Off Grid Solar Power – DC Water Pump.

Off Grid Solar Power – DC Water Pump.

Well, things are finally starting to take shape at the shack as far as getting off the electricity grid. I’ve designed a simple solar power system to provide power to pump water from one of the rainwater tanks to the house.

My current set up is a Grundfoss pressure pump running on 240V AC (240V is standard in Australia). I started doing the sums and figured out that a system to run the pump would be far too expensive. The pump is also capable of supplying far more water than I ever need to use at once. The Grundfoss pump draws 700W @ 240V AC on startup, which means that I would need an invertor big enough to handle that start up current, as well as circuit breakers and cable to handle that current draw at 12 volts (pretty close to 60 amps).

My new propane water heater uses up to 16 litres of water per minute, so I’ve sourced a 12V pressure pump that is rated to pump 17 litres per minute with a 40PSI cutoff. It also draws only 9.2 amps @ 12V DC. Now that makes the power requirements a lot easier.

I generally don’t have the water running for more than half an hour a day, so there’s 5AH @ 12V DC that I need. So I got a 100W monocrystalline PV panel on eBay, a 20A MPPT (Maximum Power Point Tracking) charge controller, a 20A circuit breaker, some battery terminals, some wire and some jumper lead cable that I had laying around.

I paid $5 each for the batteries at the local tip shop and after sitting in my carport for six months, they were still holding 12.5V.

In the next couple of weeks, I’ll get the pump hooked up to the house and do a test run with the new pump and propane water heater.

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Music: Born Barnstormers by Brian Boyko. The full track is available at freepd.com. This music is in the public domain and is free to use.