Integration 101: How renewable energy resources fit into the electricity grid

The electrical grid appears simple, turning on a light switch or moving the thermostat and getting an instant result. Usually, the light comes on or the room begins to warm or cool. However, the electrical grid is much more complex and requires many different tasks to be performed properly for the grid to function as needed.

Electricity generation follows a simple principle which is “Energy can neither be created nor destroyed, only altered in form.” When a utility burns a fuel, splits an atom, turns a generator using wind or water, or collects energy from the sun, energy is transformed into electricity.

1) How electricity gets delivered to you.

However, in many cases, this electricity must be available at any time or in storage to ensure lives and businesses can work seamlessly. Firm load, commonly referred to as base load, is the amount of customer demand that must be met at all times. This means the utility must always have sufficient resources available to meet this level of electricity demand.

Electricity that can be delivered at any time when needed by customers is called dispatchable generation. Dispatchable generation helps to stabilize electrical grids and allows utilities to use more and more renewable energy (also known as variable or intermittent electricity) as it can deliver energy in the moments when renewable energy (such as wind and solar) are not available (e.g. when the wind is low at night).

Why is electricity integration so important?

Understanding the proper system arrangement between dispatchable and intermittent electricity generation is crucial in designing a reliable and resilient electricity grid, especially in the context of an energy transition towards more sustainable energy.

What is Dispatchable Energy?

The electricity needed by customers constantly changes throughout the day and can vary significantly by season. This daily energy demand must be matched perfectly with energy supplied from the electrical grid. Energy resources that can provide energy on demand at any time are called dispatchable resources. Some common sources of dispatchable electricity generation include some fossil fuel-fired rapid response generation (e.g. natural gas, coal in Nova Scotia) and some hydroelectric facilities. Battery energy storage systems (BESS), when charged, are beginning to be used for this role as well

When renewable electricity resources or imports are not available (e.g. wind generation is low, water is low, sun is not shining), dispatchable resources can be used to maintain a reliable source of energy for customers.

Electricity generation facilities used to meet demand peaks, also known as peaking plants, generally rely on dispatchable sources. Some forms of fossil fuel-fired electricity generation can take different amounts of time to ‘turn on’ and ramp up electrical supply to the grid. Some dispatchable fossil fuel-fired generation types can respond almost immediately, while others can take between 4 and 24 hours to begin production of needed electricity.

The fastest dispatchable plants, such as charged storage (BESS), hydroelectric generation and electricity imports, are often deployed to meet daily demand peaks. Slower dispatchable plants play a key role in addressing seasonal demand peaks, like those on cold winter days, which are generally easier to forecast. Ensuring sufficient capacity across all types of generation is essential for meeting system peak demand reliably.

To add intermittent energy sources (generally wind and solar generation), a system must have a strong dispatchable energy network which can respond quickly to changes in the amount of energy demanded by an energy grid network.

What is Intermittent Energy?

Wind and solar renewable electricity generation are common intermittent energy sources as they are not always available. The wind doesn’t always blow, the sun doesn’t always shine, and sometimes water levels are too low to use for hydroelectric generation.

However, when intermittent sources are combined with storage mediums such as a battery energy storage system for example, they can provide a dispatchable source of energy generation to help cover system demand peaks when fully charged. In the periods where battery storage is being charged, fast acting generation can be used to support those periods where wind, solar and BESS are not available.

In the future, long duration battery energy storage systems, once commercially available, is a technology that can be explored to provide instantly dispatchable energy to help balance the grid and meet daily demand peaks.

Nova Scotia's Firm Load Challenge:

Nova Scotia stands out within the Atlantic provinces in its approach to integrating new renewable energy into its electricity system. Unlike New Brunswick and Newfoundland and Labrador, which benefit from significant resources from hydropower or nuclear generation, Nova Scotia has few low-emission dispatchable resources. The province has no potential to develop significant new electricity generation from biomass, for example. Historically dependent on coal, the province is now working towards a greener energy future, within these realities, while maintaining a reliable grid.

By 2030, Nova Scotia requires 80% renewable energy on its electricity grid, part of this will continue to be met using imports from Newfoundland and Labrador via the Maritime Link. Nova Scotia has also committed to a significant buildout of wind and solar generation in the province to help replace fossil fuel-fired generation and meet growing demand.

One of the key aspects of Nova Scotia Power’s approach to meeting 2030 targets is to build new dispatchable electricity generation that can be called upon at any time to ensure it can provide electricity for its customers on demand when they need it. One of the utility’s solutions to this challenge is to integrate grid-scale battery projects (it is currently developing three 50 MW projects). However, batteries take time to charge so they cannot be relied on as a silver-bullet solution, based on technology available today.

Nova Scotia Power will also build new natural gas and dual fuel combustion turbines and convert some existing coal units to burn natural gas or heavy fuel oil. These combustion turbines will provide fast-acting dispatchable resources to fill the gaps when renewable generation is low. These turbines will be used infrequently but are important to help maintain reliability while keeping costs as low as possible. Importantly, these combustion turbines can use natural gas as a bridge to future clean fuels like green hydrogen.

How can Atlantic Canadian utilities add more wind and solar generation to their electrical grids?

To allow more renewable electricity generation, like wind and solar, utilities must integrate these energy sources with their existing resources and new fast acting generation and/or battery storage to ensure that if the wind isn’t blowing or the sun isn’t shining, a customer still has power available to them. Integration methods come in many forms from energy efficiency (to lower the overall demand), to adding more immediately dispatchable generation just as natural gas combustion turbines, to battery energy storage systems and pumped hydro storage. These integration methods won’t be used all the time but must be available when needed to ensure customer demand is met.

With enough integration capacity in place, utilities can add larger quantities of intermittent electricity generation (like wind and solar) to their electrical grids without a risk of an electricity shortage in times of low energy production.

What is the role of renewable electricity integration in Atlantic Canada’s net-zero future?

Adoption of wind and solar electricity generation have risen dramatically in Atlantic Canada and will continue to do so for the foreseeable future. It will be increasingly important to integrate more, often affordable, renewable energy for Atlantic Canada’s grids, especially in the Maritime provinces, to decarbonize the electricity sector and meet growing demand with new low-emitting generation. At the same time, especially in Nova Scotia and New Brunswick, utilities will stop using coal-fired baseload generation by 2030.

To do so, Atlantic utilities are already pursing several strategies to build more dispatchable generation including battery energy storage systems, exploring opportunities for more electricity imports (and exports in NB and NL), energy efficiency programs. NB Power, Nova Scotia Power, and Newfoundland and Labrador Hydro are all pursuing new fossil-fuel or dual fuel combustion turbines to use on a limited basis. All these strategies, together, will play a role in ensuring the Atlantic grids can integrate more renewables as affordably and reliably as possible for ratepayers.