Interesting Twist on Hydrokinetics

Here’s a renewable energy concept that I’ve been seeing here and there over the past decade.

It’s a means by which a city can generate clean electricity from the water flowing under streets through pipes.  It appears that Portland, the largest city in Oregon, has replaced a section of its existing water supply network with pipes that contain turbines (shown above).  As water flows through the pipes, the turbines spin and power attached generators, which then feed energy back into the city’s electrical grid.

Caveats as I see them include:

• Limited to gravity-fed pipes.  If you’re pressurizing the water in the pipes and then taking energy out, you’re running at a net loss, per the second law of thermodynamics.

• Cost. If you’re repairing or replacing pipes, it’s possible that this has merit, but digging up and replacing working water-delivery infrastructure could never be anywhere near cost-effective.  It’s worth noting that the video linked above doesn’t mention LCOE (levelized cost of energy, the only important parameter by which energy sources can be compared).  Another cost item is tying these generators to the grid.

It all comes back to the pithy statement made by 2GreenEnergy associate Dr. Peter Lilienthal, arguably the world’s foremost expert in hybrid power optimization, who told me, “If you don’t care what you pay for electricity, I’ll get you all the renewable energy you could ever possibly use.”