Hybrid Vehicle: Waste Heat Recovery System Design and Analysis

This engineering capstone project details the design of a waste heat recovery system for hybrid vehicles, focusing on converting exhaust heat energy into usable electrical power via an organic Rankine cycle (ORC). The project addresses the increasing concerns about energy consumption and environmental impact in the automotive industry. It includes a comprehensive literature review of hybrid vehicle operational modes, waste heat recovery technologies, and the principles of the ORC. The study aims to improve hybrid vehicle efficiency by capturing and reusing waste heat, which is typically lost through engine exhaust and cooling systems. The design considers various components such as heat exchangers, turbines, generators, and cooling systems, aiming to solve challenges like low energy conversion efficiency and complex implementation. The ultimate goal is to integrate the system for commercial mass production, reducing energy consumption and environmental pollution. The project also includes theoretical calculations and explores potential improvements in fuel consumption through the implementation of the ORC system.

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Contents
ABSTRACT....................................................................................................................................................3
CHAPTER 1: INTRODUCTION........................................................................................................................4
1.1. Background.......................................................................................................................................4
1.2. Research Aims and Objectives..........................................................................................................6
1.3. Objectives of the Study.....................................................................................................................6
.4. Problem Statement.............................................................................................................................6
1.5. Rational of the Study........................................................................................................................7
1.6. Research Hypothesis.........................................................................................................................8
1.7. Thesis Outline...................................................................................................................................8
CHAPTER 2: LITERATURE REVIEW..............................................................................................................10
2.1. Introduction....................................................................................................................................10
2.2. Hybrid Vehicle Operational Modes.................................................................................................10
2.2.1 Theory of Operation.................................................................................................................11
2.2.1.1. Full stop................................................................................................................................11
2.2.1.2. Initial acceleration from a stop.............................................................................................11
2.2.1.3. Highway Driving....................................................................................................................11
2.2.1.4. Braking, Coasting and Deceleration......................................................................................12
2.3. Waste Heat Recovery.....................................................................................................................13
2.3.1. Regenerative & recuperative burners......................................................................................15
2.3.2. Economisers.............................................................................................................................16
2.3.3 Waste heat boilers....................................................................................................................16
2.3.4. Air preheaters..........................................................................................................................17
Benefits of Waste Heat Recovery System..............................................................................................18
Efficiency of HER & Cost Analysis...........................................................................................................19
Organic Ranking Cycle (ORC).................................................................................................................25
Principle of Operation of Organic Rankine Cycle...............................................................................26
Applications of ORC...........................................................................................................................27
Choice of Working Fluid.....................................................................................................................28
Applications of ORC in Waste Heat Recovery........................................................................................31
Heat Recovery on Industrial processes and mechanical equipment..................................................31
Heat Recovery on Internal Combustion Engine.................................................................................32

CHAPTER 3: RESEARCH METHODOLOGY...................................................................................................35
Theoretical calculations.....................................................................................................................37
CHAPTER 4: RESULTS & DISCUSSION.........................................................................................................40
CHAPTER 6: CONCLUSION.........................................................................................................................50
CHAPTER 7: REFERENCES...........................................................................................................................51

DESIGN OF WASTE HEAT RECOVERY SYSTEM FOR HYBRID VEHICLE
ABSTRACT
A device will be designed to recover vehicle exhaust heat energy and change to electric power
for the Hybrid vehicle. To achieve the above purposes, the invention is used to recover heat
energy from the exhaust gas and convert it into electrical power through the integration of the
Rankine cycle. The electricity generated by the Rankin cycle will be stored in batteries. It will
provide electrical energy to drive the vehicle or other devices on the vehicle. It includes some
accessories, such as motors, batteries, pumps, cooling systems, and heat exchangers. The project
will be designed in detail for specific exhaust pipes, including turbine design, generator
matching, and heat dissipation design and so on. This project will solve such challenges, such as
low energy conversion efficiency, difficult implementation, single-use, complex structure, large
volume and so on. Only after integration can commercial mass production is realized so as to
alleviate the rapid consumption of energy and reduce the rate of environmental pollution.

CHAPTER 1: INTRODUCTION
1.1. Background
Concerns regarding consumption of energy have remained to be on the increase in the
manufacturing industry. This has been as a result of the increase in the ecological adverse
outcomes as well as rise in the energy cost of production. Energy efficiency is one of the main
drivers of the automotive industry of today as it results in the industry delivering on
environmental as well as industrial performance. Energy efficiency has quickly shifted and
gained both national and international attention with various policies being developed both at the
regional as well as global levels aimed at curbing the worrying trend (Orr et al., 2016).
The great energy usage for operation of vehicles is significantly responsible for carbon dioxide
emissions and hence the witnessed changes in the climate. Taking into consideration that large
amount of this energy in the automotive industry is derived from fossil fuels there is fairness is
stating that carbon dioxide generated from the automotive industry also known as the automotive
industry carbon footprint have a very strong correlation with the efficiency of energy.
Nevertheless, the impact is proportional as the energy generated is consumed at the regional
levels while carbon dioxide emissions have worldwide impacts. There tends to be numerous
unnecessary use of energy in the industrial sector to the tune of between 20 per cent and 40 per
cent.
The prevailing trend of the automotive industry concentrates on maximization of the
performance of a vehicle as well as minimization of the fuel consumption alongside emissions
from the vehicle. Numerous technologies have been established dating back to the 1990s when
the global standard emissions began imposing boundaries on volumes of allowed emissions of
vehicles that led to always reducing volumes of emissions besides the consumption of fuel. Such

