People PowerProject Update

Lessons Learned: Municipal Sewer Heat Exchange

By June 15, 2018 No Comments

We discussed in a previous post how we chose a municipal sewer heat exchange as one of our energy reduction strategies for the AGU building renovation. Now, our partners from Interface Engineering share the scoop on the installation process and the lessons learned along the way.

The entire process required collaboration with a lot of different participants including the project partners, DC Water and HUBER Technology, the manufacturer of the municipal sewer heat exchange system. In fact, HUBER Technology visited for both the exchanger’s initial start-up and final hook up in June.

As you can imagine, drilling into a 100+ year old sewer line requires a lot of planning. Samantha Patke of Interface Engineering says, “A lot of consideration went into how to stabilize and safely excavate around the building and the sewer line to get the connections between the sewer and the wet well where they needed to be.  The sewer line was completely reinforced with concrete before the drilling of the supply and return lines into it.”

Not only that, but the partnership with DC Water, as well as their approval and willingness to take on the endeavor with AGU, was critical to the success of the sewer heat exchange system. Patke says, “There were numerous meetings and reviews with the design team, including civil and mechanical engineers, MGAC, AGU, Skanska and DC Water’s engineers and representatives. This installation needed to maintain the integrity of the DC sewer system and work effectively with the HUBER Technology but be constructed in a safe manner. No parties involved had ever undertaken anything like this before and was quite the learning curve.”

The team adds that testing for temperature and flow inside the sewer line was essential to get accurate data on what AGU’s system would be pulling from the sewer. Patke says, “There were many calls and meetings with engineers from HUBER in Germany to go over the sewer testing results, how AGU’s system would operate and perform, and how the HUBER equipment worked into this system.”

 

View looking down on the wet well.

View of the wet well on April 5, 2018. Photo Credit: Kevin Koski.

Another important consideration for the municipal sewer heat exchange system was for its maintenance. The team had to ensure not only that the exchanger had ample space for the recommended yearly maintenance, but also that they considered what the wet well in the plaza that accesses the sewer needed.

We previously mentioned that the building’s design and construction team went to visit HUBER’s factor in Germany and toured a number of installations to prepare. Ultimately, when it came to actually installing AGU’s municipal sewer heat exchange, one of the most challenging aspects was actually pretty mundane. Placing a heat exchanger that is relatively tall in a garage with a low ceiling proved challenging. The team says they had to turn the equipment on its side in order to get it down the parking garage ramp and into the mechanical room.

For another organization looking into this type of technology, Patke offers the following advice, “First, you definitely need to get the water authority on board with this type of technology and being able to tap into their sewer system. Next would be determine the flow and temperatures of that water to gauge how much energy transfer you would be able to get and if that is enough to cool and/or heat a building of the project’s size.”