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Comment by Manuel_D | Hacker News Reader

Comparing levelized cost of energy between intermittent and non intermittent sources is comparing apples to oranges. The reality is that until some fantastic storage system comes along that makes storage effectively free, intermittent sources cannot provide a path to decarbonization.

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You're making bad future assumptions about wind/solar.

What is impressive to me is that wind/solar are now beating the best LCOE "old power" scheme (gas turbine)... and they are not done dropping in cost. There are a variety of future economies of scale and advancements yet to come that will drop them even lower.

When they drop low enough and batteries get cheap enough, then yes, effectively batteries are "free" because battery+alt energy is cheaper than any other dirty alternative.

I would guess in 5-6 years we'll have a convergence of ultracheap wind+solar and good-enough sodium ion batteries that no existing nuke design or fossil fuel can beat.

There's nowhere near sufficient battery supply to make intermittent sources viable. Annual battery output amounts to less than 15 minutes of global electricity consumption, and an even smaller fraction of total energy consumption. Inputs to batter manufacturing like lithium have sixfold since 2000: https://www.metalary.com/lithium-price/

We do not need a "fantastic" storage system. Ordinary dirt-cheap storage will do fine. Batteries are the most expensive alternative.

Of course it would be stupid to build out storage until after there is enough renewable generating capacity to charge it from. In the meantime, money is overwhelmingly better spent pushing toward that goal.

When the time is right to build out storage, it will be very cheap, as storage cost is falling faster than solar ever did.

And what system will provide this "ordinary dirt-cheap storage"? It'd be helpful to actually specify what you're proposing.

Furthermore, some energy markets have seen saturation during peak production hours of intermittent sources for years now. But this unspecified dirt-cheap energy storage isn't being built to capture and resell this energy.

This "ordinary dirt-cheap storage" is precisely the fantastic storage system I'm referring to. Plans for a primarily renewable grid assume that some breakthrough is going to happen in order to make storage dirt-cheap.

Or, maybe they are not stupid, and recognize the excess is because the gas plants cannot be shut down and restarted fast enough, and there is not actually enough renewable capacity yet to charge anything much.

Until there is a lot more such generating capacity, it would be stupid to divert capital from building that out to building only minimally useful storage.

Gas turbines can be rapidly activated and deactivated, they are not the cause of excess production.

Again, what is this "ordinary dirt-cheap storage" technology? Sure, you say it's not going to be built until there's an even bigger energy surplus. But at least just specify what technology is going to provide this dirt cheap storage. Because I'd really want to know. All of the alternatives I know of like compressed air, hydrogen storage, ammonia storage, all have significant drawbacks impeding cost effective deployments.

> there is not actually enough renewable capacity yet to charge anything much.

What is this trash? Excess solar output is already an enormous problem. https://www.latimes.com/projects/la-fi-electricity-solar/

You may pretend, of course. But any solar farm producing enough power to be a "problem" may simply be shut off.

And, an occasional excess, a few hours in a few days out of each month is not the same as enough to usefully charge storage.

Also: 2017.

I always wondered if some sort of "closed loop fuel" model was viable.

The appeal of conventional fossil fuels are high energy density and well established tech to convert it back to useful energy.

What if we had a station with some tens of thousands of litres of petrol sitting around. When the grid is strained, we burn the fuel, but in a generator carefully engineered to capture all waste. When renewables exceed demand, we use the available cheap energy to distill the waste back into burnable petrol.

Now, obviously "petrol" and "generator" can be replaced with other options to optimize performance or economic viability (maybe it's hydrogen and a fuel-cell rather than petrol and a generator, but I'm not sure if those are actually working at scale or just trotted out by Toyota to distract from them being late to the EV party)

It probably wouldn't be hugely efficient (the distilling would consume more energy than burning ever generated, after all), but it could be a way to handle "I'll pay you tomorrow for a hamburger today" with more flexibility on siting than, say, pumped hydro.

I suppose the big question is how tight the closed-loop can be. It's not a winner if you end up losing 1% of your fuel stash on every daily cycle.

Essentially you're proposing capturing the CO2 emitted by fossil fuel heat engines and converting it back to hydrocarbons using the Sabatier process. There's several barriers to this:

1. Capturing the carbon emissions. The exhaust if a gas turbine is a high temperature mix of air and C02. Separating out the CO2 requires either cooling it or a chemical process to capture the carbon dioxide. Both of these processes are every energy intensive.

2. The Sabatier process needs a source of hydrogen. Typically this is done through steam reformation, but that emits CO2. Electrolysis or thermochemical water splitting needs to be done instead, and these are both energy intensive and expensive to do.

3. The Sabatier process itself also requires energy, as it's putting the carbon in a higher energy state.

It'd probably be easier to just use the hydrogen in step 2, but that's still a difficult undertaking that nobody has done cost effectively as of now.

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