SOLAR CELLS FOR TOMORROW

The Five separate market places are

Building integrated

Grid connected solar farms

Consumer products

Remote industrial

Remote communities

First generation

Based on crystalline silicon

Commercial sales of these started in the 70’s

The Future for First Generation PV

•Practical conversion efficiencies have now seemed to stabilize at around 15-18 % (with installed module efficiency 12-15%)
• Increases in efficiency tend to be matched by the cost of increased design/processing complexity
•Improvement of the cost-efficiency can therefore mainly be reached by reducing the cell and panel production costs

Second generation

Thin film semiconductors, silicon and non-silicon.

Commercial sales of these started in the mid 80’s

The Future for Second Generation PV

•Potential for cheaper production costs (but higher capital cost) by means of continuous deposition techniques.
•Cell efficiencies are now in the order 5-8 %, but substantial improvements are forecast, not so much for amorphous silicon, but more for CIGS.
•Environmental concerns about CdTe will affect its acceptability

Third generation PV

•Plastic solar cells (organic PV)

•Nano-technology cells

•Multiple junction thin polycrystalline films.

The first third generation products are just beginning to enter the market place.

The Present for Third Generation PV

•The first organic solar cell – DSC (Dye solar cell).

•Artificial photosynthesis system invented by Prof Michael Graetzel in Switzerland.

•First DSC product to be commercially available is the STI DSC Solar Facade Panel

•Laboratory results for DSC exceed 10%, with production models at around half that value.

The Future for Third Generation PV

•Organic or polymeric molecules as the PV active material.

•Recent results of 2-3% have been reported for blends based on substituted PPV polymer

•Designs for disc shaped phthalocyanine molecule as a film about 100 nanometers thick on a plastic substrate with a transparent electrical coating.

Fourth generation PV will derive from biology.

Fourth generation cells are expected to derive even more closely from photosynthesis.

Factors Driving Past Cost Reduction

Poly silicon price: $300/kg → $30/kg

Wire saws: now < $0.25/W

Larger wafers: 2” → 6”

Thinner wafers: 15 mil → 8 mil

Improved efficiency: 10% → 16%

Volume manufacturing: 1MW → 100MW

Increased automation: none → some

Improved manufacturing processes

The annual production of solar modules increases ten-fold every decade. The price of solar cell modules decreases by half every decade

2002: $3.00/W

2012: $1.50/W

2022: $0.75/W

SOLAR THERMAL TECHNOLOGIES AND CLEAN DEVELOPMENT MECHANISM

The clean development mechanism (CDM) would promote use of renewable energy technologies by providing benefits of reduction in emission of green house gases. The solar thermal technologies, especially the solar water heating systems, are becoming commercially viable in India. The CDM mechanism could push these technologies further. The major issues related to CDM in context of solar thermal systems in India are Addationality, Baselines, Cost, and Monitoring and Verification etc.

 

Additionality

The solar water heating systems are becoming economically viable in some of the sectors, in such case meeting the additionally criterion becomes critical.

 

Technical additionality

The solar water heating systems are fully manufactured in India. New mechanisms for increasing the adoption of solar water heating systems, like the energy services company and the third party financing would meet this criterion, as these concepts have not been demonstrated in India. Further, in case of medium temperature concentrating collectors for industrial and commercial applications in India, since this technology is not being used anywhere, implementing such a project satisfies this criterion.

 

Financial additionality

Though the solar water heating systems are becoming economically viable in some sectors, the initial costs are still higher thereby meeting the financial additionality criterion. In case of concentrating collectors, the costs are even higher (the systems have negative NPV against the present costs of solar system and fuel).

 

Offset additionality

The solar thermal technologies are zero emission technologies. The solar water heating system, for domestic application has potential of saving 1.5 tonne of CO2/annum. The emission reduction is 0.3 tonne/annum/m2 in case of oil replacement.

 

Baseline

The baseline for estimation of emission reduction will be different for different type of applications of solar thermal systems. In case of domestic solar water heating systems the baseline would be the electrical saving resulting from the SWHS and the emission reduction will depend on the average emissions for power generation, and the resource mix for power generation. In case of industrial systems, the existing boiler (or the boiler with maximum efficiency with present technology) will form the baseline.

 

Cost

The cost of CO2 varies form application to application from US$ 3/tonne of CO2 to US$ 12/tonne of CO2. The costs of CO2, given in table below, are estimated considering a minimum internal rate of return of 18% and 21%, for commercial and industrial systems and for domestic systems respectively, based on the cost of capital employed.

Cost of Carbon Dioxide

System /Application	Baseline	Cost of CO2  (US $/tonne)
Solar water heating system for domestic application	Domestic water heating using electric power. Emission saving based on resource mix for power  generation , presently 1.1 kg  CO2 emission /kWh	3- 5
Solar water heating system for industrial  application	Heating using boilers fired fuels  oil/diesel	5
Medium temperature solar thermal systems using solar concentrators.	Heating using boilers fired by fuel oil/diesel.	12

 

Monitoring And Verification

The distributed nature and smaller individual capacities of solar thermal systems increases the monitoring and verification costs. As per one estimate the monitoring and verification costs could be as high as 60% of the project cost.

