[ben_w]

Can also make sense if this is cheaper than batteries.

Electrolytic hydrogen is so easy I did it when I was nine years old — the only reason I powered the reaction using a battery instead of PV was that back in 1992, PV wasn't something a kid could easily get hold of with pocket money.

[gefhfffh]

Well, short term it may be cheaper. Long term you are going to pay, because the efficiency is horrible, 10-30% depending on who u ask

[ben_w]

PV is so cheap the efficiency is the least important part of this.

PV without batteries is the cheapest power source on earth, bids in the order of single US ¢ / kWh, but last I saw batteries had LCOE comparable with nuclear reactors (about 15¢/kWh in 2020).

I’m certainly hopeful that batteries will improve, but right now even a mere 10% efficient process for turning electricity into gasoline and then burning it is still useful as both heating and aviation fuel, and just about on the edge of useful as strategic diversity for nations that don’t want to limit strategic energy storage to just batteries.

[gefhfffh]

PV needs physical resources that aren't for free or unlimited. PV needs space. Most energy used has still an high negative impact on the atmosphere. Low efficiency somewhere is energy potentially wasted that could reduce carbon emissions somewhere else.

Heating is waaay more efficient with heat pumps. Aviation... Well who can still afford it...

There are other forms of storage as well, e.g. hydro, heat storage, and many more

I'm not saying it doesn't have it's uses, but efficiency is important

[ben_w]

> PV needs physical resources that aren't for free or unlimited. PV needs space.

We have about 10,000 times as much space as we need for a pure-solar economy at current power use, 1,000 times what we need if we raise everyone to the power use of the average American, but still better than 100 times what we need if we want to do that while having a 10% efficient storage system because most energy is used while the sun is up anyway.

> Most energy used has still an high negative impact on the atmosphere.

Yup, and will do until it’s renewable. If it was already renewable, using that power to make more renewables has no impact whatsoever.

> Low efficiency somewhere is energy potentially wasted that could reduce carbon emissions somewhere else.

Sure, but the ideal is a global superconducting grid, and even if you do that the easy way [0] we’re a long way from the necessary industrial base to get it done.

This option is sufficiently good to be interesting in the meantime.

[0] a ballistic superconductor, specifically a charged non-conductive ring in orbit.

Second best option: a few square meter cross section HVDC cable encircling the planet, which needs quite a big investment in mining to get the materials for but has the advantage we can get most of it done gradually just by continuously upgrading existing grids until the very last step of crossing the Atlantic and/or Pacific.

[danuker]

> Heating is waaay more efficient with heat pumps.

Absolutely.

With electricity you can power heat pumps (which are say, 5x more efficient than resistive heaters), but by synthesizing fuels with electricity, you can get strictly less than a resistive heater's equivalent energy.

[Ourgon]

> Aviation... Well who can still afford it...

Oddly enough (but not really that odd) it seems to be affordable to a lot of people who jet around the globe to tell each-other and the media that people need to fly less, for the climate. It used to be for the environment but that trope seems to be worn out.

[marcosdumay]

> because the efficiency is horrible, 10-30% depending on who u ask

You mean the electrolysis efficiency? There are examples of up to 70% on the lab, but it was never economically important to optimize it.