SUMMARY

The development of high efficiency energy systems allows for the better allocation of humanity’s resources and the reduction of the effects of modern-day life on the environment. Recuperative solid oxide fuel cell/gas turbine hybrid power cycles are a promising class of energy system that have forecasted elevated electrical efficiencies in excess of 70% across a range of power outputs using methane fuel. Additionally, these cycles exhaust high-temperature flue gas that has a potential application as the hot-side fluid in a bottoming heat exchanger. Adding this heat exchanger to the cycle before its exhaust point modifies the system into a cogeneration cycle and allows the cycle to supply a heat output. The heat output in the bottoming heat exchanger and the power output of such a high-efficiency cycle are largely coupled with each other, but they can be decoupled by inserting a bypass valve on the hot side of the recuperator. Varying amounts of thermal energy can be made available to transfer out of the cycle as the heat output in the bottoming heat exchanger by allowing a varying amount of working fluid to bypass the hot side of the recuperator. This allows each power output to now correspond to a range of heat outputs. Therefore, the scope of this research is to simulate a recuperative solid oxide fuel cell/gas turbine cogeneration cycle with a hot side recuperator bypass valve to evaluate its ability to efficiently supply decoupled power and heat outputs across a range of values. The simulations indicate that the cycle can operate at approximately 50 – 75% electrical efficiency and 90% cogeneration efficiency across a 100 – 300 kW range of power outputs, and the operation of the bypass valve can approximately triple the natural heat output corresponding to any given power output.