Over the past 20 or more years I have been involved in many aspects of self sufficiency, but by far the most difficult to come to terms with has been replacing the humble refrigerator, with something simpler, home made and not tied to the 240v power grid. The two most obvious choices that spring to my mind are something based on 12v or something based on the evaporation of water.
12 volt powered
Some time ago I got a small 12v/240v fridge that is built to look like a small version of a full size fridge, it is powered by a Peltier effect device. It looks cute but uses about 2.5 to 3 amps to cool a volume of about 0.02 cubic metres, so it is handy but no replacement for the Kelvinator in the corner of the kitchen. I want to put together my own cooler based on this technology, but it is still on the list of projects to be completed (when I do finish it you will be the first to know!).
There are compressor based fridges that run on 12 volts on the market but they are expensive. I was aslo not sure how our system would cope with the drain, the batteries charge during the day but the fridge runs 24 hours per day. I know of people turning off the fridge over night to reduce the power drain, but when I mentioned this strategy to a refridgeration mechanic friend his hair just about stood on end!
My original idea was to get a Danfoss 12 volt compressor and absorber from Bias Boating Warehouse (Which was running at about $1000 at the time) and then build a super insulated chest fridge around it. My lovely wife was unsure how that would look and so expressed some concern (IE was dead against it!) so back to square one. Fortunately the above-mentioned fridge mechanic had his own buisness and was interested in 12 volt cooling so he said if I got a fridge and paid for a Danfoss 12 volt compressor he would put them together for nothing - Woo Hoo - sounded good to me!
So we went out and bought a "Homemaker" brand el cheapo 317 litre fridge from Kmart for $350 or so and stuck it in the back of the station wagon we had at the time. It is a very basic fridge and somewhat smaller than the main fridge we were using at the time, but with the kids moving out, and this being and experiment I thought it would suffice. My friend got the compressor and I reimbursed him the $600 or so, gave him the fridge and away he went. Two weeks later and I had a 12 volt fridge!
My thought had been to use the second battery bank to power the fridge by getting a black box to split the power coming from the solar panels between the two banks and then connect in a wind generator to the second bank to provide winter power, when the hours of daylight are low. I bought a Morningstar Sunsaver Duo 12 volt regulator for around $350 (so not cheap) and it lasted about 3 months, after much to-ing and fro-ing by the supplier they finally replaced it after initial apathy. The second one lasted 6 months - bottom line I would not buy Morningstar stuff again. The one good thing that did come out of it was the little remote gauge that tells me the voltage in each of the battery banks. I still use it and have found it to be invaluable, it is digital and the analogue one that I was using before I found to be wildly inaccurate, which I suspect cost me one set of batteries.
In any case, it became clear that the current system would not support the fridge in longer cloudy periods or around the winter solstice so I bought the bullet and bought two $1000 7.5 amp solar panels and now have two totally separate systems. The system has now been operating for over 12 months successfully, but I still keep the Powertech (from JayCar) 12 volt 12 amp DC power supply (ie it converts 240 VAC to 12 VDC) to run the fridge off the mains power in the event that the 12 volt system has troubles.
Lessons learned -
If you are going to make your own fridge automatic defrost is good!
The poor insulation level of the el cheapo fridge means it uses more power than it should.
This experience REALLY focusses you on the amount of power refridgeration uses
An accurate digital volt meter is crucial to have in the system for battery health
A remote monitor that allows you to check battery health from inside your house is WONDERFUL and can alert you to problems before they become critical
Deceptively normal looking, but 12 volt powered!
