The Electric Reliability Council of Texas (ERCOT) is predicting that, based on current forecasts, it will make it through the summer of 2012 without resorting to rolling blackouts.
“Last summer was the hottest and driest summer since they started keeping records in 1895,” Kent Saathoff, ERCOT’s vice president of grid operations and system planning, said during webcast held by TransmissionHub on April 11. “We had an actual peak demand of over 68,000 MW.”
According to ERCOT’s seasonal assessment of resource adequacy (SARA) issued in March, demand this summer is expected to peak at slightly less than 67,500 MWs given predictions for a summer that is “slightly warmer than normal, but hopefully nowhere near as hot as last summer,” Saathoff said.
Total installed capacity expected to be available during the summer months is slightly more than 73,300 MWs. Under a base case scenario, that would leave a reserve margin of about 6,000 MW, enough “to cover any forced generation outages that occur all the time,” he said, while still leaving sufficient capacity for operating reserves.
Extreme load from another record-hot summer coupled with regular generation outages would use up a little over 7,000 MW of reserves, which would put the system at a little over 1,500 MW deficit, Saathoff said. “Under those conditions, we would have to shed load,” he continued.
Calls for conservation and price-responsive load resulted in a peak demand reduction of about 1,500 MW last summer. However, Saathoff admitted that, if an exceptionally high number of generator outages were to be coupled with weather that is hotter than forecast, “that’ll put us in an even deeper hole.”
A revised SARA report will be issued in May.
Wind is the wild card
Because of wind’s variability, the grid operator discounts the amount of wind that may be available because it cannot be fully relied upon to deliver energy during peak times.
“Currently, we only count about 8.7% of [nameplate] wind in our numbers,” Saathoff said, though he admitted that was probably too conservative. “Last summer, we had something like 10% to 15% of wind capacity actually generating during our peak periods.”
With 10,000 MW of installed wind capacity in Texas, the difference of wind actually delivered over and above ERCOT’s planning figure of 8.7% could be enough to overcome what would otherwise be a shortfall.
The type of wind available within ERCOT can also make a difference.
“Last summer, we found that coastal wind really came up during our peak demand periods,” Saathoff said.
Others have also credited coastal wind for keeping the lights – and air conditioners – on in Texas during the summer of 2011.
“Last summer, when we had more than 100 days of over-100 degree temperatures, we had some days that, were it not for the wind power on coastal land-based wind farms, we’d have had rolling blackouts,” Texas state land commissioner Jerry Patterson told TransmissionHub in a March interview.
“If we have the type of summer we expect, we should be OK,” Saathoff concluded. “If we do have those extreme conditions, we could be fairly close, if not into, load-shedding.”