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MNRE Releases Draft Testing and Approval Guidelines for Solar Inverters

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					</table>The Ministry of New and Renewable Energy (<a href="https://mnre.gov.in/" target="_blank" rel="noopener">MNRE</a>) has released draft guidelines for the approval and testing of solar inverters under the Solar Systems, Devices, and Components Goods Order, 2025.
MNRE had <a href="https://www.mercomindia.com/mnre-sets-efficiency-standards-for-solar-modules-inverters-and-batteries" target="_blank" rel="noopener">released</a> the order in January this year, aiming to enhance the quality and reliability of inverters and other components and increase the adoption of high-performance solar technologies.
It has invited industry stakeholders to share their comments.
Under the guidelines, manufacturers must submit a declaration specifying their products’ series at the time of submitting samples to the test laboratory.
The laboratory will charge testing fees only for the highest-rated inverter model under the IS 16221 (Part II): 2015 and IS 16169: 2019 requirements. A single test report will then be issued for all lower-wattage models in that series, which are covered under the same model family.
Series Guidelines
The firmware can have different limit settings per the series’ model rating. Products with different hardware architectures and firmware functionalities will be tested separately.
All models within a family will have the same rated input/output voltage, frequency, and number of phases at the output.
They will also feature the same printed circuit board (PCB) design and layout, power stage topology, and insulation. Additionally, they must have the same control algorithm and firmware, cabinet design, and class of construction.
If the cabinet design architecture changes between various models within the family, then all the different cabinet designs must be tested or verified for ingress protection.
The maximum-rated inverter within the family will be considered the representative test sample for all the models for safety tests. Manufacturers must provide the product datasheet, International Electrotechnical Commission certification, PCB wiring diagrams, and other relevant documentation.
Inverters must have clear and indelible markings and warning labels that display the manufacturer&#8217;s name and trademark, model and serial number, code, input and output voltage, and manufacturing location.
Retesting Guidelines 
The inverters will be tested under two sequences.
Sequence 1 includes testing for load transfer, electrical rating, thermal endurance, protection against electrical shock, backfeed voltage protection, single fault conditions, and protection against sonic pressure, fire, and electric shock and energy hazards. It also includes additional testing for grid-interactive inverters.
Sequence 2 includes testing environmental requirements and conditions, physical requirements, mechanical resistance to deflamation, effects of impact or drop, and protection against liquid, chemical, mechanical, and fire hazards.
Both sequences will have a voltage test.
Manufacturers must submit a new sample if the previous one fails Sequence 1 of testing. Only the tests in Sequence 1 will be repeated after the components and construction are verified. Similar procedures will be followed if the test fails in Sequence 2.
Test labs will charge an appropriate retesting fee for all repeat tests.
Pass criteria for solar inverters must adhere to IS 16169 and IS 16221 Part ll wherever applicable.
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					</table>A team of researchers from the <a href="https://www.unsw.edu.au/" target="_blank" rel="noopener">University of New South Wales</a> and the Chinese solar module manufacturer <a href="https://www.longi.com/in/" target="_blank" rel="noopener">LONGi</a> found that the rear side of tunnel oxide passivated contact (TOPCon) cells, particularly the silicon nitride (SiNx) layer, is prone to chemical degradation when exposed to sodium-based salts, resulting in a significant loss of open-circuit voltage.
Open-circuit voltage is the difference in electrical potential between two terminals of a device disconnected from the circuit without any external load and current flow.
The research, titled “Mitigating contaminant-induced surface degradation in TOPCon solar cells: Mechanisms, impacts, and mitigation,” was published in Science Direct.
The researchers utilized a 10 nm aluminum oxide (AlOx) barrier layer, deposited through atomic layer deposition (ALD), to effectively mitigate these degradation pathways.
The report said that accelerated damp heat (DH) testing demonstrates that the ALOx barrier improves the TOPCon solar cells’ long-term stability, reducing degradation and maintaining performance over extended periods.
The research was conducted on industrial n-type TOPCon solar cells with double-sided pyramid texturing and an average power conversion efficiency of approximately 23%. The rear side was structured with a tunneling silicon oxide layer and a phosphorus-doped polycrystalline silicon layer to form the n-type TOPCon configuration. It was further capped with an additional SiNx ARC layer.
<a href="https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina.jpg"><img loading="lazy" decoding="async" class="aligncenter wp-image-78284 size-full" src="https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina.jpg" alt="TOPCon research article" width="665" height="458" srcset="https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina.jpg 665w, https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina-300x207.jpg 300w, https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina-650x448.jpg 650w, https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina-624x430.jpg 624w, https://mercomindia.s3.ap-south-1.amazonaws.com/wp-content/uploads/2025/04/TOPCon-reserach-article-Tina-600x413.jpg 600w" sizes="(max-width: 665px) 100vw, 665px" /></a>
The solar cells’ electrical performance was assessed using a light output and normal analysis system from photovoltaic tools equipped with a five-rail pin contact frame to measure current-voltage characteristics.
Applying sodium acetate to the front of the TOPCon solar cells resulted in an approximate 0.87% degradation in their power conversion efficiency (PCE). This degradation was primarily due to a minor decline in the fill factor associated with a roughly 35% relative rise in the cell’s series resistance during the 20-hour DH85 (hydro-moisture meter) test.
The fill factor is a measure to gauge a solar cell’s efficiency. Solar cells with a higher fill factor are more efficient.
The researchers found that applying sodium acetate to the rear of the solar cells resulted in a 16% PCE decline. This decline was caused by a 450% relative increase in the cell’s series resistance, reducing the fill factor by 9.4%.
The report indicated that open-circuit voltage losses can reach up to 5.8%, resulting in an approximate 16% decrease in overall cell efficiency.
One of its key findings was the 10 nm AlOx barrier’s protective role on the cells. The layer was deposited through an industrial-scale ALD process. It reduced performance degradation, demonstrating only a minor PCE decrease and maintaining open-circuit voltage stability after 20 hours of accelerated DH testing.
The AlOx layer also mitigated corrosion and recombination defects induced by sodium-related salts.
The report claims that these findings confirm the AlOx layer’s potential as a viable protective solution to enhance the TOPCon solar cells’ long-term reliability under harsh environmental conditions.
Recently, China-based solar module manufacturer JinkoSolar Holding <a href="https://www.mercomindia.com/jinkosolar-perovskite-solar-cell-efficiency" target="_blank" rel="noopener">claimed</a> that its N-type TOPCon-based perovskite tandem solar cell achieved a conversion efficiency of 33.84%, surpassing its previous record of 33.24%.
In December 2024, another solar cell and module manufacturer, Qcells, <a href="https://www.mercomindia.com/qcells-claims-28-6-perovskite-silicon-tandem-solar-cell-efficiency" target="_blank" rel="noopener">announced</a> achieving a 28.6% tandem solar cell efficiency on a full-area M10-sized cell that can be scaled for mass manufacturing.

