[_aavaa_]

We should be so lucky as to have so much excess energy to throw away freely of green hydrogen.

But that future is nowhere in sight.

For starters we currently have 90 million tones of H2 that is made from fossil fuels. We should focus on making that green before we consider NEW use cases for it.

As for what to do with the excess energy:

1. Store it in hydro 2. Make water.

#2 is real informative. To make 1 kg of H2 you need ~9kg of pure water (let’s call it 10 for simplicity) and 50-65kWh of electricity. To make those 10 kg of water by desalinating seawater you need 0.035 kWh.

So instead of creating 1 kg of hydrogen, we could create 13,800-18,000 kg of pure water.

Given all the water problems we’re having, that might be a smarter use of that energy.

[tpm]

Every time the spot price goes to 0 or less we are throwing energy away. This is already happening. Every time we could be instead generating hydrogen, or desalinating water, whatever we are not doing right now. But with the ensuing enormouos rise in PV and wind this will get much much worse. Eventually something will use that energy. Why not generate supply for the time when sun is not shining? I don't really care if it's hydrogen, ammonia (easier to store) or pumped hydro (probably best, but not enough capacity possible) or something else.

Also not every country has access to sea and while here in EU the energy markets are interconnected, it's not perfect. And some countries have enough water, no need to desalinate.

[_aavaa_]

The difference is that energy prices don’t go below 0 for solar. They go below zero for coal, gas, and nuclear since you can’t shut the plants down on a whim. But you can with solar. You aren’t throwing energy away by turn off panels or stopping turbines, the wind blows and the sun shines for free, whether or not we capture it. The concept that energy price can go negative only comes into the picture because of things like gas, coal, and nuclear where we have to active produce heat to turn into electricity.

As for ammonia being easy to store. Yes, but only compared to hydrogen. But now you have a highly toxic gas. And, creating ammonia from hydrogen is another extremely energy intensive process.

[tpm]

> But you can with solar. You aren’t throwing energy away by turn off panels or stopping turbines, the wind blows and the sun shines for free, whether or not we capture it.

We are throwing away the electricity that would be created if we could use it at the time. So, in the name of optimal utilization of resources, we should be using it.

> But now you have a highly toxic gas.

Working with which we do have decades of experiences.

[_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.