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Glass pyramid concentrator for solar cell applications

Image: Stanford University, Nina Vaidya

Stanford University scientists have built an optical concentrator that purportedly harvests more than 90% of the light that hits its surface.

From pv magazine

Researchers at Stanford University have created a glass pyramid optical concentrator that concentrates light on solar cells, regardless of the light incidence angle.

“It’s a completely passive system – it doesn’t need energy to track the source or have any moving parts,” said research coordinator Nina Vaidya. “Without optical focus that moves positions or need for tracking systems, concentrating light becomes much simpler.”

The AGILE (Axially Graded Index LEns) device purportedly harvests more than 90% of the light that hits its surface. It also creates spots at the output that are three times brighter than the incoming light.

“Installed in a layer on top of solar cells, they could make solar arrays more efficient and capture not only direct sunlight, but also diffuse light that has been scattered by the Earth’s atmosphere, weather, and seasons,” the scientists explained, noting that the solar cell could be built with fewer raw materials and at lower costs.

They said a top layer of the concentrator could be used to replace existing encapsulation materials. That would in turn create space for cooling and circuitry to run between the narrowing pyramids of the individual devices. The pyramid was made of different optical glass flats provided by Japan’s Ohara Corp.

“The geometry of the pyramid was a square of side 14.5 mm down to a square of 8.5 mm giving a concentration of three, along a total height of 8 mm with 8 glass layers, with each flat 1 mm thick,” the academics said.

They layered the glass together with polymers that bend light to different degrees. “The layers change the light’s direction in steps instead of a smooth curve,” they said. “The sides of the prototypes are mirrored, so any light going in the wrong direction is bounced back towards the output.”

The prototype can improve optical concentration by a factor of three and achieve a 90% efficiency in capturing light, they claimed in “Immersion graded index optics: theory, design, and prototypes, which was recently published in Microsystems and Nanoengineering.

“Results of the functional prototypes demonstrate that immersion graded index technology can improve the way we concentrate and couple light many fold,” the scientists said. “The AGILE has the potential to greatly improve opto-electronic systems by reducing cost, increasing efficiency, providing a scalable concentration system with built-in anti-reflection and encapsulation without the need for tracking.”

Author: Emiliano Bellini

Climate change is driving 2022 extreme heat and flooding

Cracked and dry earth is seen in the wide riverbed of the Loire River near the Anjou-Bretagne bridge as a heatwave hits Europe, in Ancenis-Saint-Gereon, France, Jun 13, 2022. Image: Reuters/Stephane Mahe

From Reuters

LONDON, June 28 (Reuters) – Extreme weather events – from scorching heatwaves to unusually heavy downpours – have caused widespread upheaval across the globe this year, with thousands of people killed and millions more displaced.

In the last three months, monsoon rains unleashed disastrous flooding in Bangladesh, and brutal heatwaves seared parts of South Asia and Europe. Meanwhile, prolonged drought has left millions on the brink of famine in East Africa.

Much of this, scientists say, is what’s expected from climate change.

On Tuesday, a team of climate scientists published a study in the journal Environmental Research: Climate. The researchers scrutinized the role climate change has played in individual weather events over the past two decades.

The findings confirm warnings of how global warming will change our world – and also make clear what information is missing.

For heatwaves and extreme rainfall, “we find we have a much better understanding of how the intensity of these events is changing due to climate change,” said study co-author Luke Harrington, a climate scientist at Victoria University of Wellington.

Less understood, however, is how climate change influences wildfires and drought.

For their review paper, scientists drew upon hundreds of “attribution” studies, or research that aims to calculate how climate change affected an extreme event using computer simulations and weather observations.

There are also large data gaps in many low- and middle-income countries, making it harder to understand what’s happening in those regions, said co-author Friederike Otto, one of the climatologists leading the international research collaboration World Weather Attribution (WWA).

HEATWAVES

With heatwaves, it’s highly probable that climate change is making things worse.

“Pretty much all heatwaves across the world have been made more intense and more likely by climate change,” said study co-author Ben Clarke, an environmental scientist at the University of Oxford.

In general, a heatwave that previously had a 1 in 10 chance of occurring is now nearly three times as likely — and peaking at temperatures around 1 degree Celsius higher – than it would have been without climate change.

An April heatwave that saw the mercury climb above 50C (122 Fahrenheit) in India and Pakistan, for example, was made 30 times more likely by climate change, according to WWA. 

