A 10 Kilowatt, Rankin Cycle Agricultural Waste to Energy Conversion Module Utilizing Ultra Micro Turbo-Alternators

In 2011, there were 60,000 dairy farms in the US. Of there, 56,600 had herds of fewer than 500 animals. Currently, manure digester installations are only considered economical for herds of at least 500 animals. There require turbine or diesel generator sets of 100 Kilowatt size and larger. The need exists for a smaller waste to energy conversion approach for implementation on small farms were methane is typically released, unburned and unutilized, to the environment. This project evaluates the feasibility of an electrical-power-generating system based upon a steam Rankine cycle, sized and designed to burn untreated digester gas from small animal herds. The system uses a residence-sized boiler, modified to produce higher operating temperature and pressures to improve cycle efficiency. The steam from the boiler powers a unique turbo-alternator spinning on fluidically-damped gas bearings, also energized by system steam. The analysis and studies conducted in Phase I showed feasibility of the steam Rankine system and fluidic bearing turbo-alternator approach. Key features which were analyzed and/or demonstrated are a follows: A Rankine Cycle system may be scaled to herd of only 25 cows. A representative turbine rotor is capable of high speed operation when spinning of fluidically-damped gas bearings. Fluidic bearing operation was demonstrated using system steam. A closed system with fluidic bearings is capable of high efficiency, simplicity, reliability and long life. Electrical power generation efficiency of nearly30% is achievable. Combined Heat and Power (CHP) efficiency greater then 90% is achievable. Price of a Rankin CHP system may be as low as $500/kilowatt. We estimate a market for 90,000 10-kilowatt digester gas to electrical power modules for hears of 500 cows or fewer. Our agricultural CHP unit may be applied to provide all the power needs for the farm or an average home, and it may be simply modified to also burn natural gas. 30 to 50 million homes in North America are candidates for CHP. The high volume potential of the residential market can provide a great reduction in manufacturing costs, allowing us to meet our $500/kilowatt price target for CHP modules for small digesters. The first year Phase II effort will be concentrated on turbo-alternator design and development. A mass-producible, high-pressure boiler and development of a CHP manufacturing and distribution partner will be a new emphasis in the second year as part of the commercializat