Gravity batteries try to beat chemical ones with winches, weights, mine shafts

Past related threads:<p><i>Gravity Energy Storage: Alternative to batteries for grid storage</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=25650551" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=25650551</a> - Jan 2021 (167 comments)<p><i>Gravity-Based Energy Storage Begins Trials 2021</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24337537" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=24337537</a> - Sept 2020 (2 comments)<p><i>To Store the Wind and Sun, Energy Startups Look to Gravity</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=22394154" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=22394154</a> - Feb 2020 (2 comments)<p><i>Lifting rocks as a form of long term energy storage</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=21736607" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=21736607</a> - Dec 2019 (1 comment)<p><i>Gravity Battery</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=6750276" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=6750276</a> - Nov 2013 (1 comment)<p><i>Gravity Battery Concept</i> - <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=6739349" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=6739349</a> - Nov 2013 (72 comments)<p>Others?

This is an obvious scam if you do the math.<p>Assuming the full scale version delivers peak power for 11 seconds like the prototype, 2MW peak power would be 6 kilowatt hours of energy.<p>That&#x27;s terrible. We&#x27;re taking about dropping hundreds, maybe thousands of tons down a mine shaft to get the same amount of power as $700 of lithium batteries you could carry in a backpack. For instantaneous loads you&#x27;re way better off using flywheels, which we&#x27;ve already had for decades.<p>Gravity is weak, literally. The only realistic use case for gravity generation is hydro power. And MAYBE reverse hydro power where we put giant gas bags underwater and they make energy floating up

Here&#x27;s an idea: what if -- instead of digging a deep hole into the ground -- we use the tower of a wind turbine as the vertical space in which the weight is raised&#x2F;lowered?<p>A wind turbine is already equipped with a generator, so it&#x27;d be a matter of building some sort of &quot;switch&quot; which would make it either: (a) generate electricity using the turbine, as per usual; (b) raise the weight using the turbine, thus not producing electricity; (c) generate electricity by connecting the weight to the rotor&#x2F;generator, while lowering the weight.

As usual everyone is fixated on price when the real hurdle will be scale. If we&#x27;re going to replace our existing fossil fuel plants we need at least as much capacity. A quick grep in the article tells me these guys have a plan for a 4MW plant that involves a 1km shaft. That&#x27;s the same order of magnitude as a <i>single</i> wind turbine, which is already one of the worst ratio of power output per quantity of resource and land use.<p>For reference (<a href="https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Coal-fired_power_station" rel="nofollow">https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Coal-fired_power_station</a>):<p>&gt; As of 2018 coal power under construction was 236 GW, planned 339 GW, and 50 GW was commissioned and 31 GW retired<p>If we want to replace those <i>new</i> plants we&#x27;ll need 100.000 of those shafts. And that&#x27;s not counting the existing plants, and the other fossil-fuel based plants. Think of the quantity of concrete that involves. That&#x27;s just insane. If we want to actively tackle electricity generation we need to use the most efficient low-carbon tech that we already know.<p>Also, we already have gravity-based systems, only nature does all the work of raising the payload for us in gaseous form, and we let it fall in liquid forms. But it takes so much dam place.

&#x27;Switzerland-based Energy Vault wants to use a multiarmed crane with motors-cum-generators to stack and disassemble a 120-meter-tall tower made of hundreds of 35-ton bricks, like a Tower of Babel that rises and falls with the vagaries of energy demand.&#x27;<p>This sounds amazing. It&#x27;s like the repetitive, seemingly-pointless behavior you see in the background in videogames...

This is a clever system. I remember reading about a similar system in Australia that used excess solar power to lift giant concrete bricks, and then these bricks were lowered to the ground in the evenings to drive generators.<p>Not sure if this is the same one I read about, but it&#x27;s the same concept: <a href="https:&#x2F;&#x2F;energyvault.com&#x2F;" rel="nofollow">https:&#x2F;&#x2F;energyvault.com&#x2F;</a>

Stopped reading at a total cost of more than $300 per MWh for batteries.<p>Quick back-of-the-napkin calculation: Car batteries come in at less than $100&#x2F;KWh. They&#x27;re good for at least 1000 cycles at 80% capacity. That gives us at least 0.8MWh for a 100$ investment.<p>It&#x27;s very, very unlikely that initial construction of the site and operational costs more than triple that price.

&quot;But Schmidt’s calculation of the lifetime cost per megawatt-hour for lithium-ion batteries, $367, is more than twice as much&quot;<p>This is ridiculous.<p>I&#x27;m charging right now my EV from a 14 kWh 16S LFP pack which costed me $1400 tax paid and delivered.<p>LFP properly managed will do minimum 3000 cycles, so that&#x27;s 42 MWh for $1400 which gives $34 per MWh out of the battery.<p>Note: 5kW 48V inverter cost $500.