Heatwaves across the Northern Hemisphere in June – from Europe to the United States – highlight “exactly what our review paper shows … the frequency of heatwaves has gone up so much,” Otto said.

RAINFALL AND FLOODING

Last week, China saw extensive flooding, following heavy rains. At the same time, Bangladesh was hit with a flood-triggering deluge.

Overall, episodes of heavy rainfall are becoming more common and more intense. That’s because warmer air holds more moisture, so storm clouds are “heavier” before they eventually break.

Still, the impact varies by region, with some areas not receiving enough rain, the study said.

DROUGHT

Scientists have a harder time figuring out how climate change affects drought.

Some regions have suffered ongoing dryness. Warmer temperatures in the U.S. West, for example, are melting the snowpack faster and driving evaporation, the study said.

And while East African droughts have yet to be linked directly to climate change, scientists say the decline in the spring rainy season is tied to warmer waters in the Indian Ocean. This causes rains to fall rapidly over the ocean before reaching the Horn. 

WILDFIRE

Heatwaves and drought conditions are also worsening wildfires, particularly megafires – those that burn more than 100,000 acres.

Fire raged across the U.S. state of New Mexico in April, after a controlled burn set under “much drier conditions than recognized” got out of control, according to the U.S. Forest Service. The fires burned 341,000 acres.

TROPICAL CYCLONES

On a global scale, the frequency of storms hasn’t increased. However, cyclones are now more common in the central Pacific and North Atlantic, and less so in the Bay of Bengal, western North Pacific and southern Indian Ocean, the study said.

There is also evidence that tropical storms are becoming more intense and even stalling overland, where they can deliver more rain on a single area.

So while climate change might not have made Cyclone Batsirai any more likely to have formed in February, it probably made it more intense, capable of destroying more than 120,000 homes when it hit Madagascar. 

Author: Gloria Dickie

NUS students build Singapore’s first electric race car; it goes from 0 to 100kmh in 3.9 seconds

From left: Muhammad Nazirul Syahmi Bin Abdullah, Muhammad Irfan bin Zakaria and Joven Thong Jie Wen with the R22e. Image: Lianhe Zaobo

From The Straits Times

SINGAPORE – Engineering students at the National University of Singapore (NUS) have built the country’s first electric race car, which can go from 0kmh to 100kmh in 3.9 seconds.

That is the acceleration recorded by some electric vehicles (EVs), including Tesla and Audi models.

The R22e, which was officially unveiled by Senior Minister of State for Transport Chee Hong Tat at the NUS Kent Ridge campus on Tuesday (June 28), can hit a maximum speed of 125.4kmh.

Fourth-year mechanical engineering student Muhammad Nazirul Syahmi, who was part of the team from the College of Design and Engineering, said they had little reference resources to lean on at the start.

“Many of our simulations and tests had to be created from scratch,” said the 24-year-old.

“As we did not have experience with high-voltage systems and EV technologies, we approached companies in the local industry to conduct workshops for us and self-studied under the guidance of NUS teaching staff, to learn how to handle electrical systems.”

Students of the college have built a total of 19 internal combustion engine race cars over the past 21 years.

But the R22e, which the students spent 18 months working on, is their first EV race car.

Since the inauguration of the NUS Formula Society of Automotive Engineering (FSAE) Race Car Project in 2001, students from the college have been constructing formula-style race cars for the FSAE Michigan competition.

The inter-varsity event is held annually in the United States.

Formula-style cars have a single-seat with an open cockpit and open wheels.

Earlier this month, the team of 26 students entered the electric FSAE race car for static events at the competition.

According to the vehicle specifications provided by the team, the car can produce 80 kilowatts of power, and with its acceleration and top speed, can surpass its internal combustion engine predecessors’ performance.

NUS FSAE project adviser, Professor Seah Kar Heng, said the rapidly growing global electric car market made it crucial for students to be equipped with knowledge about electric car technologies.

“As a school, we have to be in sync with the direction that the world is heading in, to move towards clean and green energy,” said Prof Seah, who has been guiding engineering students in the project since 2001.

“I wanted the students to be aware of that, and working on this electric race car is a very good start for them.”

In a speech at Tuesday’s event, Mr Chee congratulated the team and said the launch was timely and mirrors Singapore’s own effort to electrify its vehicle population.

