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Comment by therealrootuser | Hacker News Reader

Many have rightly brought up the issue of energy storage for solar. Could hydrogen fuel cells provide an answer here? I believe there is some fairly recent research describing efforts to use solar energy directly to produce hydrogen (as opposed to electrolysis).

One could imagine a system in which solar cells produce hydrogen and the hydrogen is stored until needed or sold to industrial or retail customers.

Interesting field to watch, I hope we'll see some neat progress in the coming years that combine developments from multiple areas of research.

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Using hydrogen as intermediate storage is interesting because it is a pattern that can be reused in many places. For example, I know of semi-experimental Chinese nuclear reactor that is used for making hydrogen rather than electricity. That could give you easily dispatchable nuclear power, which is much better, carbon-wise, than gas peakers would be. I don't know anything aboutthe efficiency and economics of such setup though.

There's however a possible political trap to fall into - most of hydrogen humanity uses cones from oil processing. So going there has not obly geopolitical ramifications, but we might also end upin a place where we're greenwashing oil to "clean hydrogen".

Battery EVs are being deployed by the millions per year and pretty soon tens of millions. If you assume an average capacity of 50kwh, 1 million cars is about the equivalent of 0.5 TWH of battery capacity. In comparison, fossil fuel (coal, gas, oil) based electical capacity world wide was around 4 TW in 2017. So, 8M cars could supply that for 1 hour, world wide. https://www.statista.com/statistics/267358/world-installed-p....

So, hydrogen might help but by the time it comes online, most countries will already have plenty of EVs on the road and plugged into the grid with more TWH of battery then they'll ever need to absorb fluctuations in supply & demand. And that's just cars that most countries currently haven't even started to take into account to use for this.

Also a lot of domestic rooftop solar are usually excluded from energy statistics. Apparently, in the Netherlands about 1 million households now have solar on the roof (on a population of 17 million). That's quite a lot of energy even though most setups are in the order of only a few KW. That's a couple of TWH/day of supply that is just being "overlooked". I bet the UK is not far behind on that front either. The cheaper that gets, the better it gets. This kind of decentralized supply of energy and battery capacity can provide a lot of resilience.

>One could imagine a system in which solar cells produce hydrogen and the hydrogen is stored until needed or sold to industrial or retail customers.

You would need to massively over-provision your solar deployment because you not only need to produce enough energy for current needs, but also to produce enough spare hydrogen to bridge the intermittency gap ... and it is incredibly inefficient to produce hydrogen via solar-generated electricity. Worse than that, you need to over-provision not just for daily load (i.e. night and peak), but for seasonal (summer vs winter) and inter-seasonal variance. All this means you have huge amount of infrastructure that most of the time is doing nothing.

I'm also not sure about the feasibility of using hydrogen as battery backup. Hydrogen is notoriously hard to handle, move and store - and the fact nobody is building out this infrastructure right now is probably indicative of this.

If you wanted to get by with only solar and hydrogen storage, then you would need to store a lot of hydrogen.

But fortunately, we also have wind, and a moderate amount of on-demand renewable power (hydro, biomass). To smooth that out, you need to store much less hydrogen.

Hydro is a great option ... as long as you have the geography for it. Biomass is an environmental disaster. You're destroying huge swaths of natural habitats so you can grow corn or whatever just to burn ... does that sound like technology of the future? Wind has the exact same problems as solar and buys you almost nothing.

Wind and solar tend to produce power at different times. The intermittency of wind + solar is much less than either alone.

They really don't. That's one problem.

There's one company that basically wants to use a crane as power storage.

Lift blocks when energy is cheap, use regenerative braking to lower them when it is not.

Earthquakes could be bad, but nowhere near as bad as a reservoir breaching. Rectangular blocks tend to stop rolling pretty quickly.

Most fields are now installed with a battery system on site. They are largely buried, so unless you watched construction, a field may have a large storage capacity without obvious infrastructure.

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