The Future of Advanced Technology Vehicles:Vehicle Types, Emissions of Combustion and Electricity Generation, and Adoption

Yixue Xiong

1. IntroductionAny energy and environmental policy must consider the perspective of transportation. In

2015, transportation sector energy consumed 27.7 Quadrillion BTU, accounting for 28.4% of total energy consumption of the United States (U.S. Energy Information Administration, 2016). Different types of energy sources are used in the transportation sector, including gasoline, diesel, jet fuel, biofuels, natural gas and electricity. Over 90 percent of the fuel used for transportation is petroleum based, which includes gasoline and diesel (U.S. EIA, 2016). It is predicted that if the current oil consumption proceeds, the oil reserved will be exhausted before the mid-century. Besides, the increased demand of energy lead to more the greenhouse gas (GHG) and pollutants caused by burning fossil fuels, such as CO, SO2 and NOx. In 2015, U.S. Environmental Protection Agency (U.S. EPA) reported that the majority greenhouse gas emission from transportation is from the petroleum-based fuels, and the largest sources are passenger cars and light-duty trucks, accounting for more than 50% from the sector.

In order to phase out these pollutants and reduce the greenhouse gas emissions associated with the transportation, decision makers are targeting a multitude of policy measures to increase adoption of light-duty electric vehicles (DOE 2015). According to the EIA, the electric vehicles that are projected to grow the fastest all use a battery pack to do part or all of the propulsion. However, the actual emission reduction benefits associated with plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEV) varies with multiple factors, such as the vehicle types, fuel types for electricity generation and refueling availability (McLaren et al. 2016).

However, the externalities including the appropriable knowledge and pollution abatement result in social and economic benefits that are not incorporated in electric vehicle prices. In order to address resulting market failures, governments have employed a number of policies (Sierzchula et. al, 2014). The consumers’ intent to purchase advanced technology vehicles can be influenced by government policies, their education levels, environmental sensitive and energy concerns (Carley et. al, 2013).

2. Different Types of Electric VehiclesWith the increasing of energy demand, automobile industries start to work on alternative fuel

vehicles (AFV), including hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), plug-in electric vehicles (PEV) and fuel cell electric vehicles (FCEV).

2.1 Conventional hybrid electric vehiclesConventional hybrid electric vehicles (HEV) are

primarily powered by an internal combustion engine (ICE), but they also have an electric motor (EM) and use liquid fuels to produce electricity onboard at low speeds (Dumortier et al. 2015). The extra power provided by the electric motor allows for a smaller engine without

Source: Alternative Fuel Data Center, U.S. DOE

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sacrificing performance; the battery also powers auxiliary systems and headlights and can reduce engine idling when the vehicle is stopped (DOE, 2014). Besides, some HEVs can drive short distances at low speeds on electrical power alone. By using both ICE and electric motors, HEVs can achieve a better fuel efficiency and less emissions than the conventional gasoline vehicles.

Since HEVs cannot plug in and it is only charged by the gasoline engine and by regenerative braking, the electric-only drive is typically at the starting up or lower speed. Regenerative braking allows some of the kinetic energy dissipated from braking be captured, turned into energy and stored in the battery.

Currently, Toyota Prius is the best-selling conventional hybrid vehicle in the United States. In 2015, the country sold 113,829 Toyota Prius in total, about 30% of total HEV sales.

2.2 Plug-in hybrid electric vehiclesPlug-in hybrid electric vehicles (PHEV) are a kind of

HEVs that could store energy from the power grid and charge the batteries. Unlike the HEVs, PHEV could also connect to the electric grid by a plug-in system. Besides, their batteries can also be charged by the ICE and through regenerative braking system. When the battery is emptied, the gasoline engine starts to work as a HEV.

Generally, PHEV has a larger battery capacity than HEV does, providing an all-electric driving range from 10 (PHEV 10) to 40-plus (PHEV 40) miles (DOE, 2014). When the battery is charged, the PHEV can drive on the electricity from the battery, especially in city road. The ICE may power the vehicle when the battery run out, during rapid acceleration, at high speeds, or when intensive heating or air conditioning is required (Dumortier et al. 2015).

Generally, PHEV has a larger battery capacity than HEV, and since the gasoline engine serves as a back-up method, the fear of running out of battery would be relieved. Besides, when the PHEV is powered by electricity, there will not have any tailpipe emissions on road. On the non-electric driving, the PHEV would be more efficient than conventional vehicles. Thus, the environmental benefits from PHEVs could be outstanding.

2.3 All electric vehiclesAll electric vehicle is also called plug-in electric

vehicles (PEV), or battery electric vehicles (BEV). It has only electric motors, which powered by battery-stored energy, and it need to be refueled by plugging into grid. Like HEV and PHEV, the PEV also has the regenerative braking system and idle-stop features, which makes it more efficient than the conventional vehicles. Although EVs do not have tailpipe emissions during driving, they do have life-cycle emission from the electricity production. The emission rate will highly rely on the local electricity grid profiles.

Source: Alternative Fuel Data Center, U.S. DOE

Source: Alternative Fuel Data Center, U.S. DOE

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Generally, PEVs have a short range per refueling than the conventional vehicles, depending on the storage capacity of their batteries. Most of PEVs have a drive range around 100 miles on fully charged batter under ideal conditions (U.S. DOE, 2016), with some could go up to more than 300 miles. Also, their range could decrease by the driving conditions and driving habits, such as moisture, temperature, speeding and heavy loads.

From 2011 to 2014, Nissan Leaf and Chevrolet Volt were the best sellers in the country. However, Tesla Model S became the best-seller in 2015, sold 26200 vehicles in total, accounting for 23% of total market share.

2.4 Fuel cell electric VehiclesFuel cell electric vehicles (FCEV) have electric

motors and powered by hydrogen gas (Dunlap, 2015). Since the FCEVs have electric drive system, it could utilize the electric storage feature to increase the efficiency. Besides, it is possible to build the FC on existing gasoline vehicle platform. FCEVs are only in the beginning phase in the U.S. market, and they could only be fueled in California and Hawaii currently (U.S. DOE, 2016). Thus, although FCEVs are very clean and more efficient, this analysis will not include much discussion about it.

3. Charging BatteriesBoth PHEVs and PEVs could be charged in electric vehicle supply equipment (EVSE),

which provides safe flow of electricity to the vehicles (U.S. DOE, 2014). There are mainly two types of EVSE, depending on the battery charging rate:

AC level 1 and level 2: providing alternating current (AC) with an on-board equipment to convert AC to direct current for the batteries.

AC level 1 provides 12 to 16 amps of amperage with 120V voltage. The power is about 1.3 to 1.9 kW and charging time around 2 to 5 miles per hour charging.

AC level 2 provides no more than 80 amps of amperage and 240V voltage. The power is about 19 kW and charging time around 10 to 20 miles per hour charging.

DC fast charging (level 2): providing electricity directly to the battery. The amperage could reach 200 amps, and the voltage can be as high as 600V at most. Since the power is 50 to 150 kW, it can provide the charging rate at 60 to 80 miles in less than 20 minutes.

Thus, charging times might range from several minutes to more than 20 hours, according the battery types and EVSE types. Since PHEVs have smaller batteries size than PEVs, it’s charging time would be much shorter than the latter ones.

Source: Alternative Fuel Data Center, U.S. DOE

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4. Emission BenefitsTypically, HEVs, PHEVs and PEVs have lower emissions rate than conventional vehicles

(U.S. DOE, 2014). HEVs and PHEVs (non-electric miles) have a higher fuel efficiency than CVs, and PEVs and PHEVs (electric miles) have no tailpipe emission. However, their life cycle emissions depending on the amount of electricity needed and the regions charged.

4.1 Electricity Grid ProfilesElectricity grids broadly represent regions with different levels of carbon intensity (McLaren

et al. 2016). By using the production cost model, the analysis would able to simulate hourly dispatch intervals in the course of a year for different grids.

Assume five electricity grid profiles to represent the carbon intensity from low to high: Low carbon grid: 100% of electricity is generated from zero-emission fuels, such as

renewables and nuclear. Med-low carbon grid: 50% of electricity is from zero-emission fuels, and natural gas

accounts for another 50%. Medium carbon grid: 25% of electricity is from renewables and 75% is from natural

gas. Med-high carbon grid: 10% comes from nuclear resource, 60% from natural gas and

30% from coal energy. High carbon grid: 100% of electricity is from coal.

The level of greenhouse gas and pollutant emissions associated with each charging scenarios is based on the carbon intensity profile of the electricity grid, the efficiencies of the vehicles and the convert ratio of electric-to-gasoline miles to drive.

By adopting the Brinkman approach (2015), the emissions for electric miles could be assigned to an emission factor in pounds CO2 per kilowatt hour (lbs CO2/kWh). For natural gas, conventional combustion turbine will have a higher emission factor than combined power and heat system. These emission factors could apply to the electricity missed for the five grid profiles (Figure 1). Then the emissions from different grids could be calculated (Figure 2).

Figure 1. Emission factors of fuel sources (lbs CO2/kwh)

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Figure 2. Emission factors of different carbon intensity grids (lbs CO2/kwh)

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The emission from non-electric miles are a function of the vehicle efficiency. According to the U.S. DOE and the Government Performance and Results Act (GPRA), an emissions factor of 19.64 lbs of CO2 per gallon gasoline combustion (EIA 2013). In 2012, Obama Administration finalized the new corporate average fuel economy (CAFE) standards for 2025 vehicle fuel economy, targeting to raise the fuel efficiency of cars to 54.5 miles per gallon gasoline (White House, 2012). However, the CAFE standard do not test by real-world driving conditions (EIA, 2016), thus the conventional vehicles (CV) should reach an average fuel efficiency of 40.8 mpg by 2025, HEV should reach 71 mpg and the PHEVs should reach 66.8 mpg (EIA, 2014). Thus, the emission from conventional vehicle is 0.48 lb CO2 per mile, the HEV is 0.26 lb CO2/mile and PHEV is 0.29 lb CO2/mile (McLaren et al. 2016).

Since the emission from electric miles are depending on the carbon intensity profile of electricity grids and the amount energy needed per year, it is important to know the efficiency of electric motors (EMs) and internal combustion engines (ICEs). This study assumes there is a parallel architecture with the ability to declutch the engine from the powertrain (Simpson, 2006). In general, the electric motor efficiency is 76.4% - 80.2%, including inverter and gear loss (Miller et. al, 20xx). The battery and charger efficiency are roughly 90% each and the overall efficiency can reach 81% (Chae et. al., 2011; Gautam et. al., 2011). The electric vehicle converts about 60% of the grid electricity to its wheels, while the ICE converts only about 20% of the gasoline energy to the wheels. Thus, the overall fuel efficiency of electric motors and battery is as three times as the ICEs. MPGe is the approach EPA adopted to convert the energy used per by EVs compare to miles per gallon in ICEs. For PEVs and PHEVs, 33.7 kWh of electricity represents the same amount of energy in one gallon of gasoline (Oge, MT and Grundler, 2012). In this case, the real-world fuel efficiency of PHEV and PEV in electric miles could achieve 122.4 MPGe in 2025.

According to the Federal Highway Administration of U.S. Department of Transportation (DOT), the average annual miles per driver by age groups and by locations are different. In general, EPA and DOT assume the average annual mileage per driver is 15,000 miles, around 41 miles per day and including 55% of city road and 45% of highway. Assume both PHEVs and PEVs are charged daily. The all-electric range (AER) of PHEVs varies from 12 miles to 53 miles

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(plugincars.com). Assume 30% of travelling distance of PHEVs are driven by electric and 70% by gasoline. Under this assumption, the traveling miles associated with different vehicles could be determined (Table 1).

Table 1. Electric miles and non-electrical miles of different vehiclesElectric Mile MPGe Energy (kWh) Non-Electric Mile MPG Gasoline (Gal)

CVs 0 0 0 15,000 40.8 367.65HEVs 0 0 0 15,000 71 211.27PHEVs 4,500 122.4 1238.97 10,500 66.8 157.19PEVs 15,000 122.4 4129.90 0 0 0

Thus, the total CO2 emission associated with four different vehicle types from five different grid scenarios are shown in below (Figure 3).

Figure 3. Annual CO2 emission (lb) associated with different vehicle types in different electricity grid carbon intensity profiles.

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According to Figure 3, the CVs and HEVs are the constant CO2 emission rate of 7200 lbs/year and 3900 lbs/year, respectively. The environmental benefits mainly depend on the CO2 emission associated with electricity production in different scenarios.

