Minimal system impacts says study

An installed wind power capacity of 5000 MW would have minimal impacts on the operation of Ontario's power system, says a newly released study by GE Energy. The study uses data from 34 met towers around the province to examine five scenarios for wind development, ranging up to 10,000 MW of wind by 2020.

"The results were encouraging in two respects," says Don Tench of Ontario's Independent Electric System Operator, which teamed up with the Ontario Power Authority and the Canadian Wind Energy Association (CanWEA) to commission the 102-page report. "Ontario seems to have better performance than surrounding areas and the effect of geographic diversity in the province look really good."

The study found the average capacity value for wind during Ontario's summer peak ranges from 16-19%, increasing to 38-42% during winter months. The annual capacity factor is about 20%. "Those numbers are consistent with a pretty good temporal pattern for the wind resource in Ontario. Down south in New York we found the onshore resources are more like 10%," according to GE's Nick Miller.

Ontario's current operating reserve can handle the variability that comes with 5000 MW of wind, which is equivalent to about 17% of peak hourly load and 7% of total yearly energy. But at higher penetrations, the study found, additional operating reserves will be required to accommodate extreme drops in wind generation. "By the time you get to 10,000 MW, it is likely going to have to go up something in the order of 500 MW," said Miller at CanWEA's recent annual conference.

Beyond 5000 MW, the study says, the requirement for load following may exceed the capability of existing generators. "It is important that any future supply mix strategy recognise that wind generators will likely displace more flexible generation resources and the remaining balance-of-portfolio resources must be able to accommodate this additional variability," it states.

Light load conditions present a similar challenge at higher penetrations, added Miller. "There are going to be a few hours a years where there is going to be a lot of wind and not much load. Out in those last hours, especially in the last one hundred hours where the system is really disrupted in the sense that a huge fraction of the supply is coming from wind and there is a light load, some accommodation is going to be required," he said. One solution is a combination of controls on wind farms and more flexibility in the rest of the supply mix.

"The province has got to plan to have that operational manoeuvrability in the balance of the portfolio. You can't just look at wind alone. You have got to look at everything else that is there," said Miller.

The results of the study will be used in preparation of the province's 20-year integrated power system plan, to be filed in March. "It has advanced our thinking tremendously," Tench said. "The GE report did a terrific job identifying the facts. It doesn't just look at averages. The extremes of wind performance in Ontario are important. Our emphasis has to include managing those extremes. We don't expect 100% reliability from any facility, but variability at the extremes has to be planned for and it has to be accommodated."

He said forecasting of wind output will be key to managing large amounts of wind power, but argued it will have to become more effective than it is now. "All of us have to make a concerted effort to bring wind forecasting into the same kind of rigor that we use for load forecasting."

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