Nanotechnology & Solar Power Conference: Solar is a more realistic solution to global warming than carbon sequestration and other "magic" technologies. All quotations and sources are referenced.

The fundamental driver for solar PV & solar thermal is the efficiency & cost of conversion of sunlight to electricity or to heat. The competition is either fossil fuels or nuclear energy. Nuclear has three basic problems with no solutions in sight: (i) the nuclear industry only exists because the promoters do not have to pay for the billions to trillions of dollars of damage that will be caused from a large scale accident - check out the Price Anderson act which limits damage claims in the US to $500 million - the nuclear industry is basically uninsurable because the upside of a major accident is incalculable by actuarial tables, despite all the "media fog" put out by nuclear advocates(ii)the nuclear fuel cycle enables the production of nuclear weapons - see North Korea, Iran, etc.(iii) nobody wants a nuclear reactor and especially the long term waste products in their back yard.

Fossil fuels all depend on the "carbon subsidy" for current pricing - current coal, oil, gas prices depend on not having to pay for the destruction of the global environment upon which all life (including humans) depends by the mechanism of global warming. We need to get a grip on greenhouse gases before the industrialization of Brazil, China, India, Russia gets anywhere close to US, Japanese, or Western European levels.

Some possible consequences if we do not halt rising CO2 include the increasing acidification of the oceans - with the reduction of the domain where most conversion of CO2 to O2 occurs, the rise in sea temperatures to the point where methane gas stored in ice formations called clathrates (potentially leading to a spike in CO2 levels last seen when forests grew in the artic & antartic regions), and the total destruction of the ozone layer.

Note that clathyrates in the Alaskan, Canadian, and Siberian permafrost alone is on the order of hundreds of gigatons, not much smaller than the total amount of carbon in the terrestrial biosphere. The melting of the permafrost alone would therefore be undesirable, assuming we want to maintain the current global economy and human population and biosphere and high tech civilization.

15 possible ways to remove 25 billion tons of carbon of which 7 need to be implemented to enable the most desirable growth path including survival of the oceans, the biosphere, life on earth as we know it, etc. Holding carbon emissions constant for 50 years, without choking of economic growth is within our grasp. If we take a growth rate of 20% per annum in solar photovoltaic production then production doubles every 3.5 years leading to a 1,000x growth by 2041 from the 2006 baseline. And a 16,000x growth by 2056, that is, all 7 wedges of the required reduction in carbon emissions could be enabled by solar photovoltaic, assuming a 20% growth rate can be maintained for 50 years.

Cost and affordability are major obstacle to full-scale PV integration. Today, even with tax subsidies, a minimum of $20,000 is required to provide base line power to a house in CA, that is 4 - 5 KW. In the January column I presented the estimate by Renewable Energy Corporation (REC), where REC targeted a 46% reduction in c-Si PV modules by 2010. The industry consensus is that PV modules represent about ½ the cost of installed solar modules, which suggests a 2011 price in CA (with tax subsidies held constant) about 20% or so lower than in 2007, or around $16,000.

While thin film & nano technologies hold great promise to reduce cost per watt, today at least 90% of current sales & manufacturing is c-Si based. So a significant reduction in c-Si costs would have the most immediate impact on the adoption of solar PV. Such reductions can be accomplished by the scale up of c-Si manufacturing plants to the GW annual level - see the NREL 2004 Study of Potential Cost Reductions Resulting from Super-Large-Scale Manufacturing of PV Modules.

Studys have been completed for the design for "A Solar City Factory" that will produce 2 - 3.5 GWp of solar panels per year - 100x the volume of a typical, thin-film, solar panel manufacturer in 2007, and more than 4x the volume of the entire solar panel industry in 2007. With a reasonable selection of materials, and conservative assumptions, this "Solar City Factory" can hit a price target of $1.00 per watt as the total price for a complete, installed solar energy system (6.5x - 8.5x lower than prices in 2007).

