Breakthrough in Solar PV?
Here’s a video on a new approach to solar PV that claims to double the efficiency from about 18% to 36%. But I can’t see how anything these people say could possibly be true (beginning with the current efficiencies, which are in the 20s).
The principal claim is that this device tracks the sun without moving, by employing a patented nano-technology to focus the sun’s rays onto a tiny point. But a flat panel that does not physically track the sun is going to encounter the same math and physics that the Earth does in its revolution around the sun. The reason summers are hotter than winters (and afternoons are hotter than evenings) is the difference between the sun’s being close to directly overhead, vs. hitting the Earth’s surface at a low angle, lessening the sun’s intensity by the cosine of the angle made between the sun and the surface of the Earth. No technology, patented or otherwise, is going to change that basic fact.
I’m fairly certain that’s correct, but if anyone wants to challenge me on it, I’m all ears.
Craig,
You are ALMOST correct.
If the earth had no atmosphere you would be correct. However, the lower the sun is in the sky, the longer the ray path is through the atmosphere and the atmosphere absorbs part of the radiation received from the sun. Thus, insolation decreases to a value significantly less than indicated by the cosine of the angle. I lack sufficient information to quantify the effect.
@ Frank and Craig you both are right though I too can’t cite the exact reasons for the precise change in Sun s Rays either. Just know it from the industry and design factor’s used currently .
As you said Craig these folks are probably stretching things as the Albedo , condition of the sky like dust , wind negative effects ( reflection and the tendency of flat panels to not be able to concentrate the sun s light waves all limit the over all efficiency.
The condition of the sun s rays, the air and cloud cover limit the use of so called concentrated solar CPV to only a few regions of the world. That retards their acceptance plus stubbornly higher prices but they do reach 35 to 42 % in STC tests and do well in the field. But lower cost pv blows them away in the market place so most players have exited the marketplace.
As of today there are 3 manufactures all large co that are claiming or have tested and claimed Efficiency around 21 to 23 % for regular pv. they are using special coatings and backings to boost cell production along with power optimize rs that are getting good results at a low marginal cost.
However , they dont specify if that is a STC value in the lab or a PTC value ( in the field actually performance etc) .
If some one knows please Post
The new breakthrough seems to be the Perovskite cell and panel design which features a added layer onto the existing cells. these are reaching high 28 % to low 30 % in STC tests at different Universities.
some folks are hanging their hopes on this improvement which would really be a big Boost.
Actually Huge as right now we are installing high performance poly / mono pv with the Bells and whistles and we are delivering LCOE of KWHr of 5 to 7 cents per kwhr w 4.9 % financing costs and $ 3.00 per Watt so solar is way below GRID Costs beyond parity we are setting the BAR.
so all the carbon heads are really getting worried as their future profits are at RISK ….and the nuclear Genie lovers well they have a long long way to go to get their cost structure right.
When they do they will have a place at the Table till then it is Blue Skies and Sun Rays ! making power cheaper than the GRId in SW states with low low gas prices. so get over it Carbon heads ! Of course the Trumperian ERA may cast long shadows on things things are going to HEAT Up in many ways. TBD later
Craig I doubt they can do what they claim.
First off there are different types of solar cells. A single junction cell last I saw had a theoretical efficiency around 27% but you have record efficiencies with triple junction cells around 53%. But in order to make these high efficiency cells economical solar tracking must be incorporated into the system. This way the cell area is smaller but receive far more light. There are PV chemistries based on other than silicon that represent different potentials so I would not be surprised at increases beyond today’s limits.
When we look at solar tracking we have the example of parabolic trough solar thermal collectors that only need to track in one direction because they are oriented east-west.
In the history of solar PV, one type of concentrated solar PV array places small mirrors on a flat panel on the ground that does not move. Suspended above it is a small “target” of high efficiency solar cells. Many small mirrors on the flat panel that does not move are motorized and track the sun like the parabolic trough solar system in only one direction.
Cheap PV panels have made such complex systems a bit obsolete. But the technology of capturing more sunlight with essentially flat panels has a history. Another configuration used nanotubes to essentially trap photons in a nano well.
The system in this article seems to spring from this kind of research and uses a parabolic lens to focus light. There also seems to be some kind of focusing or movement within the flat panel even though the panel is not moving.
So I wouldn’t dismiss the claims immediately out of hand. But the problem with such systems is that they tend to be costly and the solar cells don’t stand up under the more intense heat. When comparing such systems to typical flat panel PV it is not quite apples to apples.
I imagine such a system would have value where it is not possible to tilt the panels toward the sun and they must be horizontal, on an airplane wing for example, or an electric car.
Craig,
Silent Running is completely right. It is Concentrated Photo Voltaics.
They use very expensive but high efficient PV cells, normally only found in the lab.
If you concentrate the light 300 times, the surface of your PV cell is 300 times smaller. If your PV cell is 100 times more expensive for the same surface, you still spend 3 times less for your PV material.
Of course you then need to add the lenses/mirrors and the tracking system. Instead of using 1 big lens, they use lots of small lenses. That reduces the distance they have to move the lenses and the price of the tracking system.
Using lost of very small PV cells also helps with the cooling which is also a problem with Concentrated Photo Voltaics. There is no mistery here.
You win by using less PV surface. This allows you to use higher priced and more efficient PV. You loose by using a complex system with lenses and tracking.
As Silent Running pointed out, it only works good with direct sunlight. Cloudy skys and diffuse light does not work. This is similar to concentrated solar thermal.
I bet they count on the fact that their lab PV cells will get a lot cheaper when made in a factory instead of a lab. They need to scale it up to be competitive. That will cost a lot of upfront money before it is profitable.
They are not the only one looking into Concentrated Photo Voltaics. I known IBM is looking into the cooling problem. I think that IBM wants to combine solar thermal and photo voltaics in 1 device.
In the end the economic value will decide which way is best.
Mark
Craig,
Here a link to the work of IBM.
Heat, cooling, desalination and electricity in 1 machine.
http://www.huffingtonpost.co.uk/2013/04/22/ibm-solar-collector-hcpvt_n_3130544.html
Mark