> Developers and power plant owners plan to significantly increase utility-scale battery storage capacity in the United States over the next three years, reaching 30.0 gigawatts (GW) by the end of 2025
Can someone explain how/why they are measuring storage capacity in watts?
They’re talking about the power capacity, which is the maximum instantaneous rate of discharge as measured in kW, as opposed to the energy capacity which is measured in kWh. From what I can glean, it appears that for many applications, the power capacity is actually the more important number.
It is a bit weird, and seems to come from a history of fossil fuel, nuclear, and/or hydropower where the total capacity is always some (very large) multiple of the instantaneous power level.
With storage currently just supplementing other power sources as renewables aren’t the majority (or all) of available capacity to provide grid stability, it makes sense I guess. None of these battery storage systems need to provide meaningful load beyond a few hours now.
Hard to imagine that won’t change at some point though, probably soonish?
"Long duration" storage doesn't have many economic use cases right now, unless the cost is a tiny tiny fraction of current storage costs. There are many startups developing tech for this, and one with the most hype (and the one I'm most excited about) is Form Energy, which is using iron-air chemistry.
Nonetheless, I do not expect to see a significant market demand for such batteries until into the 2030s; it takes a really high level of renewables penetration before it makes sense to start having long duration storage at the moment.
If there is a large need for it, I would expect that a lot of existing installations will be upgraded with longer duration, so that the same inverters and grid connection can be reused. New connections to the grid are becoming quite difficult to build on a reasonable time scale, and there's starting to be significant economic rent from just the permitting and connection stages.
Do you think it will require the phase out of things like Natural Gas peaker plants to make longer term storage more worthwhile?
Off grid, the most economic setup right now in California is essentially solar + batteries with battery storage sized up to about a day/24 hrs of load, with a propane fueled generator + propane backup heaters for ‘emergencies’ like long winter storms.
Generators get exercised regularly to ensure functionality, but otherwise don’t get run unless needed, which is rare. Maybe 16-24 hrs a season. They also charge the batteries when their full load isn’t needed elsewhere, which cuts run time.
Natural Gas would of course be the replacement for propane in a grid situation, where it was available.
The paperwork and permitting in general is a sign of the future for sure. sigh
Last I heard, lithium ion is cheaper than the OpEx for the average existing natural gas peaker, but I haven't checked in a year or two. With the fluctuating cost of gas, and the recent small rise in battery cost from supply constraints, I could see that flipping back and forth. And there will be a long delay between having a new cost king and a switchover due to utilities being able to charge rate payers for stranded capital, and also the generally slow utility process for developing new resources, which is often on a five year time scale, using decisions made on five year old data.
That's pretty exciting with regards to off-grid use, I don't know much about it. 24 hours of fossil gas use per season is just absolutely tiny, one could definitely even imagine synthetic fuel production from electricity and air being enough to generate that. Thanks for the info!
Or perhaps your understanding of the problem is incomplete?
The point of the batteries are to store power when it's cheap and abundant, then deliver it during peak demand for sustained periods. The time between those periods is measured in tens of hours.
Of course we care about the energy amount stored - some. But total power capacity is more important for a large number of applications.
The usage the OP listed (arbitrage) is only one of the 9 function listed by the National Renewable Energy Lab[1]. Many of the functions need immediate power capacity in the seconds to an hour (so MW seconds or MW minutes), and more important is the speed of response and the amount of power deliverable.
That is, they are talking about power capacity (power is probably implied by default), which is provided by a type of device. The type of device is “battery storage.”
I came here to complain about the same thing. Don't they have anybody who can proofread these diagrams and texts? For some reason, electric power related articles are super prone to people getting units wrong.
And for a lot the initial lithium ion storage on the grid, which was used for frequency regulation, the W/h or ability to respond to powe change, was a far far more important characteristic of the batteries than the Wh.
The EIA understands energy and power, the unit names used for energy and power, and is using them correctly in this short article. As much as I hate it when they use terms like "billion kWh" in some of their reports, it is their prerogative and a correct use of terms.
Why do people think that battery storage doesn't have a power specification? To the point that they will incorrectly declare others to now know what they are talking about, when in fact the accuser doesn't know?
Are you saying that you can't measure battery power capacity? Why would you assert something weird like that?
Grid assets are measured by power, and power is a key specification of storage capacity.
Edit in response to your edit: the EIA, and in fact all the people who run grids and the grid storage, refer to capacity in terms of power, and when talking about "storage capacity" on the grid continues to use power because it would be nonsensical and silly to switch to a not-so-useful energy unit rather than power unit when power is the key metric for grids.
That seems of limited use without knowing for how long the power can be supplied. 1GW for 1 second is pretty useless. 1GW for a minute not much better.
Most people would say that 1GW lasting a day is more storage capacity than 10GW lasting only an hour.
Wouldn't batteries optimized for power take the form of supercapacitors [1] instead?
"Seconds" of capacity might be useful for "primary frequency response" but not for any of the other functions listed in table 1 of https://www.nrel.gov/docs/fy19osti/74426.pdf. Primary frequency response is only seen as important in a limited number of markets in the US (see that table).
It turns out that the resources that get deployed in the grid are useful ones rather than something that deploys 1GW for 1 second. So referring to the power capacity, and dispatching based on power capacity, is how to make decisions when operators bus into the grid. At any moment, a power source may trip off, or decide that the price they are being paid is not high enough to justify continued operation.