Gravity based battery, stuffed full of lithium ion batteries?

The cheapest gravity storage is capable of holding itself up.<p>Which is why vertical glaciers are so tempting. Its just ice, you pile it up, in large columns, with a puddle of water beneath. Energy is extracted by warming the water and taking part of the pressure to a turbine.<p>Energy is added by pumping and freezing water on top, while the extracted heat is stored in a side tank for later usage. Insulation against heat prevents energy loss for longer times. Four T-beams hold up the freezing machinery on top. Storage grows with demand. If the ice starts to deform, added carbon-flakes, can increase tensile strength. Pressure in the pool is kept via onion-seals<p><a href="https:&#x2F;&#x2F;imgur.com&#x2F;iCg9LzY" rel="nofollow">https:&#x2F;&#x2F;imgur.com&#x2F;iCg9LzY</a>

The technology isn&#x27;t incredibly immature. On the contrary, it&#x27;s understood to the tiniest detail. If it doesn&#x27;t work, it won&#x27;t work.

The system bring talked about here can deliver 250kW during 11 seconds max.<p>That is LESS than 1 kWh of energy storage.<p>I hope it&#x27;s not the one on the picture otherwise their cost estimates are way off and two orders of magnitude larger than current lithium batteries, even taking into account battery replacement.<p>Another problem would be the ever-lowering price of batteries comparing unfavorably against this good old tech with stable or raising costs (human costs tend to rise over time)

Since scale and locality is such an issue here, I wonder if there are any concepts for integrating such a system in new mid-rise buildings. Similar to an elevator shaft, but with a weight of depleted uranium instead of the passenger car.<p>You&#x27;re digging for the foundation anyway, maybe maybe the marginal cost to dig a few meters deeper is worth it. You&#x27;re building with a crane anyway, maybe the marginal cost to build a steel frame tower on the roof is worth it. It&#x27;s certainly not a mine shaft, but perhaps better than nothing.

Not the first time I have heard of gravity batteries, and with the exception of dams, they all look unconvincing.<p>To make a comparison, there is a human-scaled variant of the concept in the GravityLight by Deciwatt. The concept is clever, it involves lifting a bag of rocks to get a bit of light for 20 minutes. But if you run the numbers, it is tiny. As the name of the company suggests, the generator outputs 0.1W, enough to power a 15lm LED. For 20 minutes you need to lift a 12.5kg bag 1.8m. That&#x27;s around 0.03 Wh per lift. By comparison, a good 18650 battery is around 13 Wh, about 400x more.<p>As a niche product, GravityLight is not a bad idea, but it is telling that their new product, NowLight operates the same way, but they replaced the bag of rocks by... a 18650 battery.<p>Back to the topic, it looks like that &quot;drop a weight in a mine shaft&quot; idea does worse than what you can do with a single Tesla car, which have more energy storage and more power at the wheels. Plus, it is cheaper and you get a whole car with it.

I think this guy is onto something...<p>Liquid metal batteries will be better than gravity storage IMHO.<p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NiRrvxjrJ1U" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NiRrvxjrJ1U</a><p>First commercial scale system is going live in 2021 so we shall see how it works out.

We already have pumped hydroelectric storage, it&#x27;s used as a load balancer on some national grids.

Ares is another gravity battery system. They run electric trains up a hill to store energy.<p>But looking at the size of the project, I have a hard time believing this is viable.<p><a href="https:&#x2F;&#x2F;aresnorthamerica.com&#x2F;" rel="nofollow">https:&#x2F;&#x2F;aresnorthamerica.com&#x2F;</a>

The numbers in this article seem off. 250kW (peak power) for 11s (time at peak power) is 2.75 MJ. That&#x27;s only about 51 10000mAh D batteries. Of course, the peak power of the gravity battery is much higher than the chemical batteries, but still.

Higher materials density = higher energy density of the overall system. The more you&#x27;re lifting (e.g. iron, steel, tungsten) the more you can get out in a smaller space. Kind of a cool way to increase the energy density.

So, let&#x27;s look at doing this in a distributed manner: giving every household their own gravity battery. A 1 m3 cube of concrete weighs 2400 kg; moving this over 6 meters yields (mass * gravity acceleration * height) = 140 MJ, = 39 kWh. Lets say 34 kWh after accounting for energy losses.<p>A european household uses approx 3500 kwh&#x2F;year; americans use upwards of 10000 kwh&#x2F;year.<p>Clearly such a slab of concrete will comfortably allow buffering an entire day&#x27;s worth of power, and then some.<p>Edit: fuck me I&#x27;m dumb. Off by a factor 1000. 39 watthour in that cube, not 39 kWh. Ignore everything I said.

