Photovoltaic Module Energy Yield Measurements: Existing Approaches and Best Practice

IEA PVPS Task 13, Subtask 3 Report IEA‐PVPS T13‐11:2018 May 2018

Table of Contents

Foreword …………………………………………………………………………………… 9

Acknowledgements ……………………………………………………………………………….. 10

List of abbreviations ……………………………………………………………………………… 11

Executive Summary ………………………………………………………………. 13

1 2

3 4

Introduction ……………………………………………………………………………………… 17

Background Information ………………………………………………………… 18

  1. 2.1  Scope of Testing………………………………………………………………………………….. 18
  2. 2.2  Energy Yield versus Energy Rating …………………………………………………………. 19

International Survey on Measurement Practices ……………………………………………. 20

Test Environment and Hardware Requirements ……………………………………………….. 22

4.1 Mounting Structure & Surroundings ……………………………………………………. 22

  1. 4.1.1  Mounting rack layout ………………………………………………………………….. 23
  2. 4.1.2  PV module installation ……………………………………………………………… 24
  3. 4.1.3  PV module shading………………………………………………………………………… 24
  4. 4.1.4  Albedo ……………………………………………………………………….. 26
  5. 4.1.5  Sensor positioning ……………………………………………………….. 26

4.2 Current and Voltage Measurements ……………………………………………………. 27

  1. 4.2.1  Hardware solutions …………………………………………………….. 27
  2. 4.2.2  Hardware characteristics and configuration ………………………………….. 30
  3. 4.2.3  Recommendations …………………………………………………………….. 35

4.3 Measurement of Environmental Parameters …………………………………… 37

4.3.1 In‐plane irradiance ………………………………………………………… 37

4.3.2 Module temperature………………………………………………………… 42

4.3.3 Meteorological data ………………………………………………… 45

4.3.4 Spectral irradiance ………………………………………………………. 46

Data Quality Control and Maintenance Practice ………………………………. 50

  1. 5.1  Quality Markers ……………………………………………………………….. 50
  2. 5.2  Maintenance…………………………………………………………………… 50

Characterization of Test Modules ……………………………………………………… 52

  1. 6.1  Module Selection/Sampling………………………………………………………….. 52
  2. 6.2  Pre‐testing and Control Measurements ……………………………………… 53
  3. 7

7.1 Module Energy Yield Benchmarking ……………………………………………………. 55

  1. 7.1.1  Energy yield assessment………………………………………………………………………………. 55
  2. 7.1.2  Impact of STC power …………………………………………………………………………………… 57
  3. 7.1.3  Impact of temperature, irradiance, angle of incidence and spectrum ……………. 59
  4. 7.1.4  Calculation of derate factors ………………………………………………………………. 65
  1. 7.2  Comparison of Module Data from Different Climates……………………………………… 66
  2. 7.3  Module Performance Loss Rates (PLR) …………………………………………………………… 71
    1. 7.3.1  Methodologies …………………………………………………………………………………….. 71
    2. 7.3.2  Performance metrics …………………………………………………………………………… 72
    3. 7.3.3  Filtering and correction techniques ……………………………………………………. 73
    4. 7.3.4  Statistical techniques…………………………………………………………………………. 75

Measurement Uncertainty Analysis …………………………………………………………………………….. 79

  1. 8.1  Introduction ………………………………………………………………………………………………………. 79
  2. 8.2  Methodologies for Uncertainty Analysis ……………………………………………………………….. 80
  3. 8.3  Single Uncertainty Contributions ………………………………………………………………………….. 80
    1. 8.3.1  Uncertainty in STC power UPstc ……………………………………………………………………… 80
    2. 8.3.2  Uncertainty in irradiance Uand irradiation U………………………………………………. 81
    3. 8.3.3  Uncertainty in power UPmax ………………………………………………………………………….. 81
    4. 8.3.4  Uncertainty in key performance indicators UE, UYa and UMPR…………………………….. 82


8.4 Relative Uncertainties…………………………………………………………………………………………. 84 Summary and Conclusions …………………………………………………………………………………………. 85 Annex 1: Empty Questionnaire ………………………………………………………………………………………….. 98 Annex 2: Test Facility Sheets ……………………………………………………………………………………………… 99


The International Energy Agency (IEA), founded in November 1974, is an autonomous body within the framework of the Organization for Economic Co‐operation and Development (OECD) which car‐ ries out a comprehensive programme of energy co‐operation among its member countries. The European Union also participates in the work of the IEA. Collaboration in research, development and demonstration of new technologies has been an important part of the Agency’s Programme.

The IEA Photovoltaic Power Systems Programme (PVPS) is one of the collaborative R&D Agree‐ ments established within the IEA. Since 1993, the PVPS participants have been conducting a variety of joint projects in the application of photovoltaic conversion of solar energy into electricity.

The mission of the IEA PVPS Technology Collaboration Programme is: To enhance the international collaborative efforts which facilitate the role of photovoltaic solar energy as a cornerstone in the transition to sustainable energy systems. The underlying assumption is that the market for PV sys‐ tems is rapidly expanding to significant penetrations in grid‐connected markets in an increasing number of countries, connected to both the distribution network and the central transmission net‐ work.

This strong market expansion requires the availability of and access to reliable information on the performance and sustainability of PV systems, technical and design guidelines, planning methods, financing, etc., to be shared with the various actors. In particular, the high penetration of PV into main grids requires the development of new grid and PV inverter management strategies, greater focus on solar forecasting and storage, as well as investigations of the economic and technological impact on the whole energy system. New PV business models need to be developed, as the decentralised character of photovoltaics shifts the responsibility for energy generation more into the hands of private owners, municipalities, cities and regions.

IEA PVPS Task 13 engages in focusing the international collaboration in improving the reliability of photovoltaic systems and subsystems by collecting, analyzing and disseminating information on their technical performance and failures, providing a basis for their technical assessment, and de‐ veloping practical recommendations for improving their electrical and economic output.

The current members of the IEA PVPS Task 13 include:

Australia, Austria, Belgium, Canada, China, Denmark, Finland, France, Germany, Israel, Italy, Japan, Malaysia, Netherlands, Norway, SolarPower Europe, Spain, Sweden, Switzerland, Thailand and the United States of America.

This report focusses on the measurement of modules in the field for the purpose of energy yield or performance assessments. This document should help anyone intending to start energy yield meas‐ urements of individual PV modules to obtain a technical insight into the topic, to be able to set‐up his own test facility or to better understand how to interpret results measured by third parties.

The editors of the document are Gabi Friesen and Ulrike Jahn.

The report expresses, as nearly as possible, the international consensus of opinion of the Task 13 experts on the subject dealt with. Further information on the activities and results of the Task can be found at: http://www.iea‐

List of abbreviations

AM Air mass
AoI Angle of incidence
APE Average photon energy
DHI Diffuse horizontal irradiance
DNI Direct normal irradiance
E Energy output
ECT Equivalent cell temperature
ER Energy rating
FF Fill factor
G Irradiance
Gi In‐plane (plane of array) irradiance
Gi,d In‐plane diffuse irradiance
Gi,b In‐plane direct beam irradiance
Geff Effective irradiance or spectrally sensitive irradiance Gstc Reference irradiance at standard test conditions GHI Global horizontal irradiance
GNI Global normal irradiance
H Irradiation
IAM Incident angle modifier
Imp Current at maximum power point
Isc Short circuit current
IR Infrared
KPI Key performance indicator
LID Light induced degradation
MM Spectral mismatch factor
MPP Maximum power point
MPPT Maximum power point tracker
MPR Module performance ratio
Pnom Nominal power
Pmax Power at maximum power point


Pstc Power at standard test conditions
Pstc,stab Stabilized power at standard test conditions
PID Potential induced degradation
PLR Performance loss rate
POA Plane of array
PR Performance ratio
Rs Series resistance
Rsc Resistance at short circuit current
Roc Resistance at open circuit voltage
SIF Spectral influence factor
Tstc Reference temperature at standard test conditions Tc Cell temperature
Tamb Ambient temperature
Tmod Module temperature
TBS Back sheet temperature
ΔTCBS Difference between cell and back sheet temperature u Uncertainty
UV Ultraviolet
Vmp Voltage at maximum power point
Voc Open circuit voltage
w Wind speed
Ya PV module (array) energy yield
Yf Final yield
Yr Reference yield
Θ Tilt angle
 Recording interval
γ Pmax temperature coefficient

Executive Summary

The monitoring of single PV modules plays an important role in the demonstration and deeper un‐ derstanding of technological differences in PV module performance, lifetime and failure mecha‐ nisms.

With the growing share and relevance of PV in the market, the number of stakeholders performing outdoor measurements at module level is continuously increasing: test institutes, certification labs, PV module manufacturers, but also non‐experts in the field, e.g. distributors, investors or insurance companies are publishing their results in a wide range of media, from scientific to technical journals, from risk assessment reports to purely commercial publications. The comparability of these meas‐ urements is however made difficult by the different testing approaches and missing declarations on measurement uncertainties. This is mainly due to the fact that there is no dedicated standard or recognized guideline published, covering the specific needs of PV module energy yield measure‐ ments.

The two main reference documents available today are a best practice guideline for the testing of single modules which was presented by DERLAB (European Distributed Energy Resources Labora‐ tories) in 2012 [1] and the IEC 61724‐1 Technical Standard for the monitoring of PV systems, pub‐ lished in 2017 [2]. The first one is limited to the definition of some testing requirements, without distinguishing between different testing purposes. It does not consider uncertainty contributions at single measurement level and gives no recommendations of how to reduce them. The second one addresses many of the missing aspects, with details on sensors, equipment accuracy, quality check and performance analysis, but without considering the special requirements of single module monitoring and benchmarking studies.

Besides the slightly different scopes, the main difference between monitoring at module or system level is that system monitoring generally does not obtain the same accuracy reachable at module level. Secondary effects related to the system configuration (e.g. inverter performance, module sampling, module selection, mismatch losses, …) and spatial variations over the system (e.g. venti‐ lation, soiling, shading, …) are often hiding the technological differences which are the focus and reason for module level monitoring. Moreover, the system monitoring standard does not include any IV‐curve measurements, which are the base of many performance, lifetime and failure studies performed at module level. On the other hand, system monitoring is including some measure‐ ments, which are not relevant for module monitoring like AC currents and voltages or other system related electrical parameters.

Small systems, designed specifically for the purpose of performance or reliability studies, could however be a good alternative if all secondary uncertainties would be reduced to a minimum and the measurements of the DC side and the meteorological parameters would be good enough to allow inter‐comparisons and detailed analysis. The disadvantages of the testing of entire systems are the higher space occupation and the larger number of modules to be characterized and in‐ spected, but, on the other hand, real system stress conditions are better simulated and a more statistically relevant number of modules is measured. New hardware solutions able to measure the IV‐curves of single PV modules within a string could make this approach more attractive and afford‐ able in the near future.

