By Lucas Bettle 

 

The Canadian Government’s Clean Electricity Regulations have set a goal to reach a net-zero emissions electricity grid by 2050. (Government of Canada, n.d.) Achieving, or coming close to, this target will require a major shift away from fossil fuel power generation toward renewables such as wind and solar. However, such a transition brings about a variety of concerns regarding how grid supply and demand are managed.

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Renewable energy consists of a variety of different sources, including hydroelectric, solar, wind, geothermal, and biomass. Hydroelectric, geothermal, and biomass are all controllable power generation, similar to fossil fuel and nuclear power generation. While hydroelectric capacity may vary over seasons, on a day-to-day basis it is consistent and controllable. (Biserčić, 2021)

Wind and solar power generation is non-controllable, referred to as intermittent or variable generation. Their capacity at any given moment is determined by environmental factors, available wind, and sunlight. This poses a variety of challenges concerning their integration into the electric grid. (Biserčić, 2021)

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Canada’s Current Electricity Generation Landscape

Canada’s total annual electricity generation in 2022 was 637,653 GWh. Hydroelectric generation accounts for more than half at 393,858 GWh. While this means that the majority of Canada’s generation is already from renewable sources, opportunities to increase hydroelectric generation in the future are severely constrained by suitable sites for dam construction. (Natural Resources Canada, 2024)

Fossil fuels and nuclear follow at 112,085 and 82,301 GWh, respectively. Wind and solar account for 37,993 and 4,195 GWh. (Natural Resources Canada, 2024)

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Wind and solar are the primary focuses here, as they are intermittent sources that introduce grid control concerns. They are also rapidly growing. As they continue to take up a larger share of the total generation, these concerns are becoming more pressing.

Canada is a net exporter of electricity. In 2022, Canada exported a net of 51,600 GWh to the US. This accounts for 8% of all electricity generated in Canada that year. Excess capacity from generation stations in Newfoundland and Labrador, New Brunswick, Quebec, Ontario, Manitoba, and British Columbia is sold to the US through a variety of grid connections across different export regions. (Canada Energy Regulator, n.d.)

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The Role of Conventional and Renewable Energy in Baseload and Peak Load Generation

An electric grid has a baseload that is defined as the minimum level of demand over a certain period of time. Satisfying the baseload is conventionally achieved using large generation stations, whether hydroelectric, coal, gas, or nuclear. Facilities designed to supply the baseload can operate near their maximum capacity at all times. (Biserčić, 2021)

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An electric grid will also have a peak load. This is the point of highest demand, which must be considered both on a day-to-day basis and seasonally. Additional power generation serves to meet the peak load, whether entirely separate facilities or additional generation units within the same facilities that provide the baseload. (Biserčić, 2021)

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Variable generation sources, such as wind and solar, face challenges in both of these applications. Their intermittent nature makes them a poor fit for baseload generation. The fact that their output relies on external factors means that output cannot be increased in response to rapid shifts in demand during peak loads. (Biserčić, 2021)

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It is possible to control the output of individual wind and solar generation units. A wind turbine’s output is controlled by adjusting the blade pitch angle, reducing the amount of energy extracted from the wind. When shut down entirely, a braking system holds the rotor in place. For solar panels, the inverter’s charge controller adjusts output electronically. These controls must operate within the limits of the units’ capacity at any given time, reducing their ability to react to significant shifts in demand. (Denholm, 2020)

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Energy Storage for Variable Generation Sources

Energy storage is one potential solution to improve the reliability of wind and solar power. Storing energy can allow wind and solar to operate at maximum output when wind and sunlight are available. The energy is stored and released to the grid when needed. This can close the gap between supply and demand shifts and intermittent power generation.

 

Large batteries, often lithium ion, are a potential option to store energy from variable generation. Ontario’s Independent Electricity System Operator (IESO) has recently procured contracts to install significant battery energy storage scheduled to come into service between 2026 and 2028. The projects are planned to provide 1,880 MW in storage capacity. (IESO, 2024)

Pumped-storage hydroelectricity is another potential method to store energy. Pumps powered by variable generation can fill a reservoir with water from a lower source. When needed, that water can then be used to generate power using a hydroelectric generation station. (Canada Energy Regulator, 2016)

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Ontario has the only application of this method in Canada. Pumps with a capacity of 174 MW fill a 300-hectare reservoir with water from downstream of Niagara Falls, which can then be released to increase output at the existing Sir Adam Beck Hydroelectric Generating Station. (Canada Energy Regulator, 2016)

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Instantaneous Control of Grid Conditions

Electrical grids rely on alternating current, which has a specific frequency. In the US and Canada, that frequency is 60 Hz. Power generation across the grid is controlled to maintain this frequency. Increased loads reduce the frequency, while increased generation increases the frequency. (Denholm, 2020)

