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Résofil no.13
Winter Outlook 2017-2018
Val de Saône-A program to ensure competitiveness and security  of supply in France

Gas expansion: a new source of clean energy?

In light of the energy transition process, GRTgaz applies innovative solutions to make use of all available energy sources.

We are currently studying the generation of power from pressure energy lost during the expansion of natural gas at several points on our network, which heralds a promising future for the generation of carbon-free electricity. An explanation.

A recoverable and usable source of energy

To transport large quantities of natural gas over great distances, it is compressed and kept under high pressure. The aim is to reduce its volume and, thereby, the diameter of the pipelines. Subsequently, a certain amount of energy is released and lost at every point of the network where pressure has to be reduced (known as expansion) to adapt to downstream conditions.

The energy thereby released is also recoverable, clean (as it is carbon-free) and usable in substantial proportions. In fact, an accessible deposit study carried out in 2015 identified around 20 sites that could house a generator powered by the flow of gas instead of the conventional expansion system. This operation would produce almost 100 GWh of electricity per year, which represents 25% of the energy consumed by the network's electric compressors.

Technological solutions and contractual difficulties

Several technological solutions are mature and already in use on a number of sites. Some large industrial groups already make use of these solutions: General Electric, Siemens, Atlas Copco and Cryostar (subsidiary of Linde), among others. The finalisation of the contractual arrangement that would enable GRTgaz to make use of this electricity is the only obstacle that remains.

Principle behind the generation of power with an expansion turbine

Principle behind the generation of power with an expansion turbine

Principle behind the generation of power with an expansion turbine