US National Research Council Report Finds Plug-in Hybrid Costs Likely to Remain High; Fleet Fuel Consumption and Carbon Emissions Benefits Will Be Modest for Decades
|NRC projections of number of PHEVs in the US light-duty fleet. Click to enlarge.|
Costs of light-duty plug-in hybrid electric vehicles (PHEVs) are high—largely due to their lithium-ion batteries—and unlikely to drastically decrease in the near future, according to a new report from the National Research Council (NRC). The Research Council is the principal operating agency of the US National Academy of Sciences and the National Academy of Engineering.
The report considers two PHEV configurations: 10-mile all electric range (PHEV-10) and 40-mile all-electric range (PHEV-40). The PHEV-10, similar to the Prius Plug-In (earlier post) has a larger battery pack than an HEV to allow 10 miles of driving powered by electricity only and a gasoline engine that drives the wheels in parallel with the electric motor when power demand is high or the batteries are discharged.
The other vehicle, the PHEV-40, is similar to the Chevrolet Volt (earlier post). It has a 40-mile electric range, a larger electric motor, and a much larger battery than the PHEV-10. In the PHEV-40, the electric motor provides all the propulsion; the gasoline engine drives a generator that powers the motor and keeps the batteries charged above some minimum level.
The cost to the manufacturer of producing the first generation of the PHEV-10 (2010–2012) is expected to be about $6,300 more than that of the equivalent conventional mid-size car (non-hybrid), including $3,300 for the battery pack. Similarly, the PHEV-40 with a $14,000 battery pack would cost about $18,100 more.
The lithium-ion battery technology used to run these vehicles is the key determinant of their cost and range on electric power. Costs will decline with technology improvements and economies of scale, but Li-ion batteries are already being produced in great numbers for consumer devices and are well along their learning curves, according to the NRC report. The steep early drop in cost often experienced with new technologies is not likely. The cost to manufacture these vehicles is expected to decline by about one-third by 2020 but only slowly thereafter.
It is possible that breakthroughs in battery technology will greatly lower the cost. At this point, however, it is not clear what sorts of breakthroughs might become commercially viable. Furthermore, even if they occur within the next decade, they are unlikely to have much impact before 2030, because it takes many years to get large numbers of vehicles incorporating new technology on the road.
—“Transitions to Alternative Transportation Technologies—Plug-in Hybrid Electric Vehicles”
Penetration rates for the PHEV-10 and the PHEV-40 were compared to a Reference Case that assumes high oil prices and fuel economy standards specified by EISA 2007 (with modest increases after 2020, when those standards level off), as described in the 2008 Hydrogen Report from NRC. The maximum practical scenario is the fastest rate at which the committee concluded that PHEVs could penetrate the market considering various manufacturing and market barriers; it leads to about 40 million PHEVs by 2030 in a fleet of about 300 million vehicles.
However, factors such as high cost, limited availability of places to plug in, and market competition suggest that 13 million is a more realistic number, the report says. Even this more modest estimate assumes that current levels of government support will continue for several decades. Subsidies in the tens to hundreds of billions of dollars over that period will be needed if plug-ins are to achieve rapid penetration of the US automotive market.
Most of the electricity used to power these cars will be supplied from the nation’s power grid. If charged at night when the demand for electricity is lowest, the grid would be able to handle the additional demand for millions of plug-in hybrid electric vehicles, the report says. However, if drivers charge their vehicles at times of high demand, such as when they get home from work, the additional load could be difficult to meet unless new capacity is added.
Smart meters, which bill customers based on time of use, may be necessary in order to encourage nighttime charging. In addition, some homes would require electrical system upgrades to charge their vehicle, which could cost more than $1,000.
|Gasoline use for PHEV-10s and PHEV-40s introduced at the Maximum Practical rate and the Efficiency Case from the 2008 Hydrogen Report. Click to enlarge.|
Relative to hybrid vehicles, plug-in hybrid electric vehicles will have little impact on US oil consumption before 2030, especially if fuel economy for conventional vehicles and hybrids continues to increase past 2020. PHEV-10s save only about 20% of the gasoline an equivalent hybrid vehicle would use, the report says.
If 40 million PHEV-10s are operating in 2030, they would save about 0.2 million barrels of oil per day relative to less expensive hybrids, approximately 2% of current US daily light-duty vehicle oil consumption. More substantial savings could be seen by 2050. PHEV-40s, which consume 55% less gasoline than hybrids, could have a greater impact on oil consumption.
Plug-in hybrid electric vehicles emit less carbon dioxide than equivalent conventional vehicles, but not less than hybrids after accounting for emissions at generating stations supplying their electrical power, the report says. Beyond 2030, assuming consumer acceptance, plug-in hybrid electric vehicles could account for significant reductions in US carbon dioxide emissions, if electricity generation plants fired by fossil fuels were equipped with carbon capture and storage systems or replaced with renewable energy or nuclear-powered plants.
According to the report, a portfolio approach toward reducing US dependence on oil is necessary for long-term success. This should include increasing the fuel efficiency of conventional vehicles and pursuing research, development, and demonstration into alternative strategies, including the use of biofuels, electric vehicles, and hydrogen fuel cell vehicles.
This study was sponsored by the US Department of Energy. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter.