I wonder if anyone has advice about the best pumps to use for solar DHW? I like the solar-powered pumps, but the ones I've seen don't pump until the insolation is about 200W/m2, which is actually about the same as a bright winter's day, and so presumably of little use under what would otherwise yield some warm water.
Any practical advice warmly welcomed...
J.
echase
16 Jun 2009, 12:11 AM
I published a design for a solar controller that may help you. It is published in the June and July 09 editions of Electronics and Practical Electronics available in good newsagents now. See http://www.epemag3.com/ which tells you more and has a picture of my system (at least it does now, the link will move on to a new edition by about August).
It’s a controller that will work with almost any sort of solar thermal systems but is optimised to work with no mains pumping using a PV electrical supply and direct systems. Great for saving that wasted electricity that negates a significant amount of the benefit of solar systems.
If you oversize the PV panel your pump will pump in these low light conditions, but my controller will prevent it over pumping in bright conditions.
Logmaker (Guest)
26 Jun 2009, 7:00 PM
One approach is to have the PV panel store power in a battery and a temperature switch controlling the pump across the battery, this turns on the solar pump only when the solar array is up to a specific temp and when not is storing power for when needed.
The battery can deliver the power for a heavier pump.
Our tests show this works.
ingleside
30 Sep 2009, 7:37 PM
Our Solartwin system simply measures the temperature at the top of the panel (A) and the bottom of the tank (B), and only pumps when A is greater than B. So the water is allowed to remain in the panel until it gets hot eough to be useful. That's the outline - let me know if you want more detail. Tony
