3
U.S. Electric Power Infrastructure

PHEVs require electric power to charge their onboard batteries. Unlike fuel cell vehicles, which would require a brand new supply infrastructure, PHEVs have a ready and well-established energy source—the U.S. electric power system. This vast system includes a variety of fuel sources and generation technologies, a nationwide transmission network, and distribution operations that reach almost all Americans.

This chapter begins with a brief overview of the current system. It then describes two projections of how the system might evolve by 2050, one based on current policy and the other representing a concerted effort to reduce U.S. CO2 emissions. This section also discusses the charging of PHEVs and its potential impact on the electric system. Finally, it introduces several issues that are relevant but beyond the scope of this study.

U.S. ELECTRIC POWER SYSTEM

The nation’s 1 million megawatts (MW) of electric generating capacity produced over 4 billion megawatt-hours (MWh) in 2007 (EIA, 2009b). In comparison, 1 million PHEVs charging an average of 3 kWh every day for a year would consume only about 1 million MWh.1 The U.S. electric system can clearly handle a great many PHEVs, but there is one caveat. Electricity demand varies throughout the day and over the year. Demand usually peaks on hot afternoons when summer air conditioning loads are highest. On such days, some systems are seriously stressed—sometimes to the point where they have to shed loads (reduce demand) to avoid collapse.

In recent years, the North American Electric Reliability Corporation (NERC) has raised concerns about the reliability and development of the electric power system. In its 2007 report, NERC noted that “projected increases in peak demands continue to exceed projected committed resources beyond the first few years of the 10-year planning horizon” (NERC, 2007). In its 2008 report, NERC said that “while some progress has been made, action is still needed on all of the issues identified in last year’s report to ensure a reliable bulk electric system for the future” (NERC, 2008).

Charging a large number of PHEVs during peak hours could aggravate a potentially serious problem, possibly increasing the risk of brownouts and other power system disruptions that could adversely impact the public’s interest in PHEVs. Currently, electric system capacity is generally adequate, but as the economy recovers, demand will increase, stressing the system unless new generating and transmission capacity is built.

At the outset, the key to integrating PHEVs will be to encourage off-peak charging. Generation and transmission capacity must be adequate to handle peak loads, but most of the time, demand is much lower. Utilities would greatly prefer that PHEVs be charged at night, when they can employ their otherwise underutilized capacity or purchase power at lower rates. Many utilities offer time-of-use (TOU) rate structures to at least some of their residential customers, with lower rates at night than during peak hours.

Many plug-in hybrids can be charged with available power generation and grid capacity during off-peak hours. An analysis by the Pacific Northwest National Laboratory estimated that a PHEV fleet equal in size to 84 percent of all cars and light trucks on the road in 2001 could be charged during off-peak times without building new electric generation capacity (PNNL, 2007).

The picture is different if PHEVs are charged during peak hours. For example, a study by Southern California Edison concluded that PHEVs could account for as much as 11 percent of its system load by 2020, which could increase peak loads by several thousand megawatts if PHEV charging is not properly managed.2

1

As analyzed in this report, a PHEV-10 has usable storage capacity of about 2 kWh, and a PHEV-40 has about 8 kWh.

