Tamil News Update: Electric Mobility: Introduction of EV to Mechanical Engineers

சனி, 10 ஜூலை, 2021

Electric Mobility: Introduction of EV to Mechanical Engineers | Chapter 5

Thus spoke Murugan, the EV Guru.

Professor Murugan’s career had started from the same place as Bharath, quite literally. Both of them were classmates during their college days. They spent many long nights on the hostel terrace aiming for the stars and talking about where they see themselves in the automotive industry in their career. Their paths diverged slightly when Bharath decided to go to the U.S.A. for his post-graduation and Ph.D. while Murugan stayed in India.

Prof. Murugan’s perspective of the education sector, particularly in engineering was quite unique. He did not believe in rote learning or learning for the sake of it, for a degree or a certificate. He believed that the education sector should be considered as an extended arm of the industry. After his Ph.D., he decided to join the industry to get his hands dirty, understand how different it is from the academic world and learn the tricks of the trade. He encouraged students to visit the factory and was happy to volunteer to take them for a factory tour or give an overview of the industry.

The special interest of Prof. Murugan in facilitating factory visits for students lies in his unique outlook to learning. He believes, learning today is not limited only to formal classroom sessions we attend, whether in an university or in a corporate setup. Every opportunity we get to interact with the outside world is an opportunity to learn – interaction with colleagues, academicians, subject matter experts, watching or any interaction with a system such as a machine. The World Economic Forum (WEF) calls it “Intentional Learning”.

According to WEF, the most important skill to learn today is intentional learning. It is the practice of treating every experience as an opportunity to learn: conversations, meetings, or deliverables. Rather than being something that occurs separately, the desire to learn should be an always-on, an instinctive approach to everyday situations. Two things set intentional learners apart from everyone else: a growth mindset and a curious mindset. People with a growth mindset believe their capabilities and even intelligence can be nurtured, expanded, and changed over time. Curiosity is the starting point of everyone’s learning, right back to infancy. Cultivating curiosity can mean overcoming the fear of asking questions or of trying new things, according to WEF [1].

Prof. Murugan himself is an intentional learner. He listens to several podcasts, attends seminars, organizes panel discussions and listens to experts from various domains. In one such podcast, he liked a question which Deborah Spar, senior associate Dean in Harvard Business School posed – “It makes no sense that people should get all of their education in their 20s because if we live until our 80’s there should be many points in time when one could come back and get re-educated”[1]. Several business schools globally started adapting their MBA curriculum to address the point that Deborah Spar raised. There is typically one year of course work, where the students can stay in campus. Then they get back to their work. Every year, for a specific period like a week, they come back to their alma mater either physically or virtually, to attend classes on a contemporary topic that will help them in their in their current role. Such a practice encourages lifelong learning and is required in engineering too. With the exponential rate at which technology is evolving, it is important for engineering schools to offer lifelong learning opportunities to their students. Georgia Institute of Technology, one of the leaders in engineering education, has unveiled a roadmap for the future of higher education [2]. Having demonstrated to the world that high-quality STEM education can be accessible at low cost to learners worldwide, with the launch of the online master’s degrees in computer science and in analytics, Georgia Tech is no stranger to innovation. Examples of their innovative offerings include

Micro-credentials - offering flexible modules rather than the traditional three-credit-hour classes, credits to recognize competencies and skills, a decentralized transcript to enable students to combine evidence of learning and achievements into credentials relevant to potential employers, and micro-credentials.
Whole-Person Education - The twenty-first century workplace needs more than strong technical skills from their employees. To succeed in the future, we will need deep disciplinary skills coupled with problem-solving, communications, leadership, and intrapersonal skills, along with adaptability, creativity, and discipline. The three important sets of skills that constitute whole-person education are (i) Cognitive Skills - problem solving, creativity, critical thinking (ii) Interpersonal Skills - communications, teamwork, leadership and (iii) Intrapersonal skills - adaptability, initiative, discipline, ethics, persistence.

The basic mechanical engineering skills for designing an EV

FISITA, the international federation global automotive mobility, has defined three levels of skill sets required for the automotive engineer of tomorrow, which was covered in the first article in this series. In FISITA’s model, building Engineering Expertise is the ground level, broken down into mechanical, electrical, electronics and computer engineering. The next two levels are Integration Expertise and a Growth Mindset.

Among the basic Engineering Expertise, mechanical engineering is the very basic. It ensures that vehicles have a structure in place with necessary strength to withstand the forces it is subject to. At the same time, it cannot be too bulky and waste fuel for moving around. The design of the structure of a vehicle is an exercise of optimization based on ‘mechanics of solids’, the properties and geometry of the material used. The outer body of the vehicle should take into account aerodynamic properties, as it will move at high speed and face heavy head wind. The ‘drive’ part also belongs to mechanical engineering, from the battery which supplies power to the drive train which modulates the torque depending on different situations – a stationary vehicle moving vs a vehicle already moving at high speed.

The drive train should deliver the optimum amount of torque for the vehicle based on each situation – acceleration, deceleration, starting from a stationary position, an upward or downward gradient etc., The optimum torque will ensure efficiency of the vehicle, drawing only the least amount of power required for each situation to conserve the battery charge.

