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Solar PV innovations: Crystalline silicon roundup


Joyce Laird

Most surveys conclude that crystalline-silicon PV (C-Si PV) still holds the greatest market share of all solar installations. But with other technologies now ramping up, what are C-Si companies doing to maintain that lead and perhaps even expand on this? Joyce Laird talks to some of the players active in this technology area.

Originally spun off from Suntech, in 2007 Aide Solar became a member of the PANJIT Group family of companies (Kaohsiung, Taiwan). With backing from PANJIT, Aide began to grow and expand capacity to bring it to a stronger, more aggressive supplier position in the market.

“For the market in general the push is to improve efficiency both on the cell and the module level. There is still a huge drive to improving efficiency because that is where you will see the system cost per watt going down on the installation side,” Raumond Wiley, Director Aide Solar USA, says.

Many analysts agree with this sentiment, and it is something that goes to the heart of innovation in solar PV technologies. For a number of years, thin-film technologies gained ground on their c-Si counterparts because the cost of manufacturing them was cheaper – they weren't confined to using silicon in its crystal form, inherently more expensive than amorphous silicon or other semiconductor materials.

But as the cost of c-Si has fallen in recent years due to well-documented market factors (and an availability of more silicon), c-Si has recaptured some of its lost ground. Why? Because c-Si has better efficiencies and is therefore cheaper to install. Some believe that when prices for crystalline technologies fall, prices for thin-films must fall by at least 12%. This is because higher efficiency technologies are cheaper to install (the area penalty affects balance of system, land costs and installation time). Similarly, technologies with less than 10% conversion efficiency are non-competitive in grid-connected applications. All of which has put c-Si proponents in good voice.

BioSolar Inc however, based in Santa Clarita, CA, USA has spent the last four years perfecting a technology that all PV manufacturers could benefit from. “Today, petroleum-based plastics are used in the production of virtually all solar panels. With material cost rising and the fact that these materials are not environmentally neutral, we developed a solution that ends dependency on petroleum-based products,” David Lee, Ph.D., President and CEO says.

Canadian Solar Inc. (Ontario, Canada) is a leading vertically integrated solar PV provider. “We are up to a global 1 GW of productive capacity, which puts us into very exclusive company,” Mike Miskovsky, General Manager, US Operations, says

Based in Marlboro, MA, USA, Evergreen Solar is also a vertically integrated c-Si solar PV manufacturer. “How we accomplish the progression from raw material to final panels is what makes us unique,” Chris Lawson, Director of Marketing Communications, says.

Sharp is invested in both sides of the solar PV industry with their products for both the c-Si PV and TFPV markets. Paul Wormser, Senior Director of Engineering for Sharp Solar Energy Solutions Group based in Huntington Beach, CA, says: “At Sharp, we consider ourselves a PV company, not specifically a crystalline or a thin-film company.”

Some analysts believe that when prices for crystalline technologies fall, prices for thin-films must fall by at least 12%.
 

Headquartered in Osaka, Japan, SANYO also has a very prominent position in the USA through their Sanyo Energy Division. The Panasonic acquisition of the greater amount of the shares of SANYO at the end of 2009 has started rumors of the billions dollars that will be invested into the solar operations to double SANYO's capacity to 600 MW.

“There is no timeline for this yet. It will be a methodical and calculated process that will probably take well into next year,” Asa Such, Account Manager, SANYO Energy (USA) Corporation, says.

Only 7 years old, Solaria (Fremont, CA, USA) spent its first year only in product development. The technology was commercialised in 2009 and ramped up to high volume manufacturing in 2010.

“Our technology is basically an optically enhanced low concentration c-SiPV module,” Daniel Shugar, CEO says. “The common denominator behind all crystalline modules is that irrespective of the manufacturer the cell size accounts for about 75% of the cost of manufacturing the product. If you can reduce the amount of the solar cells that are within each panel, you can dramatically reduce the cost of the product. So we set out to make a product that would accomplish that.”

SOLON (Berlin, Germany) creates solar panels utilising the best components on the market. “We work with different suppliers to get the best end modules, to reduce cell degradation, enhance energy harvest and maximise the efficiency the cells bring once they are actually in the module,” Daniel Alcombright, Regional Vice President, North America says. “We work with academia, universities and partner with them on very unique advances. Because we are not cell providers we can concentrate on the whole system and the kilowatt hours that we pull out of the system.”

