Integrating EVs and PHEVs into the electric grid longterm projections of electricity demand and CO2 emissions

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^^r Lew Fulton and Tali Trigg, Energy Technology Policy Division

Worldwide CO2-emissions constraints could stimulate the rapid development of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs) as a much cleaner means of transportation than standard vehicles. This paper provides new findings on this topic based on IEA projections for the year 2050. Questions covered include how much grid-electricity demand the use of PHEVs would create globally and by region, and how PHEV battery electric range affects the percentage of driving on electricity and net CO2-emission reductions. Although PHEVs, along with EVs, would increase global electricity demand by 2050, the net reduction in CO2 emissions is clearly positive, owing to \43 vehicle efficiency and avoided gasoline/diesel use.

Electricity in vehicles and climate policy goals

In the IEA BLUE Map scenario, the IEA anticipates great numbers of electric and plug-in hybrid vehicles in use around the world by 2050 (IEA, 2010). This is part of a broader scenario to achieve very low carbon dioxide (CO 2) emissions from transport through improvements in efficiency, alternative fuel use, and changes in travel patterns. Following the BLUE Map scenario, CO2 emissions from transport by the year 2050 are anticipated to be 5.4 gigatonnes (Gt) of CO2 lower than if a business-as-usual, or Baseline, scenario is followed. Both pure-electric vehicle (EV) and plug-in hybrid electric vehicle (PHEV) technologies greatly improve efficiency and shift energy demand from petroleum fuels to electricity provided by the grid. The manner in which EVs and PHEVs eventually source electricity from the grid must be better analysed to determine the true CO2 emissions impact and technological considerations for climate policy.

This paper summarises the results of the Energy Technology Perspectives 2010 EV/PHEV projections and impacts on electricity use. It extends the ETP analysis using a new tool, the "electric and plug-in electric vehicle module" of the IEA Mobility Model (MoMo) (see text box on following page) and addresses a number of questions accompanying the electrification of the light-duty transportation sector:

► In the BLUE Map scenario (high PHEV adoption), how much grid electricity demand do PHEVs create over time and in different regions of the world? How does this translate into reductions of CO2 emissions as a function of the electricity-generating profiles of different regions?

► For PHEVs, how does the configuration (e.g. the battery's electric range) affect the percentage of driving on electricity, and in turn, the vehicle's electricity demand and CO2 emissions?

The basics of electric vehicles in climate change mitigation

In 2005, transport accounted for 23% of global energy-related CO2 emissions (IEA, 2010). It now accounts for more than half the oil used worldwide and nearly 25% of energy-related CO2 emissions. Petroleum continues to account for about 97% of transport energy use. In order to change, future transport developments must follow a radically different route: this means new types of vehicles and fuels, used in new ways. The IEA BLUE Map scenario envisions a completely different set of propulsion systems and fuel-use patterns in place by 2050. The light-duty vehicle technologies in the BLUE Map scenario include gasoline and diesel hybrids, electric and plug-in hybrid electric vehicles, and fuel-cell vehicles (after 2020). These vehicles account for nearly 100% of sales by 2050, with electric and plug-in hybrid vehicles accounting for more than half. Even by 2020, the BLUE Map includes around 6 million sales per year of EVs and PHEVs; this figure rises to over 100 million per year by 2050.

EVs have only battery-powered motor propulsion, whereas PHEVs are essentially hybrid vehicles containing both an internal combustion engine and electric motor system, with an enlarged battery pack that can be plugged in to recharge. The EV models being introduced today typically have a range of 100-150 kilometres, whereas PHEVs have an electric range of 20-50 kilometres. PHEVs also have the advantage of a liquid-fuel engine capable of long-range travel between refuellings.

A key issue is the impact of the electric travel possible with PHEVs. Since the electric range is short, it may only provide a small share of daily travel, with the liquid-fuel engine providing the rest. The results of a previous study for the United States show that a fairly low-range PHEV (e.g. with a range of 32 km or 20 miles) can shift a surprisingly large share of travel to electric - up to 65% of the annual driving distance (Weiller, 2011).

