Contemporary biomass-burning power systems face a number of economic constraints that have historically limited their broad adoption. Foremost among these is the cost of transporting the biomass fuel within the collection radius required to sustain the system. Many systems capable of using raw feedstocks incorporate Rankine power cycles, which are not economical in plants below 50 MWe. At this scale the collection radius becomes prohibitively large with respect to transportation costs. An alternative solution has been to transport feedstock to a processing facility where the fuel can be densified into a bio-oil. The high capital and labor costs associated with the processing facility make the fuel cost too high for electric power production. The solution presented here is a Brayton cycle system that incorporates several innovations to address the historical limitations to biomass energy production, while retaining the traditional advantages. These advantages include low operating and maintenance (O&M) costs, autonomous operation, portability, and fast starting. The relatively small size of the 1 MWe engine reduces the required feedstock collection radius to a range that is economical and practical. The engine incorporates a novel compact solid-fuel-burning combustor that is designed to emulate traditional gas-turbine can-type combustor behavior and performance, enabling the use of a broad range of biomass feedstocks. Integrated on-demand fuel processing eliminates the need for an expensive central facility and serves to dry, densify, and pulverize the feedstock for direct injection into the cycle. Additionally, bound nitrogen within the fuel is driven off as stable elemental nitrogen during the integrated fuel-processing, allowing combustion to occur with characteristically low emissions. The engine itself is designed for maximum efficiency in a back-heated configuration, wherein the cycle heat addition takes place downstream of the turbine. This arrangement protects the turbomachinery and bearings from the risk of foreign object damage (FOD) or contamination that might potentially be introduced by the variable feedstock. An overview of the full design is presented, including thermodynamic cycle models and conversion efficiencies. An operational profile is provided, including the collection radius and transportation costs associated with the solution. Test data for a scale solid biomass combustor, including emissions results, is presented.
- Advanced Energy Systems Division
A 1 MWe Low-NOx Portable Biomass-Burning Back-Heated Engine Incorporating On-Demand Fuel Processing and Solid Fuel Combustion
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Sullivan, SD, & Kesseli, J. "A 1 MWe Low-NOx Portable Biomass-Burning Back-Heated Engine Incorporating On-Demand Fuel Processing and Solid Fuel Combustion." Proceedings of the ASME 2014 8th International Conference on Energy Sustainability collocated with the ASME 2014 12th International Conference on Fuel Cell Science, Engineering and Technology. Volume 2: Economic, Environmental, and Policy Aspects of Alternate Energy; Fuels and Infrastructure, Biofuels and Energy Storage; High Performance Buildings; Solar Buildings, Including Solar Climate Control/Heating/Cooling; Sustainable Cities and Communities, Including Transportation; Thermofluid Analysis of Energy Systems, Including Exergy and Thermoeconomics. Boston, Massachusetts, USA. June 30–July 2, 2014. V002T04A006. ASME. https://doi.org/10.1115/ES2014-6439
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