The maximum capacity of power plants is designed so as to meet the demand during the hottest days of the summer or coldest and darkest days of the winter. Other times a good amount the surplus energy generated by non-controllable plants is just wasted.
There are organizations such as BC Hydro's Powerex that trade electricity on a minute-by-minute basis. They buy "surplus" power from marginally controllable sources such as thermal plants in the US and Alberta - cheap - and "store" the equivalent hydro power behind BC's dams. Then, when the US needs peak power, Powerex has power generated using the stored water and sells the power back to the US at a nice markup. There are many organizations comprising thousands of people throughout North America engaging in this real-time, round-the-clock trading. (In fact, on rare occasions US generators have PAID Powerex to take power, so they don't have to temporarily shut down thermal generating units.) See FERC and NERC.
So, with dams in the grid, there is no need to "waste" electricity, and other than the most marginal circumstances, it just doesn't happen. In the same sense, there is not "surplus" generating capacity. Why else would there be so much drive to both conserve electricity and build more power plants? It also should be mentioned that some of these dams, such as the WAC Bennet Dam, contain multi-year supplies. So in that sense there is always capacity to store more water so that no power in the grid is wasted.
BTW, using hydro as a buffer for non-polluting sources such as wind and solar defeats the purpose of those new energy sources.
While I readily agree hydro has severe environmental impacts, do you know how much resources it takes to make those huge windmills and semiconductors? Apparently it takes as much energy to make 10 pc's as to make a car. Vastly better than coal/nuclear plants, of course.
First you said "Unpredictable sources like wind and solar mean very little to the grid unless there are means to store the energy they generate." Now you're saying that using hydro as a buffer defeats the purpose of wind and solar. Can you elaborate on that? I think they couldn't complement each other better. Yes, batteries also act like buffers, but massive implementation batteries has a substantial cost. I bet the impact is greater than storing water, for instance.
In my opinion, the chart you provided a link to does not show generated power vs power used (demand). I believe it shows generation potential against load/demand. It said the green line is "available resources forecast". This is useful to plan ahead to avoid brownouts. Such as knowing ahead of time when you might need to buy power from Powerex, so you can arrange a contract and avoid costly last-minute purchases. If I am correct about the chart, it means it is not proof there is vast wasted electricity. It means there is CAPACITY, but you have to burn coal etc. to get the electricity. I expect there are similar charts for longer timeframes, and even shorter ones.
IF California had such a surplus of electricity as you claim the graph proves, then they'd be pretty stupid not to sell it to someone else, or open a bunch of aluminum smelters.
The granularity of the green line representing capacity, also demonstrates that by managing different sized units at numerous thermal plants, there is extremely fine tuning of the amount of power generated, thus minimizing waste. Waste that can always be sold to the dam owners, of course.
The extra capacity you see on the graph is needed for peak load. In California, peak load happens on the hottest summer days, to serve air conditioning. At those times, the existing generation is fully used, and places like BC have to backfill places like California by using more water from dams to generate more power to sell to them. I leave it to you how electric cars will be charged up during peak load.
There certainly is a cost to the excess capacity that has to be built into the system to meet peak loads. But because of their varying characteristics, integrating via the grid: thermal, nuclear, hydro, wind and solar sources allows minimizing the size and capacity of the thermal (coal/gas) and, hopefully, nuclear plants. That's the main reason why grids exist.
I think we agree that electrifying transportation is an excellent idea. But there's a fly in the ointment. All clean/renewable power sources are fully utilized. There is no spare "clean/renewable" capacity. Any gap between capacity and demand on clean/renewable power is used to displace "dirty" sources like coal and nuclear.
This means that any new demand, such as electrifying transportation, can only be met by thermal and nuclear generation; or more dams, wind and solar sources. Except at peak loads, when there is no spare capacity. And this means that unless increased demand by electrified transportation is met only with increased hydro/wind/solar or conservation, electric cars actually are powered by coal and nuclear. Not what we had in mind.
Now it's not fair blame electric cars for that, other than that they would be a new demand. It may mean that adoption of electric cars and their demands on the power grid have to be matched with gains in clean generation and electricity conservation. This combination will require a MASSIVE amount of capital, and I just don't see the public sensing the urgency with which we need to do this. Not to mention being in a capital squeeze already.
20 years ago I warned some managers at a large provincial utility of the problem posed by electric cars (and of the threat to hydro generation resulting from glaciers melting), but of course I sounded like a lunatic then.
Now it's time to ride my bicycle home. On nasty days, I commute on the electric-powered, linear induction motored, driverless, regenerative-braking, scenic, Canadian-made SkyTrain.
