How storing energy without batteries could be key to N.S. giving up fossil fuels

In a laboratory at the Nova Scotia Community College sit two water tanks bristling with copper wires. They don't necessarily look like a piece of renewable energy technology. But they may nonetheless play a role in reducing one of the province's greatest sources of greenhouse gas emissions. 

In Nova Scotia, as much as 60 per cent of the energy consumption comes from space heating, a figure that rises to 80 per cent when hot water is included. 

As the province looks toward its new target of moving off coal-fired power by 2030, and achieving net-zero by 2050, researchers say storing heat — including through some of the thermal energy storage options being investigated at NSCC — could help bring about that transition. 

"If you can find a way to store heat for when you need it later, and if that happens to be more affordable than installing a bunch of batteries to store electricity, which it often is, then that can give you a lower-cost solution to storing your energy," said Wayne Groszko, applied energy research scientist at the Nova Scotia Community College.

"So thermal energy storage, we see as part of a future in which all, or most, of our electricity on the grid is from renewable sources."

Solving the variability challenge

In the future, an increasing proportion of energy around the world, including in Nova Scotia, is likely to come from wind and solar. 

But a central challenge with these technologies is their variability, said Groszko. "Basically, that doesn't necessarily correspond with when you need that energy. And so having some way to store the energy when it's plentiful, and use it later, is very key."

Technology like lithium ion batteries are one answer, but are relatively expensive, have a limited lifespan and use raw materials, such as lithium and cobalt, that exist in limited quantities.

Given that much of the ultimate use of energy in Nova Scotia is to generate heat anyway, storing that energy as heat is an affordable alternative, Groszko said.

One example is a hot water tank — a technology most people already have in their homes. Such a tank could be superheated on a windy day to store that energy. Then, when the wind drops, the tank's heaters could be turned off, and the energy released as hot water or space heating. 

In Groszko's lab, the team is investigating how this can be accomplished with smart controllers, which can switch the heater on and off remotely in response to demand on the grid, while still leaving enough hot water available to take a hot shower, for example.

"That's the kind of the experiments we're working on, is how to integrate this relatively simple technology into people's lives," said Groszko.

"The idea is you shouldn't notice it, you should just use your hot water as usual. But in the background, it's saving demand on the grid when it's needed, and then putting it back in later."

This would also reduce costs for households, when coupled with time-of-day electricity rates. 

Another option involves using phase-change materials, which store energy by, for instance, moving from liquid to solid. A 2020 report by the International Renewable Energy Agency estimated the global market for thermal energy storage like phase-change materials could triple by 2030. 

Several companies in the Maritimes are investigating the possibility of integrating phase-change materials into heat sources to allow more integration of renewables. 

One is Fredericton-based Stash Energy. Dan Curwin, director of business development, said they've developed heat pumps with phase-change material storage built in, to store energy from renewable sources like hydro when it's plentiful, such as overnight, and discharge it in the morning when demand is high, to be stored up again from renewables like solar during the day. 

This can help with the integration of renewables and with greater adoption of electric heat pumps, which are the most efficient heating option but risk overburdening the grid. 

Curwin said the company has partnerships with efficiency agencies across Atlantic Canada and New England, as well as housing authorities such as Housing Nova Scotia that recognize the particular burden posed by heating costs. 

"With batteries, or with electric vehicles, it's generally higher-income individuals who are able, at least right now, to purchase those systems," Curwin said. "But space heating and cooling is a huge piece of people's monthly bills. And we do want to make sure that we can get the system to a point where it's available for everyone, not just for the people who can purchase it because they want to, essentially."

Daniel Larsen, the company's co-founder, said now that they've developed a system that can efficiently heat and cool while allowing access to affordable energy through storage, the next step is to work with partner agencies to make the system attainable to households. 

"Access to renewable energy cannot be just for people who have money. So it's absolutely about making a product that's accessible to everyone," said Larsen.

The company hopes to have the units available in Nova Scotia through a larger demonstration project by next fall. 

Sean Kelly, director of clean energy for the Nova Scotia environmental charity Clean Foundation, said the need to improve access to affordable energy is particularly high in Nova Scotia. The province has some of the highest rates of energy poverty — which some researchers define as households spending more than six per cent of their income on energy for heat and other purposes — in the country, according to the Canadian Urban Sustainability Practitioners. 

"We have to deal with energy poverty at the same time as climate action, because they're both quite intertwined," said Kelly.

Technologies and policies that allow more households to be part of the energy transition, while also lowering energy costs, are an important part of taking action on climate change, Kelly said. 

"Climate change doesn't sit just with the environment movement, it's something we all have to be involved in," Kelly said.

"These sorts of clean energy initiatives will benefit those living on lower incomes more than almost anyone else. I mean, who needs lower energy [costs] more than someone living on lower income?"

Back in the NSCC lab, Groszko said some of the technology his lab is investigating is currently available through utilities and wholesalers, but is not yet available at the consumer level. 

In the future, though, he said by allowing more households to participate in the transition to renewable energy, thermal storage options could tap into Nova Scotians' willingness to help with that transition.

"Over the past 10 years, Nova Scotians have improved their energy efficiency dramatically, and I think there's a certain amount of pride about that," he said. "It's something that I think a fair number of people would be interested in continuing to move in the right direction."