Alta Devices, a start-up in Santa Clara, Calif., presented research at the 37th IEEE Photovoltaic Specialist Conference, in Seattle, this week that claims its thin-film gallium-arsenide cell can convert 27.6 percent of the sunlight striking the cell into electricity, under standardized conditions. Since the paper was submitted, the company says it has upped the efficiency to 28.2 percent. That beats the previous record of 26.4 percent for a solar cell with a single p-n junction, which was the first improvement in years over 26.1 percent. Both numbers, according to Alta, were independently confirmed by the National Renewable Energy Laboratory.
The efficiency was measured on a laboratory-made solar cell. Efficiency tends to decrease once the cells are packaged into usable modules. “We assume we will ultimately be able to achieve modules that are around 26 percent, and that’s plenty to be competitive with fossil fuels,” says Christopher Norris, CEO of Alta.
The key to achieving the record was photon recycling. When the photons in sunlight are absorbed in a photovoltaic material, they split into an electron and a hole. The electrons that pass out of the cell can be used as electricity, but many of them are lost in the semiconductor when they recombine with a hole to produce either waste heat or a new photon. By carefully growing a high-quality single crystal of gallium arsenide, the company managed to ensure that more than 99 percent of the recombinations would result in new photons. Those photons could then create a new electron-hole pair and give the electron another chance to be captured as electricity. The Alta team also improved the reflectivity of the metal contacts on the back of the solar cell, so that any photons that exited the cell would be sent back in for possible reabsorption.
The theoretical maximum conversion efficiency for a solar cell with a single junction is 33.5 percent. “We can see a path to 30 percent with our same design right now,” says Norris. Adding a second junction could also increase the energy output.
The more efficient a solar cell is, the faster it pays back the cost of manufacturing and installing it. But efficiency and cost have been at odds with each other in solar cell design. Gallium arsenide is naturally better at converting light to electricity than the chief contenders, such as silicon and cadmium telluride, but it tends to be more expensive.
The most efficient materials are single-crystalline semiconductors, but those are usually pricier. Low-cost materials, such as amorphous silicon, cadmium telluride, and copper indium gallium selenide, are less efficient; CdTe cells are around 12 percent efficient. Alta solves this problem by using only a small amount of a high-quality material—a thin film of gallium arsenide about 1 micrometer thick.
“That is the whole trick. Don’t use much gallium and don’t use much arsenic,” Norris says. He says an Alta module should cost about the same per watt as a CdTe module but produce three times the energy.
The company cut down on the material cost by using a process called epitaxial liftoff, developed by Eli Yablonovitch, an engineering professor at the University of California, Berkeley, and a cofounder of Alta. Technicians start with a GaAs wafer as a seed layer and grow a thin-film photovoltaic device structure on top of that. They peel off the thin film, attach it to a metal backing, and finish processing it into a solar cell. The process leaves the original wafer, which they can reuse for the next batch of solar cells.
Alta is working on a pilot production line to produce samples of its solar cells sometime this year and expects to have early commercial shipments by late next year, Norris says. The company has raised US $72 million to develop its production process.
Bharat Heavy Electricals (Bhel) has achieved a major landmark with the successful deployment of its Space Grade Solar Panels on the GSAT-8 satellite of the Indian Space Research Organisation (Isro). Launched from French Guyana, the satellite is Isro’s heaviest, weighing about 3,100 kg at lift-off. India’s advanced communication satellite,
GSAT-8 is a high-power communication satellite being inducted in the Insat system. The four solar panels supplied by Bhel for GSAT-8 have an area of over 5 sq m each, totaling around 21 sq m, and comprise multi-junction solar cells in series and parallel combinations, with a total power capacity of 4.5 kW. The panels were manufactured to strict space-quality standards wherein cell welding, bonding and wiring work was carried out by highly skilled manpower. The panels were further subjected to detailed testing by Isro, such as vibration test and thermovac test, as part of the requirements to validate the mechanical, electrical and thermal performance. Bhel, in collaboration with Isro, has established a state-of-the-art 10,000 clean room facilities at its Electronics Systems Division in Bangalore for the assembly and testing of Space Grade Solar Panels using high efficiency solar cells.
