Instead of batteries: Swiss towers store energy with concrete blocks

Today it is possible to generate very cheap electricity from sun and wind power. And the drop in prices will continue to grow, especially for photovoltaics. The only problem is, where does the electricity come from when the sun isn’t shining or the wind dies down?

Ecologically generated electricity must be stored. One possibility is huge battery systems, there are also exotic attempts, for example by storing energy with compressed or liquid air. The Swiss start-up Energy Vault wants to build huge concrete towers to store the excess electricity. The plans were presented for the first time in 2017 and laughed at by many (“Have the Swiss solved the biggest problem of clean energy?”). Nevertheless, the company raised $ 100 million in a financing round, and now another $ 110 million has been added.

A prototype went into operation in Bellinzona, Switzerland, last year. The technology is reminiscent of a huge children’s toy. Huge cranes pile up concrete blocks of around 35 tons to form a tower. When the green electricity bubbles, the crane lifts the blocks up. But if more electricity is delivered than can be generated naturally, for example because there is currently a lull, then the blocks are lowered again. This then drives generators that generate the additional electricity required.

Cheaper than batteries

A tower can have a storage capacity of up to 80 megawatt hours and should be able to output four to eight megawatts for eight to 16 hours. This technique will not be able to bunker the energy for the winter in the sunny summer. However, it will enable the operators of a wind energy park to actually deliver energy reliably in a pre-calculated corridor. With solar energy one could keep the production of the day for the night. Such a tower is 35 stories high and takes up the area of ​​a soccer field. The cost is eight to ten million dollars. A total of 5000 concrete blocks are moved. The cranes are controlled by algorithms so that the loading and unloading movements run as efficiently as possible. The idea is inspired by hydropower plants in the mountains, where the water is already being pushed upwards with excess electricity in order to feed a hydropower plant if necessary.

This is how the Swiss came up with the idea of ​​the concrete blocks. Your system does not require a special environment and can be used universally. One of the advantages of Energy Vault is the short latency period of the system. The tower can raise its discharge to 100 percent in just 2.9 seconds. The raising and lowering of the blocks and the chain of conversion from electricity to stored energy should result in a loss of only ten percent, according to the Energy Vault.

In addition, the Swiss want to score with a long service life, the system should be able to work for 30 to 40 years. And even after that, the blocks could continue to be used. They are made from an alternative cement made from earth and waste materials. Even with intermediate storage, electricity should still be cheaper than energy from fossil power plants.

The Swiss facility also has the advantage that it does not have to develop any new technologies, but uses existing technology. In 2020 the company was named one of the most important start-ups by the World Economic Forum. This year, after the demonstrator in Switzerland, the first commercial plants are to be built in the USA, Australia and Europe.

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