Report

BATTERY REPLACEMENT WITH COMPREESED AIR TANK
IN RENEWABLE SOURCE
Group Members
Kashif Ali Raja ECI-IT-11-124
M.Tayyab ECI-IT-11-100
S.Junaid Hussain ECI-IT-11-153
Project Supervisor
ENGR. MUHAMMAD SIDDIQUE
Department of Electrical Engineering
Hamdard University Karachi, Islamabad Campus
<BATCH 2011-2015>

BATTERY REPLACEMENT WITH COMPREESED AIR
TANK IN RENEWABLE SOURCE
Submitted By
Kashif Ali Raja,M.Tayyab,Junaid Hussain shah
Towards partial fulfillment of requirement for the award of Degree of
Bachelors of Electrical Engineering
Department of Electrical Engineering
Hamdard University Karachi, Islamabad Campus

CERTIFICATE
This is to certify that this project report entitled “battery replacement with compressed air tank
in renewable source” by Kashif Ali Raja,, M.Tayyab,Junaid husain shah submitted in partial
fulfillment of the Requirements for The Bachelors of Electrical Engineering from Hamdard
University Karachi, Islamabad Campus is the record of candidates own work carried out by
them under our supervision & guidance. In our opinion the work submitted has reached a level
required for being accepted for exam. The matter embodied in this project has not been
submitted to any other university or institute.
Final Grade Received Group A+
Committee:
1. Project Supervisor Signature
Engr.Muhammad Siddique
2. Examiner 1 Signature
_________________________ _________________________
3. Examiner 2 Signature
_________________________ _________________________

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TABLE OF CONTENTS
Table of contents……………………………………………………………………………..........ii
List of figures…………………………………………………………………………………….vii
List of Abbreviations………………………………………………………………………...........ix
Abstract……………………………………………………………………………………………x
Dedication………………………………………………………………………………………...xi
Acknowledgment…………………………………………………………………………….......xii
Chapter 1: Introduction………………………………………………………………………….1
1.1 Power Energy………………………………………………………………………………….1
1.2 Compressed Air………………………………………………………………………………..2
1.3 Compressed Air Storage………………………………………………………………….........3
1.4 Project Aim………………………….........................................................................................4
1.5Project Objectives……………………………………………………………………………...4
1.6 Report Organization…………………………………………………………………………...5
Chapter 2: Literature view…………………………………………………………………........6
2.1 Literature view…………………………………………………………………………….......6
2.2 Energy Storage Technologies………………………………………………………………….6
2.3 Methods of Conventional CAES………………………………………………………............8
2.4 Small Scale Compressed Air Storage………………………………………………………….8
Chapter 3: Dynamics of compressor……………………………………………………..........13
3.1 How can air generate power?...................................................................................................13
3.2 Advantage of air power………………………………………………………………………13
3.3 Air power versus electrical power…………………………………………………………...14
3.4 Air power versus hydraulic power…………………………………………………………...14

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3.5 Type of compressor………………………………………………………………………......15
3.5.1 Reciprocating single acting compressor…………………………………………...15
3.5.2 Rocking piston compressor………………………………………………………...16
3.5.3 Diaphragm type…………………………………………………..………………...17
3.5.4 Rotary sliding van type…………………………………………………………….18
3.5.5 Rotary helical screw type…………………………………………………………..18
3.5.6 Rotary scroll type…………………………………………………………………..19
3.6 Type of control……………………………………………………………………………….20
3.7 Type of drives………………………………………………………………………………..21
3.8 Air compressor package units…………………………………………….……………….....21
3.9 Air compressor performance………………………………………………………………....22
3.10 Air compressor installation…………………………………………………………………23
3.10.1 Location…………………………………………………………………………..23
3.10.2 Motor overload protection………………………………………………………..24
Chapter 4: Hardware Description……………………………………………………..............25
4.1 Compressor…………………………………………………………………………………..25
4.2 Types of compressor………………………………………………………………………….26
4.3 Types of drivers……………………………………………………………………………....26
4.4 Accessories of compressor…………………………………………………………………...26
4.5 Turbine……………………………………………………………………………………….27
4.6 Pressure gauge………………………………………………………………………………..28
4.7 DC generator…...…………………………………………………………………………….29
4.7.1 Turbo generator…………………………………………………………………….29
4.7.2 Permanent magnetic generator……………………………………………………..29
4.7.3 Tacho generator…………………………………………………………………….29
4.8 Servo motor…………………………………………………………………………………..30
4.8.1 Mechanism of servo motor…………………………………………………………31