Solar powered gadgets are everywhere now, and the ways solar power is incorporated into gizmos is fun to follow. Oh sure we’ve seen the double-take items like solar bras, and the cooler devices like cell phones. But so many are just down right strange. We’ve gathered up a handful of the odder solar powered devices that have made their way on to the scene. Click through to check them out.
Photo via 724deal
Starting with the silly, here is a desktop gadget that it meant entirely to entertain. The little head and body bobble back and forth, thanks to the tiny solar panel on the base. The point? Perhaps it’s just the very last life line to cling to if you’re dying of boredom.
Photo via Toys and Gadgets
This one is certainly strange, though actually serves a purpose. You can build your own bonsai tree with branches sporting various solar panels. The panels charge up a battery that you can connect your gadgets to. The battery, gadgets, and wires can all be stored inside the base, er, pot. It will lend a very sci-fi look to any home, and if you get bored with the look, just rearrange the branches. It’s one house plant you’ll have a hard time killing, but works just as hard converting sunlight to energy as its greener neighbors.
Photo via Select Solar
This…is a spider. We know it’s so because that’s what the company says it is…and that’s about the only way we’d guess it to be a spider. It does kind of resemble those little jumping spiders that hop on you when you’re laying in the grass at a picnic. Kind of. At any rate, it’s a 21-piece DIY kit that you, or anyone over the age of 8, can put together. If you’re itching to have it, most of the solar powered plasticrap stores sell it.
Photo via Technabob
What solar toy collection is complete without a solar powered rope-climbing monkey?! There’s nothing quite like slapping a solar cell on a piece of plasticrap and calling it educational. This little guy is intended to help kids “appreciate the power of alternative energy.” More likely, they’ll put it together, watch it climb the rope a few times and then it’ll end up at the bottom of the toy chest. If a parent really wants to make a toy educational, they’d grab one that is already at the bottom of the toy chest and teach their kids a cool hack, powering it with solar cells ripped off of the neighbor kid’s solar powered toy monkey that got used twice and tossed aside.
Photo via Gizmag
This is the Odysseus from Aurora. It is basically a low-flying satellite. It can fly in sustained uninterrupted flight for over five years, hanging around altitudes between 60,000-90,000 feet. And, it’s solar powered. It’s a concept device created by Aurora for military use, intended for surveillance and reconnaissance, communications relay and environmental monitoring. Useful, but still definitely a stranger bit of flying solar powered technology than we’re used to.
Photo via Chinavasion
It’s not too often you think about your tire gauge. Tire pressure, yes; tire gauge, no. Especially the power source for your gauge. In fact, it’s easy to find one that doesn’t require a power source at all. But if you’re concerned that you have to have a digital tire gauge and it has to be reliably powered, well by golly there’s a solar powered one out there for you. So if you’re out in the middle of nowhere and you just have to check your tire pressure, have no fear…the solar cells on your trusty tire gauge won’t let you down.
Photo via Pocket Lint
If you’re looking for a way to line your walkway other than using solar luminaries, this could be a solution. But it looks a little too similar to a radioactive waste bin. We haven’t seen a yard-bound solar gadget light up quite like this, and in fact, one version will glow in an array of colors. The solar cell is on a spike that you set elsewhere, and a wire runs back to the battery in the pot. The makers say you can get as much as 8 hours of glow time in the summer, and as much as 4 in the winter.
Photo via Sunshine Solar
If you don’t want to return to a hot stuffy car, you could try out this solar powered ventilator. Somehow, with the window closed, it manages to clip on to your window and circulate fresh air into the car. Riiight. We’re guessing it actually just clips to your car window and whirrs away, pushing air around the car…nothing special, especially since the price tag is a relatively cheap $38. You might be better off sparing the plastic and just opening you car door and fanning your arms over the driver’s seat a few times before hopping in.
