As university campuses look to decrease their greenhouse gas emissions, plug-in electric buses may provide a low carbon alternative to conventionally fossil-powered buses. This study investigates the viability for Uni...As university campuses look to decrease their greenhouse gas emissions, plug-in electric buses may provide a low carbon alternative to conventionally fossil-powered buses. This study investigates the viability for Unitrans, the bus service for the greater Davis area and the university campus, to replace current compressed natural gas buses with plug-in electric versions. This study presents an inventory of market available electric buses, their associated costs, incentives, and infrastructure concerns, and compares projected energy use, net present cost, and greenhouse gas emissions with their CNG counterparts. ADVISOR vehicle simulation software is used to estimate the energy use of a typical electric bus (New Flyer Xcelsior XE40 300 kW) and compare to the current CNG model (Orion V) along an actual Unitrans route. The model estimates that the selected bus can travel 146 miles on a single charge, with a fuel economy of 1.75 kWh per mile, which meets the service requirements. Results for bus replacement schedules between 5 and 49 in the 12-year analysis period indicate that between 1600 and 22,000 MT of carbon can be avoided. The net present cost analysis indicates that the potential savings from the replacement of a single CNG bus with an electric bus (with available incentives) ranges from $146,000 - $211,000 per bus over its lifetime, depending on infrastructure costs.展开更多
The scope of this study is to present a novel methodology for the validation of a solar parabolic trough collector simulation model,developed in System Advisor Model software,using solar field thermal performance expe...The scope of this study is to present a novel methodology for the validation of a solar parabolic trough collector simulation model,developed in System Advisor Model software,using solar field thermal performance experimental model functions that duly account for the contributions of errors that are inherent in the collection of input experimental data.The study focuses on the uncertainty associated with the predicted thermal energy output and thermal efficiency,which were calculated by using standardized testing procedures that were developed by the National Renewable Energy Laboratory and the American Society of Mechanical Engineers.Errors due to imperfections of the experimental models used throughout the test are also counted in,as well as uncertainties attributed to the variability of meteorological conditions.The experimental tests were conducted under clear-sky and steady-state conditions in Kenya,using a prototype parabolic trough collector.The uncertainty analysis provided a realistic evaluation of the thermal performance of the prototype during testing,resulting in expanded uncertainties of 9.05%(0.104 kWhth)for thermal output and 3.66%(0.0258)for thermal efficiency.Notably,the predicted thermal output and thermal efficiency from the experimental models did not exceed observed levels,demonstrating a strong correlation between predicted and observed values,supported by R2 regression coefficients of 0.972 for thermal output and 0.989 for thermal efficiency.The comparison of the two experimental model results with the simulation outcomes validated the performance of the simulation model,as the simulation results fell within the experimental error margins.Additionally,the statistical analysis yielded significant results,with root mean square error,mean bias error,and t-statistics values for thermal energy output of 0.057,0.033,and 2.135,respectively,and for thermal efficiency,0.018,0.010,and 1.993,respectively,indicating the accuracy and reliability of the simulation model.Thus,the simulation model has been successfully validated,proving its capability to accurately predict the thermal output and efficiency of the parabolic trough collector.展开更多
文摘As university campuses look to decrease their greenhouse gas emissions, plug-in electric buses may provide a low carbon alternative to conventionally fossil-powered buses. This study investigates the viability for Unitrans, the bus service for the greater Davis area and the university campus, to replace current compressed natural gas buses with plug-in electric versions. This study presents an inventory of market available electric buses, their associated costs, incentives, and infrastructure concerns, and compares projected energy use, net present cost, and greenhouse gas emissions with their CNG counterparts. ADVISOR vehicle simulation software is used to estimate the energy use of a typical electric bus (New Flyer Xcelsior XE40 300 kW) and compare to the current CNG model (Orion V) along an actual Unitrans route. The model estimates that the selected bus can travel 146 miles on a single charge, with a fuel economy of 1.75 kWh per mile, which meets the service requirements. Results for bus replacement schedules between 5 and 49 in the 12-year analysis period indicate that between 1600 and 22,000 MT of carbon can be avoided. The net present cost analysis indicates that the potential savings from the replacement of a single CNG bus with an electric bus (with available incentives) ranges from $146,000 - $211,000 per bus over its lifetime, depending on infrastructure costs.
文摘The scope of this study is to present a novel methodology for the validation of a solar parabolic trough collector simulation model,developed in System Advisor Model software,using solar field thermal performance experimental model functions that duly account for the contributions of errors that are inherent in the collection of input experimental data.The study focuses on the uncertainty associated with the predicted thermal energy output and thermal efficiency,which were calculated by using standardized testing procedures that were developed by the National Renewable Energy Laboratory and the American Society of Mechanical Engineers.Errors due to imperfections of the experimental models used throughout the test are also counted in,as well as uncertainties attributed to the variability of meteorological conditions.The experimental tests were conducted under clear-sky and steady-state conditions in Kenya,using a prototype parabolic trough collector.The uncertainty analysis provided a realistic evaluation of the thermal performance of the prototype during testing,resulting in expanded uncertainties of 9.05%(0.104 kWhth)for thermal output and 3.66%(0.0258)for thermal efficiency.Notably,the predicted thermal output and thermal efficiency from the experimental models did not exceed observed levels,demonstrating a strong correlation between predicted and observed values,supported by R2 regression coefficients of 0.972 for thermal output and 0.989 for thermal efficiency.The comparison of the two experimental model results with the simulation outcomes validated the performance of the simulation model,as the simulation results fell within the experimental error margins.Additionally,the statistical analysis yielded significant results,with root mean square error,mean bias error,and t-statistics values for thermal energy output of 0.057,0.033,and 2.135,respectively,and for thermal efficiency,0.018,0.010,and 1.993,respectively,indicating the accuracy and reliability of the simulation model.Thus,the simulation model has been successfully validated,proving its capability to accurately predict the thermal output and efficiency of the parabolic trough collector.
