Energy's inertial confinement

At the start of the new millennium, fossil fuels account for 80% of the world's energy consumption, but it is clear that humanity's future energy needs cannot be met solely by these energies, which have been stored in the surface layers of our planet during previous geological eras.

Energy storage through the use of fossil fuels is easy. The same cannot be said of electricity, which is destined to play an increasingly important role as a substitute energy source. Electricity cannot be stored directly, but must pass through reversible transformations (gravitational, electrochemical, kinetic potential, etc.).

In the future, the storage function would itself become a "dynamic" source of power, in the sense that it would have to be capable of supplying and accepting the transient power peaks demanded by user loads. The "main" source, on the other hand, would be limited to supplying the average power demanded by these loads.

Such decoupling would make it possible to reduce the sizing power of the main source, which should lead to savings in terms of investment, raw materials and operating costs, as well as gains in the overall efficiency of the various energy systems. Such developments are already taking shape in transport vehicles (hybrid cars – public transport network...) and in electrical or thermal energy distribution networks.

The current challenge facing researchers and engineers is to develop storage solutions adapted to the varied demands of different economic sectors (transport, housing, industry, etc.).

Energy storage can address a number of issues:

• it can compensate for a shortfall due to a discrepancy between supply and demand, or a phase shift between energy production and consumption; this is particularly the case when using renewable photovoltaic or wind energy. The size of the storage element must be adapted to the parameters of the source and the consumer;

• it can compensate for an accidental interruption in the energy supply; this is particularly the case in safety power supply applications where a break in the energy chain cannot be tolerated without irreparable damage, e.g. operating theatres, control rooms for certain industrial processes or strategic decision-making centers;

• it can lead to a reduction in energy consumption in all cyclic-type applications where it is necessary to expend energy to set vehicles in motion, and where part of this energy can be recovered in the vehicle's deceleration phase.

In this dossier, we present an electrical energy storage component, the flywheel, which is a symmetrical device rotating around...