Can you use a laser to transmit electricity? Have we done this practically,
or is it only a theory? If so, what is the efficiency? Does anyone know
the efficiency of a typical high tension line?
You would have to first define what is meant by transmit and then how that
applies to electricity.
Considering that ordinary matter is a combination of charged particles,
electricity can be transmitted by sending matter from one place to another.
-- Fermez le Bush--about two years to go.
I want to transmit energy in the form of light ... laser light specifically.
And light is matter.
Based on this, consider my original post question;
Can you use a laser to transmit electricity? Have we done this
practically, or is it only a theory? If so, what is the efficiency?
I believe this has been done, I just wasn.t sure. Or how efficient it was.
Not really - note that I have seen electrical discharges produced in air by
high concentrations of energy from a laser. but that isn't of much use.
The energy efficiency of a laser is actually quite abyssmal. The advantage
of a laser from an energy point of view is that one can get high energy
density. For transmission, the old fashioned power line is cheaper and more
That is what I learned about fifteen years ago and wondered if we had any
advancement since my last contact with it..
Could losses be overcome in a controlled atmosphere such as argon?
Is the efficiency converting back from light to electricity still as bad as
Copper power lines are dismal, and that science is ancient. With all our
technology, have we not bettered that yet?
As far as I am aware, it is not the medium through which the laser is
transmitted that would determine the efficiency (obviously it does
play a role, but not the largest one). The ineffieciency is inherent
in the genereation of the laser beam itself. Although several methods
do exist, the cheapest one being the diode pump (I think), none of
them are very good efficiency wise.
In the generation process, large amounts of energy must be put into
the system to excite atoms into a meta-stable state in order for
population inversion to take place and hence produce laser light.
Photons have to be kept inside the system long enough to keep this
light continuous, thus one side of the generator is usually totally
reflective, the other side partially reflective. This keeps many of
the photons inside. So think about it - put lots of energy in, get few
photons out. I could be wrong about this but I am unaware of a laser
with more than 50% efficiency.
The next problem is that of divergence. Any laser beam will diverge as
it propogates. Focussing the beam is a very difficult and costly
procedure (except for crude focussing). This would probably make power
transmission over any sort of reasonable distance uneconomical. I am
very rusty on the topic, so I hope I am not talking rubbish.
Hope this was helpful.
Yes, we use aluminum cable with steel cores.:)
Why do you say copper lines are dismal? Have we anything that comes remotely
near them for energy transmission. Unfortunately not. If one could transmit
power 100 miles with an efficiency of the order of 90-95% as is the
situation, then why would one use lasers at possibly 2% efficiency
(optimistic) conversion and over such a distance, collect about 1-2% of that
and convert it back to electricity with a device with 20% efficiency?
Perfectly co-linear lasers do not exist so there is beam spreading. There
is also energy loss due to scattering in the medium. I doubt whether a
controlled atmosphere with any gas would do. A vacuum would be better but in
either case- how straight a tube can you make over a long distance? A small
kink would result in disaster as the beam would destroy the pipe. In
addition, you are then looking at the capital costs involved which would
make overhead power lines look cheap.
Changes that have taken place with power lines are the use of bundled
conductors and also the development of higher voltage systems as well as
reactive controls for such systems. The basic "wires hung from insulators"
still is very good compared to anything else.
Admittedly my own experience with high power lasers is limited to
association with a person who built and tested such lasers. A 20KW CO2 laser
needed a large power supply that in itself took up about twice the volume
of an ordinary living room and needed connections to a cooling system that
was intended for building cooling. The advantage was that it could
concentrate a lot of energy in a small area- so could burn through firebrick
quite easily, weld aluminum to stainless steel and cut or weld pipe such as
used oil pipelines (it's intended purpose). --
Don Kelly email@example.com
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