Thank's to all for your opinions

[wildbill hickup]

Thank's folks,

My thanks to all for your opinions and suggestions on my solar panel design. guess I'll re-think the asphalt shingle thing (Gary gave me another idea)I guess I should give all of you an idea of what I'm doing. These panels are going on the roof of a solar room, green house solarium what ever you want to call it. The entire south and west sides of which are almost solid glass the floor will be (not this year) a 4 foot layer of 3/4" crushed black stone(this year gotta settle for dirt). The room will be 10'X12' and is connected to the house, and vented into the house by a set of french doors. It will also heat the room that the radient is under. For this year I am going to put 3 or 4 55 gal drums(filled with water) on the north wall to help hold the heat and disperse durring the night. The gas water heater will also be housed in the room. If it does get really cold the water heater will come on to heat the water and the ventpipe will give slight heat in the room. I have been finishing up the shell (that's why I've been so long getting back to everyone). When finished the roof will have 12" of insulation plus 1" thermax the north wall 6" plus 1" thermax, the south and west walls all double pane patio doors (again free) and one slider(double pane) in the winter these will all be sealed from the inside with an extra sheet of 6ml plastic(an extra airgap of 2 inches)or if I have to and radient heatloss is to great I'll cut-to-fit some blue or pink insulation for nightime use to be inserted from the inside and do away with the plastic)

Gary gary, what a site (gotta go back and read all of it) for now I have another idea on the collector/absorber's I'd like to run by you.

You said, >>The alum plates that are used as absorbers can be made for less money by constructing a groove or channel using plywood that is just a bit larger than the copper tube you are using -- then take the alum flashing sheet that they sell at Home Depot and lay it over the groove -- then using a mallet, pound the tube into the groove -- this makes a groove in the alum that fits the copper tube.  Take the tube out, put a bead of silicone in it, and put the tube back in the groove and let the silicone set.  Make the tube to alum fit as close a possible -- this silicone will conduct heat well if it very thin, but  not if its thick.

I've heard that this technique works well, but I've not actually used it.<<

I assume your using the plywood as a jig. If so after setting the pipe in silicon back into the jig you took a second sheet of aluminum laid flat on top of the pipe drill and pop-riveted it to the back aluminum plate (a copper pipe sandwich)Once the silicon is dry remve the whole thing from the jig and start over. Would there be much gain in this or would it just be a waste of aluminum?? I would think at least, it would keep the collector/absorber together rather than just the silicon. Not a new idea (sorta stole it from the link you gave).

Oh ya the reason for the size is because I was given the glazing prebuilt (large windows, 3 of them) approx 3'X5' for a total collector of about 9'X5', so I would like to use them.

Well again thank's for all the ideas, I'll post some pic's when it looks like something.

[GaryGary]

Hi,

Your scheme:

"I assume your using the plywood as a jig. If so after setting the pipe in silicon back into the jig you took a second sheet of aluminum laid flat on top of the pipe drill and pop-riveted it to the back aluminum plate (a copper pipe sandwich)Once the silicon is dry remve the whole thing from the jig and start over. Would there be much gain in this or would it just be a waste of aluminum?? I would think at least, it would keep the collector/absorber together rather than just the silicon. Not a new idea (sorta stole it from the link you gave)."

That sounds good to me.  As you say, it would hold the grooved alum in closer contact with the copper.  It would also give you more contact area since the flat alum would be in contact with the copper pipe on the open side of the groove.  I don't think the flat piece would need to be full width -- maybe just enough to get good thermal contact with the grooved piece.

Gary

[GaryGary]

Hi,

Here are the results from a little test panel I made a while back that you might be interested in.  It uses CPVC pipe instead of copper, but the same techniques could be used for copper.

http://www.builditsolar.com/Experimental/CPVCCollector/cpvccollector.htm

Look particularly at the "jigs" link near the top of the page.  This would be an alternative to the groove and mallet technique that I mentioned before.  It also shows an alternative to the sheme you proposed above with a 2nd strip of alum.

