SoftBank's Vision Fund investment of $100 million in Energy Vault, a Swiss startup that stores energy in stacked concrete blocks, came as a surprise for a lot of reasons with the most striking of them: the non-existent full-scale prototype.

It's totally unheard of for SoftBank to invest under this circumstance because not only is Energy Vault less than two years old and this is the bank's first bet in energy, the startup hasn't yet built a full-scale prototype.

However, with their ode of global reach, paired with unrivaled ecosystem coupled with freedom-level capital, SoftBank Vision Fund is going to help founders of Energy Vault build a market-leading company.

This area of technology is already ripe for large investments as Akshay Naheta, a managing partner of SoftBank's Vision Fund says the startup is ready for a large sum to deploy its technology around the world.

Energy Vault's technology of storing energy is going to be cheaper compared to companies that are into lithium-ion batteries.

SoftBank's latest investment will use low-cost materials like cement and sand for the blocks, cranes for the moving of the blocks and reversible motors converting electricity into energy and vice versa.

A 400-foot tall, six-armed crane will be in the middle of concrete blocks each weighing 35 metric tons.

Whenever there is an excess in solar or wind power, one of the crane arms will hook a block. A motor will start, powered by the excess electricity on the grid, and lifts the block making it move like a pendulum.

However, the crane's trolley is programmed to counter the movement. With the smooth lifting of the block, the crane puts it on top of another stack of blocks.

The system will be "fully charged" when the crane has a tower of concrete blocks around as energy gets stored in the elevation gain.

Whenever the grid is running low, the motors of the crane return bricks and the kinetic energy is turned into electricity.

Bricks are always placed exactly in the right position.

Storage capacity is 4-8MW of continuous power that can run from 8-16 hours.

Energy Vault's one-tenth scale prototype is in Biasca, Switzerland.

SoftBank's investment in the Swiss startup will help build a full-scale prototype, one for Italy and one for India and then multiple towers with 35MWh capacity for customers.

Naheta said that SoftBank is coming in because the technology is proven and "ready to scale" and SoftBank is confident "with the diligence" they've done.

Ravi Manghani, head of energy storage at Wood Mackenzie, says that because in most places of the world, the costs of solar and wind power are now lower than new-build fossil-fuel power plants, the demand for Energy Vault's technology is growing.

Besides, everyone needs to cheaply store energy for use when the sun isn't shining and the wind isn't blowing.