“Our transition to EVs will bring new and exciting opportunities in the new green economy,” he said.

“Engineering students can look forward to jobs and training in new areas, such as EV software diagnostics, battery and charging infrastructure.”

Author: Deepanraj Ganesan

Single-axis trackers on commercial rooftops increase generation by 37%

Image: Alion Energy

Alion Energy trackers thread the return-on-investment needle with productivity gains from white roofs and bifacial modules, while design aggressively maximizes module count.

From pv magazine USA

Alion Energy’s single-axis tracker racking product was originally designed to be deployed in regions where heavy installation equipment was more challenging to access, but labor might be more available.

One aspect of this design philosophy is that the system is light and can be easily carried and assembled, and doesn’t require metal pilings to be driven deep into the ground. And interestingly, this carries over to commercial rooftops.

Mark Kingsley, Alion Energy CEO, said in a post on LinkedIn that a commercial real estate group had installed a standard rooftop, 10-degree fixed tilt monofacial solar array, as well as a competing Alion Energy system.

The results were as expected – 37.5% greater generation on a per watt basis from the single-axis tracker, on a pristine white thermoplastic roof versus standard modules. Of course, the real breakthrough is that they were able to get single-axis trackers installed on a commercial rooftop at all.

The rooftop in their example has a lot of skylights, and the overall structure is not facing due south. In this configuration, Alion Energy suggests that it can fit 4.55 MW of modules on the Maryland structure with a standard 10-degree installation. This system is projected to generate 1.34 kWh per watt each year.

Alion has designed a system that is 5.4 MW – a full 18% increase in wattage due to systems ability to be installed directly over skylights without needing the standard setback. Additionally, this hardware is projected to generate 1.54 kWh per watt installed per year.

In this case, that works out to 37% more electricity from the same rooftop. And when the trackers are directly attached to the roof – a 2.15 pounds per square foot dead load. Add in one Alion’s customized robotic cleaners, and the company says the levelized cost of electricity from the system falls to 4.67¢/kWh and generates 40% more electricity than a standard rooftop solar install.

And while this rooftop was selected to show off their hardware, it’s still an interesting best case scenario for us to consider.

Author: John Fitzgerald Weaver

Photon-enhanched rechargeable batteries for solar storage

Image: Image: National Institute for Materials Science (NIMS), Nano Research Energy, Tsinghua University Press

Japanese scientists have analyzed storage systems that combine PV and high-energy-density metal batteries. The rechargeable batteries have advantages such as low-charge voltage and high energy density, but stability and safety must be addressed before they reach commercial maturity.

From pv magazine

Researchers from the National Institute for Materials Science (NIMS) in Japan have reviewed different photo-enhanced rechargeable metal batteries featuring PV and high-energy-density metal batteries for direct solar-to-electrochemical energy storage.

They looked at devices integrating PV and lithium-ion, zinc-ion, lithium-sulfur, lithium-iodine, zinc-iodine, lithium-oxygen, zinc-oxygen, and lithium-carbon dioxide storage systems.

“Despite the respective significant progress in rechargeable batteries and photovoltaic techniques in the past decades, integrating different rechargeable batteries with solar energy in an effective and low-cost way remains a great challenge,” they said.

They divided the battery technologies into two categories: closed-type photo-enhanced rechargeable metal batteries and open-type photo-enhanced rechargeable metal batteries. They analyzed the advantages and disadvantages of each kind of battery.

As a general rule, photon-enhanced batteries with PV can provide better performance for low charge voltage and high energy density, which makes them suitable for smart electronics and optoelectronics. However, stability and safety should be improved to help such devices to reach commercial viability.

“For example, rechargeable lithium-ion batteries, which we are all familiar with because they are used in many modern electronic devices, including laptops, phones, and electric vehicles, are efficient, but would be difficult to scale for solar energy use because of their complicated structure,” they said.

The scientists noted the importance of standardizing experimental conditions and developing effective thermal management systems for stable operation.

“Standard experimental conditions conducive to the comparison of overall performance in different systems need to be established. For photo-enhanced rechargeable batteries, light illumination is indispensable,” they explained.

Thy introduced the battery technology in “Photo-enhanced rechargeable high-energy-density metal batteries for solar energy conversion and storage,” which was recently published in Nano Energy.

