sewageENERGYrecovery - Performance comparison of different wastewater heat recovery systems for renewable heat generation

Starting point / motivation

The relative importance of energy consumption for water heating is increasing compared to heating energy consumption. In energy-efficient new residential buildings, the energy consumption for hot water preparation and for heating is of roughly the same order of magnitude. The hot water produced is usually discharged into the sewer, although there is considerable heat potential available directly at the building site.

It is therefore important to utilise the energy content of wastewater where it is highest, i.e. directly in or near the building. Some innovative manufacturers have responded to this problem and developed solution concepts that use the heat stored in wastewater to generate hot water again or to minimise the external energy required to provide hot water and increase energy efficiency.

Contents and goals

The aim of the sewageENERGYrecovery project is to independently test the performance and efficiency of three different wastewater heat recovery systems in actual operation by analysing measurement data. The analysed systems will be evaluated regarding their optimal application in buildings. The results will be incorporated into a position paper that describes a way to increase the use of wastewater heat recovery systems in buildings (e.g. via subsidies up to possible specifications in future building regulations).

Methods

The following systems are analysed by measurements:

1. decentralised shower water heat recovery: waste heat from the shower water is separated and added to the incoming cold water, preheating it.
2. centralised heat recovery: all waste water (including black water) flows into a heat exchanger, which serves as a heat source for a heat pump.
3. central grey water recycling plant in the building: grey water (waste water from showers, washbasins and kitchen sinks) is treated biologically and mechanically, heat is extracted and heats the fresh water. Purified cold water can be used for irrigation, toilet flushing and cooling.

Expected results

The contribution that could be achieved through the widespread use of wastewater heat recovery is relevant in terms of climate policy due to the now increased relative importance of energy consumption for hot water. Depending on the system used, not only is energy consumption minimised, but the burden on the municipal infrastructure is also reduced by recycling wastewater locally directly at the building site.

Project management

Schöberl & Pöll GmbH

Project or cooperation partners

• Passivhaus Institut GmbH Deutschland
• hacon GmbH

Schöberl & Pöll GmbH
Lassallestraße 2/6-8
A-1020 Vienna
Tel.: +43 (1) 726 45 66
E-mail: office@schoeberlpoell.at
Web: www.schoeberlpoell.at