HELLO!
i went for an energy efficiency course and i learnt something that was related to our SIA topic ;D

There are few ways to harness the sun's energy.
a) By photosynthesis
b) By direct heating which can be active or passive
c) By the use of photovoltaic cells

1.1) Photosynthesis
Plants obtain their energy from sunlight through photosynthesis. Photosynthesis is the process whereby solar energy is stored in the chemical bonds of a carbohydrate molecule. In fact, the energy from fossil fuels such as oil and natural gas are also produced in this way millions of years ago.

1.2) Active & Passive Heating
The easiest way to use the sun's energy is by direct solar heating. Active solar heating uses pumps or fans to circulate the heated fluid. Solar heaters, used for heating water in the house are popular because they are simple, don't pollute and is free to operate. The only drawback is that these heaters are expensive. Using the sun to keep the house cool and warm is called passive solar heating. This usually means designing houses and using materials that keep the house at a comfortable temperature thus reducing the need for air conditioning. Such houses can keep the house cool during the day but store the heat in the night.

Advantages & Disadvantages
It is free, clean and renewable. However, much capital investment is required as the solar panel is very expensive.

1.3) Photovoltaic or Solar Cells
It was discovered in 1939 (A.C. Becquerel) that light can induce a voltage in some materials. This discovery was first put to practical use in the United State's space program when solar cells powered the Skylab and other satellites. Solar cells produce electricity when a photon or light energizers a charge carrier such as an electron (to absorb the sunlight).

Advantages & Disadvantages
Solar energy is clean, free and renewable. However, a few problems exist;

a) Solar intensity is not always constant.
b) The sun doesn't shine at night at the equator.
c) Storing electricity for night use is still expensive and inefficient.
d) Solar cells are still relatively expensive and many are required for major applications.
e) Large open space is required to install solar cells.

- Chinwen (: