Going the Extra Mile - Intelligent Energy Management of Plug-In Hybrid Electric Vehicles (6 page pdf, Kanok Boriboonsomsin, Guoyuan Wu, and Matthew Barth, ACCESS, University of California, May 2016)
Today we review some testing of energy management strategies to find the optimum use of the battery in a plug-in hybrid while minimizing the use of carbon fuel. This is in the context of the fact that electric cars are less than 1% of all cars in many parts of the USA and Canada and that in some regions of those countries (for example, California, Ontario, Quebec) electric power is produced from carbon free energy sources. Results indicate that if electric energy use is restricted to when the battery level is between 20 and 80% charged (such as in stop and go traffic or going downhill) then the fuel use is minimized. Overall gasoline consumption can be reduced by between 9 and 14% over what a normal hybrid electric car would achieve which in turn is twice as efficient as car that uses only gasoline. This is true if the power used to charge the battery some from renewable energy (hydro or nuclear).
“While hybrid electric vehicles (HEVs) rely on their internal combustion engines to recharge their batteries, PHEVs generally have larger batteries and can be recharged by plugging into an outside electricity source, such as a standard home outlet ...are potentially more efficient and cleaner than HEVs, in part because more of their energy can come from clean, renewable sources.”
“The battery in a PHEV operates best at moderate levels of SOC and is less efficient at very low or very high levels of SOC. Therefore, PHEV energy management strategies tend not to leave the battery pack empty or charge it fully in order to help preserve the battery life.”
“One …strategy is to run the PHEV solely on electric energy until its battery reaches a certain charge level, and then switch to gasoline for the rest of the trip. This strategy…may result in gasoline consumption where battery use is desirable (such as in stop-and-go traffic or while going down a steep hill)”
“Our calculation for an example commute trip shows that the intelligent energy management strategy can reduce fuel consumption by between 9 and 14 percent. This corresponds to a fuel efficiency increase from 60 to between 65 and 70 miles per gallon of gasoline equivalent.”