Electric vs Diesel cars

Electric vs Diesel Cars: A Comparison

Moustafa Akkad
Francis Coburn
Samuel Doiron
Nicolas Puello

Sheridan College

November 13, 2014

Table of Contents
Executive Summary	2
Introduction	3
1 - Engine Efficiency and the Environment	3
1.1 - Biofuels	4
Figure 1	5
1.2 - Health Effects	5
2 - Technical aspects	6
2.1 - Working principles	6
2.2 - Efficiency losses	6
2.3 - Overall efficiency	7
3 - Electric Car Features	8
3.1 - Long distance driving capabilities	8
3.2 - Maintenance	9
3.3 - Pollution	9
3.4 - Sound	9
4. Feasibility	11
4.1 Location and Infrastructure	11
4.2 Weather	12
4.3 Driving Style	13
Recommendation	14
References	16


Executive Summary
This report is targeted at any prospective buyer of a diesel or electric car. Inside is a comprehensive comparison of the environmental impact from the actual running of the vehicle to the sources of energy. Biodiesel is mentioned along with the differences in environmental impact compared to regular diesel vehicles. The base technical aspects of both diesels and electrics is discussed along with their working principles, where they gain their efficiencies and the overall difference in energy efficiency between the two technologies. The different features are then compared including the long distance driving capabilities, maintenance requirements, and pollution generated by each type. Lastly, the feasibility of each is compared in relation to the owners location, weather, and driving style.
Introduction
A car is one of the most important purchases a consumer can make. And as countries worldwide seek to address future energy requirements, consumers not only have to seek sustainable transportation for one’s personal needs but for the environment at large. The diesel car and the electric car represent two of the most promising choices a consumer can make.
This report distinguishes the important factors of both the diesel and electric car that influence the buying decision of a consumer.

These factors include:
•	Environmental impact
•	Energy Efficiency and implementation
•	Pricing and features
•	Feasibility

