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Geothermal Precast Sewer Pipe Delivers Renewable Energy

Four Canadian partners adapted two trusted systems – precast concrete sewer pipe and geothermal mechanics – to supply renewable and economical energy for heating and cooling homes and businesses.

By Sue McCraven

Sometimes the answers we seek have been within our grasp all along. In our search for clean, renewable energy, the most viable solution may lie  beneath our feet. Using the proven technologies of geothermal systems and manufactured concrete pipe, four Canadian entrepreneurs have adapted an everyday precast product to efficiently capture underground energy to heat and cool our homes and businesses.

Summer or winter, the earth’s ground mass continually absorbs solar energy and exists at a constant temperature. In North America and other temperate  climates around the world, the substrate is a reliable and readily available  source of energy with a temperature of about 50 F (10 C). A remarkably practical and easily installed precast pipe system has proven to efficiently collect geothermal and wastewater energy to provide non-polluting heating and cooling for homes and businesses. Moreover, this simple system has  proved itself in one of the world’s coldest cities.

Capturing heat from renewable sources

John Hood, director of Renewable Resource Recovery Corp. (R3C),  Sudbury, Ontario, explains how he and his associates designed a patent-pending, innovative precast concrete system: “We developed @Source-Energy Pipe System that uses heat recovery principles to extract wasted heat energy and return it to warm residential, institutional, commercial and industrial buildings.”

With geothermal precast concrete sewer pipes, a heat pump replaces the  traditional furnace and air-conditioning units found in most homes. “It is the heat pump in the building that operates and controls the geothermal piping system,” says Hood, “transferring heat in and out of the building to the geothermal precast pipe system. The heat pump provides yearround comfort in the building – heating in the winter and cooling and conditioning the building in the summer.”

Field tested in one of the world’s coldest cities

Hood said that a new subdivision in Ontario has installed the geothermal sewer pipe (see the sidebar “Subdivision Installs Geothermal Sewer Pipe”). “Design calculations indicate that the main sewer line at the street frontage plus the sewer line connection from the main to the building will provide sufficient heat energy to heat a standard two-bedroom residential building.” In a pilot project in Greater Sudbury, a 2,000 sq. ft. (186 m2) home was  heated during this past winter (2009-2010) solely with the patent-pending precast sewer pipe system. The system was instrumented and performance data are currently being analyzed.

Sudbury is particularly well-suited for field testing of this new geothermal precast pipe system because, according to TripAdvisor.com, “One of the outstanding traits for which Sudbury is well-known is its frighteningly cold winter season. In fact, this city is one of the coldest cities throughout the entire world.” January and February daily temperatures average only
8.6 F and 11.5 F (-13 C and -11.4 C), respectively. Sudbury residents rarely see temperatures above 20 F (-7.7 C) during the winter.

A precaster who knows pipe

Boris Naneff, the precaster on the project and president of Rainbow Concrete Industries Ltd. in Sudbury says that any precaster who already manufactures pipe can adapt production to produce the @Source-Energy Pipe System. “Conventional precast pipe is used,” says Naneff, “and we have developed an efficient system for installing the heat exchanger in the walls of the precast pipe that carries the ethanol solution.”

Producers are welcome to visit the Sudbury plant to see the production process. As far as cost to the precaster, the plastic tubing is readily available in the marketplace and Naneff estimates that, “a precaster could expect a capital investment of around $50,000 for the license to produce. In  addition to supplies, it takes about two days of training to familiarize plant staff with the process.”

A thicker precast concrete pipe wall may be necessary to accommodate the heat-recovery extraction system. The only difference in the installation of geothermal sewer pipe from typical sewer installation would be a  certified/licensed plumbing inspector to test the external hookups for adequate pressure. There are two external hookups to connect to the home on a residential system. Additional vertical or horizontal geothermal precast pipe can be installed to augment the system for larger facilities and businesses (see Figure 1).

How geothermal piping works

Using 3/4-inch (20-mm) diameter HDPE geothermal tubes that are filled with a 30 to 70 percent ethanol-to-water mixture ratio, precast concrete domestic sewer pipes capture waste heat from sewage and latent heat from the ground to supply heating or cooling to private homes. This geothermal pipe system would function just as efficiently for commercial buildings. The normal operating pressure of the system is less than 10 psi (69 kPa).

Precast concrete pipes used for the system are no different from traditional manufactured sewer pipes with the exception of two add-on steps:

1. A heat collector system embedded in the pipe walls that extracts heat from both effluent and the soil surrounding the sewer pipe is installed in the precast piping segments.

