Yes this a serious post. At some point in basic electronics you are
asked to compute the power used by a resistor. For some reason
engineers don't care if the devices they design use energy efficently.
Pick up some batteries off the street that some one has thrown away
they average 1.2 volts. At 1.2 volts an alkaline battery still has
about 40 percent of its energy left. Design a radio to use 4.5 volts
but takes 4 batteries. Have a circuit that uses 3 batteries at a time
while rotating the unused battery at a regular interval. Then when the
voltage of the batteries drops to 1.2 volts each the circuit switches
to using all 4 batteries in series. All the batteries can be run down
to .9 volts each where they have about 10 percent of their energy left.
This idiot circuit could have been made 100 years ago. A modern radio
would test each battery, you could then mix types of batteries in a
radio. A resistor that throws away heat is only one part of an energy
wasting device. Perhaps what I am thinking of is instead of a resistor
you need a current limiting device.
Sadly, a current limiting device wastes the same amount of energy as a
resistor (perhaps more, since it will require some control, which could
take power as well.) The problem is that many times, engineers use the
fact that resistors 'waste' power in their circuits. Dropping a given
amount of current from voltage a to voltage b means that a certain
amount of power must be taken out somehow. Your light idea was a way to
regain some of that power (a very small amount).
However, if you are worried about battery pollution, you should rest
easy knowing that there are circuits that can draw batteries down to
quite low levels. They are proliferating in the form of white light LED
driver circuits. They generally use the magnetic field in inductors to
drive the thing. This is similar to two paddle wheels which are coupled
by a mechanical connection of some kind. If the driving paddle wheel
takes energy from a stream that is dropping 5 meters, it can raise 1/3
of the amount of water up to 15 meters (minus some loss for friction,
energy collection efficiency, etc).
However, considering energy efficiency of resistors when people drive
SUVs to the supermarket and leave their computers on all night is like
rearranging the deck chairs on the titanic as it sinks.
--
Regards,
Robert Monsen
"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.