In the low carbon scenario, PEVs are the most environment-friendly vehicles, with no emissions at all. Then the PHEVs are the second cleanest, with an emission rate of 3045 pounds CO2 per year. In the med-low and medium scenarios, this trend continues, and PEV is still the cleanest while CV is the dirtiest. In the medium scenario, the emission from both PHEV and PEV increase, and the emission from PHEV is even slightly over HEV. In the med-high scenario, the emission from PEV and PHEV are exceeding the emission from HEV. At this time, CV associated emission still rank the first. In the high scenario, the PEVs can cause heavy pollution, emitting over 9,000 pounds of CP2 per year, even greater than CV.

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Let the emission associated with CV and PEV, equivalent of 7200 pounds CO2 per year, the grid carbon profile has to be lower than 1.74 pounds CO2 per kWh in order to introduce the environmental benefits from PEVs.

Basically, the environmental benefits from using electric engines to replace the gasolines are determined by the electricity profile in the country. Currently, there has no national-wide policy to cap the emission from electricity generation. According to EPA (2012), the annual GHG emission output rate varies through different sub regions (Figure 4).

Figure 4. Annual GHG emission from electricity grid by regions.a. Map of eGRID subregions

b. eGrid region emission rate with five carbon intensity profiles

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From the graph above, currently no region within the U.S. are adopting low carbon electricity grid. Only NYUP and AKMS achieve low to med-low scenario. From NEWE to NYCW are between med-low and medium carbon intensity grid; from RFCE to AKGD are between medium and med-high; and from SRTV to RMPA are from med-high to high carbon scenario. Thus, almost all regions in the United States would be benefit from adopting advanced technology vehicles. Particularly, the RMPA region has the highest CO2 emission rate of 1.823 lb/kWh and it might have not much benefit from adopting PEVs, and the HEV and PHEV would be its best choice.

In a word, in the regions use low emission electricity, PHEVs and EVS have the advantage in less emission over the CVs and HEVs, especially for those who would mainly drive in city road and commute. In regions that rely heavily on fossil fuels, the PHEVs and PEVs would not have strong emission benefits from it.

5. Cost of advanced technology vehicles5.1 Fuel costs of CVs, HEVs, PHEVs and PEVs

The sale price of PHEVs and PEVs are higher than CVs and HEVs, as discussed above. In the Energy Outlook 2016 (EIA), an average electric gasoline vehicle Assume the sale price of an average sedan ICE vehicle, such as Toyota Camry, is $ 24,000; the sale price of a typical HEV is $25,000; the price of a PHEV is $35,000 (PHEV 20); and for PEV is $33,000 (Electric 100).

According to EIA (2016), the overall electricity price of all sectors in the United States is $ 0.1069/kWh, with $0.1287/kWh in residential sector and $0.0983/kWh in transportation sector. This study assumes the cost of grid electricity associated with EVs is $0.11/kWh. Since January 2015, the average cost of gasoline is $2.2/gallon (EIA, 2016).

Table 2. Annual fuel costs of different vehiclesVehicle Type Sale price ($) Gasoline ($) Electricity ($) Annual Fuel Cost ($)CVs 24000 808.83 0 808.83HEVs 25000 464.79 0 464.79PHEVs 34000 345.82 136.29 482.11PEVs 33000 0 454.29 454.29

Note: Operational and maintenance costs are not included.

In this case, PEVs owners will cost the least on fuel, about $454.29 per year, followed by HEVs of $464.79 and PHEVs of $482.11 per year. The annual fuel cost differences among those three types of vehicles are relatively small, and with discounting rate over time, the differences could be even smaller. The CVs owners will spend more on gasoline each year, reaching 808.83 per year. Thus, driving a HEV can save fuel cost by $344 per year, a PHEV can save fuel cost by $326.72, and a PEV can save $354.54. Either one of the advanced technology vehicles has a lower fuel cost than a similar CV.

5.2 Life cycle costs comparison for CVs, HEVs, PHEVs and PEVsUnder the CAFE standards, the most significant incentive is a federal income tax credit of up

to $7500 for the purchase of a qualified plug-in electric vehicle. In some states, additional monetary incentives such as sales tax exemptions and lower licensing fees are in place as well as

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non-monetary incentives including access to high occupancy vehicle (HOV) lanes or exemption from public parking meters. The policy measures that are of interest to this analysis are related to the fuel economy labels on new cars (Carley et. al, 2013).