The EV/PHEV Module is a new component of the IEA Mobility Model (MoMo), created in order to explore the electricity demand of different EV/PHEV scenarios and assumptions, and the CO2 impacts associated with electrification of LDVs and particular levels of resulting electricity demand. Like the rest of MoMo, the module separates the world into 22 countries and regions. It allows projections of vehicle sales, stocks, travel and energy use to 2050.

Figure 1

Vehicle sales shares under the BLUE Map scenario


44 This percentage will depend on the average daily driving distance and the daily variation in this distance. In any case, a PHEV can provide "base-load" driving on electricity and significantly reduce liquid fuel use.

Electric and plug-in hybrid electric vehicles recharging from the grid will instigate increased power generation. Depending on the success of these vehicle types to penetrate the Light-Duty Vehicle (LDV) market, additional generation capacity may be required in the long term. The electricity sector relies on a mix of fuels that may vary each day, as demand peaks at times of high activity, and in the long term as power plants are installed and retired. The time of day at which EVs and PHEVs recharge will have an impact on total CO2 emissions from these vehicles. This paper presents total emissions from vehicle-charging in a number of scenarios based on the following comparisons:

F Short-range PHEVs versus longer-range PHEVs' dominance of the market (full-EVs do not change in either case, but further work will concentrate on PHEV-EV interdependence).

F Baseline versus BLUE Map electricity-mix evolution.

Vehicle shares under a long-term CO2-emissions constraint

In the ETP projections new EV and PHEV models are introduced to the mass market beginning in 2010. From 2015 to 2020, sales per model and the number of existing models increase fairly rapidly as companies move toward full commercialisation, reaching about 7% of all new LDV sales in 2020, 20% by 2030 and over 50% by 2050 (Figure 1).

This fleet is a mix of pure electric vehicles and plug-in hybrid vehicles. PHEVs are further subdivided by electric-driving ranges, with a mix of vehicles able to drive between 20 kilometres and 120 kilometres (PHEV-20 and PHEV-120, respectively). Thirty- and 60-km-range PHEVs (PHEV-30 and PHEV-60) are expected to be the most common intermediate-range standards available on the market. With total plug-in vehicle sales taken from the ETP2010 BLUE Map, we explore two scenarios with different shares of PHEV types in the fleet.

Figure 1

Vehicle sales shares under the BLUE Map scenario


Gasoline ICE Diesel hybrid Hydrogen hybrid

Diesel LPG/CNG Electric vehicles

Gasoline hybrid Fuel cell vehicles

Gasoline ICE Diesel hybrid Hydrogen hybrid

Diesel LPG/CNG Electric vehicles

Gasoline hybrid Fuel cell vehicles

Source: IEA 2010.

Under scenario A, low-range PHEVs are most successful (Figure 2). In this scenario, 20- and 30-km PHEVs are the only PHEVs sold on the market. This could result from EVs having become particularly economical private vehicles and having taken the market share from longer-range PHEVs. PHEVs in this case are mainly a relatively low-cost electrification option for people who: a) have relatively short daily driving ranges and thus benefit even from the short electric range of PHEVs; and/or b) want some electric range but also plenty of liquid-fuel range for long trips. Such vehicles will enable drivers to reduce gasoline consumption and increase their vehicle efficiency without committing to the all-electric vehicle.

Under Scenario B, high-range PHEVs are most successful. This scenario supposes that PHEVs with higher range gain prevalence over low-range PHEVs (those with battery life of 20-30 km). PHEV-120s quickly dominate the market, reaching 70% of sales by 2050, due to their dual advantage of a high share of travel on electricity and reliable unlimited driving range on liquid fuel when the battery is discharged.

The critical role of vehicle driving range

PHEVs' electricity consumption depends on battery size and driving range. The share of distance travelled on grid-provided electricity relative to the total distance travelled, which we call the "utility factor", is used for the evaluation of PHEVs' electricity demand. We obtain the utility factor measures from an analysis of driving statistics from an American travel survey (Weiller, 2011).

Figure 2

Low-range (scenario A) and high-range (scenario B) PHEV scenarios

Shares of PHEV types in fleet


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