Natural gas comes out of the ground at a very high pressure, called Geo-pressure. It is this pressure that moves the gas through the pipelines of the gas distribution system. However, the pressure is too high to be used safely by end-users of gas (power stations, industrial, commercial and domestic users).
The pressure at the production platform is between 100-800 bar. In order for the gas to be suitable for domestic use it will have to be available at 1 bar (the pressure of the gas used by a cooker for example).
At several points in the system, therefore, gas goes through ‘pressure reduction stations’, where the pressure of the gas is reduced by squeezing it through a valve. Reducing the pressure in this way releases energy. In most instances this energy is presently not being harnessed though it is possible to generate carbon free electricity, merely by installing a turbine generation system at some of these stations.
The gas passes through this turbine as the Geo-pressure is reduced, and the turbine generates electricity. No gas is burned or used up in this process. It is similar to hydro-power, it is the flow of the water that turns the turbine or mill, but the water itself is unchanged by the process.
As it is not the gas but the actual pressure reduction which produces energy, Geo-pressure also applies to other fluids where pressure is reduced such as for example with geo-steam.
Geo-pressure is a travelling companion of natural gas
Geo-pressure follows the electrical base load demand
The amount of electricity that can be generated from a pressure reduction station depends on the required pressure drop and flow.
Cryostar designs and builds turbines to customer requirements in the Geo-pressure industry. Our radial inflow turbines are suitable for this application as these have high reliability and an efficiency up to 92% ensuring that optimal energy recovery is achieved.
Use the Cryostar Geo-pressure calculator to estimate the level of potential electricity generation.
In the Geo-pressure energy recovery unit in Arlesheim (GVM) commissioned by Cryostar in 2003, to reduce the natural gas pipeline pressure of 55 bar to meet the low pressure of the local gas distribution networks, a pressure drop is needed. In other words, the gas flow from 35,000 Nm3/h is allowed to expand and during this process drives the Cryostar turbines within the Geo-pressure energy recovery unit.
The turbine wheel drives a gearbox coupled to a synchronous generator. The resulting 1,9MW of electricity recovered in this way is then supplied to local electricity suppliers. The electrical efficiency of the whole installation is about 85%, vastly superior value when compared to CHPs, gas and steam turbines and even fuel cell.
Cryostar Group
Natural gas comes out of the ground at a very high pressure, called Geo-pressure. It is this pressure that moves the gas through the pipelines of the gas distribution system. However, the pressure is too high to be used safely by end-users of gas (power stations, industrial, commercial and domestic users). 