Solar market in India

There are two distinct market segments for solar water heating systems (SWHS) in India, namely, (i) domestic and (ii) commercial and industrial. In commercial sector SWHS are used to meet the hot water demand e.g. in hotels and hospitals etc. while in

industrial sector, these systems are used for preheating boiler feed water or to meet the process heating requirements. In domestic sector, SWHS are used to meet household hot water requirements.

 

So far, the majority of installations in India are in the commercial and industrial sector, with 80% of the collector area installed in commercial and industrial sector, unlike Europe where the focus is mainly on the domestic sector. But as result of improved economics of solar systems, due to increase in electrical prices, the domestic market is increasing in India. As per MNES, the potential of solar water heating systems in the country is around 30 million m2 of collector area. The MNES policy (draft) has set the goal of installing 5-million m2 collector area during 2000- 2012, with equal distribution of collector area in domestic as well as commercial and industrial sector.

 

 

But this market penetration is still small when compared with some of the European countries like Greece, Germany, and Spain etc., especially when compared in terms of collector area installed per unit population. The installations per 1000 inhabitants are 5.1, 15.2 and 0.52 in Greece, Germany and India respectively.

 

In case of Indian market, the marketing, installation of systems and after sales service are responsibility of the manufacturer as the chain of dealers and installers has not been developed, which is very important for market penetration.

 

Although India has negligible quantum of installations as compared to potential, India ranks 5th in solar PV installations and 9th in solar thermal application installations in the world. Currently, India has 10–12 manufacturers producing about 100 MW of solar PV cells and about 20 manufacturers with total installed capacity of 120 MW in module manufacturing. India also has a large number of integrators-cum-service providers (about 80) with total capacity of about 245 MW. India exports 160 MW of solar PV products to With regard to solar thermal application, India has more than 200 manufacturers of solar water heaters and 40 of solar cookers. Also, 5–6 manufacturers are involved in producing solar drying, cooking, process heat, and air-conditioning applications. It is expected that  several players will enter solar thermal application development in the coming months.

 

Recently, several companies such as Tata BP Solar, Signet Solar, and Moser Baer have announced multi-million-dollar plans for investment in solar cell manufacturing capacities in the country. With announcement of the semiconductor policy in March 2007, it is envisaged that several multinational companies will enter silicon manufacturing as well as solar cell manufacturing.

Solar Thermal Technologies In India

Solar thermal technologies have a special relevance in India due to high availability of resource, average radiation is 4.5 – 6 kwh/m2/day with average 280 clear days. In view of the increasing energy demand in all the sectors there is immense potential especially in domestic and industrial sector to meet thermal energy demands.

 

Solar concentrating collector systems for process heating

The solar thermal systems which use concentrating collectors can deliver thermal energy at a higher temperature compared with solar flat plate collectors used in solar water heating systems. Major portion of thermal energy requirements in the Indian industrial sector lies in the temperature range of 100-250 0C which corresponds to the medium temperature range of solar thermal systems. Solar concentrating systems are best suited for such medium-grade thermal applications. Solar thermal energy has a number of attractive features, which make it a very desirable energy source. As far as the proposed technology is concerned, it is still in conceptual stage in India. Under the renewable energy policy has set the goal of installing 1000 systems of 10 ton/day steam generation capacity by year 2012.

 

Solar thermal power generation

A 50 kW capacity solar thermal power generation plant was installed at Solar Energy Centre, Gualpahari, Harayana, India in 1989. This plant is operating at a de-rated capacity presently. A 140-MW integrated solar combined cycle (ISCC) power plant is planned at Mathania near Jodhpur in the state of Rajasthan. The capacity of solaralone plant is 35 MW and balance 105 MW is based on naptha. The Rajasthan State Power Corporation Ltd. (RSEB), a recently established concern wholly owned by the state government, will implement the project. The world Bank/GEF had agreed to provide a grant of US $49 million while Government of Germany, through KfW, had agreed to provide composite loan of DM 250 million.

 

Solar pond

Salt-gradient solar ponds (low -cost solar collectors with integral storage) are both appropriate and relevant in the Indian context. In India, though solar pond research dates back to 1971, none of these ponds were connected to any end-use. The 6000 m2 Bhuj solar pond at the Kachch Dairy, Bhuj, was conceived as an R&D project to demonstrate the feasibility of using a salt-gradient solar pond to deliver industrial process heat. The construction of this pond was started in 1987 as a collaborative effort among Gujarat Energy Development Agency, Gujarat Dairy Development Corporation Limited, and TERI. The Bhuj solar pond started supplying hot water to the dairy in September 1993, saving about 935 MT of lignite a year, at full capacity utilization of the solar pond.

 

The economic viability of a salinity-gradient solar pond is governed by factors such as its size, proximity to sources of inexpensive salt/bittern and water, and land availability. The following niche areas have been identified after careful matching of these requirements with the deliverables: (1) process heating, (2) water desalination, (3) refrigeration, (4) production of magnesium chloride, (5) bromine recovery from the bittern, and (6) enhancement of the salt yield in the salt farms, etc.

  

Solar desalination

2

The simplest device for desalination using solar energy is solar still. To increase the efficiency various other techniques are also tried, multi-effect desalination is one of the possible solutions.

