In this paper, a hybrid turboexpander-fuel cell (TE-FC) is investigated for extraction of electrical energy from high pressure gas in which the fuel cells are used for preheating the gas. Combination of expanders and fuel cells will reduce the fuel consumption and greenhouse gas emission. This study reveals that there are some circumstances in which the use of fuel cells in conjunction with a turboexpander is not recommended from an economic point of view. This paper seeks the region in which utilization of fuel cells along with a turboexpander presents maximum economic profit. Using the strategy provided in this paper one can decide whether to invest in the hybrid fuel cells-turboexpander or individually planned turboexpander with a conventional gas fired preheating system. Almost all effective parameters are taken into account and this can be considered a superiority of the present paper.

These days, extensive efforts are being carried out to improve energy efficiency and energy recovery in various energy systems, such as extraction of energy from the high-pressure natural gas (NG) in pressure reduction stations (PRSs) employing a turbo-expander (TE). In conventional PRSs, NG pressure reduction is carried out by pressure regulators, leading to the loss of mechanical exergy available in the pressurised NG as heat. Thus, replacing a pressure regulator with TE allows the extraction of the mechanical exergy to change into electrical form of energy by coupling with a generator. So, a novel configuration is presented here for grid-connected microgrid based on TE. Furthermore, a new procedure is developed for optimal capacity sizing of energy resources in the proposed TE-based microgrid. Finally, optimisation results (with and without TE) and economical considerations are discussed.

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