Energy harvesting — the siren’s allure

My wife, Deborah Mills-Scofield monitors dozens of media outlets and forwards articles to me that might be of interest.  One recently came my way about an effort in Portland, ME to harvest hydroelectric energy from its water pipes.  A company, LucidEnergy, has developed turbines that can be installed for this purpose.  The basic idea is to capture free energy in municipal water pipes that would otherwise be wasted.

While I applaud such innovation and creativity, I find the effort is misplaced.  I predict these turbines, like solar panels of the 1970’s and green roofs of this last decade — will soon be removed and abandoned.  This kind of energy harvesting is a fool’s errand.

About a decade ago I learned about another energy harvesting project in Israel — to install piezo-electric tranducers in highways to capture energy from passing trucks.  As heavy vehicles passed over these tranducers the truck weight would cause the transducers to compress and produce electricity.  The promoters of this energy argued that normal road compression represented lost energy — their technology would capture energy that would otherwise be lost.  The installed transducers did, in fact, produce electricity.  But I am confident that careful analysis would show that this energy comes from slight increase in fuel consumption of the vehicles that pass over the transducers.  Highway rolling resistance is mostly due to compression of the tires, not the road surface!

I am not aware of any evidence that water passing through municipal pipes arrives at end destinations with excessive kinetic energy.  Therefore any energy harvested along the way is likely to have to be re-injected by pumps.

And the maintenance issues must be significant.  I envision a few years of testing at the end of which it will be concluded that the cost of maintaining these units far exceeds the value of the energy they generate.  And what about the maintenance of pipes which get plugged due to low flow velocity?

Nature has handed us sunlight, wind, and hydo energy.  Harvesting these abundant resources is proving to be a challenge.  Harvesting efforts should focus on these well-understood and low-maintenance options.

Humans clearly waste a terrific amount of energy.  And there are many different ways that this wasted energy might be harvested.  The problem is cost-effectiveness.