2. Quality control: The heat exchange system is pressurized to 30 psi (207 kPa) for each 7.5-foot (2.3-m) length of pipe produced in the precast facility and tested again during site
installation.

When the geothermal wastewater pipes are installed in the ground and connected to a heat pump distribution system in the home’s basement, the ethanol/water liquid mix in the plastic tubes flows back to the house and into the heat exchanger and heat pump. In this way, heat is extracted from the soil and wastewater, and recycled in the home heat distribution system.

Geothermal energy pipes are connected in series, parallel, or in a  combination of series and parallel to efficiently extract heat from the sewer pipes and adjacent ground, efficiently heating the residence. The  geothermal sewer pipe system is a sustainable energy system that does not emit greenhouse gases, air pollutants or toxic emissions. The precast sewer
pipe system is a low-cost, safe, dependable, renewable energy source that is not subjected to fluctuating usage rates. Ground source heat pumps have a life expectancy of about 20 to 25 years. Concrete pipes will last 100 years.

Just imagine driving through a neighborhood on a frigid Canadian winter day. If the homes in the subdivision have geothermal precast sewer pipes for home heating, you would see no exhaust fumes from house chimneys, because there are no operating furnaces. For a two-bedroom house, greenhouse gas reductions are equivalent to taking three cars off the road.
Geothermal heat-recovery systems are 500 times more efficient than a standard gas or electrical furnace. For a more technical article that describes how a ground heat processor works in a precast piping system, please see the Summer 2010 issue of Precast Solutions magazine.

U.S. tax incentives for precast customers

Geothermal heat pumps cost about the same as a traditional gas or electric furnaces and air-conditioning (cooling) units. Although the @Source-Energy Pipe costs more than traditional sewer pipe, it constitutes the heating and cooling system for the building. Fortunately for American owners and municipal purchasers of the new system, significant federal tax incentives provide economic incentives to opt for renewable energy.

According to the U.S. Environmental Protection Agency and Department of Energy, federal tax incentives of 30 percent of investment cost (with no upper limit) for geothermal heat pump systems are available for both existing, new and vacation home construction. Tax incentives are due to expire in 2016. ENERGY STAR heat pumps are eligible for tax credit. See www.energystar.gov for more information.

In addition to tax incentives for installing renewable-energy systems for the homeowner or business owner, local agencies and municipalities have the opportunity to recoup additional capital expenditures for new sewer construction or for retrofitting existing infrastructure with geothermal sewer pipe: by acting as system managers. The system has been approved for Ontario’s Green Schools Pilot Initiative, paving the way for expanded use of the geothermal pipe technology for commercial and industrial  applications.

Subdivision Installs Geothermal Sewer Pipe

Project Team

Owner: Albona Investments Inc.
Engineer of Record: R. Mancini & Associates Ltd.
General Contractor: Garson Pipe Contractors Limited
Material Supplier: Renewable Resource Recovery Corp.

Naneff Gardens is an 18-home subdivision in Garson, Ontario, that has installed the new geothermal precast sewer pipe system. It wasn’t a difficult sell to the new homeowners, because, as Boris Naneff explains, “This is virtually a risk-free application, because both the precast pipe and geothermal mechanics are known and proven technologies.” Boris Naneff is the owner and president of Rainbow Concrete Industries in Sudbury and also president of Renewable Resource Recovery Corp.

But even more important than the confidence of working with established products, geothermal heating and cooling provides two very important benefits: very high energy efficiency and renewable (green) energy. “The use of geothermal pipe in my subdivision actually protects and improves the environment by eliminating the greenhouse gases associated with fossil fuel and gas-produced power. In carbon savings, we estimate that use of geothermal pipe in this one development alone is the emission-preventing equivalent of removing 54 cars from our city streets.”

Naneff, who has a new addition to his family, an infant who requires a warm environment, can vouch for the comfort of the reliable heat provided by the precast pipe system. “Because the earth is at 10 C (50 F) and the heat pump only needs to effectively raise the temperature another 25 degrees to heat our home, this system provides us with almost 500 percent efficiency over a standard furnace.”

This means for every dollar a homeowner spends on a geothermal pipe system, they will receive a return of $5 in supplied energy relative to conventional furnace heating, a 25 percent savings over alternative residential energy bills. “It was the environmental issue that sparked our interest as partners in developing this system,” says Naneff. “There’s a much stronger awareness of the financial and marketing potential of green  technology among precasters today than there was four or five years ago –
that’s for sure!”

Sue McCraven, NPCA senior technical consultant, is a civil engineer,  technical writer and editor, and environmental scientist who has  contributed numerous articles and studies to prominent scientific journals.


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