With headquarters in Jiangsu Province, People's Republic of China, Suntech Power is coming up on 10 years in the industry and is arguably one of the largest producers of crystalline silicon solar PV in the world.

Andrew Beebe, VP of Global Product Strategy for Suntech notes that today the markets are so big, all large solar panel manufacturers are tailoring panels for specific market applications for a better fit.

Upsolar is a China-based module supplier and we are unique because we have adopted the semiconductor manufacturing model,” Troy Dalbey, North American Sales Manager, Upsolar America Inc. says.

“We outsource manufacturing but we also personally supervise all of our modules and all of our manufacturing done at contract facilities. We hired Bureau Veritas to verify the quality control of all of our modules. Everything that is shipped out has been audited by them and stamped as verified for quality of delivery.”

Leading edge technology

What makes Aide Solar different from other manufacturers is that it is very heavily entrenched in the semiconductor method of operation. “The advantage that we have is when we started up our new facility, we were able to leverage the knowledge that exists within the PANJIT Group on the semiconductor side to help us bring our PV cell production line up. You could call it a cross-pollination of technologies,” Wiley says.

Wiley says that prior to this they were buying high-efficiency monocrystalline cells on the open market, but the highest efficiency specification they were able to find and purchase was around 17%. “After implementing our own cell technology, in only two months, we improved the efficiency of our cells by a whole percent or better and therefore, the efficiency of our modules because of the knowledge base we had coming from the semiconductor side.”

“Our facility is one of the few PV manufacturing facilities where clean room practices are in place. Our factory is a class 1000 clean room with the equipment usually having a Hepa filter and under hood cleanliness of class 100. We have air showers. We have people wearing bunny suits and gloves. You'd think you were looking at a semiconductor facility,” he says. “We got 18% efficiency after only two months, and we feel we can easily get to 20% by the end of this year or even a 24%.”

BioSolar's BioBacksheet is designed to replace current backplane/backsheet materials. When BioSolar set out to design and develop a commercial bio-based backsheet for the crystalline silicon market, they had three standards: it had to be green, it had to be less expensive and it had to be more durable than what was being used.

Currently the most popular backsheet configuration used by crystalline silicon solar PV manufacturers are: TPT™ (Teller, Polyester, Teller) or TPE (Teller, Polyester, EVA), both with three layer laminate configuration.

“The problem with the multi-layer is that every time you combine two or three different materials, especially laminated together, the coefficient of adhesion is an issue because when you have two dissimilar materials, over time with thermal expansion and stresses, they can actually delaminate. So that has been one of the biggest problems for solar modules that have been in the field for a long time.”

“We developed a mono-layer, green backsheet that simply uses one layer of extrusion. There is nothing that can separate over time and it is comparable or better in all ways to the standard TPT or TPE being used,” Lee says. “Plus it is 100% green. The BioBacksheet is derived from a proprietary polyamide resin formulation based on castor bean oil.”

While Canadian Solar is continually working on many levels of product improvement in their test lab, one unique product is drawing a lot of attention in the market. This is a rail-free automated grounding system for standard, high efficiency crystalline solar panels, NewEdge solar panels. This has the potential to slash residential installation costs up to 50%.

“What we have done is licensed the technology from a very inventive company in California called Zep Solar. They devised a system that is basically a groove that we engineer into the side of the solar panel frame itself. Everything else about the module is exactly the same – the electrical characteristics and all the same laminates. We just create this very different extrusion with special characteristics that allows it to accept system hardware so panels on any roof can quickly connect one to the other using a very easy process. You slip this specially designed lug into the groove and it interconnects the panels. Twisting it 90 degrees creates a firm bond between panels,” Miskovsky explains.

“As soon as these modules are connected one to the other, they become one cohesive single grounded unit,” he says.

Evergreen probably has one of the most unique methods of creating crystalline silicon solar PV cells. String Ribbon™ Wafers differentiate Evergreen from other manufacturing technologies. Rather than utilising the standard method of cutting silicon ingots into wafers, Evergreen wafers are developed using their ‘string’ technology.

Evergreen Solar has a new range of solar panels recently introduced at Intercooler in June 2010. According to Lawson, these new products will deliver more power, increased efficiencies and be among the most visually attractive panels in the industry.

“These panels have been designed to deliver more electricity while having even less impact on the environment. Using our String Ribbon panels, these new products will continue to have the smallest carbon footprint and quickest energy payback (less than 12 months) of any other silicon based panel on the market today,” he says.

