SPCC A Casa Amarela

part of our initial sustainability plan was to have a photo-voltaic system to supply the electricity for the house. so yesterday we finally set it up! here's how we did it for under 80€.

we started with:
1) an old used solar panel, working, about 60W max, 12/24V;
2) an old used 45Ah car battery;
3) some spare power cable (heavy duty 6mm² copper)

we bought:
4) a 15A solar charge controller with load control (under 40€);
5) a 150W (300W peak) car inverter (~25€);
6) extra cable (~10€)

the setup is easy. the main part is the controller, which has 3 terminals: solar panel, battery bank and load. so:
1) connect the solar panel to the controller
2) connect the battery to the controller
3) connect the inverter to the controller
4) connect your house wiring to the inverter
if everything goes right, you now have working electricity!

don't switch the + and the - in the wiring! if you have to cut the cigarette lighter car connector like we did, the wire that connects to the tip is the positive (+) and the wire that connects to the side metal strips is the (-). we found this by disassembling one that had colored wiring and we got lucky, red really was + that time.

some caveats:
on a 60W panel, you probably will get a daily average (for sunny portugal) of about 10h at 40W. total energy is therefore 400Wh/day. a 45Ah 12V battery can store 45*12 = 490Wh of energy. this means that this battery charges in about one day. with our tests, it actually took about 2 days from no charge to full charge, so we're a bit below the prediction.
on what it can feed, since our inverter can only output 150W, and since the charge controller won't let the battery drop more than 20%, we have a total of about 100Wh to spend with no sun, with 150W load. that means that each night we can get about 40mins at full power. luckily, our loads are mostly eco bulbs (11W) cell phones (about 6W) and netbooks (about 40W). so if we charge during the day (when we have the extra from the sun) and use only bulbs during the night, we'll get about 8 hours of light during the night. which is fine for our current purposes.

to increase total power output, we're working on:
1) adding more batteries and solar panels (deep cycle batteries preferably) which will grant us more stored energy for when there's no sun;
2) setting up extra inverters, including 1kW inverters (this one is really cheap as long as you fuse it) which allows for power tools and refrigeration (BEER!);
3) adding wind power to this setup using the old motors we have.

we're also available for training in this, if anyone wants to learn how to set one of these systems up, let us know at [email protected]!