From pv magazine 05/24

On Jan. 31, 2024, researchers from the Fraunhofer Institute for Solar Energy Systems (Fraunhofer ISE) announced that, alongside perovskite developer Oxford PV, they had produced a full-sized perovskite tandem module with a conversion efficiency of 25%. At 421 W, the dual-glass module’s power output is far from that achieved by the large-format modules manufactured by solar industry giants. Nonetheless, the result was a powerful demonstration of the steps being made toward commercializing what is widely considered the next generation of solar cell technology.

When announcing the result, the Fraunhofer ISE team noted that scientists from its CalLab PV Modules’ calibration laboratory used a “multispectral solar simulator” to measure both the crystalline silicon solar cell and perovskite cells. It allowed for different light spectra to be applied to the cell while under continuous illumination. This required specialized measurement equipment based on LED light sources that were able to provide illumination evenly across the module’s 1.68 m² surface.

“The continuous intensity and spectral stability of the light source is of particular importance especially for tandem devices,” said Johnson Wong, general manager for the Americas at equipment provider Wavelabs. The researchers from Fraunhofer ISE used Wavelabs’ Sinus-3000 Advanced LED module I-V tester for the Oxford PV module.

“Thanks to its optimized light distribution over a long working distance, the tester light source is designed to cast a light field that very closely mimics the sun at every point over the large module area,” Wong added. He said the Sinus-3000 LED tester exceeds A+ class in terms of “spectrum, light uniformity, and stability over time, which play a critical role in the measurement accuracy.”

Accurate characterization

The accurate characterization of perovskite solar devices requires not only new equipment but also novel processes. Longer illumination times are needed; the temperature impact of the light source must be controlled or corrected for; I-V sweeps should be significantly slower than in crystalline silicon cells; and, in tandem cells, their current must be aligned so that the combined power output is not limited.

The PV research community, prospective manufacturers, and equipment suppliers are making strides in overcoming the formidable challenges posed by perovskite solar devices. New, collaborative research projects are being launched and measurement routines are becoming more sophisticated. As a result, confidence is growing that as the prospective PV perovskite manufacturers develop their devices toward maturity, the equipment and processes will be ready.

Sunny prospects

Karl Melkonyan, PV technology analyst with S&P Global Commodity Insights, said that perovskite tandems have “the best chances for commercialization” among next-generation solar cell technologies. Perovskite PV cells can be coupled with either crystalline silicon (c-Si) or thin-film solar cells.

Early perovskite PV devices achieved conversion efficiencies in the low single digits – 3.8% was recorded in 2008. Record efficiencies are now set at regular intervals and are well beyond 25%.

Perovskite tandem devices are extremely promising, primarily because the thin-film perovskite cell plus the “base” c-Si, cadmium telluride, or copper indium gallium selenide layer can capture different light wavelengths, resulting in small-scale research cells with efficiencies beyond 30%.

Translating lab efficiency to larger cells and modules is difficult, however. “While there are many record efficiency achievements of perovskite solar cells reaching 20% and above, the total efficiency of a tandem structure can be much lower than the sum of those individual efficiencies,” said Melkonyan. He noted that the reason for this is often a current mismatch between bottom and top cells.

Measurement challenges

For a PV device to prove its worth, its power output must be able to be measured in a highly accurate, replicable, and standardized fashion. At the end of the day, if a PV module is to be purchased and installed, it is vital that its nameplate power output can be trusted.

Here, as noted in the recent Fraunhofer ISE and Oxford PV result, perovskite PV devices present a host of new challenges. “Yes, the power measurement of a perovskite tandem or multi-junction cell presents challenges and could be quite difficult because very specific spectrally-adjustable solar simulators are required,” said Melkonyan. “Apart from appropriate stabilization methods for different perovskite materials, the processes should include standardized protocols to measure under standard test conditions.”