 

Solar still imitates a part of the natural hydrologic cycle in that the saline water is heated by the sun’s rays so that the production of water vapor (humidification) increases. The water vapor is then condensed on a cool surface, and the condensate collected as product water. Thus, solar stills are ideal to provide safe drinking water to isolated communities of small villages, islands, lighthouses and salt works. In solar stills plant the only moving part is the pump, to pump saline water from the well. These units can be constructed in modular form and provide a viable option of providing potable water for a single house or a group of families also.

 

The Central Salt & Marine Chemicals Research Institute (CSMCRI), Bhavnagar initiated research on solar stills in India in 1965. CSMCRI was the first organization to install large capacity solar stills in villages, lighthouses and island to supply drinking water. Apart from CSMCRI, other institutions, such as Bhabha Atomic Research Center (BARC), Bombay and Indian Institute of Technology (IIT), Delhi etc., too have been involved in this field. Solar still plants of capacity varying from 130m3/day to 8000m3/day of distilled water output were installed at various places in the period of 1965 to1983.

 

Apart from the basin type of solar still other designs of solar still were also tried to increases the efficiency e.g. active solar still coupled with flat plate collector, double basin solar still etc. To further increase the efficiency multiple effect desalination systems are also under development

 

Solar detoxification

Solar detoxification process involves the absorption of photons on the surface of a semiconductor, which acts as a catalyst and produces reactive radicals, mainly hydroxyl radicals. These radicals can oxidize organic compounds and completely mineralize them. Only photons with energy equal to or more than band gap of the semiconductor are absorbed on its surface. The energy needed to activate the semiconductor catalyst recommended for the solar detoxification process corresponds to UV component of the solar radiation.

 

Solar detoxification technology has shown great promise for treatment of toxic compounds in waste water and ground water. The major advantage of this technology is its ability to completely mineralize the organic chlorinated compounds into CO2 and HCl instead of transferring it from liquid stream to gaseous stream in carbon adsorption technology or incineration. Partial combustion during incineration some time results in the formation of compounds which are more toxic than the original compounds.

Role of Solar Power in India’s Energy Security

Climate change and energy security have become twin critical concerns of our time. The main option for mitigation of climate change is to transition to a low-carbon energy economy. Solar energy offers enormous potential for a much-needed quick transition. As of now, although grid-grade solar power may seem expensive, vast possibilities of demand-side management using viable solar energy devices exist even today. Emerging technologies like ‘concentrating solar power’ (CSP) offer avenues for competitive production of electricity by as early as 2015. Alongwith other renewables like wind, biomass etc, solar energy can play a vital role in solving or ameliorating the two most critical problems of our time. What is required is an imaginative, forward-looking, and bold policy initiative.

 

As suggested by President Kalam, if efficiency of solar photovoltaic can be increased from the present 15% to 50% without increasing the cost, we can have all the power we need at competitive costs by covering a small fraction of our land (the land required can be further reduced by putting photovoltaic cells on all rooftops).The surplus solar power during daytime can be used to split water to produce hydrogen that can provide electricity at night and can also be used to run motor vehicles using fuel cells as  engines.

 

Solar energy has a large potential in the country. The average solar insolation in the country is 6 kWh/m²/day. The present conversion efficiency of commercially available photovoltaic cells is less than 15%. With this efficiency, the potential of covering just 5 million hectares of land with photovoltaic cells is 1200 mtoe/year. The photovoltaic technology is proven but expensive and the cost of electricity exceeds Rs 20/kWh at present. Potential to reduce costs and increase efficiency exists and a technology mission for this is highly desirable.

 

Solar thermal is economical for water heating. Much of its potential has yet to be exploited. Appropriate policies need to be designed to accelerate the exploitation of this potential. Solar thermal generation has not found acceptance globally, though the potential to use it in hybrid systems may be there.

 

New domestic sources: The domestic resource base can also be expanded through developing hitherto poorly developed or new sources of energy. Some of these resources may require R&D to make them economical. Among these are …

 

Solar: Solar energy, if it can be economically exploited, constitutes a major energy resource of the country. Solar electricity generated through thermal route or through photovoltaic cells provides comparable amount of electricity per unit of collector area.

 

Both currently provide about 15% conversion efficiency. While it is clear that the ratio of capital cost to efficiency of energy conversion needs to be brought down significantly, solar thermal and solar photovoltaic route to electricity offers major scope for enhancing India’s energy security. Nanotechnology holds a hope for making a major breakthrough in solar photovoltaic technology. It is stressed here that solar water heating is cost effective for India today and can reduce India’s demand for oil, gas, and coal if pursued to meet the demand for hot water in industry and households.

  

Energy efficient buildings can be designed through solar passive architecture concepts so that energy requirements of heating and cooling could be reduced. Solar buildings that cost an additional 5%–10% have the potential of saving up to 30%–40% energy. Subsidy for preparation of DPR and construction of such buildings is proposed for continuation during the 11th Plan @ Rs 100/m² of covered area for which a provision of Rs 50 crore is proposed. In addition, Rs 25/m² is proposed for training and another Rs 25/ m² for information and publicity, for which there exists a subsidy provision of Rs 12.5 crore.

Polycrystalline silicon

Polycrystalline silicon (or polysilicon, poly-Si, or simply poly in context) is a material consisting of multiple small silicon crystals.

