Natural gas or wind, what comes first? How often are we told through the media and via government spin that natural gas-fired generators will back-up wind generation whenever the wind drops. This gives the impression that gas is there solely to support wind. Not true.
The Ontario grid depends on dispatchable gas, which is replacing dispatchable coal. Wind is not needed at all as far as grid capacity is concerned. To assign a “capacity factor” to wind generation makes no sense since the grid does not need its capacity.
Wind has been added in the belief that periods of wind will reduce the amount of gas being burned and greenhouse gases being emitted. Wind is erratic and intermittent, is not dispatchable, and is added to base load whether needed or not. Nuclear and large hydro run base load. Stored water hydro is fully committed to intermediate load (daily load cycling), some operating reserve and to short periods when dispatched in response to grid load changes until other slower generators catch up. This means gas generation, as well as supplying intermediate and peak load, must be dispatched to discretely move power up and down for the longer term grid changes (load following), including those caused by wind, and be quickly available in case the wind drops.
The erratic minute to minute fluctuations of wind are smoothed out by the rotational kinetic energy of the grid generators, by the hydro and fossil turbine-generators on the grid changing their output by normal speed governor action, and by Automatic Generation Control using a small amount of hydro generation.
The intermittency of wind is handled by dispatchable gas generation. Large amounts of wind in the future will result in costly inefficient operation of the grid, and especially in wear and tear of the gas generators, with little, if any, reduction in greenhouse gases. There is no chicken and egg analogy with gas and wind. Gas comes first.
Indeed the government plan is to have around 12,000 MW of gas generation available in the next few years, with present gas generation at around 8,000 MW. So, how much wind generation can integrate with 12,000 MW of gas. According to the Independent Electricity System Operator (IESO) the dispatchable range of the Ontario combined cycle gas turbine plants is between 70 and 100 percent full power.
Enough gas generation has to be quickly available (depending on how fast wind is fading and the accuracy of the wind forecast) to pick up the slack if the wind drops. Assuming all the 12,000 MW of gas is from combined cycle gas turbine generators (in reality there will be some simple cycle gas turbine units for peaking and operating reserve and some combined heat and power plants adding to base load) then if they are operating at the bottom of their dispatchable range they will accommodate 3,600 MW of wind generation, assuming no other make-up like hydro, imports or demand response loads.
This amount of wind is more than twice the present operating reserve requirement for the grid. In reality the gas generators would be taken down well below their dispatchable range to accommodate wind which means it will take them longer to get back into the dispatchable range when the wind drops. Incidentally, according to the IESO, coal has a dispatchable range of 20 to 100 percent which means that if we stick with the roughly 6,000 MW of coal until it can be replaced by an expanded nuclear fleet the grid would be able to integrate 4,800 MW of wind. However since wind and nuclear are a bad mix there would be no point in having any expensive wind with its associated infrastructure.
Steam bypass will make new nuclear more flexible but at the cost of wasting the energy in the steam plus it is not smart to keep moving the output of multi-billion dollar nuclear plants, producing clean reasonably priced energy, up and down just to accommodate the intermittency of wind. The grid already has about 1,200 MW of wind and 3,500 MW more is expected to be added soon by a consortium led by Samsung and the Korea Electric Power Corporation and by a multitude of other projects and even more, to a total of over 8,000 MW, when grid connections become available.
Is Ontario being too optimistic with the amount of wind the grid can accommodate to the detriment of grid reliability? Does the government really believe its own spin that wind comes first and will it add more polluting expensive gas generation, whose cost depends on gas price volatility, just to accommodate more megawatts of expensive wind even though gas generation’s contribution to the grid would not be needed?
Instead of promoting distributed generation (and the so called “smart” grid) using wind and non-renewable gas and oil on the high voltage and low voltage systems wouldn’t it make more economic and environmental sense to improve the reliability (improved monitoring of equipment, replacement, refurbishment, redundancy etc) of the present centralized system based on clean nuclear and hydro generation since fossil fuels are going to be scarce and expensive in the future?
The operation of the Ontario grid is complex and this is a simplistic perusal but it does raise questions that need to be answered.
Donald Jones, P.Eng
Other relevant pieces:
“IESO – Will Ontario’s wind turbine power plants reduce greenhouse gas emissions?”,