2

D. Cromie and B. Graham, Transition to electricity as the fuel of choice, Southern California Edison, presentation to the committee, May 2009.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 17
3 U.S. Electric Power Infrastructure PHEVs require electric power to charge their onboard beyond the first few years of the 10-year planning horizon” batteries. Unlike fuel cell vehicles, which would require a (NERC, 2007). In its 2008 report, NERC said that “while brand new supply infrastructure, PHEVs have a ready and some progress has been made, action is still needed on all of well-established energy source—the U.S. electric power the issues identified in last year’s report to ensure a reliable system. This vast system includes a variety of fuel sources and bulk electric system for the future” (NERC, 2008). generation technologies, a nationwide transmission network, Charging a large number of PHEVs during peak hours and distribution operations that reach almost all Americans. could aggravate a potentially serious problem, possibly This chapter begins with a brief overview of the cur- increasing the risk of brownouts and other power system rent system. It then describes two projections of how the disruptions that could adversely impact the public’s interest system might evolve by 2050, one based on current policy in PHEVs. Currently, electric system capacity is generally and the other representing a concerted effort to reduce U.S. adequate, but as the economy recovers, demand will increase, CO2 emissions. This section also discusses the charging stressing the system unless new generating and transmission of PHEVs and its potential impact on the electric system. capacity is built. Finally, it introduces several issues that are relevant but At the outset, the key to integrating PHEVs will be to beyond the scope of this study. encourage off-peak charging. Generation and transmission capacity must be adequate to handle peak loads, but most of the time, demand is much lower. Utilities would greatly U.S. ELECTRIC POWER SYSTEm prefer that PHEVs be charged at night, when they can employ The nation’s 1 million megawatts (MW) of electric gen- their otherwise underutilized capacity or purchase power erating capacity produced over 4 billion megawatt-hours at lower rates. Many utilities offer time-of-use (TOU) rate (MWh) in 2007 (EIA, 2009b). In comparison, 1 million structures to at least some of their residential customers, with PHEVs charging an average of 3 kWh every day for a year lower rates at night than during peak hours. would consume only about 1 million MWh.1 The U.S. elec- Many plug-in hybrids can be charged with available tric system can clearly handle a great many PHEVs, but there power generation and grid capacity during off-peak hours. is one caveat. Electricity demand varies throughout the day An analysis by the Pacific Northwest National Laboratory and over the year. Demand usually peaks on hot afternoons estimated that a PHEV fleet equal in size to 84 percent of all when summer air conditioning loads are highest. On such cars and light trucks on the road in 2001 could be charged days, some systems are seriously stressed—sometimes to the during off-peak times without building new electric genera- point where they have to shed loads (reduce demand) to tion capacity (PNNL, 2007). avoid collapse. The picture is different if PHEVs are charged during peak In recent years, the North American Electric Reliability hours. For example, a study by Southern California Edison Corporation (NERC) has raised concerns about the reli- concluded that PHEVs could account for as much as 11 per- ability and development of the electric power system. In its cent of its system load by 2020, which could increase peak 2007 report, NERC noted that “projected increases in peak loads by several thousand megawatts if PHEV charging is not properly managed.2 demands continue to exceed projected committed resources 1As 2D. analyzed in this report, a PHEV-10 has usable storage capacity of Cromie and B. Graham, Transition to electricity as the fuel of choice, about 2 kWh, and a PHEV-40 has about 8 kWh. Southern California Edison, presentation to the committee, May 2009. 

OCR for page 17
 TRANSITIONS TO ALTERNATIVE TRANSPORTATION TECHNOLOGIES—PHEVS The committee assumed that most PHEV charging will Other be accomplished at night, when electric power demand is Hydro- renewables lower and rates are likely to be lower than during the day. 2% electric Encouraging PHEV owners to charge their vehicles during 6% off-peak hours will require both rate schedules that reward time-appropriate charging and equipment that can moni- Nuclear tor—or even control—time of use. Under the Energy Policy 20% Act of 2005, utilities are “required to move towards smart Coal meters that allow time-of-day pricing,” and smart meters 50% are already being installed in certain areas to improve elec- tric service, encourage efficiency, and shift energy use to off-peak hours. Many utilities are planning to deploy smart meters within the next few years. Natural gas Petroleum Modernizing the transmission grid to achieve a smart 20% grid as well as distribution systems would also benefit 1% PHEVs by improving reliability, accommodating daytime charging, helping reduce carbon emissions, and controlling FIGURE 3.1 Net generation of U.S. electric power industry, 2007. SOURCE: EIA, 2009b. costs (NAS-NAE-NRC, 2009). DOE recently released a solicitation offering $3.9 billion in grants to “modernize the electric grid, allowing for greater integration of renewable Figure 3-1 energy sources while increasing the reliability, efficiency and THE SYSTEm OUT TO 2030 AND BEYOND R01653 security of the nation’s transmission and distribution system” redrawn (DOE, 2009a). vector editable Energy Information Administration Projection In its scenario analysis, the committee examined two one column (Business as Usual) cases that bracket the national average residential rate of 10.4 cents per kWh (EIA, 2009a) and that represent likely From 2000 to 2007, average electricity demand increased PHEV charging rates: 8 cents per kWh and 15 cents per kWh. by 1.1 percent per year. The 2009 EIA Reference Case The former would apply in areas with residential TOU rate projects electricity demand increasing by 26 percent from structures; the latter would be in areas where rates are high 2007 to 2030—about 1.0 percent per year on average. The or if they rise, perhaps because electric power generation is largest increase is in the commercial sector (38 percent), decarbonized. where service industries continue to lead demand growth, CO2 will be emitted from power plants that generate the followed by the residential sector (20 percent) and the indus- electricity that replaces gasoline that PHEVs do not require trial sector (7 percent) (EIA, 2009a). EIA also provides low relative to conventional vehicles. As shown in Figure 3.1, the and high growth cases for 2030. Figure 3.2 compares the gen- primary sources of electric power in 2007 were coal, natural eration mix for the three cases in 2030 with the 2007 case. gas, and nuclear energy. From 1997 through 2007, these three EIA’s Reference Case projects that the average retail price sources provided between 84.6 and 89.5 percent of total net for electricity in 2030 will be very close that of 2008, 10.4 generation. Nuclear power generation releases no CO2, but cents per kwh, with the high growth case at 10.8 cents and coal and (to a lesser extent) natural gas do.3 the low growth at 9.7 cents per kwh. These modest price dif- CO2 emissions by U.S. electric generators and combined ferences are unlikely to have a material influence on PHEV heat and power facilities in 2007 were 2,517 million metric economics and acceptance. tons (EIA, 2009b), or an average of about 1.3 pounds of It should be noted that EIA forecasts are required to CO2 per kWh. One kWh will take a small electrically driven assume the continuation of existing policy, so no substantial car about 5 miles. Over the same distance, an equivalent efforts to reduce CO2 emissions from electric generation gasoline-powered car that gets 30 miles per gallon (mpg) were included. The committee used the EIA projections for would emit 3 pounds of CO2, more than twice as much. An its business-as-usual scenario. HEV at 50 mpg would release about 2 pounds. An Alternative View: EPRI/NRDC (Policy Driven) For PHEVs to deliver their full potential to reduce CO2 emissions, the electricity used for charging them must be generated from technologies such as nuclear, renewable energy (e.g., solar, wind), and fossil fuels with carbon cap- ture and sequestration. Because government policies will be 3Some CO2 is released from the nuclear fuel cycle, but the amount required to drive these changes, the rate at which the country per kWh generated is small relative to fossil-fired power plants.