Gary

[wildbill hickup]

Gary,

Thanx for the extra ideas. I think I'll still use the second piece of aluminum (slightly more surface contact), but I may put that silicone in there to take up any extra air-space. And I didn't even have to do the math to see that copper/aluminum collector is a much better investment any plastic(even though it more expencive.  

One thing though. It amazes me(in a very positive way) that such a small collector did so well with such a large radient heating plate(s)and an uninsulated bucket. I guess I'm underestamating the 'real' power in the sun.

Also it seems that your have done much with these systems(probably an understatment)Can you give me some tips on what and where to get a fairly low cost 12v pump for the circulator (plan on powering of bat/wind/solar). I have checked on line and it seems that they are pretty high in flow rate and price. That .5gl/hr you mentioned would be great or maybe 1gl/hr. I have a very limited budget for this and the copper is going to eat-up a bunch of it. I wondered about a bilge pump but most of those are designed to sit in the bottom of a boat not inline, and I don't know irf they will take the heat.

Thanx again

wildbill

[GaryGary]

Hi,

"One thing though. It amazes me(in a very positive way) that such a small collector did so well with such a large radient heating plate(s)and an uninsulated bucket. I guess I'm underestamating the 'real' power in the sun."

Full sunshine is about 1KW per  square meter -- so there is quite a bit of power there.

Your 3X5 collector will receive solar power at about 1.5 KW (about 5000 BTU/hr) if its aimed at the sun, and its noon plus or minus a couple hours.  If you build a good collector, you can capture about 60% to 70% of this.

"Also it seems that your have done much with these systems(probably an understatment)Can you give me some tips on what and where to get a fairly low cost 12v pump for the circulator (plan on powering of bat/wind/solar). I have checked on line and it seems that they are pretty high in flow rate and price. That .5gl/hr you mentioned would be great or maybe 1gl/hr. I have a very limited budget for this and the copper is going to eat-up a bunch of it. I wondered about a bilge pump but most of those are designed to sit in the bottom of a boat not inline, and I don't know irf they will take the heat."

There are some pump suppliers who specialize in PV driven pumps for solar collectors.  The best known are Ivan Labs (they don't have a website, but just google for them, and you will find a bunch of outfits that sell them), and Hartel (or Hartell?) pumps.

Unfortunately, you won't like the prices. You would also need a 20 (or so) watt PV panel, and these are not so cheap these days either.

I'm not aware of any cheap way to get a PV driven pump setup -- you need a pump that runs on around 12Volts DC, and one that can take the temperatures.  If you find something, please let us know!

If you can go with an AC pump, then there are more choices.  Grundfos and Taco pumps are very popular as circulation pumps for hydronic heating systems.  You can often find them at pretty reasonable prices on ebay.  Something like the low flow end of the Grundfos UP series would probably be fine.  You might try a local HVAC shop, and see if they have some used ones -- they are pretty durable pumps, so a used one might be fine.

If you use an AC pump you will also need a controller to turn if off and on.  The most common approach is to use a differential controller -- these turn the pump on when the collector temperature is 5 or 10F hotter than the storage tank temperature.  The most common brand is Goldline.  These are not that cheap either.  A "poor mans" controller can be done with a $10 thermal snap switch.  This is a switch that closes when the temperature goes above some set level.  You can put one in the collector, and set it to turn the pump on when the temperature goes above (say) 100F.  Its not quite as precise as the differential controlers because it does not sence the storage tank temperature, but it should work OK.  The PV driven pumps also don't sence storage tank temperature.  When you consider that your three 3X5 collectors might be collecting (1.5KW)(3 collectors)(60% efic) = 2700 watts, then having a pump that uses 50 or so watts does not seem so bad?

The thermal snap switches are used for attic vent fans, so places like Home Depot carry replacement switches that should work fine.

I think you mentioned that you were going to mount the panels on a sunroom roof.  If the roof has a low pitch, then the collectors will NOT work well for space heating in the winter.  But, low pitch is OK for domestic hot water heating.  they also need to face more or less south (say within 30 degrees).  You can download the "radiation on collector" program from my site, and see how collector tilt and orientation effect how much energy you collect:

http://www.builditsolar.com/References/SunChartRS.htm

Good Luck!