Environmental Science Environmental Science Solar Energy Lecture Notes

Solar Energy is RENEWABLE Renewable vs. Nonrenewable Energy Resources DEMO:

Solar Energy can be used 3 ways:  Solar Heating  Solar Heating  Electricity  Solar Radiation  Electricity

Solar Hot Water  1890: solar water heaters used in sunny states like California, Arizona, and Florida  Artificial gas made from coal was available, but cost 10X the price we pay for natural gas today  1920: 1,000’s of solar water heaters had been sold. BUT … large deposits of oil/natural gas were discovered in U. S.  Solar water systems were replaced with heaters burning these cheaper fossil fuels.

Solar collector for heating water A home in California in 1906

Today, solar water heaters are making a comeback (more than ½ million in California alone!).Today, solar water heaters are making a comeback (more than ½ million in California alone!). Heat water for homes/businesses and swimming pools (see picture)Heat water for homes/businesses and swimming pools (see picture) Panels on roof contain water pipes. Sun hits the panels and pipes.Panels on roof contain water pipes. Sun hits the panels and pipes. Warmed water is then used in a poolWarmed water is then used in a pool

Solar Thermal Electricity  Solar energy  electricity  Some solar power plants (see picture from Mojave Desert) use curved mirror called PARABOLIC TROUGH to focus sunlight on a pipe running down center of mirror.  Mirror focuses sunlight onto the pipe, causing the water to boil and produce steam. Steam can then be used to turn a turbine to make electricity.  These rows of solar mirrors arranged in "solar thermal power plants“. They make electricity for more than 350,000 homes.

Solar Thermal Electricity  PROBLEM: Works only when sun is shining. On cloudy days/at night, the power plants can't make electricity.  Some solar plants, use "hybrid" technology  During day they use sun. At night/cloudy days they burn natural gas to boil water to generate electricity.

SOLAR THERMAL ELECTRICITY

  Another form of solar power (heat) to make electricity: (Central Tower Power Plant)    Sunlight is reflected off 1,800 mirrors (HELIOSTATS) circling the tall tower.   Fluid (liquid sodium) is heated by sun's rays. The fluid is used to boil water  make steam  turn a turbine and generator   This experimental power plant is called Solar II. It was built in California's desert.   Scientists say larger central tower power plants can make electricity for 100,000 to 200,000 homes.

Solar Cells or Photovoltaic Energy   Sunlight converted directly to electricity using solar cells   Solar cells also called photovoltaic cells (PV cells) and can be found on many small appliances, like calculators, and even on spacecraft   First developed in 1950’s for U.S. space satellites.   Made of silicon, special type of melted sand   Sunlight strikes solar cells and electrons (red circles) are knocked loose. They move toward treated front surface (dark blue color). When the two surfaces are joined by a wire, a current of electricity occurs between negative and positive sides.   Solar cells  PV module  Array.   Some arrays are set on special tracking devices to follow sunlight all day long. Photovoltaic Energy Video

  Electrical energy from solar cells can be used for lights/appliances   Solar energy can be stored in batteries to light roadside billboards at night   Energy can be stored in a battery for emergency roadside telephones where no phone wires are around   Some experimental cars also use PV cells. They convert sunlight directly into energy to power electric motors on the car.   Solar cells are used in satellites in outer space. Here's a picture of solar panels extending out from a satellite. Rooftop PV Modules