The goal of this document is to fill some of the normative gaps and to help anyone intending to start energy yield measurements of individual PV modules to obtain a technical insight into the topic, to be able to set‐up his own test facility or to better understand how to interpret results measured by third parties.


The current practices for energy yield measurements of individual PV modules applied by major international research institutes and test laboratories are presented in this report. Best practice recommendations and suggestions to improve energy yield measurements are given to the reader.

A survey was conducted within the IEA PVPS Task13 consortium to assess how module energy yield measurements are performed today and how the uncertainties are calculated and reported to the end‐users. Fifteen Task members with experience in PV module monitoring from over 30 test facil‐ ities installed all over the world have been interviewed. Many ISO17025 accredited test laborato‐ ries, as well as R&D institutes, have been included. The questionnaire covered all aspects, starting from general questions on the scope of testing to the test equipment, procedures, maintenance practice, data analysis and reporting.

The purposes, for which the monitoring is performed at PV module level, can be manifold:

  •   To assess the stability of a cell technology under specific environmental conditions and stress factors (degradation studies),
  •   to measure the over or under‐performance with respect to a reference technology (benchmarking studies), understanding single environmental loss factors (temperature, spectrum, irradiance, wind, shadows, soiling, etc.) and
  •   to collect data for the validation of energy prediction models or the calibration of PV module parameters for a specific model.It is to be mentioned that module energy yield measurements are also required for the validation of the IEC 61853 standard on energy rating [3,4,5,6], which is currently in elaboration and which aims at replacing the current power rating according to standard test conditions of modules. High precision measurements with accurately determined uncertainties are the key to be able to foster the introduction of any energy rating in the future. Further, energy yield predictions as described in the Report IEA‐PVPS T13‐12:2018 entitled ‘Uncertainties in PV System Yield Predictions and Assessments’ will profit from this.Less frequently, outdoor measurements are performed for the purpose of module characterization, which is mostly done indoors with solar simulators, for which the measurement uncertainties are better defined and known. If characterization is performed under outdoor conditions, it is generally done using a sun‐tracker and other means to control the irradiance and temperature levels. In this case the integrated energy yield is not relevant and the electrical characterization is therefore not within the scope of this document.The different scopes give rise to different testing requirements and data analysis. The most relevant measured or calculated key performance indicators (KPI) are: Instantaneous power (P), energy out‐ put E, energy yield (Ya), module performance ratio (MPR) and performance loss rate (PLR). The measurement accuracy of the output data depends as much on the measurement accuracy of the single components forming the measurement system, as on the conditions at the measurement system and its configuration.This report gives an overview of the most important aspects to be considered for the set‐up of a test facility, e.g. the layout of the test rack and mounting instructions for modules and sensors, as well as how to combine and configure any current/voltage measurement system, like IV‐curve tracers and/or maximum power point trackers (MPPT) for PV modules in order to reduce any measurement artefacts ( e.g transient or capacitive effects, MPP tracking errors, wrong loading, cable losses, …) and errors in the final determination of the KPI’s due to inadeguate data recording (e.g. low sampling rates, syncronisation errors,…).Available quality control measures, such as calibration needs, quality markers for erroneous data (e.g. temperature sensor detachment, sensor soiling, data acqusition errors, …) and maintenance14

practices (visual inspection, cleaning intervals, e‐mail alert, …) are presented to increase the early detection of problems such as drifts, failures or malfunctions, which could further increase the measurement uncertainty.

The final goal is to achieve accurate and reliable data, also over a long time period, and higly comparable data, even with data from other test facilities mounted according to the same guidelines. A better understanding how to reduce single measurement uncertainties, by quantifying and documenting them, is therefore essential.

However, even by reducing all measurement uncertainties, an adequate inter‐comparison between different PV technologies is only possible if the PV modules are selected according to well‐defined sampling procedures and if the STC power and its uncertainty are known. The STC power is actually one of the main contributions to the uncertainty for the calculation of parameters Ya and MPR. The nominal power Pnom as declared by the manufacturer is generally considered as the less adequate for any inter‐comparison, because it can considerably differ from the real power of a PV module, its measurement uncertainty is rarely documented and it is subject to commercial marketing strat‐ egies. The most suitable value for benchmarking of products is the real STC power, with known uncertainty values and no variation after installation. The last aspect is important because, if the module is not stabilized before measuring the STC power, it can lead to misleading results. In gen‐ eral, the lower the measurement uncertainty and the higher the stability in the field, the higher the accuracy of the ranking is. High precision measurements and validated stabilization procedures per‐ formed by accredited test laboratories lead to highest accuracies. In general, electrical characteri‐ zation and optical inspections of PV modules before installation will guarantee that no low quality, defective or damaged modules are chosen.

To understand technological differences and the over‐ or under‐performance of one technology with respect to another under specific climatic conditions, the individual sources of loss with re‐ spect to the power under standard test conditions have to be quantified. Different approaches exist to calculate single de‐rating factors which allow to select the technology with the lowest loss at specific conditions (e.g. high fraction of diffuse light, high temperatures, high angle of incidence, etc.). To calculate the losses, either a full electrical characterization of the module under controlled laboratory conditions or the monitoring of the IV‐curves is needed.

It has to be mentioned that, in terms of bankability of the modules, the degradation rate is more important than the precise knowledge of the instantaneous performance given by the electrical module parameters. In the long term, the annual performance loss can have a higher impact on the life‐time productivity than the electrical parameters. Much less is known on the impact of the en‐ vironment on the ageing process. For this reason, many tests laboratories focus on long‐term meas‐ urement campaigns and the calculation of the PLR.

Independent of the determined KPI, deviations are only meaningful if they are higher than the measurement uncertainties. There are situations, where the magnitude of measurement uncer‐ tainty is larger than the investigated environmental effect so that the result cannot be used for benchmarking or degradation studies without taking it into account. The knowledge and reduction of the uncertainties should be mandatory for anyone performing such measurements. Sometimes, a differentiation has to be done between absolute and relative measurements.

In general, the survey performed within the PVPS Task 13 expert group highlighted that the meas‐ urement accuracy and scientific detail within most test laboratories are very high. This is demon‐ strated by a recurrent use of high precision equipment, good measurement practice and the imple‐ mentation of good quality control and maintenance practice. Nevertheless, the survey revealed some limits, which are mainly the comparability of different outdoor data and the use of these for


the validation of models due to a limited harmonization or availability of measurement uncertain‐ ties for the main KPIs. The main reason for this is that compared to the measurement of the STC performance using a solar simulator, for which the measurement uncertainties have been inten‐ sively investigated and validated over the last years, in energy yield measurements the reproduci‐ bility of test conditions is not possible and the determination of the measurement uncertainty is much more complex. The uncertainty is actually site and time dependent and impacted by many factors, which are difficult to estimate and sparely described in literature.

The first step to improve the comparability of outdoor measurements is to agree on the main un‐ certainty contributions and to suggest a common approach for the reporting of measurement un‐ certainties. This document gives recommendations on how to reduce the main uncertainty contri‐ butions and how to calculate them in future projects. Major efforts should be invested in imple‐ menting and validating best practice approaches through international round robins in future.

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Electricity Storage Valuation Framework March 2020 ISBN : 978-92-9260-161-4 Download Assessing system value and ensuring project viability – IRENA Feb 2020

Electricity storage could be a crucial factor in the world’s transition to sustainable energy systems based on renewable sources. Yet electricity markets frequently fail to account properly for the system value of storage.

This report from the International Renewable Energy Agency (IRENA) proposes a five-phase method to assess the value of storage and create viable investment conditions. IRENA’s Electricity Storage Valuation Framework (ESVF) aims to guide storage deployment for the effective integration of solar and wind power.

The three-part report examines storage valuation from different angles:

  • Part 1 outlines the ESVF process for decision makers, regulators and grid operators.
  • Part 2 describes the ESVF methodology in greater detail for experts and modellers.
  • Part 3 presents real-world cases, including examples of cost-effective storage use and maximised service revenues.

Among other findings:

  • Increasing solar and wind penetration brings new challenges for policy makers, regulators and power utilities in terms of system planning and operation.
  • Electricity storage helps to address key technical and economic challenges related to variable renewable energy (VRE) integration.
  • Storage services help to manage the variability and uncertainty that solar and wind use introduce into the power system.
  • By providing multiple services simultaneously, electricity storage permits revenue stacking for greater profitability.
  • Some storage technologies are intrinsically more suited than others for certain services. For instance, batteries provide rapid response to signals, opening the way for new, high-value system services.
  • Electricity storage could accelerate off-grid electrification, enable far higher shares of VRE, and indirectly help to decarbonise the transport sector.
  • Poor accounting for storage value results in so-called “missing money”, with market revenues too low to entice investors.
  • IRENA’s ESVF modelling methodology shows how to overcome the valuation challenge and properly assess the value of electricity storage to the power system.

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Assessment of Photovoltaic Module Failures in the Field – Study by IEA International Energy Agency


The International Energy Agency (IEA), founded in November 1974, is an autonomous body within the framework of the Organization for Economic Co-operation and Development (OECD) which car- ries out a comprehensive programme of energy co-operation among its member countries. The European Union also participates in the work of the IEA. Collaboration in research, development, and demonstration of new technologies has been an important part of the Agency’s Programme.

The IEA Photovoltaic Power Systems Programme (PVPS) is one of the collaborative R&D Agree- ments established within the IEA. Since 1993, the PVPS participants have been conducting a variety of joint projects in the application of photovoltaic conversion of solar energy into electricity.

The mission of the IEA PVPS Technology Collaboration Programme is: To enhance the international collaborative efforts which facilitate the role of photovoltaic solar energy as a cornerstone in the transition to sustainable energy systems. The underlying assumption is that the market for PV sys- tems is rapidly expanding to significant penetrations in grid-connected markets in an increasing number of countries, connected to both the distribution network and the central transmission net- work.

This strong market expansion requires the availability of and access to reliable information on the performance and sustainability of PV systems, technical and design guidelines, planning methods, financing, etc., to be shared with the various actors. In particular, the high penetration of PV into main grids requires the development of new grid and PV inverter management strategies, greater focus on solar forecasting and storage, as well as investigations of the economic and technological impact on the whole energy system. New PV business models need to be developed, as the decen- tralised character of photovoltaics shifts the responsibility for energy generation more into the hands of private owners, municipalities, cities, and regions.

IEA PVPS Task 13 engages in focusing the international collaboration in improving the reliability of photovoltaic systems and subsystems by collecting, analysing and disseminating information on their technical performance and failures, providing a basis for their technical assessment, and de- veloping practical recommendations for improving their electrical and economic output.

The current members of the IEA PVPS Task 13 include:

Australia, Austria, Belgium, China, Denmark, Finland, France, Germany, Israel, Italy, Japan, Malay- sia, Netherlands, Norway, SolarPower Europe, Spain, Sweden, Switzerland, Thailand, and the United States of America.

