HUBER Solution for Heat Recovery from Sewers (ThermWin®)
Beneath our streets we find an energy source that we have so far ignored. Municipal sewage contains thermal energy; its temperature is generally between 10 and 20 °C, all year round. This temperature permits economical operation of heat pumps for the heating of nearby buildings (e.g. nursery homes, schools, gymnasiums, swimming pools). The only challenge is how best to extract heat from sewage.
Manufacturers are busily developing sewer pipes with integrated heat exchangers; but then we would need new sewer construction. There are special heat exchangers that can be installed on the inverts of existing sewers; but this is only possible in large diameter sewers, and heat transfer is impeded by fouling layers on the surface of such heat exchangers; not only is installation of such heat exchangers difficult and expensive, but also their service and maintenance.
We have developed our own HUBER Solution ThermWin® for heat recovery from sewage:
We withdraw sewage from the sewer, screen it, pump it through above-ground Heat Exchangers, and then return it back into the sewer. Because we screen and pump the sewage, we can use compact and cost-effective heat exchangers, wherein we generate a well-defined and turbulent flow for efficient heat transfer. For screening we use a HUBER Vertical Screw Screen ROTAMAT® Pumping Stations Screen RoK 4 that is compact and lifts the screening through its vertical auger. Returned sewage flushed the lifted screenings over a chute back into the sewer.
Advantages of the HUBER Solution ThermWin®
- Efficient use of renewable and sustainable energy
- Unlimited availability, secure supply
- Local and free, decentralized heat source
- Cost-effective from a dry weather flow of around 10 L/s
- Negligible effect on wastewater treatment (sewage cooling by 1 – 2 °C only)
- Independence from sewer size
- Use of compact, efficient and cost-effective heat exchangers
- Heat exchangers above ground (easy access for installation and maintenance)
- Little construction work (narrow manhole beside sewer)
- Minimal interference of existing sewers (only drilling of two holes)