We are currently developing and testing plug-in hybrids, or PHEVs. PHEVs use the same powertrain as HEVs, but they are equipped with a high-capacity battery that can be charged from an ordinary household socket. While today's hybrids maintain a roughly constant battery charge, plug-ins actually discharge the battery while driving, to save fuel. PHEVs have the potential to reduce tailpipe emissions to near zero when running on battery power. However, the vehicles' overall life-cycle emissions depend on the electrical power source. PHEVs could also be significantly less expensive for consumers to operate.

In 2007 we introduced the Ford Edge HySeries PHEV prototype, which combines a plug-in battery with a hydrogen fuel cell auxiliary power unit. The Edge HySeries can be driven approximately 25 miles on pure battery power before switching over to hydrogen-assisted power. This vehicle delivers a combined city/highway gasoline equivalent fuel economy rating of 41 mpg.

Also in 2007, we launched a joint project with Southern California Edison to test a fleet of PHEVs. The project is helping us understand critical implementation issues for plug-in hybrids, including the vehicle-utility interface, the impact of plug-ins on utility operations and emissions, and the value to users, the utility company and the vehicle manufacturer. This groundbreaking project is further discussed by Nancy Gioia, head of our Sustainable Mobility Technology Group and Hybrid Vehicle Programs.

Plug-in hybrid technology is an exciting opportunity; however, significant technical challenges remain. Perhaps the most difficult is overcoming limitations in battery technology. The current HySeries system uses lithium ion batteries. This technology is preferable to the nickel metal hydride (NiMH) batteries used in the majority of today's production hybrids. NiMH batteries have limited power and energy density and, as energy requirements increase, they become cost-, volume- and weight-prohibitive. Lithium ion batteries are the preferred replacement technology; however, they will require significant advancement before plug-in hybrids can become a reality for most consumers. Lithium ion batteries currently cost too much for widespread use, and battery manufacturers are not currently prepared to produce cells in large volumes. Ford is working with suppliers to develop more cost-effective, lighter and more durable lithium ion batteries. We are also working to develop batteries that can be recycled and/or reused at the end of a vehicle's life.