This breakthrough in the price of solar energy comes without the need for any significant new innovation. It comes entirely from the design of a very large, dedicated and optimized factory, the design of manufacturing equipment for a very large factory and the cost savings resulting from operating at such a large manufacturing scale." Following up on this report is the very interesting news in & many other sources re SolarWorld AG's (Germany) 500MW Wafer and Cell Plant in United States. "SolarWorld AG said today that it is beginning to establish an integrated solar silicon wafer and solar cell production facility in Hillsboro, Oregon. It will reach a capacity of 500 MW by 2009.

This would make the plant the largest solar manufacturing facility on the American continent. Together with the expansion of the silicon wafer production at Freiberg/Saxony to also 500 MW, the SolarWorld Group will have a total global production capacity in excess of one Gigawatt". "Now that we will soon have exceeded the threshold of 1,000 staff in Freiberg the Group will also create a large number of new jobs at Hillsboro", announces Dipl.-Ing. Frank H. Asbeck, Chairman and CEO of SolarWorld AG. In the new wafer and cell factory the Group will produce highly efficient, mono-crystalline solar silicon products thus expanding its technological spectrum. The products from the integrated production in Freiberg are primarily based on high efficiency multi-crystalline silicon". While this plant is not at the GW scale it will still have the capacity for major cost reductions in the highest efficiency solar cells - initially resulting in larger profits to SolarWorld but in the long run to lower prices.

To return to thin film, the two commercial technologies today are a-Si, where a-Si with nanostructured Si delivers a significant energy boost and CdTe, where the leading player is First Solar who reported yearly revenue growth of 388% on sales of low cost Cadmium telluride (CdTe) thin film solar modules, designed for large scale, grid-connected solar power plants. Manufacturing costs have been reduced to $1.25 per watt. First Solar will ship 100MW this year and has 100MW plants underway in Germany & Malaysia with the potential to ship 300MW in 2009.

It is interesting to note that Ken Zweibel who authored the Super Large Scale PV report at NREL joined a CdTe startup, Primestar, in December, 2006. Primestar had raised $6+ million by that time and was working to raise another $35+ million to build their first production line. In February 2007 http://www.primestarsolar.com announced an agreement to commercialize high efficiency photovoltaic (PV) technology developed by the U.S. National Renewable Energy Laboratory http://www.nrel.gov/pv/cdte

The agreement is to transition NREL's record 16.5% efficiency cadmium telluride (CdTe) technology to commercial module production. (Inside Greentech; Feb. 28, 2007) An overview of NREL's thin film CdTe PV is available at http://www.nrel.gov/pv/thin_film "CdTe thin-film technology is being actively commercialized. CdTe cell efficiencies are over 16% in the laboratory; commercial module efficiencies are likely to be in the 9% range in the first manufacturing plants. Companies have an array of inexpensive options to choose from in CdTe fabrication - 12+ ways to make 10% - efficient cells." http://www.nrel.gov/pv/thin_film/pn_techbased_cadmium_telluride.html

Investors along Sand Hill Road in Menlo Park are pouring money into solar nanotech startups, hoping that thinking small will translate into big profits.

Both inventors and investors are betting that flexible sheets of tiny solar cells used to harness the sun's strength will ultimately provide a cheaper, more efficient source of energy than the current smorgasbord of alternative and fossil fuels.

Nanosys and Nanosolar in Palo Alto -- along with Konarka in Lowell, Mass. -- say their research will result in thin rolls of highly efficient light-collecting plastics spread across rooftops or built into building materials. These rolls, the companies say, will be able to provide energy for prices as low as the electricity currently provided by utilities, which averages $1 per watt.

Other uses of nanotechnology foreseen by Konarka, Nanosolar and Nanosys include form-fitting plastic batteries for electronic devices like cell phones and laptops. While all three companies provide prototypes for large corporate research labs and government agencies, company representatives and investors are reticent to predict when nanotechnology-powered solar systems will be commercially available. Industry watchers, however, say that achieving mass production of these products may take five years or longer.

"We take the long view, although we're not averse to having products very quickly," said Bryan Roberts, general partner at Venrock Associates in Menlo Park, a leading Nanosys investor. "Whenever you're developing a novel technology platform, you're looking at a four- to six-year time frame rather than a three- to four-year time frame."

