PV Gap

Dwight Said:

Sankey Diagram for a Solar Panel?? HELP!!?

We Answered:

There are two kinds of solar panels..one that heats air or water and the second is one that converts sunlight to electricity.

For a solar panel that converts sun to electricity, this is what happens. Approximately 1000 watts per square meter of energy from the sun strike the solar panel surface.
About 8% of the light is reflected off the surface of the solar panel because it is impossible to get 100% absorption of light.

Then the process of converting the photons of energy of the sun and changing them into electron flow (which is electricity) happens in the silicon semiconductor substrate. This conversion is only about 14% efficient , which means about 85% of the sun's energy is lost in the conversion. So if a 1000 watts reaches the semiconductor , only 150 watts comes back out as electricity.

Then there is a charge controller, which is a device that keeps the electricity from the panel going in one direction toward the 12v battery. This stops electricity from the battery from going back into the solar panel when the sun isn't shining. It also stops the battery from overcharging once it is full. This device wastes about 3% of the power.

Then you have a battery which stores the electric power. It only is about 90% efficient, which means for every 100 watts going in to it, it only gives you 90 watts output. Finally you have the Electric output...which is only about 7% of the total power that came in , once you run it thru the batteries and charge controller.

I drew a crappy Sankey diagram for you:
http://i704.photobucket.com/albums/ww43/…