Inevitably, there are some cost consequences associated with the installation of such a system. An inlet heat exchanger is required in order to take advantage of this characteristic of the gas turbine. However, there are many sites that already feature an inlet heat exchanger for the purpose of cooling the inlet air, as conventional thermodynamics rules dictate.
Therefore, little capital investment is required to install the necessary pipes and valves to reverse the flow through the inlet heat exchanger from cold to hot, and to install the appropriate controls. Such a system does not require any internal modifications to the gas turbine, and most of the physical installation either exists or can be developed while the machine is in operation. Indeed, such an installation has a relatively low impact on outage schedules and should fit within a standard service window.
Counterintuitively, there are multiple benefits associated with heating intake air. For example, the machine can achieve a more efficient part-load operating regime, which enables fuel savings while running in conditions other than base load. Such a machine may also turn down further, enhancing operator flexibility. This allows operators to move higher up the dispatch stack in a competitive market and ultimately run for more hours per year. This is critical in places where renewables are otherwise dominant and cause many thermal plant operators to shut down for considerable periods in every 24-hour cycle.
The additional ramp-down capability enabled by preheating intake air can also reduce the number of start-stop cycles and even hot starts, which have a substantial impact on service life. This may significantly reduce the costs of maintenance and avert the costs of restarting.
For asset managers, shutting off a gas turbine can cost more than running it at close to zero output, and that is a trade-off that must be considered. From a thermodynamic standpoint, preheating inlet air goes against everything most asset managers have ever learned. But for efficient operation at part-load outputs, it works.