This report concentrates on the reliability of PV modules. The reliability of PV modules is described by theoretical models. We focus on available models and not in any case on the most important degradation mechanisms. Furthermore, statistical data of the PV module reliability in the field is presented and analysed. The importance of local environmental stressors, such as temperature, humidity, irradiance, wind, etc., influencing the reliability test methods is discussed.

The editors of the document are Marc Köntges, Institute for Solar Energy Research Hamelin, Em- merthal, Germany (DEU), Gernot Oreski, Polymer Competence Center, Leoben, Austria (AUT), and Ulrike Jahn, TÜV Rheinland Energy, Germany.

The report expresses, as much as possible, the international consensus of opinion of the Task 13 experts on the subject dealt with. Further information on the activities and results of the Task can be found at:

1 Introduction

Currently plenty of PV module failures are known. For investors these failures are difficult to assess because there is little information how much impact and how often a specific failure mode occurs in real world PV systems. The lack of information adds an unnecessary uncertainty to the risk of investment. In this document we try to analyse this problem from three perspectives.

The first perspective is the view of a scientist, PV module expert or manufacturer. In chapter 2 we summarize PV module failure models. These models allow one to analyse the impact of specific well-known degradation modes and failures on the module power with a dependence on weather conditions. These models allow a manufacturer or a PV module expert to evaluate the power loss risk for specific known failures for a specific product. This information can be used to define the warranty criteria for the product. However, most of the failures have not been evaluated to this depth in literature. For these failures, data is summarized from the literature to explain the root cause mechanisms and, if possible, ways to simulate their impact on power production in the fu- ture. A framework is explained to model the power loss of multiple failures.

The second perspective is the view of an investor, banker or underwriter. We collect PV system failure data for four climate zones. These data allow analysing the occurrence of a failure relative to other failure types and its impact on the system power.

Finally, the third perspective is the view of a test institute and PV system planner. Here we explain how one has to modify testing methods for specific failure types to special regions. This allows adapting test methods for a given PV module to specific regional requirements.


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Solar Bankability – Mitigating Technical Risks in PV Investment through Quality Infrastructure

  • Solar bankability: active quality management process where all stakeholders in PV project approval process attempt to identify, manage and control potential risks (technical, legal & economical) through entire project lifecycle

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Operation & Maintenance – Best Practice Guidelines / Version 4.0 – Dec 2019


Welcome to Version 4.0 of SolarPower Europe’s Operation & Maintenance (O&M) Best Practice Guidelines. This new version produced by SolarPower Europe’s O&M and Asset Management Task Force, led by BayWa r.e., has achieved a very high level of maturity and is now well established as a reference in the solar sector. It builds on the previous versions, led by First Solar and subsequently Alectris, and has been further fine-tuned and upgraded with the help of leading experts that joined our Task Force in 2019.

O&M is a segment of great importance for the solar industry in Europe and worldwide. It is the segment that creates the most jobs and economic value in Europe, and drives important solar innovations globally notably in the field of digitalisation and data processing. The first version of these Guidelines was published in 2016 to address service quality issues in solar O&M and by 2019, the guidelines have become a living document powered by an active community of experts.

The Version 4.0 provides updates which are considered important to keep pace with the fast development of the industry. We thank our members, as well as partners including the Solar Trade Association (STA) and the National Renewable Energy Laboratory (NREL), for the thorough review. For example, in the chapter on Data and Monitoring requirements updates were incorporated to reflect state-of-the-art communication technology and cybersecurity requirements. We also included an overview of existing international standards in the field of solar O&M, and new innovative field inspection techniques such as fluorescence imaging and magnetic field imaging. In the Key Performance Indicators (KPIs) chapter, we added an explanatory section on how to interpret Performance Ratio and included new KPIs such as Trackers Availability and Schedule Attainment. We have updated the Contractual Framework chapter according to the Open Solar Contracts, which were published by IRENA and the Terrawatt Initiative in June 2019. We have also aligned the chapter on Technical Asset Management with our new Asset Management Best Practice Guidelines. Last but not least, we improved the user-friendliness of the report by adding new figures and streamlining the document’s structure.

In terms of spin-off activities, 2019 was a very rich year. Most importantly, we completed our well-established O&M Guidelines with the development of Asset Management Best Practice Guidelines, a new report looking at the commercial and financial management of solar investments. The Asset Management Best Practice Guidelines address the professionalisation of solar investors and the globalisation of solar investment portfolios, which lead to rapidly rising service quality expectations that put increasing requirements on solar asset managers. As part of our efforts to disseminate the best practices in Europe and beyond,after publishing a Spanish-language Mexican edition in cooperation with ASOLMEX and the German development cooperation GIZ in 2018, this year, we translated the O&M Best Practice Guidelines into German. We are also working on a French translation for the Tunisian market and an adaptation for the Indian market in cooperation with the German development cooperation GIZ and the National Solar Industry Federation of India (NSEFI). Moreover, we have launched, a platform which collects all our reports and tools for quality solar service provision, including the Best Practice Guidelines in all available languages and self-evaluation checklists for O&M contractors, monitoring tool providers and aerial thermography providers. Theplatform also features a directory of companies that comply with the best practices.

We thank our members for their extraordinary level of engagement, which reflects the importance of O&M and Asset Management for our sector. We will continue the work in 2020 and invite interested stakeholders to join our Task Force activities and help us improve even further our contribution to even more performant solar O&M services.


Operation and Maintenance (O&M) has become a standalone segment within the solar industry and it is widely acknowledged by all stakeholders that high-quality O&M services mitigate potential risks, improve the Levelised Cost of Electricity (LCOE) and Power Purchase Agreement (PPA) prices, and positively impact the return on investment (ROI). Responding to the discrepancies that exist in today’s solar O&M market, the SolarPower Europe O&M Best Practice Guidelines make it possible for all to benefit from the experience of leading experts in the sector and increase the level of quality and consistency in O&M. These Guidelines are meant for O&M contractors as well as investors, financiers, asset owners, asset managers, monitoring tool providers, technical consultants and all interested stakeholders in Europe and beyond.

This document begins by contextualising O&M, explaining the roles and responsibilities of various stakeholders such as the Asset Manager, the Operations service provider and the Maintenance provider and by presenting an overview of technical and contractual terms to achieve a common understanding of the subject. It then walks the reader through the different components of O&M, classifying requirements into “minimum requirements”, “best practices” and “recommendations”.

Environment, Health & Safety

Environmental problems are normally avoidable through proper plant design and maintenance, but where issues do occur, the O&M contractor must detect them and respond promptly. Environmental compliance may be triggered by components of the PV system itself, such as components that include hazardous materials and by-products that may be used by the O&M contractor such as herbicides and insecticides.

In many situations, solar plants offer an opportunity to provide for agriculture and are a valuable natural habitat for plants and animals alongside the primary purpose of power production. Solar plants are electricity generating power stations and have significant hazards present which can result in injury or death. Risks should be reduced through proper hazard identification, careful planning of works, briefing of procedures to be followed, documented and regular inspection, and maintenance. Personnel training and certification and personal protective equipment are required for several tasks. Almost all jobs have some safety requirements such as fall protection for work at heights and electrical arc-flash, lock-out tag-out, and general electrical safety for electrical work; eye and ear protection for ground maintenance.

Personne& training

It is important that all O&M personnel have the relevant experience and qualifications to perform the work in a safe, responsible and accountablemanner. These Guidelines contain a skills’ matrix template that helps to record skills and identify gaps.

TechnicaAsset Management

Technical Asset Management (TAM) encompasses support activities to ensure the best operation of a solar power plant or a portfolio, i.e. to maximise energy production, minimise downtime and reduce costs. In many cases, the O&M contractor assumes some technical Asset Management tasks such as planning and reporting on Key Performance Indicators (KPIs) to the asset owner. However, in cases where the technical asset manager and the O&M contractor are separate entities, close coordination and information sharing between the two entities is indispensable. Technical Asset Management also includes ensuring that the operation of the PV plant complies with national and local regulations and contracts, and also advising the asset owner on technical asset optimisation via e.g. repowering investments. For more information about Asset Management, please refer to SolarPower Europe’s Asset Management Best Practice Guidelines, which can be downloaded from

Power Plant Operation

Operation is about remote monitoring, supervision and control of the PV power plant and it is an increasingly active exercise as grid operators require more and more flexibility from solar power plants. Power plant operation also involves liaising with or coordination of the maintenance team. A proper PV plant documentation management system is crucial for Operations. A list of documents that should be included in the as-built documentation set accompanying the solar PV plant (such as PV modules’ datasheets), as well as a list of examples of input records that should beincluded in the record control (such as alarms descriptions), can be found in the Annex of these Guidelines. Based on the data and analyses gainedthrough monitoring and supervision, the O&M contractor should always strive to improve PV power plant performance. As there are strict legal requirements for security services in most countries, PV power plant security should be ensured by specialised security service providers.

Power Plant Maintenance

Maintenance is usually carried out on-site by specialised technicians or subcontractors, according to the Operations team’s analyses. A core element of maintenance services, Preventive Maintenance involves regular visual and physical inspections, functional testing and measurements, as well as the verification activities necessary to comply with the operating manuals and warranty requirements. The Annual Maintenance Plan (see an example in Annex B) includes a list of inspections and actions that should be performed regularly. Corrective Maintenance covers activities aimed at restoring a faulty PV plant, equipment or component to a status where it can perform the required function. Extraordinary Maintenance actions, usually not covered by the O&M fixed fee, can be necessary after major unpredictable events in the plant site that require substantial repairworks. Additional maintenance services may include tasks such as module cleaning and vegetation control, which could be done by the O&M contractor or outsourced to specialist providers.

Revamping and repowering

Revamping and repowering are usually considered a part of extraordinary maintenance from a contractual point of view – however, due to their increasing significance in the solar O&M market, these Guidelines address them in a standalone chapter. Revamping and repowering are defined as the replacement of old, power production related components within a power plant by new components to enhance the overall performance of the installation. This chapter presents the best practices in module and inverter revamping and repowering and general, commercial considerations to keep in mind before implementation.

Spare Parts Management

Spare Parts Management is an inherent and substantial part of O&M aimed at ensuring that spare parts are available in a timely manner for Preventive and Corrective Maintenance in order to minimise the downtime of a solar PV plant. As a best practice, the spare parts should be owned by the asset owner while normally maintenance, storage and replenishment should be the responsibility of the O&M contractor. It is considered a best practice not to include the cost of replenishment of spare parts in the O&M fixed fee. However, if the asset owner requires the O&M contractor to bear replenishment costs, the more cost-effective approach is to agree which are “Included Spare Parts” and which are “Excluded Spare Parts”. These Guidelines also include a minimum list of spare parts that are considered essential.

Data and monitoring requirements

The purpose of the monitoring system is to allow supervision of the performance of a PV power plant. Requirements for effective monitoring include dataloggers capable of collecting data (such as energy generated, irradiance, module temperature, etc.) of all relevant components (such as inverters, energy meters, pyranometers, temperature sensors) and storing at least one month of data with a recording granularity of up to 15 minutes, as well as a reliable Monitoring Portal (interface) for the visualisation of the collected data and the calculation of KPIs. Monitoring is increasingly employing satellite data as a source of solar resource data to be used as a comparison reference for on-site pyranometers. As a best practice, the monitoring system should ensure open data accessibility in order to enable an easy transition between monitoring platforms and interoperability of different applications. As remotely monitored and controlled systems, PV plants are exposedto cybersecurity risks. It is therefore vital that installations undertake a cyber security analysis and implement a cybersecurity management system. To evaluate monitoring tools it is recommended to refer to the Monitoring Checklist of the Solar Best Practices Mark, which is available at

Key Performance Indicators

Important KPIs include PV power plant KPIs, directly reflecting the performance of the PV power plant; O&M contractor KPIs, assessing the performance of the O&M service provided, and PV power plant/O&M contractor KPIs, which reflect power plant performance and O&M service quality at the same time. PV power plant KPIs include important indicators such as the Performance Ratio (PR), which is the energy generated divided by the energy obtainable under ideal conditions expressed as a percentage, and Uptime (or Technical Availability) which are parameters that represent, as a percentage, the time during which the plant operates over the total possible time it is able to operate. O&M contractor KPIsinclude Acknowledgement Time (the time between the alarm and the acknowledgement), Intervention Time (the time between acknowledgement and reaching the plant by a technician) and Resolution Time (the time to resolve the fault starting from the moment of reaching the PV plant). Acknowledgement Time plus Intervention Time are called Response Time, an indicator used for contractual guarantees. The most important KPI which reflects PV power plant performance and O&M service quality at the same time is the Contractual Availability. While Uptime (or Technical Availability) reflects all downtimes regardless of the cause, Contractual Availability involves certain exclusion factors to account for downtimes not attributable to the O&M Contractor (such as force majeure), a difference important for contractual purposes.

Contractual framework

Although some O&M contractors still provide Performance Ratio guarantees in some cases, it is a best practice to only use Availability and Response Time guarantees, which has several advantages. A best practice is a minimum guaranteed Availability of 98% over a year, with Contractual Availability guarantees translated into Bonus Schemes and Liquidated Damages. When setting Response Time guarantees, it is recommended to differentiate between hours and periods with high and low irradiance levels as well as fault classes, i.e. the (potential) power loss. As a best practice, we recommend using the O&M template contract developed as part of the Open Solar Contracts, a joint initiative of the Terrawatt Initiative and the International Renewable Energy Agency (IRENA). The Open Solar Contracts are available at

Innovations and trends

O&M contractors are increasingly relying on innovations and more machine and data-driven solutions to keep up with market requirements. The most important trends and innovations shaping today’s O&M market are summarised in this chapter, grouped into three “families”: (1) Smart PV power plant monitoring and data-driven O&M, (2) Retrofit coatings for PV modules, and (3) O&M for PV power plants with storage.

O&M for distributed solar

All best practices mentioned in these Guidelines could be theoretically applied to even the smallest solar system for its benefit. However, this is not practical in nature due to a different set of stakeholders and financial implications. This chapter assists in the application of the utility-scale best practices to distributed solar projects, which are shaped by three important factors: (1) a different set of stakeholders – owners of distributedsystems not being solar professionals but home owners and businesses, (2) different economics – monitoring hardware and site inspections accounting for a larger share of investment and savings, and (3) a higher incidence of uncertainty – greater shade, lower data accuracy and less visual inspection.

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An overview of solar photovoltaic panels’ end-of-life material recycling – 2020


End-of-life (EOL) solar panels may become a source of hazardous waste although there are enormous benefits globally from the growth in solar power generation. Global installed PV capacity reached around 400 GW at the end of 2017 and is expected to rise further to 4500 GW by 2050. Considering an average panel lifetime of 25 years, the worldwide solar PV waste is anticipated to reach between 4%-14% of total generation capacity by 2030 and rise to over 80% (around 78 million tonnes) by 2050. Therefore, the disposal of PV panels will become a pertinent environmental issue in the next decades. Eventually, there will be great scopes to carefully investigate on the disposal and recycling of PV panels EOL. The EU has pioneered PV electronic waste regulations including PV-specific collection, recovery and recycling targets. The EU Waste of Electrical and Electronic Equipment (WEEE) Directive entails all producers supplying PV panels to the EU market to finance the costs of collecting and recycling EOL PV panels in Europe. Lessons can be learned from the involvement of the EU in forming its regulatory framework to assist other countries develop locally apposite approaches. This review focused on the current status of solar panel waste recycling, recycling technology, environmental protection, waste management, recycling policies and the economic aspects of recycling. It also provided recommendations for future improvements in technology and policy making. At present, PV recycling management in many countries envisages to extend the duties of the manufacturers of PV materials to encompass their eventual disposal or reuse. However, further improvements in the economic viability, practicality, high recovery rate and environmental performance of the PV industry with respect to recycling its products are indispensable.

Photovoltaic technologySolar panelsRecyclingWaste generationEnd-of-lifec-SiThin film

1. Introduction

Solar photovoltaic (PV) energy technologies, which were first applied in space, can now be used ubiquitously where electricity is required. Photovoltaic (PV) energy production is one of the most promising and mature technologies for renewable energy production. PV technology is environmentally friendly and has become a popular means of generating power. Solar energy technology is currently the third most used renewable energy source in the world after hydro and wind power, which occupy the first and second position, respectively [1]. Moreover, PV energy sources generate power with low levels of carbon emissions that cause global warming [2]. In addition, fossil fuel-generated electricity accounts for CO2emissions of between 400 g and 1000 g CO2 eq/kWh, whereas CO2 emission from silicon-based solar panels are negligible [3].

Solar power is safe, efficient, non-polluting and reliable. Therefore, PV technology has a very exciting prospect as a way of fulfilling the world’s future energy needs. During the past several decades, the utilization of solar PV power has increased. There is now a large market for PV panels which have the potential to globally produce clean energy. Moreover, it is expected that within the current century, PV-generated electricity will become the primary global energy source [4]. The year 2017 was especially notable for solar PV sector, with the level of solar PV generation capacity globally installed, rivalling other energy production technologies [5]. In fact, solar power has added more new capacities than both nuclear and fossil fuel energy-generation capacity as shown in Fig. 1. The installed capacity of solar and wind power technology has almost doubled, with an additional of 99.1 GWh of solar PV energy that became grid-connected in 2017 [5].

Fig. 1

Large-area solar PV installations help to reduce production costs. Saudi Arabia put out tenders for a 300 MW plant in February 2018, which would produce solar energy at the world’s lowest price of 0.0234 USD/kWh [6]. Solar energy prices have rapidly reduced because of developments in solar technologies. China led the world in solar power production in 2017 and installed 50% of the world’s new solar power generation capacity [5]. On the other hand, in the same year, Europe had a slower rate of increase in its solar generation capacity, which grew by only 30% as compared to the previous year [5]. Nevertheless, by the end of 2022, global solar energy generation capacity may grow to as much as 1270.5 GW and solar generated power will therefore exceed 1 TW (TWh) [6].

However, with the increase in installations, the number of solar panels reaching their EOL stage will rise steadily [3]. Solar panels will become a form of hazardous waste when the useful life is over and may harm the environment if they are not recovered or disposed of properly. The recycling of waste panels was not a concern during the first 25 years of development [4]. However, a sound management of solar panels EOL is gradually becoming an important environmental issue. Therefore, an appropriate recycling of PV waste will become gradually more significant, considering the growing number of installations and extension of production [8,18]. The utilization of valuable resources and the potential for waste generation at the EOL cycle of PV technologies has imposed a proper planning for a PV recycling infrastructure [4]. To certify the sustainability of PV in large scales of deployment, it is crucial to establish low-cost recycling technologies for the evolving PV industry in parallel with the swift commercialization of these new technologies.

Recently, the European Union (EU) has included PV waste into the new Waste of Electrical and Electronic Equipment (WEEE) directive to limit the negative influence of the persistent growth in PV waste volume and to implement solar module recycling [18]. This directive (2012/19/EU) is now applicable to the management of waste solar panels, both household and industrial in Europe [4,7,8]. The natural resources used in manufacturing solar PV panels qualify as auxiliary raw materials within the applicable regulations [9]. However, PV waste must be properly disposed and treated. In Europe, the export of waste is prohibited. Quite apart from the economic, environmental and social implications of this prohibition, it promotes the recycling of solar PV components [1]. Besides, in line with the EU policy on the treatment of waste, it gives priority to the recovery and recycling of materials.

Therefore, solar PV panel EOL management is an evolving field that requires further research and development. The key aim of this study is to highlight an updated review of the waste generation of solar panels and a sketch of the present status of recovery efforts, policies on solar panel EOL management and recycling. The review also anticipates the base of solar panel recycling recommending future directions for public policymakers.

2. Overview on large-scale PV installations

There are various types of solar PV cells, whereby the c-Si solar cell dominates 80% of the market globally [1,7,8]. Thin film solar cells are second generation, semiconductor-controlled solar cells made from materials such as cadmium telluride (CdTe), and copper indium gallium (di) selenide (CIGS). In 2017, the total newly installed capacity was 99.1 GW globally, which was approximately the same as the total installed capacity up until the end of 2012 (100.9 GW) [5]. By the end of 2017, the total installed capacity exceeded 400 GW, with the capacity in 2015–2016 rising from around 200 GW–300 GW [5]. The cumulative installed solar power capacity increased by 32% between 2016 and 2017 from 206.5 GW to 404.5 GW, as shown in Fig. 2. In 2007, Germany was the first country to sanction the commercial connection of solar power to their national grid commencing a tariff scheme [6]. In 2007, the installed global capacity was 9.2 GW. At the end of 2017, the cumulative installed capacity increased by around 43% [6].

Fig. 2

In 2017, the Asia-Pacific region became the leading area for solar power having increased its capacity by 73.7 GW to reach a total installed capacity of 221.3 GW [5,6]. It represented a 55% share of the global capacity as visible in Fig. 3 [6]. Meanwhile the European nations were the solar power pioneers and still together occupy second position in the world’s capacity ranking based on a cumulative PV capacity of 114 GW, while their share has slipped to 28%. The United States of America are in third position with a total installed capacity of 59.2 GW, or around 15% [5]. The share of Africa and the Middle East was reduced in 2017. Even after adding 2.1 GW, the total solar capacity of 6.9 GW represented only 1.7% of the global capacity [5]. Almost one third (32.3%) of the world’s solar power generation capacity was operated by China based on a substantial increase from 2016 [11]. China for the first time became the world’s largest solar power generating nation in 2017, having increased its share from around 25% in the previous year, followed by Japan and USA. In 2017, USA overtook Japan although the share of the total world capacity of both countries were reduced [7].

Fig. 3

Based on their share of worldwide capacity, Japan’s 49.3 GW was reduced to 12.2% in 2017, as compared to 13.8% in 2016 [6]. None of the European individual nations was among the top three solar power generating nations. Only Germany had the fourth largest capacity achieving a double-digit global share, due to a low new-installation of 1.8 GW in 2017, which resulted in a drop-in global share to 10.6% from 13.4% in 2016 [6]. Further, for the first time in 2017, India was among the top five countries, having added more than 10 GW of solar generation capacity to increase its share of global installed capacity by 4.7%, and doubling its total PV capacity in 2017 to 19 GW [5]. At the end of 2017, the United Kingdom and Italy were the only other two countries with more than 10 GW of installed solar capacity, with Italy at 19.4 GW and the United Kingdom at 12.7 GW [11]. Based on the current estimates, it is unlikely in 2018, that any other countries will increase their installed capacities to 10 GW with Australia (7.3 GW), France (8 GW) and Spain (5.6 GW) some way below that level in 2017 [6].

3. Global photovoltaic market and waste generation

The market share of solar panels by technology group is shown in Fig. 4. Currently, the volume of comprehensive connected PV panels is rising sharply. Rapid growth is anticipated in the coming years with the typical useful life of a solar panel of 25 years [1,12]. However, it is expected that the total quantity of PV panels EOL will reach 9.57 million tonnes by 2050 [4]. In 2014, the market was dominated by silicon-based c-Si panels, which accounted for a 92% share of the market with those based on CdTe technology at 5%, copper indium gallium (di) selenide (CIGS) at 2%, with 1% accounted for by those manufactured from other materials (dye-sensitized, CPV, organic hybrids) [4,14,15]. The market share of c-Si PV panels is projected to decrease from 92% to 44.8% between 2014 and 2030 [13,14]. The third-generation PV panels are predicted to reach 44.1%, from a base of 1% in 2014, over the same period [4,[13][14][15]].

Fig. 4

Solar PV panels will probably lose efficiency over time, whereby the operational life is 20–30 years at least [7,13,16]. The International Renewable Energy Agency (IRENA) estimated that at the end of 2016, there were around 250,000 metric tonnes of solar panel waste globally [12]. The solar panels contain lead (Pb), cadmium (Cd) and many other harmful chemicals that could not be removed if the entire panel is cracked [[17][18][19]]. In November 2016, the Environment Minister of Japan advised that Japan’s production of solar panel waste per year is expected to rise from 10,000 to 800,000 tonnes by 2040 and the country has no plans to dispose of them safely and effectively [17,20]. A recent statement found that the Toshiba Environmental Solutions will take approximately 19 years for reprocessing all solar massive waste of Japan produced by 2020 [21]. The yearly waste will be 70–80 times higher by 2034 than the year before 2020 [21]. China with a larger number of solar plants, currently operates around two times as many solar panels as USA and has no proposals for the dumping of the whole old panels. Despite the presence of environmental awareness, California, another world leader in solar panels, also has no waste disposal plan. At the end of their useful lives, only Europe requires the manufactures of solar panels to collect and dump solar waste. Although solar panels were disposed of on regular sites, it is not advisable because the modules can degrade, and harmful chemicals can leach into the ground causing drinking water contamination [22].

The lifetime of PV modules has been estimated for 25 years. Therefore, it can be assumed that the installed PV power (MW) becomes waste after that period. To identify the time shifting, the years of installation and the years of waste generation may be denoted as x and y, respectively where y = x+25 [1].

Currently, two types of PV recycling technology are commercially available but other technologies are also under research. Panels manufactured by using c-Si technology occupy the major market share with thin film technology by using either CdTe or CIGS technology as the second largest market sector [13,19,23]. The recycling processes for c-Si PV panels are different from those applied to thin film PV panels because of their different module structures [5]. One important distinction is that the aim of disposing of the encapsulant from the layered structure of compound PV modules is to recover the quilted glass and the substrate glass that contain the semiconductor layer [19,23]. Therefore, the purpose for recycling c-Si modules is to divide the c-Si glass and to recover the Si cells and other metals. The method incorporated in recycling Si-based PV panels is to separate the layers, which necessitates removing the encapsulant from the panel and the Si cells to recover the metals [23]. The removal of the encapsulant from the laminated structure is not straightforward and many possible approaches exist, including thermal, mechanical, and chemical process. Chemical methods recapture metals from Si cells, for instance, by etching and other processes. The substrate glass and the metals in the semiconductors are separated, recovered and can be isolated and purified [5,13].

Most of the waste is typically generated during four primary life cycle phases of any given PV panel. These are 1) panel production 2) panel transportation 3) panel installation and use, and 4) EOL disposal of the panel [13]. The following waste forecast model covers all life cycle stages except for production. This is because it is assumed that production waste is easily managed, collected and treated by waste treatment contractors or manufacturers themselves and thus not a societal waste management issue.

3.1. Causes of solar PV panel failure

There are relatively few defects found in new solar panels, with light erosion (0.5%–5%), with poor design and defects arising during manufacture being the main causes [13,19,22]. From Fig. 5, other causes of panel failure have been claimed to be due to electrical equipment, such as junction boxes, fuse boxes, charge controllers and cabling as well as issues with grounding [24,25]. In the early years of production, solar panels suffered from degradation of the anti-reflective coating layer of colourless ethylene vinyl acetate (EVA) applied onto the glass, as well as incoherency due to cracked solar cells [26]. During the first 12 years of use, failures were caused by repeated load cycles due to, for instance to wind or snow, as well as temperature changes which caused degradation, contact defects in junction boxes, glass breakage, burst frames, breakage of cell interconnections and problems with the diodes associated with a higher rate of cell degradations and interconnectors [13,21]. Previous research has shown that 40% of PV panel failures were due to microscopic cracks and failures [21]. This reason has been the most common in newer panels manufactured after 2008 when the production of thin cell panels began [13,21].

Fig. 5

4. Existing methods of the recycling process

4.1. Recycling process

Nowadays, Japan, Europe and the US are focused on research and development related to solar module recycling [[28][29][30][31][32]]. Most efforts related to solar panel recycling concentrate on Si panels and aim to recover and recycle the most important parts. As stated above, there are presently three different types of recycling process applied to solar PV panels which are physical, thermal and chemical as illustrated in Fig. 6 [4].

Fig. 6

4.2. Physical separation

In this process, panels are primarily dismantled by removing the surrounded Al frame, as well as the junction-boxes and embedded cables [25,26]. The single part of the PV modules (panel, junction-box and cables) are shredded and crushed to inspect the individual toxicity of each part and total toxicity of the module for disposal [25]. Frame is the last component to be attached to the module. It serves as a bonding component, isolates the module edges from the exterior (to avoid water infiltration, for instance) and provides a mechanical strength while keeping the overall structure light [23,35,36]. After the frame component is separated from the module, it can be recovered through a secondary metallurgy. Other elements present in small quantities (iron, silicon, and nickel) are typical components of aluminium alloys [23,35].

The replacement of elements in solar cells to repair systems is confined to replace electrical components and does not include material separation or cell treatment [37,38]. There are two widely used types of process to check for and repair the junction box faults. By repairing the junction box faults, it can help to increase the output power of the older solar panels. However, this method can only be used for external junction boxes located outside the main body of the solar panel.

4.3. Thermal and chemical treatment

Fiandra et al. [8] applied thermal treatment to recover the polycrystalline silicon by using a high temperature Lenton tubular furnace. Samples were taken from the PV module by manual dismasting of the external Al frame. Each sample was obtained by cutting a piece of about 10 × 10 cm by using a diamond blade for glass cutting, followed by panel cutting. The gas supply flow rates for the furnace were managed by two flow meters to get nitrogen/oxygen mixtures at different ratios. The gas was supplied at a flow rate of 24 L/h. Then the reactor was heated up to the process temperature (500 °C) at a heating rate of 450  °C/h and the temperature was finally held for 1 h [18].

Pagnanelli et al. [39] used mechanical crushing to reduce the glass to >1 mm and further crushing was done to recover different grades of the glass fraction, all of which were <1 mm. Thermal treatment, with an air flux of 30 L/h was then applied to recover the glass and metal fractions. The heating rate was gradually increased until it reached 650 °C at a rate of 10  °C/min. The furnace was then maintained at that temperature for 1 h. An overall glass recovery rate of 91% was achieved by this means.

Meanwhile, Orac et al. [38] used thermal pretreatment followed by acid leaching to recover copper and tin from the used circuit boards.

Shin et al. [3] recycled 60 multi-crystalline Si wafers (156 mm × 156 mm) which was manufactured in South Korea by JSPV Co. Ltd. Thermal treatment was first applied to separate the layers of the solar panels [33,40] as shown in Fig. 7. The thermal treatment was conducted in a K-Tech. Co (South Korea) furnace (1500 mm wide x 1700 mm high x 2000 mm long). The wafers were first coated with a phosphoric acid paste and then heated for 2 min at five temperatures ranging from 320 °C to 400 °C. The resulting recovered wafers were successfully used in manufacturing solar panels and the efficiency of the cells was found to be similar to that of the original product.

Fig. 7

Doi et al. [31] applied various organic solvents to crystalline-silicon solar panels to remove the EVA layer, which was found to be melted by diverse types of organic solvents, of which trichloroethylene was found to be the most effective. The solar panels (125 mm × 125 mm) were treated in a process by using mechanical pressure, which was essential to suppress the swelling of EVA during soaking in trichloroethylene for 10 days at 80 °C. The reclaimed Si panels could be used efficiently after the recycling process.

Kim and Lee [41] reported on enhancing the rate of EVA layer dissolution by using different types of organic solvents (trichloroethylene, O-dichlorobenzene, benzene, and toluene) aided by an ultrasonic process. The research tested different solvent combinations, temperatures, ultrasonic power and radiation times. After 1 h, the EVA layer was fully dissolved in 3 mol/L of toluene at a temperature of 70 °C with exposure to ultrasound at a power of 450 W. However, a problem was noted with this process in which lead was resulted as a hazardous by-product.

Marwede et al. [42] reviewed the available means of treating EOL PV materials and noted that the pH value changed during three periods when sodium hydroxide was used for metal recovery [43,44]. In other research works, 5 N Plus recovered metals by evaporation in a thickening tank and the metals were recovered by filtering during dewatering.

First Solar announced 95%–97% recovery rate for both Cd and Te which were capable of being reused in First Solar products [46,47].

Wang and Fthenakis [48] conducted Cd and Te separation by using various ion-exchange resins on the metals in a sulphuric acid solution over different time periods [[49][50][51]]. The recovered metals were eluted from their ion-exchange/acid solutions, and a high recovery rate of above 90% was recorded. In another study, the recovery of Te from solution was noted to be accelerated by the use of sodium carbonate and sodium sulphide.

Dattilo [52] reported the wet-chemical extraction of metals from CIGS panels. The method dependent on desalinizing of composites, recovering the Cu and separating other metals such as In and Ga. CIGS materials were directly decomposed by electrolysis with the Cu and Se settling on the cathode plate, which were then removed and separated by oxidization and distillation to produce Cu, Se with ZnO and InO being compounded by exhalation.

Table 1 and Table 2 summarizes the currently available solar panel recycling technologies. While many of these methods have been the subject of laboratory-based research, there are currently only two commercially available treatments. The US-based solar manufacturer First Solar applies both mechanical and chemical treatment methods to thin film solar panels. On the other hand, c-Si solar-panel modules have been recycled by a company in Germany [6,61]. China has limited facilities for recycling involving component repair and panel separation and hires an external technology to conduct the separation and recycling of individual materials. Similarly, other countries have problems in applying recycling technologies. Physical or mechanical processes generate a huge amount of dust which contains glass. Therefore, it is toxic, and the processes are also a source of noise pollution. The separation of the EVA layer by inorganic solvents leads to nitrogen oxide emissions and other harmful gases [56], and their inhalation constitutes a health risk. In addition, the process of reusing the silicon wafers involves frame removal and it is difficult to dispose of the remaining liquid. Furthermore, the time required for EVA dissolution by familiar organic solvents is long, but it can be accelerated by using ultrasound. However, the process also produces a very large amount of organic-melted waste, which is difficult to treat. The thermal and chemical methods are therefore a combined and advanced technology but with the disadvantage that they produce toxic gases and consume high amounts of energy.

Table 1. Silicon solar module recycling processes.

DelaminationPhysical disintegration➢Efficient waste handling➢Other materials mix with EVA.➢Solar cells damage.➢Apparatus decomposition.[3,53,54]
Thinner dissolution (Organic Chemistry)➢Organic layer removal from glass➢Waste chemical reuse➢Simple removal of EVA➢Time necessary for delamination depends on area.➢Expensive equipment.➢Hazardous for human health.[31,55]
Nitric acid dissolution➢Complete removal of EVA and metal layer from the wafer➢Possible recovery of the whole cell➢Dangerous emissions.➢Cell defects due to inorganic acid.[56]
Thermal treatment➢EVA fully eliminated.➢By reusing wafers, possible to regain whole cell➢Involves high energy consumption.➢Dangerous emissions[47,57,58]
Ultrasonic irradiation➢Used as a supplementary process to accelerate dissolution process➢Simplified removal of EVA.➢Very costly process.➢Waste solution treatment.[41]
Material SeparationDry and wet mechanical process➢Non-chemical process.➢Simple process.➢Requires low energy.➢Equipment available.➢No removal of dissolved solids[45]
Etching➢Simple and effective process.➢Recovery of high purity materials➢High energy demand because of high temperatures.➢Use of chemical.[59]

Table 2. Thin film solar module recycling methods.

DelaminationPhysical disintegration➢Feasible to obtain various wastes by treatment (Split modules, submodules and laminated modules).➢Mixing of the various material fractions.➢Loss from each material fraction.➢Glass still partly combined with the EVA.➢Breakage of solar cells.[3,53,54]
Thinner dissolution (Organic Chemistry)➢Organic layer removed from glass.➢Reprocessing solutions.➢Simple removal of EVA.➢Time necessary for delamination depends on area.➢Cannot be dissolved fully and EVA still adheres to glass surface.[31,54]
Thermal treatment➢Complete elimination of EVA.➢Possible to recover whole cell by reusing wafers.➢High energy consumption.➢Hazardous emissions.[32,41,42]
Radiotherapy➢Easy to eliminate EVA➢Slow procedure➢Very expensive process.[34,47]
Material SeparationErosion➢No chemicals required➢Glass can be recovered➢Additional treatment of pre-purification is necessary[60]
Vacuum blasting➢Removal of semiconductor layer without chemical dissolution.➢Glass can be recovered➢Emission of metallic fractions➢Relatively long processing time.[42,61]
Dry and wet mechanical process.➢Non-chemical process.➢Simple procedure.➢Needs low energy.➢Apparatus usually available.➢No removal of dissolved solids[45]
Tenside chemistry➢Tensides are reusable.➢Metals fully removed from glass.➢Emulsions must be adapted to different cell technologies➢Delamination time depends on the area.[49,51]
Leaching➢Complete elimination of metal from glass.➢Further extraction of metal solutions possible.➢Very high use of chemicals.➢Complicated control of the chemical reactions.[49,62]
Flotation➢Comparatively easy method.➢Limited use of chemicals➢Material separated at various stages of flotation➢Inadequate purity of materials.[54,60]
Etching➢Recovery of high purity materials.➢Low cost and effective process➢High energy demand because of high temperatures.➢Chemical usage.[59]
Material purificationHydrometallurgical➢Commercially applicable.➢Low and controllable emissions➢Easy water management➢Many separation and absorption steps.➢Chemical process steps must be adapted to respective technology.[47,49,60]
Pyrometallurgical➢Established industrial process.➢Feedstock can contain different materials➢High throughput necessary.➢Some materials are lost in slag.➢Heavy metals or unwanted materials[47,49,55,60]

5. Recycling approaches

Within the European Union, the first country to adopt the EU’s WEEE directive that relate to the disposal and recycling of solar PV materials was the UK [63]. Then, the second EU country to ratify the directive was Germany, which now also follows the WEEE regulations [64]. Under the directive, all producers or importers of solar PV materials, including solar panels, have to register under a product consent scheme in which all data about the panels must be provided by the manufacturers [63,65]. In addition, the producers and importers have to accept responsibility for the EOL treatment of their products or they are subjected to large fines. Moreover, the European Union and the Czech Republic have entered into a joint venture for the recycling and recovery of solar PV panels EOL, following the WEEE directive [65]. Worldwide, the recycling of PV products requires producers to employ waste management techniques or employ the service of companies or non-profit organizations and solar PV waste management advisors to help them deal with the problem of EOL panels [63]. Currently, the Czech company, Retina offers both reprocess and advisor service in relation to the reprocessing management. In Europe, the WEEELABEX organization which operates out in Czech Republic is responsible for the preparation of standards and the awarding of certification in respect to collection, storage, processing and reprocessing of WEEE and the monitoring of waste-processing companies [65]. In Italy, a significant drive towards the accountable management of the EOL PV modules were the Legislative Decree No. 49 of 14 March 2014 that implements the Directive on WEEE (Directive 2012/19/EU) [66]. According to this decree, decommissioned PV panels were involved in the types of household and professional WEEE for boosting the exploitation of secondary raw materials to endorse a more efficient use of the natural resources used in their production. The Decree also states the minimum aims assuring that at least 75% (by weight) of the modules be recovered, and that at least 65% (by weight) undergo the recycling process. Subsequently, recovery of 80% and recycling of 70% is projected. The public body member for monitoring the accomplishment of the objectives set is the Italian National Institute for Environmental Protection and Research (ISPRA) [66]. It annually transmits a detailed report to the Ministry of the Environment and Protection of the Territory and the Sea notifying about the quantities and categories of electrical and electronic equipment located on the market, prepared for reuse, recycled, and recovered.

Outside of Europe, a few countries have addressed the issue of solar panel waste regulations. Some developing countries, for instance, India, North Korea, Thailand etc. are yet to consider any waste management regulation for solar PV waste recycling [13]. South Korea has just initiated the discussion about PV waste. PV waste is included as one of industrial wastes in Annex Table 4 of Article 4.2 of South Korea’s Enforcement Rule of Wastes Control Act (Act No. 14783). Article 4.2 outlines complete classifications of waste and possible recyclables [67]. In 2017, the Ministry of Trade, Industry, and Energy decided to establish a facility to recycle PV module waste in North Chungcheong Province, South Korea [67]. In Japan, solar panel waste recycling is under the control of the Japanese environment ministry and solar panel manufacturers participate with local companies in research on recycling technology that relates to recycling technology in Europe [13]. Moreover, the European PV organization and Shell Oil Company (Japan) have entered into an association. NPC, a solar-panel and equipment manufacturer, has entered into a joint venture with Hamada (an industrial waste-processing company), to recycle solar panels. In 2016, the two companies jointly established a PV processing improvement project through the New Energy Industrial Technology Development Organization (NEDO) [4,68]. In USA, the state of California Department of Toxic Substances Control (DTSC) offered to take responsibility for solar waste treatment, when European facilities’ capacity decreased and the DTSC has now increased its recycling capacity and upgraded their facilities for the disposal of hazardous materials after treatment [69]. USA-based solar panel manufacturing company, First Solar has established factories in the United States, Germany and Malaysia, which also employ recycling methods with recovery rates of 95% for Cd and 90% for glass [13,70]. Even China does not yet have strong policies relating to recycling and even its environmental protection authority has not yet focused on waste recycling [64,71]. However, Both Yingli Solar and Trina Solar are studying solar PV development and recycling. Moreover, the state of Victoria (Australia) government have established the consequence of ensuring that procedures are in place to deal with the issues related to solar PV waste [72]. The decision of Australian ministry would lead pioneering systems reducing the environmental impact caused during the lifecycle of solar PV techniques [24,72]. These attempts are part of an industry-led charitable invention organization composition to focus on the capability developing dangers of solar PV structure and their waste. The solar PV components are listed under the National Product Administration Act as a signal to the objective to believe a programme in contracting solar waste [24,73].

Different types of waste, particularly electronic waste, are being regarded as a liability which should be managed by the manufacturer of the products [13]. Making manufacturers liable for PV panels EOL would encourage a sustainable management of PV materials [[74][75][76][77]]. Moreover, manufacturers should be encouraged to adopt environmentally friendly designs by enforcing appropriate regulations. This would help to reduce the environmental impact of PV products. It can also be aided by conserving resources through the collection and recycling of EOL products as well as promoting the manufacture of new solar panels by using recycled materials [78]. Finally, strict laws should be passed in relation to the collection and recycling process, which will help the creation of a logistical network to support the productive technology and to create links in an environmentally friendly supply chain [79].

