Sewers Hold Waste Heat Ready For Recovery
Harvesting waste heat has grown in popularity in various parts of the world, but most of that comes from air heating, or heat released from machinery of various kinds. International Wastewater Systems of British Columbia has figured out another good source of heat that can be captured: sewer water.
We published one of their videos a few days ago at sustainablog; take a look at that post below, and then let us know what you think.
Waste Heat Recovery… From The Sewer? Canadian Firm Harvests Wasted Hot Water [Video]
We’ve discussed all sort of energy harvesting possibilities from sewage, but nearly all of those were tied to the waste material floating in that water. It turns out the water itself is also a carrier of energy, in the form of heat. British Columbia-based International Wastewater Systems has figured out a technology for waste heat recovery from sewers that can save municipalities and other setting with lots of people quite a bit of money on their energy spending… and make a nice dent in greenhouse gas emissions.
The general premise is pretty simple: we all send hot water – from our showers, dishwashers, sinks, etc – down the drain. That’s energy, and by using a heat exchange-based system they call The Sewage SHARC, IWS provides a means to recover that energy.
The video above goes into much more detail on how this works, including the kinds of cost savings it can produce. Yes, this is a promo video, with lots of promo-speak, but the underlying concept and the technology the company’s built are just fascinating. I know a number of European countries have done great work with waste heat recovery at a municipal scale, but, even in those cases, I’m not sure that heat from the sewers is part of the equation.
This video’s a little longer than what we normally post, but well worth your time. Once you finish it, please share your thoughts with us in the comments.
Featured photo credit: photowind via Shutterstock
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Most heat you send down the drain with showering can be recovered in your own house. My HR-drainpipe was €400 and recovers 4-10 kW of free power that would otherwise be wasted.
But for cases where draining hot water and taking in cold water are at different moments, using this resource at municipal level is of course the next best thing 🙂
Yes a HR=drainpipe should be mandatory for every new house, every retrofit.
Have one in my place. 🙂
I have not heard of HR-drainpipe. I Googled and and can’t seem to find any information. Is this kind of thing available in the US?
Heat recovery drain pipe
http://www.homedepot.com/p/Power-Pipe-3-in-x-48-in-Drain-Water-Heat-Recovery-Unit-R3-48/203456041
Though i’d love any suggestions on better ones (or insight on choosing, installing, etc.)
Tips on choosing: less cold water content is better, since it will heat faster and has less opportunity for bacteria growth (though the risk with copper is minimal anyway).
More heat exchanging surface area is usually better, so longer or wider pipes are better.
If the shower is on the same level as the sewer, you can’t use a vertical drainpipe, but horizontal drains exist too. While less efficient, it’s still better than wasting the power 🙂
Installing: make sure it is absolutely vertical so the waste water will form a uniform film on the side of the drain. You should create the entrance with two corners so the water will ‘vortex’ in.
This is the one I have (WTW=heat recovery):
https://www.warmteservice.nl/Huis-%26-Gereedschap/Warmteterugwinunit/Douche-WTW/Technea-douchepijp-WTW-RV21-V-3-rendement-65-4%25-bij-flow-9-2L-min—drukverlies-0%2C37-bar-lengte-2100mm/p/A0062956
Horizontal ones:
https://www.warmteservice.nl/Huis-%26-Gereedschap/Warmteterugwinunit/Douche-WTW/Easy-Drain-Douchegoot-WTW-zonder-Multi-goot-en-Multi-Aqua-put/p/A0065133
https://www.warmteservice.nl/Huis-%26-Gereedschap/Warmteterugwinunit/Douche-WTW/Technea-douchebak-WTW-84cm%C3%98-rechtstreeks-te-plaatsen-onder-douchebak-van-90×90/p/A0048246
So it seems to me that you would have to use some really low flow heads in order to not have a pressure restriction on the cold water (as those tubes are pretty thin…)
Also, wouldn’t these require tearing up the tile in the bottom of the shower? (What other than a shower would you use one for?)
And with a second floor shower, wouldn’t you still need a horizontal one since the floor is only 12 ish inches thick?
Thank you for the info!!!
When the shower is on the first floor, there is a vertical PVC pipe that transports the waste to the first floor. The HR-pipe replaces this PVC pipe.
My shower is on the floor above a toilet; the HR-pipe for the shower is in a corner in the toilet. Another possibility would have been in a corner in the staircase for example.
If you can reach the vertical pipe without tearing up the tiles, you can install a HR pipe without bathroom renovation 🙂
I’m not sure what pressure and flow a normal US shower has; my water supply is a steady 3 bar and 7 liters/minute gets me comfortably wet.
What it is; one large copper pipe`wrapped with a smaller copper pipe, small one has cold water going to hot water tank, large one is used grey water.
As others explained: a drainpipe that pre-heats cold tap water before it enters the heater.
My version consists of two concentric copper pipes, the 50mm inner pipe is the drain and the jacket that is formed by the outer and inner pipe contains the tap water to preheat. There is a bit more to it to ensure a double barrier between sewer and tap water, but that’s the basic idea. Just a low-tech vertical counter-flow heat exchanger.
I’ll add a separate post with some Dutch links in it, with Google Translate I’m sure you can find something similar in the US. The Power-Pipe is already named, from the looks of it, it’s a lot more copper and a lot more expensive.
Personally I think IWS has hit the mother lode. Heat from building effluent is constantly available. Easily recovered heat energy with these new SHARC and Piranha systems. Their existing installations have proven the efficiencies and ROI. Every building should have such a system, especially hospitals, prisons, colleges for example. Also I like that the IP is secured by patents or applications. Good luck to them and thanks for helping reduce carbon emissions.