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An inferential sensor based on state estimation techniques is proposed for measuring the methanol concentration in an open-cathode direct methanol fuel cell. The strategies considered include full-state and reduced-state Luenberger observers along with a proportional-integral observer. The estimators are designed using linear dynamics derived from a comprehensive nonlinear dynamic model of an experimental open-cathode direct methanol fuel cell. A representative simulation study is used to assess the performance of the estimation schemes deployed on both the linear and nonlinear dynamic models of the system. All three estimation methods are initially tuned to deliver adequate performance on the linear model. The simulation results show that the proportional-integral state observer outperforms the other designs when the dynamics are driven away from the linear regime. It is argued that the additional robustness of the proposed proportional-integral observer design holds significant promise for use as the basis for developing an effective inferential methanol composition sensor.

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Performance of a novel gas-driven, electricity-producing heating, ventilation, and air conditioning (HVAC) system with no vapor compression and no hydrofluorocarbon (HFC) refrigerant shall be discussed in the paper. The prototype was evaluated at ORNL under a Small Business Voucher (SBV) Cooperative Research and Development (CRADA) program. The target market is commercial buildings in the United States. The goal is to mitigate or eliminate grid-power for building air conditioning, coincident peak demand and associated spinning reserves, aiding in flattening of the "duck curve". The technical goal is to transform the common packaged rooftop unit into a cost-effective distributed energy resource, opening a new range of small applications and broad markets for micro-combined cycle cooling, heating, and power with integral thermal energy storage. The test results indicate the prototype would be competitive with natural gas distributed power plants with average electrical production ranging from 45% to 60% natural gas to electricity conversion efficiency. The technology has a Primary Energy Savings Potential of 4.4 Quads, higher than any other air conditioning and heating technology.