energy generated by big wastewater plants is methane from microbial activity. also waste water plant can not remove a lot of stuff like medicine, hormones...
you can construct wastewater tank with integrated coil connected to heat pump. so you can take all heat back. if you have house with integrated waste water treatment, this should be no brainer. houses with existing heat pumps can "just add another heat exchanger circuit"
but i do not personally like heatpumps because working fluid can be in orders of 10 000 times more harmful to greenhouse effect than co2. and compressors using CO2 as a working fluid are rare.
heatexchangers connected to vertical wastewater pipe are showed in tradeshows. but i do not understand how that makes sense price wise. im not sure they recover as much heat as advertised.
You seem to have concluded energy use for hot water cannot go lower by excluding any approach that would lower it, not because it's physically impossible, but simply because such technology isn't being used.
energy generated by big wastewater plants is methane from microbial activity. also waste water plant can not remove a lot of stuff like medicine, hormones...
you can construct wastewater tank with integrated coil connected to heat pump. so you can take all heat back. if you have house with integrated waste water treatment, this should be no brainer. houses with existing heat pumps can "just add another heat exchanger circuit"
but i do not personally like heatpumps because working fluid can be in orders of 10 000 times more harmful to greenhouse effect than co2. and compressors using CO2 as a working fluid are rare.
heatexchangers connected to vertical wastewater pipe are showed in tradeshows. but i do not understand how that makes sense price wise. im not sure they recover as much heat as advertised.