Energy from the Sun
Direct solar energy is captured and converted into electricity using two technologies. In the first, the sun's heat is captured and concentrated using reflectors and then is used to heat liquids (sometimes converted to steam), which in turn rotate engines and turbines that generate electricity. (These are called concentrated solar power (CSP) units). This technology has been used with great success in the southwestern U.S. Home rooftop solar water heaters fall into this category as well.
The second technology directly converts the sun's energy into electricity. (These are called photovoltaics or solar cells). Early solar cells used very pure, relatively thick pieces of silicon as their primary component. But as competition from computer chip manufacturers has increased for the limited amount of this kind of silicon that is produced, the price of silicon has risen significantly (and will likely to continue to rise). As a result, the most important issue and limiting factor for installation of solar cells has become cost.
With the international interest in renewable energy and the significant incentives that a number of countries are offering, the market for solar cells is expanding rapidly. The worldwide solar market grew 50% in 2005 to reach $12 billion, with an expected growth rate of about 30% annually. Each time the production capacity to meet this demand doubles, the cost drops about 20% due to manufacturing efficiencies. Most of this demand is being met by overseas manufacturers. Even so, the U.S. solar energy industry employs about 20,000 workers and is growing at the rate of about 35% annually.
In early 2006, the average cost of an installed watt of solar power was between $6.50 and $7.50. This means that a 2 kilowatt system that provides about 1/3 of an average household's electricity needs (3.7 MWh/year vs. 10.7 MWh/year) and lasting about 20 years costs about $14,000.
As another approach to keeping costs down, solar cell manufacturers are now looking at alternative materials. Two local firms are helping to lead the way. Solar Power Industries, located in Belle Vernon, Pennsylvania, near Pittsburgh has developed a new solar cell that can use a grade of silicon that is still very pure but not pure enough for computer chip manufacturers to use. In fact, they can make use of some of the waste products or leftovers from the chip manufacturing process, which goes far toward keeping production costs down. Plextronics, located in Harmarville, is developing polymer-based solar cells that will be not only be much more economical but will be flexible, which allows for a whole host of new applications.
Because of the cost and the relatively small amounts of electricity generated from solar cells, some jokingly say that solar energy is the fuel of the future and always will be. (To meet the energy needs of the U.S., about 12,000 square miles of solar cells (1/4 of the land area of Pennsylvania) would be required using current technologies.) But in the very long term, as technology improves, solar energy could well be a primary source of energy for the United States. Right now, only about one-tenth of one percent of U.S. electricity is produced by solar energy. But many states are now requiring that some of the electricity that is sold within their boundaries be derived from solar energy. This "legislated market" will go far to help boost investments in solar generation. Pennsylvania has included as part of its recently adopted Alternative Energy Portfolio Standard a requirement that 0.5% of the electricity sold in the state be derived from solar power by the year 2020.
Primarily as a result of the new laws, large solar generation systems which are tied into the electricity transmission grid are showing the most growth. Net metering programs, which allow electricity customers to get credit for any extra power they send back into the grid, are also helping to drive grid-tied installations.
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©2007 Janet S. Lauer Consulting. All rights reserved.