Wastewater Europe

What lies beneath: Harnessing the potential of heat from sewage

Thursday, 25 January 2024

In a bid to revolutionise home heating and reduce environmental impact, water companies are turning to an unconventional source – sewage. Sewage heat recovery (SHR) is gaining momentum as a reliable and renewable energy solution. We delve into the innovative world of SHR and understand why water companies are investing in this forward-thinking approach.

Untapped source of heat

Sewage water, often dismissed as waste, boasts a hidden asset – a constant and stable temperature. This inherent quality makes it an ideal, yet largely untapped, source of renewable heat. 

The key steps in SHR involve heat exchangers, electrical heat pumps and a distribution system. The process begins at a sewage treatment plant where wastewater from various sources undergoes treatment.

Heat exchangers are employed to transfer thermal energy from the sewage water to a separate fluid, such as water or refrigerant. This transfer occurs without direct contact between the sewage water and the secondary fluid, ensuring hygienic and efficient heat extraction.

Once the thermal energy is extracted from the sewage water, it typically needs to be further elevated to reach temperatures suitable for residential heating. Electrical heat pumps play a crucial role in this stage. They receive the moderately heated fluid from the heat exchangers and use electricity to further boost its temperature. Recovered heat is at a level that can effectively warm homes during colder periods.

The now-elevated and heated fluid needs a system for efficient distribution to homes or buildings. A distribution system, often a network of pipes, is employed to transport the heated fluid from the sewage heat recovery facility to residential areas. This infrastructure ensures that the warmth derived from sewage is effectively delivered to end-users.


Stable temperatures of sewage water

One of the key advantages of sewage heat recovery is the relatively stable temperature of sewage water throughout the year. Unlike external weather conditions, sewage water maintains a consistent temperature, providing a reliable and steady source of heat.

By harnessing the thermal energy from sewage, the process reduces the reliance on traditional heating methods powered by fossil fuels. This contributes to a reduction in the overall carbon footprint associated with residential heating, aligning with sustainable and eco-friendly energy practices.


Trailblazing SHR in Vancouver 

Vancouver, Canada, has emerged as a trailblazer in sustainable energy practices by tapping into the potential of SHR. Approximately 6,210 apartments in False Creek, an area of the city, are now warmed by the innovative use of heat from wastewater, making sewage heat the primary contributor to renewable energy sources for heating.

The Seven35 Condo residential estate in the city also successfully reduced its greenhouse gas (GHG) emissions by an impressive 150 tonnes using SHR.  A SHARC wastewater heat recovery system was used, which now recovers 80 per cent of wasted energy.
In an article on the project from the BBC, Derek Pope, the  manager of Neighbourhood Energy for the city of Vancouver, emphasizes the transformative impact of SHR. Underneath the city's streets, a network of sewage systems exudes heat. The process involves strategically placed energy centres, equipped with heat pumps that cool down warm sewage before it reaches treatment plants.

By concentrating and elevating the temperature of the extracted heat, scalding hot water is produced, reaching up to 80°C. Pope says the system operates with remarkable efficiency, achieving over 300 per cent efficiency in converting electricity into thermal energy.