> make synthetic fossil fuels from atmospheric CO2.

that would actually be my preferred solution (if only it was less energy inefficient, sigh).

chithanh 3 hours ago | parent | next [-]

The problem here is that the production of hydrocarbons, ammonia, etc. from electricity can only make back its high upfront investment when it runs basically 24/7. This is a challenge for renewables.

In China which recently opened a large off-grid green ammonia plant in Chifeng, they use multiple tiers of energy storage to ensure constant electric power availability.

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elzbardico 5 hours ago | parent | prev [-]

If the marginal value of electricity is negative, what matters if it is energy inefficient?

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lazide 5 hours ago | parent [-]

Scale/quantity.

That ‘negative value’ electricity could also be used to do something else. And actually requires a lot of capital to produce. It isn’t actually free, it’s a side effect of another process that has restraints/restrictions.

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chithanh 3 hours ago | parent [-]

It has a negative price precisely because at that given moment, nobody can use it for anything else.

	▲	lazide 3 hours ago \| parent [-]
		Yes…. And capital costs to capture that ‘moment’ productively are likely not in favor, if this situation exists long term. For example, Free power for an hour is useless if someone is running an aluminum refinery, because you can’t just start and stop it; and it costs so much capital to make that only operating 1 hour out of 24 is not economic. And that is for a situation where electrical power costs are one of the most dominant costs!