The aim of this report is to present sufficient information on these important factors so that the average consumer can make a proper decision that caters to their specific needs.
1 - Engine Efficiency and the Environment
When it comes to making an environmentally friendly choice, efficiency is important. Even if you have an electric car system that is totally emission free, it still has to be efficient. Otherwise, it may be a better choice to use a less environmentally friendly method that is more efficient. An electric car still has a substantial carbon footprint, even though it may not emit any tailpipe emissions. (Girard, 2011) Likewise, although diesel fuel is not environmentally friendly, it is very widely used. Electric cars are certainly a step in the right direction when it comes to emissions. However, there are other costs such as extra electricity consumption. In the United States only 10% of electricity is produced via renewable means. (Girard, 2011) So a mass drain on the power grid may actually cause more fossil fuels to be burned, as opposed to less.
Since cars need to be portable, we also have to deal with the issue of energy storage. When you fill up the fuel tank of a car with gasoline, it’s assumed that if the car is left for a week the fuel will still be there. Not so with an electric car, as batteries will discharge slowly even when not in use. Batteries also store less energy for their weight as compared to petroleum based fuels. However, electric motors more efficiently transfer stored energy into movement, so less energy is needed in the first place. Battery technology can also be expected to improve as the infrastructure around electric cars begins to be built up. A final environmental issue surrounding batteries is that they must be disposed of properly, or else the heavy metals and acids they contain will contaminate the environment.
1.1 - Biofuels
By using biofuels, such as palm oil and ethanol, it is possible to reduce emissions while maintaining the current infrastructure of diesel engines. However, it is also true that even a complete switch to biofuel will not greatly reduce overall emissions to an extent that matters in terms of global climate change. The biofuel movement is more about making the best of an existing infrastructure of diesel engines, and switching to a renewable source vs. a non-renewable one. A fleet of bio diesel trucks will still emit compounds harmful to our health. As one can see in Figure 1, Canada is behind the world in terms of actual use of biofuels.
Figure 1
  (Biofuel Support Policies: An Economic Assessment, 2014)
Biofuels seem like an ideal solution, aside from some practical considerations. One is that engines require modifications to run biodiesel, or simply cannot run the fuel period. This adds to the cost of using this fuel, and decreases economic feasibility. Even when engines can use biodiesel, they can often only use a percentage of it, with the remainder being regular diesel. All of the negative health effects of diesel fuel are still present in biodiesel, just in a smaller percentage. The interoperability of biodiesel and regular diesel may also extend the dominance of the fossil fuel infrastructure, causing more environmental problems than it is solving.
1.2 - Health Effects
One of the main concerns with diesel engines is with regards to the content of emissions. Although emissions standards are constantly improving, diesel exhaust has been found to be a group 1 carcinogen by the IARC. (IARC, 2014) This is due to hydrocarbons, nitrous oxide, and aldehyde that are present in diesel exhaust. (Bang-Quan, Shi-Jin, Jian-Xin, & Hong, 2003) The only ways in which an electric car may harm human health are the ways in which electric power may be generated. If the electricity is generated by coal, natural gas, or other fossil fuels, although the car is not itself emitting emissions they are being generated somewhere else. For electric cars to be a truly environmentally friendly option, the electricity used must be generated in a clean fashion.
2 - Technical aspects
2.1 - Working principles
In any internal combustion engine including diesels, fuel is combined with air as close to possible to an optimal ratio of 14.5 parts of air for 1 part of diesel. The engine cylinders then compress this optimal mix of fuel and air to prepare it for combustion. Unlike gasoline engines which have compression ratios close to 10:1, a diesel engine requires a much higher ratio often going as high as 20:1. At peak compression, the air and fuel mix is ignited to produce a powerful and very fast explosion. This explosion is what gives an engine its power. Gasoline explosions are much quicker than diesels but are have less force to them. This is why diesel engines run at lower speeds but have more torque. In the last stage of an engine running, the burnt up mix of fuel and air is pushed out to the exhaust where it is taken away from the other car components that are prone to damage under high temperature. In an electric vehicle, electricity is stored in a battery or series of batteries. Under acceleration, electricity flows from the batteries to the motor where the flow creates a magnetic field, which then turns an axle. \
2.2 - Efficiency losses
The largest difference in efficiency from these two types of engines come from their motors. In any combustion engine, a majority of the stored energy is lost as heat during combustion and the friction of pistons moving inside cylinders.  Vibrations, the effects of compression and inefficiencies of unburned fuel also add up to the inefficiencies of internal combustion engines. Electric motors do not suffer from such losses, as they do not require the burning of fuels to move. Their losses come mainly from the electrical resistance of the inverter and magnetic coils. Frictional losses are still present but nowhere near as significant as those found in internal combustion engines. In both cases, cars will also experience losses from other sources. Tire rolling resistance, air resistance and even parasitic losses from steering and brake pumps, and braking affect all cars. (Bandivadekar, et al., 2008)  These effects can be reduced but never eliminated; However because of the difference between the 2 types of car, electrics are more prone to losses from external sources otherwise known as power to wheels losses (Office of Transportation & Air Quality U.S. Environmental Protection Agency, 2014 ).
2.3 - Overall efficiency
This efficiency rating is the overall combination of efficiency in motor, drivetrain, aerodynamics, mechanics and driving characteristics that the owner must ultimately face. Because of the differences in mechanical principles driving the two types of cars, Electric vehicles are far more efficient. Where a gasoline engine might reach a peak efficiency of around 15% and a diesel around 20%, an electric vehicle can easily reach efficiency levels of around 80% (Shah, 2009). This massive difference is what helps to make electric vehicles extremely clean for the environment and economic to run despite their high initial costs.
3 - Electric Car Features
If the goal is to go far distances then the trend is to lean towards a diesel engine. With more super charging stations being installed over the coming years the electric car will become more of a viable option.
“Tesla Superchargers allow Model S owners to travel for free between cities along well-
traveled highways in North America, Europe and Asia. Superchargers provide half a charge in as
 little as 20 minutes and are strategically placed to allow owners to drive from station to station
 with minimal stops.” (Tesla Motors Inc, 2013)
3.1 - Long distance driving capabilities
 	There will be more options available for long distance driving and road trips. Diesel engines are the preferred type of engine for long distance driving due to efficiency. A disadvantage of diesel over electric apart from long distance travel would be the fact that diesel engines produce much more torque than horsepower which is not ideal for a consumer car.
“Diesel engines, because of the weight and compression ratio, tend to have lower
maximum RPM ranges than gasoline engines. This makes diesel engines high torque rather than
 high horsepower, and that tends to make diesel cars slow in terms of acceleration.”
 (Howstuffoworks Inc, 2000)
3.2 - Maintenance
Maintenance of a diesel engine would be much more than an electric engine over the course of its life. The cost of driving a diesel engine car constantly and for long distances causes wear and tear on the engine.
“Diesels still need regular maintenance to keep them running. The oil, air and fuel filters must be changed. Cleaner diesel fuels no longer require you to bleed excess water
 out of the system, but many vehicles still have water separators that need to be emptied
manually.” (Sclar, 2012)
3.3 - Pollution
One of the main features and draws of an electric car is there is a lack of polluting by products because the car is powered by a battery. This also goes hand in hand with reduced fuel costs electricity is significantly less expensive than gasoline.
“Another important advantage of battery-powered motors over gas-powered engines is the lower cost of the fuel - that is, electricity for EVs and gas for the internal combustion engines.” (Lampton, 2008)
3.4 - Sound
Sound is a large issue for electric cars, some people enjoy the silence that a typical electric car will make. There are people who want to add artificial sounds to electric cars to make it easier to hear for safety reasons. The visually impaired and those who rely on combustion engine sounds to navigate through cities have issues with the current state of electric cars, diesel cars would not have this problem.
	“Visually impaired pedestrians and other road occupants such as bicyclists, however, rely on the sound of combustion engines to negotiate safely” (Blind Canadians, 2010)
The answer to this issue is installing automatic pedestrian alert system to all new electric cars. Pedestrians will be able to predict incoming cars that otherwise may have gone unnoticed which will lead to less pedestrian crashes.

