Will return to reinvent the storage of energy by high -efficiency roller of inertia
Energy storage per steering wheel of inertia is not a recent idea.It is even the oldest known method, still exploited today.But faced with STEPs, the boom in batteries and recently hydrogen, this solution is rarely used.If it has the advantage of a high performance and a long service life, the limited storage time does not plead in its favor.But the Texan company Vetter will announce the development of a new, more efficient technique whose cost would be twice as advantageous as that of Lithium-ion batteries.
An inertia steering wheel stores electricity in the form of kinetic energy.It consists of a mass, most of the time a cylinder, rotating around an axis and locked up in a protective enclosure.
In the storage phase, an engine connected to the axis converts electricity into kinetic energy, which increases the rotation speed of the mass.In the stationary phase, that is to say energy conservation, the speed of rotation of the mass must be maintained constant.The energy supply is then minimal and only compensates for the losses related to friction.And restitution phase, the engine plays the role of generator and converts mechanical energy into electricity, slowing down the mass.
The principle is very old.Since antiquity, potter towers have had a wooden tray which makes it possible to regulate and facilitate the movement given by the foot of the craftsman.In the 19th century, most of the steam machines had inertia wheels.In the 1920s, some Belgian and Swiss trams were equipped under their floor with heavy cast iron discs of more than a ton that allowed them to go from one station to another without current.The disc was restored by connection to the electrical network at each station.
Intervene in a fraction of a second
If the STEPs and the batteries keep almost all the energy during the stationary phase, this is not the case with the ruffles of inertia that remain in motion.So there are friction, synonymous with losses and self -discharge.Consequently, the ruffles of inertia were so far reserved for uses requiring only limited storage periods, in the order of a few tens of minutes.Inertia storage is therefore mainly used for frequency regulation and voltage support on electrical networks, to prevent voltage falls.The city of New York for example, has a modest power plant (20 MW), but which, thanks to 200 ruffles of inertia, can restore in seconds enough energy to help maintain a dietregular in electricity.
Technology is also used on niche markets, for example to supply an operating room from a hospital or data center.In the event of a network cut, inertial storage can take place in a fraction of a second while waiting for the start -up of other more powerful electrical production, such as a generator.
New developments
However, the storage of electricity having become a strategic issue of the energy transition, the ruffles of inertia are today the subject of new developments in order to ensure the smoothing of the production of renewable energies.
Different solutions were developed to minimize energy losses during the stationary phase: the use of high performance ball bearings, the confinement of the rotor in a vacuum enclosure, the magnetic suspension of the axis, etc.For the rotary mass, new materials are also implemented.Previously made of cast iron or steel, they are now made up of glass or carbon fibers, kevlar, etc.Winner of the EDF-Pulse competition in 2015, La Française Energestro works on a fiber concrete prototype.
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More recently, the Texan Startup will return will claim on its site the design of inertia "comparable to lithium ion batteries in terms of delivered power, but half cheaper and 20 times more efficient than current solutions".Ben Jawdat, founder and CEO of the company thinks they have found the way that allows inertia ruffles to store long -term electricity and compensate for the variability of renewable energies. He claims to have developed a 100 kWh model with a rotor7 tonnes that stores electricity for 4 to 5 hours with a yield of 90 %.It’s better than 85 % of batteries and 75 to 80 % of STEPs.
Lire aussi :Stockage de l’énergie : une technologie prometteuse mise au point par une startup suisseAccording to Jawdat, the performance of its technology is made possible thanks to innovations in three key areas: the materials used for the rotary mass, the generators and the suspension of the rotor.The improvements made to metallic alloys and composite materials have notably improved the resistance of rotors, allowing them to turn at higher speeds.
Superconductors
But the most important technological development lies in the development of an innovative suspension without friction, explains Jawdat.Classic inertia steering wheel use either mechanical bearings, such as high performance ball bearings, or magnetic suspensions without friction, the magnetic field being created by electro-like.However, these two options go hand in hand with significant energy losses.
Verter will use "passive magnetic bearings" which maintain the rotor in balance without external control and therefore without energy expenditure.The secret lies in the use of superconductors [1] "at high temperature" to create the magnetic field. "The improvements made to the manufacture of superconductors made them more affordable for commercial applications" tells us Ben Jawdat.The return inertia wheels require only a small amount of superconductive material, maintained at a temperature of approximately -196 ° C (77 k), by a standard cryogenic refrigerant.Most of the machine works at room temperature.
Yield of 90%
This tip "reduces energy losses thanks to the inherent capacity of the system to trap the magnetic field that keeps the rotor in place".According to Verterra, its 100 kWh prototypede loses only 50 watts during the stationary phase.In comparison, conventional inertia wheels consume more than 1000 watts, claims Jawdat."For a full load and discharge and a storage of 4 to 5 hours, the yield is 90 %," he adds.
Verter will see a future for its machines in the balancing of electrical networks and the smoothing of production of wind and solar parks.With an important advantage compared to Li-ion batteries: "With our technology, you can load and unload all day for 30 years, and your storage capacity will always be 100%, while batteries must be replaced after 10 years».
[1] A superconductor is characterized by the absence of resistance to the passage of the electric current, and the expulsion of the magnetic field (Meissner effect).This phenomenon is manifested at very low temperatures, close to absolute zero (−273.15 ° C).
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