Is this a silly idea?

[patp]

Talking to the guys installing our drains and sewers we got on to discussing heat pumps. It then occurred to me that there was a long trench with, eventually, pipes full of warm water running from the new bungalow to the junction with the road. It is, in our case, a distance of about 50 or 60 metres. Would it be possible to use these sewer and drain pipe runs to heat underground heating pipes?

 

Then I started to think about all the sewer pipes that crisscross our land that could be used as a source of heat. OH and I discussed turbines in the sewer system but decided that would be a step too far given all the stuff people flush down BUT what about a turbine on the "clean" side of sewage treatment plants, just where it enters the river/sea?

 

Someone somewhere has thought about putting turbines into their incoming water supply apparently.

[Simplysimon]

i've always thought a turbine outside everyones house in the water main would be a good idea

[TonyT]

You could probably generate enough to light a small led lamp similar to the standby LED on the tv

 

https://www.instructables.com/downspout-generator/

[Radian]

23 minutes ago, Simplysimon said:

i've always thought a turbine outside everyones house in the water main would be a good idea

Water companies have to pay for the energy that pressurizes the water main. I don't think they'd be too chuffed. Great for those who go unmetered though ?

Extracting the kinetic energy from the waste water as it leaves the house would create a tiny win with no losers except for the messiness issues already mentioned ?

[jamieled]

Some water companies are using in line turbines on raw water supply pipes (scottish water for one). Helps if you have a hilly supply area. Doing it on the clean water side is problematic due to both pressure requirements and the need for cleanliness.

 

Most waste water treatment plants are close to either a river or coastal water body in order to avoid pumping sewerage back to the plant so there'd be next to no head for turbine to work.

[Iceverge]

1 hour ago, patp said:

Would it be possible to use these sewer and drain pipe runs to heat underground heating pipes?

 

 

Yes but.....

 

Say in theory if you ran a COP of 3 (3 units of heat extracted from the waste, 1 energy put in to make up the losses) on your DHW heat pump you should be able to return the waste water to the mains at much the same temperature as the mains water in. 

 

However if you were to add space heating to that you could well end up freezing the out going sewerage with the heat pump. Bugger. 

 

Even if sewerage is cooled significantly it will start to have processing and flowing issues.  

 

If you want to waste less heat from water just put a water heat recovery on the bath and shower wastes. 

 

 

Alternatively shower in the bathtub with the plug in and leave the water there until it has cooled to room temperature. You could get 2/3 of your energy back as heat to the room this way. V cheap win. 

[SteamyTea]

Would you not just freeze the water in any pipes.

 

I think it is illegal to run a turbine from a tap.