“Our Commercial ES-E Performance series panels featuring the latest, most advanced generation of String Ribbon cells featuring our new Boost-cell™ technology. They will begin to replace our current ES-A series panels from late 2010 onward,” Lawson adds.

The Boost-cell technology features solar cells without the traditional ‘bus-bars’ on the surface of each cell. Instead they have a fine network of conductive ‘micro-wires’ on the surface. This technology improves the cell efficiency by about 6%. The micro-wires replace the conventional bus-bars to reduce cell shading and improve current collection.

For the residential solar PV market, Sharp has its OnEnergy solution, which is a total system; modules and the mounting system. “Last year we introduced a 60-cell module for residential rooftops that has a beautiful black frame and black colour between the cells that looks very good.

This year, in fact by the end of this month, (May 2010) we will be boosting the power of that system by 5 W per module, bringing it up to 240 W. When we first introduced the 60-cell module it was only 200 W. So, about every 6 months, there has been a 5 W increase in power,” Wormser says.

SANYO's HIT (Heterojunction with Intrinsic Thin layer) solar cell, composed of a single thin crystalline silicon wafer sandwiched by ultra-thin amorphous silicon layers has shown industry-leading performance for the past 15 years. The company is continually looking for new ways to enhance their HIT technology and one of the latest is making Bifacial HIT solar cells, where the backsheet is not plastic, but glass.

The back face of a HIT double panel generates electricity from ambient light reflected off surrounding surfaces, and combines with power from the front face of the panel. Depending upon system design and site, this results in up to 30% higher power generation (more kWh) per square foot.

This past March, SANYO completed installation of two Solar Parking Lots, incorporating these Bifacial HIT solar panels and lithium-ion battery systems in Tokyo. The clean power generated from the solar panels installed on the roof is stored to be used to recharge electric hybrid bicycle batteries and illuminate the parking lot lights. By combining HIT solar panels with lithium-ion battery systems, it enables recharging the electric hybrid bicycles without any commercial power source, even at night or on a rainy day.

Higher efficiency technologies are cheaper to install (the area penalty affects balance of system, land costs and isntallation time).
 

Solaria has another unique use for glass. “Solaria technology is quite simple. It looks like any standard solar panel but the difference is that we use optical technology – a special lens on the cover glass of the panel to focus the light for the low concentration,” Shugar says.

“The way it is accomplished is we take standard crystalline solar cells and cut them into narrow strips. We do that with a very high yield, over 99%. So we don't lose or waste any material. All solar panels have a tempered glass that goes on the top, a standard type of low iron glass that is very good at transmitting light,” Shugar says.

“We use low iron glass too. The difference is that our glass has a ribbed pattern. This is a very simple optical device. We align our strips under these patterns and do it in a way that creates a panel that produces the same amount of power as other panels with only a third of the actual solar material. And we can assemble this in a highly automated fashion.”

SOLON's latest products include their new SOLON Black 280/12 which is the first crystalline module that can be attached to metal roofs for commercial installations using an adhesive. Specially developed for use on lightweight industrial metal roofs at the 25th Symposium on Photovoltaic Solar Energy in Bad Staffelstein, Germany, this past March, the frameless design of the SOLON Black 280/12 module is attached directly to the roof using a silicone-based adhesive, without any roof penetration.

“Assembly time is substantially less when compared to a conventional solar power system using crystalline modules because fewer components are required, the system is lighter weight, and installation is uncomplicated when using an adhesive,” Alcombright says.

Many owners of flat metal roofs were unable to use these surfaces for solar PV systems due to load-bearing restrictions of the roofs. Owners were also concerned about leaks once the mounting system was installed.

The SOLON Black 280/12 is manufactured using 72 monocrystalline cells and weighs only 8.5 kg/m, making it extremely lightweight. The modules are particularly well-protected against theft since they are attached with an adhesive. It is also protected against corrosion with other foreign materials on the roofs.

Suntech has several new and interesting products. One of the most interesting is their revolutionary Pluto™ solar PV cells. These decrease reflectivity of cells, ensuring that more sunlight is absorbed and increasing output to record-breaking levels. Its solar PV cells have a conversion efficiency of up to 19%, versus the industry average of 13%.

The Pluto technology was developed based on world record holding PERL solar cell design from the University of New South Wales (UNSW). Suntech successfully commercialised this into their Pluto solar cells and HiPerforma™ solar modules.

Pluto cells feature a unique texturing process that improves sunlight absorption, even in conditions of low and indirect light.

