Talk:Gravity battery

Earliest Gravity Batteries

The claim that the earliest gravity batteries were pendulum clocks would not seem to hold up - there were clocks driven by descending weights well before that, such as the Salisbury Cathedral clock in the UK (https://en.wikipedia.org/wiki/Salisbury_Cathedral_clock) which dates to 1386. — Preceding unsigned comment added by 144.173.163.65 (talk) 15:10, 16 January 2023 (UTC)

Discussion on how little energy this can practically store (uncited)

Using some basic assumptions, let's assume we push up a large mass using a hydraulic cylinder. This is one practical example of a gravitational battery, but other alternatives are possible, such as hoisting it up using a cable, or hauling it up an inclined railway, but using a hydraulically raised mass seems to be the most practical. The actual practical implementation doesn't matter as much as the mass being lifted, the change in height, and the gravitational field (9.8(m/s²) at sea level, let's just use 10 (m/s²) to simplify). If we assume a change in height of 10 meters (roughly 30 feet) using a 10 meter long hydraulic cylinder, and we assume a 10 metric tonne mass (10,000 kg, roughly 20,000-25,000 pounds), then the energy being stored is equal to the change in gravitational potential energy, which is (mass) * (∆height) * (g) = (10,000 kg) * (10 m) * (10 (m/s²)) = 1,000,000 (kg(m²/s²)) = 1 MJ, which may seem like a lot, but is only 0.28 kilowatt hours = 280 watt hours (only enough to light a single 60 W lightbulb for 4.67 hours, and storing hardly any energy in the context of the energy use of a town or city); if we were to double either the mass, or the change in height, or increase either by a factor of ten, then the amount of energy stored is only twice, or tenfold more, which may seem promising, but that becomes physical and economically impractical for constructing a hydraulic accumulator. One of the few implementations of gravitational potential energy storage which is practical is pumped hydro, which uses enormous masses of water over large changes in height, which means it is only economical to construct in only a few places (capable of supporting large reservoirs of water near steep hills with available water). I think this article should have links to the article on pumped hydro and to hydraulic accumulators (which are basically the implementation discussed above, and which is used for storing small amounts of hydraulic energy and for smoothing out pressure variation in hydraulic machinery), but otherwise, I think this article should be nominated for deletion, or should more clearly demonstrate the impracticality of storing large amounts of energy in gravitational potential energy except in the case of pumped hydro. Bfoshizzle1 (talk) 20:47, 9 January 2019 (UTC)

You just have lots of hydraulic accumulators, much as you don't have one giant wind turbine, but lots of smaller ones. An accumulator "farm" can store useful amounts of energy without each individual accumulator being too large to construct. This is how the inclined gravity railway projects are planning to work at scale - you have many parallel tracks, not one very long/high capacity one. Either way, your calculations above are original research on the topic, which isn't useable in a Wikipedia article. So if you want to add a "disadvantages" or "challenges" section to the article, you'll need to find and cite a few reliable sources. That seems useful (if such sources exist). I don't see the argument for deleting the article, though. Railfan23 (talk) 21:49, 9 January 2019 (UTC)

Do You really expect that somebody does a big scientific work about this nonsense? You can store 1 kWh electricity in 6,5 kg LiFePo4 batteries. With 90 m height difference 4000 kg are necessary. I came across this article, because was used as argument in social medias how great this is.Pege.founder (talk) 13:26, 12 October 2021 (UTC)

Cutting CO2 emissions

From the article:

Implementing gravity batteries on a larger scale would therefore decrease the need for fossil fuels, significantly cutting down CO2 emissions.

This is a neat statement but I have no idea if it is true. Can anyone find a reliable source that has reported a study showing that gravity battery solution are expected to actually cut CO2 emission? The best I can find are statements like this: it is being welcomed as a promising and effective addition to the string of alternative energy sources required to lower CO2 emissions. That doesn't seem good enough to support what is currently being claimed.Jared.h.wood → JHelzer💬 20:15, 9 February 2021 (UTC) For day night balancing are about 1000 GWh batteries for Germany required. At the current LiFePo4 batteries are this about 6.5 million tons batteries. With 90 m height difference, 1 kWh requires 4 tons (100% efficiency to make the discussion easier). All together 4 billion tons. 1 kWH of LiFePo4 batteries is about US$ 100. With 90 m height difference and 4000 kg, each kg of the construction should be US$ 100 / 4000 = US$ 0.025. Just my 2 and a half cent about this.Pege.founder (talk) 13:36, 12 October 2021 (UTC)

Wrong numbers all over the article

Its sad, that IEEE published the number of 35 MWh stored in those concrete blocks. Just as a reminder: when lifting 100 tons by 100 meter the amount of stored energy is 100 Mega Joule or somewhat less that 30 kWh. (or 1/3 of a tesla battery);1 KWh is 3.6 Mega Joule. For 30 MWh one would need 100000 tons lifted by 100 meter 70.70.140.75 (talk) 05:22, 28 May 2022 (UTC)

"Bricks in an inner ring, for example, might be stacked up to store 35 megawatt-hours of energy." (IEEE 2021-01-05) They're clearly referring to the total storage capacity of a segment of a potential facility, and not that of one individual block. Obviously the WP article doesn't convey this accurately. SamuelRiv (talk) 19:10, 6 August 2022 (UTC)

"Pumped storage hydropower costs $165/kWh to operate" is nonsense, too. This article needs to show the facts, the uselessness of small scale "Gravity battery" compared to LiIon batteries. I have added simple calculation examples, from pendulum clock to person climbing stairs and King Kong in NYC, neither can match a simple battery. A bus load of scrap in a mine shaft is nearly as expensive as a matching battery. Only very large pumped storage can compete, and only in the few countries that can build such plants without having to face protest. 193.159.98.109 (talk) 21:50, 23 June 2024 (UTC)

Dubious

Why the heck would you have to make the weight entirely out of solid iron? We have, like, dirt, and rocks, which tend to cost approximately $0. jp×g🗯️ 13:50, 24 July 2024 (UTC)

Yes, the whole article is dubious, and this here is not an engineering or business case discussion forum. Anyway, I guess you refer to the simple example of a "weight the size of a bus[3] made of scrap iron, at 700 tons, lowered into a 1000 m deep mine shaft, would provide 1900 kWh, but at over US$ 100[4] per ton of scrap iron, would cost US$ 70000"? So you replace the US$ 100 per ton scrap iron by $0 rocks, make the weight about three time as big due to lower Density#Various_materials, and then you add all the cable pull rigging, winding drums and machinery needed to lift and lower 700 tons in a 1000 m deep mine shaft. Because that insignificant detail has been neglected up to now. What size of an elevator will US$ 70000 buy you? Roughly one private home elevator, that maybe travels from the cellar to the attic, four floors, 10 meter? Carries about 250 kg of rocks or humans? This will equal the other example "A 100 kg human would have to climb stairs of ten floors (25 m) to match the little battery cell" of a mere 7 Wh. "The main problem with gravitational storage is that it is incredibly weak compared to" proper storage, as dothemath.ucsd.edu says.