FREE TO A GOOD (NZ ?) SOLAR HOME
Reading @Joey Hess' recent post on solar PV for hot water, I was reminded that I have the above items, gathered when I was looking at a project for myself, but unused as I finally opted for an evacuated tube system:
Dual immersion heater element with standard thread/fitting for NZ hot water cylinders. This has two elements, the first marked 240V 2000W, the second marked 96V 1000W. The idea is that this replaces the standard 240V 3kW immersion heater, allowing normal mains operation with the first element, with the option of some sort of solar PV to the second element.
Combined thermostat and overtemp safety cutout. Most standard HW elements have the thermostat/safety built in. The above dual element does not, so this would do the job for the mains element. Note that it would probably not do the job for the solar element, which would be DC and so prone to arcing.
MPPT tracking controller for battery-less DC solar PV water heating. I got this from Techluck in the US, he hasYouTube demos:
It looks as though it works, though I have never tried it. As I recall, the solar array and probably the immersion element need to be reasonably matched to operating range of the PCB.
He doesn't post any operating/ connection details until you have purchased the unit.
I'd prefer to pass this to someone who has some basic understanding of electronics.
I would have to go back and see if I can find the operation/connection details.