Ontario has some electricity surpluses at times, which the IESO calls “Surplus Baseload Generation”, or SBG. What is it? Is it bad or good? Why do we have it? What solutions are available to solve it? You will no doubt hear more about this, as the Conservatives and anti wind people are sure to twist this into something it is not. The Star has written an article on it.
Supply and demand of electricity must be in balance at all times. Demand goes up and down, varying from about 11,000 MW to 25,000 MW. Demand rises when it is hot (air conditioning), and when it is cold (heating and furnace fans). It goes up on weekdays, and down on weekends and holidays. It is highest during the day, and lower at night. So supply has to go up and down to meet demand. Fossil generators and waterpower routinely provide the increase when needed, and cut back when not needed, reducing fuel consumption and emissions, or saving the water for future use. But sometimes we have too much power that we can’t shut down easily. This is the SBG.
Some generation types are inflexible and can’t be shut down. The only way to reduce nuclear output is to shut down a reactor. But it takes up to 3 days to restart the reactor, so power may not be available when demand goes up the next day or hour. The exception to this is the Bruce unit, which can reduce output by 300 MW per unit X 8 units – that is a lot. The Bruce plant does not require a shutdown, but instead can resume the full output fairly quickly when demand increases. But when they reduce output, we essentially lose the energy – the units do not consume less fuel, they just vent some of the energy as heat.
Wind, by contrast with nuclear, can be shut down, or curtailed, relatively easily. In fact, wind can be used as spinning reserve – ready to come back up at a moments notice, when it has been curtailed. This has been done with offshore wind in Denmark at the Horns Rev project. When wind is curtailed, again, we lose the energy. When generation is curtailed, the system must still pay the generator, whether wind or nuclear, for energy they made available, even when it is not used. After all, they built the plant under contract to produce electricity for the system, and the plant costs continue whether the electricity is generated or not.
What happens when the system is producing more power than can be used, even after the fossil generators and waterpower has been turned down as much as we can? We can do several things. We can export power to New York, Michigan or Quebec. When we do this, they can turn down their fossil generators, or store water behind their dams for future use. We can shut down generation, such as 300 MW per unit at the Bruce plant, or wind turbines. But there are other options that we will explore below that could be a low cost elegant solution.
How did we get to this? The biggest reason is an unforseen drop in demand. Electricity demand in Ontario peaked in 2005 at about 152 TWh. Since then, conservation and a changing economy have reduce demand to about 142 TWh. This has reduced demand at any given time by about 1500 MW, half the size of the Pickering plant, and more than Niagara Falls. It takes time to build new generation capacity, so in 2005, we were contracting for power from wind, nuclear refurbishments, gas, several years in advance, based on the demand forecast (and the coal phase out) at that time. We did not forecast such a big decrease in demand.
Of course we wouldn’t have SBG if we under built our electricity system. This is common in third world countries, where the power is routinely cut in rotating blackouts. If you don’t have enough generation, this will happen. The IESO says that it could cost $225 million per year to reduce the output of wind or nuclear. This is less than 2% of the total electricity system costs. Would you rather save the 2%, and be faced with rotating blackouts? The answer to that one is clear. We need to build some excess capacity to ensure reliability. Is SBG bad? Not when you consider that it came about due to a desire to maintain system reliability.
The current SBG problem may be short term in nature, and reflect the fact that we have built the system for forecasted demand that did not materialize. The reality is that we need to replace or refurbish much or our system, that was mostly built over 30 years ago. The biggest upcoming refurbishment is the Darlington nuclear plant, scheduled to begin in 2016. The plant refurbishment will take 3600 MW off line, perhaps in 900 MW chunks, for a period of years. The 3000 MW Pickering plant will follow, with either refurbishment or decomissioning of all or part of it in 2020. SBG may go away on its own, and instead of complaints of surpluses, we will be grateful for the foresight our planners had in building the capacity a little early.
