Solar concentrator increases collection with less loss

[OKIsItJustMe]

http://live.psu.edu/story/56150

Solar concentrator increases collection with less loss

Wednesday, November 2, 2011UNIVERSITY PARK, Pa. -- Converting sunlight into electricity is not economically attractive because of the high cost of solar cells, but a recent, purely optical approach to improving luminescent solar concentrators (LSCs) may ease the problem, according to researchers at Argonne National Laboratories and Penn State.

Using concentrated sunlight reduces the cost of solar power by requiring fewer solar cells to generate a given amount of electricity. LSCs concentrate light by absorbing and re-emiting it at lower frequency within the confines of a transparent slab of material. They can not only collect direct sunlight, but on cloudy days, can collect diffuse light as well. The material then guides the light to the slab's edges, where photovoltaic cells convert the energy to electricity.

"Currently, solar concentrators use expensive tracking systems that need to follow the sun," said Chris Giebink, assistant professor of electrical engineering, Penn State, formerly of Argonne National Laboratory. "If they are a few tenths of a degree off from perfection, the power output of the system drops drastically. If they could maintain high concentration without tracking the sun, they could create electricity more cheaply."

LSCs can do this, potentially concentrating light to the equivalent of more than 100 suns but, in practice, their output has been limited. While LSCs work well when small, their performance deteriorates with increasing size because much of the energy is reabsorbed before reaching the photovoltaics.

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[ChairmanAgnostic]

1. frensel lenses have incredible properties.

[OKIsItJustMe]

2. They do! but I don’t believe we’re talking about simple Fresnel lenses here.

Fresnel lenses have been used in solar concentrators for a while now.

[txlibdem]

3. Fresnel lenses used to concentrate more sunlight onto a solar panel increases its output 20-30%

One can use mirrors can do the same thing. More light shining onto the panel equals more energy out.

[madokie]

4. I've got a fresnel lens about 3 ft to the side

It'll set the grass on fire before you even find the focal point. I guess I should try using it for something but too many jobs to do otherwise to put much effort into it.

[txlibdem]

5. Here's a tip, be careful with the focal point...

DO NOT put the solar panel in the focal point. That will burn the solar panel and you'll have an expensive hunk of plastic.

Watch this video... it's from a seller on eBay that I've been rooting for since he put up his first item. He has a zillion free videos on his site and a lot of them are funny and all are interesting (IMO). GreenPowerScience is his eBay ID (IIRC).

http://www.greenpowerscience.com/ - the home page
http://www.youtube.com/watch?v=-yh1q59a1h0 - Here's their video of boosting solar panel output w/ fresnel lens.

--- shows about a 50% increase in solar panel output...

PS, I love this guy! He has done so many experiments with solar (not all of them turn out right and he doesn't remove the bloopers or the failures).

"GREENPOWERSCIENCE" is his youtube channel.

PPS, I'm not in any way connected to this person. I am only sharing what I find interesting.

[madokie]

6. I'm an experimenter too

Thats how I know some things to be fact cause I've already done whatever it takes to get me there.

Thanks for the link
I'll share it with my neighbor who is in the process of building a solar collector using mirrors that will track the sun to heat his shop. I'm sure he'll glass on past it but I'll send it anyway

For me I'll treasure it as you seem to do. :hi:

[txlibdem]

7. Not to take credit or anything... but I posted something similar months ago

That's a great idea, what you neighbor is doing. I would suspect that since he wants to keep the reflected sun shining on a single point (his shop), he'd have to mount them on tracks as well as have 2 axis control of the mirrors?

[madokie]

8. No he is tracking the sun keeping the mirrors focused on a heat exchanger

made of a coil of stainless steel 1/2 inch tubing encased in some melted beer cans, aluminum. He is putting the storage inside of his shop in one corner and circulating the water/antifreeze solution though the heat exchanger. He is using a heat exchanger, an auto radiator with a fan on it to warm his shop with. Tracking from east to west will be electronically controled but the up and down he'll have to do by turning a screw to keep it focused that way. He figures he'll only have to change that weekly or so.
After he gets the mirrors and heat exchanger finished I'll pm you a picture of it so you will know what he did. :hi:

[txlibdem]

9. Thanks I'd appreciate that

It sounds like a simple yet effective way to get free heat from the sun!