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When large power sources fail, the grid frequency starts to decline. The solution to this is to start disconnecting portions of the customer load once it has passed a certain threshold, for example, 59.5 Hz in most of the US. When frequency exceeds a certain limit, such as 60.5 Hz, some generation is disconnected. (Denholm, 2020)

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Control of Inertial Generation Sources

In the case of conventional power generation relying on a physically rotating generator, the frequency is tied to the rotational speed of the generator. Online generators are controlled through a variety of processes, with primary frequency response (PFR) providing automated detection of frequency changes and making output adjustments without operator intervention. Electronic sensors measure frequency and change generator output in real-time. (Denholm, 2020)

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Conventional fossil, nuclear, and hydroelectric generation stations have significant energy stored in their rotating generators. The inertia of these rotating mechanical systems plays an important role in resisting changes in frequency, providing more time for control systems to respond. Renewables such as solar and even wind do not provide this inertia, posing challenges. (Denholm, 2020)

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Control of Variable Generation Sources

When grid supply and demand shift, solar and wind do not have the same physical inertia. While wind power does involve physical rotation, the output is not directly connected to the grid. The frequency of electricity from wind power is highly variable and must be converted to supply the grid. Solar panels generate direct current, which is converted to AC with an inverter. Neither process provides inertia to maintain frequency. (Denholm, 2020)

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A grid with a high level of renewable energy will have low inertia. This reduces available response time and means that smaller shifts in supply and demand can reach the threshold for customer loads to be disconnected. (Denholm, 2020)

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Potential Solutions for Controlling Frequency in Variable Generation Sources

Some frequency control can be achieved through the use of variable generation as dispatchable resources. Both wind and solar can be operated below maximum output for any given conditions. Controls can be put in place to increase output in response to dropping frequency. However, this results in a significant loss of energy production, as not all available wind and sunlight is being used. (Denholm, 2020)

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One potential solution to this is the use of a synchronous condenser. A motor draws energy from the grid to spin a large mass, like a flywheel. The spinning mass is then used to drive a generator and inject power back into the grid on demand, providing the same inertia as conventional power generation. This type of solution has already been used to solve localized grid issues and could potentially be scaled up to stabilize grids with high levels of variable generation. (Richard, 2020)

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The Texas ERCOT grid has an average of 20% variable generation, mostly wind, reaching the highest instantaneous penetration of 57.9%. ERCOT has worked to improve frequency stability with a program that allows private entities to register as load resources. These load resources are put under grid control, allowing them to be shut down or limited during demand peaks. Examples include industrial facilities and large HVAC systems. Companies receive payments based on the size of their load for participating. (ERCOT, 2018)

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Solutions Are Currently Under Development in Anticipation of Increasing Reliance on Wind and Solar Energy

Increasing the proportion of variable generation from renewables such as wind and solar within the overall grid supply poses both technological and infrastructure challenges. Changes must be made to conventional grid management to account for intermittent capacity along with instantaneous control. Efforts by governments and utility companies are currently underway to address these challenges through energy storage projects and changes in grid management practices.

 

References

1. Biserčić, A. Z. (2021). Reliability of Baseload Electricity Generation from Fossil and Renewable Energy Sources. Energy and Power Engineering.

2. Canada Energy Regulator. (2016). Market Snapshot: Pumped-storage hydro – the largest form of energy storage in Canada and a growing contributor to grid reliability. Retrieved from https://www.cer-rec.gc.ca/en/data-analysis/energy-markets/market-snapshots/2016/market-snapshot-pumped-storage-hydro-largest-form-energy-storage-in-canada-growing-contributor-grid-reliability.html

3. Canada Energy Regulator. (n.d.). Electricity Trade Summary. Retrieved from https://www.cer-rec.gc.ca/en/data-analysis/energy-commodities/electricity/statistics/electricity-trade-summary/index.html

4. Denholm, P. (2020). Inertia and the Power Grid: A Guide Without the Spin. National Renewable Energy Laboratory.

5. ERCOT. (2018). Dynamic Stability Assessment of High Penetration of. 

6. Government of Canada. (n.d.). Canada’s Clean Electricity Future. Retrieved from https://www.canada.ca/en/services/environment/weather/climatechange/climate-plan/clean-electricity.html

7. IESO. (2024). Resource Acquisition and Contracts. Retrieved from https://www.ieso.ca/en/Sector-Participants/Resource-Acquisition-and-Contracts/Long-Term-RFP-and-Expedited-Process

8. Natural Resources Canada. (2024). Electricity Generation Energy Use and Generation by Energy Source. Retrieved from https://oee.nrcan.gc.ca/corporate/statistics/neud/dpa/showTable.cfm?type=HB&sector=egen&juris=00&rn=1&page=0

9. Richard, L. (2020). Optimal Allocation of Synchronous Condensers in Wind Dominated Power Grids. IEEE.