Grid Scale Energy Storage

Grid-scale energy storage refers to a system capable of storing large amounts of energy and converting it to electricity when needed. The ability to store energy is becoming increasingly important in power grids worldwide as it increases their flexibility and reliability. Renewable energy sources like wind turbines and solar panels benefit greatly from energy storage systems, as they rely on the sporadic nature of wind and sun to produce power, resulting in not necessarily supplying energy when it is needed. The ability to produce power from renewable sources and then store that energy for when it is needed is very beneficial to the overall energy output of renewable sources. In northern Canada, many utilities are adopting grid-scale storage for various projects to increase grid stability and reliability while reducing carbon emissions and costs. 

This blog post will answer the following questions: 

1. Why use grid-scale storage? 
2. What technologies are used for grid-scale storage? 
3. How is storage technology is used in the Yukon? 

Why use grid-scale storage?

Energy storage can help with reliability as it can control and improve system stability by maintaining a stable voltage and frequency, preventing issues that can cause power quality issues or even brownouts and blackouts.  

One of the biggest benefits of energy storage comes when paired with renewable energy. When solar and wind power generate more electricity than needed, storage systems can capture the extra energy instead of letting it go to waste. Later, when renewable sources produce less, like at night or on cloudy days, this stored energy can be fed back into the grid.  

In some cases, microgeneration renewable energy can provide too much power on the grid, causing problems like voltage spikes and frequency imbalances. Grid-scale storage can help by storing that excess energy and releasing it when demand rises or when renewable energy sources aren’t producing energy (i.e. when it’s cloudy or not windy). This reserve of energy can keep the grid running smoothly. Since storage can help with both balancing system stability and storing excess renewable energy, this means that grid storage can increase the amount of renewable energy in the system. 

Being able to store large amounts of power means that when the grid might need extra generation, such as in times of peak demand, more generation does not need to take place. Instead, that power will come from grid-scale energy storage rather than a nonrenewable energy source. This means that grid storage can be used either for supporting peak generation or to offset nonrenewable energy with stored clean renewable generation.  

What technologies are used for grid-scale storage?

Below are some of the common grid-scale storage options. Many of these technologies are being developed and pursued by various countries around the world; however, the uniqueness of northern Canada’s landscape means that not all technologies will be equally viable. In the following section, we will review case examples of how these energy storage options work and some of their advantages and disadvantages. 

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Battery Energy Storage (BESS)

Batteries are a chemical storage method which allows easy charging and discharging with the ability for power to be stored for many days, weeks or months with minimal losses. This is the most common storage method.

Advantages:
– High Energy Density: Capable of storing large amounts of energy in compact spaces. 
– Fast Response: Can respond to operator needs in milliseconds 
– Scalability: Suitable for small and large-scale applications. 

Disadvantages:
– Cost: Relatively high but decreasing over time as technology matures. 
– Lifespan: Degrades with each cycle of use. 
– Safety Concerns: Risk of dangerous fire due to reignition, toxic gases and runaway chemical reaction 

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Pumped Storage Hydro (PSH)

Pumped hydro works by using excess power generation to pump water to a higher elevation where it is stored for later use. When power is required, they operate the same as hydroelectric dams, which spin turbines with released water. 

Advantages:
– Large Capacity: Can store large amounts of energy, suitable for grid-scale operation. 
– Long Lifespan: Long lifespans of 50 to 100 years 
– Low Operating Costs: After initial design and construction, maintenance and operating costs are low.

Disadvantages:
– Geographic Limitations: Requires elevation difference and geography that allows changing water levels 
– High Initial Costs: Significant investment for construction and design. 
– Environmental Impact: Can cause ecological disruptions due to changing water levels and reservoir construction.

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Thermal Energy Storage

Thermal energy can be stored in 3 ways:  
– Raise the temperature of a liquid or solid 
– Store energy through phase change of a material. For example, liquid to gas.
– Reversible thermochemical processes where chemical reactions absorb and release energy

Advantages:
– High Efficiency: Particularly when integrated to capture waste heat from thermal power plants or manufacturing. 
– Scalability: Can be designed for various capacities. 

Disadvantages:
– Thermal Losses: Thermal energy dissipates over time, directly impacted by amount of insulation 
– Infrastructure Needs: Requires substantial space and insulation. 
– Specific Applications: Best suited when paired with thermal energy generation.

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Hydrogen Storage

Hydrogen storage works by using extra electricity to perform electrolysis on water, splitting each molecule into its atomic components: 2 hydrogen atoms and 1 oxygen atom. Hydrogen is stored for later use by combustion in either power generation or transportation.

Advantages:
– Flexible Storage: Effective for seasonal or short-term storage. 
– Versatility: Hydrogen can be used for electricity generation and transportation. 
– Potential for Green Production: Can be produced in a green manner when paired with renewable energy.

Disadvantages:
– Low Round-Trip Efficiency: A lot of energy is lost in the process of producing hydrogen. 
– Infrastructure Requirements: Needs specialized storage facilities. 
– Safety Concerns: Hydrogen’s flammability requires specific handling protocols. 