[txlibdem]

10. I just had a thought about using mirrors in that way

As we both know, there are only a few hours of "peak" sunlight during each day and the output of a solar panel drops off sharply (sometimes down to zero, sometimes to just a trickle) outside of those hours.

So imagine the solar panel mounted not flat but at an angle to catch the most sunlight from the mirrors. Say that 10a to 2p is the peak window in his area. So he starts off with two mirrors focusing on the solar panel. Then at 3pm he rotates another mirror and aligns it toward the solar panel, then at 3:30p another, then at 4p another...

He could conceivably increase his "peak" number of hours of sunlight from 4 to 6 hours or more by doing that, all while increasing the output due to the mirrors during all that time.

PS, something would have to be done about cooling off the solar panels so either a heat fin or (better yet) the first stage of a solar water heating system zigzags behind the solar panels to keep them cooler -- a cooler panel gives a higher output but the mirrors would tend to increase their temperature and might shorten their lifespan. So once the water moves along the length of the solar array it would then go to the actual solar water heater (and / or) solar pool heater.

[madokie]

11. He is using 64 10x 10 inch mirrors

each mounted on an aluminum plate that has a swivel on the back of it so he can aline each of them to shine on a heat exchanger that will be mounted out in front of the array of mirrors that is a ball of aluminum with the stainless tubing in side it. He has a tracking apparatus already made and the mount so he can move the array of mirrors in focus to the heat exchanger as the sun tracks from morning to evening. If the sun is out he will have roughly 64 sq ft of mirrors focused on this exchanger that is about 12 inches in diameter. It is made of 20 ft of 1/2 stainless tubing with aluminum poured around it so all you see is the pipe sticking out a foot or so to connect to. It looks like a slightly flatten ball of aluminum that has two pieces of stainless pipe sticking out the back side.

I just came in from doing some welding on it for him. I am beat

He made his own tracking unit to track it with using a few leds to turn on a gate to a transistor to move the motor that moves the frame to keep it in focus. He has this home made tracking device mounted at the end of a 2 ft of 2 inch pipe. When the sun comes down the tube it turns the tracking motor on until it no longer shines on it then it stops to be repeated as the sun progresses across the sky. Dry runs it works great so far.

[txlibdem]

12. Mirrors would work great to enhance both solar PV and solar thermal (your friend's project)

My earlier post was describing a system of mirrors to be used with solar PV panels...

Whoops, I didn't notice your reply was for a solar heating system!

[txlibdem]

13. I think I've seen something like this on the interwebs

So in essence, you are concentrating 64 square feet of sunlight onto one square foot, multiplying the heat from the sun by 64 times.

Doesn't he have to use flexible hoses... or is the target (exchanger) stationary?

[madokie]

14. Yes he will be using flexible hose

A short piece of insulated heater hose and he'll be fixed up. This is a work in progress and as he learns new things he'll make changes. We're both old men who have grown up tinkering, making our own toys so this kind of a project is right down he and I's alley.

The exchanger is mounted to the frame that the mirrors are mounted to so they are always in the same place in relation to one another. the whole thing tracks the sun as one unit so the focal point is always at the same place.

[txlibdem]

15. Oh man! I want one!

But our HOA forbids anything that collects or concentrates sunlight. Sounds like the oil companies had a hand in writing out that HOA document, eh?

On edit: Flexible tubing such as PEX? Or another similar?

[madokie]

16. I'm not sure of what he'll use

I'm a pex man myself so if it was left to me thats what I'd use. I think he's going to use heater hose for autos though

[txlibdem]

17. Well, auto hose will handle the heat

And that baby will be putting out some heat, that's for sure.