“Our innovative Pluto cell design and ultra-fine top contact gridlines combine to boost power output, delivering a 10-15% performance advantage using the same materials, wafers, and module line equipment as a standard cell. Pluto's extra fine cell fingers (not, vert, similar30 μm), reduce surface shading and boost sunlight absorption into the cell and give the product its sleek appearance,” Beebe says.

Upsolar's semiconductor based business model has allowed them to produce a wide standard module range is adapted to suit all types of installation. Their monocrystalline modules with power output from 160 Wp to 180 Wp are used mainly for rooftop installations while their polycrystalline modules from 200 Wp to 280 Wp are typical for large scale power systems.

“By utilising the semiconductor business model we are able to manufacture a top tier product with a very low capital expenditure. It also keeps us a lot more nimble to needed changes than many of our competitors who do it all in-house,” he says.

2011 and beyond

Everyone has a positive view on what the future holds for the crystalline silicon market and is working toward that bright future.

Aide Solar's plan is to continue to focus on the manufacturing side and to be ready to be in the position on the module side jump from 250 MW to 500 MW next year. On the cell side to go from 70 MW to 420 MW by the end of next year.

BioSolar's recent announcement of commercial production of the BioBacksheet has been very successful for the company. The benefits of the new material plus the lower cost are bringing in large quantity sample orders from major c-Si solar PV manufacturers so they can test it in their labs and see how to best integrate it into their current manufacturing processes.

Miskovsky says that Canadian Solar is partnered with the Energy Research Center of the Netherlands (ECN) to apply metal wrap-through (MWT) cell technology to Canadian Solar's production lines, which eliminates the need for front-side busbars, giving more surface area, further boosting conversion efficiencies.

“This has the potential to boost solar cell efficiencies up to the 18.5% range by basically transferring most of the energy harvesting to the back contact of the cell. This will be on a number of our products soon.”

Evergreen is releasing three new products for residential and commercial markets. “All three will retain our industry leading −0/+5 W power tolerance, textured cells and anti-reflective treated glass in order to maximise electricity production,” Lawson says.

"While 2008 ended badly for the industry and 2009 was very tough, 2010 is seeing a substantial upturn in the industry..."
- Paul Wormser, Senior Director of Engineering for Sharp Solar Energy Solutions Group

Wormser says that while 2008 ended badly for the industry and 2009 was very tough, 2010 is seeing a substantial upturn in the industry. “I see 2011 a continuation of 2010. All the conditions for growth are right here. We are very excited,” he says.

This past February, SANYO announced the successful on-time opening of the SANYO Solar of Oregon solar PV silicon manufacturing plant and also the strategic partnership agreement between SANYO North America Corporation and InSpec Group.

The strategic partnership will utilise SANYO's industry-leading quality of products and innovation to achieve full integration of SANYO's total energy solutions product line across the USA and InSpec Group's strength of experience in engineering and construction management of complex solar installations.

Solaria is planning to develop a module featuring a 3X lens, which will reduces silicon cell material 67% compared to standard PV modules and further improve the value for customers.

SOLON is heavily invested in utility-scale systems and is working on a new product that will be called Velocity. “Velocity to us means reducing both the time and the cost to getting a full system operational,” Alcombright says.

“The innovation we developed in the Velocity is basically a standard system that is configured in 1 MW AC clusters. This is a pre-packaged set of pre-configured blocks with either single axis or fixed rack configuration. Like a turnkey solar farm.”

Suntech has the goal of doubling production, continuing their historic business pattern. “I was at one of our newest facilities in Shanghai. We are planning to produce 1 GW of cells from this one facility. To put that into perspective, less than 10 years ago the entire industry was not producing 1 GW per year. Now we have one building that can produce 1 GW this year on its own,” Beebe says.

Upsolar has been increasing production output by about 80% a year and Dalbey says that they have USL rating so the company will continue to solidify relationships with manufacturing partnerships and get into the 500 MW range by 2012.

He agrees with the consensus that as far as the strength of crystalline technology goes, “It is well proven with installations generating power steadily for 25 to 30 years now. Steady improvements in both product and process have kept both mono and polycrystalline PV modules at the top of the food chain.”

Most would agree that still being considered ‘top of the food chain’ after 30 years is a pretty good place to be.


About the author:

Based in California, Joyce Laird has been writing for a wide range of industrial magazines for over a decade. Her extensive background in the semiconductor industry created a perfect transition to covering developments in photovoltaics.

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