The sun is your charger
Updated: Mar 5
When building an off-grid home, solar panels are one of the first things that come to mind. I have also considered aeolian power (wind energy), but the winds here are not strong enough or the technology is not yet too efficient. Keeping on the solar panel track, I discovered that there are loads of options on how to design your system. However, blueprints are scarce, especially when concerning a small off-grid system. For this reason, I’m sharing mine with you now.
There are some things that I would like you to consider before going to the blueprint.
First, my solar panels stand on the ground, a bit less than 30 meters away from the house. The roof of my house is not very suitable to mount solar panels, due to its steepness and direction. The distance between the solar panels and the house was my main motivation for connecting the panels in series. A series connection allows for using thinner cables, while keeping the voltage drop within a decent percentage.
Second, I live very simply and prefer to have an efficient system that I would be able to understand well, instead of a system that would allow me to have all the modern comforts. I did not use an integrated inverter/controller to 220V. The latter is costlier, fails more easily without good chances of a DIY fix, and uses more power for ventilation and conversion than a charge controller. I chose my house to be powered solely by 24V, by means of a charge controller. The energy supplies inside the house are USB and 12V ports (like the cigarette lighters in your car). I did include a small 1000W pure wave inverter to 220V for the fridge and occasional domestic appliances.
small water pump (check out my post on rainwater harvesting or more information)
batteries for wireless tools
Illustration of the photovoltaic system
Three solar panels of 450W / 41.8V / 10.77A connected in series summing to a total of 125.4V/ 10.77A/ 1350W.
MPPT Charge controller 60A / 12V-48V / Max OC 138V / RCP 1500W for 24V.
Two 12V batteries of 150 Ah connected in series summing to a total of 300 Ah / 24V.
Fuse of 80A protecting the batteries.
Fuse panel with fuses adjusted to the respective domestic circuit.
If you would like to see the system up and running, have a look at documentary (10:20 onwards).
I’ve been using my system one year now and it passed the test throughout all the seasons. The batteries have never been more than halve empty. They even charge well when there is a significant cloud cover!
Thank you for reading my post. If you have any comments, please leave them in the box below.
Sources and calculations:
· The thicknesses of the wires were calculated using jCalc.net (Electrical design calculators).
· The direction of solar panels was determined by means of HOMER (Hybrid Optimization of
Multiple Energy Resources). The application calculates whether you have to adapt your planned PV system, based on the days when the sun is scarce. You can specify the capacity of your panels and batteries and fill in the coordinates of your location.