“It is necessary to explore more suitable electrode materials and optimize the device structure of the batteries,” said researcher Hairong Xue. “By addressing some critical challenges involving working mechanism, electrode materials, and battery structure design, the goal is to demonstrate viable uses of photo-enhanced rechargeable batteries in electronic and optoelectronic devices.”

Author: Emiliano Bellini

CEA-INES develops 18.95%-efficient flexible perovskite solar panels

Image: CEA-INES

French researchers have developed PV modules with an area of 11.6 square centimeters for indoor applications. They said the achieved efficiency level marks a world record for a flexible perovskite device larger than 10 square centimeters.

From pv magazine France

Researchers at France’s National Solar Energy Institute (INES) – a division of the French Alternative Energies and Atomic Energy Commission (CEA) – have developed new flexible perovskite solar modules.

They have a surface area of 11.6 square centimeters, with a maximum power conversion efficiency of 18.95% and a stabilized efficiency of more than 18.5%. INES said the performance is a world record for a flexible perovskite device larger than 10 square centimeters.

Currently, the power conversion efficiencies of solar devices based on perovskites indeed exceed 25% for single junctions and 29% in tandem structures with silicon. However, these results are obtained on small surfaces, of the order of 1 square centimeters.

To obtain this yield on larger surfaces, INES developed the flexible perovskite solar modules at low temperature on low-cost substrates made of polyethylene terephthalate (PET). They used a very simple structure featuring five layers, including the electrodes.

The performance is obtained after encapsulation and the stability of the devices has been tested under damp heat conditions at 85 C, according to the standards used for silicon-based technologies. A stability of several hundred hours has been obtained – between 400 and 800 hours, depending on encapsulation – based on a standard objective of 1,000 hours.

To achieve this result, the CEA optimized the stacking of the layers of the cell to implement a three-step laser process for the production of the module. It also developed a flexible encapsulation process that is fully compatible with high gas barrier materials, with no initial loss.

The CEA’s devices will be integrated into a demonstrator for building-integrated photovoltaic (BIPV) applications by Flexbrick (Es), a member of the European consortium. The modules will be interconnected to obtain high voltages and will be tested according to building standards. In addition, stability tests in real conditions are currently being carried out.

The Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) in Germany, a project partner, is testing the panels for indoor applications. The tests have already shown power conversion efficiencies of up to 24.5% at very low light (500 lux).

For some applications, the use of flexible substrates could be of interest for single-junction perovskite technology, because it could open the way to high-speed and low-temperature printing processes. It therefore becomes possible to use low-cost substrates unlike flexible inorganic technologies, such as CIGS, which require higher temperature processes and more expensive substrates.

Many teams around the world are trying to meet the challenges of making larger devices with sufficient stability for real-world applications. This is one of the tasks set by the partners of the European APOLO project.

Author: Gwénaëlle Deboutte

Longi unwraps reasons behind green hydrogen shift

Longi’s green power and green hydrogen plans will provide much-needed decarbonisation opportunities to heavy industries such as metals manufacturing. Image: Pixabay

In recent years, Longi has turned its attention to green hydrogen. Li Zhenguo, company founder and CEO, speaks with Vincent Shaw in Shanghai about the strategic shift and how coupling this technology with solar PV will be key to achieving carbon neutrality.

From pv magazine 05/2022

How does Longi view the relationship between hydrogen, solar and storage?

Longi firmly believes that green power and green hydrogen is the best solution to achieving carbon neutrality. Solar power (green electricity) fundamentally reduces carbon emissions in hydrogen production. And as an extended application of solar energy, hydrogen production can bring hundreds of gigawatt-level increments. In addition, green hydrogen is a new type of energy storage that can address intermittency issues. This is what we call the “green electricity – green hydrogen – green electricity” cycle.

Low-cost solar power is critical to the development of hydrogen. It takes around 50 kWh to produce 1 kg of hydrogen by electrolysis. If the cost of PV electricity drops to US$3.33 cents per kilowatt-hour, the total power cost for 1 kilogram of hydrogen will drop to around US$1.67. If the cost of PV electricity drops to 1.67 cents per kilowatt-hour, the total power cost for 1 kilogram of hydrogen would be around US$0.83, which means the cost of green hydrogen from electrolysis is even lower than the current cost of hydrogen produced from coal (grey hydrogen).

The world currently consumes about 80 million tons of hydrogen every year, and most of it is grey. For green hydrogen to account for 15% of consumption, it requires about 450 GW of PV installations to support it. That is why we say solar and hydrogen production are inextricably linked in terms of scale and cost.