OCR for page 17
one-column size below  U.S. ELECTRIC POWER INFRASTRUCTURE Home Charging 6,000 Charging a PHEV may be a simple matter of finding 5,000 a suitable electrical outlet (most likely in a home garage) Billion kilowatt-hours Renewables and plugging in. In other cases, however, it will be more 4,000 Nuclear complicated. The time required to charge a PHEV at regular 3,000 Natural Gas household voltage may be quite long, so a voltage upgrade Petroleum may be necessary. Zoning codes or standards may require 2,000 Coal upgraded or dedicated service for PHEVs, and PHEV- 1,000 friendly, off-peak charging may require the installation of dedicated charging circuits and/or meters. 0 2007 reference low fossil high fossil One recent study considered three levels for PHEV charg- 2030 ing (Morrow et al., 2008): FIGURE 3.2 Electric generation by fuel in four cases: 2007 and • Level 1 charging uses a standard 110 volt, 15 to 20 2030 (Reference Case, high growth, low growth). SOURCE: EIA, ampere circuit, standard in residential and commercial 2009a. buildings. Level 1 provides relatively little power and may necessitate prolonged charge times. • Level 2 charging involves a 220 volt, single-phase, 40 ampere circuit. At the higher voltages and currents, charg- moves toward this greener power generation mix remains ing would be more rapid, but Level 2 service is not common uncertain. in residential garages and would generally entail a system An alternative set of scenarios for U.S. power genera- upgrade. tion was developed jointly by the Electric Power Research • Level 3 charging uses a 440 volt, three-phase circuit Institute (EPRI) and the Natural Resources Defense Council supplying 60-150 kW of power and can deliver a 50 percent (NRDC) to explore the relationship between the grid and charge in 10-15 minutes, depending on vehicle size and PHEVs if it becomes necessary to lower CO2 emissions electrical range. Level 3 charging might be the choice for from U.S. electric power generation (EPRI/NRDC, 2007). public garages, parking lots, and shopping centers. Nine modeling scenarios were developed spanning high, medium, and low emissions of CO2 and low, medium, and The committee has considered charging only at Levels 1 high penetrations of the fleet by PHEVs. Chapter 4 compares and 2, believing that charging at Level 3 will not become greenhouse gas (GHG) emission intensities of the EIA Refer- important until much later. Table 3.1 provides estimated ence Case with the EPRI/NRDC medium case. charging times for representative PHEVs and charging Among other things, EPRI and NRDC concluded that stations. Costs per charging station were estimated (num- all nine cases showed significant GHG reductions attribut- bers rounded by the committee) as follows (Morrow et al., able to PHEV fleet penetration. Cumulative GHG savings 2008): from 2010 to 2050 could be significant, ranging from 3.4 to 10.3 billion MT of CO2.4 • Residential garage charging Recognizing that reductions of this magnitude are not —Level 1, $880 likely to occur without public policy intervention, the com- —Level 2, $2,100 mittee used the EPRI/NRDC results to illustrate the potential • Apartment complex charging benefits that PHEVs might provide under a policy-driven —Level 1, $830 low-emission grid scenario. —Level 2, $1,500 • Commercial facility charging —Level 2, $1,900 CHARGING THE BATTERIES If a dedicated circuit is not required, many PHEVs can At the time this report was prepared, manufacturers had be charged with little or no change to an owner’s electri- not announced whether they would equip PHEVs for charg- cal service. Although significant upgrades in the electrical ing at both 110 and 220 volts. The committee believes, distribution system might be required for a large PHEV however, that the additional cost for dual voltage vehicle population, utility planners should have sufficient time to charging is probably small and not likely to significantly prepare for these changes. affect the committee’s analysis. In summary, some PHEV owners may be able to charge their vehicles using their existing home electrical service, but many others probably will not. The cost of upgrading 4Total CO 2 emissions from gasoline in the transportation sector currently equal about 1.2 billion metric tons per year.

