Project Update - July 2023

On July 10, 2023, the Ontario Ministry of Energy (MoE) released Powering Ontario’s Growth – an integrated strategy detailing the province’s plan to meet energy demands for 2030 and beyond. Actions in the report include a request for the Independent Electricity System Operator (IESO) to assess the proposed Marmora Clean Energy Hub Project to improve Ontario’s grid efficiency. Please access the report for more details.

Location and territory acknowledgement

Map of Marmora Pumped Storage location

Located halfway between Toronto and Ottawa, the proposed project lies within two historical First Nation Treaties; the northern portion lies in Treaty 27/Treaty 27 ¼, and the southern portion lies in the Crawford Purchase. Both Treaties and the Crawford Purchase are the traditional and Treaty territory of Alderville First Nation and territory covered by the Williams Treaties First Nations Settlement Agreement. Ontario Power Generation and Northland Power Inc. acknowledge and respect Indigenous Nations and communities whose practices and spiritualities are tied to the land and water, and continue to develop in relation to the territory and its other inhabitants today.

A battery made from nature

The proposed Marmora Clean Energy Hub Project is looking to convert Marmora’s former open-pit iron ore mine into a 400-MW clean energy asset – a first-of-its-kind project for Canada. The inactive site has the potential to become a source of clean energy that not only creates the electricity we need, but serves as an economic engine supporting skills training, tourism and the local business community.

Did you know? The mine pit, which reaches a depth of more than 200 metres below ground level, was created for mining operations in the mid-20th century. Since mining operations ceased in the late 1970s, the pit has filled with a combination of rain and ground water. The proposed Marmora Project would recirculate this water between two reservoirs to generate electricity using a closed-loop design. This approach avoids drawing water from nearby waterways and lakes, eliminating impacts to fisheries and waterway levels.

Artistic rendering of proposed Marmora Clean Energy Hub Project
Artistic rendering of proposed Marmora Clean Energy Hub Project

If constructed, the project would interconnect with major transmission infrastructure in eastern Ontario fewer than 8 kilometres away, allowing flexible east-west bi-directional power flow. This allows for adequate load capacity, and is easily accessible for workers, equipment and supplies.

Unlike other energy technologies requiring upgrades or replacement every few decades, the proposed Marmora Clean Energy Hub Project has an operational life span of more than 90 years. With a low operating cost and the ability to supply electricity on-demand, this GHG-free facility can help Ontario meet future capacity needs and achieve its climate change goal of being net-zero by 2050.

Surrounding lands on the Marmora property could be developed for community recreational use and tourism throughout the year. The creation of naturalized areas for public use could be explored as a potential conservation opportunity in the future.

Work is currently underway to advance this clean energy project in pursuit of a cleaner, more flexible electricity grid for Ontarians.

 Project overview

We’re planning for innovation with real impact

Hydroelectric pumped storage uses the pumping and release of water between two reservoirs at different elevations to store water and generate electricity.

A schematic showing how the Marmora pumped storage system will work
Marmora pumped storage system closed-loop Design

When demand for electricity is low, a pumped storage facility can use low-cost energy to pump water from the lower reservoir to the upper reservoir for storage. When demand for electricity is high, that same facility can release water from the upper reservoir through a powerhouse to drive turbines and generate electricity.

The Marmora Project is proposing a closed-loop cycle design that recirculates the same water between two reservoirs. If constructed, the facility will offer power on demand thanks to its ability to ‘time shift’ generation by delivering power when it’s needed most by our system (and maximize ratepayers’ return in the process).

Additional details regarding design and function will become available as the project progresses.

Frequently asked questions

Pumped storage produces electricity during high-demand periods by using the flow of water from an upper reservoir to drive turbines as the water passes down into a lower reservoir. When demand is low and the province has excess (surplus) electricity that would otherwise be sold off at a discount to other jurisdictions, the pumped storage facility uses the surplus power to pump water from the lower reservoir back into the upper reservoir. The water is then stored in the upper reservoir until the system needs more electricity.

Depending on the size of the reservoirs and electricity demand, this cycle may be repeated several times a day to varying degrees.

The proposed Marmora Project would have an average capacity of 400 MW for up to five hours. That’s enough to power approximately 400,000 households.

Should the project obtain approval to proceed, an environmental assessment would precede a construction period of approximately five years.

Yes, OPG has operated Ontario’s only pumped storage facility since 1957. This six-unit, 175-MW pump-generator is part of the Sir Adam Beck Complex in Niagara Region.

Pumped storage shares many of the same advantages with conventional hydroelectric generation:

  • Longer lifespan than other types of generation assets (90+ years).
  • A made-in-Ontario solution creating long lasting economic, environmental, and social benefits including those for Indigenous communities.
  • Significantly lower operating costs than other technologies once initial capital is recovered.
  • Lower lifecycle costs and construction related environmental impacts than other technologies that require replacement every 20-30 years.

A closed-loop design describes a type of hydroelectric pumped storage facility that recirculates (or ‘recycles’) the same water to generate clean, renewable electricity. The proposed Marmora Project, which features a closed-loop design, avoids drawing water from nearby waterways and lakes, and eliminates on-going impacts to fisheries and waterways. The ‘head’ - or vertical distance from the top reservoir water level to the bottom reservoir water level - varies as the water moves between the two reservoirs.

Some hydroelectric pumped storage facilities feature an “open loop” design which draws water from lakes, rivers or bays with the potential to impact fisheries or increase turbidity (suspended matter that makes water look cloudy or dirty) due to the volumes of water being drawn or returned to the waterway.

In the coming years, more clean energy resources will be required to meet Ontario’s growing electricity demands and replace existing assets that are being retired or entering long-term refurbishment outages. As demand continues to grow through the latter part of the decade, the Marmora Project will help Ontario meet its near-term generation capacity needs which are forecasted to increase up to an additional 15,000 MW by 2035.

This proposed clean energy facility will also support the growth in electrification across the province, and help Ontario reach its climate change goal of being net zero by 2050.

OPG and Northland Power are committed to working with the local community, Indigenous communities and stakeholder groups throughout the lifecycle of this potential project. We have an established engagement framework that will help to ensure that a pro-active, accessible and transparent approach is taken to public outreach, and allows for the growth of positive relationships that help inform the project if, and when, it proceeds.

From the outset of each project, OPG and Northland Power encourage local and Indigenous employment and involvement and consideration for supply chain opportunities that may exist on the Project. As we move further through the planning process, we will work with the project constructor to identify different trade and other business contracts that are required.

The project will operate within all applicable noise by-laws during construction and operation.

The safety of our employees, the public and the communities where we operate is our greatest priority. The planning and potential future operation of the proposed Marmora Project is governed by a multi-tiered regulatory framework involving federal, provincial and municipal governance. OPG and Northland Power are committed to this framework to ensure all safety requirements are met throughout the life of the project. Public engagement will also remain a focus of the project as it moves through the Federal Impact Assessment and Provincial Environmental Assessment processes. These are important planning and decision-making tools supporting a range of environmental, health, economic and social considerations. If you have questions or require more information, please contact us.

This is a joint venture between Ontario Power Generation (OPG) and Northland Power Inc. (NPI).

OPG and NPI anticipate further direction around April 2023 regarding whether the project will progress to IESO Gate 3 (final stage). A final decision is not expected until late 2024 at the earliest, pending approvals. The earliest construction could start would be 2025.


Please drop in to learn more about the proposed Marmora Clean Energy Hub Project and speak with members of the project team.

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