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.