Solar Energy

The Earth receives an incredible supply of solar energy. The sun, an average star, is a fusion reactor that has been burning over 4 billion years. It provides enough energy in one minute to supply the world's energy needs for one year. In one day, it provides more energy than our current population would consume in 27 years. In fact, "The amount of solar radiation striking the earth over a three-day period is equivalent to the energy stored in all fossil energy sources."

Solar energy is a free, inexhaustible resource, yet harnessing it is a relatively new idea. The ability to use solar power for heat was the first discovery. A Swiss scientist, Horace de Saussure, built the first thermal solar collector in 1767, which was later used to heat water and cook food. The first commercial patent for a solar water heater went to Clarence Kemp of the US in 1891. This system was bought by two California executives and installed in one-third of the homes in Pasadena by 1897.

Producing electricity from solar energy was the second discovery. In 1839 a French physicist named Edmund Becquerel realized that the sun's energy could produce a "photovoltaic effect" (photo = light, voltaic = electrical potential). In the 1880s, selenium photovoltaic (PV) cells were developed that could convert light into electricity with 1-2% efficiency ("the efficiency of a solar cell is the percentage of available sunlight converted by the photovoltaic cell into electricity"), but how the conversion happened was not understood. Photovoltaic power therefore "remained a curiosity for many years, since it was very inefficient at turning sunlight into electricity." It was not until Albert Einstein proposed an explanation for the "photoelectric effect" in the early 1900s, for which he won a Nobel Prize, that people began to understand the related photovoltaic effect.



"Solar technology advanced to roughly its present design in 1908 when William J. Bailey of the Carnegie Steel Company invented a collector with an insulated box and copper coils." By the mid-1950s Bell Telephone Labs had achieved 4% efficiency, and later 11% efficiency, with silicon PV cells. From then on, interest in solar power intensified. During the late 1950s and 1960s, the space program took an active role in the development of photovoltaics. "The cells were perfect sources of electric power for satellites because they were rugged, lightweight and could meet the low power requirements reliably." Unfortunately, the cells were not practical for use on earth due to the high cost of making them efficient and lightweight, so further research was necessary.

Solar energy may have had great potential , but it was left on the backburner whenever fossil fuels were more affordable and available. "Only in the last few decades when growing energy demands, increasing environmental problems and declining fossil fuel resources made us look to alternative energy options have we focused our attention on truly exploiting this tremendous resource." For instance, the US Department of Energy funded the installation and testing of over 3,000 PV systems during the 1973-1974 oil embargo. By the late 1970s, energy companies and government agencies had invested in the PV industry, and "a tremendous acceleration in module development took place." Solar energy improvements were again sought during the Gulf War in the 1990s.

Considering that "the first practical solar cells were made less than 30 years ago," we have come a long way.The profligation of solar professional companies designing unique and specific solar power systems for individual homes, means there is no longer an excuse not to consider solar power for your home. The biggest jumps in efficiency came "with the advent of the transistor and accompanying semiconductor technology." The production cost has fallen to nearly 1/300 of what it was during the space program of the mid-century and the purchase cost has gone from $200 per watt in the 1950s to a possible mere $1 per watt today. The efficiency has increased dramatically to 40.8% the US Department of Energy's National Renewable Energy Lab's new world record as of August 2008.

We still use solar power in the same two forms today, thermal and photovoltaic. The first concentrates sunlight, converts it into heat, and applies it to a steam generator or engine to be converted into electricity in order "to warm buildings, heat water, generate electricity, dry crops or destroy dangerous waste." Electricity is generated when the heated fluid drives turbines or other machinery. The second form of solar power produces electricity directly without moving parts. Today's photovoltaic system is composed of cells made of silicon, the second most abundant element in the earth's crust. "Power is produced when sunlight strikes the semiconductor material and creates an electric current." The smallest unit of the system is a cell. Cells wired together form a module, and modules wired together form a panel. A group of panels is called an array, and several arrays form an array field.

There are several advantages of photovoltaic solar power that make it "one of the most promising renewable energy sources in the world." It is non-polluting, has no moving parts that could break down, requires little maintenance and no supervision, and has a life of 20-30 years with low running costs. It is especially unique because no large-scale installation is required. Remote areas can easily produce their own supply of electricity by constructing as small or as large of a system as needed. Solar power generators are simply distributed to homes, schools, or businesses, where their assembly requires no extra development or land area and their function is safe and quiet. As communities grow, more solar energy capacity can be added, "thereby allowing power generation to keep in step with growing needs without having to overbuild generation capacity as is often the case with conventional large scale power systems." Compare those characteristics to those of coal, oil, gas, or nuclear power, and the choice is easy. Solar energy technologies offer a clean, renewable and domestic energy source.

