Solar Energy: The Ultimate Renewable Resource

What is Solar Energy? Originates from nuclear fusion reactions in the sun Originates from nuclear fusion reactions in the sun Nuclear Fusion Video (1.5")

Advantages and Disadvantages Advantages Advantages Chemical/radioactive pollutants remain on sun Chemical/radioactive pollutants remain on sun 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! 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 Disadvantages Sun does not shine consistently. 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. 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.

Putting Solar Energy to Use: Heating Water 2 methods of heating water: passive (no moving parts) and active (pumps) 2 methods of heating water: passive (no moving parts) and active (pumps) In both, a flat-plate collector is used to absorb sun’s energy to heat water In both, a flat-plate collector is used to absorb sun’s energy to heat water Water circulates through the closed system due to convection currents Water circulates through the closed system due to convection currents Tanks of hot water are used as storage or to heat swimming pools Tanks of hot water are used as storage or to heat swimming pools

Heating Water: Active System Active System uses antifreeze so the liquid does not freeze if outside temp. drops below freezing. Active Water Heating Animation

Passive Heating of Living Spaces Best design of a building is for it to act as a solar collector and storage unit. This is achieved through three elements: insulation, collection, and storage. Best design of a building is for it to act as a solar collector and storage unit. This is achieved through three elements: insulation, collection, and storage. Efficient heating starts with proper insulation on external walls, roof, and the floors. Doors, windows, and vents must be designed to minimize heat loss. Efficient heating starts with proper insulation on external walls, roof, and the floors. Doors, windows, and vents must be designed to minimize heat loss. Collection: south-facing windows Collection: south-facing windows

Heating Living Spaces Passive Solar Passively heated home in Colorado

Heating Living Spaces Passively heated homes use 60-75% of solar energy that hits its walls and windows Passively heated homes use 60-75% of solar energy that hits its walls and windows A well-designed passive solar home can reduce energy bills by 75% with an added construction cost of only 5-10% A well-designed passive solar home can reduce energy bills by 75% with an added construction cost of only 5-10% About 25% of energy is used for water and space heating About 25% of energy is used for water and space heating Passive Solar Home Design Video (5")

Solar-Thermal Electricity: Parabolic Dishes and Troughs Solar energy  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. 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. 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. Rows of solar mirrors are arranged in "solar thermal power plants“. They make electricity for more than 350,000 homes. Rows of solar mirrors are arranged in "solar thermal power plants“. They make electricity for more than 350,000 homes.

Solar-Thermal Electricity: Power Towers 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 Power Towers Animation (2.5") Solar Power Towers Animation (2.5")

Direct Conversion into Electricity 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 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