Today's hot, humid weather drove Ontario's electricity demand to it's highest levels since July 22nd of last year, with demand forecast to peak at 5 pm.
The day's generation profile isn't exactly typical for a summer day, but it is a good example for clarifying some of the confusing terms in electricity generation. The term baseload is being deliberately obfuscated recently, but it's pretty easy to spot the traditional meaning in the day's actual production figures for 3 am, and 3 pm
At 3 am demand was around 14000 MW, and we were exporting about 1800 MW in addition to that, at a little over 1 cent/kWh. That gives a decent idea that whatever was generating is more expensive to stop generating than to sell at rock bottom rates. For different reasons, this applies to nuclear, the big hydro installations (ie. the Niagara and St. Lawrence generating stations), contracted non-utility generators (gas), and wind.
The bulk of the production is nuclear and hydro, both of which have characteristics that are historically considered part of what makes a plant baseload, which is a big capital cost, and much lower operating cost.
Ontario's coal units, and much of it's gas, can be considered intermediate generation, which simply means it can have a generation profile that matches the predictable daily demand profile that rises in the morning, peaks at 5 pm on this particular day, and then declines until a sharp drop-off late at night.
Peaking generation is that which is available to handle sudden needs, which could arise from generators unexpectedly going offline or unexpected demand levels, and does now also arise from the presence of variable generation, the wind and solar 'renewables', on the grid. Much of the hydro, gas, and coal generation is peaking, and intermediate supply. In the first graph, the orange line (CF @ 3 am) is a good estimate of baseload components of hydro and gas/oil, with the gap between the orange and green lines indicating the demonstrated ability to ramp up output to meet demand (as intermediate and peaking supply). Using hydro for peaking likely lessens the production, while increasing the operating costs, for hydro turbines. Figures from Germany and Ontario both point to the likelihood that increased peaking duty is leading to decreased hydro output.
Which leaves wind; on this day producing 1163MW at 3 am (the HOEP market valued this at $10.60/MWh), and only 431MW at the peak demand hour of 5 pm (HOEP $38.36). This may seem like a cherry-picked example, but the output at peak here is actually far higher than what the system operator expects for the wind turbines, which is only 230 MW (page 96 of the NERC 2012 Summer Reliability Assessment)
Some are now referring to wind generation as baseload because the fuel doesn't have a cost, and general operating costs are low, while the initial capital costs are high. I'd suggests that it's frequent behaviour of output moving in the opposite direction of demand makes it inappropriate to use any of the traditional terms we slot generators into.
Considering wind generation's detrimental impact on the other generators in the supply chain, demands on the transmission and distributions systems, and the significant issues posed to markets, in it's fickle, demand agnostic, fashion of generating energy, I think it's clear it should be put in a new category within Ontario's generating system: