The latest developments in engineering, as part of Progressive Engineer (www.ProgressiveEngineer.com), the online magazine and information source with a sustainability slant.
Saturday, October 22, 2011
Power in a drainpipe: A business thrives around a novel device that recovers heat from water flowing down the drain
RenewABILITY Energy’s CEO Gerald Van Decker with his invention
George Hayden, Jr. lives with his wife and four young children in a 4200-square-foot two-story craftsman traditional house near Mountain Top, PA. When I ventured to their abode in a new upscale wooded development, his wife welcomed me and asked if I wanted coffee. But while that added to the ambience and made me feel at home, this wasn’t a social visit. I was here to check out the plumbing and see a unique energy-saving device known as a Power-Pipe made by RenewABILITY Energy.
“This house was done as energy-efficiently as we could within limits,” Hayden told me as we walked into the mechanical area downstairs. They have a Rinnai Hot Way natural-gas-fired on-demand water heater, also known as a tankless water heater. “This with that makes a big difference,” he says in pointing to the water heater and then the Power-Pipe.
With headquarters and a manufacturing facility in Waterloo, Ontario (Canada), west of Toronto, RenewABILITY Energy has made its mark in so-called drain water heat recovery (DWHR) technology. Made of copper, the Power-Pipe DWHR system is a double-walled heat exchanger that recovers heat energy from the wastewater flowing down your household drain and uses it to warm incoming cold water. They sell it through retailers such as Sears and Home Depot and distributors.
This takes advantage of the fact that nearly one-third of the energy you consume in your home goes to heat water for everyday household tasks, but 90 percent of that energy runs down the drain, mostly in your shower. In North America alone, this loss amounts to about $40 billion a year.
Single-family homes as well as multi-unit residential, commercial, institutional, and industrial buildings can take advantage of the Power-Pipe to reduce energy use and water heating costs. Joel Murray, technical support manager at RenewABILITY Energy, reports, “The residential sector has been the major market focus. We have had moderate success with the commercial and industrial sectors. We do some applications for larger more industrial or commercial applications where they manifold several Power-Pipes together.”
The Power-Pipe is based on a principle known as the falling film effect. Water falling through a vertical pipe doesn’t run down the center of the pipe but instead clings to its inside wall, creating a thin film that maximizes the Power-Pipe’s ability to recover heat energy.
Multiple coils of rectangular copper tube wrap together in parallel around a central copper drainpipe. Hot water flowing down the drain transfers its heat to incoming cold water moving up the coils in a counterflow mode. Having multiple coils allows for adequate flow with no discernible water pressure loss. Falling film heat exchangers have actually been around for decades, but previous designs consisted of a single coil wrapped around the drainpipe, restricting flow, or used a non-counterflow design, which reduced heat transfer performance.
The drainpipe and Power-Pipe have the same nominal diameter, with the Power-Pipe installing vertically. Typical residential drainpipes are either 2 or 3 inches in diameter, and the Power-Pipe comes in diameters of 2, 3, 4, and 6 inches. The preferred configuration for providing maximum energy savings plumbs the home's main water line through the Power-Pipe. A second option is to plumb cold water through the Power-Pipe to the water heater only. A third configuration consists of running cold water through the Power-Pipe to the cold side of the shower fixture only.
Accommodates Growing Family George Hayden built his new house in 2010 to accommodate his growing family and wanted to go with renewable energy as much as possible. It has four bathrooms, three tied into the Power-Pipe in a three-inch drain line downstairs. The outlet from the Power-Pipe feeds to the hot water line upstairs to supplement the water heater. In keeping with the renewable energy theme, they plan to add a 10-kilowatt solar photovoltaic system to the house.
George Hayden installed a Power-Pipe in his new house to save on utility costs.
In their previous house in Hazleton, PA, the Haydens had a traditional electric tank water heater and two showers. Their gas bill runs about $60-70 a month now compared to an electric bill of roughly $100 a month before. The only drawback they notice is a small restriction on the cold water supply going to more than one of the showers because it is being diverted to the Power-Pipe.
RenewABILITY Energy claims that using a Power-Pipe can raise incoming supply water temperature from 50F to 77F and reduce overall household water heating costs by up to 40 percent with a payback of 2 to 6 years. A significant potential for energy and cost savings often comes in industrial applications because of the large volume of heated fluids consumed. The Power-Pipe can recover up to 70 percent of waste fluid heat and use it to preheat fluids before they enter a primary water heater. And institutions can recover up to 60 percent of that wasted heat energy with a Power-Pipe.
