Author Topic: Solar Concentrator (Read 11930 times)

Frank Lussier · « **on:** October 12, 2006, 02:30:57 PM »

This is my latest project

Image 1

it's a solar concentrator. I got two dishes from neighors who couldn't handle looking at them anymore - they are relics....two 10 foot dishes. One is full aluminium and the other is black mesh. The one you see in the pix is the full aluminium..i started to take off the paint and sand it but it was going to take dog's year...so i bought some mylar online and glued it on with super 77 glue made by 3M It was not as easy as i thought...especially on a windy day...don't look at the many wrinkles!

It works unbelievably!! it just works too good...it burns wood in under 4 seconds and is melting aluminium - it's like lead dripping.

Image 2

For the concentrator i used a car heater core made of aluminium. I tried a pyrex dish as a cover (i had read that somewhere)trust me it doesn't work.it took about 10 minutes and the pyrex exploded! literally all over the yard. So now i have to find another type of extreme heat restistant glass or something to put infront of the radiator. I've rigged it up with two actuators - North/South and East/West and i also bought a solar tracker from Red Rock Energy. This will enable the dish to follow the sun. It's placed right smack in the middle of our yard...a major eye sore according to my wife - but it's just for trial (that's what im telling her) i hope to move it behind the barn in the Spring..hopefully will not blind the farmers too much. My wife is afraid i will be bringing down airplanes with the reflection.

Im looking for a tank and then i'll run the plumbing and attach to a rad in the livingroom...

I was able to bring a bucket of freezing cold water to 100.9 degrees F in less than one hour - this was my first test and it was an overcast day in the late afternoon when i did this test. Imagine a sunny high noon day!

You can go check my website http://www.junkyardsolar.com/page1.html - it's almost all up to date..but it will give you a history of my projects.

thanks

Frank

Slingshot · « **Reply #1 on:** October 12, 2006, 09:35:30 AM »

Frank,

That looks like a pretty good job covering the dish. I'll bet that the auto heater core won't last long, though, with the kind of energy you'll have available. If that's a C-band dish in your pictures, it will probably be about 8-10 feet in diameter. You're going to have a concentration of about 50 SUNs on the heater core.

I've seen a lot of those old C-band dishes laying in backyards around Dallas, and often thought it would be fun to resurrect one as a parabolic mirror. Please keep us updated on the project!

Where do you live?

Frank Lussier · « **Reply #2 on:** October 12, 2006, 09:57:24 AM »

im in Vankleek Hill, Ontario - eastern Ontario by the Quebec border..in the boonies where i can get away this project. You're right im going to have to change the heater core..im looking for an all steel radiator or something similar.

jimjjnn · « **Reply #3 on:** October 12, 2006, 11:20:47 AM »

I don't see why you don't make your own radiator from iron pipe and U type joints or combinations of L joints

Devo · « **Reply #4 on:** October 12, 2006, 01:37:30 PM »

I've heard of a fellow using to steel plates about 1/4" thick spaced about 1/8" apart I believe(you would have to play with this) then the heat transfer fluid was pumped through them & into the system.

Devin

Bruce S · « **Reply #5 on:** October 12, 2006, 02:16:58 PM »

Frank

WOW! Very nice!!

There are a couple things you could do to lessen the 50 sols impact.

One is to use a Freznel lense to defract the spot heating that'll burn threw most metals after a period of time.

Or you could use a larger heating surface, those Aluminimum heater cores are only built to with stand a max of about 300F , using something larger that is out of the

focal point of the concetrator would serve has heat sink and help the heated parts to survive longer.

There is also the way of putting the heated parts slightly off focal point which for thsi 10' Dia unit should be about 3.18' for the hotest point.

Moving it closer to the dish would actually make it less effecient but would help lessen the melting problem.

Pass along the diameter and depth of this beauty and the offset focal point can be calculated .

