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.
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?
(Battery storage) capacity
not
Battery (storage capacity).
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.”
A quick look at their site shows "battery power capacity" is measured in watts, whereas "battery energy capacity" is measured in watt-hours.
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?
The very first chart in the article is titled "U.S. Battery Storage Capacity (2015-2025)", but the vertical axis is labelled "gigawatts".
Storage capacity is not measured in gigawatts.
Edit: yes, batteries also have a power delivery rating, but that is not what is implied by "storage capacity".
https://www.seia.org/sites/default/files/EIA-860.pdf
It would be good to see the actual data.
This is an area I'm interested in. HECO in Hawaii are arguably the most advanced in battery storage. https://www.hawaiianelectric.com/documents/clean_energy_hawa...
To put this in context Bath County is a reservoir that has 24GWh of storage.
https://en.m.wikipedia.org/wiki/Bath_County_Pumped_Storage_S...
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.
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.
Edit: looks like the information is here somewhere in the national dam inventory: https://nid.usace.army.mil/#/dams/search/&viewType=map&resul...
But I am very tired and must sleep so I will not query.
https://www.nrel.gov/docs/fy21osti/79236.pdf
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.
And batteries are perfect for grid stabilization.
EDIT: numbers..
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's really silly to assume that the literal Energy Information Administration doesn't know the difference between the units of watts and watt-hours.
Battery power capacity is watts.
Battery energy capacity is watt-hours.
This article is talking about power capacity.
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.
I think that there are pros and cons of each, we'll end up with a mix of lots of different solutions.
"Scotty, increase engine power by 1 gigawatt per hour!"
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
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!
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.
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.
[1] https://www.nrel.gov/docs/fy19osti/74426.pdf see table 1
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?
[1] https://en.wikipedia.org/wiki/Supercapacitor#Comparison_with...
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).
I do think the graph in the linked article (https://www.eia.gov/todayinenergy/detail.php?id=54939) should use terminology consistent with https://www.nrel.gov/docs/fy19osti/74426.pdf though.
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.)
Pumped hydro may sit by the side of a river, but otherwise not obstruct the flow, and so that is not a major issue. (Example rendering: https://cdn.forumcomm.com/dims4/default/3ac369d/2147483647/s...)
It also makes a lot more sites interesting.
[https://www.sciencedirect.com/science/article/pii/S254243512...]
