[_aavaa_]

It’s hard to say it’s optimal to build a whole hydrogen/ammonia production and distribution network to capture some excess energy.

Those things have serious costs, and that time and money could be better spent on a problem that is more important to solve. Again, that energy doesn’t cost anything to produce.

Don’t confuse optimal with maximal.

> decades of experience.

Yes, and the first rule of safe design is to not use toxic or harmful chemical if you can avoid it. And in this case we can.

[tpm]

> Don’t confuse optimal with maximal.

I'm not, we won't be able to utilize all of installed PV when it's producing max power. Currently at around 300GWp yearly added capacity and rising. But also I'm not saying hydrogen/ammonia production and storage is the only option we have. I just don't see many others.

> And in this case we can.

Sure we can. How?

[_aavaa_]

> Sure we can. How?

By not making ammonia.

> we won't be able to utilise all of installed PV when it's producing max power.

I don't see that as a problem. Underutilised it will extend it's payback period, but they are already so cheap by comparison to any other option. There isn't a startup/shutdown cost, and there isn't an operating/fuel cost (the sun shines and the wind blows for free).

We should be focusing on adding storage for cases when we may not have it in the future, and not because we have more than we need now. If we have more than we need now, that's not really a problem that needs solving. Take the money we'd spend on that and build more renewables; there's still plenty of places in the world (US included) that are still burning coal. Taking those plants offline is a bigger win than storing excess energy that we get for free (minus a longer payback period on the equipment).

So before we talk about storage, I'd argue for 2 changes:

1. Simply overbuild the hell out of solar and wind. Build it out so that they handle the winter demands, the price is already so low, and in the summer when we have all that excess energy we won't have to worry about storing it for later.

2. Change usage pattern. This is both a supply and demand problem. People already are used to not running their dishwasher/laundry during peak times, "peak times" will simply change. So if you have a lot of solar and wind, you'll want to do those at noon rather than at night. Same for other high energy draw activities.

Storage will depend on how long you need it in the future, and what you will use it for.

- Heating and cooling short term: Use thermal storage to store "heat" or "cold" then pull from that during the rest of the day as you need it. Think water heaters, bricks for heat storage, or phase change materials for "cold" storage.

- For short term there's batteries (for a great payback period see Hornsdale Power Reserve).

- If you have hydro, or are connected to neighbours which do, change how that's operated (it's only at ~40% capacity) so that you store the excess green energy in them, and run them when solar and wind go offline.

- Build pumped storage between two artificial basins (cover them with solar panels to help with evaporation).

- And worst case, you end up in a situation where you have to turn on some natural gas peaking plants to cover a shortfall. But if we get to the point where potentially running a fossil fuel peaking plant is the biggest of our concerns, we have won 99% of the battle.

[tpm]

> Take the money we'd spend on that and build more renewables; there's still plenty of places in the world (US included) that are still burning coal. Taking those plants offline is a bigger win than storing excess energy that we get for free (minus a longer payback period on the equipment).

> Simply overbuild the hell out of solar and wind. Build it out so that they handle the winter demands

How do you propose replacing coal with renewables without storage? Here in the EU, in winter there is no way to power national grids from PV (with the possible exception of PIGS) and a few landlocked countries can't have enough wind power (also often the wind just does not blow enough even for offshore production). Currently there is a mix of sources including coal, gas, nuclear, hydro, biomass etc. There is also a strong national bias so even as a small country you can't be completely dependent on other countries for power.

> So if you have a lot of solar and wind, you'll want to do those at noon rather than at night. Same for other high energy draw activities.

Or we could power night activities with the PV from west, but there is only Morocco/Western Sahara and then the ocean. But people still want to cook food and watch TV in the evening and they will not change that, so we will need short term storage. That's probably not even an big issue though.

> Build pumped storage between two artificial basins

We do have a few here, here is the biggest one: https://sk.wikipedia.org/wiki/%C4%8Cierny_V%C3%A1h_(vodn%C3%...

it's impressive, but also easy to see the limits: you need suitable geology and geography and without that can't reach sufficient capacity.