The efficiency of ICE and electric vehicles

In the second article in this series we saw that electric motors or vehicles are lot more than efficient than internal combustion engine (ICE) driven vehicles. Why is that so? Prof. Murugan took time to explain the theory behind it to Pavan and his team and refreshed their memory of what they had studied a few semesters back. ICEs are a type of heat engine in thermodynamics - the study of conversion of heat into other forms of energy. They usually follow what is called a “Carnot cycle” from thermodynamics. It has its own limits of efficiency. The energy from the petrol or diesel that is burnt inside an engine cannot be completely tapped and converted into mechanical energy. Some of the fuel will be unburnt. A significant portion of the heat is left out in the exhaust and some dissipate unused. Therefore, ICEs have low energy efficiency, typically 25%.

On the other hand, a motor converts electric energy into mechanical energy and is therefore much more efficient. An EV motor is around 85 - 90 per cent efficient when converting electrical energy into mechanical energy. “EVs convert over 77 per cent of the electrical energy from the grid to power at the wheels. Conventional gasoline vehicles only convert about 12 per cent – 30 per cent of the energy stored in gasoline to power at the wheels,” according to the US Department of Energy [3].

An all-electric vehicle (EV) does not produce emissions from the tailpipe, but there are upstream emissions (also called well-to-wheel emissions) of greenhouse gases from electricity production. For an EV to be truly a green mode of mobility, it must use energy produced by renewable sources. Authors Sanjay Prakash and Soumya Prasad have calculated a small electric car to be 2.5 time more energy efficient than a similar small petrol car [4]. They also demonstrated an electric SUV is 1.8 time more energy efficient than a similar diesel SUV.

Prof. Murugan explaining the energy efficiency of ICE Vs EV to Pavan and his friends (eBaja Team)

EV architecture

eBaja changed Pavan’s course of life. He had grown technically more confident, got a new job offer, amazing mentors in Bharath and Prof. Murugan. eBaja also introduced Pavan to Kavya. In one of his interactions with Bharath, Pavan realised the importance of attending seminars and workshops. What he could learn from his mentors, he used to share with Kavya. So, whenever possible after eBaja, both of them started attending seminars and workshops and got to meet each other. The two by then had become good friends.

Things were going smooth until Pavan received an email from Bharath with an invitation to join a pre-conference Tutorial session on EVs jointly organized by SAE and IEEE. Bharat himself was one of the speakers. Pavan was elated the moment he saw the invitation. There were multiple reasons for his happiness. First, the topics to be discussed in the Tutorial were very interesting and touches the basics of an EV. Second, Bharath was going to be one of the key speakers and he always loved listening to Bharath's way of teaching. Third, the seminar was going to be held in Andhra Pradesh and Pavan felt, Kavya should not find it difficult to join the seminar. He remembered last time Kavya mentioned that her Dean Dr. Rao expressed his dissatisfaction over Kavya low attendance while attending the remote seminars and workshops.

Pavan forwarded the invite to Kavya hoping to get a positive reply. Pavan kept on refreshing his email hoping to see a reply. And just as he lost all hopes by the end of the day, the top email in his inbox became unread. It was from Kavya. It had just two words - "Will try!". That was good enough for Pavan. But there was no communications since then till the day of the seminar.

The seminar started on time. The hall was pretty packed up within half an hour of the scheduled start. Bharath was the fourth speaker. he explained the basic structure of an EV with a simple block diagram (Figure 2). Though Pavan had built an EV prototype for eBaja, he was not an expert on EV architecture. Bharath believed in going to the basics and building the understanding from there. He went to the nearest white board and drew a simple block diagram of an EV. He started explaining the basics of EV and had a unique way of teaching the audience who were mostly beginners in the domain. For every question the audience asked, he posed a counter question. It was his way of making beginners ask the right questions and explore a new concept boldly.

A simple block diagram of a basic EV architecture

Bharath limited the discussion to the most basic components of EV:

The Battery Pack, comprising of multiple lithium ion cells, stores the energy required for running the vehicle in the form of chemical energy. A car like Tesla Model S would require 6000 – 7000 AA batteries. The battery pack is the most expensive component, accounting for 40 – 50% of the price of EV.
DC – AC Converter – The DC output of the battery is converted to AC that powers the motor.
Electric Motor converts the electrical energy into mechanical energy and delivers it to the wheels via a simple drive train.
On-board Charger converts the AC from the mains to DC and controls the current flowing into the battery pack.
Regenerative braking is a way of taking the wasted energy from the process of slowing down a car and using it to recharge the car’s batteries.

Bharath explaining EV Architecture in the Seminar

The first half of the seminar was about to finish. The anchor announced a break of half an hour for lunch. Still there was no sign of Kavya. With a heavy heart, Pavan closed his notebook and was about to proceed towards the lunch hall when his phone vibrated. The sad drooping face of Pavan immediately brightened. It was Kavya. He hit the call accept button, hold the phone close to his ear and heard a female voice saying, " hey Pavan, on your right"

Note:

All opinions and points-of-view expressed above are those of the authors and do not represent that of any other individual or organization.

References