Posted by Mikko on October 31, 2001 at 14:28:35:
In Reply to: That's not true... posted by Emily on October 31, 2001 at 12:23:46:
When it's bright and the sun is high in the sky, all solar panels have about the same efficiency. The best can give 1/6 of that output when it's overcast and raining.
To get more technical, the overall top efficiency of a typical solar panel is 20% (and that of projected ones is ~30%) It means that when 1000 watts of energy from the sun hits a square metre, you'll get about 200 watts of output, assuming it's a 1 square metre (10.8 sq ft) panel. When it gets rainy, it's 1/6 of that or about 33 watts.
Those are average summer day figures. In Finland in February when there are no clouds, solar energy/square metre is about 150 watts or so and the output one tenth compared to above.
The biggest problems with solar energy is that the amount of sunlight varies considerably and it's very difficult to manufacture efficient batteries that could store the energy for long periods of time. This problem is shared by all forms of energy production that use non-continious power sources.
Mikko