Despite the lack of commercial product availability, Konarka, Nanosolar and Nanosys have collectively raised more than $120 million since 2001, the year all three companies were founded. Recent investments include $7 million in debt financing for Konarka in June, making its total funding to date $38.5 million. Nanosolar recently announced more financial support in a Series B round of funding that secured $20 million in May. With previous investments of $7.25 million, it has secured a total of $27.25 million.

Both Konarka and Nanosolar have said they plan to use the money for new research and development facilities. Nanosys, which cited poor market conditions as the reason for withdrawing its IPO in August, has raised $55 million to date. The company's last round of funding in April 2003 secured $30 million.
Venture capitalist excitement for these new technologies reflects growth in the solar energy market as whole, say industry experts.

"The technology is maturing, and the industry is maturing. British Petroleum, Shell and the oil companies are all in this field," said David Wooley, vice president of the nonprofit Energy Foundation in San Francisco, a research group funded by major charitable trusts but not affiliated with utilities or energy producers.

A study released by the Energy Foundation in March suggests that the United States could produce 2,900 new megawatts of solar power by 2010 -- enough to power 500,000 homes -- if the cost is significantly reduced.

Solar energy ranges between $4 and $5 per watt. The report suggests market expansion will require $2 to $2.50. If the price breakthrough occurs, says Wooley, the report's assumed price structure represents a $6.6 billion annual market opportunity. The Energy Foundation report also says that solar energy could furnish much of the nation's electricity if available residential and commercial rooftops were fully utilized. According to the Energy Foundation, using available rooftop space could provide 710,000 megawatts across the United States, whose current electrical capacity is 950,000 megawatts.

"The market is obviously huge, demand is huge. Besides, (alternative energy) is imperative in the world we live in," said Bill Gurley, a general partner at Benchmark Capital in Menlo Park, an early investor in Nanosolar. As for recent growth in solar energy, Paula Mints, a senior analyst at the technology research firm of Strategies Unlimited in Mountain View, says that 14,000 photovoltaic megawatts were sold last year, representing 54 percent growth in the industry.

Mints says that VC interest in new energy technologies represents a positive development. "It's very healthy for the industry. They (venture capitalists) see the growth and the possibilities," she said. However, Mints also cautions against expecting immediate changes in the way energy is produced. She cites the long development history of conventional solar cells. "It took 20 to 25 years to commercialize (conventional) photovoltaics," she said. High production costs are among the reasons solar energy hasn't become a major source of electricity. The black, glasslike photovoltaic cells that make up most solar panels are usually composed of crystalline silicon, which requires clean-room manufacturing facilities free of dust and airborne microbes.

Silicon is also in short supply and increasingly expensive to produce, so high manufacturing costs are the main reason behind high wattage prices.

As a result, the cost of panel installation typically equals four to five years of expensive energy before production costs are recovered and systems begin paying for themselves.

With nanotechnology, tiny solar cells can be printed onto flexible, very thin light-retaining materials, bypassing the cost of silicon production. "Silicon is very capital-intensive. You don't need a clean room for plastic power where capital costs are one-tenth of silicon," said Raj Atluru, managing director at the venture capitalist firm of Draper Fisher Jurvetson in Menlo Park, a major investor in Konarka. Konarka, Nanosys and Nanosolar say their solar technology will reduce the time it will take consumers to recover production and installation costs to a matter of months.

In addition to being able to manufacture photovoltaic cells more quickly through printing, the companies also say that manipulating materials 100,000 times smaller than the width of a human hair will provide more light- collecting capabilities. Each printed nanostructure solar cell would act as an autonomous solar collector, and sheets of these products would have more surface area to gather light than conventional photovoltaic cells.
The companies also say that the printed rolls of solar cells would be lighter, more resilient and flexible than silicon photovoltaics.

Konarka, Nanosolar and Nanosys say that nanotechnology could make the price of electricity less expensive per watt.

