What is a gas letdown generator (GLG)?
Gas Letdown Generators
Gas letdown Generators (GLG) use the flow of natural gas to generate electricity in a similar way to how the flow of water generates energy in a water mill. Turboexpanders are a type of gas letdown generators that generate power through pressure reduction in gaseous substances. The Anax-Star Turboexpander (ASTE) uses an axial flow turbine to reduce gas inlet pressure to a usable outlet pressure. A generator connected to the turbine generates direct current (DC) as the turbine spins, and an inverter converts the direct current to usable alternating current (AC).
How are GLGs used?
Natural gas travels through long-distance pipelines at extremely high pressure (700+ psig) and must be reduced before it can be safely distributed to end users.
There are thousands of these pressure-reduction stations across the United States that squeeze the high-pressure natural gas through a valve in order to reduce the pressure.
Pressure-reduction valves are the primary method for reducing natural gas pressure to a usable point. Despite their abundance, pressure-reduction valves are extremely inefficient; the energy used to reduce the pressure is wasted.
Instead of using a valve that wastes the pressure energy, the high-pressure gas passes through a turboexpander that harvests energy that would otherwise be wasted for power generation, much like a wind or water turbine. Pressure is still reduced, but the gas flow spins a turbine that is connected to a generator, enabling the machine to generate clean electricity from waste
GLG’s produce ‘clean’ energy because they do not burn fossil fuels and only use energy that would otherwise be wasted.