Polycrystalline silicon can be as much as 99.9999999% pure. Silicon is most often companioned with oxygen to form sand. When the oxygen is stripped from the silicon, crude polycrystalline silicon remains. Ultra-pure poly is used in the semiconductor industry, starting from poly rods that are five to eight feet in length.

Semiconductor grade (also solar grade) poly is converted to “single crystal” silicon – meaning that the randomly associated atoms of silicon in “polycrystalline silicon” are converted to large “single” crystals of silicon. Single crystal silicon is used to manufacture 99% of all electronic devices. The devices are used in watches, refrigerators, microwaves, televisions, radios, communications equipment such as cell phones, and controls for cars, ships, aircraft, missiles, and atomic weapons.

In microelectronic industry (semiconductor industry), poly is used both at the macro-scale and micro-scale (component) level.

At the macro scale, polysilicon is used as a raw material entering a process in which single crystals are grown ( Czochralski process, Bridgeman technique).

At the component level, polysilicon has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it is deposited using low-pressure chemical-vapour deposition (LPCVD) reactors at high temperatures and is usually heavily N or P-doped.

More recently, intrinsic and doped polysilicon is being used in large-area electronics as the active and/or doped layers in thin-film transistors. Although it can be deposited by LPCVD, plasma-enhanced chemical vapour deposition (PECVD), or solid-phase crystallization (SPC) of amorphous silicon in certain processing regimes, these processes still require relatively high temperatures of at least 300°C. These temperatures make deposition of polysilicon possible for glass substrates but not for plastic substrates. The drive to deposit Polycrystalline silicon or poly-Si on plastic substrates is powered by the desire to be able to manufacture digital displays on flexible screens. Therefore, a relatively new technique called laser crystallization has been devised to crystallize a precursor amorphous silicon (a-Si) material on a plastic substrate without melting or damaging the plastic. Short, high-intensity ultraviolet laser pulses are used to heat the deposited a-Si material to above the melting point of silicon, without melting the entire substrate. The molten silicon will then crystallize as it cools. By precisely controlling the temperature gradients, researchers have been able to grow very large grains, of up to hundreds of micrometers in size in the extreme case, although grain sizes of 10 nanometres to 1 micrometre are also common. In order to create devices on polysilicon over large-areas however, a crystal grain size smaller than the device feature size is needed for homogeneity of the devices.

Another method to produce poly-Si at low temperatures is metal-induced crystallization where an amorphous-Si thin film can be crystallized at temperatures as low as 150C if annealed while in contact of another metal film such as aluminum, gold, or silver

The main advantage of polysilicon over a-Si is that the mobility of the charge carriers can be orders of magnitude larger and the material also shows greater stability under electric field and light-induced stress. This allows more complex, high-speed circuity to be created on the glass substrate along with the a-Si devices, which are still needed for their low-leakage characteristics.

When polysilicon and a-Si devices are used in the same process this is called hybrid processing. A complete polysilicon active layer process is also used in some cases where a small pixel size is required, such as in projection displays.

Polycrystalline silicon (used to produce silicon monocrystals by Czochralski process)

 

A polycrystalline silicon rod made by the Siemens process

Polysilicon is a key component for integrated circuit and central processing unit manufacturers such as AMD and Intel, however it is also a key component of solar panel construction. The photovoltaic solar industry is growing rapidly but is likely going to be very limited in 2006-2008 due to severe shortages and allocations of the polysilicon material. Currently in 2006, 30% of the world’s supply of polysilicon is being used for production of renewable electricity solar power panels.

Major Polysilicon manufacturers include Hemlock Semiconductor, Wacker Chemie, REC, Tokuyama, MEMC, Mitsubishi (Japan and America) and Sumitomo-Titanium, as well as several small sites in China and CIS. The first 7 companies cover over 75% of the worldwide production capacity of polysilicon.

Silicon For Solar

Silicon is the second most common element in the Earth’s crust, comprising 25.7% of the Earth’s crust by weight. It was discovered in 1824 by the Swedish chemist Jons Jakob Berzelius. It is shiny, dark gray with a tint of blue. Silicon, atomic number of 14, is a semi-metallic or metalloid, because it has several of the metallic characteristics. Silicon is never found in its natural state, but rather in combination with oxygen as a silicate ion (SiO₄) in silica-rich rocks such as obsidian, granite, diorite, and sandstone. Feldspar and quartz are the most significant silicate minerals. Silicon alloys with a variety of metals, including iron, aluminum, copper, nickel, manganese and ferrochromium.

The name silicon comes from the Latin word silicis which means flint.

Silica is processed into two intermediate products- silicon and ferrosilicon. Silicon is known in the ferroalloy and chemical industries as “silicon metal.” The ultra pure form of silicon (>99.99% Si) is distinguished from silicon metal by the term “semiconductor-grade silicon.” The terms “silicon metal” and “silicon” are used interchangeably.

Silicon is used in ceramics and in making glass. Ferrosilicon is crushed into a variety of forms and sold as bulk metal. Depending on its intended use, it can be mixed with aluminum and calcium. It is a very heavy alloy. When it comes into contact with moist air or water, an explosive chemical reaction occurs in which hydrogen is released. Consequently there are very strict laws about the shipping of ferrosilicon it must be kept perfectly clean and dry.

