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Managing A Diverse Supply of Energy

The diversity in the number of energy sources strengthens the reliability of the entire electricity system.  While Ontario has always benefitted from a diverse supply mix, the range of sources of electricity generation continues to evolve.  The IESO is adapting how it manages the electricity system to effectively accommodate the operating characteristics of these different forms of generation and, increasingly, to also manage demand response.

What was once a centralized, largely predictable system is now very fluid with many different operating scenarios emerging. Today's generation fleet is more variable, with the introduction of wind and solar generation, and it has lost the flexibility provided by coal-fired generation. Demand patterns in the province are also changing, as Ontarians are becoming more conscious of how and when they use energy.  And increased amounts of community-based generation − much of it variable − is displacing energy needed from the transmission grid.

As a result, the IESO is incorporating new technologies and finding new ways of doing business in order to inject greater flexibility and efficiency into system operations. For example:

  • As part of its broader efforts to integrate wind and solar power, the IESO forecasts output from variable generators and dispatch these facilities.
  • A new computer-modeling system has been developed to provide more timely information about the capacity available on the transmission lines, which can change according to system conditions. Using this new system allows the IESO to make more efficient use of existing infrastructure.
  • Given the growing importance of natural gas supply to the electricity sector, the IESO and its partners have worked closely with the sector to continue to improve communications and processes.
  • Demand response and storage are being integrated into the market to provide one of the most sophisticated forms of grid balancing: regulation service. 

Different Generators Serve Different Functions

Maintaining system reliability requires a continuous balance of supply and demand. As demand for energy can increase by more than 10,000 megawatts in one day, the IESO needs consumers and different types of generators to perform different roles in providing that balance.

Some generators are needed to produce a constant supply of energy around the clock to meet basic energy needs, while others are needed to increase or decrease output in step with the second-by-second changes in demand. The IESO coordinates the provincial electricity fleet through the electricity market which maximizes the advantages of each source of supply.

"How is Electricity Made?" a video from the Ontario Ministry of Energy 

Baseload Generation:  Hydroelectric and Nuclear

Run-of-the-river hydro facilities with little or no storage capabilities and nuclear power plants provide basic energy needs 24 hours a day − by producing a constant and steady output with little downtime.  While some of these facilities may be able to decrease or increase their output to a limited degree, these manoeuvres typically take place when electricity demand is forecast to fall below the output from baseload generators. 

Peaking and Intermediate Generation: Hydroelectric, Natural Gas

Some generators are designed to increase and decrease energy output on demand − these include natural gas facilities and hydro generators with reservoirs.  Some of these generators are referred to as peaking generation because they are relied upon to meet the "peaks" on the highest demand days of the year. They can also step in quickly should another generator break down unexpectedly. Others act as intermediate generation − working throughout the day by adjusting output as consumer demand ramps up and down.

As with all forms of generation, there are physical limitations as to how quickly they can ramp up or down.  Gas generators for example, need to be able to run at a certain minimum amount before they can start to vary their output. On the other hand, hydro generation can respond quickly by opening floodgates and using stored water to run turbines. They can be limited in their flexibility when water levels are low, or conversely they may need to generate power because weather conditions like the spring thaw could flood reservoirs.

Variable but Controllable Generation: Wind and Solar

Wind and solar facilities produce energy depending on how strong the wind blows and how bright the sun shines.  While their output is variable, these facilities act as baseload supply, meeting core energy demand needs.  These generators are, however, highly flexible within the limits of the availability of the wind and the sun, and can change output very quickly in response to system signals.  

For that reason, the IESO instituted a dispatch process for both solar and wind facilities connected to the grid and they are now called upon to decrease or increase their output depending on system conditions.  For the most part, this dispatch is currently used when there is surplus baseload generation, but it is also used to help follow changes in demand and to reduce congestion along transmission lines in certain areas.

Ontario's Interconnections: Working with Our Neighbours

Ontario's electricity grid is part of a greater network that spans North America.  These interconnections with neighbouring provinces and states are vital to ensure reliability.  If a local generator fails, power automatically flows in from Ontario's neighbours to help cover the few minutes it takes to get another Ontario-based generator up and running. 

By importing and exporting energy on a continual basis, the IESO has an important tool to help it manage the system and it also creates a more competitive market.  It is currently looking at ways to increase flexibility in how it manages Ontario's interconnections. 

Matching Consumption with Supply:  Demand Response

Large consumers have always played a role in the electricity market. This role will only grow over the coming years. Demand response − consumers increasing or decreasing their electricity use in response to prices and support system needs − can be a highly flexible resource providing valuable stability to the system. In this way, consumers can compete with generators in the electricity market, providing energy and flexibility. 

Learn more about the role of demand response in Ontario's electricity market.