Harness Hydroelectric Power for Off-Grid Energy

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Electricity generated from running water can be one of the most affordable off-grid power sources, but the use of hydroelectric turbines may be restricted in some areas.
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Hydroelectric Turbine and Head of Water
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Hydroelectric Water Wheel on River Surface
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"Hut-Topia" by Christopher James Marshall is a place-name meaning hut for small house and utopia for ideal. You can build your own ‘Hut-Topia’ as inspired and wonderful as the small house that Thomas Jefferson built which founded his famous Monticello homestead.

Hut-Topia: How to Create Sustainable Small Homes and Homesteads by Christopher James Marshall, 2015, is a holistic DIY guide designed to help you along the path to creating a sustainable homestead and affordable dwelling. It provides perspectives on the history of small houses, building and zoning codes, as well as on being a landowner, how rural living is different than urban, examples of off-grid dwellings, and much more.

You can purchase this book from the MOTHER EARTH NEWS store: Hut-Topia: How to Create Sustainable Small Homes and Homesteads.

On-Site Hydro-Electric and Cold-Sinks

There are two ways to get electrical power from streams and rivers: a turbine in the natural channel of water, or a dammed water flow that feeds into a turbine.  Turbines are often prohibited in the natural channel of a waterway because it is by law public property and a turbine would be an obstacle to other users and aquatic life.  A stream on your property can be dammed only if you have sufficient elevation difference (or ‘head’) between where the stream enters and leaves your property; however, there may be local restrictions on damming even on your own property due to water rights of farmers and ranchers downstream of your property.

After you determine if you have access to extract water power, then the measurements you need to take are the flow in gallons per minute (flow = volume  x velocity), or in the case of a dam, measure the head, multiplied by the cross section area of the outlet, multiplied by the force of gravity.  The flow can vary seasonally as well as from the center of the channel with maximum flow to the bank at minimum flow.  The beauty of water power is that it generates 24/7, unlike intermittent solar or wind power.

Hydroelectric is electricity generated by the mechanical power of the water.   Other than a dam, there are only two main components: the turbine and the generator.  Overall, hydroelectric is one of the least expensive off-grid methods to produce electric power.

Vendors of water turbines are few, partly because opportunities for home water power are limited and partly because people build their own from re-purposed components.  Vendors can provide tables for their turbine on how much power can be generated given your situation.  The minimum size hydroelectric system would require a water source with a head of about 5 feet and flow of about 15 gallons per second and would produce about 500 watts.

Relatively small turbines are used for high pressure situations like the flow out of a dam, but in low pressure situations like the flow of a river without a change in head, a large water-wheel is located on the water surface.  Usually the generator is located above the turbine, out of the water.

On-site hydro can be used as a thermal ‘heat sink’ to keep food cold.  The temperature of mountain streams and lakes are typically less than 40 degrees F—the same temperature that your refrigerator is designed to operate.  The inconvenience is access to the cold water from your home, unless your home is a ‘house boat’.  Placing the food items into the water is not going to work because food containers can become rusted or can leak, ruining the food and polluting the water. 

Cold Box for Foods

A cold exchanger with cold water or cold outside air can be used to keep food cold.  Build a cold cabinet (or re-purpose a refrigerator) with an air chamber between the food box and the outer insulated box and use a fan to circulate cold air from a crawl space or root cellar into the bottom of the air chamber and out the top and exhaust it to the outside.  Alternatively if you have a source of cold water, wrap coils of tubing between the food box and the outer insulated box, then circulate the cold water, using a pump or a gravity-fed flow of cold water by diverting a portion of a stream.

Read more:

Planning to Build Your Own House

Calculate Sun Position for Solar Gain

Christopher James Marshall Blog

Reprinted with permission from Hut-Topia: How to Create Sustainable Small Homes and Homesteads by Christopher James Marshall, 2015. You can purchase this book from the MOTHER EARTH NEWS store: Hut-Topia: How to Create Sustainable Small Homes and Homesteads.

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