As a solar company, entering the hydrogen industry requires a strategic change. How have you approached this?

In 2018, Longi began to conduct strategic research into the hydrogen value chain. On March 31, 2021, we established Longi Hydrogen Energy Technology Co., Ltd., and our first hydrogen energy equipment manufacturing plant in Wuxi, China. The first 1,000 Nm³/h alkaline water electrolyser was officially launched in October 2021, and so far, several more have been delivered to our customers and put into production. The production capacity of the Wuxi plant will reach 1.5 GW by the end of 2022 and is expected to reach 5 GW to 10 GW by 2025. The “green power and green hydrogen” solution fully covers synthetic methanol, synthetic ammonia, steel smelting, petroleum refining, and other industries that are in urgent need of decarbonisation. As a renewable energy industry leader, we will continue investing in R&D to increase efficiency and reduce the cost of both solar PV and hydrogen production. In addition, we have developed a five-year development strategy for the hydrogen business and are committed to accelerating the global transition to clean energy.

What are Longi’s strategic hydrogen plans?

Longi has launched its alkaline water electrolyser, which marks a significant milestone, and represents a key step towards becoming a world-leading hydrogen technology company. Our electrolyser can provide a hydrogen output of 1,000 Nm³/h and we have already provided a 4000 Nm³/h hydrogen production system for the world’s largest green hydrogen project. The service life of the equipment exceeds 200,000 hours. The distributed I/O control system realises automatic and unattended operation. We will continue to invest in R&D and innovation and push for the development of products based on our technical abilities.

What is the biggest challenge for the development of hydrogen and how can it be resolved?

Like other green energies, the development of green hydrogen is highly dependent on policy. Interest rates and carbon prices play critical roles in the cost of green hydrogen. We have made a simple calculation: If the technical cost is considered, the cost of green hydrogen is around US$1.17 to US$1.33 per kg, which is very close to or even lower than that of grey hydrogen. This calculation is very sensitive to interest rates. If the local interest is 5%, the cost of green hydrogen will grow to around US$3.33. Therefore, green hydrogen is financially competitive in countries with low-interest rates, like Europe and Japan; but there are still cost difficulties in China.

The second constraint is the carbon price. Compared to grey hydrogen, green hydrogen saves around 20 kg of carbon dioxide emissions per kilogram of hydrogen. Based on the present carbon price in Europe, which means an extra income of about US$1.33, it makes green hydrogen more cost competitive. Therefore, green hydrogen has an absolute economic advantage in regions such as the European Union with low-interest rates and high carbon prices. However, in China, the current carbon price from Shanghai Carbon Exchange is only around US$8.33 per metric ton, which means a compensation rate of around US$0.17/kg for green hydrogen. This is far from enough for the development of China’s green hydrogen.

What are the trends in green hydrogen pricing?

It is possible to realise US$0.25 per cubic meter on the production side. The cost rise in the PV industry in the past two years is temporary. I believe the cost of solar will continue to decline, and eventually, in many places, PV power will reach 3.33 cents or even lower per kilowatt-hour. In that case, the power cost for water electrolysis would be around US$0.15 per cubic meter, thus allowing hydrogen to achieve US$0.25 per cubic meter.

What are the main applications for green hydrogen?

We see a variety of industries that need hydrogen, and especially green hydrogen. For example, in petroleum refining, hydrogen is used as a feedstock, reagent, and energy source. Hydrotreating is one of the key links in the refining process, involving processes such as hydrogenation, hydrodesulfurisation, hydrodenitrogenation, and hydrodemetallisation. Gasoline and diesel hydrogenation, wax oil hydrogenation, and hydrocracking units also require a lot of hydrogen consumption. The global oil refining industry consumes 38 million tons of hydrogen every year, accounting for 33% of the global hydrogen demand. The International Energy Agency estimates that demand for hydrogen in the refining industry will continue to grow. Meanwhile, tighter standards for air pollutants will lead to an extra 7% increase in hydrogen use in refining.

Author: Vincent Shaw

Singapore’s water tech companies, research institutes make waves worldwide

Wateroam’s portable water filter technology has been exported to 38 countries, including Nepal, Malaysia and Indonesia. Image: Wateroam

SINGAPORE – Water tech innovations and infrastructure that have helped water-scarce Singapore meet its daily water demands are now making waves worldwide, bringing clean water and sanitation to communities around the globe.