Currently, most PEVs received the full tax credit of $7500. For PHEVs, the tax credit varies from $2500 to $7500, this study will assume all the PHEVs owners can receive $5000 federal tax credit. Assume a vehicle has a lifetime of 15 years in average. The vehicle owners would pay the full price and receive the tax credit at the very beginning year and make fuel payment in the end of a year. By using a 3% and 7% discount rate, the lifetime costs of those four types of vehicles are shown in figure 5.

Figure 5. Overall costs for CVs, HEVs, PHEVs and PEVs in 15 years, maintenance not included.

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(A) Sale price and fuel costs with 3% discount rate(B) Sale price, fuel costs and tax credit for PHEVs and PEVs with 3% discount rate(C) Sale price and fuel costs with 7% discount rate(D) Sale price, fuel costs and tax credit for PHEVs and PEVs with 7% discount rate

From A and C shown above, the lifetime cost of PHEVs and PEVs will be well above the CVs and HEVs. Under both 3% and 7% discount rate scenario, the cost of HEV will equals to

A B

C D

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that of CVs in the fourth year. After that, the fuel cost from CVs will make the total cost greater than HEVs. And for the PHEVs and PEVs, the total cost is mainly due to the battery cost in the beginning, the total costs will still be $7000 greater than those pure gasoline cars.

From B and D, the government tax credit reduced the sale price in the beginning. The PEVs, which received the highest tax credit, will have the similar price as the HEVs. It turns out that PEVs and HEVs would have a very close overall cost during their lifetimes. However, since the highest upfront cost and less tax credit, the cost of PHEVs is well above the other threes. But when take fuel costs into consideration, the total costs in the year 15 would be similar between PHEVs and CVs under 3% scenario. In the 7% scenario, the difference will still be about $2000.

5.3 Consumer AdoptionAccording to Dumortier et. al (2015), all the advanced technology vehicles are having a

difficult time penetrating into vehicle market. In the short term, the market will still be dominated by conventional vehicles (Singer et. al, 2016). Their research concluded that the fuel savings in vehicles’ life cycle have no effect on consumer’s ranking of CVs, HEVs, PHEVs and PEVs.

The advanced technologies vehicles have a higher initial price due to the technologies associated with battery and efficiencies. Although they would have less fuel costs and environmental benefits, the consumer typically will not recognize it and decline to purchase those vehicles. This is called “energy-efficiency paradox” or the “energy-efficiency gap” (Gillingham and Palmer, 2013). Research suggests that fuel economy, government incentives, environmental concerns, and general interest in technological innovations are influential in driving vehicle purchasing decisions (Caulfield et al., 2010).

6. ConclusionThis study introduced the advanced technology vehicles, including the with different vehicles

types, the charging situation and the consideration of their emissions and costs based on the anticipated 2025 vehicle efficiencies.

The suggestions of the study will include: The carbon intensity of the electricity grids has the greatest influence on the emission

benefit from those vehicles with all electric mile. The differences in emissions between carbon intensity profiles are detectable according to the calculation. Based on the analysis, the emission benefit will stop by the grid profile at 1.74 pounds CO2 per kWh generation.

In the regions use low emission electricity, PHEVs and PEVs have the advantage in less emission over the CVs and HEVs, especially for those who would mainly drive in city road and commute. In regions that rely heavily on fossil fuels, the PHEVs and PEVs would not have strong emission benefits from it.

The annual fuel costs of HEVs, PHEVs and PEVs are much lower than conventional vehicles. However, the advanced technology with battery and efficiency will add a higher initial price for those three vehicles. Without government incentives, the total costs of PHEVs and PEVs will be outstanding higher than HEVs and CVs. However,

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if take the government incentives into consideration, the total costs of PHEVs and PEVs might be able to compete with ICE vehicles.

The consumers tend to choose the lower initial price and convenient charged vehicles instead of considering the long-term pollution and climate impacts. Even though with the government incentives, there are still several barriers from those advanced technology vehicles. Obstacles to the widespread adoption of plug-in electric vehicles are the limited range, the long charging time, the limited availability of recharging stations, and the higher purchase price compared to similar conventional gasoline vehicles.

The actual environment benefits may vary due to different regions, different charging time and charging placed. The gasoline price and electricity price also effects on the adoption of those advanced technology vehicles.

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