Cheers

Bruce S

fungus · « **Reply #6 on:** October 12, 2006, 02:43:10 PM »

By the way a 5mw laser is the equivalent of 50 suns.

electrondady1 · « **Reply #7 on:** October 12, 2006, 03:08:53 PM »

that's very impresive frank.

perhaps a ceramic could hold up under such temperatures.

something that holds molten metal

maybe a local potter could make something up for you

or you could just move the heater in so the focal point is not so concentrated

just when i was starting to get my yard tidy! now i need one or two of these.

dinges · « **Reply #8 on:** October 12, 2006, 03:15:41 PM »

Like I said before, interesting website.

Basically anything (apart from some exotic ceramics) will melt or burn when put in the focal point. Your only option is to have a flowing liquid (e.g. water) inside to cool the collector. Plus some kind of safety mechanism, that, as soon as water flow stops (defect pump, blockage in the pipe, etc.) it IMMEDIATELY rotates the parabolic antenna out of the sun. Look at the solar collector from an energy balance point of view: when more energy enters it (from sun) than leaves it (through coolant/water), it will continue to heat up.

If there are no safeties and water/coolant flow stops, the water in the collector will quickly begin to boil, steam and cause a rupture/explosion.

Maybe add 2 safety mechanisms, to be sure 7kW is a LOT of power, especially when something goes wrong.

I wonder... why don't any of MY neighbours have such dishes they want to get rid of...

Devo · « **Reply #9 on:** October 12, 2006, 03:17:08 PM »

Don't forget to keep this far enough in the air that if a bracket failure happened the dish doesn't point towards something burnable within it's "heat range" like a house or

You have probably already covered this I am just throwing it out there in case you haven't.

Devo

vawtman · « **Reply #10 on:** October 12, 2006, 03:58:33 PM »

Frank thats cool

Do you have a direct link where you got this mylar from?

I have the meshed type dish and been trying to figure what to do with it.Not anymore.

Thanks

zubbly · « **Reply #11 on:** October 12, 2006, 04:08:14 PM »

hey Frank,

great job! i have a 10 foot sitting in my backyard also. have been thinking of doing the same thing also. perhaps a project for next year.

by the way, i am about a 1/2 hour from you (Martintown), would like to see your dish up close some time.

zubbly

DanG · « **Reply #12 on:** October 12, 2006, 04:18:23 PM »

Shouldn't need to use the exact focus on something that powerful... Most metals will suffer from corrosion at elevated temperatures - a good stainless steel water block should withstand an out-of-focus heat as should block graphite, but the stainless should have mineral free water and the graphite will start to oxidize above 700°F in the presence of oxygen.

WXYZCIENCE · « **Reply #13 on:** October 12, 2006, 05:48:26 PM »

Frank, well done. Wear eye protection when you are working on the unit. That's a lot of energy you are working with. We experimented with an 18" dish that would burn a hole in paper in about 5 seconds.

Joseph.

thefinis · « **Reply #14 on:** October 12, 2006, 09:52:15 PM »

http://stores.ebay.com/Sunset-Hydroponics-1-866-395-9204_Mylar-Panda-film_W0QQcolZ4QQdirZ1QQfsubZ5QQ
ftidZ2QQtZkm

http://www.nehydro.com/store/index.php?main_page=index&cPath=8

http://www.mylarstoreonline.com/50ft.html

Here are three of the cheaper ones. I got my roll from the one with free shipping because it ended up as the best deal. Mylar is fairly tough but the mirror surface is hard to keep in good shape it is pretty tender.

Just be careful

Finis

hgp · « **Reply #15 on:** October 12, 2006, 10:34:03 PM »

Frank well done, a system i worked on some years back used special oil fed in to a heat exchanger.I dont know how far you want to go with this but its something to think about.

Herman

ghurd · « **Reply #16 on:** October 13, 2006, 12:16:58 AM »

"Moving it closer to the dish would actually make it less efficient..."

Not much, only a few percent, right?

The loss of energy would be because from the shadow on the parabolic dish? But that would be absorbed on the rear of the collector before it got to the dish just the same?

I don't have a clue how delta T would actually affect losses to the surrounding air, but believe a lower temperature on a slightly larger area would probably lose less BTUs. Like an I^2R wave theory perspective kind of thing.

Einstein would say it is better to place the collector farther from the dish. I think. I think I think?

One thing I am sure of... I need an aspirin.