Silicon conducts electricity, but not as well as a metal such as copper or silver. This physical property makes silicon an important commodity in the computer manufacturing business.

Ferrosilicon accounts for 53% of the annual silicon consumption in the United States; pure silicon accounts for the remaining 47%.

Silica is in human connective tissues, bones, teeth, skin, eyes, glands and organs. It is a major constituent of collagen which helps keep our skin elastic, and it helps calcium in maintaining bone strength. Silica dust in mines has caused silicosis or a lung disease in miners. Wetting the area being mined and application of good ventilation has reduced the danger of lung disease. Some organisms like sponges and some plants use silicon to create structural support.

Sources

Silicon compounds are the most significant component of the Earth’s crust. Silicon is recovered from an abundant resource: sand. Most pure sand is quartz, silicon dioxide (SiO₂). Since sand is plentiful, easy to mine and relatively easy to process, it is the primary ore source of silicon. Some silicon is also retrieved from two other silicate minerals, talc and mica. The metamorphic rock, quartzite, is another source (quartzite is metamorphosed sandstone). All combined, world resources of silicon are plentiful and will supply demand for many decades to come.

The United States has plentiful sand, quartzite, talc and mica resources. The majority of the silica produced in the U.S. is produced East of the Mississippi River and in the Northwest. The U.S. also imports silicon from Norway, Russia, Brazil, Canada, and from a number of other countries.

 

Most silicon chips are made of single crystal silicon, which has a very low resistance to electron flow. However, silicon can exist in different forms (just as carbon can exist in the form of diamond, graphite, soot and buckminsterfullerine). As well as single crystal silicon, other forms are Poly-silicon and Amorphous silicon.

Polysilicon (p-si) is short for Polycrystalline Silicon, which is a form of silicon composed of many crystals, as opposed to Amorphous Silicon (a-si), which is an unordered form with a random internal structure. Electrons have a hard time moving quickly in amorphous silicon so the transistors in active matrix displays have to be relatively large, blocking quite a lot of light, and are relatively slow to switch. Polysilicon would be more efficient so why, then, do most active matrix LCD panels use a-si?

Making an LCD requires the silicon to be deposited on a transparent material (the substrate) and depositing p-si proved to require too high a temperature (typically 650 deg plus) to make it a practical proposition, so attention switched to a-si which could be deposited at a much lower temperature (380 deg ) allowing glass to be used as the substrate.

The speed of p-si was a strong lure, however, and eventually P-si panels were produced using quartz glass, which, though very expensive, could stand the heat of the deposition process. Small panels using quartz are used in LCD projectors and some other small applications such as camcorders and digital cameras. A major advantage of getting poly-silicon onto the glass is that the driver chips can be produced in the same process, saving cost and space and improving reliability.

Various companies have developed methods of using lasers to create p-si transistors on glass. The process is that amorphous silicon is deposited on the glass at low temperature and the silicon is then heated with a very short pulse from a laser that avoids heating the glass excessively.

As new, cheaper methods, using still lower temperatures, are developed to produce p-si displays, a-si displays will be replaced by p-si units which require less power, are brighter, more responsive, have a higher resolution and require less external circuitry to make them operate.

Uses

Ferrosilicon alloys are used to improve the strength and quality of iron and steel products. Tools, for instance, are made of steel and ferrosilicon.

In addition to tool steels, an example of “alloy steels,” ferrosilicon is used in the manufacture of stainless steels, carbon steels, and other alloy steels (e.g., high-strength, low-alloy steels, electrical steels, and full-alloy steels).

An alloy steel refers to all finished steels other than stainless and carbon steels. Stainless steels are used when superior corrosion resistance, hygiene, aesthetic, and wear-resistance qualities are needed.

Carbon steels are used extensively in suspension bridges and other structural support material, and in automotive bodies, to name a few. Silicon is also added to aluminum to create a stronger alloy. The largest consumers of silicon metal are the aluminum and chemical industries.

Silicon is used in the aluminum industry to improve castability and weldability, not to add strength as noted in the text. Silicon-aluminum alloys tend to have relatively low strength and ductility, so other metals, especially magnesium and copper, are often added to improve strength.

In the chemicals industry, silicon metal is the starting point for the production of silianes, silicones, fumed silica, and semiconductor-grade silicon. Silanes are the used to make silicone resins, lubricants, anti-foaming agents, and water-repellent compounds. Silicones are used as lubricants, hydraulic fluids, electrical insulators, and moisture-proof treatments.

Semiconductor-grade silicon is used in the manufacture of silicon chips and solar cells. Fumed silica is used as a filler in the cement and refractory materials industries, as well as in heat insulation and filling material for synthetic rubbers, polymers and grouts.

Other silicon materials are used in the production of advanced ceramic materials, including silicon carbide, silicon nitride, and sialons. Silicon carbide is also used as an abrasive material, a refractory agent, and in steel manufacturing.

Substitutes and Alternative Sources

There are relatively few options to replace silicon in its applications. Germanium and gallium arsenide can be used as semiconductors in place of silicon. In some applications, a small number of metal alloys, such as silicomanganese and aluminum, can substitute for ferrosilicon.

