Most Efficient Electric Car

Abstract

        The use of conventional internal combustion engines using gasoline as mean of transportation has been of the main factor of greenhouse gases emissions. These emissions are known to have catastrophic effects on Earth from rising sea levels to drastic changes in our ecosystem. The introduction of electric vehicle has been considered as one of the best solution to reduce greenhouse gases emissions in the transportation sector. A car manufacturer based in California, USA is seeking the optimal energy source to be used for the mass production of electric vehicles.

        This study proposes and evaluates four different alternatives under a set of selection criteria. The alternatives in questions are: Lead-acid Battery (LAB), Nickel Metal Hydride Battery (NiMH), Lithium-ion Battery (Li-ion) and a Hydrogen Fuel Cell (HFC). The essential criteria that needs to be met in order to further consider any alternative were the following: CO2 emissions (<500g of CO2 emitted per mile), Capital Cost (<300$/kWh) and Specific Energy (>50kWh/kg). The only two alternatives meeting the specified threshold are the Li-ion battery and the HFC. These two technologies underwent further analysis using a set of desirable criteria such as the minimal capital cost, fuel consumption, minimum refill time, maximum lifecycle and minimum maintenance costs. This comparative analysis determined the HFC as the best alternative for the mass production of an electric vehicle.

Acknowledgements

        I would like to thank my Energy Systems Professor Alejandro Rey and Professor Jan Kopyscinski for sparking my interest in renewable energy and the importance of reduction of CO2 emissions within the transportation sector.

Introduction & Background

An independent automotive company based in California, USA is planning to enter the market of electric car and approaches an engineering consulting firm with the objective of finding out what is the best energy source for an electric vehicle.

        The expectation from the consulting firm is to provide a detailed comparative analysis on the different types of battery and find the most suitable one to introduce car. In order to eliminate any questions or doubts on the subject, a quick introduction and background of context of the problem and description of specialized concepts that will first be provided. This will then be followed by a list of selection criteria that are of importance for this project. The next section will focus on describing, analyzing and comparing the different alternatives before giving our final recommendation to our client.

Since the past two decades, reducing greenhouse gases emissions has been the most important goal to achieve due to the alarming rate at the Earth is getting warmer: It is estimated that to avoid any dangerous climate change, the average global temperature should not increase more than 2°C in the next five years^[1], however we are well on our way to exceed this threshold by a big margin. This would cause catastrophic effects on Earth from rising sea levels to drastic changes to our ecosystem^[2] along with the impact it will have on the population. Hence, it is understandable that climate change has been a such an important subject over the past few years.

Greenhouse gases emissions are composed of different gases: carbon dioxide, methane, nitrous oxide and F-gases, with CO2 being responsible of 76% of all GHGs as it can be seen on the figure x^[3].

[pic 1]

Next, sources emitting greenhouse gases can vastly differ, with transportation being the second biggest sector driving the emission of CO2. (26%; Figure X^[4])

[pic 2]

In addition, research and development to reduce greenhouse gases emission with the transportation sector has been one of the most promising field over the past decades. This can be seen with the invention of the hybrid cars and more recently the electric cars.  

The purpose of this paper focuses on the study did by the consulting firm: There are many ways to produce electrics cars and the most important feature of these cars is the energy source used to have the most efficient system. Depending on the specification of the car and the alternatives proposed, choosing the right technology is crucial to have the most attractive electric car on the market.

Background

        As explained in the Introduction, research and development in this fields have long started due to the significant impact gasoline cars has on the environment. However, the real trigger for the R&D is considered to be the sales mandate issued by the California Air Resources Board (CARB)^[5] in 1990 that required big automotive company (selling more than 35,000 cars per year in California) to have at least two per cent of zero-emission vehicles (ZEVs) and partial zero emission vehicles (PZEVs) by 1998. This percentage increased to ten percent in 2003. These standards were then applied implicitly to all US states and the world.

        It is considered that the only practical way of producing ZEVs is using electric propulsion. Until now, the internal combustion engine (ICE) has been the leading propulsion system for motor vehicles, even though electric propulsion has been used for trains and smaller car applications. The most important apparatus for an efficient electric car are the propulsion motor and the battery system that will keep the car running. The former follows the industry standards and focus on using magnetic materials (usually permanent magnet called “brushless DC”) along with effective cooling method to have small but highly rated motors^[6]. In order to have an efficient operation system with a capable motor control and regenerative braking, complex electric controls and power electronics will have to be implemented.

        On the other hand, the energy source for a car or the battery is one of the most important, if not the most, aspect of an electric car. Energy sources for car vary from several battery technologies such as Nickel-Metal Hydride, Lithium-ion or lead acid batteries. Other energy sources, also refereed to unconventional batteries, take into account flywheel or fuel cells (hydrogen fuel cell) that can generate and store energy for an electric car.  

        Finally, it is important to notice that for each type of energy source or battery, a suitable charging facility needs to be available either at home or in stations throughout the city in order to have an overall sustainable product in the market. The alternatives proposed can be separated into two categories of energy sources: Electric Batteries and Fuel Cells. The mechanics of these two alternatives are described in Appendix A and B respectively.