The grid is an amazing, absolutely massive, machine for matching power at the generation and load sides. Power, of both the real sort and the reactive sort, are the name of the game.
As far as optimization for power over minimal capacity, the best use case for supercapacitors might be frequency regulation, but batteries have proven to be superior for that particular use case, with a few fly wheels also taking part.
I think it is mostly use correctly. They genuinely are talking about "the total possible instantaneous discharge capability" when they talk about "storage capacity increasing".
I think this is because in table 1 of the linked doc they list where batteries help the energy market and most are capacity (as in power delivery capacity) limited, not stored energy limited (ie most of the uses are measured in "hours" of stored energy or less. In general it reads as the limiting factor is power capacity, not energy storage capacity).
If you think of this as "the capacity of power we can generate at any given moment due to these batteries" then it makes sense. Just the same way as you would say "hydro power capacity"
Suparna Ray, the independent statistics and analysis EIA person writing about Utility scale photovoltaic and thermal here appears to be using EIA forms like this as the basis for her article. (She's listed as a contact on this form but it is hard to find info on who she is).
Be advised, if one travels to witness this place, (Bath County Pumped Storage Facility) one will likely need to be ready to trespass to get a good look unless you have a prearranged tour. The owners have a lot of money for signs and fencing. But, it's worth it, the grandeur is jaw dropping.
There's also little to no cell service due to NRQZ. There's a nice campground at the base of the lower dam.
There's actually a lot of pumped energy storage up and down the east coast of the US to take advantage of things like nuclear power arbitrage. (Always-on nuclear power is cheap at night, while on-demand hydro power has a premium during the day) Many manmade power storage lakes doubled as real estate development schemes which made them a slam dunk economically for the power company. For example, my relative has a house on Lake Keowee in South Carolina which has a nuclear power station nestled amongst multimillion dollar lakehouses, and is interlinked to both upper and lower reservoirs for energy storage and heat dissipation.
One interesting point is I doubt such projects could be replicated at all today in USA. Batteries are the way forward.
Context for your context: Bath County resevoir is descrbed as "largest battery in the world", and cost the equivilent of 4 billion dollars (in 2021 $), occupies 265 acres of land, and has a capacity of around 14,000,000 m3 of water.
I'm curious to see how the costs compare. My understanding is pumped hydro storage gets cheaper at scale. If my math is correct, 24GWH of storage at $4 billion dollars^ is $167 per kilowatt hour. What do these batteries cost to install at scale at the moment? What are they predicted to cost in the next 5, or 10 years?
^ does the 4 billion include the cost of land? Probably not important, even at an "expensive" 200k an acre, that's only 50ish million extra in costs.
Even putting costs aside it seems like it could be unlikely that such a thing could be built at all today. Flooding huge swaths of ecosystems is no longer in vogue and dam removal is picking up in pace. When was the last major scale hydroelectric dam built in USA?
It's worth noting that pumped hydro, and the dams that are getting torn down for environmental these days, often look very different.
Usually the dams that are getting torn down, block the entire river, and thus fish from passing up or downstream of the dam. (Fish ladders exist but are not particularly effective.)
Interestingly, it’s also becoming somewhat common to dam off (concrete-fence-off?) the entire top of a hill somewhere for pumped hydro. Essentially the opposite of what you’d do for a hydropower installation.
Also, pumped storage tends to be smaller, in that it’s meant to provide a certain level of discharge for hours or days. So the reservoirs can be a lot smaller.
My feeling is a big advantage for batteries over pumped hydro is utilities can can locate them on existing land they own and have use permits for. So quietly spend money today and reap the benefit immediately without having to fight Nimby's and the Sierra Club.
Pumped hydro can amortize over 50-100 years. In a true renewable grid, you will get over 50,000 cycles from the same dam (with some turbine replacements).
Thermal degradation will likely take it out before 100 years, but odds of wearing out next gen sodium ion batteries by cycling are pretty slim https://natron.energy/product/
Costs for LFP are around $350/kWh and about half consists of BOS like inverters, charge control cooling, fire control, etc.
10-20% YoY drop in manufacturing cowts is pretty likely, although demand will keep up with production and lithium extraction capacity so this might just turn into profit in the short term.
Sodium ion is presently scaling, which should remove most of this raw material limitation by late 2020s. Additionally the lower volumetric capacity, higher coulpmbic efficiency and higher thermal stability should reduce cooling and fire control.
TL;DR Some/most people expect it to drop each year similar to what solar did. I expect prices to be stable for 2-4 years while anyone with a lithium mine or existing production builds a small ocean of cash to swim in and then crash abruptly to <$80/kWh
It is a little confusing because they use the term “battery storage capacity” a bunch of times. This looks like the… amount of storage capacity that the batteries have. But I think they actually mean it as, like, (battery storage) capacity. Like battery storage is just the name of the type of thing that provides [power] capacity.
Grid resources' most salient aspect is their power rating. For lithium ion batteries, there is typically four hours of duration when discharging at maximum capacity, though sometimes it's as low as one to two hours. And for the earliest lithium ion battery that were used for frequency regulation, it was as low as 15-30 minutes of duration. But today, it's usually safe to multiply the GW by four to get GWh for grid batteries, if one cares about the GWh more than GW for some reason.
Can someone explain how/why they are measuring storage capacity in watts?