Designing Ecological Habitats - Gaia Education

enewable energy anD electric systems Design for ecovillages 169
market to produce high quality machines at a reasonable price, so there are
not enough of these available. Europe is perhaps the best source. Africa and
Asia are starting to produce some good machines. The USA lags behind.
Micro Hydro
Small hydro can be the absolute best renewable energy source for an ecovillage.
And you may be surprised how little water it takes to produce significant
power. The advantages of hydro are many: For a modest investment you
get power 24 hours per day and in many cases 365 days per year. It can be a
great source of power even if your flow is seasonal, providing power during
rainy months when your solar harvest decreases. If you are looking for land
for a new ecovillage, it’s worth making a viable hydro resource part of your
land search criteria.
One kW of hydro can be produced from roughly 6.3 liters/second (100
gpm) falling 30 meters (100 feet). This would be considered ‘high-head’
hydro and would use a pelton wheel turbine. Or you can pass 10 times as
much water through a ‘low-head’ turbine with one-tenth the elevation
change and produce the same 1kW of power.
The economics of hydro can be fabulous. Let’s say you have that 1 kW
of hydro potential. One-thousand watts (1 kW) running 24 hours/day for a
full month = 720 kWh/month. Not bad for a system that could cost less than
U.S. $6,000 installed! A wind system producing an equal amount could cost
you 3-4 times that and an equivalent solar system could be 6-8 times that cost.
Geothermal
There are two kinds of geothermal energy. One is the latent heat in the earth
or water table that can be harvested with a heat pump. Heat pumps can be 2-4
times more efficient than using a direct electrical heating element but involve
more hardware and complexity, with associated maintenance costs. The other
kind of ‘geothermal’ refers to hot springs. If you are lucky enough to have a
sufficient source of this energy, you can power your whole ecovillage.
Waste Heat
With the advent of practical, affordable Stirling engines, waste heat now
becomes a source of renewable electricity for on- and off-grid living. A freepiston
Stirling engine can transform the waste heat of a woodstove, furnace,
exhaust stack – or even a fermentation process – into useable electricity.
Recently available units burn natural gas or propane and produce all the
heat, hot water, and electricity a community may need.
Backup Sources
Even the best renewable energy system design usually requires some backup,