N.S. grid operator insists natural gas power plants cannot be replaced with batteries

Nova Scotia is heading toward a 1,700-megawatt problem, and despite public resistance, the energy grid operator maintains that new gas-powered generating stations are an essential part of the solution.

Last week, Pictou County council asked the province to pause the pursuit of two natural gas power plants and consider alternatives. The warden and councillors said they’d received a deluge of feedback from local residents worried about potential environmental and health risks.

Premier Tim Houston did not dismiss the pushback — he said concerns are natural and his government is trying to alleviate them by providing information about the plants — but he did dismiss the request to pause and reconsider.

Houston said the Independent Energy System Operator (IESO), the newly formed entity that’s taking over management of the province’s power grid, knows best.

“I have great confidence in the process they followed and … in the decision they made,” he told reporters after a cabinet meeting last week.

Here’s how the IESO explains that decision.

The province is approaching a statutory deadline to stop generating electricity from coal, and at the same time, electricity demand is increasing.

Chris Milligan, the IESO’s vice-president of planning and procurement, said when you put those things together, models point to a 1,700-megawatt gap on the power grid that will need to be filled by 2030.

That’s a big number when you compare it to the highest demand ever placed on the power grid, which was 2,459 megawatts, Milligan said. That happened during a cold snap this January.

The grid operator plans to address the gap with renewables (primarily onshore wind energy) and demand-side management (technologies and programs that reduce electricity use), and to balance the intermittency of renewables, batteries and fast-acting gas plants.

Nova Scotia Power built two large-scale battery facilities last year and has a third nearing completion, and the IESO plans to procure more battery storage in the near future. 

Critics of the gas plants — also known as peaker plants because they’re predominantly turned on in times of peak energy demand — say batteries alone can do the job. But Milligan said batteries have a problem of diminishing returns.

“Eventually you won’t be able to effectively serve that load with energy storage alone,” he said in a recent interview.

According to the IESO’s analysis, batteries and peaker plants are comparable at low capacities: nine megawatts of peaker plant capacity, for instance, can be displaced with 10 megawatts of battery capacity.

But a larger gap emerges as capacity increases. The IESO has found that it would take 1,000 megawatts of battery storage to replace 240 megawatts from a peaker plant.

Milligan said the analysis dates back to 2019 but has been reassessed over the years and still holds true.

“We continue to find that the 300 to 600 megawatts [of fast-acting gas power] is needed,” he said.

Milligan said another shortcoming of batteries is the lead time needed to charge them, and their limited usefulness. Large-scale batteries typically have a four- to 12-hour duration, and Milligan said periods of peak demand or flagging wind inputs can last days.

IESO officials have previously estimated that each 300-megawatt peaker plant could cost about $800 million, but the exact price tag is not yet known, and therefore the impact on power rates is also still unclear.

Milligan said affordability is a priority for the grid operator, along with reliability and meeting the province’s decarbonization goals.

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