The Republic is a leading global hydrohub with an ecosystem of more than 200 water companies and 25 water research centres spanning the entire water value chain, including water supply, used water management and stormwater management, such as flood protection measures, said national water agency PUB.

Some local companies have also been commercialising their solutions in other parts of the world.

Wateroam, a company founded in 2014, has developed portable water filters to deliver clean water to countries as part of emergency response and humanitarian relief for disaster-hit areas.

The technology, which is designed to be as simple as possible, has been exported to 38 countries, including Nepal, Malaysia and Indonesia.

Non-profit organisation Lien Foundation launched the Lien Environmental Fellowship in 2010 to equip Asian scientists and researchers from selected regional countries with the skills and resources needed to tackle challenges related to water and sanitation, as well as renewable energy projects in their home countries.

Successful applicants receive mentorship from the Nanyang Technological University’s Nanyang Environment and Water Research Institute (Newri), where they receive technical and financial support to transform their ideas into viable solutions.

A total of 18 projects have been administered in nine countries as at May this year.

Lien Foundation chief executive Lee Poh Wah told The Straits Times that each project has to be tailored to the unique challenges of each community and the solutions have to be long-term, sustainable ones that have garnered local support and engagement.

Recently, the Lien Environmental Fellowship programme embarked on a new project to sample the water quality of Kathmandu’s heavily polluted Bagmati River to determine the source and extent of the pollution.

There has been continuous dumping of solid waste, domestic sewage and industrial waste in the river.

Noting that plastic pollution in the water was immense, Newri executive director Shane Snyder said that a possible solution could involve a plastic upcycling technology, with plastic waste converted to diesel fuel to alleviate the high fuel costs that Nepal is currently experiencing.

He added that plastic waste – when left in water – can cause toxic chemicals to leach, which can be harmful for the human body.

Freelance climate change and senior watershed expert Madhukar Upadhya from Nepal, who was not involved in the project, said the idea was great, as it could provide jobs to those collecting plastic waste and incentivise households to save their plastic waste to sell it.

The Fellowship programme also saw some of Singapore’s best innovations – such as its membrane technology – benefit less-privileged communities.

For instance, Myanmar’s Mandalay city had extremely hard water – full of calcium content, as well as E. coli bacteria and other pathogens.

“We knew that the nanofiltration method (which is typically used to soften and disinfect water) would be the way to go – but there was no such system available,” said Professor Snyder.

However, local water tech company Century Water, picked up the intellectual property rights from NTU and the National University of Singapore – which also does water tech research – and installed a membrane nanofiltration system there at a low cost.

“The operations are still going strong, despite the coup there and even amid the Covid-19 pandemic,” he added.

Mr Lee said that having clean water is the very foundation for health and human development.

“Without clean water, no country could ever escape poverty… and just as Singapore has become a global water hub, we have also benefited from foreign investment during the early days. So this is our way of paying it forward.”

Author: Cheryl Tan

Agrivoltaics for broccoli, cabbage

Image: Chonnam National University

Scientists in South Korea have combined PV generation with vegetable farming and have found that solar array shading provides favorable results for crops such as broccoli and cabbage.

From pv magazine

A research team at Chonnam National University in South Korea has looked at how solar power generation could be combined with broccoli and cabbage cultivation. The team found that the shading provided by a PV facility could improve the quality of crops.

Broccoli and cabbage need to be grown in places that receive full sun, which means between six and eight hours of sunlight per day, or very light shade. A lack of sunlight could result in thin, leggy plants.

“Because of its low light saturation points, broccoli may be a suitable crop to maximize famer’s profits and energy security through an agrivoltaic system,” the scientists said. “However, to date, there is limited information on the performance of brassica crops in agrivoltaics.”

The scientists built their agrivoltaic system with bifacial modules at a height of 3.3 meters. They achieved an average power generation per day of 127 kWh during the testing period. They claimed that their approach demonstrated the technical and economic viability of the proposed agrivoltaic solution.

“We found that the taste and the quality of the broccoli were not lower than those of a reference field without the solar array,” they said. “We also found no significant change in functional ingredients and metabolites that affect taste.”

The PV installation caused a significant reduction in the light hitting the crops, which in turn resulted in an improvement of their color.

