Monday, May 7, 2012

Surplus Baseload Generation, and Supply Curtailment

Ontario's electricity supply challenges include curtailing supply when it is too abundant, and Ontario's Independent Electricity Supply Operator (IESO) has been working towards better management of the supply through better information.  This short post is a question for the IESO; readers of this blog may feel compelled to request similar information.

Ratepayers have been charged to set up central wind forecasting. I was of the understanding that the "Forecast Surplus Baseload Generation Report" changed with the introduction of this central forecasting.
  • Forecasted weather is used to determine Ontario Demand and Wind Generation as part of the SBG calculation. 
  • The following assumptions are made when forecasting SBG: 
    • Baseload energy is the sum of all available nuclear, must-run hydroelectric, self-scheduling, commissioning and intermittent generators.
    • The Export Forecast is based on available tie-line capacity and historical exports.
    • The must-run hydroelectric is an estimate arrived at from information provided by the Generators. 
    • Only surplus generation is displayed in the report.
  • Minimum Generation Alerts are indicated up to four days in advance of real time when SBG is expected to exceed forecasted exports for more than 2 hours (Days 1-2) and 4 hours (Days 3-4). See SSR and SAA for additional information including Minimum Generation Event notifications.
The report for May 3rd showed alerts for May 4th and 5th and 6th.   Coincidentally, there appears to have been some non-utility generators idled, presumably at a cost, from late Friday evening to Monday morning (the 4th -7th of May).

The SBG report for the 3rd, seemed to call for this action, because it showed alerts for the 4th, 5th and 6th.  I've highlighted hours where "SBG is [was] expected to exceed forecasted exports"

Date Surplus Baseload Generation for Hour
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Export Forecast Min Generation Status
2012-05-04 2202 2409 2401 2253 1761 995 654 616

247 553 1140 1128 1511 1633 1294 1405 1700 Alert
2012-05-05 1195 1291 1472 1262 1122 1000 468 403 215 241 363 457 587 548 637 1117 1293 1544 1533 990 840 1234 1760 982 1700 Alert
2012-05-06 1367 1539 1744 1733 1598 1739 1425 1350 1103 1195 1101 991 1123 926 664 1093 1219 1560 1741 1331 865 1464 2181 1324 2200 Alert

Supply was curtailed entering the weekend, presumably based on Surplus conditions, but the conditions that are stated to cause an Alert were not present on either the 5th or the 6th.

I would appreciate the IESO clarifying;
  • Was the "Alert" status for the 5th and 6th in error
  • Is supply curtailment action instigated by SBG alerts
  • Is the "Alert" status programmed, and, if so, how does the program trigger the 'Alert' status (clearly it is not as described on the cited web page)
My guess is that available export possibilities are shrinking, and if that is the case forecasting involved in SE-91 talks would be impacted (as curtailment will be necessary more often).
Transparency on this matter may allow investors to curtail spending on generation which will have lower utilization rates than previously anticipated.


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