Off-Grid in Cornwall

The Hobbit and I have just returned from a pleasant weekend down in Lostwithiel. For the last few weeks I've been playing email ping-pong with another member of the Forum, gucu, who has built himself a recycled shed down at the bottom of his garden and wanted to put in an off-grid solar system to power garden lights and his aquaponics pump.

He procured the inverter, solar charge controller and batteries and I advised him on minor details like the battery interconnects and how to set up the system. I'd hoped to drop down to Cornwall one week while I was working in Portishead but due to work schedules and his training commitments a suitable window of opportunity had been evasive,

So, we jumped in Pudgy, dived over the bridge and down the M5 and A30 and went to visit gucu, his lovely wife annapuddles and the kids.

Saturday was a day of manly shed-time while the girls went for a mooch round Lostwithiel.

Photos shamelessly stolen from gucu's blog - I'm sure he won't mind!

Four 12v 15Wp thin-film panels installed on the sloping roof, South South West orientation.

Two Alphaline 88Ah deep-cycle leisure batteries wired as a parallel bank and powering a 300W Sterling Pure Sine Wave inverter. To test the inverter we used an anglepoise lamp with a 25W incandescent bulb. You can see the LED display on the inverter showing the load in watts.

Having got the mains output working, I used the inverter to power my soldering iron which I then used to wire up the panel connections and create the input side of the system. The panels feed a Steca Solsum 10.10 charge controller which is then connected to the batteries using 6mm heavy duty cable. Although the total capability of the controller is only 10A and the cable is capable of handling 37A, by using far thicker cable than the current rating suggests, this reduces resistive losses to a very low figure thus getting maximum charging voltage into the batteries.

See that smile on my face? I'm always happy when I'm fettling!

So, all done and dusted, and the inverter and controller mounted in their final positions. I'd pulled 35W for about half an hour with the soldering iron, and with the light for testing, I estimated we'd used some 20-25Wh of the available battery capacity. It was a fairly overcast day, with a few spots of rain, but by the time we'd had a cup of coffee and a pasty for lunch, the charge controller status display was showing charge coming from the panels and the battery monitor was flicking between orange (charging) and green (charged). Ten minutes later, the batteries were showing full again. That is the biggest advantage of using thin film panels...their performance and output in poor conditions is much better than poly or mono panels. Ok, in perfect conditions you can expect a higher output from the more expensive panels, but for the next six months, the UK winter insolation is going to be far from perfect.

Smiles all round, and a good job jobbed.