A concentrated power boost for solar energy

Concentrating solar power, which has been around for decades,is one of the most promising techniques being tried today to make solar electricity more cost effective.

The concept is simply to focus light in order to boost electricity output. But there’s a wide disparity in the types of solar concentrators being built, from utility-scale solar thermal projects to specialized photovoltaic solar panels that could one day go on a homeowner’s roof.

In concentrating photovoltaics, a design being pursued by a number of solar companies seeking to lower the cost per kilowatt the sun can deliver.

What are the primary forms of solar concentrators?

Solar concentrators use lenses, mirrors, parabolic dishes or other optics to concentrate energy from the sun. Very often, they have a mechanism so that these devices track the path of the sun during the day. In solar thermal applications, troughs or large mirrors amplify sunlight to create heat, which heats a liquid or gas that turns turbines to make electricity. Solar thermal is used for large-scale power plants operated by utilities, usually in the desert.

This same technique is also being pursued in conjunction with photovoltaic solar cells, which convert light to electricity. Among concentrating photovoltaic companies, there is a wide range of approaches. There are systems designed for utilities’ central power stations, mounted concentrators that can go on the roof of an office building, and those that are the same size as traditional solar panels.

Solaria CEO talks solar

Suvi Sharma, CEO of solar start-up Solaria, on cutting-edge solar technologies and a recent investment by solar cell maker Q-Cells in his company.

Why is there interest in concentrating photovoltaics?

Three words: the solar constant. The sun radiates about a kilowatt of energy per square meter on the surface of Earth, according to B.J. Stanberry, CEO of HelioVolt. There are 2.6 million square meters in a square mile. Thus, every square mile gets about 2.6 gigawatts. It’s a number that just can’t be increased.

Concentrators essentially try to artificially increase the constant by virtually expanding the size of solar cell with mirrors or lenses. The quality of the concentrator is rated by how much solar real estate it can cram onto a solar cell without creating things like shadows or interfering with other solar cells.

One number you hear a lot is how many suns a concentrator replicates. GreenVolts, which is commercializing technology licensed from Lawrence Livermore National Laboratory, has a concentrator it says can deliver the equivalent of the energy of 625 suns to a solar cell.

Why not just improve solar cells?

That’s also being done. Without concentration, the efficiency of commonly used solar cells made from silicon tops out at around 22 percent. Physics says that crystalline silicon PV cells will top out at around 29 percent.

High-efficiency cells, historically used for satellites or spacecraft and made from different layers of materials, can exceed 40 percent efficiency or more, but this pushes up the price. Focusing more light onto cells makes them more productive.

The relatively high cost of photovoltaic material–the most common being silicon, which is in short supply–represents a significant cost to an overall solar power device. Using concentration, manufacturers are looking to lower the overall cost per kilowatt-hour of a solar power purchase. People often believe that since most solar cells are made of silicon, panel manufacturers inherit Moore’s Law, which stipulates that the performance of microprocessors double every 24 months. But the same dynamics don’t play out, solar industry executives say. Instead, the solar industry is focused exclusively on cost and making solar power competitive with traditional fossil fuel-based power generation. That’s why many companies, including a number of start-ups, are trying to concentrate solar power, along with thin-film solar cells made from other materials, and lowering their manufacturing costs.

OK, concentrating light onto solar cells means more power output. But does that mean it’s more cost-effective?

Not necessarily. Concentrating photovoltaic systems often require lenses or mirrors to focus the light onto solar cells. To maximize the amount of light they receive, high-concentration systems can be mounted and need a motor so that the cells track the movement of the sun over the course of the day. So although manufacturers may be saving money on solar cells, the additional equipment can raise the price.

But solar concentrators stand to benefit from the incremental improvements in solar cell efficiency. Brad Hines, the chief technology officer of solar concentrator company Soliant Energy, says that concentrators are becoming more cost-effective as cell efficiency climbs. A company can build a concentrator that’s cost-competitive with traditional solar panels when cells are 16 or 17 percent efficient, he figures. Once manufacturers start using cells with efficiency above 18 percent, there’s a significant cost advantage. “When I make a concentrator, it costs me the same to build the frame and the tracking system and optics regardless of the solar cell I put in,” Hines said. The same basic math holds true with high-efficiency cells, even though they are more expensive, he says.

 

So what do these solar concentrators that use photovoltaic cells look like?
Designs vary greatly. One could segment the industry into high-, mid- and low-concentration categories.

An example of a high-concentration company is SolFocus, a venture spun off from Xerox’s Palo Alto Research Center. The company is using a series of curved lenses that focus light on high-efficiency triple-junction (i.e. multi-material) cells. The company’s “honeycomb” structure places 16 of these dishes on a flat panel, which is mounted on a pole. This design magnifies light by 500 times normal sunlight, according to the company. There are a number of companies pursuing this basic design of concentrating solar arrays, essentially large assemblies with several panels. When scaled up into many very large arrays mounted on the ground, they can be used for multi-megawatt power plants. Or, one or a few arrays can be used on the rooftop of a commercial building to supplement their power consumption.

Energy Innovations is another company targeting the flat commercial rooftop business, but with a different design. It, too, uses high concentration–on the order of 800 times–and high-efficiency cells with its Sunflower product. It has a tracking system that can follow the sun’s altitude and azimuth (its angle on the horizon) and a specially designed mounting system meant to keep a low profile on the roof.