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Compressed Air Energy Storage (CAES)

Compressed air storage is the pumping of air into a container to an increased pressure. Storage can be done with man-made cylinders or geological formations such as caves and caverns. When power is required, the air is released, and the pressure is used to spin turbines. 

Advantages:
– Large-Scale Storage: Capable of storing large amounts of energy. 
– Long Lifespan: Components are durable with a long operational life. 
– Cost-Effective for Bulk Storage: Cost-effective for technologies that store air in caverns or geological features. 

Disadvantages:
– Low Round-Trip Efficiency: A lot of energy is lost in the process of pumping air in and in generating power from that air. 
– Geographic Constraints: Only certain regions have the necessary geography to enable storing air in caverns.
– Complexity: Can involve intricate engineering and design considerations. 

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Flywheel Energy Storage

Flywheels store energy by spinning a large mass using an electric motor. When energy is required, the process reverses, and the spinning flywheel turns the motor, generating power. 

Advantages:
– High Energy Density: With limited space, large amounts of power can be stored 
– Fast Reacting: Delivers rapid energy discharge. 
– Long Lifespan: Capable of charging and discharging with minimal wear over time. 
– Low Maintenance: Mechanical simplicity reduces maintenance costs. 

Disadvantages:
– Short Duration Storage: Stores energy only for short periods. 
– Self-Discharge: Due to friction, flywheels lose energy over time. 
– Cost: High initial costs for advanced flywheel systems. 

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Energy storage in the Yukon
Battery energy storage

The Yukon has many different examples of grid-scale energy storage. The Old Crow, Kluane, and Watson Lake renewable energy projects include the use of batteries as energy storage in remote power grids.  In these projects, a battery was used to chemically store excess power produced by either a wind turbine or solar panels. When enough power is stored, the utility can turn off the diesel generators in these communities, reducing diesel consumption and greenhouse gas emissions as the power system can run entirely off the battery and the renewable energy source. Batteries are great for these types of projects as they are fast responding and can easily control the grid frequency and voltage. They are also well-understood technologies that can be easily scaled to the size of the project. 

Another battery project is the Whitehorse grid-scale battery, which aims to be finished in 2025. This project aims to use battery storage to supplement generation during peak demand periods in winter months, replacing potential diesel and natural gas generation with renewable energy produced at a low demand time. Additionally, the battery will enhance system reliability, support the adoption of renewable energy, and help the Yukon interconnected grid during brownouts and blackouts. The Whitehorse battery project consists of a 40MWh lithium-ion battery designed for a 20-year lifespan, housed in climate-controlled shipping containers. When completed, it will be the largest grid-scale battery in northern Canada and is estimated to displace 7.2MW of generation when operating, which will displace as much power generation as 4 of the 17 rented diesel generators used in the winter of 2020. To ensure safety for Yukoners, the battery units are fitted with an automatic fire suppression system and are enclosed in shipping containers to stop the spread of fire in the unlikely event of ignition. 

Pumped storage hydro

Yukon Electric Corporation has proposed the Moon Lake pumped hydro project, which would pump water from Tutshi Lake into Moon Lake.  Water would be pumped into Moon Lake during the summer when there is excess renewable energy and then released during the winter to flow down to a generating station on Tutshi Lake. This would help reduce the amount of winter power demand that is currently being met through diesel generators. This project would require the construction of a new dam on Moon Lake, a penstock (transportation piping), a generation building on Tutshi Lake, and a 138kV transmission line to tie the system into the Yukon interconnected grid. The proposal outlines two storage options for the project: 48 GWh of storage with a 20.2 MW generation capacity or 70 GWh of storage with a 26.1 MW generation capacity. According to Yukon Energy, the average household consumes 0.012 GWh of electricity per year. Based on this estimate, the project could offset the annual energy consumption of approximately 4,000 homes under the 48 GWh storage option or 5,833 homes under the 70 GWh storage option. 

Thermal energy storage

The electric thermal storage (ETS) project in the Yukon aimed to test the validity of using household electric thermal storage units and demand side management to reduce household heating emissions. This demonstration program replaced baseboard, oil, and gas furnaces in 45 homes in Whitehorse and 1 commercial building. This project aimed to determine whether ETS units would be an effective method of reducing peak demand by charging the ETS unit at low demand times and releasing the stored heat during high demand times, heating the building without consuming power.  

While not in the ETS project and in the Yukon, ETS units combined with demand-side management could allow charging to be done during times of low demand when renewable energy is being produced, making this a solution for storing renewable energy.  

Contributors

Author: Simon Kerkhof
Reviewed By: Simon Geoffroy-Gagnon and Trent Gardiner 

References

1. Grid Scale Battery Energy Storage System – Yukon Energy
2. Old Crow Solar Project – Yukon University Power System Impact Report
3. Moon lake Pumped Storage Conceptual Report – Midgard Consulting Inc. 2015
4. Electric Thermal Storage Project – Yukon Conservation Society