In looking ahead to future electricity options, it's important to understand how different types of supply can contribute to a power grid. We meet generation needs though a combination of sources including coal, gas, hydro, wind and purchased power. All vary in how they are able to provide electricity to Saskatchewan's power network and contribute to making sure electricity is there when we need it.
Base load
The minimum amount of electric power delivered or required over a given period of time at a steady rate. The generating equipment associated with this normally operates to serve loads on an around-the-clock basis. These units can change their output somewhat to follow hourly demand, but are not turned on and off to follow instantaneous load changes.
Intermediate
These plants meet demand during peak business hours of the week and colder months of the year. They have moderate fixed costs and higher variable costs than base load units. Our intermediate load resources include hydro, gas-fired generation and imported power.
Intermittent
These facilities cannot be dispatched (turned off and on to meet demand). They produce power intermittently - when the resource they depend upon is available. Wind is an example of intermittent generation.
Peaking
These units only operate at times of peak system demand, such as suppertime. They start up and shut down quickly. Peaking units have lower fixed costs than others, but sometimes have high variable costs related to fuel. Our peaking fuels are natural gas and hydro.
This supply combination provides us with the flexibility to serve a demand for power that can swing 500 to 1,000 megawatts (MW) daily, as loads drop overnight and begin to rise in the morning.
Supply and demand
Modern electric systems are designed to meet customer demand in real time—meaning that supply and demand must be constantly and precisely balanced. As electricity cannot presently be stored on a large scale, changes in customer demand throughout the day and over seasons are met by constantly controlling output of the available generation. When there is a generation shortfall, power will flow in from neighbouring utilities over interties, and where there is excess generation, power flows out.
Interconnection flows can have a significant impact on the reliability of interconnected electric systems, particularly when there is a sudden loss of a generator. To minimize the risk of a system failure, the electricity industry has established reliability standards and guidelines requiring utilities to closely control intertie flows. Reliability standards also require that the electric system operators maintain sufficient transmission infrastructure and generating capability to withstand the sudden loss of the largest generator in its fleet.