In late April 2024, Fraunhofer ISE, Oxford PV, Wavelabs, and the University of Freiburg wound up an 11-month investigation into how large-format perovskite tandem PV cells can be accurately characterized. Fraunhofer ISE’s Martin Schubert led the project – abbreviated to “Katana” in German. He said there are two major differences between the characterization of perovskite tandem devices and regular PV modules.

Two factors

“One is that the efficiency may change during illumination,” said Schubert, who leads the quality assurance, characterization and simulation team. “The reason for that is that there is an ion migration in the perovskite cell in which some ions are moving. The second complication is the tandem architecture. By itself, that means we have two solar cells – one on top of the other and with different spectral sensitivity. We need to take care that the top cell gets the right amount of current and the bottom cell gets the right amount of current.”

Ion migration within the perovskite device while under continuous illumination means that the measured efficiency can either increase or decrease over time. This “metastability” necessitates the long illumination time needed for stabilized power output to be ascertained. Complicating things further, different perovskite PV compositions demonstrate varying levels of metastability.

The need for long light exposure, to accommodate metastability, brings heat, even when using LEDs. This means that the measurement of perovskite devices is often carried out at temperatures higher than standard test conditions (STC).

The power output of a photovoltaic device declines as its temperature increases, a factor described as a device’s temperature coefficient. Different PV technologies mean differing temperature coefficients. c-Si solar products, for example, have a larger temperature coefficient than thin film devices. If that is not controlled and accounted for, the result is measurement uncertainty.

Testing equipment with temperature control – essentially a chamber with air conditioning – can reduce this uncertainty in best-case scenarios. Such sophisticated devices, particularly with sufficient scale to accommodate full modules, come at a cost.

The impact of temperature can be corrected for using mathematical models based on accurate temperature readings and can account for the uncertainty higher temperatures can bring. With tandem devices, the temperature sensitivity of both the top and bottom cell must be accounted for – a complex, if not impossible, equation.

Commercial implications

At present, the testing of perovskite devices is carried out within minutes, to account for metastability related to ion migration in the perovskite cell, so that slower I-V sweeps, with multiple power point tracking (MPPT), can be carried out. This is unsuitable for mass production, as many modules need to be rolling off production lines every minute.

Wavelabs’ Wong said that a “more pragmatic test routine” would likely first involve a preconditioning of the module using light soaking, from mass-production light sources. That could then be followed by “a fast I-V sweep using high quality illumination that must fit within the specifications of spectral match, uniformity, and stability,” said Wong. “The fast I-V sweep will likely be done in the order of 100 milliseconds to one second, during which the ions are ‘frozen in’ to their preconditioned distribution and do not significantly redistribute.”

Fraunhofer ISE will be launching a three-year research project in May 2024 that will investigate how “fast and precise measurements” can be developed and executed for perovskite devices, including tandems. The project, abbreviated to “PERLE” in German, will be funded by Germany’s Federal Ministry of Economic Affairs and Climate Action. Fraunhofer ISE’s Schubert said that it is possible that the first findings from the project will be published by May 2025.

From pv magazine Australia

With an eye to local job creation, shorter supply chains, and reduced carbon emissions from transportation, Nextracker is continuing to use locally produced steel for some major projects. The latest in the strategy is the 480 MW Aldoga Solar Farm in Queensland, which will use Bluescop steel torque tubes, produced in Brisbane.

Nextracker announced the deal at an event in Brisbane on Thursday, March. 15. The event was attended by local politicians, steel industry representatives, and Nextracker management.

The local supply deal involves Nextracker, Orrcon Steel, Bluescope, and Baojia.  It involves “critical steel components” being produced at the BlueScope steel coil at Orrcon Steel’s Salisbury Tube millin Brisbane. The toirque tubes will then be finished by Baojia – which works with Nextracker on a global basis.

The supply deal will underpin a decision to open a new steel manufacturing line. It will be equiped to produce 50,000 tonnes of torque tubes a year – a PV capacity of 2.5 GW.

