It's a simple concept, and one of those "why didn't I think of that" for folks all around the globe: As water flows through city water pipes, embedded turbines spin, powering attached generators, which then feed energy back into the city’s electrical grid.

This aptly describes phase one of a project in Portland, OR, where the city water department has replaced a section of its existing water main with Lucid Energy pipes containing four 42-inch turbines. Known as the “Conduit 3 Hydroelectric Project,” Portland’s new clean energy source is expected to be up and running at full capacity this month.

While the Portland project is snagging the headlines, it's an idea that has been pioneered in many municipalities, including 10 New England towns that have installed or proposed in-conduit hydroelectric systems, using a variety of turbine types. (See PDF: "In-Conduit Hydropower Project – Phase I Report," submittend by Alden Energy to Massachuttes  Executive Office of Energy & Environmental Affairs, August 2013).

A project in San Diego at the Ranchos Penasquitos Pressure-Control Hydroelectric Facility is up and running with a 4.5-megawatt turbine generator in one pipeline capable of providing enough electricity to power 5,000 homes.

At this time, the Portland project is only generating 200 kilowatts (0.2 megawatts), enough to power about 150 homes. Portland is only "first" at securing a 20-year Power Purchase Agreement (PPA) with a municipality.

The path was cleared in the U.S. for in-conduit hydropower by the enactment of the Hydropower Regulatory Efficiency Act of 2013, which exempts conduit hydropower facilities from the licensing requirements of the Federal Power Act.