G-

BTW Frank, it's great.

Extra effort was spent looking for the minor wrinkles. Be proud of it! Leave it in the front yard! I would.

Volvo farmer · « **Reply #17 on:** October 13, 2006, 06:02:04 AM »

I went outside to have a smoke this morning and got an idea. What if you put a small PV panel at the focus and pointed that thing at the moon? Probably not practical power but might be interesting to see if 50 full moons would equal one sun?

The Crazy Noob · « **Reply #18 on:** October 13, 2006, 09:57:57 AM »

Have you tought about heat engines like stirling engines?

Frank Lussier · « **Reply #19 on:** October 13, 2006, 11:11:32 AM »

Hi Vawtman

I got my Mylar at Bustan in Toronto, got a fair price

For the mesh dish I was thinking of using plywood instead of the mesh.

Frank Lussier · « **Reply #20 on:** October 13, 2006, 11:13:17 AM »

Hi Zubbly, sure come by anytime. email me at frank_lussier at yahoo dot ca so we can set up a meet.

Frank Lussier · « **Reply #21 on:** October 13, 2006, 11:14:07 AM »

yes i know i've learned my lesson already -my son and I wear our welding glaases when working on the dish.

Frank Lussier · « **Reply #22 on:** October 13, 2006, 11:14:57 AM »

I've read about the oil..it's just to find the right oil to use but it might be a very good idea.

Bruce S · « **Reply #23 on:** October 13, 2006, 11:27:26 AM »

Peter;

I agree, rotating it out of focus would be the best bet. It should rotate so that the Antenna is poiting down and not the focal point.

Rotating the focal point out of the way could be a cause for starting somehting on fire if they were close enough or blinding lights for passing planes and stuff, which of course would make for not so nice visits from the FAA.

A few years back furnace companies were toying with the idea of high temp ceramics , perhaps to mixture is available to try.

Ghurd> hows your high-temp knowledge on the ceramics you work with?

There is a high-temp oil used by GM for the older 5sp with over drive that can take it , but directly, but it does transfer heat really well. Not as cheap as buying say stright 30 weight, but would be good to pass through those coolant tubes for a close looped system with out too much to worry about overheating or freezing.

I would love to push some of the ALky I make through one of these to see how it would do under extreme measures.

Now I need to go find one and build it too :--) just to find out.

Frank; it could also be possible to use multi-farming of the heat using stacked radiators, one could be used for pre-heat to hot water tank, one for steam, one for distilling fuel.

Hummmm

Bruce S

vawtman · « **Reply #24 on:** October 13, 2006, 12:35:24 PM »

Boy oh boy Frank cant believe how cheap this stuff is.

Plywood is what i was thinkin of using 1/4 luan if thats ok.Could one just use contact cement to adhere it?

How does it hold up to the elements acid rain and stuff?

How wide is the collection area?

Is it just a narrow beam?

Im sure its uv resistant LOL

Thanks

Bruce S · « **Reply #25 on:** October 13, 2006, 01:45:33 PM »

Frank,

You have more than one dish , boy ... some people have all the luck :--))

Use the mesh it'll hold up very well. Mother Earth News did a lot of test with these sort of this back when the whole "C" band stuff came out. The Mesh won over most everything else. The holes keep it light enough so that if a wind comes up it'll blow loose the Mylar instead of sending the 10' dish after a house or something.

It's also light enough to run a tracker system without needing to use the heavy duty motors, I think if I remember the old mounts that you could make use of a 36volt motor and run it at 12Vdc with no problems.

Bruce S

BigBreaker · « **Reply #26 on:** October 13, 2006, 02:07:23 PM »

Nothing beats phase change for heat transport capacity. Put a reservoir of water at the height of the target, run a line to that target and pull the steam off the top. If something breaks, the concentrator has to boil off the whole reservoir to heat the target over 100C.

The newest commercial solar thermal concentators are looking to use this concept, it's called direct steam generation.

Countryboy · « **Reply #27 on:** October 13, 2006, 02:30:51 PM »

Hi Volvo,

That's a heck of an idea, that certainly needs looked into.

I read that the moon reflects about 7% of the sunlight that hits it. Much of the sunlight is absorbed by the moon surface. You would need about a 15 to 1 moonlight collecter to get 1 sunlight value at the moon surface.

However, since the moon is round, it reflects light in all directions. The 7% of sunlight that is reflected is scattered. We don't get a land area on earth equal to the moon which is receiving 7% sunlight at night. That 7% is scattered over a wider area.

earth 7900 miles diameter

moon 2160 miles diameter

238,857 miles distant

A 2160 mile diameter object has a circumference of 6782 miles. Since only half of the moon is exposed to sunlight, we get an arc of 3391 miles of reflective surface.

Since we are 238,857 miles from the moon, the moonlight from that 3391 mile reflective surface is now scattered across an arc 375,005 miles long.

Since the earth has a diameter of 7900 miles, it only catches 7900/375,005 % of that reflected light, or about 2% of the light reflected from the moon.

If my math is correct, the earth catches 2% of the sunlight the moon reflects. Since the moon reflects 7%, and because of our distance from the moon, we can only catch 2% of that 7% reflected sunlight. Moonlight is 0.14% (0.0014) of actual sunlight.

A 50 sol concentrator would generate about 7% of true sunlight. In order to get 1 sol output from a moonlight concentrator, you would probably need a 700-750 sol concentrator.

I took the 7% sunlight reflected from a website. I don't know how accurate it is. Moonlight can be pretty bright sometimes. Moonlight being 0.14% of actual sunlight seems low to me, but it may be accurate.

I know some of the amorphous panels produce better in low light conditions. While it may be practically impossible for DIY'ers to achieve 1 sol with a moonlight concentrator, it may be possible to collect enough moonlight that low light amorphous panels may be able to produce some power.

It's definately an idea worth experimenting with. But if you do play with a moonlight concentrator, have it 100% covered before daylight!

vawtman · « **Reply #28 on:** October 13, 2006, 02:48:17 PM »

Countryboy you forgot to factor in the stars.More omph

Countryboy · « **Reply #29 on:** October 13, 2006, 02:49:02 PM »

After doing a little more digging, I discovered the term to be googling is 'moon albedo'. (Percent of sunlight reflected as viewed from other planetary bodies.)

http://www.asterism.org/tutorials/tut26-1.htm

Cites the moon having an albedo of 0.12%, so my 0.14% wasn't far off.

craig110 · « **Reply #30 on:** October 13, 2006, 04:10:41 PM »

The moon looks bright at night only because our pupils open way up when they get acclimated to the nighttime and everything else is even darker than the moon. For a more valid comparison of the amount of light coming to us from the moon versus the sun, take a look at the moon when it is visible in the daytime sky. See how dim it is up there? Yup, that's all the light you're going to get from it.

Since folks were getting into astronomy issues in this discussion, one thing to compare is the magnitude of the sun compared to the full moon. I just googled "magnitude" to look up the magnitudes and calculate the sun / full moon difference, but found this handy page, http://www.heavens-above.com/gloss.asp?term=magnitude, that already has the answer: The sun is 400,000 times brighter than the full moon. And that is for the full moon. For various reasons (see the bottom of http://www.museum.vic.gov.au/planetarium/solarsystem/moon.html for more info), a quarter moon is only around 1/10th as bright as the full moon, or about one 4,000,000th the brightness of the sun.

Suddenly, the 50x collector doesn't look so big at night, eh? Beautiful daytime collector, though!

Craig

fungus · « **Reply #31 on:** October 13, 2006, 04:24:19 PM »

You certainly wouldnt want a moonlight reflector in the sun eh.....

Volvo farmer · « **Reply #32 on:** October 13, 2006, 07:08:42 PM »

Okay, this is the second post to suggest that this thing can burn something down if misaligned. The whole idea of a parabloic dish is to concentrate whatever hits it into a spot a FIXED distance from the parabola. For a C-band satellite dish, this spot is always four to six feet away from the center of the dish. As long as you keep things out of the 12" diameter sphere of the focal point, no burning, and probably no blinding is going to take place. It ain't a death ray, it's a concentrator.

News:

Author Topic: Solar Concentrator (Read 11930 times)