Solar Panel Question.

[RandomThoughts]

Just like with the wind mill funnel thing. Couldn't solar panels be made cheaper by increasing light on cell, and lowering the amount of cells actually on the panel?

Just watched this film on how they make a solar panel
http://www.greentechnolog.com/2007/10/solar_panel_construction_demonstration.html

I don't know much about solar power, but saw an interesting show on space elevator test using mirrors on solar panels. It keeps me wondering.

If the problem is output of solar cells per cost of manufacturing. just like in the wind example, why not use cheap reflective surfaces to increase the amount of sunlight that hits a solar cell.

I was looking at the solar farms, and they are all rows of solar panels. You would think they would double light on cell surface with a cheap mirror surface.

In the same respect, why not make the solar cell itself allow for magnified light.


bottom surface of solar panel would be same as they are now, but every other row is left blank.

Then above the blank spots would be a layer of simple glass that would refract light that would hit blank spot to hit a cell spot. So when light hit glass, light that would have gone to panel still does, but also light that would have gone to blank spot gets bent by lensing above panel to hit a cell also.

So you could get same size panel, same output, with half the actual cells on it.

_______________ Current panel design.


\___/\___/\___/ Mirror approach, Bottom lines are solar cell rows, the slanted edges are reflective surfaces that point light to cells. so you get close to same amount of light on cells, but need half the cells. This of coarse assumes that the cells are not at peak production already.

-__--__--__--__- This method would not bounce light to adjacent surface, but would just curve it by making the dashes little lens that change light path to adjacent cell. Again you could get same light on cells, using half the cells.

So output per square foot of Panel would go down, since not all light would hit cell, but Cost per watt would also go down. 50% cost, 85% of the power output, compared to a full panel.

Alternativly, the actual cell itself could incorporate some light bending within each cell itself, a small row of raised reflective surface between surface that generates power.

Doesn't this make sense?

[Dogmudgeon]

1. Most of the recent efficiency breakthroughs do just that

In the last week, there were press releases posted here about at least two "best-ever" achievements in PV tech, as well as a scheme to use reflective balloons to amplify infalling light. Almost all the action these days is in this area, since we are close to the physical limits for the developed solar/PV technology, which is about 7-10% conversion. The ultimate limit could be as high as about 50%, based on what I was reading 2-3 years ago, but that number could be higher by now.

--p!

[RandomThoughts]

2. You mean like hot air or helium balloons

suspended above the solar farms?



.0........0
..______.. Like this
where the balloons refract light to the farms?

[Dogmudgeon]

4. I think they stay tethered to a ground frame; they're used to collect light

I think this is the post: http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x177633">Cool Earth Is Scaling Up Solar Energy Generation (solar balloons)

Here is the original article: http://www.renewableenergyworld.com/rea/news/story?id=54228">Cool Earth Is Scaling Up Solar Energy Generation

The "problem" is that solar energy is still, at best, a small-site solution, and most of these corporate press press releases are wildly optimistic. But I think the future of solar technology will be in novel uses of originally low-tech ideas; only the PV cells will be super-high-tech.

The use of balloons as light collectors (among other things) actually HAS been proposed, in several forms, as space technology.

--p!

[RandomThoughts]

13. Great link thanks

And while you got the pole up there already, and the power lines leading away from it. You might as well slap a windmill rotor on the pole too :)


The downside of that tech is it requires manpower. It must be regulary serviced. This is not a downside. It creates jobs which is a plus. Of coarse labor cost have to be calculated in cost/benifit analysis, but if you get a comparable one that also creates jobs, its a win win.

[RandomThoughts]

6. found this one

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x178119

Yea this thread was interesting, sounds like it uses a material like a fiber obtic, to direct photons to a cell.


Really cool sounding, like a piece of glass made from two one way mirrors, so all the light hitting it goes in, then does not come out, but bounces down the sheet to reach a row of cells at the end.

[RandomThoughts]

3. Hows this.

Instead of rows of panels.

You turn panel upside down and then have each panel get the light
from two rows of mirrors on each side of panel row.

[HillbillyBob]

5. Yes you can increase the power generated by focusing mirrors but the mirror

gets to be more expensive than the panels. I checked with suppliers and manufacturers.
I want to build a solar oven, normal mirrors will only last about 2 years exposed to weather the silver tarnishes and turns black because the backing cannot be sealed properly so mirrors that cost about 140$ will cost over 500$ for longer lasting mirrors will last 7 10 years that would be enough to use on 2 or 4 panels. We have to have a better less expensive way to do it. Polished metal is more expensive yet closer to 1000.00$, but the upside is that they can be polished again.
No idea of the cost on that though. Focusing fresnel lenses would work, but I have not been able to find them and a cost for glass fresnel lense only plastic which will yellow in a few years. Pronounced fren el s is silent, is the same tech used for lighthouse lenses and the newer auto headlights.
If we could ever get the powers that be to get off their asses and get the production level up the price will come down.
It looks like the powers that we have elected do not serve us, they want to plunges us into serfdom and be dependent on central power supply.

[Blue Meany]

7. You can get fresnel lenses for a reasonable price on ebay...

be sure to get a linear lens that spreads out the concentrated light or the hot spot will be too concentrated to use for cooking, as you may melt the cooking vehicle, at least if it is aluminum. I'm thinking of using chrome paint or aluminized mylar as an alternative to mirrors.