Gerald Van Decker invented the Power-Pipe and founded RenewABILITY Energy in 2000 and serves as the company’s CEO. Before that, he worked at Natural Resources Canada (NRCan), where he engaged in project management and R&D activities in active solar technologies. Van Decker has a Master's degree in mechanical engineering and Bachelor's degree in systems design engineering, both from the University of Waterloo in Canada. And he is a Professional Engineer registered in the province of Ontario.
RenewABILITY Energy has about 20 employees, including 3 engineers. A mechanical engineer, Joel Murray has worked there five years. “This being a small company, my roles are diverse. I do everything from technical support to designing and sizing systems for larger commercial and industrial applications to process improvements on the technical manufacturing process,” he explains. They custom design Power-Pipes for larger flows and complex plumbing designs, while smaller systems are standard. They do energy recovery analysis to show customers the potential with their hot water. And they design tools to streamline the manufacturing process, which becomes more important as production ramps up.
The company does all the Power-Pipe manufacturing itself. They use copper DWV (drain, waste, and vent) tubing for the inner drainpipe and Type L or Type K copper for the outer coils, silver soldering or brazing the parts. “The main part is wrapping the coils. The rest is brazing the coils into a manifold with a silver phosphorous alloy using an oxyacetylene flame. It’s a very manual process,” Murray says. They purchase the copper tubing in standard round form from a copper mill in the U.S. and form it into its rectangular shape using a proprietary process.
According to Murray, RenewABILITY Energy sells Power-Pipes “all around the world. Since we’re located in Ontario, the biggest market obviously is Ontario. We also sell a good number of units all across Canada and the U.S. We sold some in a couple of different countries in Europe -- Bulgaria, France. Also Mexico. It’s becoming a more well known technology.”
Education Plays a Big Role But even with this success, the company is still ramping up, and they find themselves in a constant education mode, Murray says. “It’s not a standard technology in the home, so we go around to engineering and architecture firms and designers and offer programs to learn about this technology. While it is a very simple technology, drain water is not something people think about for saving energy. Once they use that water, it flows down the drain and out of sight and mind. We’re there to show them how much energy actually is flowing down the drain.” They’ve developed courses for the American Institute of Architects and the U.S. Green Building Council, and they go to their chapters giving presentations.
Murray adds, “I was involved in designing an enclosed working display where we can create a hot water stream and a cold water stream and actually have one of our units in place that shows how much heat can be picked up.” They take this to trade shows.
Is it fun? “Oh, definitely,” Murray replies. “Especially during the education and design phase where people get that ‘aha’ moment that the potential is there. Green technology is one of the hottest markets right now, and there’s a lot of focus being put on it from many different perspectives.”
It helps that the Power-Pipe qualifies for financial incentives under numerous government and power utility energy efficiency programs. Murray says, “Utilities and energy companies have really backed the technology and offered aggressive rebate programs to their customers. That’s been the biggest surprise. They have programs for homebuilders across Canada and America.” Main examples have been Minnesota Power and utilities in Iowa and California.
Hayden’s Power-Pipe works in conjunction with this gas-powered tankless water heater
George Hayden discovered the Power-Pipe when RenewABILITY Energy rented space in a building in Hazleton that George J. Hayden Electric-Communications worked on. They have their U.S. office there. “I wanted to try their product,” he recalls. Hayden’s plumber followed the directions for installing the Power-Pipe and found it installed easily.
It’s not surprising that Hayden would embrace an energy-saving device considering his company’s direction in recent years. His father George J. Hayden started George J. Hayden Electric-Communications in 1975 as an electrical contracting company serving residential, commercial, and industrial markets. George F. Hayden, the son, serves as vice president of operations. In recent years, the firm has gotten into renewable energy, mainly installing solar PV panels and maintaining the electrical components of wind farms such as substations and transformers – the area around Scranton, PA has seen several wind farms go up in recent years.
With companies like this promoting the Power-Pipe and RenewABILITY Energy engaged in its extensive educating and marketing effort, we may all have a Power-Pipe in our home some day, and drain water will figure prominently in the energy mix.