my solar project-need pump ideas

[barnartist]

I have had this built for a few years now. I first used it to help heat my pool, but now I'd like to pump the water into my existing 500 gal storage tanks. Im looking for ideas on a dc run pump so that I can hook it up to a matched solar panel. My thinking is that when the solar panel has power to feed the pump, the water in the pipes also must have some heat.

There will be virtually no head on the pump since my storage tanks stand virtical. All of the rest of the plumbing is in place because I use the tanks along with my gasifier wood stove to heat my home. I simply need to connect the solar system, and then I can use it for our showers and such.

Pump, panel, thoughts-where to buy. Thanks!

 

[barnartist]

another pic of all.

 

[Bad Wolf]

Try http://store.altestore.com/Solar-Water-Heaters/Solar-Circulator-Pumps/Dc-Pumps/c425/

Or you could use a regular TACO pump and a differential controler. When the collector temp is 8-10 degrees higher than the tank temp the relay turns the pump on. Thats what I'm doing with mine.

 

[Bad Wolf]

The cost of enough solar panels to power the pump and a 12 volt pump will be pricey. The nice thing about the controler is it gives me readouts of my tank temp top and bottom as well as controling the pump for the solar panels.

 

[Dune]

Check with R.V. places for d.c. pumps

 

[barnartist]

your right, the dc pumps are pricey. I have a taco 13 here unused but it will circulate the water to quickly and use more power than I want it to.
OK, where do I look for the differential control? How much do they run?
I think a taco 007 will probably do the job.

 

[peakbagger]

The typical DC circulator pump used on solar hot water systems, draw about 20 watts. They are usually in a sealed loop so there is no elevation head so they only have to account for the friction in the piping and in the panels. The pumps are sized for flow rather than pressure drop so make sure you look at the pump curve before you buy one.

 

[WES999]

Take a look here: (broken link removed to http://www.discountpv.com/solarwaterheating/index.htm)

It looks like they have kits with the pump and solar panel starting at $235.

It would probably cost about the same for a AC pump and differential controller.

 

[Wet1]

Search no further...

http://www.newegg.com/Product/Produ...A=0&Order=BESTMATCH&Description=swiftech+pump

The only real problem I see with running a pump on a properly sized panel is having enough power on tap to start the pump and the low voltage situation under during transitional periods might be very tough on the pump. If you want to use solar electricity to power the pump, I'd use a differential controller with the pump and a solar panel tied to a battery to condition the power and supply the needed power for the initial surge.

 

[barnartist]

I like the solar idea, but it is not something I am stuck on. If everyone thinks it will be too tough on a pump then I'll just run it with AC.

 

[peakbagger]

Hooking a DC pump directly to a solar panel is not tough on a typical centrifugal DC pump. Bascially when there is low light, the pump doesnt turn very fast and therefore doesnt deliver any significant flow. Mine works fine and I have seen and heard of other installations where the pumps have been running for several years. At some point brushes need to be changed, but that is more of a function of hours or operation versus voltage and load. Generally the linear current boosters are used on positive displacement pumps used on water wells but that would be overkill for your system.

 

[barnartist]

Ya, I would think that under low light the flow would barely move, but that would be perfect-less heat to move into the tanks. I think if this stuff were available over the counter at a hardware store I would have bought something by now to try out. At this point in the year though here in Ohio, the sun has been only a friend that stops by every now and then. I don't think I have missed too many BTU's for free.

 

[woodgeek]

For the effort you are making, I think you should upgrade your collector. I'm completely cool with the DIY collector concept, but it seems you have taken inspiration from concentrating troughs rather than big flat plates. Of course, the concentration factor does nothing to increase the BTU's collected (and you don't want to boil the water anyway-just heat it). In fact, the concentration can lead to lower eff both from the reflection off the trough, and in passive losses off your hose. The only reason the big boys do it this way is that they need to make steam to turn a turbine, so they eat the losses (after engineering the crp out of the reflector and the evacuated tube in the focus).

BTW, the unglazed pool heaters work well for their job because the water temp is usually lower than the air temp, so passive losses are negligible or negative. So I do believe your system heats water in your pool. Heating water in the winter is another story, I think you need at least one sheet of glazing (could be a plastic film) to get 30-40% eff in the cold weather.

I think you would do a lot better to put up a cheap insulating board over the whole vertical wall, paint it black (use 'selective' paint for a couple bucks more if you want to be fancy), reconfigure the hosing you have to cover the area with the smallest spacing possible (6-12"), and then find some cheap plastic sheet that is rated for 200F and staple it over. I'd guess you'd get several times the BTUs in the summer (from the increase in area), and at least some positive BTUs in the winter.

I hope this all came out as a constructive comment! It was intended as one.

 

[barnartist]

I'm just trying to understand your thought/idea. I don't really have anything vertical so I am a bit confused. Maybe you mean the piping at the end of each trough. If so your right. But my plan is probably to only run this solar system during the warm months because I dont want to have to run glycol and then a heat exchanger so as to use the system year around. I don't think we get enough sunny days to benifit from such a system during the winter, although I could be wrong. I do have radiant plumbing in the house, so maybe I could get enough heat on some days to run that. I just don't know. Thanks! please continue your thoughts.

 

[Gooserider]

The Build it Solar website has a lot of good info on it, including plans for DIY collectors. They've done a lot of research on how to get the most BTU's per buck in a collector, seems like they have some really good designs.

Gooserider

 

[woodgeek]

Goose's link covers it all. By vertical I just meant the wall you hung your collectors on. You could get a lot more heat by having a larger area and at least a film for glazing. Is glycol incompatible with your piping formulation? Don't have a liquid to liquid heat exchanger? Running potable water through system now?

For the pool--those solar pool heaters are very cheap, and tho only complaint I've heard is that you need to patch them sometimes. For space heating in winter--I think solar air heaters are a great DIY project.