/diy/ - Do It Yourself

>>2797376
1100L of water = 5550 mol of water
heat capacity of water = 75.385 J/(mol•K)
heat capacity of 100L water = 418.450 kJ/K
If you want to get that water from 20°C to 80°C, that's 60K difference
heat required = 25.107MJ = 7kWh

So 4•250W of constant power will get the water from 20-80C in 7 hours. But you could only get that much continuous power by having your PV panels on gimbals, which you probably don't want to do. If you angle them towards the equator you'll get maybe half of that.
It also assumes maximum power point tracking, which you won't get just by piping the panels into a resistive heater. Pic related is the output of a PV panel, if you pick the wrong size resistance you'll get way less than 250W per panel if it's directly connected. You'll probably want some form of MPPT controller, though I'm not sure if conventional MPPT charge controllers will pipe energy into a resistive load with no battery. It's probably a problem that's been tackled before, with any luck you can just choose the right size resistance and a normal MPPT controller will think everything is fine, maybe using some funny configs and/or a little voltage divider. I advise using a length of nichrome that you can adjust the length of via crocodile clips.

Consider running the water behind the panels before it gets heated resistively, it will both cool the panels (cooler panels are more efficient) and use the waste heat for heating the water further. There are also some really easy diy solar water heating panels out there, Tech Ingredients did a good one.