Everyday the sun radiates energy down to the earth's surface. These rays of sunlight can be turned into several forms of renewable energies (excluding tidal and geothermal). Renewables are a naturally occurring source of energy that does not come from a fossil or nuclear based fuel. The suns rays are turned into renewable energy in both indirect and direct manners. Indirectly, solar radiation influences the Earth's water, air current, and photosynthesis cycles These cycles are used to generate hydro, wind and wave, and bioenergy respectively. Directly, solar radiation can turned to electricity, as well as absorbed for heating.
For further information visit DOE's Solar Energy Resource Basics page.
Types of Direct Solar Energy Systems
Videos describing some of the technologies found below can be found on ISEA's Educational Videos page.
Photovoltaic systems operate using a principle known as the Photovoltaic effect. This effects allows solar pv panel to directly convert solar radiation into electricity.
1) The solar pv panels collect the sun light and turn it into electricity.
2) The electricity reaches the inverter where it is changed into a compatible format.
3) The electricity is used within the building. Any unused electricity is sent to step 4.
4) The meter keeps track of electricity used in the building and produced from the panels.
- Any unused electricity is sent to the electricity grid.
For further information visit DOE's Photovoltaic Technology Basics page.
Concentrated Photovoltaic systems operate in a similar manner to normal PV systems, but involve the use of mirrors or lenses to concentrate the suns rays. This system generates more energy out of a solar cell and are typically used on a non-residential scale.
1) The primary mirror reflects sunlight to toward the secondary mirror.
2) The secondary mirror reflects sunlight toward the optical rod.
3) The optical rod concentrates the sunlight.
4) The solar cell receives the concentrated sunlight and turns it into electricity.
For further explanation visit NREL's Concentrating Photovoltaic Technology page.
Active Solar Thermal
Building scale Active Solar Thermal systems typically involve the use of a solar collector. These collectors contain tubes which hold a liquid that is heated by the sun and is used for domestic hot water. Solar thermal is also used on a utility scale (larger than building) to generate electricity. An example of a utility scale system is provided below.
Building Scale Solar Thermal
1) Sunlight hits the panel where liquid filled tubes absorb heat.
2) The heated liquid moves to a tank where the heat is transferred to the water inside the tank.
3) The cool liquid is moved back into the tubes of the solar collector.
For further details on Residential Scale Solar Thermal visit HowStuffWorks.com's Solar Water Heaters page.
Utility Scale Solar Thermal
1) Mirrors placed on the ground, called Heliostats, focus light onto the receiver.
2) The receiver transfers the heat from light directed towards it to a liquid within the receiver.
3) The liquid is heated by the reflected light and sent to a steam turbine to generate electricity.
4) The liquid is sent back to the receiver.
For further details on Utility Scale Solar Thermal visit DOE's Concentrating Solar Power Basics page.
Passive Solar systems typically consist building design which utilize the suns radiation to heat and light the building. These systems sometimes use pumps and fans to circulated the heated air.
1) Sunlight travels through glass and heats the air trapped behind the glass.
2) The heated air rises and travels through the opening in the top if the wall.
3) Cold air sinks and travels back to be heated.
For further information on building Passive Solar visit DOE's Passive Solar Home Design page.
Boyle, Godfrey. Renewable Energy: Power For A Sustainable Future. Oxford: Oxford UP in Association with the Open University, 2004. Print.