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

Post by [deleted] » Sat, Apr 24, 2021, 12:33 PM UTC

prof-dr-ir wrote: post #87

rakoo wrote: post #48

As usual everyone is fixated on price when the real hurdle will be scale. If we'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's the same order of magnitude as a single wind turbine, which is already one of the worst ratio of power output per quantity of resource and land…

> But it takes so much dam place. Does it? If you use iron instead then we only need to know that it has eight times the density of water. Multiplying a volume by eight is not a lot; it's only twice the size in length, width, and depth. So let's imagine replacing a typical hydroelectric power station [0] with a 'gravicity' system. Supposing the same depth you need a system of about one third of its length and its wid…

Post by masklinn » Sat, Apr 24, 2021, 12:37 PM UTC

thehappypm wrote: post #108

runeks wrote: post #76

Here'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/lowered? A wind turbine is already equipped with a generator, so it'd be a matter of building some sort of "switch" which would make it either: (a) generate electricity using the turbine, as per usual; (b) raise the weight using the turbine, thus not produ…

I’ve always been surprised that there is no product wind turbine with a guaranteed power output, that is, a turbine with an embedded battery. Sure it would cost much more, but in some applications steady power is worth it.

Post by masklinn » Sat, Apr 24, 2021, 12:46 PM UTC

tchvil wrote: post #46

xyzzyz wrote: post #6

Earlier quoted context omitted.

Yeah, if you do the math, it turns out that you need impractically large weights lifted to unreasonable height. Like, suppose you’re lifting 100 ton weight 100 meters high. That’s a rather large and heavyweight system. How much energy you can store this way? Less than $5 worth of electricity, as it turn out. This is basically the same as pumped water storage, but instead of immense amount of water you can pump betwee…

How about to retrofit wind turbines? They are tall, strong, and empty inside.

Post by martinald » Sat, Apr 24, 2021, 1:00 PM UTC

audunw wrote: post #90

rakoo wrote: post #48

As usual everyone is fixated on price when the real hurdle will be scale. If we'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's the same order of magnitude as a single wind turbine, which is already one of the worst ratio of power output per quantity of resource and land…

It's a common misconception that energy storage needs to handle all the power needs of an area for a significant time. The most immediate need for energy storage is frequency regulation, and short hours-long dips in power output. If we can solve that we can scale renewables very far. For days-long dips in power output, it's probably better to keep some gas power plants on stand-by. I think many areas of the world has…

Post by isoprophlex » Sat, Apr 24, 2021, 1:08 PM UTC

prof-dr-ir wrote: post #126

isoprophlex wrote: post #122

So, let'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. A european household uses approx 3500 kwh/year; americans use upwards of 10000 kwh/year. Clearly such a slab of concrete will comfor…

140 kJ, not MJ [0]. So you'd need a thousand of these cubes for 39kWh. But you can also just raise your single cube by 6km. [0] https://www.google.com/search?q=2400+kg+*+10+m+%2F+s%5E2+*+6...