[bryanlarsen]

Alberta isn't very cloudy in the wintertime, the reduced insolation is mostly due to lower angles and shorter days. AFAICT, winter sunshine is more than a third of summer sunshine in Alberta. In Europe the number is often 10%.

It's cheaper to size production for winter sunshine than to build a lot of storage. AKA it's cheaper to put down 3X as many panels than to build seasonal storage.

Alberta doesn't lack for hills, which is what's needed to build pumped storage which is what's cheapest for seasonal storage.

[pfdietz]

> It's cheaper to size production for winter sunshine than to build a lot of storage.

Which means enormous amounts of surplus power in the summer (even with PV angled to optimize winter production.) So storage doesn't have to go far to be worthwhile, and in particular with nearly free input energy it doesn't have to be very efficient.

[bryanlarsen]

It doesn't have to be very efficient, but it is has to be cheap. Batteries aren't cheap but they discharge every night so their cost is spread out over ~365 days and their cost becomes feasible.

Pumped storage is ~10% the cost of batteries, but if used as seasonal storage so they only discharge once per year that makes them ~36X as expensive. Especially in Alberta where they're competing against Natural Gas which is also approximately free (it's often flared off as a waste gas from oil wells rather than captured and sold because the value is less than the cost of capture).

[pfdietz]

For seasonal storage, it would be either an e-fuel (like hydrogen) or bulk storage of thermal energy (basically, artificial geothermal). The latter could produce very hot rock at rather shallow depth, yet still have thermal time constants of many years.

[bryanlarsen]

Both of those are more expensive than pumped storage.

[pfdietz]

This depends on the time scale. For days or weeks? Pumped hydro is better. But for seasonal storage? The size of the reservoir becomes prohibitive.

[bryanlarsen]

A water reservoir is a heck of a lot cheaper to make large compared to a hydrogen tank.

[SketchySeaBeast]

I like this idea, but I disagree with this:

> It's cheaper to size production for winter sunshine than to build a lot of storage.

This still doesn't work - storage is mandatory. Winter peak loads, which are often the most power that the grid will require all year, are before and after the sun.

[adrianN]

There’s a huge difference between load shifting a couple of hours and seasonal storage

[SketchySeaBeast]

That's why I didn't specify it needed to be seasonal, but it does need to be stored, as a lot of that load isn't shifting. At 7pm on a -35 day there is zero solar generation, but every furnace in the province is on and people are doing their evening cooking and cleaning.

[bryanlarsen]

You're right, you said "as much storage as production". That's actually a very tiny amount of storage. Generally a "24hr" solar plant for California usage patterns has about 4-6Wh of storage and about 1W of discharge per watt of solar plant. Alberta will likely need ~2X that for daily load shifting during the winter. Seasonal storage would require a couple of orders of magnitude more.

[SketchySeaBeast]

Ah. To clarify, when I said "as much storage as production", I meant focus, not quantity.

[Marsymars]

I'd note that actual -35 days are pretty rare. Per Environment Canada Climate Normal Data from 1991 to 2020, Edmonton averages only 2.5 days per year with a minimum temperature below -30.

[SketchySeaBeast]

While you're correct, they do happen and need to be accounted for, and temperatures in the -30s in general aren't rare, but we're also experiencing more extreme weather as of late. Edmonton set a few records for cold the last few years, and those moments, when the grid is at the most strain, is also when the power is needed the most to keep people safe.

[jfim]

> Alberta doesn't lack for hills, which is what's needed to build pumped storage which is what's cheapest for seasonal storage.

From what I understand, BC has a lot of hydro dams. I wonder if there is a way to use them for pumped storage.

[SketchySeaBeast]

They do use them as storage, but more passively - When others sources of production are high BC slows their consumption, allowing them to build up greater reserves in their dams.