Basics of an Off Grid Micro
by Staff Writer
Only a small percentage of parcels are suitable for a
micro hydro installation. But if you have an adequate change of elevation and
sufficient water flow, micro hydro may be the most efficient and cost effective
way to power your homestead.
Capturing the energy of moving water is not a new
idea; it has been used to mill grain, operate bellows, and manufacture textiles
for hundreds of years. It was only recently, however, that we learned to convert
the potential energy of moving water into electricity. The construction of dams
and modern hydroelectric plants really began in the 1930s. The Grand Coulee Dam
in Washington, which was completed in 1942, is capable of producing over 6,800 megawatts of electricity and
is still one of the largest producers of electricity in the world. One of the
great things about hydroelectric is that it can be generated on any scale, but
scalability is only one of the benefits of hydroelectricity.
Micro Hydro Turgo Turbine
- photo courtesy of Gary St. Onge
Smaller installations do not require that a reservoir
be built, so there is very little impact to the ecosystem. Power generation
tends to be more consistent with micro hydro installations than with solar
arrays or wind turbines -- it's hard to guess how much the sun will shine or the
wind will blow. Traditionally, micro hydro generation is more efficient than
other forms of alternative energy. It's not uncommon to capture 60% -- or more
-- of the potential energy stored in moving water. Some people frown on wind
energy because they don't care for the whirling noise that turbines may
generate, or they don't want an unsightly tower and guy-wires on their property.
Micro hydro installations are quiet and low-key. Most people won't know that you
are generating electricity unless you point out the components of the system.
For a successful micro hydro installation, you need to
know the head and water flow of your site. Head is the pressure created by the
difference in elevation of the water intake and the turbine. The greater the
difference is, the higher the pressure generated will be. Water flow is the
amount of movement expressed as gallons per minute. Measuring the head and flow
are critical steps when planning your micro hydro installation. If your site has
high head but low flow, an impulse turbine would be most efficient. If your site
has low head but great flow, then a reaction turbine would be a better choice.
Determining the cost and components necessary for a successful installation are
impossible until you have accurate head and flow measurements.
Micro Hydro Water Intake
- photo courtesy Joe Hartvigsen
The materials, appearance, and cost of micro hydro
installations can vary greatly, but they should all share the same basic
components: intake, pipeline, turbine, and generator. Water is filtered and
funneled into the system through the intake. The water builds pressure as it
travels through the pipeline (or penstock) to the turbine. The potential energy
in the water is then converted into kinetic energy in the turbine. An alternator
or generator uses the kinetic energy to produce electricity. The electricity can
stored in batteries, used directly, or fed into the grid. Numerous
components can be used to condition and manage the electricity, but this is
beyond the scope of this article.
Micro hydro turbines can be a cost-effective way to generate electricity, but only if they are designed
and installed correctly. Selecting an improperly-sized turbine or pipeline can
severely reduce the efficiency and output of your system. Do-it-yourselfers can
still tackle their own installation, but should proceed with caution. Consider
working with a consultant or at the very least, talk with your turbine vendor.
Turbine vendors know their business and can provide a wealth of information if
you take the time to ask.
For more information about turbines and micro hydro installations, visit:
St. Onge Environmental Engineering, PLCC