Comment by gumby | Hacker News Reader

Comment by gumby | Hacker News Reader

Parent Full thread

My problem with seasonal isn't the duration itself (though that's a challenge too). But if you're trying to shift seasonally you need not just storage duration but volume-duration too.

That is, let's hypothesize a house uses 24 kWh per day, roughly the magnitude in California, 365 days/year (AC in summer, heating in winter). Power is from solar and wind.

If you look at "duck curve" demand, you need a bit extra in the afternoon / early evening when there is higher A/C demand -- you can scavenge a bit more power in the morning (say 5 AM to noon) and discharge it in the afternoon (when the solar flux is high BTW), then do the same trick tomorrow. Call it 5 kWh. That's all the storage you need: a relatively small amount for a few hours.

Could you hold that 5 kWh for four months? Maybe. Maybe you need to store 7 kWh to get 5 out four months later. Only it's not just 5 kWh for four months: that's 120 days of needing your storage, to produce 600 kWh...on a battery you then don't use much until next season.

And that's just for one house. I don't see how seasonal long term storage works, except in a few weird corner cases. Maybe you store it as something else than protons, like methanol. But if you can build a better grid I suspect it's still better to export power from the Mojave to Bangor and the Mahgreb to Helsinki.

I am glad someone is thinking about this though!

Residential in general indeed isn't much of a concern. That can - even in Germany - be done by solar, wind, battery backups and geothermal.

The more pressing problem is industry, which makes up about 44% of our electricity. Some processes, e.g. metal and glass smelters, absolutely require years of uninterrupted power supply or need dozens of millions of euros and months of downtime to get repaired. Some, like electric-arc aluminium smelters, can handle a short-term load disconnect and receive a premium on their electricity prices for that. The utter majority however could in theory be suspended and resumed at will, adjusting to market prices and stability requirements... but the owners don't like that uncertainty and workers don't like it either because they wouldn't get paid.

Other large consumers like city lighting or advertising could in theory also be shut down or reduced during peak demand times. But as we've seen in the winter following the Russian invasion of Ukraine where that was outright banned by an emergency decree, this is politically untenable - people have grown so accustomed to the luxurious energy waste that they're (literally) willing to kill over it.

It's very interesting. I wonder what exactly was banned that winter?

Quite a bunch of stuff, the full law is here: https://www.buzer.de/EnSikuMaV.htm

Most important, no keeping open of store doors that blast people with warm air, no illuminated advertising of any kind between 2200-0600, no exterior lighting on buildings and structures that was not safety-critical (i.e. escape paths, flight safety), temperature control limitations for non-residential buildings, and swimming pools were shut down completely.

Thanks!

> That is, let's hypothesize a house uses 24 kWh per day

We're at approximately half that and it still isn't a tractable problem just for a single day, for the 1st week of January we used 88 Kwh and made 18.7 Kwh in solar, about 7.5 of which went to the grid (so would have been available to charge a battery). We'd need 4 times as much solar to get through the days and even then there would be days when there wouldn't be enough to go around. Making that work for a week would require 70 KWh of storage and a nameplate installed solar capacity of about 60 Kw, well into fantasy territory, it would never make sense from an economics perspective to set that up. You're looking at 150 to 200 panels depending on type, massive power infrastructure (your normal hookup will not even be close to enough for this) and a formidable array of batteries for storage.

It won't happen locally for that reason, much as I would like to. The only thing we can do is to try to conserve even further but we're already close to what you can do with four people in one house, approximately 3 KWh / person / day, especially in the winter. Transporting that power from the excess in the summer would be an even more impressive feat. We still have 11 months of netmetering and then that's over.

I don’t think any meaningful storage makes sense for a home, but for a grid-attached solar plant. The surface area is large but I think the cap ex (and naturally the op ex) are naturally much lower.

Even if the solar plant doesn’t generate enough in the middle of summer when demand is high, its grid connection means the batteries could be charging from surplus wind at night.

Not that this addresses my time-volume issue, just saying it’s not worth considering from the single home perspective except in unusual cases.

I'm hoping for HVDC both across both large spans of longitude and lattitude, that would be a game changer. There is plentiful solar, all we need to do is to be able to transport it across the planet to wherever the sun currently isn't shining.

'A mere matter of engineering'. But we do have that capability.

I think seasonal underground thermal storage is most interesting for somewhere like a remote community up near the Arctic Circle; away from grids, high seasonal variability in generation, etc. I don't think it's ever gonna be how you, say, run the whole European grid; there, a large geographic range of interconnected grid is more likely to be the answer. Cloudy in Germany? Spain's fine.

Thermal storage is hamburger, hard to re-use, hard to transport. You need electrons.

Reply on news.ycombinator.com