Much has been written about how Ontario is going to meet its growing electricity needs. Renewables often come up as a potential solution, and, to put my money where my mouth is, I am hoping to put some solar on my roof. But, renewable by nature are intermittent, hence storage, in some shape or form, is an essential component of any renewable strategy. My home battery system for example, works well for a few hours, perhaps a few days with modest expansion, but my energy needs vary greatly by season, heating even with an efficient cool climate heat pump, is energy intense. However, rooftop solar productivity is great during the summer thing. So what can we do to address that problem? Well, a few things, first is to leverage the grid, second is consumption patterns, then there is just overbuilding your solar array, and lastly Hydrogen.
The grid is arguably the simplest solution. As Ontario, electricity demand is typically “summer-peaking”, with air-conditioners humming. Anyways, this is a simple enough concept, simply export your solar power, which is ample during the warmer months, during the winter months when your heat-pump might be working, import. This works well if the grid is flexible enough to either take your excess solar, or provide the needed electrons on a cloudy day.
Some power-plants are flexible enough, others are not. Nuclear is not very flexible (source), and likes to operate at near 100%, while gas-plants can usually be throttled up or down depending on demand (source). Hydro is generally considered to be fairly flexible, while some run-of-the-river hydro plants might be less flexible, others often operate like “pumped-storage” stations (source). Here in Ontario, about half of the grid is powered by nuclear, while the other half is split between hydro, gas and wind. Thus there is at the time of this writing, some flexibility in Ontario’s grid, although if solar continues to gain popularity, that might change (source).
Then there is consumption. If the gird needs more electrons during the summer than the winter, perhaps storage is not really a problem. Oil financial gurus have something called the “summer-driving-season”, as people tend to drive more in the summer than the winter (source). So perhaps solar is a good match for our energy needs, after all, air conditioners are also a summer time thing, and have historically been a heavy load on the grid.
Third is hydrogen. With electricity and water, you can make hydrogen, which can be stored in tanks for months at a time. The hydrogen can then be passed through a fuel cell when needed to generate electricity (source). Its worth noting that round-trip efficiency is only about 40 % (source), which is much lower than the 89% efficiency quoted for my powerwall (source), but on the other hand, a tank might get me week or so of power for my home (source), compared to several hours for my powerwall.
Lastly, there is also, just overbuilding your solar array for a cloudy day. On a dark wintery day, your solar array might produce perhaps 10-25 % of what it does on a summers day (source). Thus, why not add some panels to areas of the roof that see brightness during a cloudy day, for example my North facing roof gable, some of my garden fence etc. That coupled with a battery system might be all one needs. This interestingly, might be the least expensive option, as solar panel costs are quite low by historical standards (source), at $3 000/kW installed, it might beat out hydrogen.
So, of the four contenders, which one is right for you? I suppose this all goes down to your situation, and they are certainly not mutually exclusive, all four might work well in combination. For me, living in Toronto, I do have a small home battery, but I am considering over-sizing my solar array, mostly as it might be a better option than adding to the home battery to cover a winter’s day. As I do have an electric car, we could use excess solar to charge it, or perhaps its better to export that excess solar, and charge at night, after all, on the ultra-low overnight rate, a kWh during the day, might buy two or three at night.
Electric car adventures 