• Current cost of solar energy, per watt: $4-$5
• Average cost of energy from traditional fossil fuel sources, per watt: $1
• Estimated cost of energy from nanotech solar panels, per watt: $2
• Total energy-generating capacity of the United States: 950,000 megawatts
• Potential total rooftop solar energy capacity in the United States: 710, 000 megawatts

Nanosolar also announced this week more than $100 million in funding from various sources, including venture firms and government grants. The company was founded in 2001 and first received seed money in 2003 from Google's founders Larry Page and Sergey Brin. Experts say Nanosolar's ambitious plans for such a large factory are surprising. "It's an extraordinary number," says Ken Zweibel, who heads up thin-film research at the National Renewable Energy Laboratory in Golden, CO. Most groups building new solar technologies "add maybe 25 or 50 megawatts," he says. "The biggest numbers are closer to 100. So it's a huge number, and it's a huge number in a new technology, so it's doubly unusual. All the [photovoltaics] in the world is 1,700 megawatts."

Today, the lion's share of solar cells are based on crystalline silicon, which is about three to five times too costly to compete with grid electricity, Zweibel says. Nanosolar's technology involves a thin film of copper, indium, gallium, and selenium (CIGS) that absorbs sunlight and converts it into electricity. The basic technology has been around for decades, but it has proven difficult to produce it reliably and cheaply. Nanosolar has developed a way to make these cells using a printing technology similar to the kind used to print newspapers, rather than expensive vacuum-based methods. Although the company expects to start selling solar cells next year, ramping up to full production will take more time. Meanwhile, high demand for solar cells worldwide will keep prices high, Roscheisen says. Eventually, however, he says the company hopes to attract more customers with lower prices, in several years reaching prices that make solar-power electricity competitive with the grid.

The costs of solar electricity is approximately 0.5 €/kWh in Central and Northern Europe and about 0.4 €/kWh in Southern Europe. Unfortunately, the feed-in tariff is significantly lower in most European countries. Also, for renewable energy sources feed-in tariff s up to 0.1 €/kWh are quite common, resulting for PV systems in recovery times beyond the technical lifetime. As a consequence, if the incentives on solar electricity are not sufficient to set up an economically feasible project there have to be other means of applying photovoltaics.

Especially in the built environment PV systems may have an additional function besides energy production, e.g.:

- A building element, such as a roofing element, part of the sun blinds, a façade element etc.
- An architectonic or aesthetic function, for instance as part of a sun roof or solar home, solar façade or included in the curtain wall.
- Part of the image building, showing environmental concern, of the company, owner or inhabitant

PV can be a profitable technology for converting sunlight into electrical energy. Incentives from local authorities, utilities, national governments and the European Union are widely available and promote the wide-scale integration of PV. The main reason for providing incentives is that solar PV is a clean energy source without generating greenhouse gases or other environmental pollution.

Germany and Spain are good examples where incentives significantly enhance the installation of grid-connected photovoltaic installations. In Germany the feed-in tariff is between 0.55 €/kWh, for small installations, mainly in the built environment, and 0.45 €/kWh for large plants including ground-based PV installations. In Spain, for PV installations up to 100 kWp, the feed-in tariff is approximately 0.40 €/kWh and it is about half this price for plants with higher installed power levels Other European countries have no specific feed-in tariff s for PV and generally speaking, incentives that are sufficient for other renewable energy sources are not satisfactory for economic operation of solar PV.

The solar photovoltaic (PV) market has demonstrated an aggregated global growth rate of more than 40 percent per annum over the last 10 years. Few industries can boast equivalent numbers, but solar PV has two big challenges ahead. Production costs need to go down in order for it to become more economically sustainable, while production capacity must continue to grow in order for PV to become a significant player in the global energy market.

In order to make the PV industry viable in the long run, the price of electricity per energy unit (cost/kWh) generated by a photovoltaic system needs to be comparable to the electricity market price during peak time. This cost target is 20 Eurocents/kWh. In order to achieve this, significant efficiency improvements are needed in the production process, as well as in balance-of-system costs such as rectifiers and installation.