[RandomThoughts]

8. Well the political possiblitiies

You could make a case that if everyone had enough food, shelter, health care, and power. It would be alot tougher for some centeral organization to hold anything over people.

But I am going to assume people that think like that are on there way out.



But on the panel question. Are you saying a mirror is more expensive then solar panels?
You could put a piece of tinfoil under a piece of glass and get a really cheap light reflector.

a mirrors power is it reflects exactly as it catches light,

but you could get away with just reflection, and accept some scatter.

[mopinko]

10. solar ovens are out there.

they had them as a premium on my local npr station a couple of years ago.

[garybeck]

17. not really

mirrors are not the problem. actually you don't have to use real mirrors. you can use any reflective surface, like polished sheet metal. you can also use fresnel lenses on top of the cells, which focus the light onto a small area.

the problem is not the mirrors, but the PV material itself and the glues that are used to adhere the the cells to the glass on top. both crystalline and amorphous PV material actually decrease output as temperature goes up. the other materials do not respond well to high temperatures.

these are all problems that could be solved with more r&d but the cost of implementing the solutions must be less than the just buying more PV material, and as the cost for that goes down, it's hard to say which will be more cost effective in the future.

[tinrobot]

9. It's being done -- look up concetrator PV systems

Start here:

Several advantages of concentrator PV systems, as compared to flat-plate systems, can be enumerated. Concentrator systems increase the power output while reducing the size or number of cells needed. An additional advantage is that a solar cell's efficiency increases under concentrated light. How much that efficiency increases depends largely on the design of the solar cell and the material used to make it. Another advantage is that a concentrator can be made of small individual cells. This is an advantage because it is harder to produce large-area, high-efficiency solar cells than it is to produce small-area cells.

http://www1.eere.energy.gov/solar/concentrator_systems.html

[Fledermaus]

11. PV panels work better at lower temperatures

Increasing the amount of sunlight raises the operating temperature and decreases the efficiency.

Effect of Temperature on Solar Panels

The graph above shows the relationship between temperature in degrees Celcius (horizontal axis) and the solar panel power output measured in milliwatts (vertical axis). Because of the way the halogen lamp took one minute to reach full brightness the results from 25-30 degrees Celcius should be ignored.

Between 30 and 42 degrees there was only a small drop in power output from a peak of 749 mW down to 730 mW. After that there was a consistent drop in power output of around 8.3mW (1.1% of peak output) per degree rise in temperature. Voltage under load went from a peak of 6.21V at 0.12 Amps down to just below 5V at 0.09 Amps.

The total power loss due to the increase in temperature was from around 750 mW down to just 458 mW - a fall of almost 40%! Had the solar panel been pre-cooled in the fridge before the experiment was started the peak power output would certainly have been even higher.

http://www.reuk.co.uk/Effect-of-Temperature-on-Solar-Panels.htm

[garybeck]

12. Many have tried to do this, but.............

Good question!

The answer is, many have tried to do this. However the problem is that the materials currently used to make PV panels actually don't like to be very hot. The hotter they get, the shorter their lifetime and the less relative power they put out. The actually perform best when they're cold!

There is some new research and hopeful results from new things they are trying, to disperse the excess heat and resolve the other problems.

There have been concentrator modules on the market a few times. But the companies all went out of business because of these problems.

It's possible that there will be new concentrator modules on the market, if the new developments in the lab can be translated to industry.

[RandomThoughts]

14. Reply to both 11 and 12

Thanks for links,

And the heat issue does make sense, it creates the diminished returns in both output and lifespan that would have to be overcome to use reflective.

you wouldn't want any cooling system, since that would take power, I wonder if you could fill the blank rows between cells with heat sinks to water to radiate heat off the cells, and then that heated water(with enough cells) itself could add energy to be collected.

So a combination, you take the current mirror system used to heat water, but between the water and the light source is solar cells that generate electricity, and gather some heat to be radiated into the water.

Some mirror to water only systems would also be needed to reach steam temperature, but some energy could be pulled off heat of solar panels, and cooling of panels would also occur.

Thinking about it, you wouldn't want to use water, but find a liquid that absorbs energy to transfer from liquid to gas state at lower temperature. If there is one. Alcohol boils lower then water, but you would want to find one that boils even lower, at a temp compatible with max heat exchange radiating off of cells. Are their gases that absorb that extra liquid to steam energy around 60 celsius?

[conscious evolution]

15. In theory it should work.

I do know this.In the early eighties a friend of the family invented an improvement for solar water heating panels using a similar idea.His idea increased the efficiency by 50% or so.
GE bought the patent from him ,though,and stuck it on a shelf never to see daylight again.

[garybeck]

16. this is what happens to PV panels with concentrators on them

the Carrizo solar power plant was a huge utility scale project with mirrors on the panels. After a few years they realized that the panels were decreasing output, because the encapsulate glue between the glass and the PV material was turning brown due to the intense heat. The entire plant was decomissioned and the panels were sold off to retailers very cheap. I personally sold probably thoudands of them. once they were taken off the mirrors, the power output stabalized, and they were sold cheap, so it worked out for the end users... but everyone learned why concentrators don't work, the hard way.