 |  | | IntroductionEnergy ExpressOur knowledge about the sun has increased throughout the ages. In ancient times, it was believed that the sun orbited the earth. Then, during the time of Copernicus and Galileo, scientists realized that the sun did not orbit the earth; rather the earth orbited the sun. We now know that the sun is but one star out of the millions of stars in our galaxy, which is but one galaxy among millions of galaxies. Despite this apparent cosmic insignificance, the sun provides virtually all the energy used on Earth. In the most obvoius form, the sun shines on about one-half of the planet constantly, providing us with light and heat. Other forms are not so obvious. All the so-called "fossil fuels" used for energy today were plants which used the sun's energy in photosynthesis, millions of years ago. So, how can the sun provide so much energy? In a matter of speaking, the sun is a continuous explosion of a hydrogen bomb, held back only by gravity. The bombs dropped on Nagasaki and Hiroshima, Japan, pale in comparison to a "modern" hydrogen bomb, which itself pales to the sun. Perhaps fortunately, most of the sun's intense radient energy never reaches Earth. It shines, instead, on other planets, moons, and so on, or it simply goes off into the depths of space. This energy travels at the speed of light, about 300,000 kilometers per second. Sparing the calculations, it takes about eight minutes for this radiant energy to reach Earth in the form of light. Various forms of light are blocked by the ozone layer and such, but two major types of light hit the planet. The first is visible light, which causes day to be much brighter than night. The second is infrared light, which keeps the planet at an average temperature of about sixty degrees Farenheit. In light of these observations, the question now becomes: how can we best use the solar energy that does get to our planet? Photovoltaic Cells: ScienceThe most efficient system to date for capturing solar energy is photovoltaic cells. They use the freely available energy of sunlight to cause a reaction that produces direct current. This reaction involves elements with very loosely held outer electrons. When light energy is applied, these electrons escape, forming a current. This current, however, is generally small, so large arrays of cells need to be used. In a short article written by Harry Roman and Ken Maskell, the concept of photovoltaic cells is summed up as follows:
Semiconductors are the primary counterparts in many types of modern equipment, including computer chips. The most commonly used semiconductor is silicon, which is abundant in the earth's crust, mostly in the form of silicon dioxide, which is SiO2. While the concept of being simple is a highly relative term, photovoltaic cells are nearly silent. One does not hear his or her calculator make any noise, and the calculator is powered by photovoltaics. No moving parts are used, except for the moving electrons, which are far too small for us to see. Perhaps the biggest benefits of photovoltaics over the other typerss of energy production is that it does not pollute the planet. Incomplete combustion of fossil fuels leads to, in addition to carbon dioxide and water, many dangerous chemicals. No chemical ever leaves the cell, and therefore could never be released into the environment. Photovoltaic Sells: EconomicsIt is in the very nature of capitalism that only those things which are economically sound will ever be used at a large scale. The first photovoltaic systems ever produced cost more than $1000/watt for electric production, but the costs have now been slashed to about $7/watt. This is approaching the costs of being on the "grid" systems of conventional electric power. There are several problems that need to be addressed before and if solar power is to become prominent. Efficiency neds to be improved from the barely 20 percent of today. Also, it is often difficult to get enough energy. Places such as Canada, Russia, and much of the northern United States receive comparatively little sunlight during much of the year. Once the technical hurdles have been crossed, the biggest problem may be in convincing power companies and their customers to take the initial "hit" solar power will have in their pocketbooks for cheaper energy later on.
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