11-02-2013, 04:18 PM
Renewable energy
Renewable energy.ppt (Size: 3.33 MB / Downloads: 183)
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(放射性) 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.
Solar Heating
Two methods of heating water: passive (no moving parts)(被动式) and active (pumps)(主动式).
In both, a flat-plate collector is used to absorb the sun’s energy to heat the water.
The water circulates throughout the closed system due to convection currents.
Tanks of hot water are used as storage.