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Next Generation Encapsulant - Polyolefin (PO) - 15.12.18

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Encapsulants are used primarily to protect, preserve the solar cells and keeps the glass, solar cells and the back sheet integrated. This white paper on Encapsulant highlights the following:

Importance of Encapsulant as encapsulant degradation is a prime cause for module degradation.
Polyolefins (PO), a new encapsulant type reduces module degradation significantly and improve durability of the modules.
Ethylene Vinyl Acetate (EVA), the most commonly used encapsulant has a limitation that it produces Acetic Acid when exposed to heat & pressure and leads to module degradation.

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Next Generation Encapsulant - Polyolefin (PO) - 15.12.18

  1. 1. Gensol Group Next Generation Encapsulant – Polyolefin (PO) Reduced Energy Degradation From 0.7% To 0.3% Gensol Engineering Pvt. Ltd White Paper Copyright © Gensol Engineering Pvt. Ltd., 2018 Publication Date 14 12 18
  2. 2. Gensol Group 1. INTRODUCTION - PV MODULES With the blooming market of solar PV industries development across the globe, there is intense competition among IPPs, EPC contractors, manufacturers, consultants and other service providers in the PV sector. One of the very important factor for the selection of the solar PV modules is the quality of the modules which directly impacts the performance of module. For the solar developer, investor, EPC and O&M contractor in solar industry, it is very important to know the composition of solar module and why it degrades leading to huge loss of power and revenue. The main components of the solar module are as shown in Figure 1: 1. Top protective glass, 2. Interconnect PV cells between the encapsulants and 3. Back sheet. Figure 1 Solar PV Module Structure 1 Mike Rycroft(EE Publishers), 2016 & IEA PVPS 2014 Ethylene Vinyl Acetate (EVA) are the most commonly used encapsulant in industry. It has been understood that the EVA is one of the important component of the module as they are used primarily to protect, preserve the solar cells and keeps the glass, solar cells and the back sheet integrated. Thus, it supports the module mechanically and is responsible for its long-term reliability and performance. Encapsulant contributes about 4% of the total module production cost. Figure 2 Impact of Solar Module Components on Reliability 2. SOLAR PV MODULES - RELIABILITY The studies carried on PV solar modules shows the power output loss in the infant stage (when just exposed to light) is majorly caused by Light Induced Degradation (LID) upto 4%1 (generally in range of 1-2%). During midlife or operational phase, the losses are mainly due to degradation of Anti-
  3. 3. Gensol Group Reflective (AR) coating on glass (upto 3%), EVA encapsulant discoloring (upto 10%), and the rest is due to corrosion on the cells by the acetic acid from EVA. Figure 3 Degradation in PV Solar modules It very important to note that many mechanism of the power loss are directly or indirectly affected by the choice of encapsulants. In case of EVA encapsulant, deacetylation and hydrolysis of vinyl-acetate monomers result in generating acetic acid2, which leads to EVA discoloring or yellowing, corrosion on the cells, delamination, PID, snail trails. Figure 4 Evolving of acetic acid from EVA 2 http://www.eqmagpro.com/presentation-by-dr- debajyoti-sarangi-surjatech-at-suryacon-pune-2018/ 3 https://www.renewsysworld.com/encapsulants- conserv-poe 4 https://www.dow.com/elastomers/markets/photovolt aic/index.htm 3. CONCEPT OF ENCAPSULANT – POLYOLEFIN (PO) The solution is to find encapsulant which is free of acetic acid. Many manufactures like Renewsys3, DoW4, Borealis5, Cybrid tech6 etc. are coming up with a new concept of encapsulant (free of acetic acid) called Polyolefin (PO) which are polymers focused to reduce module degradation and improve durability of the modules. Polyolefin encapsulant are of two types – cross- linked i.e. Polyolefin elastomer (POE) and non- crosslinked i.e. Thermo-Plastic Polyolefin (TPO) that enables glass and PV cells to combine uniquely. Polyolefin (PO) has a quality of not producing any acetic acid due to which corrosion and decolourisation, PID and snail trails gets to virtually zero. Figure 5 Structure of Polyolefin 5 https://www.borealisgroup.com/polyolefins/energy/so lar 6 http://www.cybridtechnologies.com/products/encapsu lant/
