King County Opens The Door For Heat Energy From Wastewater

Aug 3, 2012

The Department of Energy estimates that 350 billion KWH of energy are flushed down drains in the form of heated water. King County is one of the first counties in the nation to try to do something about all that wasted heat energy. EarthFix’s Ashley Ahearn reports.

Jessie Israel looks down into an open sewage pipe at a construction site near Discovery Park. She handles resource recovery for King County’s Wastewater Utility.

Stinky water rushes beneath the construction worker’s feet below us. But Israel doesn’t think about it as stinky water.

Israel: “The vast majority of what’s going out to the plant is water from running our laundry, the sink, your shower this morning. We flush a lot of hot water, a lot of energy down the drain and you can see it right here, we’re trying to figure out how to capture that and use it in buildings.”

Israel sees that warm sewage water as energy. The average temperature of the water rushing through this pipe, and hundreds of miles of sewage and wastewater pipes in the county, is a pretty constant 65 degrees.

King County is looking for partners in the private sector who want to harness that heat and use it in buildings.

Israel: “We’re essentially going to match-make places where we have pipes full of sewage, full of all that hot water, next to a piece of developable land, with a developer that is a deep green developer that wants to innovate and integrate new technologies.”

To be clear: King County is not paying the contractors. They’re just offering them access to their pipes. And they are one of the first counties in the nation to do so.

Another point of clarification: warm sewage water is not getting funneled around buildings to provide heat.

Lynn Mueller owns a company in Vancouver, BC that installs systems to extract heat energy from wastewater. He says, in order to understand this, picture your refrigerator.

Mueller: “So you know how your fridge works, you put warm beer in the fridge, pretty soon the beer is cold and the back of your fridge is warm? Well you’ve moved heat from that warm material in the fridge to outside of the fridge and that’s basically exactly the same system – it’s a heat pump.”

So the warm wastewater in the sewage pipe provides the heat – just like the beer in the fridge – and then that heat is used to warm up clean water in separate pipes that circulate around the building.

Systems like this have been installed in Japan, China, Canada and parts of Northern Europe - and they’re having an impact.

One of Mueller’s systems went into a building in Vancouver and lowered the building’s energy consumption by 75%.

Mueller: “We’re operating at 600% efficiency so every dollar we spend recovering the heat out of the sewer we get 6$ worth of heat out.”

His company’s sales are projected to jump from 3 million this year to 50 million next year.

But wastewater energy systems won’t work on all buildings.

It can be tricky to retrofit buildings that don’t already have hot water heat circulating systems.

Jessie Israel with King County says the key is to get developers of new buildings thinking about incorporating this technology early on in the design process – in order to reap big energy savings later.

Israel: “350 billion KWH of energy are lost every year, just flushed down the drain. If we’re smart about how we build cities and how we build communities and how we build buildings. Maybe 50 years from now that will be a much smaller number."

King County will be accepting ideas for wastewater energy capture projects until the 23rd of August.

Copyright 2012 Northwest Public Radio