Gravity batteries store energy using gravity. They are often used to store energy from renewable sources such as solar and wind. For example, a gravity battery could use solar power to pump water uphill on a sunny day and then, on a cloudy day, let the water flow downhill (using gravity) and generate power from it hydroelectrically. .
The biggest problem with renewable energy is that when the sunlight or the wind disappears, the energy also disappears. You need batteries to store excess energy for those times, but not all “batteries” have to be chemical – just use gravity!
The curse of abundance
Suppose you haven’t kept up with the advancement of renewable energy solutions, like solar power. In that case, you may think that the main challenge is getting enough energy from solar and wind power, but often the opposite is true.
When your renewable energy source generates more energy than you need, you have to use it or lose it. This is why grid-tied solar home installations can feed energy back into the grid, and you can even get paid for it!
Off-grid home solar installations use battery arrays to store excess power 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 like the Tesla Power Wall are becoming a better solution these days.
Whether lead acid or lithium, these batteries store energy through 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 keeps us firmly on the ground. That’s why “what goes up must come down”. Overcoming gravity requires an enormous amount of energy. It takes a chemical rocket the size of a building to launch a relatively small spacecraft with a few astronauts on board into orbit.
When you pick up an object on a table, the calories you burn to lift it are converted to potential energy, now stored in that object. If your cat knocks that object off the table later, that potential energy is released when the object falls back to the ground.
A gravity battery converts that potential energy into electricity, but there are many different ways to convert potential energy into electrical energy.
Different types of gravity batteries
The most common example of a gravity battery today is also one in widespread use. Power companies pump water into elevated reservoirs to store energy. Later, when they want to access that energy, the water is released and flows into another reservoir, flowing through a hydroelectric turbine before getting there. These water pump turbine systems work well, but there are only a limited number of places you can build them, not to mention they don’t really scale down in any useful way.
There are companies like Gravitricity that are building large gravity batteries that can be installed anywhere, unlike water tank solutions. Its demo platform uses two 25-ton weights on a 15-meter (49.21-foot) platform to deliver 250 kW of power. The company claims that its technology can scale up to 20MW and that its systems have a design life of 50 years.
The advantage of these systems is that they can produce a lot of energy in a short time or small amounts for long periods. It’s also great as a way to ensure there’s power if your renewables take a temporary 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 that provide similar performance, so it caught the attention of renewable energy producers!
On a small scale, there are products like the (now defunct) Gravity Light, in which lifting a weight provides about 20 minutes of light and eliminates the need for dangerous kerosene lighting.
Gravity batteries are likely to be a key component of a practical and sustainable renewable energy grid thanks to their simplicity and potential longevity.