Plug-in hybrid vehicles (PHEVs) are similar to regular hybrids (HEVs) except that they are able to run for significant distances at cruising speed in the all-electric mode, like a battery-electric vehicle (BEV). They can be used for daily commuting in the all electric mode not producing any emissions during the commute. Because much of their use is in the all-electric mode their fuel (gasoline or diesel) economy is in the range of 80-120 mpg. PHEVs are the most important near term solution for reducing dependency on our decreasing supplies of liquid fuels. They differ from HEVs by having a larger battery pack and a built in battery charger that lets the vehicle be plugged in to an electrical outlet for charging. They have an internal combustion engine (ICE), like a HEV and can run in the hybrid mode while their batteries are being charged by the engine. Extended trips are made in the hybrid mode, thus not having the the limited range of a BEV. It is usually assumed that a range of 20-30 miles in the all electric mode would be sufficient for most commuting. The all-electric range is strictly a function of the size of the battery pack and the speed at which you are traveling. In longer trips in a PHEV, the fuel mileage would be higher than an HEV because the larger batteries could absorb more power from regenerative braking and coasting, as well receiving a significant amount of power from their batteries.
In addition to eliminating emissions during commuting where they are of most concern, PHEVs cost less to operate because they are using electricity for power much of the time, rather than gasoline. Electricity is less expensive because: 1) it is produced by a more efficient process than burning gasoline in an ICE and 2) its power is derived from a less expensive form of energy than gasoline, the majority from coal. 3) because the vehicles would be charged overnight they would be eligible for an off-peak rate. This also would minimize the impact on generating capacity.
While coal is not presently the most environmentally friendly source of energy, the transition to lower emission power plants has started, several "Clean Coal" demonstration plants have been built and bids are being solicited for the first all commercial clean coal plant. However, clean coal plants do not solve the environmental issues resulting from coal mining which also have to be addressed. Unfortunately, despite these concerns the more urgent need is to reduce our dependence on liquid fuels which are becoming in short supply. The sustainability of our economy is dependent on a viable transportation system. Mass transit systems and electrical generation from renewables are much more dependent on governmental actions and the impetus for this must come from the voters.
No PHEVs are available for sale by an automobile manufacturer. DaimlerChrysler, see below, is developing a PHEV version of its Sprinter delivery van with customer tests scheduled for this year. EDrive sells retrofit PHEV systems for the Prius at a substantial cost. They "plan to seek investment in their technology in order to establish a production facility, and once this is accomplished, pricing and production schedules will be available on their web site." Several organizations and publications have published information and articles supporting PHEVs. The Electric Power Research Institute (EPRI) has published a series of reports advocating the development of PHEVs. Set America Free supports PHEVs as a main point in their energy policy. The New York Times (April 3, 2005 $2.95) and Business Week (April 11, 2005) had articles supporting PHEVs.
According to EPRI Report #1009299, section 1, even at current battery prices, the total lifetime cost of a PHEV is not only lower than a CV, it is lower than that of a HEV. I offer the following three observations on this statement: 1) their results are so sensitive to the assumptions that they have made, that for all practical purposes there is little difference in the life cycle costs of a CV, HEV or PHEV that they calculated for a midsize sedan. For the SUV the differences are more significant, but still within the range of possible divergence 2) the average owner of a car is unlikely to own the car for 150.000 miles which is necessary to achieve the benefits that they calculated 3) as battery costs are reduced the differences between the HEV and PHEV dramatically decrease. That said there are enough other benefits to owning a PHEV to justify buying it. The following list taken from the EPRI Report #1000249, p 2-17, sums up these benefits in descending order of importance as determined by a consumer survey:
- Fuel cost savings
- Reduced maintenance (costs and personal time)
- 50% longer range
- Convenience of overnight charging and not having to go to a filling station
- Better handling due to balanced weight distribution
- Environmental benefits due to lower emissions and less global warming gases
- Better handling due to lower center of gravity
- Quieter at stops and during acceleration
- Reduced dependence on foreign oil
- Less vibration and fatigue at stops and during acceleration
Many of these items also apply to a HEV. One question I have is: even if the life cycle cost is lowest for the PHEV, how many people are going to consider life cycle cost when buying a car, but rather make their decision based on lowest sticker price? It is disappointing, but not surprising, to see reduced dependence on foreign oil so low on the list. I guess we have to work harder to get the word out; that oil depletion is real, it is here and we have to reduce our dependence on oil. Until this becomes common knowledge to the general public, we face an uphill climb in progressing through The Energy Revolution.
DaimlerChrysler (free registration required) is developing both a PHEV and a HEV version of its Sprinter 311 CDI (diesel) delivery van. Development of the PHEV is relatively far advanced. This vehicle is equipped with a 70 kW electric motor powered by nickel-metal hydride or lithium-ion batteries (14 kWh capacity). Lithium Ion batteries reduce the weight of the vehicle by 420 lb (190 kg), but currently at significantly higher costs. The van can be operated in either of two hybrid modes or the all electric mode. At low speeds in the all electric mode the van can make quiet, emission free deliveries in pedestrian zones, at hospitals or in convention centers. When operating in the electrical mode, the vehicle has a range of up to 18 miles (30 kilometers). Customer tests on two fleets of the PHEV are scheduled to begin this year, one in the U.S. and one in Europe. As reported in the Green Car Congress, the Austin, TX mayor and city council have supported purchase of Sprinter vans and have considered approaching other cities to join Austin in placing a large bulk order for Sprinters.
A Toyota Prius has been modified by Energy CS , earlier post, by replacing the standard 1.3 kWh NiMH batteries with a 9kWh Lithium-ion battery pack. With this modification, the car, if carefully driven, can get between 120 -180 mpg (ignoring the contribution of electricity). For the first 60 miles it can be driven in the all electric mode and then, when the battery gets low, it automatically switches to the regular hybrid mode, getting about 50 mpg. The cost implications are greater than might be expected, at $0.10 per kWh of electricity, they claim that it costs you only 72 cents to travel the first 60 miles. This car is similar to the one being offered for sale by EDrive, referred to above.