6. Social and environmental advantages

At the end of 2016, various estimates of the volume of solar PV waste was ranged between 43,000 and 250,000 tonnes worldwide. Comparatively, the small amount that is currently being produced renders reprocessing not economically viable with the projected growth of waste PV panels up to 2050 with different projections based on regular and early loss scenarios [14]. Based on the increase in the installed PV generation capacity in the current decade, the number of EOL panels will necessitate a strategy for recycling and recovery. The worldwide ratio of solar PV waste to new installations is expected to increase considerably over time as shown in Fig. 8. It will reach between 4% and 14% of total generation capacity by 2030 and approximately rise over 80% by 2050. Based on literature, analysing the expected rates of panel installation and solar panels EOL, most of those will be c-Si over the next several years [43,59,80]. Therefore, the methods of dealing with solar PV waste material, principally by recycling need to be established by 2040. By recycling solar PV panels EOL and reusing them to make new solar panels, the actual number of waste (i.e., not recycled panels) could be considerably reduced. Scenarios that involve recycling were analysed by Cucchiella and Rosa [81] based on net present value and discounted payback period rubrics with the aim of supporting management strategies in respect to recycling plants, with particular reference to the economic viability of plants of various sizes. A 2.6 MW conventional power station causes an annual volume of 1480–2220 tonnes CO2 eq emissions and this could be saved by recycling 186 tonnes solar PV waste [14]. Such a saving would have a considerable positive impact on the environment and would reduce emissions from power generation by around 49470 tonnes CO2 eq over the 20-life of a power station [14]. It has been estimated that the output from a 1903 MW conventional generating facility would be equivalent to recycle 1480 tonnes solar PV waste. It would reduce emissions by around 11840–17760 tonnes CO2 eq over the lifetime of the plant, a saving that equate to 396770 tonnes CO2 eq [13,14]. Moreover, Te recovery is important from both the environmental and economic perspectives. CdTe modules can be produced from recycled Te, and thus reducing the need to extract more of this limited natural resource.

Fig. 8

7. Conclusion

Based on the swift growth in the installed PV generation capacity, we propose that the number of EOL panels will necessitate a strategy for recycling and recovery which need to be established by 2040. CO2 emissions could also be reduced by recycling solar PV waste which will consequently pose substantial positive impact on the environment. Therefore, this review scrutinized the necessity for solar PV recycling policies by analysing the existing recycling protocols. Recent studies have found it difficult to assess the future consequences of current research, development and testing efforts for PV panel recycling techniques. There are currently not enough indications on policies to handle these problems. Particularly in China, there is a lack of regulations on solar panel recycling. Furthermore, in Asia, countries should help to protect their natural environments by developing an environmentally friendly recycling industry and enforcing regulations to encourage reprocessing and the safe disposal of waste. This study contributes to literature on evaluating the sustainability of EOL management of PV panels, and paves the way for future researchers to comprehend the issues involved in the sustainable development of the PV sector. We recommend that recycling should be made commercially necessary by making manufacturers responsible for recovering materials from solar PV panels EOL. In summary, the management of panels EOL and other hazardous waste is obligatory. Additionally, governments must adopt hard-line policies to enforce the manufacturers of solar PV materials to consider the consequence of their products on the environment. It is also essential to gain the support of the mass-media, social media, public, and non-governmental organizations. It is indispensable to put pressure on manufacturers to act responsibly and to extend the responsibilities of producer not only in the solar PV manufacturing sector, but also throughout the entire energy industry, to be responsible for the eventual disposal or reuse of the products. All in all, it is expected that the pace of R&D will accelerate permitting researchers to resolve issues and contribute to the PV module recycling schemes, as well as for the end-of-life management of PV modules.


The authors would like to acknowledge the contribution of Thailand’s Education Hub for Southern Region of ASEAN Countries Project (THE-AC) with code number THE-AC 062/2017. The authors admit and appreciate the contribution of The Solar Energy Research Institute of The National University of Malaysia (UKM) through the research grant number GUP-2017-031. Due appreciation is also credited to the Institute of Sustainable Energy (ISE) of the Universiti Tenaga Nasional (@The National Energy University) of Malaysia for their valuable support through the BOLD2025 Programme.

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Operation & Maintenance Best Practices Guidelines – Version 3.0


Welcome to Version 3.0 of SolarPower europe’s Operation and Maintenance (O&M) Best Practices Guidelines. This edition, coordinated by BayWa r.e. Operation Services S.r.l., brings forward the success of the first two editions, led by First Solar and then Alectris, by covering a number of new topics and further refining existing chapters – all this with the support of a constantly growing O&M Task Force community.

Europe is not the continent with the largest fleet of solar power plants anymore. it remains, however, the continent with the oldest fleet and therefore a considerable amount of expertise in solar O&M. O&M, being the most job and value intensive segment in the solar power value chain in Europe, is responsible for about one third of all solar jobs created and gross value added: it is indeed a segment of great importance.

the members of the SolarPower Europe O&M task Force have decided to put on paper and share in these Best Practices Guidelines their know-how and experience in this field. the Guidelines were first published in 2016 to address quality issues in solar O&M and by 2018, they have become a living document with an active community behind, today already consisting of nearly one hundred top experts from nearly 50 companies.

Version 3.0 further refines existing chapters and covers a variety of important new topics with three brand new chapters on “revamping and repowering”, “O&M for distributed solar” and “innovations and trends”. repowering is becoming an increasingly important business segment within O&M, particularly in Europe where the plants are in operation since many years, while O&M in distributed solar is an interesting yet largely untapped segment with a number of specificities as compared to utility-scale best practices. We thank the European association of Electrical Contractors (aiE) for their support to the latter chapter. trends and innovations such as smart power plant monitoring, data-driven O&M, retrofit coatings for solar panels and O&M for solar power plants with batteries have been addressed in a new standalone chapter, introducing some topics that are expected to become more relevant in the years to come. the chapter on Environment, health & Safety has been complemented thanks to the support of Solar trade association, with useful information on how solar power plants can contribute to preserving and enhancing their natural environment. also, the annual Maintenance Plan has been updated, streamlined and simplified.

2018 was a very active year also in terms of spin-off activities related to the O&M Best Practices Guidelines. in June, we launched the Solar O&M Best Practices Mark (, a quality label based on the recommendations of the Guidelines. the Mark has already been adopted by a dozen leading O&M contractors. We organised four webinars on O&M best practices for various national solar industry associations and their members. last but not least, as part of a partnership between SolarPower Europe and the Mexican solar industry association asolmex and with the support of the German development cooperation GiZ, we translated the Guidelines into Spanish and organised an O&M best practices workshop in Mexico City, where our O&M task Force members presented the Guidelines chapter by chapter and discussed with Mexican experts.

these successful actions have reconfirmed the significance of the O&M Best Practices Guidelines for the industry and SolarPower Europe will continue its dissemination efforts in 2019 in Europe and beyond. Join the O&M task Force if you would like to be part of this undertaking and if you would like to contribute to the upcoming Version 4.0

Enjoy reading this report!

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Too much of a good thing: Inverter hyper-clipping

In earlier articles we’ve already pointed out that inverter clipping isn’t as significant as most people think, and that in a grid-power-constrained system it may be economically optimal to have a rather large DC-to-AC ratio. But what if there was a situation that resulted in significantly higher (and unexpected) inverter clipping losses of 30% or more? We’ll show you how to understand and avoid these cases of inverter “hyper-clipping.”

What really happens when inverters clip power?

It’s easy to say that the inverter “clips the excess power,” but from a physics point of view, that doesn’t describe what is going on. You can’t just “throw away” power you don’t want—and inverters don’t have air conditioners they can turn on when they need somewhere to send the excess energy. The main tool an inverter has is setting its DC voltage—and this is actually how an inverter is able to drop the system power.

It helps to visualize this issue graphically. A solar array has a power-voltage curve that illustrates the relationship between the operating voltage and the array’s output power. The modules can perform anywhere on the curve, and it’s the inverter’s job to pick the spot on the curve—ideally at the spot that maximizes the power (called the max power point, or MPP).

Figure 1: Typical array power-voltage curve

At the same time, an inverter has a maximum operating power and a voltage range it operates within. We can visualize the inverter’s operating range as a rectangle.

Figure 2: Array power-voltage curve in over-power clipping

When an inverter is in an over-power clipping mode, the array is producing more power than the inverter can handle. The inverter will increase the DC operating voltage, pulling the modules off of their max power point, until the modules’ DC power is within the inverter’s operating range. You can see this as the green point in Figure 2. The inverter protects itself while maintaining maximum power production. The modules end up dissipating the excess power as heat, but as we’ll show at the end of the article, this isn’t a big deal.

However, there is a scenario where this behavior can cause problems. Specifically, look at what happens if the arrays’ power-voltage curve doesn’t intersect the inverter’s operating range. The process we described above (the inverter increasing the operating voltage until the modules’ DC power is within the inverter’s operating range) doesn’t work. Instead, the array will miss the inverter voltage window and trip off—for that period of time, the energy production will be zero. Note that this is by definition happening at a time when the array is at peak production—so just a few times a year can have a serious impact on the array’s energy production!

Figure 3: Array power-voltage curve in over-power and over-voltage condition

So how might this come up? 

The description above is a theoretical framework, but how might this issue come up in an actual system?

There are a few ingredients needed to make this happen: a location with lots of sun (high power) combined with relatively cold temperatures (high voltages), high designed string voltage relative to the inverter’s max operating voltage and a large DC-to-AC ratio.

We can look at the power and temperature properties for a few locations around the US, and it looks like there are a few cities that are at elevated risk for this (again, high irradiance relative to temperature). We’ll use Los Angeles for the analysis here.

Figure 4: Sunlight and temperature by location

We then design a system in Los Angeles with an inverter with a max MPP voltage of 750 V (combined with a 1000 V Voc string), and 1.5 DC/AC ratio.

Figure 5: Loss chart for hyper-clipping simulation

We can see that the clipping losses can be as high as 32%, caused by 15% of operating hours where the array goes into hyper-clipping and trips to zero.

In terms of seasonality, these clipping losses persist for most of the year, with clipping losses above 30% for seven months of the year.

Figure 6: Clipping losses by month

Sensitivity to design choices

It’s worth illustrating how these two factors interact. Note that if we start with a base case of an array with a 1.2 DC-to-AC ratio and an inverter with a wider max voltage of 820 V, then there is no clipping loss. Each factor independently will lead to clipping of 5.7% (for increasing the DC/AC ratio to 1.5), and 0.6% (for dropping the inverter’s voltage to 750 V. But together, the clipping losses jump to 32.4%—approximately five times the sum of the individual effects.

The good news is that HelioScope will properly simulate these losses—so if you are ever at risk of hitting these conditions, you’ll find out before you build the array. And it’s a reminder that inverters aren’t just black boxes that turn DC power into AC power. The nuances of their behavior (including the operating voltage range) can make a big impact on energy yield.

How much heat does this create at the module? 

This description of clipping often raises questions about the module health. Basically, if the inverter isn’t ‘clipping’ excess power but the modules are, then does this damage the module?

To re-state the process described above: During inverter clipping, the modules are working off of their maximum power point. So at a moment when a module wants to produce, say, 320 W, it is only able to deliver 240 W to the inverter. The difference (in the example, 80 W) results in heat at the module. So, how much heat are we talking about?

Here, it helps to think in terms of thermodynamics. Modules are only about 20% efficient at converting sunlight into energy—and the rest, 80%, is largely dissipated as heat. So, say an inverter is clipping 25% of the array’s production (as in the example above). Then in the broader context of the sunlight, the 20% efficient module is only converting 15% of the sunlight’s energy to power, with the resulting energy, 85% of the sunlight, being converted to heat. Compared to the base case (80% of sun’s energy converted to heat) this is an increase of ~6%. Sure, any extra heat isn’t ideal—but any well-made module should have no problem handling that extra heat.

