Surplus base-load generation (SBG) has become an issue lately. It occurs when Ontario's "must run" electricity sources (predominantly nuclear and hydro but also wind and solar) exceed Ontario's minimum demand. SBG typically occurs on weekends or late evenings when Ontario's tie-lines can't export the surplus.
The IESO has formed a committee (SE-91) to find solutions to the problem. Their initial proposal was a band-aid approach to curtail wind production during periods of SBG. The root cause of the problem, of course, is that Ontario's nuclear capacity has gradually grown even as the province's demand has flattened. Fortunately, Paul Murphy, the CEO of the IESO, has the vision and courage to speak out against the nuclear lobby.
The original article is here.
The Ottawa Citizen
February 6, 2012
OTTAWA — For at least eight hours Monday, Ontario is once again forecast to produce more electricity than it consumes, and the recurring glut has one top energy executive warning of temporary nuclear power plant shutdowns.
“We have largely been able to avoid nuclear shutdowns to deal with the (surplus) conditions but this may not be the case in the near future,” Paul Murphy, head of the Independent Electricity System Operator (IESO), recently told an industry gathering.
His comment is raising questions about Ontario’s plans to boost nuclear power as the province’s chief source of energy.
Nuclear-generated power supplies about 57 per cent of Ontario’s electricity. Based on the province’s assumption that demand will grow moderately over the long term, multi-billion-dollar projects are contemplated for new reactors and refurbishments of existing ones.
The problem is, unlike wind and some other forms of power production, nuclear reactors can’t easily be turned off when demand for electricity drops.
Returning them to full operating status can take two to four days and sometimes longer, making nuclear the least flexible portion of the supply mix at a time when demand is increasingly finicky.
And since electricity can’t be stored and must be used as soon as it is generated, the resulting “surplus baseload generation” in the system has to be exported to neighbouring provinces and states, usually at a bargain price, until the IESO can rebalance supply with demand.
In some cases, “negative pricing” is required. Ontario electricity producers shelled out $35 million in the first six months of last year alone to get neighbouring jurisdictions to take surplus power, up sharply from the same period in 2010, when negative pricing amounted to $4.2 million.
The supply surpluses have become increasingly common since 2005 and are expected to continue for at least a few more years, said Murphy.
Yet some surplus periods, which are forecast based on weather predictions and historic patterns, sometimes only last for a few hours.
“We need to find alternative ways to address (surpluses) to avoid using a multiday nuclear shutdown to address surplus conditions that could last for only a few short hours,” said Murphy.
“Given the potential of quick swings from surplus to shortage, those actions could have greater consequences in the future if the shutdown nuclear unit is not available by the time we need it again.”
Last June 8, for example, he said Ontario was exporting “everything we could to keep supply in line only to declare an energy emergency alert just 12 hours later. Demand climbed to the point where we were using every available megawatt in Ontario to meet that demand.”
Murphy’s remark about potentially and temporarily shutting down power reactors casts doubt on some fundamental assumptions of the province’s energy planning, says Mark Winfield, an associate professor in the faculty of environmental studies at York University.
“Given the province is theoretically committed to building a new nuclear plant and is considering refurbishment decisions on Bruce B (reactors), the implication is, one, you shouldn’t be adding supply on that scale and, two, if you’re going to add supply, it probably should be supply that you can turn off when you don’t need it,” says Winfield, who also co-chairs the school’s Sustainable Energy Imitative.
“It’s the IESO whose job it is to have their finger on the pulse of the system and also to be looking ahead (and it is) basically saying that potentially some pretty fundamental assumptions underlying planning for the system for the past decade need to revisited.”
Contributing factors to the excess supply include the global economic slump, consumer and industry conservation measures. and the Ontario economy’s transition away from manufacturing and resource-processing.
Seasonally, the situation typically worsens in spring and fall, when furnaces and air conditioners are turned off, and spring runoff forces hydro facilities to “spill” the water rather than store it for peak periods.
Additional factors will be the return to service of two refurbished reactors at the Bruce generation station near Kincardine and the increasing quantities of renewable energy coming on to the grid under Ontario’s Green Energy Act.