Photo via Gadget.Brando.com
If you want to look strange while walking around with a strange solar gadget, stick this one on the brim of your hat and consider yourself a success. The hefty-looking solar powered fan clips on to your visor and blows air directly into your face. Makes sense for a really hot day, but it might be a little less dorky to use a hand-held solar powered fan. Or, how about just…a fan.
Photo via Dvice
This little “Bugbut” named Nigel takes the cake for strange. Basically it’s a bunch of gadget pieces duct tapped together and powered by a solar cell. It climbs slowly around your desk, creeping out anyone who passes by. You can get one from Jenny, a.k.a. Tinyminds at Etsy. Definitely. Strange. Just keep it and the solar bug zapper a good distance apart.
Traditional uses of silver have been in coinage, photography, jewelry, and tableware. Today, with refined techniques of miniaturization, the precious metal‘s properties are being aligned toward better use in the new fields of technological devices. Silver has long been respected for a natural ability to interfere with the chemical bonding of bacterial cells. Besides its high sensitivity to light, silver has the highest properties of electrical and thermal conductivity. These factors serve, today, to give the rare metal definitive use in the new technologies.
Silver maps the circuitry of what was formerly electrical wiring on printed circuit boards (PCBs). This function represented a milestone advance in the miniaturization of electronic components. Coupled with the digital signaling ability of, now, even smaller configurations of transistors, diodes, and other electronic components, this miniaturization has led to an exploding production of cell phones, mp3 music players, and implantable pacemakers, among a vast array of electronic products. Interest in research and development is at the forefront. DuPont, for example, discusses a new technology of “Silver Conductive Inks for PCB” that can overprint even “smaller diameter vias.”
Expressed as “nanotechnology” or “nanosystems,” radio frequency identification (RFID) tags are made with silver based ink. This process uses, sometimes hidden, but electronically identifiable, identification codes, or antennas, on nearly every kind of product imaginable, from laptops to animal tags, or warehouse items at Wal-Mart‘s. Nano-size embedded electronic components created with nano silver, include connection traces, resistors, capacitors, and inductors, antennas, and shielding nets.
The latter points to the role of silver mixed with copper as a shield to electromagnetic or RFI interference occurring from electromagnetic radiation or an electronic device. Plastic or fabric is coated with the silver-copper alloy to reflect EMI from nuclear radiation, as in the case of the workers recently working on the damaged Fukushima Daiichi nuclear plant in Japan.
Silver-oxide batteries are used, in the shape of small discs or buttons, in hearing aids and watches. Silver-zinc batteries have been shown to be effective as rechargeable batteries with more run-time than the lithium-ion butteries, and less volatile. But their technology, along with silver- cadmium batteries, is still evolving. Such is the case with silver used in silicon photovoltaic cells. Thin-film solar cells, coated with a paste of nanoparticle silver, have been found to absorb more photons of light then other processes, thereby increasing the efficiency of the solar cell, but not necessarily lowering the expense.
Boise City, Iowa, intends to have its $45 million, 10-megawatt photovoltaic power plant completed by 2012. Using silver solar cell technology, based on layers of 50 microns thick monocrystalline silicon, the project is intended to furnish energy for up to 15,000 homes. A different kind of energy-producing technology involves using the heat transfer properties of silver to scald nitrate salt to high degrees of heat. The heat is then transferred to drive steam turbines in electric generators. This setup currently works successfully to provide electricity power in Boulder City, Nevada.
All of these “high” technologies involving silver have reached out in specific directions for research and development that are empowered with real and necessary goals. The modern techniques of miniaturization have expanded silver into a fountain of energy.
Research into new materials and structures is under way. Innovative technologies are being tried out. But it has to result in large-scale manufacturing applications. DR. MADHUSUDAN V ATRE, PRESIDENT AND M.D., APPLIED MATERIALS, INDIA
The Jawaharlal Nehru National Solar Mission (NSM) and its guidelines have created significant excitement in the industry with the announcement of new projects, setting up of assembly units and States vying with one another to offer incentives. With critical mass coming in, several large players are looking at backward integration, possibly manufacture of wafers.
Dr. Madhusudan V Atre, President and Managing Director, Applied Materials, India that is among the top suppliers of equipment and technology for solar industry and semiconductor segments, provides insights into the way forward.
Applied Materials and IIT-Bombay have joined to set up National Centre for PV Research and Education and a Clean Lab to work on new materials. Dr. Atre, who has been appointed a member of the advisory committee to drive the sector’s growth, touches upon prospects and challenges in an interview to Business Line. Excerpts from the interview:
What is happening in the solar industry? How do you perceive some of the changes and challenges?
A lot of developments have taken place since the Solar Mission. Various projects have been finalised. On the photo-voltaic side, projects ranging from 1MW to 5MW and on the solar thermo lighting, 50 MW to 70 MW have been finalised.
Many projects approved under the NSM have achieved financial closure and completed land acquisitions.
Apparently things are moving. From the Government’s perspective, it must be reasonably satisfying.
Apart from solar cell manufacturing and utilities, backward integration into wafering and polysilicon is also under way. All this will lead to the creation of a very vibrant solar ecosystem in India.
There have been developments at the Central and State Governments. Gujarat continues to drive a lot of solar-related projects.
What about the semiconductor business?
The Government wants to pitch in $5 billion on setting up infrastructure. The modifications in the Semiconductor policy in 2007 will be reviewed. Many changes are proposed in the policy. It is good the Government is thinking seriously about fabs.
That would be good from a manufacturing perspective but depends upon the local market. Areas of healthcare, automotive, and industries will need them.
These are big guzzlers of semiconductor chips. The changes recommended in the policy can probably make it a little more practical with the perspective of helping set up a fab.
Many companies are getting into an implementation mode. Some of them are raising finances and setting up units, such as Lanco and Moser Baer. What stage are they in capabilities?
Many have attained financial closure and acquired land, approved either by the State or Central Government and started their projects. The manufacturing technology is not a widely prevalent expertise. They have to depend on established technology and Applied Materials is one of the players.
Besides just the cell and module manufacturing which is usually thought of in the solar arena, some want to go a few steps aheadin terms of either manufacturing polysilicon itself or taking polysilicon blocks and making wafers out of them. Till now wafers needed for the crystalline silicon solar cell manufacturing are imported. Some are considering why not bring the silicon and do wafering.
Why should we bring the silicon and do the wafering , why not manufacture the polysilicon here is another line of thinking.
If you look at the chain which essentially comprises silicon, wafers, cells and various utilities, there are players who are now looking across the chain, and not just at a cell or a module. That is important.Through vertical integration, you can bring down costs. If you import a wafer, you are not only paying the guy from whom you are buying the wafer for his manufacturing cost but you are also paying for imports, logistics and transport. Internally, there is an inherent nailing down of costs.
This will be a domain only for serious players with deep financial resources. Backward integration brings about a cost and investment escalation. In the long run, serious and non serious players will get segregated.
Two years ago we were talking of Rs 19 crore for 1MW of installation; now they are saying Rs 15 crore and some of them a little lower than that. What is your assessment of ground reality?
They are talking of Rs 15 crore per MW, the figure has been arrived at after extensive study and with industry inputs. The cost will go down as a function of time, technology escalation, efficiency escalation. That is why now the tariff stands at Rs 12 per kilo-watt. That will decrease year on year as the technology goes up and cost goes down.
Do you see some new technology challenging usage of solar devices? What is your assessment from a research perspective?
Huge amount of research on technologies and devices is under way into new materials and structures.
Some are doing the corrugation of a solar cell on a certain dimension to capture more sunlight, so as to increase the efficiency. Innovative technologies are being tried. But it has to result in large-scale manufacturing applications. R&D to manufacturing process is a significant step.
For instance, flexible solar cell is something that can be used to wrap around objects. This will increase the mobility of solar units. Many new technologies and applications can come up. At the end of the day, it depends on how much of it can be scaled up in terms of size, manufacturing and scaling down of the cost.
We are talking about large installations, what about small units?
