Energy and Exergy Analyses of Power Generation Cycles Using Powdered Iron as a Fuel Source

Abstract As the effects of climate change become a greater threat, the need for a viable source of sustainable energy grows daily. Iron powder has been proposed as a potential alternative to conventional fossil fuels. Pulverized iron can be burned similarly to coal. Unlike coal, however, iron combustion does not create CO2 as a by-product. It also produces a negligible amount of NOx. Iron is also abundant in the Earth's crust, has a low explosion range, possesses a competitive energy density to hydrocarbons, and reacts well with oxygen. Finally, the iron oxide produced during combustion can be collected and reduced back to iron, creating a fully sustainable process. In this analysis, different power generation cycles were analyzed to maximize the energy and exergy efficiencies as well as the work output per unit mass of iron. It was found that the power cycle that maximized both the energy and exergy efficiencies as well as the work output per unit mass of input iron was a combined power cycle, where the topping cycle was a gas turbine cycle with one-stage compression and expansion and the bottoming cycle was a steam turbine cycle with two-stage expansion and reheat. This brought the theoretical energy efficiency to 59.87%, the theoretical exergy efficiency to 65.37%, and the theoretical work output per unit mass of iron to 4422 kJ/kg. The energy efficiency decreased to 56.81% when auxiliary devices were considered.