Mitigating Chemical Degradation in TOPCon Solar Cells

The International Electrotechnical Commission (<a href="https://www.iec.ch/" target="_blank" rel="noopener noreferrer">IEC</a>) has issued a new standard – the IEC 62938:2020 &#8211; to test the resistance of solar photovoltaic modules to large amounts of snow piling up on their surfaces.
The IEC defines the test standard as a method for determining how well a framed PV module performs mechanically under the influence of inclined non-uniform snow loads.
It said that this standard was introduced based on how previous market experiences have shown the need for a specific test method for measuring resistance to snow loads as needed. Previously, the IEC 61215-1:2016 was the closest equivalent to this test, and it contained various test methods to induce mechanical stresses to measure how well solar modules could withstand different loads.
The older test, however, was constrained as it could only be used to assess uniform loads on a horizontal plane, unlike the new one which can test non-uniform loads on a sloped pane. The IEC said that there were several reports of bent and misaligned modules in areas with heavy snow.
It said that this was observed at large systems in mountainous areas where modules in the lower rows of sloped installations were affected. Because modules are installed at an inclined position, snow will slide down the panel and accumulate unevenly at the bottom edge of the frame. As a result of this, the lower part of the module needs to withstand greater stress. The IEC also noted that ice might also accumulate between the frame and glass, applying even more stress on the module.
The IEC noted that this standard was applicable only for framed modules with framed protruding beyond the first glass surface on the lower edge after installation, as <a href="https://upload.wikimedia.org/wikipedia/commons/b/ba/Young_girl_cleaning_photovoltaic_solar_panels_from_snow%2C_Grange_Farm%2C_UK.jpg" target="_blank" rel="noopener noreferrer">this</a> is what stops snow from sliding off the edge. This standard does not apply to other kinds of modules with back rails formed in frames, on the side, top, and lower edges which will not create an additional snow barrier.
Recently, a team of research scientists led by the University of New South Wales, in collaboration with the University of Sydney, have, for the first time, <a href="https://mercomindia.com/new-generation-solar-testing-standards/" target="_blank" rel="noopener noreferrer">produced</a> a new generation of experimental solar energy cells that have passed the International Electrotechnical Commission (IEC) testing standards for heat and humidity.
A little earlier, the Ministry of New and Renewable Energy also <a href="https://mercomindia.com/mnre-renewable-energy-standardization-cell-quality-standards/" target="_blank" rel="noopener noreferrer">decided</a> to set up a Renewable Energy Standardization Cell. The objectives of the cell are to identify the areas in renewable energy where standards need to be developed and identify international standards such as International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC) for applications in Indian climatic conditions. India’s northern region, especially Leh, Ladakh, and parts of Himachal Pradesh, experiences heavy snowfall in the winter season.
Image credit: 1010 Climate Action / CC BY (<a href="https://upload.wikimedia.org/wikipedia/commons/b/ba/Young_girl_cleaning_photovoltaic_solar_panels_from_snow%2C_Grange_Farm%2C_UK.jpg" target="_blank" rel="noopener noreferrer">2.0</a>)

