It sounds so sensible, you have to wonder why everybody isn't already doing it: Tap the excess pressure found in many urban water mains to drive small turbines that could feed electricity into the grid, block-by-block. Often such pressure has to be relieved by means of specially installed valves that do no work. Why not exploit it to generate power?
It took a New York City wireless company executive, musing idly about emergency power shortly after 9/11, to dream up the idea of electricity from water mains. The startup he founded and leads, Rentricity, has been attracting attention and interest locally. It has obtained modest R&D funding from the New York State Energy Research and Development Authority (NYSERDA) and is a tenant of the New York University Polytechtechnic Institute Incubator that was started by the New York City Accelerator for a Clean and Renewable Economy. On 1 May, NYC Mayor Michael Bloomberg signed into law a city council resolution calling on New York to do an 18-month study of the feasibility of widely deploying electricity-from-water-main technology throughout the city.
The city, which gets all its drinking water from reservoirs that at are much higher elevations upstate, has a water distribution system that is inherently highly pressurized. As such, it would seem to be ideal for what Rentricity is proposing to do. It is not, however, the site of the first test installation. That honor goes to Keene, N.H., a town close to that state's southern border and Boston's high-tech periphery. Rentricity has also installed a 30-kilowatt generator at a reservoir near Pittsburgh; though that setup is in a water distribution system, it is basically a standard low-head hydro installation, and not an example of the power from water mains concept.
Could Rentricity turn out to be a company that is better at PR than engineering? To judge from its website, the opposite may be the case. The listing of its executive leadership makes a credible impression. The videos promoting its work, on the other hand, leave a good deal to be desired in terms of production values.