Could waste heat in sewers heat buildings? Untapped energy flowing under Brainerd

When we think of new sources of energy, we often look up at the sun or the wind. But some people decided to try looking down instead. Underground. In the sewers of Brainerd.

A study, financed by a state grant and carried out by Hidden Fuels of Brainerd, shows that energy available to cool and heat homes and public buildings in Brainerd flows through the sanitary system every day.

Area government officials and folks interest in energy solutions gathered recently at the Brainerd Public Utilities building to hear about results of an extensive study to find captured heat and cooling capacity in the sewers that run through Brainerd.

On January 25th, over 45 people gathered at a Central Region Clean Energy Resource Team (CERT) forum at Brainerd Public Utilities to hear about research into extracting energy from wastewater. Al Cibuzar, Jeff Aga, and Pete Nelson presented a study done by Hidden Fuels. The ultimate goal is to capture energy in the waste stream under Brainerd. And Brainerd Public Utilities, the city of Brainerd, and Earl Wolleat, superintendent of buildings for the Brainerd School District, partnered on the study. Hidden Fuels is a renewable energy company providing services and products to efficiently capture and distribute unused energy from waste (primarily home) municipal wastewater and biomass wastes. “Given the need for both energy independence and better wastewater treatment methodologies in the United States and abroad, technologies capable of harnessing usable energy from waste are in demand,” their literature says.

“We received a state grant to conduct research,” explained Aga.

For 16 months, from Oct. 2010 to Jan. 2012, Hidden Fuels and their partners collected data samples from sensors installed in the Brainerd sewer system. First, they located all the lift pumps in the large system and they installed sensors in the pumps.

Cibuzar passed a used sensor around. “These have been coated with balls of fat as big as basketballs,” he said about the environment in the sewer.

Studying over 1 million data points revealed important information about flows and water temperatures and determined that through a yet-to-be-developed system, they can pull both heating and cooling energy from the sewer system—energy that is now, literally, going to waste. The study showed that the underground temperature varies because of time of day but the average temperature is around 45-60 degrees.

“Is there the flow needed to make heat?” asked Nelson. “Yes, and it’s a good match to where the energy is needed.”

The highest temperature of waste water, around 78 degrees, was found in an industrial park where a commercial laundry was operated. The coldest was down to 38 degrees at the Brainerd Public Utilities plant. The group determined that there is energy available to heat hundreds of homes and several public buildings in Brainerd. They narrowed their focus to how they could heat the Brainerd High School, The Brainerd Police Department and the North Star High Rise building with waste water energy.

At BHS, they figured a new system would save $17,300 on heating costs and that they could save $8,300-$9,000 at the police department and $6,000 to $8,100 at the high rise—which is not as efficient. Cost savings will depend greatly on the cost of natural gas. Now, due to the poor economy, natural gas is very cheap. But the higher the price of gas goes, the more economical this alternative waste energy source becomes.

Conclusions were that the study verified the sewer sheds in Brained and what in the city flows where, it created a thermal energy map, it showed that a significant amount of energy is available from the sewer system (even though they don’t yet know how to get it out). It also indentified the buildings that could use waste heat and identified an untapped renewable energy source for future infrastructure and building plans.

Although the technology of how to extract the energy from the sewer system needs to be refined, it is intriguing that in the future we may be recycling energy from our own waste stream to heat and cool our neighborhoods. Future work could include evaluating present geothermal technology and researching methods of extracting heat from uncontaminated sewage flows. The tremendous amount of data they collected in Brainerd has been compressed and can be used as a template for research in other locations. The ultimate goal would be to design and build a suitable apparatus for waste water energy capture.

“The purpose of the study was to find out how much energy is going where,” said Nelson.

Although such alternative sources of energy may be a future reality, it is a discipline being studied carefully by many engineers and scientists. Who knows, they say, what may be possible? They encouraged everyone at the meeting to think about how much wasted energy they are flushing down the drain each day.

“Geothermal, that’s where the thinking for this really started,” said Nelson. “Trying to capture the heat that’s constantly flowing in the sanitary sewers. ‘Once a mind is expanded with a new thought it never returns to its original dimension,’” Nelson pointed out.

That quote was from Albert Einstein and illustrates that once engineers and scientists, partnering with cities and utilities and businesses, start thinking of new ways to extract energy for America, there are no limits on where that thinking could take them.

Following the Hidden Fuels presentation, the conversation shifted to opportunities for businesses and residents to reduce energy costs with energy efficiency. Scott Sjolund (Brainerd Public Utilties) and Rick Pederson (Crow Wing Power) both presented about their utilities’ incentives and rebates. Joel Haskard, CERTs Co-Director, presented about solar projects happening on farms, small businesses and homes. “Solar is a job creator for Minnesota,” Mr. Haskard noted. “With the price of panels dropping and the number of Minnesota manufacturing plants and trained installers expanding, we hope to provide people easy access to information so they can connect with these businesses and learn more.”

This article originally ran in the February 10, 2012 edition of the NewsHopper out of Brainerd, MN.

About the author: Ann Schwartz is a freelance writer living in Aitkin, MN with an interest in science, environment, and alternative energy topics. She has been published in newspaper, regional magazines, and a book published by the University of MInnesota. You can contact her via email with any questions.

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