If wind is treated as ‘must take’ then it ought to be treated as negative load. The net load for the schedulable generators is then
Net = Actual – Wind
Baseload therefore refers, initially, to demand. The first graph shows baseload as the minimum daily Ontario demand. Between 2005, and 2011, the minimum dropped -on average 1574MW. That, coincidentally, is about the capacity of nuclear supply due to return as Bruce 1 and 2 return to service (I think the contracts were negotiated in 2005).
Baseload supply generally refers to supply that is to meet this minimum demand - which would be the base load. It is usually expensive to build, and cheap to run; that means nuclear, but it can also mean hydro, combined cycle gas generators (CCGT), theoretically with carbon capture - the same for coal plants, etc. In general the characteristics are large capital costs and lower operating costs (MIT recently published this on the impact on existing generators from increasing renewables). Baseload supply did serve to reduce the amount of peaking, or intermediate, supply that the remainder of the generation mix needs to meet demand. Wind especially, but also solar, do the opposite - they increase the daily swings in demand. To the rest of the generators, there are not only more accurately in the 'load' equation, they are the least predictable factors in that equation.
In Ontario, baseload supply was approximately: 2500MW of hydro (varied by season), 11000MW of nuclear - which was about right in 2005, and a number of natural gas (primarily) generators were contracted on a 'must take' basis, adding another 1000MW. Nuclear generator availability not being 100%, this was appropriate until demand drops accelerated. Until the deep recession of 2009, exports hid the excess capacity, but since then the term "surplus baseload generation' (SBG) entered Ontario's vocabulary.
I've gone back to the data set I built for an earlier series of posts, adding wind capacity to set wind at 8100MW, and I've also grabbed a sample data set for solar production in London, Ontario (the capacity factor is 13-14%), and set the solar capacity level to 2600MW. The graphs based on this data are projections of 2016 if all goes as planned.
The average is about 3000MW lower, and 7000-7500MW is probably a better estimate of what base load remains. With 2000-2500MW of hydro, and another 1000 of gas, the available room for baseload nuclear would only be 4000MW even if we assume no more load following generation would be required on the grid. The renewables target certainly devalues Ontario's investments in nuclear capacity - and it is likely to increasingly devalue Ontario's public hydro assets as they are enslaved to balancing privately owned renewables.
The graph demonstrates we do essentially need today's generation capacity, in addition to whatever renewables are added.
These things are known - although I'm not convinced the math had been done. The Independent Electricity System Operator (IESO) is busy developing a scheme paying renewable generators not to generate. That essentially pays them to inflate the load (as the production isn't subtracted from demand), in order for existing baseload to continue functioning. The Ontario Society of Professional Engineers is encouraging that initiative and urging more money be spent on making nuclear more flexible.
Nobody seems to be able to get the government to accept the obvious.
It's a lousy supply mix - and they are making it increasingly worse.