What are Gravity batteries and how do they work?

What are Gravity batteries and how do they work?

A Gravitricity gravity battery

Gravity batteries store energy through gravity. They are often used to store energy from renewable sources such as solar and wind power. For example, a gravity battery can use solar power to pump water upwards on a sunny day, then, on cloudy days, let the water flow downwards (using gravity) and generate electricity. energy from it in a hydroelectric way.

The biggest problem with renewables is that when the sunlight or the wind goes away, so does the electricity. You need batteries to store excess energy during these times, but not all “batteries” have to be chemical: just use gravity!

The Curse of Abundance

Suppose you haven’t kept up with the development of renewable energy solutions such as solar power. In this case, you may think the main challenge is getting enough solar and wind power, but it’s often the opposite.

When your renewable energy source generates more energy than you need, you must either use it or waste it. That’s why grid-connected solar home systems can feed power back into the grid, and you can even get paid for it!

Off-grid solar home systems use battery arrays to store excess energy so it can be used at night or when it’s cloudy. Special deep-cycle lead-acid batteries have been popular for this use, but lithium-based solutions such as the Tesla Power Wall are becoming a better solution these days.

Whether lead acid or lithium, these batteries store energy using an electrochemical process, but what if you could store and release energy without the need for an electrolyte?

Gravity batteries have potential (energy)

This is where the idea of ​​a gravity battery comes in. Gravity is that force that holds us firmly to the ground. This is why “what goes up must come down”. Overcoming gravity requires an enormous amount of energy. You need a building-sized chemical rocket to launch a relatively small spacecraft with a few astronauts on board into orbit.

When you lift an object off a table, the calories you burn to lift it are converted into potential energy, now stored in that object. If your cat knocks this object off the table later, this potential energy is released when the object falls back to the floor.

A gravity battery converts this potential energy into electricity, but there are many ways to convert potential energy into electrical energy.

Different types of gravity batteries

Gravity diagram showing wind energy stored using weights running down a well

The most common example of a gravity battery today is also widely used. Power companies pump water into elevated reservoirs to store energy. Later, when they want to access this energy, the water is released and flows into another reservoir, passing through a hydroelectric turbine before it gets there. These Water Pump Turbine systems work well, but there are only a limited number of places you can build them, not to mention that they don’t really scale down in any useful way.

There are companies such as Gravitricity that build large gravity batteries that can be installed anywhere, unlike water tank solutions. Their demo rig uses two 25 ton weights in a 15 meter (49.21 ft) platform to deliver 250 kW of power. The company says its technology can scale up to 20 MW and its systems have a 50-year lifespan.

The advantage of these systems is that you can produce a lot of energy in a short time or small amounts over long periods of time. It’s also a great way to make sure there’s power if your renewables have a transient dip, as it takes less than a second to reach full power. More importantly, it is cheaper in the long run than lithium battery installations with similar performance, so it has caught the attention of renewable energy producers!

On a small scale, there are products like the Gravity Light (now defunct) where lifting a weight provides about 20 minutes of light and eliminates the need for dangerous kerosene lighting.

Gravity batteries are likely a key component of a practical and sustainable renewable energy grid thanks to their simplicity and potential longevity.

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