

My Solar Energy Idea - scobar
http://scottbarbian.com/my-solar-energy-idea

======
deeviant
I worked in a CPV(Concentrated PhotoVoltaic) start-up. We used Fresnel lenses
printed on cheap, rigid, inflatable substrates to focus highly concentrated
light on very high efficiency multi-junction cells(with real-world
efficiencies of >40%), using high precision independently tracking platforms.

A few points:

* Simplicity is success, the more complicated your process is, the more likely it will fail. Our rig was complicated, but your proposed solution is much much more so.

* CPV is the leper of the solar industry, nearly every player in the CPV space is dead or dying, and most VC's avoid it like the plague.

* With any high concentration CPV system, you will not generate power and potentially melt/destroy your rig if you do not have an accurate tracking system, which are expensive and often require constant maintenance.

* Quantum dot solar cells basically don't exist outside of theory. The highest efficiency I've heard coming lab examples is somewhere below 10%. Multi-junction cells, although expensive, do exist and are obtainable(spectrolab, etc).

* Every time light reflected or otherwise interacts with a non-vaccum medium, it loses energy. CPV system should be designed to interact with the light as little as possible, while the above design seems to maximize interaction.

* Module costs are in constant decline and unpredictably so, it is extremely dangerous to build any business module based on current 1-sun panel prices (see solyndra).

* There are massive infrastructures in place to deliver electrical energy, while very few to deliver light energy, and none at all to deliver this sort of high energy light. In short, it would be far more technologically and economically efficient to deliver power to areas remote from the generate site by converting it to electricity.

* In reference to your comment related to shifting the light to a specific frequency: It is very difficult to shift the frequency of light, and there are losses and limitations ( see raman shifting). If you could design a system to shift wide band EM radiation to a single band, cheaply, without significant losses, you would have revolutionized no just the solar energy sector, but a great many other industries as well. I have seen prismatic systems which split light into different bands, each which are channelled to a solar cell with a matching band gap, but once again, the cost and loss made this approach uninviting.

* In short: How does this unit track the sun, as that's the first hurdle to handle with any CPV solution. Then what are your optical losses? What's LCOE can be expected from this sort of design and how does that compare to a 1-sun type module bench mark. What are the benefits of this design of current designs? If you are looking to build a product, you should define a MVP: a simple demo that can demonstrate value to somebody. If you are trying to assist the world in general with intellectual philanthropy, I would better define how this system could be expected to perform, and how is it better/cheaper/whatever-er than the current systems.

~~~
scobar
First, thank you for your thorough response. You have more experience than I
do in this domain, and I really appreciate you taking the time to offer your
insight.

> With any high concentration CPV system, you will not generate power and
> potentially melt/destroy your rig if you do not have an accurate tracking
> system, which are expensive and often require constant maintenance.

For the tracking system you mentioned to protect the rig, do you mean sensors
to monitor energy throughput/system temperature/etc.?

> Quantum dot solar cells basically don't exist outside of theory. The highest
> efficiency I've heard coming lab examples is somewhere below 10%. Multi-
> junction cells, although expensive, do exist and are obtainable(spectrolab,
> etc).

Do you know if the reported efficiency of quantum dot solar cells is based on
input of the entire solar spectrum or from a single frequency? Do you know if
multi-junction cells (or a different technology) would convert a laser into
electricity more efficiently? As I understood it, multi-junction technology
was specifically designed to better handle multiple wavelengths.

> In reference to your comment related to shifting the light to a specific
> frequency: It is very difficult to shift the frequency of light, and there
> are losses and limitations ( see raman shifting). If you could design a
> system to shift wide band EM radiation to a single band, cheaply, without
> significant losses, you would have revolutionized no just the solar energy
> sector, but a great many other industries as well. I have seen prismatic
> systems which split light into different bands, each which are channelled to
> a solar cell with a matching band gap, but once again, the cost and loss
> made this approach uninviting.

Achieving a wide-to-single band shift with minimal loss was the mark I was
aiming for, and I hope someone figures this out in my lifetime. I'm curious to
see how near or embarrassingly far I was from the target.

> In short: How does this unit track the sun, as that's the first hurdle to
> handle with any CPV solution. Then what are your optical losses? What's LCOE
> can be expected from this sort of design and how does that compare to a
> 1-sun type module bench mark. What are the benefits of this design of
> current designs? If you are looking to build a product, you should define a
> MVP: a simple demo that can demonstrate value to somebody. If you are trying
> to assist the world in general with intellectual philanthropy, I would
> better define how this system could be expected to perform, and how is it
> better/cheaper/whatever-er than the current systems.

I was taking the 'intellectual philanthropy' route, but I really am curious to
learn my inaccurate assumptions and misconceptions about the idea as well. The
first metrics I'd like to test are the energy lost between the solar radiation
input and laser output as well as the amount of loss recuperated by converting
the waste heat to electricity or a laser. If the efficiency were not
substantially better than directly pumping a NdCrYAG laser with solar
radiation, then the idea would not be worth pursuing.

My underlying goal with the idea was to reduce the cost of electricity and
reduce consumption of fossil fuels to produce electricity simultaneously.
Thank you again for your input and your time.

