Energy Vault of Switzerland has developed a "cement energy tower," which can store massive excess green power, functioning as a giant battery supplying low-cost energy.
The tower consists of multiple heavy concrete bricks, just like a structure comprised by building blocks, with a full height equivalent to a 35-story building. It envelops a vertical hoist, with six giants arms at top, which can move the concrete bricks to the lower level, thereby triggering the operation of generators via the principle of potential energy, similar to the operation of a pumped-storage hydroelectric power plant.
Robert Piconi, chief executive of Energy Vault, explained that after receiving signal from grid, the built-in software of the tower would lift or lower concrete bricks according to weather conditions, including wind speed, thereby generating power steadily.
The series of photos demonstrates the power-consumption process of the energy storage tower, the one on the far left indicating full storage capacity and that on the far right near depletion of stored power.
Each tower boasts 10-35 MWh of power storage capacity, with peak power output reaching 5 MW. It features a modular design and a number of multiple towers can be built together to augment storage capacity. For its bulky size, the tower can function nimbly, as the hoist can be triggered within 2.9 seconds, with round-trip performance hitting 90%. It doesn't have the problems of electrolyte leakage or performance degradation, plaguing regular batteries.
Energy Vault claimed that life of the energy tower, made of concrete scraps, can last 30-40 years.
Energy Vault hoped that such cement tower could become a common supplement to renewable energy plants, storing excess power for use during windless or cloudy days and thereby enabling grids to maintain stable power supply. The company noted that with US$7-8 million of estimated construction cost each, its power cost per kWh is lower than lithium-ion battery, flow cell, and other energy storage systems.
The company has built a prototype tower, 20 meters high, with a hoist capable of lifting concrete bricks weighing 500 kilos. It is scheduled to build a 35 MWh tower for Tata Power of India in 2019. Along with the effort to look for customers, it will endeavor to improve the operating efficiency of hoist and lower the cost of concrete bricks by using mixed building wastes.
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(First photo courtesy of Energy Vault, written by Daisy Chuang)