What is Solar Energy? • Originates with the thermonuclear fusion reactions occurring in the sun. • Represents the entire electromagnetic radiation (visible light, infrared, ultraviolet, x-rays, and radio waves).
Advantages and Disadvantages • Advantages • All chemical and radioactive polluting byproducts of the thermonuclear reactions remain behind on the sun, while only pure radiant energy reaches the Earth. • Energy reaching the earth is incredible. By one calculation, 30 days of sunshine striking the Earth have the energy equivalent of the total of all the planet’s fossil fuels, both used and unused! • Disadvantages • Sun does not shine consistently. • Solar energy is a diffuse source. To harness it, we must concentrate it into an amount and form that we can use, such as heat and electricity. • Addressed by approaching the problem through: 1) collection, 2) conversion, 3) storage.
Photovoltaic Cells: converting photons into electrons • Photons in sunlight hit the solar panel and are absorbed by semiconducting materials, such as silicon. • Electrons (negatively charged) are knocked loose from their atoms causing them to flow through the material , in one direction, to produce electricity (the flow of electrons is current). • The flow of e- is current and we can draw that current off for external use. • This current, together with the cell's voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce. http://www.sunnywinenergy.com/en/AboutSun_02_en.htm
Global Cumulative PV Power http://www.epia.org/fileadmin/EPIA_docs/publications/epia/Global_Market_Outlook_Until_2013.pdf
Cumulative Installed Solar Electric Power by 2007 • 1st Germany 3.8 GW • 2nd Japan 1.9 GW • 3rd US 814 MW • 4th Spain 632 MW
Renewable Energy Consumption in the US Energy Supply, 2007 http://www.eia.doe.gov/cneaf/solar.renewables/page/trends/highlight1.html
Chart Data http://www.eia.doe.gov/cneaf/solar.renewables/page/trends/figure1_1.xls
Friday April 8th Photovoltaic Cells Lab
Group Analysis • About half the incoming solar energy reaches the Earth's surface. • The Earth receives 174 petawatts (PW) (1015 watts) of incoming solar radiation at the upper atmosphere. Approximately 30% is reflected back to space while the rest is absorbed by clouds, oceans and land masses. • Earth's land surface, oceans and atmosphere absorb solar radiation, and this raises their temperature. Sunlight absorbed by the oceans and land masses keeps the surface at an average temperature of 14 °C. • By photosynthesis green plants convert solar energy into chemical energy, which produces food, wood and the biomass from which fossil fuels are derived. http://en.wikipedia.org/wiki/Solar_energy