Maximum capacity of solar panels

Any one know ....

How many W/m2 can solar panels produce, assuming concentrated or laser
light?

The application I was thinking of was for a Solar Power station at
Earth - Moon L1, beaming laser power to vehicles on the moon's
surface.

I think a mechanical digger or large dump truck might need about 100
KW. Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

For these slow moving vehicles, tracking should not be a problem.

The other application is reducing solar cell area by preconcentrating
light on it, since mirrors are lighter and cheaper than solar cells.

Alex

In article ,
Alex Terrell wrote:
How many W/m2 can solar panels produce, assuming concentrated or laser
light?

Nobody has done much work on optimizing solar panels for laser illumination,
so I think the answer to that one is "nobody knows".

Solar-concentrator systems are still somewhat experimental. (Note that
you have to do the concentration near the array -- it is fundamentally
impossible to concentrate sunlight into a narrow beam for long-range
transmission.) My impression is that currently feasible concentration
factors are relatively small, but I haven't followed this closely. Do
note that the better concentrator arrays generally have to be aimed quite
carefully at the light source -- they don't have the wide-angle reception
of a normal solar array.

...Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

Converting the laser beam into heat is no big deal in priniciple, but then
you run into the inefficiency of heat engines, and the need to get rid of
a lot of waste heat with a radiator system. Solar arrays are easier.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Alex Terrell) wrote in message . com...
Any one know ....

How many W/m2 can solar panels produce, assuming concentrated or laser
light?

The application I was thinking of was for a Solar Power station at
Earth - Moon L1, beaming laser power to vehicles on the moon's
surface.

I think a mechanical digger or large dump truck might need about 100
KW. Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

For these slow moving vehicles, tracking should not be a problem.

The other application is reducing solar cell area by preconcentrating
light on it, since mirrors are lighter and cheaper than solar cells.

Alex

A solar panel converts roughly 7-17% of the light it recieves into
electricity. This depends on heat and the cells themselves. For
example a silicon PV cell loses half its efficiency between 0 C and
room temp. Basically, of the light hitting the solar panel, about
50-60% gets absorbed with about 5-15% getting converted to electricity
and 40-50% getting converted to heat, so concentrating the light means
more wattage hits the panel so more electricity gets generated, but it
also heats up the panel lowering efficiency. I don't know the wattage
of concentrated light, but for a laser, assuming you can put big
enough panels to collect 90% of the light from it, a 100 KW laser
(should be available soon using diode pumped lasers, so no fuel) you
would get 90 KW hitting the panels, so you would generate 6-15 KW of
electric power but about 38.7 KW of heat. That is a lot of heat you
have to disapate. You also need to store some of that electric power
as most 100 KW lasers are pulsed (I don't really know of one that
isn't), so your actual throughput is less. I don't know much about
solar thermal solutions but that may be better (using the laser to
heat a convective fluid to run a turbogenerator).

(Henry Spencer) wrote in message ...
In article ,
Alex Terrell wrote:
How many W/m2 can solar panels produce, assuming concentrated or laser
light?

Nobody has done much work on optimizing solar panels for laser illumination,
so I think the answer to that one is "nobody knows".

Solar-concentrator systems are still somewhat experimental. (Note that
you have to do the concentration near the array -- it is fundamentally
impossible to concentrate sunlight into a narrow beam for long-range
transmission.) My impression is that currently feasible concentration
factors are relatively small, but I haven't followed this closely. Do
note that the better concentrator arrays generally have to be aimed quite
carefully at the light source -- they don't have the wide-angle reception
of a normal solar array.

If concentration factors are quite small than maybe solar cells won't
work. A large digger might need 100 KW. If the solar cells can deliver
400W/m2, then 250m2 is needed, assuming the laser is accuratre and
also spread over this area.

Imagine a large digger or dump truck with a 20m diameter solar array
over it!

...Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

Converting the laser beam into heat is no big deal in priniciple, but then
you run into the inefficiency of heat engines, and the need to get rid of
a lot of waste heat with a radiator system. Solar arrays are easier.

I agree solar arrays are easier, but you have 20% efficiency of the
array and 90% efficiency of the motor = 18%. That's a lot of heat to
dump, though the array could be several meters above the vehicle.

A heat engine should be able to do better than that. The heat that
needs to be dumped would be no more than if the heat source were an
internal combustio engine - though that would be a problem in the
vacuum of the moon.

In article ,
Alex Terrell wrote:
Converting the laser beam into heat is no big deal in priniciple, but then
you run into the inefficiency of heat engines, and the need to get rid of
a lot of waste heat with a radiator system. Solar arrays are easier.

I agree solar arrays are easier, but you have 20% efficiency of the
array and 90% efficiency of the motor = 18%...

Note that for a well-chosen laser wavelength, the conversion efficiency of
simple solar cells is 50%+. The reason the efficiencies are so cruddy
when working from sunlight is the huge spread of photon energies.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(George) wrote in message . com...
(Alex Terrell) wrote in message . com...
Any one know ....

How many W/m2 can solar panels produce, assuming concentrated or laser
light?

The application I was thinking of was for a Solar Power station at
Earth - Moon L1, beaming laser power to vehicles on the moon's
surface.

I think a mechanical digger or large dump truck might need about 100
KW. Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

For these slow moving vehicles, tracking should not be a problem.

The other application is reducing solar cell area by preconcentrating
light on it, since mirrors are lighter and cheaper than solar cells.

