1. INTRODUCTION As one of the fastest growing renewable energy sources, solar power is becoming increasingly popular. Over the past fifteen years, solar energy demand has grown at a rate of approximately 30% annually, and in 2008 alone photovoltaic panel installations increased by 5,948 megawatts, enough to power 8,400 households. PV panels alone account for approximately 0.05% of the world’s energy. The leading countries in solar power use are Germany and Spain. COSTS Solar panels cost an average of $95 per square foot and each of these have an average output of 10.6 watts. METHODS FOR GATHERING SOLAR ENERGY Solar Thermal There are two ways to capture solar energy. The first way is known as concentrating solar or solar thermal. The more efficient means of capturing the sun’s energy, solar thermal involves the production of steam, using either parabolic troughs, or fields of flat, computer guided mirrors called heliostats. In order to convert the sun’s energy into electricity, the sun is first directed via heliostats to central spots, such as tubes containing oil or a tower filled with molten salt, the heated medium then powers a conventional generator that produces electricity. Photovoltaic In comparison to the solar thermal method, the Photovoltaic method for gathering solar energy has a lower efficiency, ranging from 10 to 20 percent, compared to the 24 percent efficiency of solar thermal powering. Photovoltaic, or PV panels, directly convert the sun’s rays. In order to provide enough energy for large devices, such as lamps and appliances, several solar cells are connected in one module. Several modules are then place side by side in one panel, and then the panels are connected directly to the device. POSSIBILITES Barak Obama promises to “harness the sun and the winds and the soil to fuel our cars and run our factories” and his 2010 budget called for doubling the country’s renewable energy capacity in three years. The National Renewable Energy Laboratory is the government’s primary research center. According to NREL associate director Robert Hawsey, “solar is such a small fraction of U.S. electricity production that it’s measured in tenths of a percent. But that’s expected to grow. Ten to twenty percent of the nation’s peak electricity demand could be provided by solar energy by 2030.”Aiming to bring the prices down, NREL engineers are studying mirrors made from lightweight polymers instead of glass and receiving tubes that will absorb more sunlight and lose less heat. The biggest problem is how to save the heat produced during the day for use during the night: (solar thermal energy) back in 2008, the first commercial solar plant with heat storage opened near Guadix, Spain. During the day, sunlight from a mirror field is used to heat molten salt, in the evening, as the salt cools it gives back heat to make more steam. Another possibility for storing solar power for the night: (PV) panels produce electricity directly; no heat to capture in tanks of molten salt, one option is to divert some of photovoltaic current during the day to drive pumps, compressing air in underground caverns. When electricity was needed at night, the pent-up electricity from the sunlit hours would be released, rushing forth and spinning a turbine. Another possibility: solar powered electrolyzers that split water molecules into hydrogen and oxygen, recombining the gases in a fuel cell would yield electricity again. Kristina Norris, Lindsay Hetherington, and Mecca Davis Department of Nancy Sources cited “Solar Energy”- New York Times “Plugging into the Sun”- National Geographic Magazine http://www.solarenergy.org/ http://www.nrel.gov/learning/re_solar.html http://www.ucsusa.org/clean_energy PROS ~Quiet ~Sun is free!!!! ~They can help to avoid fossil fuel dependency ~All other energy sources are limited in their quantity ~Can be installed on many rooftops, which eliminates the problem of finding the required space for solar panel placement CONS ~Requires acres of land (for solar thermal mirrors) and long transmission lines (to bring power it produces to market) ~Both methods of solar energy are extremely expensive ~Weather can affect the efficiency ~Pollution can affect the efficiency ~You cannot use them at night…there is no sun at night.