using a parabolic mirror with PV?

[dimtick]

A while ago I saw a Discovery channel show (Invention Nation....I think) and they had a guy that was using a mirror arrangement to focus light onto a small pv cell.  He was able to get power levels much much higher than the size of the cell.

has anyone here experimented with this?  

I don't have the land for this but thought it was an interesting concept.

Fixed the Title typo. Sorry it got a couple comments before I caught it.

[Sparky01]

Yes I have thought of designing a system that uses parrabolic mirrors. But the main concern is heat generation and PV panel degradation. It would not be wise to get more output and cut the life of the panel to only a couple of years. The design that I have drawn up (have not done it yet due to too many projects) is to use a temperature sensor mounted on the back of the panel. And if the temperature gets too high the mirrors (that are mounted on a hinged arm with an actuator) would turn back out of the way to remove any reflexion. It is alot to build into a system, especially when it is also a tracker mount. Primarily I was going to use it in the winter when it is very cold (0F to -30F).

[DamonHD]

It's one form of CSP (Concentrated Solar Power), eg:

http://www.businessgreen.com/business-green/news/2215513/satellite-solar-panels-promise

(though they apparently wouldn't know their Amp from their Elbow given their units abuse...)

Rgds

Damon

[GaryGary]

Hi,

I believe that the designs that use a lot of concentration use PV cells that are designed for this.

If you want something that will work with regular PV panels, then maybe something like the 'ridge' concentrators would be more workable?

http://www.builditsolar.com/Projects/PV/pv.htm#Tracking

(see the three entries that show the ridge style concentrators)

It seems like the combination of tracking and mild concentration from the reflectors would give quite a worthwhile collection increase without stressing the PV panels?  Especially if the panels are mounted in the open for good cooling?

Gary

[fcfcfc]

Hi:

Concentrating and tracking the solar energy is the greatest challenge whether you are targeting PV, Sterling or other energy devices. Survivablity outdoors of such systems without constant maintenance is not easy... You need to be in clear sky country as well, where most of the energy most of the time is not diffuse, I.E. not the Northeast. Concentrating solar is great for demos with "drama" though....

.....Bill

[auspiv]

now i'm not sure about water's absorption of sunlight, but could you place a piece of glass over the top to create a thin (.5cm - 1cm) film of water? then it'd be circulated to cool the cell while heating some water.

[ruddycrazy]

now i'm not sure about water's absorption of sunlight, but could you place a piece of glass over the top to create a thin (.5cm - 1cm) film of water? then it'd be circulated to cool the cell while heating some water.

50-100 mm of water on a glass pane :| come on those figures must miss a decimal point or 3 .

[SteveCH]

When I was shopping around for some new, additional pv panels a few yr. ago, many manufacturers stated in their info' that the panels they made were not intended for concentrating systems like this. The ones I bought stated so in the warranty. However, you could make some or use some that you were willing to sacrifice if necessary, for experimentation. I've often thought that using some other devices such as flat mirrors to reflect more light towards the panels might be ok. There might still be an issue with the engineering of the panel circuitry...more amperage being produced than they reasonably expected. I would definitely try things out on a panel I was willing to lose first....

The heat produced by parabolics could be an issue for the substrate and sealant even if the cells themselves were able to withstand it. There have been some companies [Arco for one] who did a bunch of experimentation with these sorts of things back in the eighties. Don't know whether one could get hold of the data....

[auspiv]

.5cm = 5mm.. any thinner and it could be difficult to keep uniform spacing, but if you could pull it off i suppose thinner is better.

[Ungrounded Lightning Rod]

I got hold of some of the old panels retired from that experiment.

They had a brown discoloration over much of the surface of each cell - where the concentrated sunlight hit the cell.  The light had discolored the glue used between the cells and the glass, drastically reducing the efficiency of the cells.

I believe they went with a different glue for the production panels as a result.

Nevertheless, using a concentrator is very problematic for a panel.

For starters, only a small percentage of the incoming light is converted to electricity.  The rest ends up as heat in the cells.  Multiplying the incoming light multiplies the heating of the cells.  If you don't provide additional cooling they'll get hot enough to reduce their output significantly.  (They may also melt, re-diffuse until they're not functioning properly, or expand/warp until they crack or cause some other failure, etc.)  If you DO provide additional cooling you may end up exposing them to water, which rapidly destroys them.

Yes you can get more out of them with a concentrator - even a big parabola with a large multiplier.  But the panels are not designed for this and it's not easy to design workarounds for them.

[Ungrounded Lightning Rod]

Also:  A substantial portion of the losses in a panel are voltage-drop losses in the coating and interconnect wiring.  Multiplying the solar input leaves the generated voltage untouched and multiplies the current output.  But resistive losses go with the SQUARE of the current.  So you lose output voltage at the terminals and efficiency in the panel at the multiplied solar input levels.  These extra losses add still more heating to the panel.

[GlutealCleft]

So... are cells made for concentrating available to the average joe?  Any links?

I can think of several ways to very cheaply concentrate a fair bit of sun....

[Tritium]

Why could one not build one from bare cells by gluing (Arctic Alumina like used on high power leds and CPU heat sinks) them to an aluminum or copper block with water channels cut in it and cover it with a window of fused silica (very low expansion at high temps). Not cheap, but not astronomical in price either.

Thurmond