Using Gravity to Store Electricity, Sounds Stone Age But It Works at 90 % Efficiency

trainPicture a chain tied to a large boulder and worked through a pulley system that is attached to a motor that winds the boulder up into the air until it is hanging about 100 feet off the ground.

This sounds dangerous if you were standing right underneath it and trusting the tiny engine to keep that thing wound but you are probably just now starting to get the concept so my mental picture has accomplished its purpose.

Gravity can have some pretty great uses, take for instance a hydro dam. As the water moves through the dam a turbine spins. The great thing about hydro is that the electricity is basically stored by a big wall and we use gravity to give us electricity on demand through the dam wall as the turbines spin on command when water comes through.

Gravity energy storage for the electricity grid is a wild idea but could accomplish a lot considering the whole electric grid is a real-time grid. We store absolutely no electricity but instead generate it as needed.

So what we could do in theory is use a small motor to send a large weight up into the air or up a steep hill and when we need electricity we allow the weight, heavy ball, etc to travel back down and that force pulls on a cable that spins a turbine to offer us electricity when we need it most, during peak demand hours.
A guy by the name of Jim Kelly thinks gravity energy storage is ripe for trying out based on the needs of our modern-day electricity grid. With all these lithium batteries being produced for every appliance under the sun we still can’t use them for energy storage for the grid because they are too darn expensive.

Jim wants to use gravity instead of lithium to store our energy and he just might be on to something. Jim has 38 years of energy storage research and development under his belt from Southern California and Edison.

The concept Mr. Kelly has in mind requires that an electric motor powered by surplus electricity during off-peak hours propels a train up a slope. When electricity is demanded during on-peak hours, low wind periods, cloudy weather, etc. the train will roll back downhill.

The rolling motion of the train will be used to turn the same motor that will act as a generator. There will be a third rail in this train system that is used to both power the train up the hill as well as to receive the electricity generated and send it back on the grid when demanded.

When back up power plants need electricity they can rely upon the gravity energy storage device with an efficiency rate of about 90 % instead of other means.

The nice thing about this method is that it is efficiently storing cheap electricity and then sending it on the grid during high demand expensive time periods.

You would need about 8 miles of train track to provide 500 MW of power for a large-scale storage device. We do not yet know the energy storage capacity so the energy to size ratio is still leaving us in the dark but the idea sounds promising.

The experiment is projected to start soon at a ranch on the Tehachapi mountains. The Tehachapi Mountains, regionally also called The Tehachapis, are a mountain range in the Transverse Ranges system of CA in the Western U.S.

A large-scale system of this type that could provide 500 MW of power (the energy storage capacity was not stated) would require about 8 miles of track.

While 8 miles sounds long, that is of course only the length of the track. The width is not much, so it doesn’t require as much space as it might appear at first. The energy to size ratio cannot be calculated without the energy storage capacity, though.

This project is to be executed on a ranch on the Tehachapi mountains. The Tehachapi Mountains, regionally also called The Tehachapis, are a mountain range in the Transverse Ranges system of California in the Western United States.

Benefits of Gravity Energy Storage

  • They never lose charge
  • Last basically forever
  • High efficiency
  • Simple
  • No rare materials needed

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