1. Solar energy How Free Is Solar Energy?

2. Introduction
Renewable energy technologies promise to set us free from fossil fuels .
Solar panels that convert sun light to electricity is called photovoltaic.
Panels that convert solar to heat is called thermal solar.

3. Advantages
by using solar power for water heating, we can have an almost zero cost swimming pool or hot water supply.
The usage of electricity generators can be reduced in order to prevent air pollution.
It depends on the sun which is available every where at all time
Disadvantages
One problem with solar cells is that they only produce electricity during the day
The cost of solar panels is relatively expensive compared to other energy sources.
it depends on the weather significantly.

4. How Free is Solar Energy?
Solar energy becomes free depending on payback periods which is effected by how solar cells perform once installed (as shown below)
payback periods
1-4 years
7 kWh/m2/d in Phoenix
2 kWh/m2/d in Moscow
For the most common type of module, which uses multi-crystalline silicon, the energy payback times can be between one and four years.
Source:

5. How Free is Solar Energy?
Thin-film solar cells, which eventually will be much cheaper than multi-crystalline-silicon cells, have shorter energy payback periods. They recover their energy inputs in 10 to 22 months.
Thin-film cells
shorter
payback periods
Cheaper than multi-crystalline-silicon
Source:

6. conclusion
The attractiveness of renewable technologies depends not only on their energy paybacks.
Using other modules like Thin-film solar cells could cost less and have a shorter payback period.

7. References
Wikipedia the solar energy Retrieved from=
By Sandra Upson (2008 ), How Free is Solar Energy Retrieved from=