Power plant utilities are as important as standalone distributed solar applications. The policy lays a lot of effort on rooftop, lighting applications and other commercial applications.
The higher the utility, the cost and investment is that much more. There is a lot of focus on this by distributors and small scale plants.
The Solar Mission had taken out a directive that out of the 1 Gigawatt generated 100MW has to be diverted towards roof-top applications.
The chic Solar Handbag features 100 small silicon solar cells that are seamlessly woven into its conductive embroidery. The solar cells on the bag’s surface collect sunlight & generate 2 watts of energy that’s stored on a lithium-ion battery.
The optical fibers come on automatically when you open the bag, rendering it easy to search things inside the handbag.
The luxury solar handbag is to retail soon.
Dow Corning Corp., which is into silicones, silicon-based technology and innovation, has named Global Wedge as a distributor of silicon-based solutions for the manufacturing of solar photovoltaic modules in India.
Global Wedge, a distributor of photovoltaic (PV) raw materials, solar modules and panels, and a developer of solar power projects since 2001, will supply high-quality silicone solutions to Dow Corning’s customers in India. Located in Hyderabad, India, Global Wedge has an excellent reputation as a PV materials supplier and an extensive customer base in India.
“India continues to grow as an economic powerhouse, and the solar industry with it. We are excited about the prospect of providing solutions to the Indian solar power industry to support its expansion,” said Allison Ashbrook, global distribution manager, Dow Corning Solar Business. “We look forward to working with Global Wedge in India and with our broad network of regional distributors throughout the Asia-Pacific region to provide silicone solutions that will help solar energy become a viable energy option.”
“We are excited to be associated with Dow Corning as their distributor for India,” said Rao Marella, president, Global Wedge. “Dow Corning’s specialty is in the development and application of silicon-based products. They are global leaders in the industry and our customers will derive the benefit of using superior products with the highest levels of quality and reliability. Most of our customers export their modules to Europe and America. To make modules to international standards, Dow Corning’s silicones continue to be their number one choice. We thank our customers for their confidence in us, and we are pleased to be a part of the success of the solar business in India.”
Dow Corning’s expansion of its global distribution network follows several recent investment announcements including:
* Completion of a new Solar Solutions Application Center in JinCheon, Korea, Dow Corning’s second;
* Plans to build another solar center in Shanghai, China, announced in February; and
* Plans for a $13 million Solar Energy Exploration & Development Center (SEED) in Seneffe, Belgium.
One of the only companies in the world able to provide silicon-based solutions throughout the entire photovoltaic value chain, Dow Corning is investing to expand its portfolio of total solution packages for solar cell manufacturing, module assembly and installation. Solution packages are built on high-performance silicone products such as encapsulants, adhesives, coatings, potting agents and sealants, as well as next-generation solar grade silicon. www.dowcorning.com
The launch of the Jawaharlal Nehru National Solar Mission (JNNSM) has triggered a demand in the market for solar photovoltaic (PV) projects and products. With this, the need for solar modules has increased, driving up demand for solar cells. However, delivering low cost solar energy is the biggest challenge faced by the manufacturers. Currently, a factor that influences the cost in a big way is efficiency. Thus, the right technological choice is critical in order to ensure good financial returns, while maintaining the quality and the long life of the product.
A solar cell, also called a photovoltaic cell, is used to convert solar energy into electrical energy. Solar cells are the basic elements of a solar module or panel. These cells are made of silicon, a common semiconductor. A typical modern solar cell measures 15 cm × 15 cm. It is covered by a clear anti-reflection coating (ARC) that reduces the amount of light lost to reflection at the cell surface.
Technology behind different types of cells
There are three main types of solar cells, which are distinguished by the type of crystal used in them. They are monocrystalline, polycrystalline, and amorphous. To produce a monocrystalline silicon cell, absolutely pure semiconducting material is necessary. Monocrystalline ingots are manufactured through C2 method from polycrystalline granules or chunks. Monocrystalline wafers and slices are extracted from these ingots. With this method, quality of silicon further improves, and cell manufactured from these wafers have higher efficiency.
Production of polycrystalline cells is more cost efficient. In this process, ingots are developed with directional solidification system furnaces. These ingots are sliced into multicrystalline wafers. During the solidification of the material, crystal structures with different direction are formed. As a result, the solar cell is less efficient.
If a silicon film is deposited on glass or another substrate material, the result is a so called amorphous or thin layer cell. The layer thickness amounts to less than 1µm—for comparison, the thickness of a human hair is 50-100 µm. The production costs of this type of solar cell are lower because of the lower material costs. However, the efficiency of amorphous cells is the lowest when compared to the other two types of solar cells.
In order to provide suitable voltages and outputs for different applications, solar cells are connected together to form larger units. Cells connected in series have a higher voltage, while those connected in parallel produce more current. The interconnected solar cells are usually embedded in transparent ethylene vinyl acetate (EVA), fitted with an aluminium or stainless steel frame, and covered with transparent glass on the front and with tedlar on the backside to make a solar module.
Crystalline silicon cell: About 80 per cent of the manufacturers in the world use crystalline silicon (C-Si) cell based technology. “The current installed capacity of solar cells based on this technology stands at 600 MW and that of modules ranges between 900 MW to 1 GW in India,” informs Dr VK Kaul, general manager, Solar Photovoltaic Group, Central Electronics Ltd (CEL). CEL is among the pioneers in solar technology, and manufacturing crystalline silicon cells.
C-Si technology has been time tested and thus manufacturers rely on it a lot more. “One of the scoring factors for C-Si cells is its high efficiency. Two decades back, crystalline silicon cell efficiency was 8-10 per cent. Today, we are getting 16-17 per cent efficiency,” says Sunil Goel, vice president, Maharishi Solar Technology Pvt Ltd.
Monocrystalline cell: Websol Energy Systems Ltd manufactures monocrystalline (mono Si) cells, and has recently introduced two solar modules—W2300 and W2800. “Both the modules are made with 156 mm x 156 mm mono Si cells. A W2300 module is a configuration of 60 cells connected in series and giving an output of 235/240/245Wp with module efficiency of more than 14.3 per cent. A W2800 module uses 72 cells in a 9cm x 8cm configuration to give an output of 280/285/290Wp with a module efficiency of 14.5 per cent,” explains S Vasanthi, director, technical and marketing, Websol Energy Systems Ltd.
Bharat Heavy Electricals Ltd, Bharat Electronics Ltd, Euro Multivision, Jupiter Electronics, Maharishi Solar Technology Pvt Ltd, Tata BP Solar India Ltd, Indosolar Ltd and Websol Energy Systems Ltd are some of the major players that have a strong foothold in this field of technology.
Amorphous silicon cell: Due to the inflated price of solar silicon, the PV industry introduced a cost efficient technology—the amorphous silicon (a-Si) cells or thin film technology, which was a big breakthrough in the industry. Its biggest advantage is that it uses a much smaller quantity of silicon than C-Si, which is expensive. There are three main thin film technologies to date—copper indium gallium selenide (CIGS), cadmium telluride (CdTe) and amorphous silicon.
The disadvantage of thin film technology is its lower efficiency compared to C-Si but there are solutions to overcome this limitation. Thus, low cost and high efficient thin film is not far from becoming a reality. Another concern about this technology has been regarding its high tendency to break. But today, the technology has been developed to have a non-breakable flexible material as the substrate. This technology performs better in low light and works well in both diffused and direct sunlight, which has a definite cost reduction potential.
The market for thin film PV is huge in countries like Germany and USA. In India, the deployment of this technology has not yet picked up, though the potential seems high. Some of the major players in this field are Moser Baer Solar Ltd, Hind High Vacuum Company Pvt Ltd (HHV) and Shurjo Energy Pvt Ltd.
