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Comment by michaelt | Hacker News Reader

  What percentage of our 
  global storage needs do
  you believe are "long
  term" in this dichotomy?

Solar output in the UK varies substantially between summer and winter [1] - as does demand for heating.

As a Brit with solar panels, it would be super neat if I could generate power during the summer, store it for 6 months, and use it for heating during winter.

That would reduce my direct carbon emissions relative to the status quo, which is burning natural gas for heating during winter.

However, replacing my (fairly modest AFAIK) £222-per-year gas bill would need ~150 Tesla Power Wall packs, costing several times the value of the home being heated.

[1] https://pvoutput.org/aggregate.jsp?p=0&id=4768&sid=3764&t=m&...

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https://en.wikipedia.org/wiki/Power-to-gas is probably feasible for consumer energy use (at least for people with room for solar panels). We have the facilities to store and distribute the gas already, and to the extent that additional storage would be necessary, it is fairly economical.

Replacing industrial and shipping energy with renewables is a bigger problem.

> store it for 6 months, and use it for heating during winter.

I wonder when we will get high voltage transmission systems between the northern and southern hemisphere? Actually solar farms in Southern Spain, Morocco or Arabic countries would make more sense.

Also seasonal thermal energy storage does that. Avoids solar electricity altogether, although has other limitations.

https://en.m.wikipedia.org/wiki/Seasonal_thermal_energy_stor...

Another "paradigm" is that full and empty batteries are shipped between regions by boat or truck as needed instead of just waiting 6 months for the planet to move through the cosmos.

Whew, that doesn't sound feasible, but I'd love for someone to do the math for me. It seems much more realistic to build HVDC lines from equatorial regions to the temperate zones, but even that is not very popular anymore as far as I know due to cost and NIMBYs.

I haven't done the math either, but I've seen serious discussions of it.

It requires zero infrastructure investments to load a hundred Tesla batteries on a truck and drive it to place with a different climate situation.

Compare that to long distance HVDC lines, which for the US are desperately needed, have been discussed for decades, and show no signs of ever getting built.

A HVDC transmission line might be a more practical way to do this.

For this, wouldn't it be better to pump water onto the top of a bunch of mountains in Wales?

https://en.wikipedia.org/wiki/Dinorwig_Power_Station, but more.

That's the point, isn't it? Batteries are not a panacea for energy storage needs, even with a doubling of their capacity.

There is no requirement for a panacea or super neat developments that allow individual households to store seasons worth of privately generated electricity.

For seasonal and sporadic production shortfalls in solar and wind generation, biofuels and electrically synthesized fuels can fill in. On the occasions where carbon-neutral fuel resources are insufficient - gas generation can remain as fallback (increasingly rarely) until sufficient carbon neutral fuel production is developed.

And with atmospheric CO2 capture, CO2 released by intermittent fallback fossil combustion can be scrubbed at a rate well below the peak release rate at the turbines.

Pumped water does not scale well, there are only so many mountain valleys to block. And I'd rather keep a few in a somewhat natural state (a magic "no more mountain valleys in exchange for instantly solved climate change" would be attractive nonetheless, even though I write this from a very nice, unblocked mountain valley).

But when your concern is just seasonal storage for heating, you don't need pumped storage. Just great water in a big, isolated tank, it's not even new technology. The surface per volume shrinks the bigger the system, so very large tanks can have quite nice loss numbers.

Actually, there is enormous potential capacity for pumped storage around the world.

Pumped hydro is generally used for diurnal storage. The infrastructure of the dams and turbines is darned expensive; it makes practical sense if you're filling and draining the basin (or half of it) every day, but paying pretty much the same cost to get just a single lake volume per year ... not so much.

The entire UK energy use is about 2% of the world total. So I'm guessing that the storage needs of your specific (and oddly non-grid connected) home is only a small fraction of that and doesn't affect the larger, global, back of the envelope figure I'm looking for.

Using numbers to quantify the situation is part of why I'm asking, asking (and answering) the right questions so we don't get silly answers is the other important part though.

Having short days in the winter, long days in the summer isnt a UK specific thing. As you get closer to the equator it may become less of a problem as summer air con load overtakes winter heating as the dominant load, but we are talking about large swathes of the planet that will have higher heating demand that can't reasonably be covered by solar power alone.

If you could put some kind of number on how much of a not-UK thing it was on a global scale, that would answer my original question.

Like, apoarently air con is currently 10% of all electricity and set to grow. 10 AC units will be sold every second for the next 30 years.

It seems solar plus batteries has that covered, but I'd be interested to know the ratios.

According to this [1] it looks like about a third of energy used in commercial and residential buildings is for space heating. That only accounts for some 32 Pwh of 157Pwh [2] of energy use but is greater than the 21-23Pwh of total electricity generation.

So judging by your figure of 10% of electricity usage that's 2Pwh (10% of 21-23Pwh) for air con v 10Pwh (third of 32Pwh) for space heating.

But that energy demand is mostly based on combusting fossil fuels directly, decarbonisation would require a move to electric heating which would probably involve heatpumps, and quite a lot of insulation, so I would hope that that figure would drop quite alot in the future.

[1] https://www.sciencedirect.com/science/article/pii/S136403211... fig 3.

[2] https://en.m.wikipedia.org/wiki/World_energy_consumption

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