This graph shows the projected increase of installed super-charging stations worldwide over the next six years. This also shows that the market for electric cars is constantly growing.
One day electric cars may replace diesel cars all together.
(Young, 2013)
4. Feasibility
Feasibility is an important aspect when evaluating the choice between purchasing a diesel or electric car. In order to make a determination for one’s needs, one must look at the many factors that make diesel and electric cars suitable or unsuitable purchases.
4.1 Location and Infrastructure
One factor to consider is a person’s location. Whether diesel or electric, the infrastructure in which you drive your car plays an important role in its feasibility. For the electric car, when it comes to infrastructure, it’s a matter of both cost and convenience. For example, high electricity prices in Hawaii reduces the value of owning an electric vehicle, whereas a high diesel priced location such as California reduces the value of owning a diesel vehicle. Location also plays a role from a convenience standpoint, where you have to make you sure you are surrounded by charging stations in case you need to charge the battery. And even if that’s not an issue, you will still have to make sure you’ve given the car enough time to fill the car.
With respect to diesel cars, location matters only from a cost perspective and not much from a convenience one. Since countries all over the world are attempting to clean the air, one potential approach to doing so is penalizing those who own diesel cars in the form of tax burdens For example in the United States alone, the federal tax on diesel fuel is 32 percent more than the federal gasoline tax: 24.4 cents a gallon for diesel versus 18.4 cents for gasoline (Totty, 2012). Another case is in central London, where diesel car drivers could be forced to pay a tax to drive in to the capital's low emission zone by the year 2020 to encourage a move to cleaner cars (Knapman, 2014).
4.2 Weather
When choosing between diesel and electric, it might come down to which is more feasible in extreme weather conditions. For the electric car, mileage becomes a concern in cold weather. This is namely because you will more than likely be using a sizeable amount of energy for your heater. Also from a chemical standpoint, batteries do a poorer job of regenerating in cold weather, which makes the electric car at risk of possible failures. Figure 4.1 and 4.2 shows a link between temperature and range, comparing best and average range data sets of two electric cars, the Chevrolet Volt and the Nissan Leaf (Howard, 2013).

Figure 4.1

Figure 4.2
Diesel cars do not fair too well in cold weather either. As with batteries, fluids such as diesel also act differently from a chemical standpoint.  When the temperature is low, diesel's viscosity increases, which is known as "gelling" or "waxing", to a point where it cannot be pumped (Ingram, 2013). This causes the engine to die or not start at all.
4.3 Driving Style
Another factor to contemplate is a driver’s style of commute. Electric vehicles are excellent for short distanced stop-and-go style driving. However, for long distance travelling, the electric vehicle is a lot less reliable than the diesel car due to the risk of the car’s battery draining out. Diesel engines do not have such problems, as diesel cars are actually at their most efficient for long constant highway use. In a stop-and-go environment, diesel engines are inefficient due to powering the car from zero to cruising speed. It is actually recommended by manufacturers to drive a diesel car long distances as it helps avoid clogging the filter (Cooke, 2014).
If a commuter’s daily activity has a tendency to fluctuate up and down, one might consider looking at their average daily usage to make their choice. It has been reported that the average work trip length increases with metro population size, with a national average of 12 miles (Transportation Research Board, 2006). So the best bet in a situation like this would be to select the car based on which two factors the user values most: cost or convenience. If cost plays a more important role, the best bet would be to lean towards an electric car, as money would be saved from not going to the pump. If convenience is more valuable, the choice would be to go with a diesel-fueled car, as the daily commute would not include dealing with things like the car’s electric range or worrying about searching for the nearest charging station.
The differences in technology, design and implementation of diesel and electric cars cause them to have very different energy efficiencies. High energy efficiency is highly important as it dictates how much energy is converted to the desired output and ultimately translates to reduced operating costs for the owner.
One of the largest aspects of a cars energy efficiency is its motor. The motor is the mechanism that converts the stored energy be it in the form of gasoline or diesel fuel or the form of electricity stored in a battery.
Recommendation
Considering the research on efficiency, environmental impact, features, and feasibility, the recommended car is purely based on the potential buyers budget.  Electric cars are still a new technology and as such do not have the variety and adequate pricing to be considered a very reasonable alternative. Fortunately, with a large budget, the Tesla Model S becomes available and with its impressive features and already implemented infrastructure, is a solid contender at being a great car for most buyers. With a smaller budget, the already tried and tested technology of diesels becomes the recommended option.

References
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