By Paul Grana, co-founder, Folsom Labs

Source: Solar Power World

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FUTURE OF SOLAR PHOTOVOLTAIC Deployment, investment, technology, grid integration and socio-economic aspects – IRENA Nov 2019 – A must read

THE DECARBONISATION OF THE ENERGY SECTOR AND THE REDUCTION OF CARBON EMISSIONS TO LIMIT CLIMATE CHANGE ARE AT THE HEART OF THE INTERNATIONAL RENEWABLE ENERGY AGENCY (IRENA) ENERGY TRANSFORMATION ROADMAPS. These roadmaps examine and provide an ambitious, yet technically and economically feasible, pathway for the deployment of low-carbon technology towards a sustainable and clean energy future. 

IRENA HAS EXPLORED TWO ENERGY DEVELOPMENT OPTIONS TO THE YEAR 2050 AS PART OF THE 2019 EDITION OF ITS GLOBAL ENERGY TRANSFORMATION REPORT. The first is an energy pathway set by current and planned policies (Reference Case). The second is a cleaner climate-resilient pathway based largely on more ambitious, yet achievable, uptake of renewable energy and energy efficiency measures (REmap Case), which limits the rise in global temperature to well below 2 degrees and closer to 1.5 degrees, aligned within the envelope of scenarios presented in the 2018 report of the Intergovernmental Panel on Climate Change (IPCC).

THE PRESENT REPORT OUTLINES THE ROLE OF SOLAR PHOTOVOLTAIC (PV) POWER IN THE TRANSFORMATION OF THE GLOBAL ENERGY SYSTEM BASED ON IRENA’S CLIMATE-RESILIENT PATHWAY (REMAP CASE), specifically the growth in solar PV power deployment that would be needed in the next three decades to achieve the Paris climate goals. 

This report’s findings are summarised as follows:

ACCELERATED DEPLOYMENT OF RENEWABLES, COMBINED WITH DEEP ELECTRIFICATION AND INCREASED ENERGY EFFICIENCY, CAN ACHIEVE OVER 90% OF THE ENERGY-RELATED CARBON DIOXIDE (CO2) EMISSION REDUCTIONS NEEDED BY 2050 TO SET THE WORLD ON AN ENERGY PATHWAY TOWARDS MEETING THE PARIS CLIMATE TARGETS. Among all low-carbon technology options, accelerated deployment of solar PV alone can lead to significant emission reductions of 4.9 gigatonnes of carbon dioxide (Gt CO2) in 2050, representing 21% of the total emission mitigation potential in the energy sector. 

ACHIEVING THE PARIS CLIMATE GOALS WOULD REQUIRE SIGNIFICANT ACCELERATION ACROSS A RANGE OF SECTORS AND TECHNOLOGIES. By 2050 solar PV would represent the second-largest power generation source, just behind wind power and lead the way for the transformation of the global electricity sector. Solar PV would generate a quarter (25%) of total electricity needs globally, becoming one of prominent generations source by 2050

SUCH A TRANSFORMATION IS ONLY POSSIBLE BY SIGNIFICANTLY SCALING UP SOLAR PV CAPACITY IN NEXT THREE DECADES. This entails increasing total solar PV capacity almost sixfold over the next ten years, from a global total of 480 GW in 2018 to 2 840 GW by 2030, and to 8 519 GW by 2050 – an increase of almost eighteen times 2018 levels. 

THE SOLAR PV INDUSTRY WOULD NEED TO BE PREPARED FOR SUCH A SIGNIFICANT GROWTH IN THE MARKET OVER THE NEXT THREE DECADES. In annual growth terms, an almost threefold rise in yearly solar PV capacity additions is needed by 2030 (to 270 GW per year) and a fourfold rise by 2050 (to 372 GW per year), compared to current levels (94 GW added in 2018). 

Thanks to its modular and distributed nature, solar PV technology is being adapted to a wide range of off-grid applications and to local conditions. In the last decade (2008–18), the globally installed capacity of off-grid solar PV has grown more than tenfold, from roughly 0.25 GW in 2008, to almost 3 GW in 2018. Off-grid solar PV is a key technology for achieving full energy access and achieving the Sustainable Development Goals. 

AT A REGIONAL LEVEL, ASIA IS EXPECTED TO DRIVE THE WAVE OF SOLAR PV CAPACITY INSTALLATIONS, BEING THE WORLD LEADERS IN SOLAR PV ENERGY. Asia (mostly China) would continue to dominate solar PV power in terms of total installed capacity, with a share of more than 50% by 2050, followed by North America (20%) and Europe (10%). 

SCALING UP SOLAR PV ENERGY INVESTMENT IS CRITICAL TO ACCELERATING THE GROWTH OF INSTALLATIONS OVER THE COMING DECADES. Globally this would imply a 68% increase in average annual solar PV investment from now until 2050 (to USD 192 billion/yr). Solar PV investment stood at USD 114 billion/ yr in 2018.

INCREASING ECONOMIES OF SCALE AND FURTHER TECHNOLOGICAL IMPROVEMENTS WILL CONTINUE TO REDUCE THE COSTS OF SOLAR PV. Globally, the total installation cost of solar PV projects would continue to decline in the next three decades. This would make solar PV highly competitive in many markets, with the average falling in the range of USD 340 to 834 per kilowatt (kW) by 2030 and USD 165 to 481/kW by 2050, compared to the average of USD 1 210/kW in 2018. 

The levelised cost of electricity (LCOE) for solar PV is already competitive compared to all fossil fuel generation sources and is set to decline further as installed costs and performance continue to improve. Globally, the LCOE for solar PV will continue to fall from an average of USD 0.085 per kilowatt-hour (kWh) in 2018 to between USD 0.02 to 0.08/kWh by 2030 and between USD 0.014 to 0.05/kWh by 2050. 

THE SOLAR PV INDUSTRY IS A FAST-EVOLVING INDUSTRY, CHANGING RAPIDLY THANKS TO INNOVATIONS ALONG THE ENTIRE VALUE CHAIN AND FURTHER RAPID COSTS REDUCTIONS ARE FORESEEN. First- generation technologies remain the principal driver of solar industry development and still hold the majority of the market value. Tandem and perovskite technologies also offer interesting perspectives, albeit in the longer term several barriers still need to be overcome. The emergence of new cell architectures has enabled higher efficiency levels. In particular, the most important market shift in cell architecture has resulted from bifacial cells and modules, driven by the increased adoption of advanced cell architecture, such as passive emitter and rear cell (PERC), and by its compatibility with other emerging innovations, such as half-cut cells and others.

TAKING ADVANTAGE OF FAST-GROWING SOLAR PV CAPACITY ACROSS THE GLOBE, SEVERAL RESEARCH PROJECTS AND PROTOTYPES ARE ONGOING TO STIMULATE FUTURE MARKET GROWTH BY EXPLORING INNOVATIVE SOLAR TECHNOLOGIES AT THE APPLICATION LEVEL. One example is building-integrated photovoltaic (BIPV) solar panels. BIPV solutions offer several advantages, such as multifunctionality (they can be adapted to a variety of surfaces), cost-efficiency (savings on roofing material, labour/construction, refurbishment and renovation costs), versatility and design flexibility in size, shape and colour.

Solar panels have improved substantially in their efficiency and power output over the last few decades. In 2018, the efficiency of multi-crystalline PV reached 17%, while that of mono-crystalline reached 18%. This positive trend is expected to continue through to 2030. Yet, as the global PV market increases, so will the need to prevent the degradation of panels and manage the volume of decommissioned PV panels leading to circular economy practises. This includes innovative and alternative ways to reduce material use and module degradation, and opportunities to reuse and recycle PV panels at the end of their lifetime.

TECHNOLOGICAL SOLUTIONS AS WELL AS ENABLING MARKET CONDITIONS ARE ESSENTIAL TO PREPARE FUTURE POWER GRIDS TO INTEGRATE RISING SHARES OF SOLAR PV. To effectively manage large-scale variable renewable energy sources, flexibility must be harnessed in all sectors of the energy system, from power generation to transmission and distribution systems, storage (both electrical and thermal) and, increasingly, flexible demand (demand-side management and sector coupling). Some countries, particularly in Europe, have achieved much higher shares in 2017: the VRE share in Denmark reached 53%, in South Australia 48%, and in Lithuania, Ireland, Spain and Germany over 20%. Globally, to integrate 60% variable renewable generation (of which 25% from solar PV) by 2050, average annual investments in grids, generation adequacy and some flexibility measures (storage) would need to rise by more than one-quarter to USD 374 billion/year, compared to investments made in electricity networks and battery storage in 2018 (USD 297 billion/year). 

INNOVATIVE BUSINESS MODELS AND COST COMPETITIVENESS OF SOLAR PV ARE DRIVING THE REDUCTIONS IN SYSTEM PRICES. The deployment of rooftop solar PV systems has increased significantly in recent years, in great measure thanks to supporting policies, such as net metering and fiscal incentives- which in some markets make PV more attractive from an economic point of view than buying electricity from the grid- PV-hybrid minigrid, virtual power plants and utility PPA. The competitiveness of distributed solar power is clearly evident amid rising deployment in large markets, such as Brazil, China, Germany and Mexico, however important differences remain between countries, which highlight the further improvement potential.

IF ACCOMPANIED BY SOUND POLICIES, THE TRANSFORMATION CAN BRING SOCIO-ECONOMIC BENEFITS. The solar industry would employ more than 18 million people by 2050 (of which 14 million would be employed by solar PV) four times more than the 2018 jobs total of 4.4 million (3.6 million – solar PV). To maximise outcomes of the energy transition, however, a holistic policy framework is needed. Deployment policies will need to co-ordinate and harmonise with integration and enabling policies. Under the enabling policy umbrella, particular focus is needed on industrial, financial, education and skills policies to maximise the transition benefits. Education and skills policies can help equip the workforce with adequate skills and would increase opportunities for local employment. Similarly, sound industrial policies that build upon domestic supply chains can enable income and employment growth by leveraging existing economic activities in support of solar PV industry development.

UNLEASHING THE MASSIVE POTENTIAL OF SOLAR PV IS CRUCIAL TO ACHIEVE CLIMATE TARGETS. This is only possible by mitigating the current barriers at different scales (policy; market and economic; technology; regulatory, political and social). Grid integration and grid flexibility, economies of scale, access to finance, lack of standards and quality measures, consumer awareness are among the key barriers that could hinder the deployment of solar PV capacities in the next three decades. Mitigating the existing barriers immediately, through a range of supportive policies and implementation measures including innovative business models, financial instruments is vital to boost future deployment of solar PV capacities to enable the transition to a low-carbon, sustainable energy future.

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Table of Contents



  1. A  Supplementary LCOS Analysis Materials 11
  2. B  Supplementary Value Snapshot Materials
    1. 1  Landscape of Energy Storage Revenue Potential 15
    2. 2  Value Snapshot Supporting Materials 20
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