More wind generation on Ontario electricity grid means more pollution

By: Donald Jones, P.Eng., retired nuclear industry engineer, 2015 January

It seems that the more wind there is on the Ontario electricity grid the more pollution there is. Case in point, a snapshot of the Independent Electricity System Operator’s (IESO) Generator Output and Capability Report for 2015 January 8 at 7 pm, which was a high wind high demand day. Wind was generating 2,631 MW, natgas or frackgas was generating 3,783 MW with the balance of the demand being met by nuclear and hydro. There were net exports of 3,500 MW. Now if there were no exports, natgas generation could have been reduced to 283 MW (assuming this low generation were achievable technically and under the must-run contracts) with a clean supply of nuclear, hydro and wind meeting the major part of the Ontario demand. Obviously 283 MW of natgas generation produces less greenhouse gases (GHGs) than 3,783 MW of natgas generation. So why did we need to export any gas generation in the first place since exports are highly subsidized by Ontario ratepayers to the benefit of the recipient jurisdiction?

This large amount of gas generation was likely exported because of the concern the IESO may have had with the risk of losing substantial wind generation under these circumstances (reference 1). Since most of the gas generation would be shutdown without exports the potential loss of 2,631 MW from wind would have had to be met from hydroelectric generation. With hydroelectric generation at this time already at a high 5,535 MW there may not have been enough extra MW and MWh available to cover the time period until the combined cycle gas turbine (CCGT) units could be fired up and dispatched to meet the wind shortfall. Ontario has only one quick start simple cycle gas turbine (SCGT) unit of 393 MW. Imports from other jurisdictions may not be available since wind failures affect large geographical areas and Quebec may have needed all its generation in house or had it already committed. The solution seems to have been to keep the CCGTs running at around their lowest dispatchable load so that they would always be available in case wind generation failed and the only way to do this was to feed an export market (reference 2). If sufficient extra MW and MWh of hydroelectric generation were available until the demand dropped there would be less or even no need to fire up the CCGTs. However, over the next five years or so several thousand MWs of additional wind will be coming onto the grid. With hydro generation limited the grid will see more use of the GHG emitting CCGTs (in MW and in MWh) and of exports (as in this snapshot) to maximize the use of the wind generation investment and minimize wind curtailment. The Ontario grid will depend even more on an export market and on reliable wind forecasting.

Ontario presently has one small SCGT unit and (I believe) two CCGT plants capable of operating simple cycle, Portlands and Goreway. One could ask why not build more SCGT units to quickly pick up the load if wind generation falls off. SCGTs and CCGTs operating simple cycle are much less efficient than CCGTs and produce more GHGs per unit of output. The amount of gas generation on the grid should be sufficient to meet the balance of the grid demand without any contribution from wind generation. That’s what Ontario already has. Any more would be uneconomic, superfluous to the grid and amount to another subsidy to the wind operators (reference 1).

In retrospect it might have been advantageous to have kept the coal-fired plants operating (reference 3). The coal units can be dispatched down to 20 percent of full power while the CCGTs can only be dispatched down to 60 to 70 percent of their full power. This means that for the same ramping capacity as gas, to cover for the loss of wind, less GHGs might have been produced using coal (reference 4). More so in the future with the addition of several thousand MWs of new wind.

Without large amounts of installed wind on the grid the gas plants would be able to meet the goals of the long forgotten 2007 Integrated Power System Plan (IPSP) to use natgas for peaking, high-value and high-efficiency uses like meeting the Ontario peak load (using SCGTs) and intermediate load (using CCGTs) and not for supporting intermittent wind, and gas exports. Doing this would have avoided the capacity payments (net revenue requirements) now made to the operators of the large CCGTs because wind generation makes merchant operation uneconomic (reference 5). If there were no wind generation installed on the Ontario grid and no exports then under the system conditions of this snapshot gas-fired generation could be reduced from 3,783 MW to 2,914 MW giving a reduction in GHGs and would just supply Ontario’s intermediate load as per the 2007 IPSP.

The use of natgas described in the 2013 Long-Term Energy Plan is less prescriptive than that of the old IPSP and says, “Natural gas-fired generation will be used flexibly to respond to changes in provincial supply and demand and to support the operation of the system”. Even so, exporting large amounts of gas generation out of the province to support unreliable wind hardly meets this vague directive or meets the intent of the 2009 Green Energy Act to reduce GHGs.

Large amounts of wind and solar generation on low demand days can necessitate reductions in non-GHG emitting hydro and nuclear generation. If this results in the complete shutdown of one of Ontario’s present nuclear units that unit will be off-line for three days due to the unavoidable physics of nuclear operation and if demand then picks up the balance of the demand will have to be met with GHG emitting gas. It is not known if any of the nuclear units off-line at the time of the snapshot was because of wind. The Enhanced CANDU 6 nuclear plant proposed for Darlington B would be able to reduce output to zero by a combination of steam bypass and reactor power reductions and would be immediately available if the demand picked up. However reducing the output of non-GHG emitting nuclear to allow expensive wind on the grid makes little environmental, economic or technical sense.

Unlike most other grids Ontario is fortunate in having significant hydroelectric generation to act as a reservoir between wind and gas to avoid always having gas-fired units in continuous “back-up” operation. However this reservoir is of limited capacity, especially with more wind coming onto the grid, so more operation of the big CCGTs will be expected in the future.

Of course running a grid is a pretty complex task, as is running an electricity market, so there may be other reasons that large amounts of GHG emitting gas generation is being exported at whatever the environmental and financial cost to the Ontario ratepayer but the end result seems to be, more wind on high demand days means more GHGs (reference 4 and 6). The future Ontario grid will inevitably be a practically zero GHG emitting nuclear-hydro grid, with no gas and no wind, supporting an electrified transportation system and with space heating being provided electrically. This will mean more nuclear build to meet the increased load demands.


1. More wind means more risk to the Ontario electricity grid, 2011 January 22, Don Jones,

2. Why Ontario has to export electricity, 2011 February 22, Don Jones,

3. An alternative Long-Term Energy Plan for Ontario – Greenhouse gas free electricity by 2045, 2011 May 30, Don Jones,

4. IESO – Will Ontario’s wind turbine power plants reduce greenhouse gas emissions?, 2010 August 23, Don Jones,

5. Why wind power does not work in Ontario – and the solution, 2012 August, Don Jones,

6. Ontario’s electricity – greenhouse gases up, cost up, security down, 2013 December, Don Jones,


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