Ontario’s electricity grid is among the cleanest on the continent, and major manufacturers are making rapid progress in bringing electric cars, buses, and even some trucks onto the market. But a number of challenges remain in the fight to reduce greenhouse-gas emissions. One of the biggest relates to an issue that may seem banal: how to heat and cool homes and workplaces without relying on fossil fuels such as natural gas or heating oil.
Sidewalk Labs, the Google-backed company that wants to build a “smart city” district on part of Toronto’s waterfront, aims to tackle the problem by building a “district energy” system as part of its so-called Quayside plan. So far, so normal: plenty of large developments — universities, private mixed-use residential and commercial sites — rely on district energy. But, traditionally, that has meant pushing high-temperature steam or hot water through heavily insulated pipes and then using it to heat buildings directly. Toronto’s Enwave, a district-cooling utility, takes cold water from deep in Lake Ontario and uses it to provide cooling for towers in the city’s core.
It’s established, tested technology, but it comes with drawbacks: even insulated pipes lose a lot of their energy to the ground they’re buried in (hot pipes cool down; cold pipes warm up), and it has traditionally relied on gas-fired boilers. So Sidewalk wants to try something different: a more distributed model of smaller plants.
“We’re trying to create a pathway to climate-positive neighbourhoods,” says Charlotte Matthews, director of sustainability at Sidewalk Labs.
“In Toronto, specifically,” she says, “the electricity grid is so green — 90 per cent of the power is coming from carbon-free sources — that it means 87 per cent of GHG emissions associated with buildings in Toronto comes from the burning of natural gas for heating and hot water.”
The company’s approach would involve pipes filled with water, but not at the extreme temperatures of traditional systems. The water could be warmer or cooler but, in general, it would be much closer to the temperature of the ground the pipes run through — the “ambient” in “ambient loop.” The water in the pipes wouldn’t take care of the heating or cooling: that job would be done by heat pumps.
In principle, heat pumps aren’t much different from your refrigerator’s compressor, which moves heat from the inside of the fridge to the outside, making your food cooler. Heat pumps, though, can be reversed, bringing heat inside Canadian homes and businesses when it’s needed. They’ve been used in buildings for decades, providing heating, cooling, and hot water. The ambient-loop system effectively gives the heat pumps a predictable, utility-delivered stream of water that they can either pull heat out of (for heating) or dump heat into (for cooling).
Because it doesn’t rely on heavy insulation or high temperatures, an ambient-loop network could prove more affordable than traditional district energy. It could also be easily expanded or modified in the future as residents and businesses change — a key concern, given the Quayside plan’s emphasis on flexible, changing uses for buildings. But one of its most compelling features, and the one that has Sidewalk Labs interested, is that it may allow for the creation of a two-way exchange between various customers in the network, meaning that the waste heat generated by the cooling of a data centre, for example, could be used to heat an office building.
“Quite often, across our climate regions, we’ve got buildings that require cooling in both hot and cold seasons, and that offers us the opportunity to do effective energy recovery,” says Vladimir Mikler, a principal at Integral Group and an expert in district-energy systems.
In theory, it’s a zero-carbon answer to the question of how cities of the future will be able to sustainably heat and cool buildings. But some details remain unclear. Numerous jurisdictions are looking at different ways of implementing ambient-loop systems, and Sidewalk Labs’ design is, for now, just one idea among many. Mikler and Integral are working on one proposal, which would see a backup water supply in Vancouver intended for firefighting used as an ambient-loop system. That would save money by using pipes that are already in the ground, without threatening their availability for firefighting when needed.
Saving money is an obvious goal in Toronto as well, given the cost of living.
“In addition to being climate positive, we also want to keep Sidewalk Toronto affordable, and that means keeping costs to just about what they are today,” Matthews says.
Mikler notes, however, that it can be difficult to assess the costs and benefits of new green technologies fairly.
“We’re working in an environment where everyone is comparing things to the business-as-usual scenario, which is typically a system that’s based on fossil fuels, and systems that paid for themselves a long time ago,” he says. “Now you’re trying to build a brand-new infrastructure and fuel-switching from natural gas to electricity.”
Although the ambient-loop system offers efficiencies and environmental benefits, the fact that it would require brand-new infrastructure and a switch from (cheap) gas to (more expensive) electricity may make a daunting proposition.
But it would be worthwhile to make it work: we badly need zero-carbon solutions for the 21st century. Between heating, cooling, and hot-water demand, buildings are responsible for 20 per cent of Ontario’s GHG emissions. That number will need to start coming down rapidly in coming years — an experiment on Toronto’s waterfront may help make that possible. Certainly, Sidewalk hopes that any resulting success wouldn’t be confined to the Quayside area.
“I would very much hope that as commercial developments are built in the area and other development occurs that they would also be served with similar thermal grid systems,” Matthews says. “No solution that just serves a single neighbourhood is a really optimal solution.”
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