July 31st, 2006

Let's Clear the Air

Plug-In Hybrids: A Developing Solution to America’s Oil Dependence

by NAFTC student worker and contributing writer Matt DeLiso

Unfortunately, as gasoline prices across the country continue to rise, wallets continue to empty. According to AAA, the average price for a gallon of unleaded gas is $2.965, and because of this, a growing number of people are looking for better options. While some have bought more fuel-efficient vehicles (i.e., Honda Civic), others have chosen to make a commitment to the environment and America’s energy independence by purchasing a hybrid.

The hybrid market is exploding with new models and a new twist on old technology, and it seems that there is no limit to its future. With each new model there is a new advancement, all aimed at improving the range of a gallon of gas with the ultimate goals of cleaner air and America’s oil independence.

A hybrid gas-electric car, such as the Toyota Prius, uses computer controls to either operate in electric mode or gas-electric mode when needed. Some believe that this technology can be taken one step further. The next generation is plug-in hybrids, which provide even better range with less fuel costs. As the name suggests, this vehicle is a hybrid that is plugged in to charge when not in use. It is estimated that it can obtain more than 1,000 miles per tank of gas in the Toyota Prius.

This plug-in Toyota Prius was converted by EnergyCS and features its EDrive system.

This plug-in Toyota Prius was converted by EnergyCS and features its EDrive system. Credit: CalCars.org

How does a plug-in hybrid achieve these numbers? It works with the combination of two systems, such as the one found in the Toyota Prius hybrid or an electric vehicle (EV). The combination of these systems equals the next evolution of hybrid technology. The vehicle can be driven around town like an EV, but the hybrid system also provides extra power for highway driving. The hybrid system supplies the necessary speed and the unlimited range that an EV does not have.

The system works by replacing the existing 1.3kWh nickel-metal hydride (NiMH) battery in the Toyota Prius with a NiMH or lithium-ion battery that is several times larger and able to provide more power to the electric motor. This enables the driver to obtain more miles per gallon (mpg), possibly up to 100 mpg or more, although this number will only be achieved if the user plugs in the vehicle at night when it is not in use.

This lithium-ion battery pack in the plug-in Prius provides power to the electric motor.

This lithium-ion battery pack in the plug-in Prius provides power to the electric motor. Credit: CalCars.org

Potential gains from a plug-in hybrid are immense. Keeping in mind that with gas currently costing $2.965 a gallon and the average Toyota Prius achieving 55 mpg, a plug-in hybrid achieves 100 mpg at $2.965 plus the additional cost of charging overnight at a rate of 9.81 cents/KWh (kilowatt hour ), according to the Federal Register. This means that an eight-hour charge is an additional 78.5 cents, so for a total cost of $3.745, the driver receives an extra 45 miles of driving range on the same gallon of gas!

The battery pack cover in the converted plug-in Prius.

The battery pack cover in the converted plug-in Prius. Credit: CalCars.org

There are a couple of obstacles with this system that have to be considered. One is that these new plug-in hybrids have a smart onboard charge that will need to operate on a standard 110V outlet. The average homeowner does not have a 220V outlet or larger in their homes, which is needed to run certain chargers. Due to this consideration, these systems will not be mass-marketed by the large automotive manufacturers because a common system to make plug-in hybrids user friendly for the average homeowner would first need to be developed.

Another possible problem is the owner occasionally forgetting to plug in the car, although this is not as big an issue as one might think. With the plug-in hybrid system, the vehicle will still run as a traditional hybrid, but will not achieve the possibility of 100 mpg. That high number is based on the vehicle being charged.

While the prospects sound great, there is one other problem: None of these systems are available yet to the public. Aside from the backyard engineers who have made their own forms of plug-in hybrids, there are no public plans by any automotive manufacturer to put these vehicles on the market, although some vehicle systems are in early development.

One company, EnergyCS, has developed an EDrive system that is in the testing stages. The EDrive plug-in hybrid system is designed to be used in 2004 or later model Toyota Prius. EnergyCS delivered the first of eight plug-in Prius vehicles to the California South Coast Air Quality Management District for testing and evaluation. The vehicle is reported to get more than 100 mpg, and the company will manufacture it for under $12,000.

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