The major cause of SBG is our reliance on nuclear power. We have 10,000 MW of operating nuclear power (when all the reactors are running), and we have an additional 1500 MW of refurbishments due on line by the end of June. 11,500 MW, if it is all running, is enough on its own to exceed our minimum demand of 11,000 MW. There are several water power and gas co-gen facilities that must be left on line as well. That is the source of SBG. Wind sometimes contributes to the problem, but the highest wind output with the wind currently installed is about 1600 MW. 85% of the problem is caused by nuclear. But wind can be easily curtailed, so it can be part of the solution.
Curtailing nuclear or wind, or for that matter, spilling water, doesn’t seem right, though. In all cases, we are discarding available energy. Surely there is something we can do with this surplus, to perhaps reduce consumption of natural gas, or fuel oil, or save it for the future? It turns out there are lots of things we can do, but we don’t. We haven’t designed our electricity system this way yet. But we can. Here are some options:
The City of Guelph Ontario had a system that could turn off all the electric water heaters in the city for a period of time, to reduce the peak consumption. A signal was sent to shut off the heating element for a short time. Consumers would not even know it had happened, as the heat energy that they wanted was stored in their hot water tanks already. Demand for electricity was shifted to a later time, presumably when electricity was more available, or cheaper, or the transmission capacity was less strained. What about sending a signal to hot water heaters to turn on during times of SBG, raising their temperature by a few degrees?
In downtown Chicago, some of the office towers make ice at night, when electricity demand is low. They use the ice during the day to provide air cooling. The ice has stored the cold, and the demand on the power lines and transformers in downtown Chicago is relieved on hot days, as the cool of the stored ice is used to supplement air conditioners. Make ice during times of SBG.
Toronto Hydro had a program in 2006 to install a wireless device on residential air conditioners, to shut them off for 15 minutes during times of peak demand. Again consumers barely felt it, as a home takes more than 15 minutes for a building’s temperature to rise to uncomfortable levels. Cool buildings by a degree or two during times of SBG, reducing their need for cooling later on.
In the United Kingdom, utilities offered cut rate electricity rates at night under the E7 program (white meters in Scotland), to try to encourage a shift of demand to the night when it cost the utility little to keep operating coal and nuclear plants. Consumers responded by installing a lot of heating closets containing thermal mass, such as rocks or ceramics, heated by an electric element at night. The heat energy was then released during the day when electricity rates are high. The program was so successful, that night time demand increased considerably. Demand was shifted forward by about 12 hours. Summerside PEI does this to deal with surplus wind energy from time to time. Dispatch heating of thermal mass to reduce consumption from other sources of heat.
Pumped storage is widely used in electricity systems. The New York Power Authority has a pumped storage system at Niagara Falls. Surplus night time electricity is used to pump water from the bottom of the gorge to a storage lake at the top of the Niagara escarpment. During the day, or periods of high demand, the water is released, to flow through generators. Pumped storage is a widely used storage method in electricity systems, and is well understood by utility planners. Pumped storage has round trip efficiency of around 85%. Ontario has some pumped storage, but it could be expanded, perhaps using existing dams, but putting in reversible turbines.
The hydrogen can be used as a form of storage. Surplus electricity from SBG can make hydrogen simply by running a current through water, a process called electrolysis. This hydrogen would then be stored, and used in existing hydrogen applications. It can also be injected into natural gas pipelines, reducing the need for natural gas.
Plug in vehicles are entering the market. There is the all electric Nissan Leaf, the Chevy Volt, and Toyota has a plug in version of their Prius coming. Charging vehicles during times of SBG just makes sense, and it is being done elsewhere.
Using surplus energy just makes sense. It replaces imported natural gas, or fuel oil, or gasoline, or reduces the future need for fuel to produce electricity. It is good for emissions. It replace imports with domestic production.
If we have to spend $200 million per year to deal with SBG, wouldn’t it make sense to spend a good chunk of this trying to use the energy, rather than wasting it? We should start working on this immediately. An important side benefit is that solving the SBG problem by creatively using the energy also positions us to utilize variable energy sources like wind, water, and sun more easily in the future.