OCR for page 17
0 TRANSITIONS TO ALTERNATIVE TRANSPORTATION TECHNOLOGIES—PHEVS TABLE 3.1 Approximate Charging Time as a Function of recently awarded a stimulus grant of nearly $100 million from Vehicle Size and Electric Driving Range (hours) the Department of Energy to build 12,800 charging stations for electric vehicles and PHEVs in Arizona, Washington, PHEV-10 PHEV-20 PHEV-40 Oregon, California, and Tennessee (DOE, 2009b). Level 1 Economy vehicle 2.7 5.5 11 ADDITIONAL ISSUES Midsize vehicle 3.6 7.3 14 Light-duty truck/SUV 4.5 9.1 18 The committee identified some related issues that are Level 2 beyond the scope of this study and will require detailed Economy vehicle 0.5 1 2 assessment to understand the impact of PHEVs on the grid Midsize vehicle 0.7 1.3 2.7 and vice versa: Light-duty truck/SUV 0.8 1.7 3.3 NOTE: Numbers rounded by the committee. • Outlet access. An accurate estimate is needed of the SOURCE: Morrow et al., 2008. number of existing homes and buildings where charging would be easy. About 35 percent of housing units do not have a garage or carport, which is probably essential for home service to allow PHEV charging, whether desired or an outlet for home charging (Bureau of the Census, 2008). required, is estimated to range from slightly less than $1,000 PHEV owners without ready access to an outlet would need to slightly more than $2,000. PHEV-40s are more likely to a public charging infrastructure; it is uncertain how many need costly new circuitry for 220 volts. consumers would be willing to rely on public charging. PHEV subsidies may soften the financial concerns associ- • Charging at 0 V. Some carmakers may be interested ated with this issue, and in some cases (especially for meter in 440-V charging to reduce charging times (Carney, 2009). upgrades), utilities may pay for such upgrades and amortize The cost and potential extent of such service needs study. the costs over a series of electric bills. However, an open • Distribution system upgrades. In some areas, local question remains: To what extent will these additional costs, utility electric distribution capacity may not be adequate for or just the inconvenience of making the modifications, dis- the simultaneous charging of many PHEVs on one circuit, suade potential PHEV buyers? particularly for fast charges. These areas should be identified and plans for upgrading developed. • Safety. Safety issues associated with charging PHEVs Public Charging must be thoroughly studied and problems minimized. As PHEVs proliferate, there will be a growing demand • Energy stored in PHEVs. It has been suggested that the for public charging, much of which could occur during day- electric grid might use the electric energy stored in PHEVs to time hours, when electric power costs are higher. It seems help meet peak demand (when the costs of producing power likely that some office complexes will install chargers for are very high) and replace it later, when costs are lower. The their employees and visitors, and shopping malls may install willingness of PHEV owners to allow this, and the benefits to chargers to attract customers. In some cases, businesses may them of doing so, need to be assessed. Conditions and terms not even charge for the electric power, treating it instead as under which this might be feasible and beneficial need to be a promotional expense. developed. Alternatively, a charged PHEV might be used to As an indication of interest in public charging, one provide electric power to a home during a blackout. It would company, Electric Transportation Engineering Corp., was be useful to know the viability of these options.