Photovoltaic power even has advantages over wind power, hydropower, and solar thermal power. The latter three require turbines with moving parts that are noisy and require maintenance.

Solar energy is most sought today in developing countries, the fastest growing segment of the photovoltaics market. People go without electricity as the sun beats down on the land, making solar power the obvious energy choice. "Governments are finding its modular, decentralized character ideal for filling the electric needs of the thousands of remote villages in their countries." It is much more practical than the extension of expensive power lines into remote areas, where people do not have the money to pay for conventional electricity.

India is becoming one of the world's main producers of PV modules, with plans to power 100,000 villages and install solar-powered telephones in its 500,000 villages. By 2000, Mexico plans to have electrified 60,000 villages with solar power. Zaire 's Hospital Bulape serves 50,000 outpatients per year and is run completely on solar power, from air conditioning to x-ray equipment. And in Moroccan bazaars, carpets, tin ware, and solar panels lie side by side for sale. Probably the most outstanding example of a country's commitment to solar power is in Israel . In 1992, over half of all households (700,000) heated their water with solar energy systems. And there are 50,000 new installations every year.

Solar power is just as practical in populated areas connected to the local electrical power grid as it is in remote areas. "An average home has more than enough roof area to produce enough solar electricity to supply all of its power needs. With an inverter, which converts direct current (DC) power from the solar cells to alternating current (AC), which is what most home appliances run on, a solar home can look and operate very much like a home that is connected to a power line."

Household energy supply is but one use of solar power. There are actually four broad categories that can be identified for solar energy use: industrial, rural habitation, grid-connected, and consumer/indoor. Industrial uses represent the largest applications of solar power in the past 30 years. "Telecommunications, oil companies, and highway safety equipment all rely on solar power for dependable, constant power far from any power lines." Roadside call boxes and lighted highway signs rely on the sun's energy in order to provide reliable services without buried cable connections or diesel generators. Navigational systems such as marine buoys and other unmanned installations in harsh remote areas are also ideal applications for solar power because "the load demands are well known and the requirements for reliable power are the highest." Rural habitation includes "cabins, homes, villages, clinics, schools, farms, as well as individually powered lights and small appliances." Grid-connected systems pair solar power with an existing grid network in order to supply a commercial site with enough energy to meet a high demand, or to supplement a family's household supply. Consumer/indoor uses of PV cells include watches and calculators; PV modules power computers and radios.

The practicality and environmentally safe nature of solar power is influencing people worldwide, which is evident in equipment sales. According to Seimens Solar, production of PV cells and modules increased threefold from 40 MW in 1990 to about 120 MW in 1998. "Worldwide sales have been increasing at an average rate of about 15% every year during the last decade . We believe that there is a realistic possibility for the market to continue to grow at about a 15% rate into the next decade. At this rate, the world production capacity would be 1000 MW by 2010, and photovoltaics could be a $5 billion industry."

There are only two primary disadvantages to using solar power: amount of sunlight and cost of equipment. The amount of sunlight a location receives "varies greatly depending on geographical location, time of day, season and clouds. The southwestern United States is one of the world's best areas for sunlight . Globally, other areas receiving very high solar intensities include developing nations in Asia, Africa and Latin America ." See also sustainable house design

But a person living in Siberia would not benefit much from this renewable resource. And while "solar energy technologies have made huge technological and cost improvements, [they]are still more expensive than traditional energy sources." However solar equipment will eventually pay for itself in 2 to 5 years depending on h ow much sun a particular location receives. Then the user will have a virtually free energy source until the end of the equipment's working life, according to a paper called "Energy Payback Time of Crystalline Silicon Solar Modules." Future improvements are projected to decrease the payback time to 1 to 3 years.

The best way of lowering the cost of solar energy is to improve the cell's efficiency, according to Larry Kazmerski, Director of the DOE's National Center for Photovoltaics. "As the scientists and researchers at the NCPV push the envelope of solar-cell efficiency, we can begin to visualize the day when energy from the sun will be generating a significant portion of the country's electric power demand." Any improvements and subsequent cost cuts will also be vital to space applications.Also try finding the right Electric company in order to save money. Power companies can help you benefit with decisions such as this.

As the price of solar power lowers and that of conventional fuels rises, photovoltaics "is entering a new era of international growth." So much so, that solar power "will remain an excellent energy option, long after the momentary fossil fuel model fades into smoke."