“This foundation strengthens Nextracker’s commitment to deliver energy security to Australians with a local supply chain and new manufacturing jobs to make clean energy affordable and accessible. We support Queensland’s Energy and Jobs Plan and applaud their ambitions to create jobs for the clean energy economy,” said Peter Wheale, Nextracker GM for Australia, Southeast Asia, and New Zealand.

Thursday’s opening ceremony was attended by the Queensland Minister for Energy Mike de Brenni; Tania Archibald, Chief Executive BlueScope Australian Steel Products; Tony Schreiber, Chair of the Australian Steel Institute and General Manager of Orrcon Steel and Peter Wheale, General Manager of Nextracker Australia, Southeast Asia, New Zealand.

Rival tracker supplier Array Technologies announced in February that it would establish a manufacturing line in Australia. The decision was made on the back of project supply wins, including the 102 MW Glenrowan Solar Farm.

In announcing the supply deal, Nextracker pointed to Rystad Energy research that showed that the US tracker company had supplied 7.45 GW of projects in Australia – of a total fleet of 13.5 GW, making it the market leader. Other major projects Nextracker has supplied in Australia are the New England Solar Farm (521 MWd), Stubbo Solar Farm (520 MWd) and Western Downs (460 MWd).

From pv magazine print edition 3/24

The annual SNEC solar exhibition in Shanghai is an exhausting affair. On his return from the 2015 event, seasoned energy storage analyst Sam Wilkinson took a call from a journalist at The Times newspaper. A drained Wilkinson provided what proved to be front-page analysis.

The United Kingdom-based title was after Wilkinson’s take on the new Tesla Powerwall, the American EV maker’s residential battery. The product had been revealed by Elon Musk, with trademark chutzpah, on social media.

“I was literally in a taxi on the way home from Heathrow Airport and the next day I got a call that somehow the story had made the front page,” said Wilkinson, a director of clean energy technology at S&P Global Commodity Insight.

“It showed that there was this level of interest in the idea of energy storage. At the time it was a very nascent, niche, techy thing to do – to have a battery in your house. Fast forward, eight or nine years and it has become a very well understood, common thing.”

The Times was not alone in its enthusiasm for the Powerwall. “Sleek, chic, and unmistakably touched by that Elon Musk magic,” enthused pv magazine when featuring the first iteration of the Tesla Powerwall on its June 2015 cover (see left). The battery came at a price point far below rival products. Musk said the 10 kWh Powerwall would retail for $3,500, with the 7 kWh model going for $3,000.

“At the time I noted the price of Tesla batteries was significantly cheaper than what we’ve seen in the market, which would bring competition among other suppliers and push prices down,” said Wilkinson. “Which turned out to be relatively true, in the end.” By setting such an aggressively low price, Tesla blew open a previously nascent market segment.

Next generation

At the time, Tesla embodied the cutting edge in EVs and uber-geek cool. Powerwall 3, launched in 2024, will be the most powerful iteration – offering backup power even to large homes. It became available to installers in the United States on Feb. 16, with the move announced on X (formerly known as Twitter), Musk’s social media platform.

The Powerwall 3 was unveiled in Las Vegas at the RE+ trade show, on Sept. 12, 2023. While it has the same storage capacity as the Powerwall 2 – 13.5 kWh – a key differentiator is that it can provide more than 50% more power, at 11.5 kW of continuous power. It is a hybrid battery with the solar and battery inverter fully integrated.

At RE+, Tesla engineers highlighted that the Powerwall 3 offers installers quicker installation through a series of innovations. The new battery is smaller and lighter, albeit slightly deeper. It is 110 cm long, 61 cm wide, and 19.3 cm deep and its inverter, battery cells, and battery management system weigh in at 130 kg.

To lighten the load, Tesla has also worked with partners to develop a “dolly” – to help installers to lift the hybrid battery up and onto walls for mounting. That may seem like a minor detail but, crucially, it allows a single installer to fix the battery in place.

At $11,500, the Powerwall 3 is not looking to shake up the residential market based on price, as its predecessor did. However, the Tesla team at RE+ were keen to impress that quicker installation will enable installers to carry out more jobs, bringing down their labor costs.

Integrated system

Tesla’s in-house engineers developed the solar inverter inside the Powerwall 3 – displaying the company’s growing technical proficiency. The product deploys six maximum power point trackers (MPPTs), to optimize rooftop PV output.

“That has been an evolution of the [energy storage] space in general,” said Wilkinson. “We call them ‘integrated systems,’ with batteries and inverters combined together. The integrated product is obviously looking to provide a lot of other functionality and slightly more futuristic things, like VPPs [virtual power plants] and systems that can respond to things like electricity prices.”

The integrated approach precludes retrofit applications in homes with existing rooftop arrays, which Tesla says it will continue to serve with the Powerwall 2.

“It is all about the Tesla brand and they have that unique position of being the place you can go to get solar, storage, and an EV – and no-one else offers that full ecosystem,” said Wilkinson.

In the United States, Tesla is planning to sell the Powerwall 3 in a bespoke offering for homeowners. The company’s sales team provides integrated solar-plus-storage quotes based on a home’s size and power consumption. For even larger homes, up to four Powerwalls can be installed in series, offering a whopping 40 kW of power.

“It is not completely unheard of to have three or four Powerwalls, in the States,” Wilkinson said. “It is not an economic decision, it is purely a backup power play. And people will pay for backup in the US because grid outages are relatively common, compared to Europe.”

Thunder Down Under

Sydney-based PV and battery retailer Natural Solar sold the world’s first Powerwall in January 2016. The company’s founder, Chris Williams, said that while the first Powerwall was largely for early adopters, the Powerwall 2 opened up more of a mass market, with some 500,000 units sold globally. He said the latest version represents the next phase of the product’s evolution – which he described as an “interesting and exciting” one.

“It is tackling a new market as a solar inverter and a battery,” said Williams. “Having that all in one ecosystem, with data flowing from the Tesla app – and you can add an EV charger – I think is the next stage of ecosystem, from a customer perspective.”

Australia is a significant market for Tesla, for its utility scale and distributed batteries and its EVs and chargers. With a vast and growing rooftop solar fleet, and power outages increasingly common as a result of extreme weather events, there is a growing appreciation of backup power provision through residential solar-plus-storage.

Around 600,000 homes in the state of Victoria lost power on Feb. 13, some for days, after a storm downed a major transmission line.

EUPD Research monitors EV charging and solar-plus-storage installers in Australia and Europe. EUPD analyst Finn Bee said that the Tesla residential EV charger has consistently had the highest installer satisfaction rating of any brand. When it comes to batteries in Europe, however, there is more of a mixed picture.

“Our installer monitor, for which we survey more than 1,600 installers in selected markets across Europe and Australia, shows that Tesla has lost some market penetration but is still one of the best-known brands in many countries,” said Bee. “They are doing particularly well in Australia and Italy, two of the strongest markets for storage but are lagging in Germany, for example.”

Future outlook

While Tesla helped to create the residential energy storage market segment in 2015, the dynamic in 2024 is one of oversupply. The residential segment in the United States is depressed on the back of net metering reforms in key solar states. In Europe, inventories remain high.

“The market has cooled off in 2023,” said Wilkinson. “We’ve now got a pretty grim situation, especially in Europe. Every company, especially the newer Chinese entrants, was shipping, into Europe, crazy volumes when the energy-crisis boom was under way.”

S&P Global forecasts incremental residential energy storage growth in the coming years, with slightly more than 17 GWh of installations expected globally in 2024.

From pv magazine 02/24

While certain solar production steps are measured in nanometers, atomic layers, and fractions of a percentage or cent, ingot and wafer production more closely resembles heavy industry. Gleaming crystalline silicon ingots emerge from towering pullers to be sliced by diamond wire saws into iridescent, black square, or rectangular, monocrystalline wafers.