Makers of low-concentration panels are satisfied with much lower magnification–as low as two or three times concentration. Companies pursuing this general track are Soliant Energy, Solaria and Silicon Valley Solar, which recently acquired NuEdison. Although they have different optical techniques for directing sunlight, the end product is meant to have the same shape and size as traditional solar panels. That should make it easier for installers and distributors familiar with solar panels able to work with these products without any special training or mounting equipment.

What are the tradeoffs of this approach?

Magnifying light many times, of course, creates a lot of heat, which lowers the efficiency of solar cells. As a result, high-concentration manufacturers often use specialized cooling systems. In addition, large-scale systems with several mounted arrays can be big civil engineering projects. As noted, all the additional equipment and engineering involved in building an entire system that tracks the sun during the day can raise the overall cost of the system, even if manufacturers are being thrifty with solar cells.

Very large concentrating photovoltaic arrays, which could be used for a medium-size power plant, are designed mainly for very sunny environments like the desert of the southwestern United States, according to solar industry executives.

Because they align with the sun very closely, a concentrating photovoltaic power plant will not perform as well on cloudy days, whereas a power field with hundreds of traditional flat-plate solar panels could still generate a significant amount of electricity, said Nancy Hartsoch, vice president of marketing at CPV start-up SolFocus.

“Put us in the Mojave Desert and we’ll significantly outperform flat-plate photovoltaics. Put us in a power field in Germany and we won’t,” she said.

Because concentrating photovoltaic is a relatively new technology, Hartsoch expects that utilities will use a combination of flat-plate solar panels with concentrating photovoltaic arrays in the near term.

Are these concentrating photovoltaic systems commercially available?

Many of these systems are being tested now with utilities and commercial customers. A number of vendors have promised commercial availability of their systems late this year or next year. It doesn’t appear that panels aimed at residential rooftops will be coming in the near future.

How will things look a few years from now?

With so much investment and engineering being poured into concentrating solar power, it is likely to endure once products are commercially available. What is less clear is which designs will win out. Solar industry executives expect that different approaches will find their market niches, such as smaller power plants for utilities looking to boost the amount of renewable energy they produce to meet government mandates. For on-site power generation, rather than centralized power plants, the success of commercial customers will help sort out the winners and losers, as they represent the mass market.

Apart from design, one of the major factors of success is manufacturing processes, argues Suvi Sharma, CEO of Solaria. With so much competition among solar companies–as well as other forms of electricity generation–the cost-effectiveness of the end product will hinge heavily on a provider’s scale and operational efficiency, he said.

“Not every Silicon Valley company getting funding will be standing five years from now, but there will be some great successes,” said Sharma. “Once things get more cost sensitive and commoditized, there will be a weeding-out process…it’s very important to bridge the gap from a technology development phase to mass production.”

Rising Sun

The aggregate market valuation of these 28 solar products manufacturers in last year was $118 billion. Investors have been snapping up stocks of solar companies from around the world.

Company/Country	Market Capitalization ($U.S. bil)
REC/Norway	$17.40
ORKLA/Norway	16.7
MEMC/US	12.4
WACKER/Germany	9.9
Q-CELLS/Germany	9.5
FIRST SOLAR/US	7.3
SUNPOWER/US	6
SUNTECH/China	5.8
SOLARWORLD/Germany	5.5
LDK/China	4.5
TOKUYAMA/Japan	4
DC CHEMICAL/South Korea	3
CONERGY/Germany	2.6
YINGLI/China	2
MOTECH/Taiwan	1.8
JA/China	1.5
TRINA/China	1.4
ECD/US	1.2
ERSOL/Germany	0.9
EVERGREEN/US	0.9
RENESOLA/China	0.7
E-TON/Taiwan	0.7
SOLON/Germany	0.7
SOLARFUN/China	0.5
SOLAR MILLENNIUM/Germany	0.5
ATS/Canada	0.4
CHINA SUNERGY/China	0.3
CSI/China	0.2
TOTAL	118.1

 

Sources: Bloomberg Financial Markets; FT Interactive, Reuters Fundamentals and Worldscope via FactSet Research Systems; U.S. Department of Energy.

 

Sources: Bloomberg Financial Markets; FT Interactive, Reuters Fundamentals and Worldscope via FactSet Research Systems; U.S. Department of Energy. Sources: Bloomberg Financial Markets; FT Interactive, Reuters Fundamentals and Worldscope via FactSet Research Systems; U.S. Department of Energy.

Solar power is still more expensive than fossil fuel generated electricity. But the gap is closing. The rule of thumb in the solar business: Every time the volume of solar cells doubles, its cost drops by 20%. Governments in Germany and Japan have consequently offered generous subsidies to local consumers and companies who invest in building solar power. Those subsidies have sparked booms.

According to the International Energy Agency, by the end of 2005 Germany led the world with the most installed photovoltaic systems (1.43 million kilowatts) followed by Japan (1.42 million kilowatts). The U.S. was a distant third (480,000 kilowatts)..)

The race is on to find a way to make solar grow up so that it can compete, dollar-per-watt, against any fuel on the planet.

The long-term forecast? Bright, with big patches of innovation ahead.

