Sunday, November 27, 2011

Harnessing the Untapped Energy in Water Pipes

Water is often stored high above the city that consumes it. To reach its destination, water travels through a system of gradually shrinking pipes until it comes out the faucet. As the water travels, excess pressure gathers in the pipes, which is dissipated by pressure valves. All that built-up energy leaves the system, wasted.

This type of energy waste is hard to design away. Some water systems are so old they still have hollowed-out cedar logs as pipes. And huge numbers of people depend on the systems continuing to function without a break. So rather than figuring out ways not to waste energy, it's easier to harness and repurpose it. Rentricity, an energy company based in New York City, is doing exactly that by creating electricity from excess pressure in water pipes.

Frank Zammataro, Rentricity’s president, learned about the inefficiencies of municipal water systems after he spent too many hours thinking about a New York City water tower. In 2001, he and his colleagues looked down from their 40th floor Midtown office on the building below and joked about how every time someone flushed on the first floor, water had to travel from the tower on top of the building all the way down. Someone, they thought, ought to put in a wheel in the pipe to capture that squandered energy.

Zammataro took the idea seriously enough that he scheduled a visit to Rensselaer Polytechnic Institute in upstate New York to investigate further. The professors told him that a single building didn’t have enough sustainable flow or pressure to make harvesting the energy practical. But one suggested he take a look at municipal water systems and the points where they regulate pressure in the pipelines.

Rentricity takes the energy from those points in a water system and uses it to turn a turbine, creating electricity. The system itself didn’t require any breakthrough technology: the company’s primary innovation was recognizing that a valuable resource was being thrown away. “We applied the technology in a unique way and in a unique place,” says Zammataro. “We're not innovating at a turbine level.”

by Sarah Laskow, Good |  Continue reading:
Photo via (cc) Flickr user CarbonNYC