With the stables fit out finished it was time to finish off the solar power project for the shed. This is our first foray into solar power so we started small, modular and scalable. We really just wanted the ability to run lights and the occasional small appliance (like horse clippers) from the 3-bay shed. It’s about 40m from the house so it wasn’t worth the effort and disruption of digging cable from the house.
The panel on the roof of the shed is just 10w – enough to trickle charge a battery. I’d calculated our use to be fairly small, and with a reasonable capacity battery, there was no need to charge it any faster than 10w. That said, there is room on the roof stand to mount another panel in future if we need more power. The panel is incredibly effective and even produces power on an overcast, showery day.
The panel faces North and is set at an angle of 42 degrees. Interestingly, the optimal angle to maximise your solar absorption is the same as your latitude – in our case 42 degrees.
The battery and charge regulator are the smallest capacity I could find, but still with some room for expansion. The setup is pretty straightforward – energy comes from the panel into the regulator and then to the battery. The battery is wired to a switch to control the lights.
With such a small solar panel, a charge regulator isn’t strictly required as it would be almost impossible to overcharge the battery, but I never miss a chance to buy a box with blinky lights on it…and we can add more panels in future without worrying about cooking the battery. When the battery is full, the regulator stops charging it.
The battery is a bog standard car battery. You can spend a fortune on deep-cycle batteries, designed to discharge and recharge many times over, but as our battery will never be less than around 95% charged, a cheaper car battery is fine. It has a capacity of 32AH (or approximately 1 amp of current draw for 32 hours).
I’ve used standard TPS house wire for all the wiring and it seems to work fine (although it might be slightly less efficient). With 12V systems you want to use the thickest gauge wire you can, but we’re dealing with short distances (and I happened to have a roll of house cable lying around).
The lights are 12v LED spots with 48 white LEDs in each cluster. They draw 1w of power and put out a lot of light for their size. Three of these at the front of the stall allow more than enough illumination to change a bandage, feed the calves etc. Now that I’ve tested them, I’ll put another strip of three in the middle of each stall.
The inverter is a cheapie from Dick Smith. It is only 300w so it will run a 240V radio, clippers etc. We could replace it in the future with something more substantial if we needed to use power tools out there for example.
Finally, a nice chunky waterproof swith to control all that solar power.
Future plans for the shed include 12v sensor lights and possibly a small wireless repeater to extend the farm wi-fi network, but that’s definitely for another day…