Michael Splinter was raised on the most powerful incantation in the tech industry, Moore’s Law, which roughly holds that computing power per dollar doubles every two years. During his 20 years at Intel. Splinter saw this law deliver exponentially better products and profits.

Now, as chief executive of Applied Materials, the biggest pick-and-shovel maker for the semiconductor and flat-panel display industries, Splinter, 56, wants to forge a sunny-side-up version of Moore’s Law. “Can we, with our customers, drive down the cost per watt of photovoltaics?” Splinter asks. “We’ve got to.”

Currently photovoltaics cost $2 to $3 per watt to build, down from $22 in 1980. Splinter thinks he can help drive the cost of solar to under $1 a watt. At that price, even after adding a dollar or two per watt of installation costs, solar power would rival grid-delivered fossil fuel power. (Bear in mind that watts here are measured at midday peaks. Even in California an installation rated at 1 kilowatt will produce only 1,600 kwh a year.)

Ambitious enough to be on Intel’s shortlist of future chief executives, Splinter leaped at the chance to run his own show at Applied in 2003. The growth in solar captured Splinter’s attention early on. Slowdowns at computer chip makers, who buy nearly all of Applied’s equipment, hit hard. The $9.2 billion (revenue) company has a price-to-earnings ratio below that of Kraft Foods The solar cell manufacturing industry for years made do with hand-me-down tools from the computer chip industry. But last year solar cell manufacturers bought more silicon wafers than chipmakers–and solar’s demand for wafers is growing three times as fast as demand from the rest of the electronics industry. Applied will likely hit $400 million in contracts for solar manufacturing gear by year-end; Splinter wants $1 billion by 2009.

Applied intends to trim the industry’s costs in four ways: boost solar factory throughput, improve the productivity of every tool, cut materials costs by using photovoltaic materials more sparingly and raise solar cell efficiencies. Splinter has already spent close to $1 billion to hire hundreds of people for his solar group, buy two small thin-film equipment makers and invest in a silicon wafer firm in California.

Charles Gay, who is leading Applied’s solar business, obsesses about speed. Computer chips are made in batches; solar cells are produced continuously. Coating tools once used to put films on sheets of glass are being tweaked so they can also rapidly coat thousands of individual wafers. Thin-film solar makers want to work with the 64-square-foot sheets of glass used by Applied’s LCD customers, but solar glass is four times as thick as display glass. So Applied is strengthening the arms of the robots it sells to hold glass sheets. “We’d like to move one ton of silicon wafers through a line in an hour,” Gay says. At that speed one factory could produce a gigawatt of solar modules per year, ten times as much as the U.S. is now installing. “This is like the 1970s in the computer chip business,” says Splinter, flashing a 200-watt smile.

 

Solar power is the ultimate alchemy

Over the next 25 years solar is expected to be the fastest-growing alternative source of electric energy. But it is complex, expensive magic and has burned many entrepreneurs and investors in the past. With clean power in great demand, and fresh capital coming in from governments and capital markets, the solar economy is again humming with new materials, ideas, designs and business plans. Solar now meets only a 0.1% sliver of our electricity needs, but opportunities for growth and invention are bright.

Enthusiasts like to point out that an hour of sunlight packs enough energy to power the entire world for a day. Or this: If you could cover an area about the size of Massachusetts in the Southwest U.S. entirely with solar cells, you could generate enough electricity to quench America’s need for electric power.

But building solar cells, the devices that convert photons from the sun into streams of electrons and electricity, is complex, expensive magic to pull off–and has burned many entrepreneurs and investors in the past.

Today, solar energy contributes about a tenth of a percent (0.1%) of the U.S.’s electricity needs. Both Germany and Japan, where government have provided more subsidies, use a larger percentage of solar power.

Among alternative energies, solar energy is a child starlet: alluringly clean, endlessly promising-yet petulantly expensive and hard to manage. For investors, solar energy stocks have been an astonishing story this year: The aggregate market value of a group of 28 solar companies now tops $118 billion.

On average, the value of those companies has risen almost by half since January. Driving those market valuations is the expectation of more growth ahead: Analysts both in industry and in the government anticipate that solar will be the fastest-growing alternative source of electric power over the next 25 years.

How will it happen?

This year’s E-gang, our ninth annual look at technology innovation, offers a snapshot of some of the inventions and entrepreneurs that are part of this solar boom. The work starts with tool makers–those companies that are building and refining the equipment needed to make solar cells.

Then there are inventors, who keep trying to squeeze more power from every ray of sunlight. Manufacturers of different versions of solar power vie to have their approach designated as the most promising. There are plenty of contestants: the traditional approach of building crystalline solar cells, pairs relatively higher efficiency with higher costs.

There are thin-films of solar materials, some made from exotic combinations of materials, others still relying on silicon. Then there is one of the oldest ways of getting power out from the sun: solar “thermal” installations, which absorb the sun’s energy, transforming it into heat so it can boil water and run a turbine.

Finally there are those who innovate through their business models and strategic approach–the installers turned financiers, who help customers juggle the costs and risks of investing in solar. None have had more experience in this than Germany’s solar installers, who are cashing in on their government’s generous subsidies for solar power. The stock market has also been a boon to many Chinese companies, which have jumped into the business of building everything from solar wafers to finished panels.