Over the past four decades the semiconductor industry has developed enormous know-how about silicon in its different forms, as well as its interaction with other materials, such as aluminum and copper. This knowledge is very useful in analyzing the behavior of silicon-based solar cells and in optimizing their efficiencies. For example, the Belgium-based research institute IMEC is using knowledge from advanced deep-submicron research for its own work in thin-film PV cells. The understanding of epitaxial growth of silicon and its interaction with the substrate has enabled IMEC to grow large silicon crystals on low-cost substrates, enabling efficient PV cells at a significant lower cost.

Chip equipment manufacturers are also using their experience from the semiconductor industry as a basis for entry into the PV market. In September 2006 Applied Materials announced the acquisition of Applied Films, an expert in PVD systems for the deposition of thin coatings on different substrates. This technology is used to coat architectural glass with heat reflecting films or plastic foils with a thin layer of aluminum. This kind of technology is also applicable for the creation of thin-film PV systems on architectural glass, or in the future even roll-to-roll photovoltaic foils. The latter case is perceived as the ultimate low-cost PV system of the future.

However, entering the PV field is not necessarily a "free lunch" for semiconductor players because major research is needed to adapt semiconductor processes to the manufacturing needs of PV. Microelectronics has traditionally been a batch-based process which allows the manufacturer to process different devices in the same production line, keeping setup time to a minimum. In PV manufacturing, maximizing throughput at a predefined process quality is the main objective. Batch processes are inherently less efficient than continuous systems because of the queuing of batches between the process steps.

Since 2005, demand for silicon has increased significantly in the PV industry, even overtaking the capacity needs of the semiconductor industry. This has resulted in unprecedented high prices for silicon on the spot-market as well as PV production facilities working at less than full capacity. To address this problem, the PV industry saw the need to agree on long-term capacity forecasts in order to secure the raw material for their production lines. Because it takes about two years to build additional raw silicon capacity, it will likely be 2008 or beyond before silicon prices return to normal, which is between US$30-40/kg for solar-grade silicon. An additional advantage of this evolution is that more solar-grade production will become available, which will be cheaper than the semiconductor grade silicon because purity requirements are less stringent for the PV industry.

Another interesting development is the use of cheaper alternative techniques to create solar grade silicon. Some suppliers are commercializing a chemical purification method that claims to be significantly less expensive than traditional methods. Dow Corning announced recently that it is offering solar grade silicon derived from metallurgical poly-silicon feedstock. As production cost can be lower for this process, it offers opportunities to lower the overall cost of the PV cell once sufficient solar grade silicon feedstock is available. At this moment however it is still unclear what the effect on cell efficiency will be if such new material is used.

In 2007, Sharp of Japan was the only PV-cell manufacturer that had more than 400 MW/year production capacity, equivalent to about a 25 percent market share. Second was Q-Cells of Germany, with 160 MW/year. Q-Cells expects to cross the 400 MW/year threshold in 2007, as do Japanese companies Kyocera and Sanyo. Industry experts believe that within four years leading PV cell makers could be operating facilities with capacities of 500 MW/year, which is considered the threshold for the manufacture of economically viable PV cells.

Some analysts predict that a consolidation of current PV players will take place in the next 5 to 7 years. In the more distant future, we can expect to see a market consolidation in several parts of the value chain of the industry where a handful of players will produce the bulk of commodity solar cells, while smaller players will migrate to specialized niche products.

Another challenge facing the industry is the lack of technical standards. Because several of the larger PV cell manufacturers are vertically integrated they have developed proprietary in-house standards. However, as new players enter the market they will look to third party equipment suppliers in order to build a complete production line. This approach can only succeed if industry standards are agreed upon for the interfaces that are used by these systems. This can be in the form of simple agreements -- such as the height and other dimensions of the input and output for a continuous flow system -- or more sophisticated interfaces, such as machine-to-machine interfaces and their related software protocols for the advanced process control of the full production line.

Beyond standards, there are production improvements that can be made in order to increase the economic viability of PV solar cells. There is still scope to decrease the thickness of the wafers which in turn would increase the output of the industry. For example, if the silicon used for crystalline silicon cells can be reduced by 30 percent the PV industry could produce 8.5 GWp/year of capacity instead of 5.6 GW/year -- from the same amount of feedstock.

