Technical and economical feasibility of the Rankine compression gas turbine (RCG)

Abstract

The Rankine compression gas turbine (RCG) is a new type of combined cycle, i.e. combined steam and gas turbine installation, that returns all shaft power on one free power turbine. The novelty of the RCG is that the steam turbine drives the compressor of the gas turbine cycle. This way, the turbine of the gas turbine acts as a free power turbine. With its free power turbine the possible field of application of the RCG is mechanical drives. The RCG can be designed with components that can all be referred to as existing technology, which makes the RCG robust and technologically feasible. Thermodynamic calculations show that a thermal efficiency of about 40% is realistic. This is higher than simple cycle gas turbines, and equal to gas turbines with a recuperator. The calculations also show that the specific power of an RCG is up to twice as high than that of both simple cycle and recuperative cycle gas turbines. Finally, economical assessments show that the extra investments of an RCG compared to a simple cycle have an expected payback time of 2–4 years. This makes the RCG economically appealing, but further study is necessary to obtain more exact figures on the economical feasibility.