This novel waste-to-energy system was originally conceived and built for the 2010 Vancouver Olympics, during which time nine blocks of flats were constructed on brownfield land in the centre of the city to house visiting athletes, and then converted to high-end housing.

Derek Pope, Associate Director of the City of Vancouver Neighbourhood Energy Utility, says: ‘The city wanted to deliver a sustainable games, and a sustainable Olympic village. In Vancouver we inventory where our greenhouse gas emissions are coming from and buildings are responsible for more than 50% of the city’s emissions; we commonly heat with natural gas. The city wanted to create a more sustainable path for the future.’

Situated only a few blocks from the Olympic village buildings was the False Creek sewage pumping station, one of 26 such facilities scattered around the city that send wastewater, at a volume of hundreds of litres/s, onward for treatment. There, the False Creek Neighbourhood Energy Utility contracted Trane to install a 3.2 MW Tecsier heat pump, which received a diverted stream of the wastewater, and extracted the heat energy which is then supplied to a network that has since grown to service 46 buildings.

Pope states: ‘We were the first city in North America to extract waste heat from raw sewage. The big innovation here is that wastewater treatment plants tend to be on the outskirts of cities. So, if you collect the heat from the treatment plant effluent, you have to transport it all back in to service the city. We are accessing waste heat with our closest connected building across the street, which brings major benefits to economy and efficiency.’

Although flows of wastewater vary by time of day – with a peak in the morning – and by season, its temperature generally does not change, remaining on average 20°C in winter and 22°C in summer. This is because, all year round, residents generate domestic hot water for heating, showers and washing dishes, and that thermal energy remains in the water as it flows out of the flats, through the sewer, and into the False Creek heat pump at 110 l/s. (That uniform temperature helps improve the efficiency of the heat transfer process year-round.)

There is also a nice synergy between heating demand and sewage flows, Pope observes. ‘What is the first thing that people do when they wake up? They have a shower, wash up, and we see a big spike in heating demand on the system as a result. Those same activities also result in an increased flow of sewage giving us more waste heat to send back to the neighbourhood.’

How does a sewage heat recovery system work?    
Having reached the facility’s heat pump’s corrosion-resistant, cupronickel tubes, heat from the sewage conducts through the metal wall to the shell side of the integral heat exchanger, vapourising a refrigerant. When the gas is compressed, the gas temperature shoots way up, travels to a second heat exchanger, and conducts its heat through another metal wall to warm 50–55°C service water. Having done so, the refrigerant condenses and returns the way it came. Meanwhile, the service water, now 65–80°C, flows to the buildings in a closed loop, where it dumps the heat via another heat exchanger, then returns to be heated again. The system’s annual heat loss is said to be only 2–3%.

The utility measures the system performance by comparing heat output to electricity input (for the compressor), and over the past decade the heat pump has had a coefficient of performance of 3.2. In other words, for every unit of electricity, it generates 3.2 times as much heat. Having removed about 5°C from the sewage, the system generated about 23,000 MWh in 2022 and 20,000 MWh in 2023.

Last year’s performance was somewhat reduced because of planned downtime to install two new 90 l/s York heat pumps, installed by Johnson Controls, which are expected to add another 6.6 MW capacity, to meet expanding demand when they come online by the end of October 2024. ‘We expect that they will be more efficient too, with a rated CoP [Coefficient of Performance] of 3.5,’ Pope adds, citing technology improvements in heat pumps over the last 15 years.

Another important upgrade to the plant is the screening system that protects the heat pump from debris, such as wet wipes (or anything else greater than 2.5 mm) that inevitably makes its way into the sewers and could block the heat exchanger tubes if they reached them. The previous travelling screen was located in the wet well – ‘a maintenance headache’, says Pope. The screen has been replaced with a new Sharc system located in the dry part of the facility.

‘One thing that is now starting to come to the forefront of the conversation is that [district heating] systems are really effective at removing a burden on the electricity grid, as we go down an electrification route.’ – Derek Pope, Assistant Director of the City of Vancouver Neighbourhood Energy Utility

How do you plan the district heat network?    
District energy systems do not suit all urban neighbourhoods, Pope contends. ‘It does require the right conditions, and it is important to consider them all. Generally, you are looking for areas of the city at higher density.’ Even better are areas with a mix of building types, to be able to aggregate different energy profiles of buildings and make better use of the system and equipment. District energy helps create economies of scale to do things that are not practical at the building scale. However, the biggest barrier is the upfront cost and investment.

Pope explains that the utility is operated on a commercial model, with rates set to recover capital and operational expenses, plus a modest profit. Discussing the economics of the project, he says: ‘When you’re talking about payback, it depends on what you’re comparing. But any project that recovers its costs while generating low-carbon energy, most people can get behind that.’ Another benefit of the system is that, since sewage is the biggest contributor of heat to the system, it shelters residents from swings in the cost of fuel.

He continues: ‘One thing that is now starting to come to the forefront of the conversation is that these systems are really effective at removing a burden on the electricity grid.’ High efficiency, ability to integrate different energy sources and integrate heat storage, they can act as demand-side management at a neighbourhood scale, he explains, which is of particular interest as municipalities move down an electrification route.

We don’t have to limit ourselves to sewage heat, Pope adds. ‘One emerging source of waste heat we’re interested in is waste heat from data centres. As we move toward smart cities and AI [artificial intelligence], the need for data processing and data centres is growing quickly, and they produce large amounts of waste heat.’

Having been the first of its kind to be installed in North America, False Creek has since been joined by others in greater Vancouver, using raw sewage heat recovery – the latest, a 5MW Lonsdale plant announced in September, is planned for the City of North Vancouver – alongside other district energy schemes in the city.

Over the years, False Creek has attracted visits from municipal officials from all over British Columbia, Canada and the US since it was installed, to show off the potential of the technology. ‘Greater Vancouver has become a leader in low-carbon district heating,’ Pope notes.

• Further reading: ‘Affordable street-by-street solutions present a path for heat decarbonisation.’ Heat pumps have been the leading technology candidate to replace gas-fired boilers in the decarbonisation of UK homes for some time. What are the likely benefits of mass adoption of networked ground source heat pumps?   
• Find out more on the advantages of the refrigerant used with heat pumps that are being installed for one system in London.