Today I came across a post on the IEEE (Institute of Electrical and Electronics Engineers) Spectrum site called "Living on 150 Watts". A couple in Fiji lives off the grid using a 300 watt micro-hydro turbine generator. There is not much drop (low-head) from the water intake to the turbine, so it only produces half the power it is rated for. The longer the drop, the more potential energy available, that is why hydro-electric dams are so tall (high-head). with only 150 watts you have to make a lot of sacrifices on what appliances they can use when. They plan on adding a methane powered generator to run off the methane produced by the rotting manure from their cows.
Hydro-Power
Here is a really nice example of a high head system. It is more complex than what you would use for a single household, but good for a small village or if you wan to go into it with your neighbors, it runs at about 8 Kilowatts.
A hydro system is nice if you have a stream running through your property, which not everyone has. Next up, power from poop.
Methane Power
Power production from methane is a fairly new energy production method. Dairy farms are really picking up on this technology, since you need a lot of manure to make enough bio-gas to run a farm, and if you have been to a dairy farm you know they have a lot. Methane production and power generation takes a considerable investment. You need anaerobic digesters, scrubbers to remove hydrogen sulphide and other impurities, these can cause increased wear on generators and engines that will be running off the bio-gas. Also needed is a generator or engine designed or modified to run off methane, or natural gas. The Caterpillar company already makes generator designed to run off "dirty" gas from unscrubbed methane. Here is a dairy farm that runs off it's own poo;
Wind Power
Wind power is one of those solutions that seems like a good idea, but is actually a pain in the rear. So many people think that there is some super efficient design out there somewhere that can power an entire house. Not true. Wind power is very finicky, you need an average yearly wind speed of at least 12 mph to get any viable energy. In Midwest states like Wyoming, North Dakota, and South Dakota, this is definitely possible.
Wind is a very finicky thing even in high wind areas. Too high wind speeds will break the wind turbine if it doesn't furl the blades (rotates the blades so they don't spin faster in the wind). This requires a more costly and complicated (read: breaks easily) mechanics. Plus you have to have a mast taller than anything surrounding it, like trees and houses. The best place to have one would be on a hill near Minot, ND. It always blows there ;)
Video of a catastrophic failure on a large turbine;
Solar Power
Ahh, solar. Not as over-hyped as wind power, but pretty close. Solar power has come a long way in recent years, especially in price. Solar is slightly less unreliable than wind unless you live in a desert area like Phoenix. Cloudy days drop the amount of energy available, and you get nothing at night from it. To get enough power to run anything decent in say Seattle, you need a significantly larger solar panel array than you would in Phoenix.
Back-up Systems and Miscellaneous Equipment.
All of these systems WILL require back-ups. failures either to the system, or source of the energy will occur (drought, cloudy days, no wind, generator malfunctions...). You need a back-up power source, like a battery storage bank or a gas/propane/diesel generator. A battery storage is always necessary for solar and wind systems, since it is unreliable. You need a way to store that energy you receive when you are not home and want it when you get back from work (usually in the evening when solar starts to conk out). Battery banks require a charging system to convert power from the source to a safe voltage and current to charge the batteries. If you are using "The Grid" (power company) as a backup, you must install a safety device that will cut your system from the grid in case of a power outage. This keeps the linemen safe from being electrocuted while trying to fix a line they thought had no power.
Unless you have everything in your house to run at 12V/24V/48V, you need an inverter. Inverters change the voltage from, say 12VDC batteries, to 120VAC that every home appliances runs on. Inverters can be cheap ones designed to run your laptop charger from the cigarette lighter in your car, to large expensive ones designed to run an entire household load.
Conclusion
Even with a large system producing lots of power, you may still find that you need to ration your power. With the kind of alternative energy system most people can afford, that will be a certainty. So, if you want to live off the grid, you must be ready to make a large initial investment and willing to make sacrifices in how much power you use, which is something you should do anyway, if not for energy conservation, at least your pocketbook.
