We often get questions about the Hut’s off grid system so here are our answers!
Our experience with solar power systems started with our retro caravan that we set up with a 12 Volt fridge, a solar panel, solar charger and 12V battery. In addition, we had an auxiliary connection that allowed the caravan battery to charge off of our vehicle battery when we were travelling.
The lessons we learnt in that project were that we needed to size our batteries better, as they need to run fairly full. Constant discharge and recharge of a deep cell battery quickly destroys them. When we did our hut system, we spent a bit more and got bigger batteries.
Couple of electrical basics that you need to understand:
Volts, Voltage is the difference between the positive and negative terminals. Think of this as ‘grunt’. Voltage is grunt. 12V are the most common and easy to set up solar systems for motor homes (which is the market for everything we used in our systems).
Amps, Current is the amount of power travelling through the wires. Big current means big cables. Ie to start a car you need big cables (jumper leads) because there is high current. Small wires for small currents.
Current(Amps) x Voltage(Volts) = Power (Watts)
The hut system includes:
- 2x Solar Panels, 290w
- A solar charger that takes that power and puts it into the batteries as efficiently as possible, tailored to the type of batteries. Ours are deep cycle AGM types.
- 2x batteries which have a capacity of 270Ah.
We also have a 3000W inverter. This take the 12Volt DC power stored in the batteries and turns it into 240V AC which is normal house mains power. This is more than required for most peoples purposes but we wanted something that could run high output power tools when required. The inverter is turned on if mains power is needed, then turned off when not in use. The inverter is connected to an RCD which goes to 2x powerpoints to provide normal use and protection that is expected in a normal house.
In addition to the above, we added a wind turbine and its controller to the system. This connects to the same batteries but runs independently to the solar charger. This helps get us through periods of grey sky where we get minimal sunshine hours for the solar panels, winter days and periods of rain for multiple days. The wind turbine is regulated by the charger that it came with by way of monitoring the battery voltage. When the voltage gets to 13.4 V (approx. full charge for a 12V Battery) then it shuts the turbine down. The solar charger does the same thing with the panels, ie it doesn’t overcharge the batteries.
For sizing your system, we recommend using a solar power website calculator, which will…
- Calculate the Watts per day that you need to run what you want to run
- Find out how much sunlight you are likely to have available at the location of the building, and how long you will likely need to store it.
- Work out what panels you need to harness the required amount of energy
- Work out how long you need to store it which gives you the size (in Ah, Amp Hours) of the batteries that you need to store it.
Ultimately if you are setting up on off grid place to live you are likely to need a back up generator. Our hut system doesn’t need one because of the wind turbine. We generally pick up at least a 10 Knot breeze most of the time because our property is fairly exposed. And the turbine just tops the batteries up at approx 40W but it is almost constant which is what makes it work. The turbine and charger is an expensive purchase though at $2,300 plus the installation costs. You can get a reasonable generator for that money.
In terms of Generators, we recommend an inverter type generator because they are generally quieter due to the housing having a lot of sound deadening built into them and they provide much cleaner power which is better for any sensitive electronics.
For charging a 12V system from a generator, you will need a special charger to ensure that as much of the generators output power as possible gets put into the batteries as efficiently as possible, ie. as quickly as the chosen type of batteries can accept it. It needs to be able to charge at 15 Amps at least. If you use a small battery charger (trickle charger) then you will burn a lot of petrol to charge your batteries because the generator will have to run for a longer time to get the same amount of charge (at a lower Current) into the batteries.
With batteries, inverters, solar panels etc. bigger is always better. The more $ you spend, the better your system will work without you having to constantly monitor it and without you discharging your batteries beyond their designed range of discharge. It is not worth skimping on the batteries because they will not last if they are being discharged too much and you will be up for replacements in no time. We did this with the caravan, no good.
With Fridges, 12V fridges actually make things cold, 3 way or gas type fridges don’t, well not very well in our experience. With the cost of gas going up so much, they are not economic. We strongly recommend you spend $ on a bigger solar/battery system that is sized to run a 12V fridge. They work well albeit they are noisier (they have a compressor like a normal mains fridge) and you don’t have to worry about constantly refilling gas bottles.
We are more than happy to run you through our system and how it works if you wish to come and visit.