technologies are among them the addition of forced induction using supercharger and/or
turbocharger, using electric energy via high capacity batteries and even a combination of the two
(Kim et al., 2011).
The aim of this study is an examination of a vehicle technology that brings on board a
combination of aforementioned technologies that is termed as electric hybrid vehicle as well as
makes use of internal combustion engines using an electric power train as a component of the
propulsion architecture of vehicle, Since relatively large volume of fuel energy utilized in the
movement of any vehicle installed with internal combustion engine is often lost in the form of
heat, numerous systems have been established in exploiting the energy of the wasted heat in a
bid to provide it back to vehicle or engine in form of enhanced power or even as extra source of
electricity (Srinivasan, Mago and Krishnan, 2010). The organic Rankine cycle that is studied at
length in this study makes use of exhaust gases of engine in heating organic fluid and passing the
fluid via number of devices so as to generate electric or mechanical power that may then be used
in enhancing the different aspects of vehicle or engine performance.
The final lap of this study involves an evaluation of established hybrid model via 3 driving
cycles: New European Driving Cycle as well as two EPA federal examinations that are adopted
in the USA. The inspiration of this project is a derivative from the fact that very little research if
any has been carried out for use of organic ranking cycle waste heat recovery alongside a light
hybrid vehicle that is equipped with gasoline. The organic ranking cycle system is one of the
latest technologies that are yet to be adopted in lightweight vehicles and this is attributed not just
to the cost which is significantly high but also due to the lack of evidence offering proof that the
system may efficiently operate with engines having smaller capacity.

The study thus intends to evaluate the merits of implementation of an organic ranking cycle
waste recovery system as an aspect of the powertrain of a hybrid vehicle specially the reduction
potential of the fuel consumption (Sprouse and Depcik, 2013). For the same purpose, the
implementation of the organic ranking cycle systems would be tested through the use of two
most commonly used drive cycles to enhance the value of this assessment further hence resulting
in an increase in the utility and value.
1.2. Research Aims and Objectives
The main aim of this study is to design a waste heat recovery system for hybrid vehicle while
coming up with an implementation method of waste heat recovery system for electric hybrid
vehicles remains the major objective of the research.
1.3. Objectives of the Study
Other objectives of this study include:
 Investigating the various modes of operation of hybrid vehicles
 Conduct a literature review on organic Ranking cycle system
 Analyse the various forms of loss of energy in a vehicle and the modes of lowering the
losses
 Discussion waste heat recovery in the context of the performance of a hybrid vehicle
.4. Problem Statement
A device will be designed to recover vehicle exhaust heat energy and change to electric power
for the Hybrid vehicle. It will provide electrical energy to drive the internal combustion engine or
other devices on the car. Almost 70% of the chemical energy is wasted through engine exhaust
and cooling system. Serious and concrete efforts must be made to protect this energy through
waste heat recovery technology. Such a system would effectively cut down overall energy

requirements. Power in the cooling system is usually considered waste hence the research
focuses on the waste heat of exhaust gas, and several methods are suggested to recovery it. In
four-stroke engines, the temperature of waste gas is about 400-500 Centigrade.
Besides the consumption of fossil fuels, the combustion of these fuels makes much thermal and
environmental pollution, which threatens our ecosystem. Lots of fuel energy in the internal
combustion engine is treated as the waste gas. Only 25% of the heat generated by fuel
combustion is used for driving vehicles, while 40% of the energy is discarded by exhaust gas,
30% of the energy is released through coolant, and 5% of the power is transferred to friction.
That means the recovery of waste gas has excellent research potential.
1.5. Rational of the Study
The project is geared to improving the efficiency of the hybrid vehicle exhaust heat recovery
device. The project would solve such challenges among team low efficiency of energy
conversion, complex structure, difficult implementation, single use as well as large volume
among others. The number of electrical components that are found within a car system has
significantly increased aimed at enhancing the performance, convenience, comfort as well as
safety in the automobiles resulting in a sharp increase in the rated power of the on-board
generators including supply of automotive loads including electric steering system, air
conditioning, high energy discharge lamps as well as electric brakes. There is high power loss of
Rendel alternator is relatively high as a result of increased electric power that is used on the
vehicle. The 14V voltage level used in today's automobiles leads to an increase in current, which
leads to a thicker wiring harness. As a result, the cost of the whole power system increases while
the performance decreases significantly.

1.6. Research Hypothesis
Organic Rankine Cycle waste heat recovery system plays a major role in enhancing the
performance of a hybrid vehicle with regard to the energy efficiency.
1.7. Thesis Outline
The dissertation has six chapters as discussed below
Chapter 1: Introduction-The research topic is brought to limelight and a precise background
provided. The aim as well as objectives, research questions alongside significance of study is
highlighted. The main function if this chapter is to make known as well as brief reader of the
dissertation on what is availed in other chapters
Chapter 2: Literature review-Previous journals alongside works of other authors about waste heat
recovery, modes of operation of hybrid vehicles and organic Rankine cycle are discussed at
length. The main role of this chapter is to arm the researcher and reader with an elaborate
comprehension of the topic of the research.
Chapter 3: Methodology-The chapter is a discussion on approaches adopted in data collection
alongside various data collection methods used
Chapter 4: Discussions-The information that was obtained from literature review is elaborated
comprehensively with reference to research aims as well as objectives. In the chapter, answers to
research questions are sought
Chapter 5: Conclusion-This chapter offers study summary of the research conducted.
Recommendations and final remarks are included in this chapter

Chapter 6: References-All information sources of the data used in the dissertation are noted in
this chapter and such include books, journals, and articles among other sources which contain
relevant information to the research topic.

CHAPTER 2: LITERATURE REVIEW
2.1. Introduction
This chapter provides a discussion on previous journals and works of other authors regarding
waste heat recovery, modes of operation of hybrid vehicles and organic Rankine cycle are at
length. The main purpose of this chapter is to bring to light what previous experts have been able
to achieve as far as the research topic is concerned which would then provide a foundation on
which the current research and the solutions to the research questions are concerned.
2.2. Hybrid Vehicle Operational Modes
A hybrid electric vehicle defines hybrid vehicle type which brings together conventional internal
combustion engine system as well as electric propulsion system. The availability of electric
powertrain is aimed at attaining either enhanced fuel economy in comparison with conventional
vehicle or even better performance (Macián et al., 2013). There are numerous types of hybrid
electric vehicles and the extent of each function as an electric vehicle is as well variable. The
hybrid electric car is the most commonly used type of hybrid electric vehicle even though there
are as well hybrid electric Buse and hybrid electric trucks.
Modern hybrid electric vehicles adopt efficiency-enhancing technologies including regenerative
brakes that change the kinetic energy of the vehicle to electric energy that is stored in a super-
capacitor or a battery. Some types of hybrid electric vehicles make use of an internal combustion
engine to rotate an electric generator that either recharges the batteries of the vehicle or powers it
directly of the electric drive motors; a combination known as motor generator. Most of the
hybrid electric vehicles lower ideal emissions through switching off engine at idle as well as
restarting it in case there is need which are called as start-stop system. A hybrid electric
generates low tailpipe emissions in comparison with a sized gasoline car as the gasoline engine
of the hybrid is often smaller in relation to the gasoline powered vehicle. In case the engine is not

used in driving the car directly, it may be geared to operate at maximum efficiency hence
enhancing the economy of fuel (Jadhao and Thombare, 2013).
2.2.1 Theory of Operation
Hybrid cars may work differently based on the driving mode. The typical driving may be
grouped into four various modes. Knwoledge on how the hybrid vehicle works under very mode
is important in getting most gas mileage as well as minimizing the output of emissions. While
the car makers do not specify on the same, it is made to get super high gas mileage regardless of
how the driving is done. The four driving modes of hybrid vehicles as well as their theory of
operation are as discussed below:
2.2.1.1. Full stop
At a full stop just as is the case with a red light traffic or even a stop light, the gas engine often
closes down to remove idling as well as lower emissions. The electric motor is at the moment
ready in propulsion of the car when pushing on gas pedal. In densely populated cities having
numerous stop and go traffic this may save as far as fuel is concerned.
2.2.1.2. Initial acceleration from a stop
Beginning from a stop, the electric motor aids in accelerating the car with the power extracted
from the battery pack. In the case of downtown stop and go traffic one may save most of the fuel
with the use of hybrids as opposed to regular cars in which most of the fuel is burnt. The gas
engine switches off and on as required when one drives. Rapid acceleration would stull damage
the gas mileage just as is the case with conventional cars (Shabashevich et al., 2015).
2.2.1.3. Highway Driving
This is case in which fuel efficiency of a hybrid vehicle is not the same as a regular car. Lower
mileage is attained on the highway in comparison with the city. The backing behind is in the
driving mode car is basically powered only using gas engine that may be charging the electric