“The color of broccoli is an important property that goes beyond appearance quality and is involved in consumers’ desire to purchase,” the scientists said.

They said that presence of the PV system reduced the agricultural yield by around 20%, compared to the reference field without solar. However, they said that the income generated by the solar array could more than compensate for such losses.

“The annual economic benefit from solar power was 10.4 times more than the broccoli production benefits,” the scientists said. “Therefore, farmer benefits will increase as they are cultivated in agrivoltaics compared to open field.”

The researchers presented their findings in “Agrivoltaic Systems Enhance Farmers’ Profits through Broccoli Visual Quality and Electricity Production,” which was recently published in Agronomy.

“In terms of land use efficiency, agrivoltaic is a good means of producing energy and food in Korea, which is a highly mountainous area,” they said.

Author: Emiliano Bellini

RETC releases 2022 Module Index Report

Image: RETC

The Renewable Energy Test Center has released a new report on PV module performance.

From pv magazine USA

The Renewable Energy Test Center (RETC) has released its “2022 PV Module Index” (PVMI) report, highlighting module performance across a variety of lab tests, while also providing industry-cited clarifications on the real-world significance of the results.

The 2022 PVMI marks the first edition released since VDE acquired a 70% stake in RECT. President and CEO Cherif Kedir said the move will allow RETC to expand its testing services to a broader network of manufacturers, investors, insurers and developers, all in pursuit of minimizing risk and uncertainty in favor of long-term reliability, sustainability and profitability by designing better data-driven risk mitigation programs and service products.

RETC Vice President of Business Development Daniel Chang told pv magazine the 2022 PVMI takes a more forward-looking approach than previous editions, supplementing testing results and hardware performance with emerging industry trends that are going to guide the use of this hardware and investments in projects that utilize it into 2023 and beyond.

Cherif Kedir, President and CEO of RETC

“We focus on what we think are going to be topics that are going to be relevant for the upcoming year, like the onset of N-Type modules, and field services,” explained Chang. “There are a lot of installations out there degrading at a faster pace than expected. These installations are investments in assets made by banks to yield some sort of financial benefit to them, right? If they have some sort of degradation, then that’s not performing the way that was expected and planned for.”

Specifically, RETC is interested in forensic analysis of PV systems to determine the root causes of underperformance. This investigation is the culmination of different analyses to be done over the life of a project, starting with a baseline third-party module health assessment during project commissioning.

In instances of underperformance, RETC recommends Electroluminescence (EL) testing. EL testing uses a special camera system to document the light emissions that occur when an electrical current passes through PV cells. The technology has long been used in labs to detect a wide range of hidden module defects.

Another aspect of forensic analysis is predictive maintenance, wherein a third party inspects plants from periodically to detect issues that may not be visible at a base overview, but could develop into much larger issues if allowed to linger.

While Chang brought to light the ongoing issue of degradation and the developing need for advanced field services, Kedir focused more on the technology side, researching where the next wave of module innovation will come in a post-large-format world.

Panasonic Heterojunction with Intrinsic Thin Layer (HIT) solar cell

That innovation, he thinks, will come from heterojunction n-type modules (HJT).

“I think leading manufacturers are kind of a crossroad point right now, in terms of how to get more power out of modules without making the modules just unreasonably large, because they’re already pretty damn big,” Kedir said. “The other reason I think manufacturers may be hesitant to make their modules larger is that everybody is testing the waters with heterojunction cells, so that they can eke out more more watts per module, without having to increase the size. With the module technologies they currently have, I don’t think they’re able to get a lot more efficiency out of the cell, so they’re trying to figure out how to get more power without increasing the module size, and the next, the next logical thing is to go to different technologies, Topcon and heterojunction.”

In an op-ed for pv magazine in November 2021, Nadeem Haque – chief technology officer at Heliene – outlined some of the distinct technology advantages that HJT presents. HJT cell manufacturing involves the deposition of an amorphous layer of silicon on both the top and bottom of the wafer followed by a transparent conducting oxide deposition and making of metal contacts.

HJT cell production lines are currently expensive, almost prohibitively so, and new lines need to be built. The cells require a more expensive metallization paste to manufacture. HJT cells are by nature bifacial, with bifaciality rates above 90%, the highest of any cell technology. Higher bifaciality and lower temperature coefficients result in higher energy output, and HJT cells in mass production are expected to reach about 27% efficiency.

