Don’t Forget About Micro Hydropower

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infographic by US-DOE depicting a typical micro hydropower system courtesy of DOE.Maine is riddled with opportunities to generate power from streams, rivers and tidal inlets. Our forefathers hitched these power sources up and used them to great advantage. What happened? More importantly, how soon can we go back to using this resource? Here is a brief primer on some of the ways.

How a Microhydropower System Works

Hydropower systems use the energy in flowing water to produce electricity or mechanical energy. Although there are several ways to harness the moving water to produce energy, run-of-the-river systems, which do not require large storage reservoirs, are often used for microhydropower systems.

For run-of-the-river microhydropower systems, a portion of a river's water is diverted to a water conveyance -- channel, pipeline, or pressurized pipeline (penstock) -- that delivers it to a turbine or waterwheel. The moving water rotates the wheel or turbine, which spins a shaft. The motion of the shaft can be used for mechanical processes, such as pumping water, or it can be used to power an alternator or generator to generate electricity.

A microhydropower system can be connected to an electric distribution system (grid-connected), or it can stand alone (off-grid). Read more about microhydro from the DOE here.

Ideenergie river turbine in operation image courtesy of IdeenergieWhat Is New In Micro-Hydro Technology?

One company from Canada is offering a small, portable, in-stream turbine for rivers and streams. According to Idénergie, rivers offer the best energy potential compared to other renewable sources of energy. Providing constant energy 24 hours a day, Idénergie’s river turbine can meet the electric needs of a residence by producing, at maximum capacity up to 12 kWh daily, depending on the water velocity of the river.

The reliability of the river turbine offers a cleaner alternative to gas generators for remote or backup power needs. Read more here.

RivGen system by Ocean Renewable Power Company in operation courtesy of ORPCCommunity-Sized Hydro

On a somewhat larger scale, the RivGen® Power System from Maine’s own Ocean Renewable Power Company (ORPC) is specifically designed for generating reliable, renewable electricity in rivers near remote, "islanded" communities with no access to large, centralized power grids. Whether surrounded by expanses of uninhabited land or water, these communities pay up to 15 times more than the cost of power from a utility grid because of their reliance on expensive, polluting diesel fuel generators.

The RivGen® Power System connects directly into existing community grids and provides automatic fuel-switching so that whenever the RivGen® System is generating power, the diesel generator automatically turns down or off.

Learn more and read about pilot installations here.

Stroudwater Tidal Mill image courtesy of Halliday Historic Photograph CompanyTidal Mills

A tide mill is a water mill driven by tidal rise and fall. A dam with a sluice is created across a suitable tidal inlet, or a section of river estuary is made into a reservoir. As the tide comes in, it enters the mill pond through a one way gate, and this gate closes automatically when the tide begins to fall. When the tide is low enough, the stored water can be released to turn a water wheel.

Tide mills are usually situated in river estuaries, away from the effects of waves but close enough to the sea to have a reasonable tidal range. These mills have existed since the Middle Ages, and some may go back to the Roman period.

According to historian Bud Warren of Topsham, there were at one time up to 150 tidal mills in operation along the coast of Maine, including one at Stroudwater (pictured).

Warren is a member of the Tide Mill Institute at Dorchester Historical Society, an organization for the study of tide mills and tide mill sites that puts on an annual conference with international participation.  Learn more here.