Real-world Evaluation of National Energy Efficiency Potential of Cold Storage Evaporator Technology in the Context of Engine Start-Stop Systems 2020-01-1252
National concerns over energy consumption and emissions from the transportation sector have prompted regulatory agencies to implement aggressive fuel economy targets for light-duty vehicles through the NHTSA/EPA corporate average fuel economy (CAFE) program. Automotive manufacturers have responded by bringing competitive technologies to market that maximize efficiency while meeting or exceeding consumer performance and comfort expectations. In a collaborative effort between Toyota Motor Corporation, Argonne National Laboratory (ANL), and the National Renewable Energy Laboratory (NREL), the real-world savings of one such technology is evaluated. A commercially available Toyota Highlander equipped with two-phase cold storage technology was tested at ANL’s chassis dynamometer testing facility. The cold storage technology maintains the thermal state of air-conditioning evaporators to enable longer and more frequent engine off operation in vehicles equipped with start-stop functionality. Test results were analyzed and provided to NREL where a novel simulation framework was developed and calibrated to test data. The vehicle model was then exercised over a large set of real-world drive cycle and ambient condition data to estimate national-level fuel economy benefits. Results indicate that the cold storage evaporator provided national fuel consumption reductions of 0.11% relative to a conventional evaporator in the same vehicle. Additionally, when the cold storage evaporator engine stop/start was enabled for any temperature and the baseline was limited to the standard 80°F, a national fuel savings of 0.497% was found. Fuel savings result from a combination of extended engine-off duration during idle events and increased frequency of deceleration fuel cut off; both enabled by the ability of the cold storage evaporator to maintain thermal state in situations where air conditioning is active.
Jason Lustbader, Eric Wood, Michael O'keefe, Nicholas Reinicke, Jeff Mosbacher, Forrest Jehlik, Alvaro Demingo, David Cosgrove, Yuanpei Song
National Renewable Energy Laboratory, Argonne National Laboratory, Toyota, DENSO International America