Flywheels: the Low-Cost Solution to the Energy Storage Issue

It is said that covering less than a quarter of the Sahara Desert with solar panels could power the whole planet with electricity. It is said that wind power being considered “one of the most promising new energy sources” could provide 20% of the US’s electricity by putting turbines on less than 1% of its territory. Hydropower, geothermal energy, ocean energy, biomass… all of these renewable technologies embody the possibility for the planet to go green.

However, if some of them seem promising, achieving 100% renewable energy today remains an impossible bet. One of the main difficulties raised is that, although renewable sources are cheap and abundant, we are still dealing with the well-known intermittence issue.

This issue of energy discontinuity could simply be solved rebalancing the energy supply through the storage of the energy surpluses. Yet, storing energy stands at the core of the problem regarding the development of renewables. Indeed, we have batteries, but can we talk about them in a profitable way? I am not so sure. Batteries have a rather limited lifetime and cause global environmental issues especially when it comes to improperly disposed old batteries and their toxic and corrosive materials. Moreover, since few progresses have been made in order to improve batteries’ sustainability, more and more engineers have deepened knowledge regarding a sustainable alternative for storing energies: flywheels. This new technology was thought through the construction of a cylinder spinning at a very high speed, exploiting kinetic energy in order to store energy. To construct the wheels, many materials have been tried, from steel to carbon fiber, but low-cost storage was impossible to reach regarding their expensiveness. One solution was found: using compressed concrete allows a cheaper price and manages to provide the wheels with an unlimited lifetime, thus making them a sustainable alternative to batteries.

Finally, if this technological invention brings new hope, does it not sound too good to be true? I believe that we could easily question the attainability of the perfect conditions for the use of kinetic energy, meaning the perfect absence of air drag in the wheels. Even though the technology to limit these energy losses have been improved, there is still a huge problem regarding the transfer of energy from electric to mechanical to electric again. Though, if the performances of such flywheels remain below the ones of some batteries, such as the lithium ones, for instance, the low cost of this storage technology is very interesting and cost-effective from an economic and ecological standpoint.

Aurélie Calemard du Gardin


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