Thin film technology has some advantages over crystalline silicon as it requires less silicon (it has a thin layer with a thickness of few micrometers), whereas the silicon thickness in multi-crystalline and mono-crystalline solar cells is thicker than 200 micrometers. Another advantage is that it produces panels that show a much lower temperature coefficient than crystalline modules, which results in a higher yield in the field. In hot countries, this advantage results in a 5 to 10 per cent higher output per installed watt compared to crystalline silicon. Currently, cost reduction is the main focus of the PV industry and thin film technology emerges as the right choice for the industry.
“Data shows that the thin film solar modules in India are generating 5-8 per cent more energy than their installed capacity,” informs Vivek Chaturvedi, global head, sales and marketing, Moser Baer Solar Ltd. The company’s total installed capacity of 90 MW of C-Si cells, 100 MW C-Si modules and 50 MW of thin film panels has resulted in it taking a lead in the industry.
Bengaluru based Hind High Vacuum Company Pvt Ltd, with its turnkey production lines, has opened up a new chapter in large scale manufacturing that is based on amorphous silicon technology. With modifications and improvements in a-Si micromorph technology, the company claims to derive an efficiency between 10 per cent to 12.5 per cent.
Kolkata based Shurjo Energy Pvt Ltd is also in the business of CIGS thin film technology. In case of this technology, silicon is not used as the active PV semiconductor and, therefore, production is not hampered by any raw material supply problem. In addition, using only minute quantities of active material means the energy payback is far superior to conventional crystalline products. Studies show that CIGS material actually yields more energy per KW installed, compared to traditional crystalline products, due to its better performance in low light conditions.
The latest breakthrough in cell technology is the introduction of dye or organic cells. An organic solar cell is flexible, lightweight and affordable (it is about 1/3 cheaper than an inorganic solar cell). The main drawback of organic cells is their lower efficiency in converting sunlight into electricity, when compared to conventional solar cells. In general, organic cells have around a 1-3 per cent efficiency rate, while silicon based solar cells have an energy efficiency of about 15-20 per cent. However, the advantages of this technology over conventional solar cells are its low impact on the environment and easy manufacturing process. Also, because these cells can be attached to flexible materials, they can be put on many surfaces.
“This technology is at a very nascent stage and it will take some time to replace the current single crystal silicon solar energy solutions. Rather, they are seen as an opportunity in their own niche market. As time progresses and the focus of the research concerning these cells broadens, the dye/ organic solar cell might just become a contender in the current solar panel market,” opines Dr Kaul.
Challenges buyers face
A buyer faces the dilemma of keeping up with the pace of changes in the solar power industry. The most obvious criterion for buyers is the choice of technology—its viability, track record, future prospects and the total cost of the project in relation to the revenue generated. This is the most critical aspect as the success of the whole project depends on the option the buyer chooses. While both crystalline silicon and thin film have their own benefits and shortcomings, it is the end usage of the technology that will decide the success of a particular project.
“The most important criterion is not the upfront cost, but the lifetime cost compared to the product’s value over its entire life time. So a buyer should basically evaluate the end use of the technology. For a grid market, a high efficiency module is required. The total profitability of the project depends on the energy generated and evacuated to the grid,” says Sunil Goel.
Thin film has not yet been proven in India as the technology has not yet been deployed on a large scale. Since its fairly recent entry into the industry in 2002-03, the time frame seems less for testing a technology with decades-old and tested crystalline silicon technology. However, experts feel this technology is good for reducing grid parity.
Apart from the choice of technology, buyers should be aware about the efficiency of cells while making a purchase decision. Efficiency of cells depends on the quality of raw material used. The buyer should always ensure the efficiency aspect, and if possible, should check the performance of solar PV power plants by ensuring the energy generated (kWh).
Another factor that comes into the picture is the cost. “Since India is a price sensitive market, the buyer should also look at this aspect. Besides, buyers should also look for warranty periods that ensure quality and efficiency of the cells. Product certification, and environment and safety certification is equally important for a buyer, as in the long run, these play a huge role in the viability of the project,” informs S Vasanthi.