“You can gauge where the industry is going based on where investment money is going, and we hear a lot about companies investing money in heterojunction cell lines in Asia, so I think that’s probably going to be a trend,” said Kedir.

The last industry trend examined by RETC is mitigating the effects of extreme weather on PV systems, a topic which pv magazine has reported on extensively with RETC and other partners, like VDE Americas.

Module index

The core of the report is a review of modules’ performance across a range of tests that are designed to go beyond the parameters of tests for certification and accurately project what each module’s strengths are, rather than compare and rank them against one another.

The tests are split up into three categories, each of which analyzes a different aspect of module excellence: quality indicators, performance indicators, and reliability indicators. In testing, the researchers at RETC noticed a new trend that some of the performance and reliability gaps from manufacturer to manufacturer have widened, as opposed to the narrowing they observed in recent years.

“Some of the issues that we saw over the last year have been related to manufacturers faced with their own supply chain issues and inability to get their raw materials,” explained Kedir. “They’ve had to go to other sources, secondary and tertiary sources of cells and backsheets, and then that triggered a few failures, we saw more of them last year. What’s been lingering is potential-induced degradation (PID) and some related performance stuff. On cells, PID, for all intents and purposes, had been completely solved a few years ago, but then it reappeared throughout the pandemic, with the supply chain issues, we see some of that leftover.”

This is a phenomenon that Kedir expects to see continue, at least in the short term. The issue may linger as a result of the recently-announced two year moratorium on the DOC’s anticircumvention case, he said.

“Demand is going to is going to pick up in the US,” he began. “The upcoming traceability requirements are going to put a constraint on the cell supply from forced labor regions, which means you’re not going to have enough cell supply for them for the market demands. This causes supply separation between manufacturers. Some larger manufacturers have already completely mitigated that issue, developed a new supply chain for polycrystal, and have new cell lines in Southeast Asia. Those guys are going to fare out much better than a manufacturer who hasn’t put in that infrastructure already. They’re going to have to try to source cells from other places or other manufacturers that may or may not be as good as their initial supply.”

While the gap between top-tier, established module manufacturers and some newer market entrants is widening, RETC still had a number of manufacturers perform well across their litany of tests.

Based on available testing data, RETC highlighted Hanwha Q CELLS, JA Solar, and LONGi Solar as the overall top three performers of the year. The recognition does not stop with the top performers, however, and RETC listed some of the manufacturers who scored the highest marks in individual tests, listed below.

Hail durability:

  • LONGi Solar

Thresher test:

  • Hanwha Q CELLS
  • JA Solar
  • LONGi Solar
  • Tesla

LeTID resistance:

  • Hanwha Q CELLS
  • Jinko Solar
  • LONGi Solar
  • Trina Solar

LID resistance:

  • Hanwha Q CELLS
  • JA Solar
  • Jinko Solar
  • LONGi Solar
  • Trina Solar

Module efficiency:

  • JA Solar
  • LONGi Solar
  • REC Solar
  • Silfab Solar
  • Tesla
  • Yingli Solar

Pan file performance:

  • JA Solar
  • Jinko Solar
  • LONGi Solar
  • Trina Solar

PTC-to-STC ratio

  • Hanwha Q CELLS
  • JA Solar
  • REC Solar
  • Silfab Solar
  • Tesla
  • Yingli Solar

Damp heat test

  • JA Solar
  • LONGi Solar
  • Hanwha Q CELLS
  • Tesla

Dynamic mechanical load test:

  • JA Solar
  • Jinko Solar
  • LONGi Solar

PID resistance:

  • JA Solar
  • Jinko Solar
  • LONGi Solar

Thermal cycle test:

  • Hanwha Q CELLS
  • JA Solar
  • Jinko Solar
  • LONGi Solar
  • Tesla

RETC said the rankings are comprehensive only to data that the company has collected, so modules from other manufacturers could perform similarly to the ones listed above, but the organization cannot make an overall determination regarding high achievement in manufacturing without module tests data across the three categories.

The report concludes with a look at a number of notable changes and revisions anticipated in the upcoming edition of IEC 61730, a two-part standard pertaining to PV module safety qualification, as well as upcoming updates to IEC TS 62915, a technical specification pertaining to PV module approval, design and safety qualification.

The standards analysis is expansive, and pv magazine will cover these pending changes in a follow-up to this article.

Author: Tim Sylvia