What about pumping water up hill into reservoirs?<p>I know not every where is suitable for reservoirs but this seems pretty obvious. Run renewable to pump the water up hills, all the &#x27;battery&#x27; components of the tech are well established. You&#x27;re creating additional benefit by storing potentially potable water. It seems like the tech for water storage&#x2F; transport&#x2F; regeneration to electricity is all pretty well figured out. I&#x27;m thinking some place like the Columbia gorge where there is high capacity for wind and for hydro.

A long time ago I was interested in alternative ways to store energy, one good method but quite expensive is to convert it to Rotational energy of a flywheel, NASA had pretty good results with magnetic bearings and vacuum.<p><a href="https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Flywheel_energy_storage" rel="nofollow">https:&#x2F;&#x2F;en.m.wikipedia.org&#x2F;wiki&#x2F;Flywheel_energy_storage</a><p>It isn&#x27;t practical and much more complicated than the other alternatives mentioned

Gravity and electromagnetic forces are somewhat similar, they both have infinite range, decay as 1&#x2F;r, one key difference is that the electromagnetic force is 10^36 stronger than gravity [0]. Just for that reason I&#x27;m always immediately skeptical of projects of this type.<p>[0] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Fundamental_interaction" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Fundamental_interaction</a>

Does it need to expend the energy to winch it up? Would it not be simpler to have a set of these weights, and a ramp system to deliver them to the top, and use vehicles to unload at the base and drive them back to the top to be hooked up again in sequence? Surely there would be less energy loss moving it up a ramp than fighting gravity in a vertical shaft to winch it directly upwards.

If you pump one cubic meter of air 100 meter deep, the energy stored equals a tonweight at 100 meter up. That is 9.81 kJ aka 2.7 Wh. This is inifinitely scalable and suits flat places like Australia.<p>One and only minor problem is how we prevent the 2.7 GWh energy storage, which is 1E9 m^3 aka one cubic kilometer inflatable container, not rupturing or raising up.<p>But otherwise ingenious nicht wahr?

And these systems are way larger, more dangerous (wind) and not as efficient as magnetic bearing flywheels.<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Flywheel_energy_storage" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Flywheel_energy_storage</a>

This could give a new purpose for abandoned mines all around the world. The shafts already exist and are no longer in use, they would only need some repairs.<p>I grew up in one such city, there were &quot;covered holes&quot; everywhere.

I wonder what is the limit when this kind of storage would only consist of single steel cable. As at certain point weight of cable is so big that it can&#x27;t support even itself anymore.

How efficient the system is? If, say, the machine uses 100KW to lift the weight, what&#x27;s the output?

what if you lift ion batteries instead of iron

Could they make it a space elevator?

I realy like the design of this baterry: Its simple, easy to build and mantain.

Ok, ok, everyone, I&#x27;ve got it. It&#x27;s great. As you know, two <i>meh</i> ideas together make one <i>galaxy-brain</i> idea so here it is. Gravity batteries + vertical farming.<p>This is so amazing I&#x27;m just jittering over here. So what are big shafts filled with before they are shafts? <i>Dirt</i>! What do plants need to grow? <i>Dirt</i>! So what you do is ... wow this is great ... what you do is you take the dirt out, then you make this big battery thing a stack of <i>dirt shelves</i> that go up and down and while they are going up and down they <i>also</i> grow plants in the dirt.<p>So now you have a big field of these dirt stacks going up and down and in the middle you have a big farmers market. Money from dirt <i>two</i> ways. God how is this not already a thing.<p>Problems solved. Done.

It&#x27;s crazy how little we understand about gravity if you think about it. It&#x27;s a perpetual energy source right in front of us, but we never really think about it, and can barely offer a basic explanation as to what powers it. It even impacts <i>time</i> itself[1] for christ sake. I think better understanding gravity is the solution to all human energy needs. (interesting to note I have heard stories of disappeared scientists who made advancements in gravity research years back)<p>[1] <a href="http:&#x2F;&#x2F;thescienceexplorer.com&#x2F;universe&#x2F;how-gravity-changes-time-effect-known-gravitational-time-dilation" rel="nofollow">http:&#x2F;&#x2F;thescienceexplorer.com&#x2F;universe&#x2F;how-gravity-changes-t...</a>