IEC Issues New Standard for Testing Resistance of Solar Modules to Heavy Snow

The Gujarat State Electricity Corporation Limited (<a href="http://www.gsecl.in/" target="_blank" rel="noopener noreferrer">GSECL</a>) has successfully managed to operate its 500 MW Ukai unit under its coal-based power project at 40% of its capacity during a recently conducted low load test run.
This is the first time the state power corporation has been able to run its unit at the lowest possible load points while still maintaining all the other operating parameters under stable conditions and without any supplementary oil firing support.
With United States Agency for International Development’s help, this move is now the state’s first successful attempt to achieve greater load flexibility at its coal-based project to boost the integration of renewable power into its mix. These low-load tests will allow the power generators to more easily adapt their generation when the need for integrating more renewable energy in their mix arises, according to the Greening the Grid (GTG) Program update.
The low load test run was conducted under a pilot implemented under USAID’s GTG – Renewable Integration and Sustainable Energy (RISE) initiative in partnership with GSECL and Bharat Heavy Electricals Limited (BHEL), which is the Original Equipment Manufacturer.
“The outcomes of these test runs would enable GSECL to plan its fleet-wide strategy for 5,000 MW of its coal-based thermal units towards flexible operations to support renewable integration,” said B A Gandhi, Executive Engineer (Efficiency), GSECL.
Recently, the Union Minister of Coal and Mines, Pralhad Joshi, <a href="https://mercomindia.com/india-likely-to-stop-coal-imports/" target="_blank" rel="noopener noreferrer">announced</a> India’s plans to stop the import of thermal coal from 2023-2024. This follows reports that coal imports increased by 13% year-over-year. Coal-based power makes up the largest share of power generation in India. However, considering that India has the 5th largest coal reserves in the world, stopping imports is not significant news on its own.
Earlier, the Ministry of New and Renewable Energy (MNRE) came up with a <a href="https://mercomindia.com/mnre-bundle-thermal-solar-wind-round-clock-power/" target="_blank" rel="noopener noreferrer">draft plan</a> to supply round-the-clock (RTC) power from renewable (solar, wind, and hydro) projects, to be complemented with power from thermal projects.
Previously, Mercom <a href="https://mercomindia.com/solars-share-india-total-installed-power-capacity/" target="_blank" rel="noopener noreferrer">reported</a> that India’s total installed power capacity stood at about 371 GW as of December 31, 2019. Of this, renewables (including large hydro) accounted for about 133.2 GW, up from 122.8 GW last year, an 8.5% rise. Coal power installations still held the top spot with cumulative coal installations at around 198.5 GW or 53.5% of the total mix.
Thermal power, which includes coal, lignite, gas, and diesel, maintained its stronghold and continued to be the most significant contributor to the country’s power pool. Its cumulative installations rose to 230.7 GW by the end of December 2019, up from 223 GW last year. However, its overall share fell to 62.24% from 63.2% last year, highlighting the progress made by renewable energy capacity additions.

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