Portland, Oregon, seems optimistic about the recent installation of hydro-electric turbines in some of their city’s drinking water pipes. The project has been getting a lot of press of late; check out this January 17, 2018 feature:
PBS also detailed the project in this six-minute feature: https://www.pbs.org/newshour/show/water-power .
It’s an exciting idea, but can it work in Vermont?
Offhand, one would think so. Water’s electrical energy potential is largely a matter of “head” (how far water falls) and “flow” (how many gallons per minute). We have good precipitation to provide flow, and most areas have enough head thanks to high hills and a population concentrated mostly in river valleys.
In fact, the potential for in-conduit microhydro has been considered in Vermont for years. In 2013, Barre hired Rentricity, Inc., to construct a 12 kW demonstration project, using grant funds from the Vermont Clean Energy Development Fund and Vermont Agency of Natural Resources. It diverts, and returns, 400 GPM of the city’s approximately 4,000 GPM average flow.
According to William Ahearn, Barre’s director of Public Works, the unit is still up and running. However, it has never delivered its theoretical full output capacity. Ahearn blames nuances of pressure and electrical management technologies, and says the city and manufacturer are continuing efforts to improve its performance. Below: The Barre unit.
You can read about the Barre City case study, and see photos, at: https://rentricity.com/wp-content/uploads/2014/07/City-of-Barre-Case-Study-7-14.pdf . Fuss & O’Neil partnered with EcoStrategies to create this presentation about Barre’s potential: http://www.vecan.net/wp-content/uploads/jeff-McDonald_VECAN_Barre-Micro-Hydro-Project.pdf
Bennington also installed a small in-conduit unit in 2014, about the same generation capacity as Barre’s. According to Bennington water operator Brian Billert, it works well most of the time, but high silt levels brought by heavy rains can impair function. Below: Bennington’s setup.
Does your town have what it takes?
For a seat-of-the-pants guesstimate: Power (in watts) = Head (height, in vertical feet, between your source and your treatment plant) X Flow (in gallons per minute) X 0.09 (factor for turbine efficiency, pipe losses, friction, etc.). H X F X .09 = generator’s watt capacity.
Example: Your reservoir intake is 300 feet above your treatment plant, and it feeds you 2,000 gallons per minute. 300 x 2,000 = 600,000. Now, factor in the 0.09, and you get 54,000 Watts, or about 54 kiloWatts (kW) maximum electrical generation potential.
If a 54 kW (average capacity) turbine runs all day every day, you get enough juice to supply electricity to 69 Vermont homes (per Green Mountain Power residential 2016 averages).
Of course, it depends on how much of your total flow you divert to the unit. Also, daily water volume use and electrical demand vary, and maintenance downtime can change this equation. And, to the H X F X .09 calculation, add an unknown factor for a town’s enthusiasm for innovating — and spending money.
For more information, here’s a more detailed discussion from the Water Power Magazine: “Energy Recovery from Public Water Systems” article: http://www.canyonhydro.com/news/SOAR_IWPDC.pdf
If you have any questions, or have experience with in-conduit micro-hydro, please leave a comment! To return to GMWEA’s website, click here: www.gmwea.org.