The ingot and wafering production steps are power hungry and produce waste in the form of kerf slurry – the residue ingot material from between the sliced wafers. Those are the PV production steps most highly concentrated in China.

Jessica Jin is the principal research analyst for solar and clean energy technology at S&P Global Commodity Insights Shanghai. Jin reported that in 2023, China accounted for 96% of global ingot and wafer production. She added that the wholesale switch within PV manufacturing from multicrystalline to monocrystalline technology, in and around 2018, was decisive for China’s dominance of the production step. That dominance has extended upstream.

“This was led by Longi, as everyone knows,” she said. “Since then, Chinese equipment manufacturers working with Longi keep improving their technology and also add capacity and they all grow up with the market expansion in China.”

The development is one that is common throughout China’s solar success story. Through aggressive scaling and close cooperation with technology and material suppliers, Chinese manufacturers have been able to rapidly adapt new technology and production processes, outcompeting European and American rivals first on cost, and then on performance and efficiency.

“Nowadays, we see most of these equipment suppliers are also in China as well,” said Jin. The result being that in 2024 there are few credible pathways for non-Chinese manufacturers interested in developing ingot and wafer capacity.

European setbacks

PV manufacturing advisory Exawatt, now a part of CRU Group, finds that the only notable ingot and wafer production hub outside of China is in South East Asia. Exawatt tallied some 35 GW of wafer facilities in operation in South East Asia by the end of 2023, with that potentially expanding to 45 GW by the end of 2024.

While expansions are under way in South East Asia, the opposite is the case in Europe. The year 2023 saw both Norsun and Norwegian Crystal suspend or wind up their operations in Europe – effectively reducing wafer production in Europe to zero. Those decisions were followed shortly after by that of, presumably, a key supplier. Polysilicon producer REC Solar Norway began winding up its operations in Kristiansand, Norway – which had an annual output of 8,000 tons – and in Heroya, Norway – with 5,500 tons – in November 2023.

Norwegian Crystal had closed its 500 MW ingot facility in Glomfjord, Norway, a month earlier. As recently as 2022, it had been pursuing plans to develop a 6 GW ingot and wafer facility but had been unable to secure funding, forcing it to begin liquidation of the company.

In September, compatriot Norsun announced layoffs and a production halt at its 1 GW facility in Årdal, Norway. Tellingly, Norsun is now trying to establish a 5 GW ingot and wafer production facility in the United States. In August 2023, it announced it had raised NOK90 million ($8.5 million) in capital in pursuit of the plan, alongside the €53.6 million ($58 million) it was awarded by the European Union Innovation Fund.

Potential in United States

Subsidies are available for solar manufacturers in Europe but they pale in comparison to what is on offer in the United States. In the first 12 months after the US Inflation Reduction Act (IRA) was signed into law, announcements were made totaling 155 GW of annual solar manufacturing capacity, right across the value chain, according to trade body the Solar Energy Industries Association. However, few were for ingot and wafer production.

“According to our model, the incentive is actually very good for production in the United States,” said S&P Global’s Jin. “But it’s not simply about the production cost but also other costs, like the recycling, construction cost, and so on.”

Jin said that securing environmental approvals for wafer operations may prove difficult outside of China. Although she did note that in the past five years, many of the waste and recycling issues from wafer production have been addressed.

South Korean module maker Qcells stands out as an exception. In January 2024, Qcells announced a $2.5 billion investment decision which included 3.3 GW of annual ingot, wafer, and cell production capacity, to be executed in stages. The manufacturing will involve the establishment of a new production base, in Cartersville, Georgia – outside of the city of Atlanta in the United States. It follows the expansion of Qcells’ module assembly operations, to 5.1 GW capacity, in Dalton, Georgia, in the United States, completed in October 2023.

Supply deal

In January 2024, Qcells announced it had expanded an existing 2.5 GW module supply and engineering, procurement, and construction services deal with Microsoft to 12 GW of supply over eight years. The companies say the projects covered by the deal will be supplied by Qcells’ “fully integrated solar supply chain factory in Cartersville,” to the tune of 1.5 GW per year through 2032.