  4. 4. Gensol Group Modules made with PO-based encapsulants sheets outperform those made with EVA in critical areas shown in Figure 6. Figure 6 Impact of Degradation on EVA Sequential experiments have been performed by various manufacturers that shows higher levels of PID resistance in PO-based module when compared with EVA-based module as depicted in Figure 7. Figure 7 Virtually Zero PID using POE, Renewsys, India The combined sequential stress testing of modules, where various stresses like damp heat, thermal cycle and UV are given either in combination and/or sequence, also proves the 7 PVSEC 2017, Amsterdam (po ster 5DV.3.14). Figure 8 Comparison of EL pictures, power loss, ISC, VOC and fill factor for both EVA and PO encapsulant on 60 cell module during combined stress test showing severe degradation of EVA base after 4th cycle of the stress test; Borealis97 robust long-term stability of PO based encapsulants as example shown in Figure 8. •Higher Resistivity •Lower Water Vapor Transmission Rate •No Yellowing or Optical transmission •Higher Energy Output •Reliable & Durable Key Performance Parameters
  5. 5. Gensol Group Modules manufacturers generally provides 25 years of the performance warranty for EVA based modules with 0.7%/year of degradation (from the 2nd year) excluding LID of 2.0% for the 1st year with 80.7% of power output at the end of 25 years. However, practically, the degradation is much worse and the Annual Linear Degradation Rates for PV modules vary from 1 to 5 %/year8&9 leading to about 69.5% of power output. Then again, experimental demonstrations show that Polyolefin based solar PV module reports in sustained levels of module efficiency and lower degradation in power output to 0.35%/year down from 0.7%/year. The cumulative drop in drop of power output shrinks by approximately 4 times at the end of 25th year. 8 http://borealisempoweringsolar.com/en/QuentysTM BPO http://www.ncpre.iitb.ac.in/research/pdf/All_India_Sur vey_of_Photovoltaic_Module_Reliability_2016.pdf Figure 9 Degradation Rates - EVA Vs Polyolefin Polyolefin (PO based encapsulant) is highly reliable and has potential to overrule EVA sheets by 202410. Currently in India, Renewsys has full fledge established manufacturing facility for Polyolefin (POE) as well as standard module and glass-to-glass solar PV modules based on POE. Other manufacturers like, Borealis have also started introducing PO based encapsulant for Indian market. 9 https://res.mdpi.com/technologies/technologies-05- 00022/article_deploy/technologies-05 00022.pdf?filename=&attachment=1 10 ITRPV Eight Edition 2017 Report 55. 67.5 80. 92.5 105. 0 5 10 15 20 25 POWEROUTPUT(%) YEARS Degradation Rates - EVA Vs Polyolefin Manufacturers Warranty (%) Practically Observed (%) Proposed Warranty (%) using Polyolefin 0.2 - 0.3% degradation/annum 0.5 - 0.7% degradation/annum 1 - 2% degradation/annum
  6. 6. Gensol Group Gensol Engineering Pvt Ltd | Gensol Consultants Pvt Ltd | Solarig Gensol Utilities Pvt Ltd Corporate Office A2, 12th Floor, Palladium, Opposite to Vodafone House, Prahladnagar, Ahmedabad, Gujarat. India - 380015 Email: solar@gensol.in | Web: www.gensol.in | Phone: +91 79 40068235 | Fax: +91 79 40068239 Gensol is one of the leading consultants and system integrators for Solar Power Plants. We boast of a portfolio of over 6000 MW of Solar Photovoltaic Plants. Gensol is also a channel partner to Ministry of New & Renewable Energy and installs kW scale Solar Rooftop systems on a turnkey basis with more than 42 MW of cumulative installations across the country. The information contained herein is of a general nature and is not intended to address the circumstances of any particular individual or entity. Although we endeavor to provide accurate and timely information, there can be no guarantee that such information is accurate as of the date it is received or that it will continue to be accurate in the future. No one should act on such information without appropriate professional advice after a thorough examination of the particular situation.

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