What is most absurd about Energy Vault is that simply using water (a kind of mini-pumped hydro) would be orders of magnitude cheaper to build and far more efficient.
Gravity storage is not new. It predates the electric motor by centuries. You store power by using it to lift a heavy thing and then let that heavy thing drop and spin a wheel or a turbine when you want that energy back. The weight can be anything; a bag of rocks, a gallon of water, or a custom-form concrete block.
From an engineering perspective, water is the way to go. It's cheap, easy to work with, and turbines/pumps are efficient. Best of all, you don't need to build some bizarre, towering structure to hold it. Just use tanks if there are no natural elevations.
In fact, you could put the whole thing underground if you wanted to. All that matters for gravity storage is the relative distance you move the mass.
Energy Vault seems to be taking us back to the medieval bag-of-rocks method of energy storage.
I've never understood why people consider them innovative.
Water is great mainly because we have so much equipment already invented for handling it automatically. Imagine if you had to invent pumps and pipes before you could demonstrate your idea.
Cables, pulleys, and winches are another mature technology. If you can provide a large constant force on a cable over long distance, reversibly, without need to build anything that long, you might have a winner. You should be able to share the expensive bit, the motor/generator/winch, with lots of cable reels. And, it is better if the winch and reel are off-the-shelf items.
So, put a float with hundreds of tons of buoyancy on a cable through a pulley screwed into the sea floor, thence to a reel and winch on shore. You can share the expensive motor/generator/winch among as many reels as you like. The float might be a sealed balloon full of lithium-saturated liquid ammonia, which is half as dense as the water it displaces.
Air handling is a little less mature. Pump air into a big, light tank well anchored to the sea floor, displacing water. Let the air out through a turbine. People invent elaborate systems to avoid losing heat, but when marginal cost of generation is zero, efficiency doesn't matter so much. The tank only has to be strong enough to hold back the buoyancy of the air. You can add as many tanks as you like. Or, use natural cavities beneath the water table. Maybe pump hydrogen down there, instead. Or hydrogen in one, air in another.
There will be zillions of storage schemes, that all work, until we settle on a few we like best for their secondary benefits. Certainly pumped hydro will remain important.
The main problem for energy storage investment is that investors demand a complex, patentable system, but the best systems are too simple for that. So, there will be a rash of over-complicated storage scheme startups, and not enough simple ones.
So to field a good system, you need to rely on grants, instead. A grant might suffice to prove viability, but it takes investment to build a factory to build systems in the huge volume we will need. So, the parts for your system need to be already manufactured in volume for some other purpose. And you probably need a utility to commit to a huge order and pay in advance.
We need an investment fund that selectively funds scaling up the simple storage systems venture capital can't.
Comments
What is most absurd about Energy Vault is that simply using water (a kind of mini-pumped hydro) would be orders of magnitude cheaper to build and far more efficient.
Gravity storage is not new. It predates the electric motor by centuries. You store power by using it to lift a heavy thing and then let that heavy thing drop and spin a wheel or a turbine when you want that energy back. The weight can be anything; a bag of rocks, a gallon of water, or a custom-form concrete block.
From an engineering perspective, water is the way to go. It's cheap, easy to work with, and turbines/pumps are efficient. Best of all, you don't need to build some bizarre, towering structure to hold it. Just use tanks if there are no natural elevations.
In fact, you could put the whole thing underground if you wanted to. All that matters for gravity storage is the relative distance you move the mass.
Energy Vault seems to be taking us back to the medieval bag-of-rocks method of energy storage.
I've never understood why people consider them innovative.
Water is great mainly because we have so much equipment already invented for handling it automatically. Imagine if you had to invent pumps and pipes before you could demonstrate your idea.
Cables, pulleys, and winches are another mature technology. If you can provide a large constant force on a cable over long distance, reversibly, without need to build anything that long, you might have a winner. You should be able to share the expensive bit, the motor/generator/winch, with lots of cable reels. And, it is better if the winch and reel are off-the-shelf items.
So, put a float with hundreds of tons of buoyancy on a cable through a pulley screwed into the sea floor, thence to a reel and winch on shore. You can share the expensive motor/generator/winch among as many reels as you like. The float might be a sealed balloon full of lithium-saturated liquid ammonia, which is half as dense as the water it displaces.
Air handling is a little less mature. Pump air into a big, light tank well anchored to the sea floor, displacing water. Let the air out through a turbine. People invent elaborate systems to avoid losing heat, but when marginal cost of generation is zero, efficiency doesn't matter so much. The tank only has to be strong enough to hold back the buoyancy of the air. You can add as many tanks as you like. Or, use natural cavities beneath the water table. Maybe pump hydrogen down there, instead. Or hydrogen in one, air in another.
There will be zillions of storage schemes, that all work, until we settle on a few we like best for their secondary benefits. Certainly pumped hydro will remain important.
The main problem for energy storage investment is that investors demand a complex, patentable system, but the best systems are too simple for that. So, there will be a rash of over-complicated storage scheme startups, and not enough simple ones.
So to field a good system, you need to rely on grants, instead. A grant might suffice to prove viability, but it takes investment to build a factory to build systems in the huge volume we will need. So, the parts for your system need to be already manufactured in volume for some other purpose. And you probably need a utility to commit to a huge order and pay in advance.
We need an investment fund that selectively funds scaling up the simple storage systems venture capital can't.