Solar collector performance help please.

LOL...yeah, you speak sense. I was going to do that, just use PV and elements. Easier to control. Simpler to install. But I would have to go out and buy it all. I have a lot of the materials needed for this project just sitting in store rooms and I refuse to sell expensive radiator tubing for scrap value. If I could re-purpose it and put it to use it sounds interesting. Out of all the stuff I need to build this, I only need to buy the electrics, the pressure storage tank and the glass. I would have to buy the pressure tank anyway with electric. It is a lot of work though, but also an interesting project for my Sons. Both in their late teens...

 

What ever you do DON'T use automotive antifreeze in your system. First off if it gets into the domestic side it can kill you. Second any kind of that type of additive in the system will reduce your pump efficiency by moving less volume and raising power draw to run the pump. Are you sure that pump can handle the head / height it needs to pump?

 

Why would he ever need antifreeze, -1 c will not freeze if the pumps and pipes are covered as they should be if your trying to store heat . He wants simple ,, my DHW was confvcke with coolants and pressure and auto venting valves since my system ran at 2 bar coolant to move the collected heat down 40 feet to DHW tank House pressure is 4 bar .
Since he is using a 240Vac 50hz power , he can get a ac pump to pump the hot water line and keep the tank at rest pressure. if your off grid , and want a hot shower , you will run the water till warm and save all that cold water to go back into a tank or feed the garden . noting go,s to waste .
Sloth

 

I'd suggest that instead of getting glass for your top sheet, spend your extra $ on acrylic sheets. That should help with the baboons and hail.

Mount them 3/8 to 1/2" above the glass and you should be protected from any hail. If you really want to get sophisticated, add a valve in between the two, use a vacuum pump from an auto air conditioner maintenance kit to pull a vaccum between the two for added insulation. You'll have to caulk the edges of glass and acrylic, of course.

Two ways to add heat, either paint the backing black, or paint the tubes themselves.

Your other option might be to put this set up on the ground so you have good access to maintenance.

I assume you know what you're doing with 150F water, but most homes are recommended to be 120F max.

 

Thanks for the input. In this part of the world there are no maximums for domestic water temperature. 150F is a maximum. I will very likely end up turning it down when installed. Thank you...Dave

 

I lost my place when I read "baboons on the roof", Our elk problems are pretty minor.

 

If you have a lime problem, your copper pipes will start losing efficiency from Day One. Just something to keep in mind.

Likewise, sometimes a little simplicity trumps a lot of efficiency--especially when going for the maximum efficiency turns into a PITA.

I wouldn't make the solar panels pivot to track the sun. That's a lot of additional labor and expense, and a plague of maintenance to have to deal with forever.

You can probably calculate the "increase in efficiency" you'd get with tracking panels.

If it's 5%, get the same "increased efficiency" by making the collector 5% larger in area. Over the next thirty years you'll be glad you did.

I would rethink the entire copper pipe scenario completely. Every soldered joint is a potential leak waiting for you to go on vacation.

Plus, you don't need them to collect solar energy. A solar box and a bulk tank can do the same job. (See below.)

Pumps? If you design correctly you don't need no es-tinkin' pumps.

Build a system that will thermo-siphon. No moving parts, low maintenance, and nothing to break or wear out.

Here's a description of my system. It has taken at least $100.00 a month off my electric bill from the day I installed it.

The whole thing only cost about $100.00 in materials (plus some scrounging) and only took two days to assemble from start to finish.

I started with an old galvanized water tank. The kind that were used on water wells until the bladder-tanks largely displaced them.

It was a scrounge. Cost: $0.00.

I built a triangular hot box out of recycled plywood and 2x4s. I faced it with one layer of free glass (Yay, Craigslist!) and insulated it with scrap fiberglass (Ditto, Craigslist!)

I set the box on my back deck opposite the electric hot water heater on a south-facing wall, with the pump tank lying horizontal.

Being only one wall-thickness away kept the waterlines really short and minimized heat loss in transfer.

I plumbed the tank directly into the cold water intake on the water heater. Thus, heated water from the tank flowed into the base of the water heater, while the coldest water in the heater thermo-siphoned into the water tank--if it was colder than the hot water in the tank.

And as water was used from the hot water heater, it was constantly replaced with the hottest water in the tank.

My system is a very effective pre-heater for the electric water heater, and every erg of energy it delivered was one the electric water heater didn't need to suck out of the grid--and one I didn't have to pay for.

Most of the cost in my system was the brass valves and copper tubing used to plumb it in, plus a little paint and caulking.

I can isolate the tank from the system, if I wish, to allow for future modifications and/or maintenance.

I have NO IDEA how efficient it is or isn't, and the actual efficiency doesn't matter in the slightest. It works well enough to suit me, and that's all I need to know.

I think it was Kungfucious that once said "Consider always the difference between efficiency and effectiveness, Little Grasshopper!"


P.S.: If you have a Prancing Baboon problem, you can fix it quickly, cheaply, and permanently by just gluing a whole bunch of Stainless Steel thumbtacks point upward all over the solar panels.

The shade they cast will be insignificant, and the baboons will learn very quickly that it is far better to walk around than over...