But one misconception I often read is that everyone focuses on batteries. It would make more sense in general to talk about energy storage instead of just batteries. Like Kinetic, chemical, thermal and so on.
Batteries cannot be solely responsible for back-up. You need different types of storage: short term, medium term and long term storage.
There are different concepts for each application. Batteries, compressed air storage, pumped storage, kinetic, thermal storage as well as power-to-X systems are able to absorb the increasing summer power and provide the energy again in the medium term or seasonally shifted.
The best energy storage form is "final form". Some energy products can be stored. For example if you are using the energy to create heat, you can store heat for use in the future. Heat storage sucks as a way to store energy destined for electricity, but is a great way to store energy destined for use as heat.
The utility of batteries for daily storage is obvious and well proven.
Thirdly, the best annual storage is pumped hydro. It's the cheapest and it can be used pretty much everywhere -- all you need is water at one end of an elevation change and a way to build storage at the other end.
All the other forms that you'd think would fit in between the two are being quickly subsumed by the rapid price drops in battery pricing. The cutover points are rapidly shifting -- batteries are now cheapest for biweekly-ish.
And the primary sources are getting so cheap that overbuilding is an alternative to storage. Rather than storing for the reduced amount of daylight in the winter, just overbuild. More overbuilding and a few days of storage will let you handle a stretch of cloudy, windless days in January. No annual storage required.
However, the point of the study is different, and that makes it still relevant today: The barrier to expanding energy storage isn’t a technical one—it’s a political one. The study also shows that there is a great deal of variability, and the often-used argument that there’s not enough lithium or rare earth elements doesn’t hold up. More recent studies validate different storage technologies depending on their specific use case, showing that they can complement batteries in a meaningful way—also from a financial perspective.
Another perspective is that we still have a long way to go before full electrification. Right now, batteries are used in suitable scenarios, but many other areas haven’t been electrified or optimized at all. Other storage technologies might still become relevant. Building a house around a 20,000-liter tank to store energy for heating in Alaska over six months might already be financially and technically viable. But whether the logistical challenges of such solutions will ever make them truly feasible—that’s something I neither want nor can predict.
I strongly dispute this. E-fuels like hydrogen would be much superior to PHES for annual storage.
Yes, hydrogen has low round trip efficiency. But it comes out cheaper than PHES. The "cost of inefficiency" is proportional to the number of charge/discharge cycles. For annual storage, efficiency is 365x less impactful than it is for diurnal storage. What matters for annual storage is capex of storage capacity.
Which is exactly why PHES wins the cost comparison for annual storage. Open air water storage is ridiculously cheap compared to hydrogen storage.
If you want something that may compete with hydrogen for annual storage, consider bulk thermal storage (using artificially injected heat, not naturally occurring heat). The thermal time constant of a very large object increases quadratically with radius, if everything is scaled proportionally, and can easily reach many years. This is why geothermal works at all -- there's plenty of heat stored in the near crust ready to be mined.
You're also comparing hypothetical costs to historical costs. Hypothetical costs put out by industry are usually out by about an order of magnitude.
There's a reason that PHES is the only one with historical costs.
These are not hypothetical costs. Construction of these caverns is state of the practice for natural gas storage. Vast volumes of gas are stored in these things, allowing steady production of natural gas and constrained pipeline capacity to serve seasonally unsteady consumption patterns.
The reason PHES is the only one with historical costs is that, historically, PHES has been used for diurnal storage, from the days when baseload plants were cheaper. There was never a market for long term storage via hydrogen (although some hydrogen storage has been constructed and used to help steady the hydrogen input to ammonia plants); why bother for the grid when just varying the use of fossil fuels would serve that function just as well?
Pumped hydro is primarily used for short term storage. The vast majority of pumped hydro installations around the world operate on an intra-day cycle.
For storage systems generally (not just electricity), profitability is a linear function of capacity, the possible price arbitrage AND how frequently you charge and discharge. Nobody is going to build a pumped hydro storage facility with the intension of operating a single charge/discharge cycle per year.
Nor are pumped hydro facilities cheap to build and certainly cannot be deployed everywhere as they require particular geographic and geologic conditions and mostly locations suitable for pumped hydro are few and far between and those locations that are suitable are generally far away from population centers where the demand for electricity is.
Batteries are often cheaper than pumped hydro, they can be located near demand, they scaled down as well as up and can be distributed around the grid to provide "virtual transmission". They are quick to deploy and require little maintenance or staffing.
The solution for "long term" storage will be massive over-provision of wind and solar and more grid interconnections. Batteries will take care of everything else.
The cables connecting PV to the grid, as well as the grid itself, can all use aluminum conductors. Even large transformers can be designed with aluminum if copper gets too expensive.