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Low voltage DC solar heating pump from europe?

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PekkaNF:
I am thinking of building a small off-grid solar heating system for warm water. Solar heating will not provide 100% all year, but should do about 6 months without any external energy. Middle of winter would need 100% of external energy. Space heating is different system altogether, but there low voltage heat circulation pump would be really useful too.

Therefore:

1: Circulation pump for solar panel circuit.

2: Circulation pump for space heating system.

Ideally these pumps would be then same model, if dimensioning and chemical resistance etc. works out. I am looking for a decent quality residental type pump, not all plastic caravan type pump.

There seems to be plenty of solar heating and PV panes, controllers and other hardware, which most of it normal domestic heating.

It is easy to locate 230 VAC mains operated circulation pumps, but low voltage (12/24/48VDC) circulation pumps seem to be rare.

Saw this one on YT:


This is not exactly, what I need, but othervise looks pretty good:
https://shop.solardirect.com/product_info.php?products_id=880

There is possibility to use DC/AC sinewave inverter, but this is of additional complexity and losses.

Ideas or good pointers?

ZebraDriver:
A quick look at ebay shows lots of solar hot water brushless 12 volt pumps, Ok they look to be plastic but at the price of them (under 20 euros) they might  do your job and be replaceable as they possibly wear out.

Martin

vtsteam:
So Pekka, the reason for low voltage is that you also want to power the pumps from a photovoltaic source?

PekkaNF:

--- Quote from: vtsteam on July 17, 2022, 03:18:35 PM ---So Pekka, the reason for low voltage is that you also want to power the pumps from a photovoltaic source?

--- End quote ---

Correct. Sort of UPS for power breaks and other exeptional (and hopefully rare situations). Small DC PV system is simple to work with.

I do have 3 phase mains, but there are ocassional power breaks and world is a bit grazy....therefore I am looking for a little redundancy, back-up and maybe a little energy bill savings.

My logic goes for a separate discrete systems that are easily replaced or upgraded. Solar thermal system needs very little external electricity to work. However, most controllers and pumps are build for mains use. No problem, if the solar energy is used only when main energy is available....but I want it also when it is not. I do know that energy demand is low and I could use an inverter, but that is added loss, reliability and complexity. Ofcourse this is no problem in a bigger PV system, but that would need to have all island use hardware.

I was looking a little thermosolar system, because it is proven and simple. Also storing enough energy for 2-4 days use for hot water in a insulated "boiler" inside of the house is standard technology and very reliable. There are pretty much all system components available, even packaged, but the low voltage pump part could be a show stopper.

My other alternative for thermosolar panels and pumps would be to use PV panels to produce high DC (equivalent of AC) to heat water in a standard boiler. Here it would be 8 x 375W panes (each nominally 40v open circuit voltage and 12A short circuit current) in series, mounting hardware, isolation switch, wiring and overheating disconnect....and very little anything more. Feels a little daft to use PV electricity to waste it into a restor (heating coil/immersion heater ) to heat water, but it looks like most cost effective way (no inverters, just a relay to disconnect it in a unlikely event of thank overheating). But Solar panels would take more space and in future I could use that space for PV panes that produce usable electricity...

That is my though process and now I am stuck of not finding a low voltage solar heater circulation pump and that might lead to scope creep....and that probably would render simple system unfeasible. Just doing a little feasibility study study before comitting.

JamesC:
A thought, do you need a pump at all?

With the right design you could have a gravity system which required no pump.

James

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