Alex

A solar panel converts roughly 7-17% of the light it recieves into
electricity. This depends on heat and the cells themselves. For
example a silicon PV cell loses half its efficiency between 0 C and
room temp. Basically, of the light hitting the solar panel, about
50-60% gets absorbed with about 5-15% getting converted to electricity
and 40-50% getting converted to heat, so concentrating the light means
more wattage hits the panel so more electricity gets generated, but it
also heats up the panel lowering efficiency. I don't know the wattage
of concentrated light, but for a laser, assuming you can put big
enough panels to collect 90% of the light from it, a 100 KW laser
(should be available soon using diode pumped lasers, so no fuel) you
would get 90 KW hitting the panels, so you would generate 6-15 KW of
electric power but about 38.7 KW of heat. That is a lot of heat you
have to disapate. You also need to store some of that electric power
as most 100 KW lasers are pulsed (I don't really know of one that
isn't), so your actual throughput is less. I don't know much about
solar thermal solutions but that may be better (using the laser to
heat a convective fluid to run a turbogenerator).


You guys can more efficiently transmit energy using microwave
antennas. You can get 60% efficiency by radiating microwaves onto an
antenna that is equipped with microwave diodes. This would be the
preferred method of transmitting power.

Zoltan

(Henry Spencer) wrote in message
My impression is that currently feasible concentration
factors are relatively small, but I haven't followed this closely. Do
note that the better concentrator arrays generally have to be aimed quite
carefully at the light source -- they don't have the wide-angle reception
of a normal solar array.

this feild has been steadily improving, a search for non-imaging
optics will point you in the right direction. In space the
concentration factors are limited for thermal reasons, but water
cooled solar cells with high concentrations have been demonstrated.
Wide-angle reception has also been demonstrated, but there are
fundamental limitations to concentration factors and reception angles.

Greg

"Zoltan Szakaly" wrote in message
om...

You guys can more efficiently transmit energy using microwave
antennas. You can get 60% efficiency by radiating microwaves onto an
antenna that is equipped with microwave diodes. This would be the
preferred method of transmitting power.
Japanese have done most of the latest research work in WPT, and IIRC they
have achieved efficiencies in excess of 80%.
( sites to check:
http://global.mitsubishielectric.com...r/sol01_b.html and
http://www.wronkiewicz.net/ssp/)

But, wrt solar cells, check out this
http://www.spacedaily.com/news/solarcell-02m.html
"An Unexpected Discovery Could Yield A Full Spectrum Solar Cell"
"The serendipitous discovery means that a single system of alloys
incorporating indium, gallium, and nitrogen can convert virtually the full
spectrum of sunlight -- from the near infrared to the far ultraviolet -- to
electrical current."
"great many layers with only small differences in their band gaps could be
stacked to approach the maximum theoretical efficiency of better than 70
percent."

-kert

(Zoltan Szakaly) wrote in message . com...
(George) wrote in message . com...
(Alex Terrell) wrote in message . com...
Any one know ....

How many W/m2 can solar panels produce, assuming concentrated or laser
light?

The application I was thinking of was for a Solar Power station at
Earth - Moon L1, beaming laser power to vehicles on the moon's
surface.

I think a mechanical digger or large dump truck might need about 100
KW. Alternatively, could the laser be converted directly into heat to
drive a closed cycle engine?

For these slow moving vehicles, tracking should not be a problem.

The other application is reducing solar cell area by preconcentrating
light on it, since mirrors are lighter and cheaper than solar cells.

Alex

A solar panel converts roughly 7-17% of the light it recieves into
electricity. This depends on heat and the cells themselves. For
example a silicon PV cell loses half its efficiency between 0 C and
room temp. Basically, of the light hitting the solar panel, about
50-60% gets absorbed with about 5-15% getting converted to electricity
and 40-50% getting converted to heat, so concentrating the light means
more wattage hits the panel so more electricity gets generated, but it
also heats up the panel lowering efficiency. I don't know the wattage
of concentrated light, but for a laser, assuming you can put big
enough panels to collect 90% of the light from it, a 100 KW laser
(should be available soon using diode pumped lasers, so no fuel) you
would get 90 KW hitting the panels, so you would generate 6-15 KW of
electric power but about 38.7 KW of heat. That is a lot of heat you
have to disapate. You also need to store some of that electric power
as most 100 KW lasers are pulsed (I don't really know of one that
isn't), so your actual throughput is less. I don't know much about
solar thermal solutions but that may be better (using the laser to
heat a convective fluid to run a turbogenerator).


You guys can more efficiently transmit energy using microwave
antennas. You can get 60% efficiency by radiating microwaves onto an
antenna that is equipped with microwave diodes. This would be the
preferred method of transmitting power.

Zoltan

I agree for tranmission to large fixed rectennas, but the specific
application is to power vehicles on the moon from L1, so a tight beam
is needed.

Actually I thought Rectennas were closer to 90% efficient.

In article ,
Zoltan Szakaly wrote:
You guys can more efficiently transmit energy using microwave
antennas. You can get 60% efficiency by radiating microwaves onto an
antenna that is equipped with microwave diodes.

Better than that, actually. Unfortunately, microwaves lose badly for
long-range transmission except at very high power with very large
receiving antennas. The longer wavelength -- five orders of magnitude
longer than light -- means it's much harder to form tight beams. So you
end up having to use very large antennas on both ends, and that's just not
practical unless you're sending a whole lot of power.

Note that solar arrays are 50%+ efficient on laser light, if the wavelength
is chosen carefully to match the solar cells.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |