Parabolic trough tests

[netttech]

Just an update on my project. My initial attempts at a trough panel failed while trying to create a good-working trough using pvc pipe. I abandoned the idea of using PVC pipe with Mylar because of weight.

My panel has to be small & easy to handle since I can not leave the panel connected year around. If I have to construct/connect a series of panels to heat (140 degrees preferred) the water sufficiently, fine. At least they will be light-weight.

I have contructed smaller test troughs using aluminum coil which are near weightless in comparison to PVC troughs.

I tested the troughs for effectiveness recently & surprisedly the 6" trough performed better than a 7". I expected the reverse to be true. The 6" trough recorded 42 degrees increase (maxed) in 10 minutes. I am using a halegon drop-light to determined the trough effectiveness.
Later this week I am testing a form to hold the coil in a trough form so I can apply the mirrored mylar. It puckers if the mylar is applied while laying flat, then formed into a trough.

Within a few weeks I hope to have the panel completed for a true test. I will try to post pictures as I progress.
jeff

[BuzzBuds]

I tested the troughs for effectiveness recently & surprisedly the 6" trough performed better than a 7". I expected the reverse to be true.

Being the fact that aluminum if the most heat conducter used in heat sinks and due to the thickness of it. I will also be able to with stand harsher treatment than PVC also

[russ]

İs the shape identical for both troughs - parabolic shape? İ agree with you in that it doesn't seem right. Matter of fact it can not be.

@Buzz - No idea what you meant to say. Please use spell check (this time İ believe you actually did) and then edit afterwards to make sure the words are correct.

[netttech]

Yes, they are very close to the same shape (parabolic - now 4 troughs, 6"wx2 3/4"d). One has a variation only due to the fact I am re-using aluminum coil from my space heating panel. They all have a 'crook-odd-bend', in it but one has a distinct fold close to the bottom of the trough. I'm not sure how it got there. It wasn't noticeable until I made the trough.
I have 4 troughs built & today spent a good portion of the day building on the frame to support it. I also measured/cut-top-fit the copper tubing. It always take longer to construct the 1st panel.

I wanted the ability to adjust the tubing (up/down) to fit the focal point. My carpentry is not perfect so I wanted so lee-way, for that imperfection I possess. I came up an idea I believe will work. I will solder the copper & finish the frame in a couiple of days.

Jeff

[russ]

Good luck Jeff and we will be following your progress closely!

There are two applications that really interest me:
1) Parabolic troughs for higher water temperatures
2) Solar air heater

Both can be applicable for me and my location plus don't have to cost an arm and a leg.

İ liked the comment about carpentry! İ much prefer steel as for home projects normally it is possible to modify lengths or shapes as required.

[russ]

Hi Jeff - Here is the site of a guy who has built parabolic troughs - seems to be quite a resourceful and capable fellow!

http://www.ffwdm.com/solar/solar-index.htm

[netttech]

Test Results from my panel

Russ, that was a good link. Thanks

In june I finally finished my 1st parabolic panel & tested it. It weighs about 20lbs, 30"x56". The 4 troughs are 6 3/4"w x 2 3/4d. It creates a sustained 12-14 degree increase in water temp at 1-2gpm. I was using a tub of water (6 gallons) for the test, so the pool of water temperature increased also. The maximum sustained water temp was 118 degrees, with the pooled water at 93.
I am in the process of making a 2nd panel to connect in series. I suspected it would be necessary for at least 2 panels the desired water temp when I started this project.

Lessons learned: The trough should be wider & 'shallow'. I emphasised shallow because it appears on a deep trough the top portion of the trough, will not reflect onto the copper tubing. I used a common Laser to confirm the focal point/location of the tubing. About 1/4" on the top portion of the troughs would not reflect on the tubing. When I tried to adjust the tubing heighth, I would loose other reflectability.

The 2nd panel will be the same overall dimensions, with shallow troughs. I will try to post a picture of the finished panel.
Jeff

[russ]

@ Jeff - Well done and am happy to hear of your progress.

Best of luck on the next step and please let us know how it goes once again!

Russ