Purely Mechanical Energy Storage

[PP3]

A problem with wind turbines is, of course, that their power is intermittent. I have seen talk of using compressed air or batteries to store the power but both these solutions have problems with efficiency, and batteries leak power even when not used.

 

I was thinking, what about using a heavy weight to store power? Electric motors would lift a weight, then when power was needed, the weight would fall, running the motors backwards and generating power. I guess it would be very efficient, and there would be no leakage of power even if the stored energy was not used for months or even years. It is low-tech and very low maintenance.

 

The heavier the weight, the less far it would need to travel up and down to store and produce the same amount of power. To save materials, I was thinking the wind turbine itself could be the weight: it would only need to move up and down a few cm to store a huge amount of power.

 

I have no background in engineering, so please tell me, is this a good idea, or is there a reason why this has not already been done?

[Acme]

Judging by the weight-powered car projects I often see on forums I'd say that a falling weight isn't as much power as you envision. The idea in-and-of-itself is not new.

Wind Turbine Gravity Storage: Wind turbines lift weights to store energy circa 2006

 

Flywheel storage is often proposed and even designed and tested but the problem there seems to be keeping it from flying apart as well as building protection sufficient to prevent a catastrophe when it does.

Flywheel energy storage

 

There is also pumping water into a reservoir and releasing it later to drive a turbine generator.

Pump Up the Storage

[Enthalpy]

You should put figures on the weight lifting method. What mass, what height to store how much energy. Figures are the stupid reasons that wreak havoc so many fantastic ideas, especially at renewable energy. You could check it (I haven't) for a wind turbine floating on the open Ocean, since depth is available there - don't forget the cable's cost.

 

One affordable means to lift weight is to use water that you don't pay and store it in a huge basin for which Nature has provided all the walls except the tiny dam you add across the vally. Then, the price is correct. Unfortunately, it needs water, mountains, uninhabited valleys.

 

I do like Prof. Garvey's underwater bags to store compressed air

http://www.physforum.com/index.php?showtopic=21016&st=0

alas, no drawings there, sorry for the huge mess. Good reason to prefer ScienceForums.

 

Batteries can work. Their cost is more or less acceptable. Their efficiency isn't that good. The amount of lithium accessible to Mankind is short, but a Japanese university tries to make them with sodium instead: may they succeed.

 

I describe there how I imagine flywheels to be cheap and efficient:

http://www.scienceforums.net/topic/59338-flywheels-store-electricity-cheap-enough/

they're presently my preferred method.

[Endy0816]

http://www.energystoragenews.com/Energy%20Storage%20in%20Elevated%20Weights.htm

 

^Gives a good overview and an analysis of some of the associated costs you would encounter.

 

I'd also heard of another group looking at doing the same with a train engine. Interesting concepts at any rate.

[swansont]

 

I'd also heard of another group looking at doing the same with a train engine. Interesting concepts at any rate.

 

 

What I read about was not an engine, but some train cars on an incline. I reviewed it here:

http://blogs.scienceforums.net/swansont/archives/14819

[Danijel Gorupec]

I never see how power is regulated in such weight-energy-storage propositions... is it by number of weights that are 'falling' simultaneously (many generators) or is there a gearbox before a generator or something else?

[Enthalpy]

I've put an example for a wind turbine at deep sea there

http://www.scienceforums.net/topic/59338-flywheels-store-electricity-cheap-enough/#entry860512

feasible, but flywheels are better.