In the search for renewable sources of energy, people can get pretty creative. We’ve seen firms utilize biogas from human waste, seaweed-derived ethanol, waves, and the sun as sources of energy, but here’s a new one: the city of Brainerd, Minnesota is attempting to utilize heat present in the sewers to power local heating and cooling systems. With a city name that contains both “brain” and “nerd,” I suppose we should expect some out-of-the-box ideas, right? Well this idea definitely caught my attention as being pretty unusual, but after reading more, it appears to be a viable option.
If you think about it, this idea totally makes sense. What ends up in sewers? Shower water, dishwater, hand-washing water, and toilet water. All of those items tend to be heated in some way, so you can imagine that the sewer would be a very warm place. According to the article, a company called Hidden Fuels installed sensors throughout the city’s sewers, and the sewer temperatures in Brainerd range from 42°F to 66°F. We all know that heat is potential energy. Why not take advantage of it if you’ve got it?
So, the heat is there, but how do you tap into that heat and convert it into energy? The plan is to use existing technology that is very similar to geothermal electricity systems. Here’s the gist: a heat pump is installed in buildings that will be powered by the system, water from the sewer is run through the pump, the pump contains a turbine that is moved by the water, and the turbine generates electricity.
What’s particularly cool about using the sewer for thermal electricity is that it’s expected to cost half of what a new geothermal system would cost. Much of the infrastructure needed to manage the flow of water is already in place, and the sewer water is already at the appropriate temperature. For this reason, Brainerd expects to have the experimental new system heating its first building by the end of this year.
Unconventional? Absolutely. But, at the same time, it’s pretty ingenious to find a way to extract energy from a system that is already in place. Sewers aren’t going anywhere, but, with this system, they could potentially serve two purposes. Keep it up, Brainerd-s; that kind of efficiency is just what we need in the transition to clean energy.