The Benefits of Plugging-In Your Vehicle
18 Mar, 2009 04:11 pm
Plug-in Hybrid Electric Vehicles could drastically alter our conception of transportation for the better, but face potential social obstacles.
By drawing on and supplying power to the power grid, electric vehicles could displace the use of petroleum and mitigate pollution and security issues related to oil extraction, importation, and combustion. It could also improve the economics and technical performance of the electric utility industry and generate revenue to owners of PHEVs.
A PHEV uses hybrid electric vehicle technology, but it features a larger battery and a plug-in charger. Most PHEV prototypes contain a battery capable of powering the vehicle for between 20 and 60 miles (30 to 100 km) on electricity alone.
An automobile capable of V2G interaction, sometimes referred to as “mobile energy” or “smart charging,” mates a PHEV with the existing electric utility system. PHEVs must possess three elements to operate in V2G configuration: a power connection to the electricity grid, a control and/or communication device that allows the grid operators access to the battery, and precision metering on board the vehicle to track energy flows. This intelligent, two-way communication between the electricity grid and the vehicle enables utilities to manage electricity resources better, and it empowers vehicle owners to earn money by selling power back to the grid.
The V2G concept excites advocates because it offers mutual benefits to the transportation and the electric power systems. It could assist the former by reducing petroleum use, strengthening the economy, enhancing national security, reducing strain on petroleum infrastructure, and improving the natural environment. It could help the latter by providing a new demand for electricity, ideally during the parts of the day when demand remains low. Moreover, it could add capacity to the electric grid during peak times without the need for the utility industry to build new power plants.
Focusing on its benefits for the transportation sector, the U.S. Department of Transportation estimates that about 60 percent of vehicles travel fewer than 30 miles per day. A PHEV with a battery capable of a 30-mile range could therefore eliminate petroleum use for these short trips and cut overall liquid fuel use by as much as this amount. The numbers quickly add up: a transition to a V2G strategy has the potential to displace 6.5 million barrels of oil equivalent per day, or more than 50 percent of the nation’s entire oil imports.
A transition to the PHEV/V2G concept may also offer major environmental benefits. One study from the Pacific Northwest National Laboratory (PNNL) estimates that for the nation as a whole, shifting roughly half the vehicles on the road in 2007 to PHEVs would have reduced total greenhouse gas emissions by 27 percent. PNNL projected that pollution from volatile organic compounds and carbon monoxide emissions would decrease by 93 percent and 98 percent (respectively) under a PHEV transition. Total nitrogen oxides emissions would also be reduced (by 31 percent) as internal combustion engines are displaced along with the corresponding refining processes needed to fuel them.
Using a “well-to-wheels” metric, which includes the energy and greenhouse gases used in the manufacturing of the vehicle as well as its fuel cycle and operation, an Electric Power Research Institute (EPRI) study projected that the average HEV emits 22 percent less carbon dioxide than what a conventional vehicle emits. EPRI noted that when gasoline vehicles met California’s Super Ultra Low Emission Vehicle standards, an average conventional vehicle would emit 320 g/mi of CO2 over the course of its lifetime. An HEV with no all-electric range and charged only at night, in contrast, would emit 250 g/mi.
Consumers may profit from the use of PHEVs as well because electricity is cheaper than gasoline for equivalent distances traveled. Using 2006 average residential electricity prices, it would cost about $1 for a PHEV to travel the same distance as a conventional car would travel using a gallon of gasoline. If a PHEV sedan needs around three to four hours to charge per night (and a commercial delivery van around four to five hours), the electricity will cost around $170 to $215 annually. By contrast, the gasoline needed for a car to drive the same distance as the PHEV would cost more than four times as much (assuming a gasoline price of $3 per gallon). EPRI concludes that PHEVs would save about $600 per year for the average American driver.
PHEVs therefore have the opportunity to become not only vehicles, but mobile, self-contained resources that can manage power flow and displace the need for electric utility infrastructure. V2G vehicles can reduce the lifetime cost of PHEVs, thereby making them more attractive, and if V2G increases the market share of PHEVs, the benefits of PHEV use increase. Since average vehicles in the United States travel on the road only 4 to 5 percent of the day, and at least 90 percent of personal vehicles sit unused (in parking lots or garages) even during peak traffic hours, the size of a possible PHEV V2G resource can be quite large: placing just a 15 kW battery in each of the existing 191 million automobiles in the country would create 2,865 GW of equivalent electricity capacity if all the vehicles supplied power simultaneously to the grid. This amount is more than twice the total nameplate capacity of all the electric generators in the United States.
