by ChumpusRex2 » Mon 18 Sep 2006, 19:30:43
$this->bbcode_second_pass_quote('SolarDave', '
')I use a Maxwell 15 volt 58 Farad unit to "smooth" out the power from the pedal generator. It's as close to perfect as it can be for this use. It holds enough energy (and this is the smallest 15 volt unit Maxwell makes) that I can stop pedaling for short periods and the TV/Air compressor/Light runs for a short time after. They are more efficient than batteries (more of the electricity you put in comes back out), and they have virtually unlimited lives.
The catch with capacitors that makes them a difficult proposition for home-built energy, is that they need to be swung from low-to-high voltage to charge, and vice-versa.
Unless you use some form of switched-mode electronic charge controller, the efficiency of charging cannot exceed 50%. This is in stark contrast to batteries, where making a 70-80% efficient charger is relatively straight-forward.
[Most power sources e.g. solar, generators, etc. are constant-voltage.
[V = voltage. Q = charge
Energy required to charge a cap from a constant-voltage source = V x Q.
Energy stored in a cap = 0.5 x V x Q.]