~~~
deeviant
> For the tracking system you mentioned to protect the rig, do you mean
> sensors to monitor energy throughput/system temperature/etc.?

For any concentrated PV system, you make use of only the direct normal
isolation of the sun. All of the optical geometry (must) assume the usable
light is coming in normal to the apparatus. Because the sun moves(well because
the earth moves really), your apparatus needs to move too, in order to track
the sun and maintain the normality of the incoming radiation, any deviation
from normal will change the point in which the concentrated light will
strike(which in this case is whatever receiver apparatus the rig is using). So
the tracking system I am taking about is the apparatus that continuously aims
the apparatus at the sun. This is not an easy problem, as you do the math and
calc all the angles, but slight imperfections(which we found to be generally
non-linear and thus quite hard to calibrate out) in the geometry of the rig,
unevenness in terrain and other factors(you would be suprized on how many
factors and affect this <wind, a flock of pigions sitting on the device,
thermal expansion of the structural components of the rig, etc>).

> Do you know if the reported efficiency of quantum dot solar cells is based
> on input of the entire solar spectrum or from a single frequency? Do you
> know if multi-junction cells (or a different technology) would convert a
> laser into electricity more efficiently? As I understood it, multi-junction
> technology was specifically designed to better handle multiple wavelengths.

All reported efficiency of quantum dot solar cells is based on wide-band solar
spectrum, since this is the only practical spectrum we have to operate on (
see below).

> Achieving a wide-to-single band shift with minimal loss was the mark I was
> aiming for, and I hope someone figures this out in my lifetime. I'm curious
> to see how near or embarrassingly far I was from the target.

This actually may be theoretically impossible. As mentioned in my previous
response, a discovery that can do this would be a huge advance for a great
many fields and applications.

> I was taking the 'intellectual philanthropy' route, but I really am curious
> to learn my inaccurate assumptions and misconceptions about the idea as
> well. The first metrics I'd like to test are the energy lost between the
> solar radiation input and laser output as well as the amount of loss
> recuperated by converting the waste heat to electricity or a laser. If the
> efficiency were not substantially better than directly pumping a NdCrYAG
> laser with solar radiation, then the idea would not be worth pursuing.

My underlying goal with the idea was to reduce the cost of electricity and
reduce consumption of fossil fuels to produce electricity simultaneously.
Thank you again for your input and your time.

Good luck with your continued efforts, my only suggestion would be to focus on
one thing at a time, and do due diligence on the assumptions made. It was my
pleasure to add my comments, solar power is the energy source of the future
and increasingly, it's the energy source of today. I'm always glad to see
inquiring minds pondering ways toward pushing the technology forward.

P.S.

If anybody ever gives you grief for supporting solar, just tell them you are
looking into wireless fusion technology, which actually produces more energy
than it consumes (which, I might add, is entirely true).

