Eddie's R.A.P.S (remote area power system)

Only one of the buildings (a rental house) at Nimbin Rocks is connected to mains electricity. We intend to keep the rest off the grid. We are also supply our own water and waste disposal with the exception of some rubbish which is taken off site. Anyhow my energy needs are a bit different to most RAPS systems you find written up in that my place at Nimbin is not my primary residence so there is little drain on the system for most of the time. This means I can get away with smaller solar panels (aka photo-voltaics or PV) in my PV/battery system. Currently I use 3 PV panels, one 40 watt solarex panel I bought new about 6 years ago for taking on island trips, one second hand panel of aprox 20 watts and one second hand 60 watt BP solar panel. This give a peak output of around 120 watts. However to get peak power you would have to run the panel at 18 volts or so, 100 watts is a more realistic figure. Say 8 amps @ 12.5 volts. The panels do not track the sun so most of the times I'd get well under the peak rating. My batteries consist of two reject train batteries. These are normally 8 volt batteries which are used in sets of three to give a 24 volts system. The ones I've got failed their pressure test in one cell each and the faulty cells bypassed giving two six volt batteries - now in series to give 12 volts . I'm not sure what the capacity of the batteries are. I'd guess they are in the order of 500 amp/hrs. At 500 a/h a 0.01C trickle charge (ie 500 * 0.01) is 5 amps, this is close to what I can expect from the PVs so there is no danger of over charging and no need for a regulator. The down side of this is that lead/acid batteries sometimes need to be boost charged, this is something I can't do using PV and I may end up using my car to boost it if the need arises. A higher voltage system would be more efficient but 12 volt was much cheaper and easier.

System loads.
Currently the only permament load is an electric fence which draws practically nothing. Other low voltage loads are 2-15 watts flouros, one 4 watt flouro, a mobile phone and a Ni-cad charger. A 12 volt water pump may be added shortly. For running 240 volt stuff I have a second hand square wave inverter rated at 350 watts continious, 600 watts for 20 minutes and 1.5 kilowatt surge. This can run power tools and the old 386sx notebook PC I'm writting this on. A sine wave invertor would have been nice but the only thing the square waves won't do is get variable speed from my variable speed drill. If I were to live here (Nimbin) permanently my RAPS would need to be upgraded as both the time I'd be using power and the amount drawn would increase. While I'm happy enough to go without my fast PC and TV etc for a week or so - when I know I can drive back "home" to them. I wouldn't want to give up the mod cons permanently and my PC can earn me money as a programmer , PCB designer or web author.

Hits since 29/oct/98 =

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