The approval for the Waldpolenz solar park was granted and meanwhile the construction work has started. Waldpolenz is a project of the Juwi group, based in Mainz, Rhineland-Palatinate, Germany. The new solar plant will be located on a former military air base near the communities of Brandis and Bennewitz, east of Leipzig (Saxony, former eastern Germany). Construction will be completed by the end of 2009. The plant will have a capacity of 40 MW. This is to be compared with the largest PV plant currently in operation, which is the 11 MW solar plant of Serpa, Portugal, inaugurated 2007.

The European Commission has drawn over a map of Europe the potential for electricity production using solar energy. The red spot - the biggest potential - lies over the south of Portugal, where the sun shines up to 3300 hours per year. With 11 MW, the PV plant opened today in Portugal (Serpa) is the biggest in the world, comprising 52 000 PV panels that will transform solar energy into electricity for about 8000 persons. The project was developed by a group of companies (General Electric, Power Light and Catavento) and will be followed by a new central just a few kilometres away with 62 MW.

Another company Eurosolar believes that, due to the huge potential, is more profitable to build smaller plants closer to the consumer. This company has a project to build 260 small stations in the south of Portugal in the coming years.

The European Commission's Joint Research Center in Ispra just published an interactive map of Europe (and Africa) showing the photovoltaics solar electricity potential. You can produce monthly and annual averages for specific locations and inclination angles.

While use is still limited, solar energy and photovoltaic electricity generation is regarded worldwide as the most promising sustainable energy source for the future.

The field of application of PV is manifold, for instance stand-alone systems, space applications, large ground-based power systems, various applications in the built environment and applications on small personal or household tools and gadgets. The most common manner to use solar PV is to feed the generated electricity into the utility grid. The emphasis of grid-connected PV is on the built environment, also referred to as building-integrated PV (BIPV). In Europe, the potential for PV in the built environment is immense, i.e. all roofs of industrial, office and residential buildings.

Another advantage of BIPV is that generation and usage of electricity are close to each other.
The majority of the photovoltaic cells and modules are produced from crystalline silicon material. Over the past decade the costs of PV systems diminished by about 70%, from approximately 15 €/Wp in the early nineties to 5 €/Wp in early 2000. Currently the price has increased again by 10 to 20% due to a shortage of crystalline silicon.

The PV market has high expectations from thin film (amorphous) cells and modules, requiring less scarce and costly silicon and a better prospect for cost reduction in the near future. Currently grid-connected PV is not yet cost-effective and incentives are needed to promote large-scale application of solar-generated electricity.

Worldwide solar energy is regarded as the most promising sustainable energy source for the future. The cumulative capacity of all PV systems around the world has reached almost 4,000 MW, half of which is installed in Europe.

The field of application of PV is manifold, for instance stand-alone systems, space applications, large ground-based power systems, various applications in the built environment and applications on small personal or household tools and gadgets. The total capacity has more than tripled since 2000. This large growth has been primarily in the grid-connected sector

Approximately 15% of the PV capacity is installed in an off -grid application. However the ratio between off -grid and grid-connected PV varies largely between countries; some install predominantly off-grid PV applications while others largely apply grid-connected PV. The most common manner to use solar energy is grid-connected. Especially in the built environment, usually only small and medium-sized systems, the economically optimal solution is to feed in behind the electricity-metering device.

By saving purchase costs of electricity from the utility, the value of the solar energy comprises not only the production fee but also the normally included fee for transport, management, profit and -- depending on the situation-- even VAT. The surplus of energy can be fed into the grid at a fee to be agreed upon with the utility.

The applications of solar cells are various. They have been used on roofs of dwellings for years. But lately other applications like sunblinds or PV systems as part of facades have been gaining ground. Sometimes they are also used as a sound barrier along the highway.

