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By Lynn Mueller
Whether you call it green plumbing or simply smart economics, the underlying theory is the same. Environmental and economic issues are driving plumbing engineers to design piping systems that use fewer resources and have minimal impact on our planet.
Historically, as societies grew more complex, plumbing systems became more innovative. This was demonstrated by the Romans whose aqueducts recycled bath water to flush out latrines and irrigate gardens. Somewhere along the line, however, society lost the pressing demand to conserve natural resources. Recently, due to the rising price of energy and the threat of climate change the building industry is asking, “How can we use a whole systems approach to re-design plumbing so that energy and resources are used more efficiently?”
Today, the U.S. Environmental Protection Agency estimates as much as 30 to 50 percent of the energy and water that flows into our buildings is wasted. With more than 5 million buildings in the U.S. alone, this leaves plumbing engineers in a unique position to influence the design of smarter buildings by employing cradle-to-cradle techniques; re-using materials before eventually “downcycling” them to waste.
Water heating is an example of where this technique can be employed. Water heating is the third largest energy expense in residential buildings and typically accounts for 14 to 25 percent of the energy consumed in our homes. For commercial and industrial buildings, like hospitals and laboratories, this percentage can be even greater.
A variety of energy efficient solutions are currently available for improving the distribution and operation of a hot water system (such as adding piping insulation and using WaterSense labeled faucets and showerheads that function at lower flow rates). Until recently, however, in regards to heating water in our buildings few options other than converting electricity, natural gas or using solar energy, have been on the market.
The simple fact is that water enters our buildings at 40°F to 50°F, and leaves at 66°F to 77°F. If captured, this heat could be used to fulfil 40 to 50 percent of our building energy requirements.
Capitalizing on this temperature differential is a system called Sewage Heat Recovery (SHR). SHR is designed to recycle up to 95 percent of the inherent heat in wastewater back into the building. The technology is not complicated. First, a filter separates out solids from the waste stream. Then, with the help of a heat pump and heat exchanger, it uses the warm water from the wastewater stream to heat the buildings hot water system.
At the end of the cycle, the clear sewer water picks up the solids extracted at the start and flushes them back into the municipal sewer system.
This energy saving technology is an environmentally friendly and cost efficient solution for multiple unit residential, commercial buildings and energy districts water heating systems. SHR systems can work at 500 to 600 percent efficiency, meaning that for every dollar spent on operational costs, $5 worth of heat is recovered. Plus SHR systems can be applied to both new and retro-fitted buildings. As a result, demand for SHR systems is increasing worldwide and SHR projects have been launched in cities across North America, Europe and Asia.
The Sail Project in Vancouver BC is one example. This new, 172-unit condominium project is a highlight of the University of British Columbia’s sustainable community plan. The Sail Condominium has newly installed a Sewage Heat Recovery system called the SHARC, which not only produces hot water but also contributes to heating the building via radiant floor heating. The system generates 220,000 BTU’s per hour, reducing the buildings emissions by 100 tonnes per year and contributing to the Sails’ excellent REAP Platinum building standard.
In fact, all existing SHARC installations are presently demonstrating consistent energy savings of at least 76 percent. Added benefits of the SHARC system include full automation with a Direct Digital Control (DDC) or Building Automatic Control Network (BACnet) interface and a wireless or Ethernet connection for data retrieval and instantaneous calculation of greenhouse gas (GHG) savings.
The SHARC unit and the heat exchanger are connected using 316 steel, 6-inch piping. The valve tree is designed to allow for reverse flow back flushing of the heat exchanger which is part of the quarterly scheduled maintenance and the system is equipped with drain down ports for maintenance purposes.
While the modular nature of the SHARC means it can be matched to a building of any size, the technology is most efficient for residential buildings greater than 50 units or with institutional buildings like hospitals and prisons that have exceptional hot water usage.
SHR is one example of an engineering solution that is both green and cost-effective. Plumbing engineers play an important role as stewards of our natural resources, and the decisions they make will have long-term effects on both our economy and the health of the planet. The future of plumbing engineering will be about designing smarter systems with the “whole building” in mind, effectively utilizing water and energy in a way that leaves little to waste.
Lynn Mueller is the president of International Wastewater Systems, located in Vancouver, British Columbia. She has been a leading advocate of sustainable space conditioning energy systems for the last 25 years, and has pioneered many innovative energy approaches.