PV Gap

Cynthia Said:

Catchy title for science fair project about solar energy/solar cell?

We Answered:

The "Bright" Solution (towards saving energy)

Pamela Said:

what is the difference between generating energy using solar cells and solar thermal energy?

We Answered:

Solar photo-voltaic is the absorption of a photon by a semiconductor which causes an electron to be emitted. The frequency of the photon that can be absorped is determined by the orbit of the outer electrons in the semiconductor hence most solar cells only absorb light energy in the infrared spectrum. Various newer solar cells are formulated with different materials to absorb more than one frequency or with an intermediate material that absorbs different frequencies and re-emits them in the desired frequency. Hence generating energy from solar cells is generating a very useful form of energy from a small portion of the sunlight energy falling on the cell. The energy generated by solar cells is in a form valuable enough to sell to the grid.

Solar thermal energy is from the tendency for materials in general to absorb energy from a wide spectrum of light and re-emit them as heat (very low frequency infrared) and using that energy as heat directly rather than trying to convert it to something else. Hence solar thermal energy generation is the generation of a not too useful form of energy from a large portion of the sunlight falling on the solar collector. Solar thermal is great if it's only heat that you want.