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Solar Technologies

According to John Thronton, a former engineer at the National Renewable Energy Lab (NREL) in Golden, Colorado, the cost of manufacturing photovoltaic cells has been decreasing, but the market price has remained level or slightly increasing because worldwide demand far exceeds supply.  The U.S. exports 70-75% of its photovoltaic products.  In the long run, however, the high demand will lower prices because it presents a profitable business opportunity, which means there will be a race to manufacture, thus increasing supply.

These claims are based mainly on the traditional semi conductor-grade crystalline-silicon wafers, which dominate the solar technology market. These traditional silicon wafers are expensive to manufacture because of the high energy manufacturing inputs and the high loss of material during production.  The cost of production is one of the impediments in the investment in and the output of solar technology.  According to Thornton, the promising thin-film alternatives could revolutionize the marketing of solar technology.

One type of thin-film technology, the most advanced and widely used, uses amorphous silicon.  An amorphous silicon thin-film solar cell contains only one-three hundredths (0.33%) of the material and takes only one-third (33%) of the energy to produce than the crystalline-silicon PV cells.  As a result, the cost of manufacturing these thin-film cells is much cheaper relative to traditional crystalline-silicon wafers.  One of the drawbacks, however, is that their efficiency is lower.  The best-stabilized efficiencies achieved for these types of solar panels in the U.S. are about 8%, whereas crystalline-silicon cells have efficiencies between 13% and 15%.

However, efforts to find ways to make thin-films more efficient are underway.  Copper indium diselenide (CIS) is a more recent thin-film PV cell material.  CIS modules currently on the market reach an efficiency of more than 11%.  NREL scientists in the laboratory achieved an efficiency of up to 19.2%.  Thus, research now focuses on increasing efficiency, reducing costs, and raising the production yield of CIS panels.  Another material, CdTe, is also promising because it’s less expensive than CIS.  Cells containing this material have reached an efficiency of up to 11%, so now research focuses on improving efficiency and reducing panel degradation.

If progress continues, Franz Karg, research manager at the Shell Solar facility in Munich, Germany, predicts that thin-film technology will eventually cut the present production cost in half per unit kilowatt peak (kWp). This means that a complete system’s cost will be reduced by 35% or more.  And Thornton believes the promise of thin-film technology could significantly reduce the price of solar technology by 2012 in Colorado.

Despite these prospects, there are still many challenges in mainstreaming thin-film technology.  For one, cost-effectively mass-producing thin-film cells is hard due to the difficulty of coating large areas of glass.  Also, thin-film technologies are fairly new, the very first type having only been in the market for about 15 years; therefore, it is hard to compete with the older, more reliable crystalline-silicon cells.  Present economics greatly hinders investment in thin-films.

Meanwhile, Colorado is offering rebates to those who want to install solar systems.  Thornton said it cost him about $5000 to install a 2.2 kW system in his home after an $11,500 rebate from Xcel Energy and a $2000 federal tax credit.  If national and international collaborations between industry and government continue, research could revolutionize the marketing of solar technology and change the economics to reduce the cost even more, not only in Colorado but nationally and internationally as well.

Colorado Public Radio
The Industrial Physicist (

Solar Photovoltaic (PV) Technologies

The primary types of solar photovoltaic (PV) technologies fall into four different generational categories, which include:

  • Monocrystalline silicon (1G)
  • Thin-film deposits (2G) of semiconductors based on polycrystalline silicon, amorphous silicon, micro-crystalline silicon, cadmium telluride, or copper indium selenide/sulfide
  • Photoelectrochemical cells, polymer solar cells, and nanocrystal solar cells (3G)
  • Composite PV technology, which utilizes polymers with nano particles mixed together to make a single multispectrum layer (4G)

Today, we’ll take a brief look at the most popular technology currently in use in the PV industry: monocrystalline silicon.

Monocrystalline silicon
Monocrystalline silicon cells are generally referred to as silicon wafer-based solar cells, and they represent the so-called first generation of photovoltaics.

Monocrystalline cells are produced by slicing silicon wafers from a single crystal boule (high-purity silicon). Monocrystalline technologies currently yeild the highest levels of solar conversion efficiency of turning sunlight into energy. Most monocrystalline cells on the market today offer around 20% efficiency, while the theoretical maximum conversion efficiency is about 37%.

Monocrystalline silicon cells are costly to produce due to their capital-intensive manufacturing methods, which have been carried over from the silicon-based microprocessor industry. Due to this carry over, the quality standard for monocyrstalline silicon cells is often much higher than needed in photovoltaic (PV) production.

Monocrystalline silicon cells account for more than 85% of the current production of solar cells, making them the dominant technology in today’s photovoltaic market.

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