Furthermore, PHEVs in a V2G configuration could provide additional revenue to owners that wish to sell power back to the grid. V2G concept pioneer Willett Kempton and postdoctoral scholar Jasna Tomic estimated that PHEVs could provide much needed assistance to transmission operators as they maintain reliability and operating standards (known as “ancillary services). They calculated the value of those electric services at up to $12 billion per year, some of which would flow to V2G owners. Follow up business studies have projected additional annual revenue for V2G ancillary services at between $3,777 and $4,000 per vehicle.
Even the electric utility system benefits from implementing the V2G concept, not only by supplying electricity to the new vehicles, but by drawing power from them. The first benefit derives from the fact that many utility resources go underutilitized, an implication of the way utility managers have traditionally (and logically) designed the electricity infrastructure to meet the highest expected demand for power. Except for these periods of peak use, the power system could generate and deliver a substantial amount of energy needed to fuel the nation’s vehicles at only the marginal cost of fuel. About 8 to 12 percent of peak electricity demand occurs within just 80 to 100 hours during the year. Because much of the generating capacity remains unused, 84 percent of electrically powered cars, light trucks, and sport utility vehicles in the United States could be supported by the existing electric infrastructure if they drew power from the grid at off-peak times. Consequently, utility companies would earn extra revenues during these periods.
One final word of caution, however. While the benefits of a PHEV/V2G transition have been widely recognized, they have not yet been achieved, perhaps because the impediments facing such technologies remain simultaneously technical and social. Barriers relating to customer acceptance, the historical aversion to new technologies, and hearty resistance from stakeholders in the existing infrastructure may be significant impediments.
For example, V2G technologies and PHEVs may experience rejection from consumers because of their high initial cost, a serious impediment considering that most people do not discount the savings from energy efficient technologies as do financial experts. Motorists will likely be unaware of how their driving patterns and habits negatively affect V2G PHEV performance, exhibiting impatience and frustration if technologies do not perform precisely as anticipated, especially given the high expectations they developed during the years in which the vehicles have been developed. More serious resistance may come from automobile manufacturers, oil companies, and repair businesses that have sunk billions of dollars into supply and production infrastructure for conventional vehicles. One would expect these powerful industries to exert immense influence with policymakers and the public to maintain the status quo.
These latter types of barriers do not fit neatly into traditional R&D categories and remain deeply embedded in the social and institutional fabric. Overcoming them may require a substantial effort that currently eludes much discussion.
For further reading:
Duvall, M. 2002. “Comparing the Benefits and Impacts of Hybrid Electric Vehicle Options for Compact Sedan and Sport Utility Vehicles,” Electric Power Research Institute Final Report 1006892, July, available at http://www.spinnovation.com/sn/Reports/Comparing_the_Benefits_and_Impacts_of_Hybrid_Electric_Vehicle_Options_for_Compact_Sedan_and_Sport_Utility_Vehicles.pdf.
Kintner-Meyer, Michael, Kevin Schneider, and Robert Pratt. 2007. “Impacts Assessment of Plug-In Hybrid Vehicles on Electric Utilities and Regional U.S. Power Grids Part 1: Technical Analysis,” Pacific Northwest National Laboratory Report, available at http://www.pnl.gov/energy/eed/etd/pdfs/phev_feasibility_analysis_combined.pdf.
Scott, Michael J., Michael Kintner-Meyer, Douglas B. Elliott, William M. Warwick. 2007. “Impacts Assessment of Plug-In Hybrid Vehicles on Electric Utilities and Regional U.S. Power Grids Part 2: Economic Assessment,” Pacific Northwest National Laboratory Report, available at http://www.pnl.gov/energy/eed/etd/pdfs/phev_feasibility_analysis_combined.pdf.
Sovacool, Benjamin K. and Richard F. Hirsh. 2009. “Beyond Batteries: An Examination of the Benefits and Barriers to Plug-in Hybrid Electric Vehicles (PHEVs) and a Vehicle-to-Grid (V2G) Transition,” Energy Policy 37(3) (March, 2009), pp. 1095-1103, available at http://www.spp.nus.edu.sg/Faculty_Benjamin_K_Sovacool.aspx.
Tomic, Jasna and Willet Kempton. 2007. “Using Fleets of Electric-Drive Vehicles for Grid Support.” Journal of Power Sources 168, pp. 459-468, available (with many more excellent articles) at http://www.udel.edu/V2G/.