The deal provides offtake certainty to Qcells, with one-third of its ingot and wafer output accounted for in cooperation with a bankable counterparty. For its part, by working with Qcells in this way, Microsoft hopes to accelerate its renewable energy deployment by locking in supply and driving large-scale domestic production of solar modules in the process.

“There is always something that makes supply to the US uncertain,” said Alex Barrows, head of PV at Exawatt. “I can see an appeal to locking in something that gives you some certainty – even if you’re paying a premium.” PV module prices are higher in the United States and there remains a complex web of tariffs, exemptions, border seizures, moratoria, and legal challenges, all of which can delay final project realization or blow out costs.

Barrows noted that Qcells’ parent company, Hanwha, is South Korean rather than Chinese. It has access to American polysilicon from REC Silicon and is on the way to becoming a vertically integrated United States producer – making it well placed to offer stability in the face of potential policy turmoil or geopolitical shocks. “I feel like it is a pretty good way to lock in some security,” said Barrows.

Yet despite the IRA, higher prices, and advantages for locally produced products, Barrows remains skeptical of the prospects of many announced ingot and wafer facilities in the United States. Alongside Qcells and Norsun; Convalt Energy, CubicPV, and India’s Vikram Solar have announced American manufacturing plans that extend up the supply chain to ingots and wafers.

“I think we’ll get a bit [of ingot and wafer capacity] in the US but nowhere near what has been announced,” said Barrows. “Thirty-five GW of capacity by the end of 2026 has been announced but I would actually suspect it is more likely that 15 GW to 20 GW will be installed.”

Kerfless promise

On the list of aspiring manufacturers, CubicPV stands out. Not only has it announced its intention to develop 10 GW of traditional ingot and wafer technology, it is also a proponent of “direct wafer” usage. The company’s chief executive officer (CEO), Frank van Mierlo, formerly led 1366 Technologies. That business had attempted to commercialize “direct wafer” technology by producing multicrystalline solar wafers from a liquid, rather than cleft from a monocrystalline ingot.

Qcells worked in partnership with 1366 Technologies and achieved notable conversion efficiency achievements with the latter’s technology, including cells with more than 20% efficiency. However, when the PV industry switched to monocrystalline technology, 1366’s wafers were left stranded on the wrong side of development.

Germany’s NexWafe is pursuing a wafer technology not dissimilar to that used by 1366. The NexWafe approach is described as epitaxial and involves gases being deposited onto a seed substrate from which it can be separated and fashioned into a cell. Both approaches can be described as “kerfless” wafer production as they do away with wafer cutting and the waste kerf it produces.

In October 2023, NexWafe broke ground at a 250 MW factory in Germany where it will invest at least €70 million. Interestingly, NexWafe CEO Davor Sutija was the former president and CEO of SiNor, which eventually became Norwegian Crystals.

Production alternatives to the mature Czochralski process for monocrystalline ingot pulling and diamond wire sawing must overcome capital expenditure, throughput and efficiency challenges to become commercially viable. High cell efficiencies on epitaxial or direct wafer technology have not yet been reached, nor has competitive throughput from a factory at scale.

The establishment of any new ingot and wafer capacity with any technology will also take place under intense cost competition. The year 2023 saw module prices decline by more than 30% on global markets and there is a glut of product on the market. “We’re definitely expecting a wash in the industry next year,” said S&P Global’s Jin.

Yet, in times of bankruptcies and consolidation, there are opportunities for “step change” or next-generation technologies. European or United States companies may prosper while oversupply grips their Chinese rivals. NexWafe and CubicPV are pursuing new approaches to wafer production despite manufacturing-segment adversity.

In November 2023, NexWafe appointed Rick Schwerdtfeger as chief technology officer and André Seemaier as chief financial officer as the company moves into the commercialization phase of its gas-to-wafer technology.