Latest developments towards increasing cell efficiency
Globally, manufacturers are moving towards developing new methods of increasing cell efficiency and reducing the Kerf loss in wafering. US based company Solaicx, a solar cell ingot maker, has developed a manufacturing process for wafers used in solar cells, which it claims results in higher efficiency. It has been designed keeping in mind the special needs of the solar cell industry. Similarly, Japan’s New Energy and Industrial Technology Development Organisation (NEDO) launched a research initiative to develop innovative solar cells. This led to achieving the world’s highest solar cell conversion efficiency of 35.8 per cent.
Although India is not in contention in the higher efficiencies race as yet, the efforts made by the domestic manufacturers are commendable. The enegy efficiency achieved today ranges between 16-18 per cent. Websol Energy Systems Ltd claims to have achieved an efficiency of up to 18.2 per cent. “Manufacturers are reducing the thickness of silicon, which reduces the usage of silicon and eventually helps in cost reduction,” says Dr Kaul.
Other initiatives to enable high performance solar cells while maintaining or even reducing manufacturing costs include the use of silver solar paste with high solids, and using techniques such as hot melt and double printing. This further helps in increasing the performance of the cells. The hot melt technique reduces the overall capital cost of equipment by eliminating dryers.
Key solar cell manufacturers
* Bharat Electronics Ltd
* Bharat Heavy Electricals Ltd
* Central Electronics Ltd
* Euro Multivision Ltd
* Hind High Vacuum Company
* Pvt Ltd
* Indosolar Ltd
* Jupiter Electronics
* Maharishi Solar Technology Pvt Ltd
* Moser Baer Solar Ltd
* Shurjo Energy Pvt Ltd
* Tata BP Solar India Ltd
* Websol Energy Systems Ltd
(Note: The names of the companies are in alphabetical order)
* Check the credibility and track record of the manufacturer
* If possible, verify the performance of solar PV power plants that have installed the solar PV modules that you’re considering
* Check the quality of raw material used
* Pay attention to the consistency of product performance
* Ask for product certification
* Look for quality management systems certification
* Check environment and safety certification
* Ask for product warranty
Traditionally, solar powered devices suffer from a two-fold problem. First, they have difficulty converting the light they capture to electricity. Second, they only capture a small band of wavelengths out of the wide range of wavelengths found in sunlight striking the Earth. Improving in either area can offer gains to the net power output (and efficiency) of a solar cell.
Researchers at the University of Missouri are claiming a breakthrough in the second category. They claim [press release] to have developed a device that can capture 90 percent of sunlight, versus the 20 percent that current photovoltaic (PV) panels capture.
To capture the wider range of wavelengths, Patrick Pinhero, associate professor of chemical engineering, used a special thin, moldable sheet of small antennas called nantenna. The resulting material converts heat to electricity and can be used both for industrial heat recycling and for solar designs. In solar designs it is capable of collecting both optical (visible) sunlight and the near infrared band sunlight that most cells miss.
Professor Pinhero collaborated with researchers at the Idaho National Laboratory and Garrett Moddel, an electrical engineering professor at the University of Colorado to develop a complete material with electronic devices capable of harvesting the heat and light collected by the nantenna.
Professor Pinhero is working to port the resulting device to a mass-producable design. He’s currently securing U.S. Department of Energy funding and money from private investors to accomplish this. To that end, he’s enlisted the help of Dennis Slafer of MicroContinuum, Inc., of Cambridge, Mass., a solar power and alternative energy firm.
“Our overall goal is to collect and utilize as much solar energy as is theoretically possible and bring it to the commercial market in an inexpensive package that is accessible to everyone,” Professor Pinhero states. “If successful, this product will put us orders of magnitudes ahead of the current solar energy technologies we have available to us today.”
You can’t fault Professor Pinhero for ambition. He says that within five years he should be able to deliver a finished material that complements traditional PV panel designs in rooftop installations, solar power plant installations, or rooftop car panels. This material would bump up the range of collected light, and by proxy bump up the cell’s net efficiency and power output.
The instructor expects to create a broad range of commercial spinoffs based on the technology. The spinoffs would be infrared (IR) detection based products, including contraband-identifying devices for airports and the military, optical computing, and infrared line-of-sight telecommunications.