Tuesday, December 29, 2009

Distributed Hydropower for Irrigation Districts

Irrigation districts can be found in nearly every state in the US. Operated, and often owned, like any other utility, irrigation districts provide water for crops, orchards, vineyards spread along the length of their maintained canals.

For many irrigation districts, electricity, primarily to power water pumps, is a significant cost--sometimes the second largest line item in their operating budgets, costing $1,000,000 or more every year.

Hydrovolts turbines can halve the cost of electricity in gravity-fed irrigation canals, providing a capital ROI to the districts of less than 5 years in Washington state. Because Washington State has the cheapest electricity in the entire US, the payback period in other states is even better. In California the expected capital ROI is 2-3 years.

These payback periods compare very well to other forms of distributed renewable energy generation--wind at 10+ years and solar at nearly 20. Plus, Hydrovolts turbines run continuously with the flow of the water; the power is neither intermittent nor variable.

One can think of an irrigation canal as a water terrace system, or a series of long shallow steps. Maintaining each "tread" at a specified height is very important to allow the pumps along the banks to have their intakes properly positioned, ensuring steady delivery of water to the fields.

The height in each tread of the canal is controlled by a check weir, the "riser" in this metaphorical water staircase. Each check weir has one or more adjustable sluice gates that control the flow of water from one canal section to the next. By raising or lowering the gate, the water behind (upstream from) the check weir can be kept to a specific level with great accuracy.

Just below the check weir the water is moving fast and has a lot of power. We have measured many flows in eastern Washington canals at greater than 10 knots (5 m/s) where even a small Hydrovolts turbine could generate 20kW, enough to run five 5 h.p. pumps. Many such locations would accommodate multiple turbines, as many as 6-10 in the larger canals.

A typical irrigation canal may stretch for 50-100 miles and typically has scores of check weirs. Each irrigation district is a potential customer for hundreds of turbines.

Many foreign countries also have extensive canals and irrigation systems well-suited to the Hydrovolts turbine.

There are many kinds of canals other than those in irrigation districts which could host turbines to create power. Transit canals, systems of locks, aqueducts and other fresh water supply systems could all be customers for new, distributed hydropower.

See also: Distributed hydropower for

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