At the end of 2007, the total PV capacity installed worldwide was 3,700 MWp, almost 90% of which was grid-connected. In comparison with the year before this means 40% growth worldwide. It has to be noted that the statistics include only the IEA-PVPS member countries; however, the contribution of non-member countries is considered as negligible. The average annual growth of the worldwide PV market up to 2009 is projected to be 25 to 30%, then increasing to ~35% between 2010 and 2020.

Japan and Germany are dominating the solar PV installation market by the end of 2005 both countries counted almost 1,500 MWp, each representing 40% of the total installed PV power. Third on the list is the USA with almost 500 MWp installed by the end of 2005. The European countries are lagging behind, except for Germany. As a matter of fact, Germany might take over Japan's lead position by the end of 2008.

The following section distinguishes between PV cells and PV modules. The PV cell made from crystalline silicon is the base component producing solar electricity. A number of cells connected in series and mounted in a workable frame is called a PV module. PV modules are available in the dimensions 0.7x1.0 to 1.0x1.3 square meters. The yearly increase in production of PV cells and modules was in step with the yearly growth in installed PV power. In 2005 cell production increased more than 40% worldwide. For the first time not only the leading but also some small global producers doubled their production in 2005. The crystalline silicon used in the semi-conductor microprocessor industry is identical to the PV-cell material. The high demand in the microprocessor industry worldwide caused the shortage and an increase in cost price.

Before 2003 BP Solar dominated the market, but for a few years now Japanese companies have been world leader with about 50% of the PV cell and PV-module production market. The European companies, mainly in Germany and Spain, have a 20% market share but are growing faster than the Japanese competitors. The third largest market is the US. The US market only grew by 10% in 2005, with a growth of approximately 44% for the European market and 36% for the Japanese market at the other end of the scale. The production in the rest of the world is also expanding; for example BP Solar has set up production facilities in both Australia and India.

The leading European PV-cell producer is Q-cells, which more than doubled its production in 2005. Two other success stories are Schott Solar and Sunway, both from Germany. The numbers 1 to 4 on the world's list are all of Japanese origin: Sharp, Kyocera, Mitsubishi and Sanyo.

Thin film cells and modules are constructed by depositing extremely thin layers of photosensitive material on a low-cost backing such as glass, stainless steel or plastic. Thin fi lm cells off er the potential for cost reduction, as less semi-conductor material is required, less material is spoiled and lower production costs are envisaged. Especially the current shortage of crystalline silicon may enhance the development and production of cost-effective thin filmmodules. Nowadays, three materials are commercially available: amorphous silicon (a-Si), copper indium diselenide (CIS, CIGS) and cadmium telluride (CdTe). Of these materials amorphous silicon (a-Si) is most frequently installed.

The efficiency of the a-Si cells reaches 7-9%. The moderate efficiency of thin film leads to a low installed power level per square meter, i.e. 50 to 60 Wp/m2, for a fixed power quantity this requires almost double the covered area compared to crystalline silicon modules. Although in most applications the useful area is limited, this still leads to a preference for crystalline silicon over thin film.

The relatively low efficiency of thin film cells may be enhanced by using multiple (double or triple) layers of photovoltaic material instead of one single layer. The layers differ physically in that they are sensitive to different frequency bands of the sunlight spectrum. With triple junction thin film cells efficiencies up to 13% have been demonstrated. Other types of thin films can be produced using micro-crystalline silicon (μ-Si), cadmium telluride (CdTe), and copper indiumgallium diselenide (CIGS).

Besides crystalline silicon and thin film solar cells, two other cell types exist: high-efficiency concentrator cells and Spheral solar technology. Concentrator cells, abbreviated as CPV, technology uses relatively low-cost mirrors or lenses to concentrate the light before it strikes the photovoltaic material. The concentrator cells have an efficiency of 20 percent or more. Up to now a disadvantage is that for proper operation concentrator cells have to be pointed to the sun, requiring a tracking system which is expensive and especially in the built environment not always feasible.

Spheral solar technology uses minute silicon beads bonded to an aluminum foil matrix. This offers a major cost advantage because of the reduced requirement for silicon material. Spheral solar cells are relatively new in the solar market and have an efficiency of 11%.