Feasibility of advancing the development of compact energy systems

It is necessary to advance the development of compact energy systems for making energy from biomass like wood or switchgrass, as an alternative to the construction of highly capital-intensive large scale biorefineries. Compact energy systems consist of four individual components: a biomass preparation unit, a biomass converter, a fuel processor, and a powered engine. The individual unit processes within each component and the possible types of compact energy systems with different biomass converter technologies like fermentation, pyrolysis, and gasification are presented. The size, weight, and energy efficiency of upgrading biomass to energy using a compact energy system with various gasification technologies has been estimated. A compact energy system with a hydrogen fuel cell as a powered-engine component, processing 10 kg of dry biomass per day, generates a net energy (kW h) of -7.5, -30, 18.7, 13.1, and 11.7 with the super-critical, microwave assisted, catalytic, steam, and conventional gasification technologies as biomass converter technologies, respectively. The low yields of super-critical gasification and low efficacy of converting electric energy to heat via electromagnetic waves with microwave assisted gasification result in negative net energy with the respective compact energy system. Finally, the challenges and opportunities with the development of low weight, small size, and highly energy efficient compact energy systems built around gasification are discussed.