Reliance on gasoline powered vehicles exacerbates our dependence on imported oil, while the emissions produced by the vehicle severely affect our climate. Each year four tons of CO2 produced by the average automobile is released into the atmosphere where it remains for 45 years. Making cars more fuel efficient is imperative if the effects of global warming are to be reversed.
By installing a battery, electricity can be used to propel the vehicle. When not driven, the car will be plugged into the grid to charge the battery. The battery can drive an electric motor which moves the car. This approach, called plug-in electric vehicle (PEV), will completely eliminate the combustion engine. This approach will rely on significantly improved battery technology. In the short to medium term, a smaller combustion engine may still be needed resulting in the concept of plug-in hybrid electric vehicle. In PHEV, fuel efficiency can be as high as 150 mpg.
Various studies conducted elsewhere indicate that not only will the PEV have no emissions; its total ownership cost is also cheaper than a gasoline vehicle over the life of the vehicle (12 years). During the vehicle’s life, the car owners will spend three times as much on fuel as they originally paid for the vehicles themselves. On the other hand, charging the typical electric car throughout its entire life will cost only one-third of the original battery price. By 2020, fueling a combustion car for a single year will cost more than charging an electric car for its entire life.
To be truly emission free, the electricity used to charge the PEV must be generated by green and renewable energies, such as solar and wind. Significant efforts in that area are also underway and many states now mandate 20% renewable penetrations by mid 2010s.
PHEVs can be categorized depending on their mechanical connections as parallel, series, or parallel/series. In parallel PHEVs, both the electric motor and the engine can provide power directly to the drivetrain. In a series PHEV, all the propulsion power comes from the electric motor. The engine is used only to recharge the energy storage unit; a fuel cell vehicle belongs to this group. Some mechanical setups allow the vehicle to behave as both a series and a parallel hybrid (usually via a planetary gear). Vehicles in this group are called parallel/series PHEVs. The Toyota Prius belongs to this group (shown below).
Alternatively, a series hybrid vehicle can be considered as a plug-in vehicle. All the propulsion power is produced by the electric motor in the series hybrid; therefore, the engine is turned off until the battery is discharged, thus providing true all-electric operation. These vehicles are capable of being powered solely from electricity generated on board the vehicle. The vehicles can operate as all electric vehicle even at high speeds, and will therefore provide true all electric operation. Chevy Volt vehicle will feature this setup.
Finally, the all electric vehicle will completely dispense with the on-board power generator. Such a system has a much simpler mechanical system, as there is no need for the on-board power generator or the electric motor (electric vehicle is shown below). Due to the space savings of the simpler system, there is now more space for a larger electric pack.
Electric cars represent a viable option to end our reliance on oil. We can generate electrons and send their energy directly into batteries that power efficient electric motors. Unlike engines, motors do not generate friction or heat, and provide over 90% efficiency. We can minimize greenhouse gases, save drastically on powering our automobiles, and jump-start a sustainable, powerhouse industry.
Challenges we face:
- The total US installed generation capacity is approximately 1000 GW
- There are approximately 200 million cars in the United States
- By the year 2020, if 10% of US vehicles will be some form of PHEV or PEV
- If each PHEV or PEV has a storage capacity of 30 kWh
- Vehicles are in use an average of 1 hour/day
- (10%) * (200*106 vehicles) * (30 kWh) = 600 GWh
600 GWH is both a threat to today’s utility and an opportunity. If not utilized properly, it will drive up the peak demand and may cause grid instability. If used wisely, these vehicles can become a distributed energy storage device (DESD) for the utility and hence can be dispatched to lower the peak demand, delay the construction of new power plants.
Beside significant challenges in the area of PHEV and PEV management, there is also a significant challenge in developing cheaper, lighter and better batteries. The energy density in the battery must be further improved. In addition, the power electronics technologies that interface the battery with the grid and the motor must be further improved to increase efficiency and reduce weight.