Compressed natural gas for power
Compressed natural gas (CNG) can now be used as a fuel for gas-fuelled captive power plants. Natural gas as fuel source has a significant number of benefits versus diesel including reduced emissions and reduced fuel costs.
However in many parts of the world the gas distribution network is not fully developed and does not reach all of the prospective customers. There may be plans to expand the gas distribution network at a later stage, or a customer may want to make use of the cost and environmental benefits of gas.
In this instance CNG may be an attractive source of fuel. CNG is made by compressing natural gas and is composed primarily of methane (CH4). Unlike natural gas it is not typically transported in pipelines, instead it is transported in batches and contained and distributed in cylinders under pressure over 200bar.
CNG’s energy density is significantly higher than natural gas as there are more CH4 molecules stored in a smaller area.
Prior to use in a gas engine, the gas must be decompressed and fed into the generator typically at an operational pressure of 80-200mbar.
Depending upon the price of natural gas compared to diesel and the distance which the gas has to be transported from the point of compression, the fuel savings can be in the region of 30%. This is therefore a significant driver for the adoption of this technology. It can also act as a stop-gap until pipeline gas is available in a given area, if the developer does not wish to make the capital investment in diesel fuelled electricity generators.
As with other gas engine technology CNG-fuelled facilities can improve their fuel efficiency through the cogeneration of heat and power.