The growth of coal.
Coal-fired generation was up for the 6th consecutive week, repeating the performance seen in the spring.
Despite over 20% of Ontario's coal capacity being removed from service at the end of 2011 (Nanticoke units 1 and 2), the year-to-date total coal production is now up over the same period in 2011.
The Ontario government's mantra that 'wind is replacing coal' is increasingly farcical. Germany is increasing coal builds; 4 times more hard coal-fired capacity is planned than natural gas capacity (BNetzA .xls), and the boasts of the flexibility of their newest coal-fired units must create envy in Ontario's System operator (IESO) as they lament the planned elimination of flexibility in Ontario.
The desirability of the coal units is in their peaking depth - meaning a hot coal-unit offers a far greater operational range (20-100%) than the CCGT plants Ontario has contracted, expensively. Coal did serve an intermediate supply function in the past (matching the higher demands of the day, and being removed at night), and that role could be filled by CCGT plants, but ... in the shoulder seasons the intermittent wind and solar supply negate the need for intermediate supply, and what is needed is the peaking depth of coal to accommodate the intermittent generation.
Notes.This article should not be seen as critical of the IESO - quite the opposite. Despite the inflexible supply they are presented with, there were no notable curtailments in the week (although we wouldn't know if Pickering units were offline due to excess supply), nor was there significant negative pricing
---Donald Jones noted the issue with peaking capacity (not using that term) a couple of years ago in an article here.
His latest article notes some of the engineering challenges that should be met to allow nuclear to provide more flexibility - flexibility that will be increasingly precious as Ontario continues to phase-out coal.