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4.9 Arduino UNO rev 3 board …...……………………………………………………………….32
4.10 Valves (ball valves)………………………………………………………………………....33
4.10.1 Body design……………………………………………………………………….33
Chapter 5: Implementation of the Project……….………………………………………….....35
5.1 Compressed air accessories…………………………………………………………………..35
5.1.1 Air Receive tank……………………………………………………………………36
5.1.2 Motor……………………………………………………………………………….36
5.1.3 Reciprocating single acting compressor……………………………………………37
5.2 Pressure gauge………………………………………………………………………………..37
5.3 Solenoid valves (ball valve)…………………………………………………………………..38
5.4 Turbine……………………………………………………………………………………….38
5.5 Generator……………………………………………………………………………………..38
5.6 Control circuitry……………………………………………………………………………...39
5.6.1 Tacho generator…………………………………………………………………….40
5.7 Hardware layout……………………………………………………………………………...40
Chapter 6: Results and Discussion……………………………………………………………..43
6.1 Theoretical Analysis………………………………………………………………………….43
6.2 Practical Analysis…………………………………………………………………………….43
6.3 Total Energy used to fill Compressor Receiver……………………………………………….44
6.4 Estimation on size of Receiver for SCAES…………………………………………………...44
6.5 The efficiency of a Compressor Air System………………………………………………….45
6.6 Other Alternatives……………………………………………………………………………46
Chapter 7: Conclusion and Further Recommendation……………………………………….49
7.1 Conclusion……………………………………………………………………………………49
7.3 Further Recommendation…………………………………………………………………….49
REFERNCES…………………………………………………………………………………...50

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Appendices………………………………………………………………………………………52
Appendix A Basic Definition……………………………………………………………………52
Appendix B 9Volt Battery……………………………………………………………………….56
Appendix C Comparison of Storage Technology………………………………………………..57
Appendix D Ideal Thermodynamics Calculation………………………………………………...58
Appendix E Evaluating True CFM Rating of an Air Compressor……………………………….61
Appendix F Comparison of Battery and Compressor……………………………………………62
Appendix G Automation of Motor Control Coding……………………………………………...63

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LIST OF FIGURES
Figure 1.1 Conversion of atmospheric air into compressed air…………………………………….2
Figure 1.2 Compressed air…………………………………………………………………………4
Figure 2.1 Classification of energy storage………………………………………………………...7
Figure 2.2 First generation………………………………………………………………………..10
Figure 2.3 Second generation…………………………………………………………………….10
Figure 2.4 Third generation………………………………………………………………………11
Figure 3.1 Reciprocating single ………………………………………………………………….15
Figure 3.2 Reciprocating two stage………………………………………………………………16
Figure 3.3 Rocking piston type…………………………………………………………………...17
Figure 3.4 Diaphragm type……………………………………………………………………….17
Figure 3.5 Rotary vane type………………………………………………………………………18
Figure 3.6 Rotary helical screw…………………………………………………………………..19
Figure 3.7 Rotative scroll………………………………………………………………………...20
Figure 3.8 Starter type……………………………………………………………………………23
Figure 4.1 Air flow turbine……………………………………………………………………….28
Figure 4.2 Pressure gauge………………………………………………………………………...28
Figure 4.3 Servo motor…………………………………………………………………………...30
Figure 4.4 Mechanism of servo motor……………………………………………………………31
Figure 4.5 Arduino UNO rev 3 board………………………….…………………………………32
Figure 4.6 Floating ball valves single piece………………………………………………………34
Figure 5.1 Motor………………………………………………………………………………….37
Figure 5.2 DC motor……...………………………………………………………………………39
Figure 5.3 Hardware layout 1……………………………………………………………………41
Figure 5.4 Hardware layout 2……………………………………………………………………42
Figure 6.1 Size of energy storage…………………………………………………………………45

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LIST OF ABBREVIATIONS
AI Air Injection
AEC Alabama Electric Cooperative
BCF Billion Cubic Feet
BOP Balance of Plant
CEC California Energy Commission
CAES Compressed Air Energy Storage
SCAES Small Compressed Air Energy Storage
CF Cubic Feet
CT Combustion Turbine
EPRI Electric Power Research Institute)
Gt Gega Ton (1000 Mega Ton, 1 Billion Ton)
HP High Pressure
HRR Heat Recovery Recuperator
IPP Independent Power Producer
LP Low Pressure
MM Million (from Roman Numerals)
Mt Mega Ton (Million Ton))
MW Mega Watt (Million Watt)
NA Not Applicable
PG&E Pacific Gas and Electric
PSI Pounds Per Square Inch
PV Photo Voltaic

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ABSTRACT
Compressed air energy storage (CAES) is a commercial, utility-scale technology that provides
long-duration energy storage with fast ramp rates and good part-load operation. It is a promising
storage technology for balancing the large-scale penetration of renewable energies, such as wind
and solar power, into electric grids. This study proposes a CAES-CC system, which is based on a
conventional CAES combined with a steam turbine cycle by waste heat boiler. Simulation and
thermodynamic analysis are carried out on the proposed CAES-CC system. The electricity and
heating rates of the proposed CAES-CC system are lower than those of the conventional CAES by
0.127 kWh/kWh and 0.338 kWh/kWh, respectively, because the CAES-CC system recycles high-
temperature turbine-exhausting air. The overall efficiency of the CAES-CC system is improved
by approximately 10% compared with that of the conventional CAES. In the CAES-CC system,
compressing intercooler heat can keep the steam turbine on hot standby, thus improving the
flexibility of CAES-CC. This study brought about a new method for improving the efficiency of
CAES and provided new thoughts for integrating CAES with other electricity-generating modes.

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Dedication
First of all we would to like to thank “Allah Almighty the most gracious and the most merciful”.
Specially dedicated to our families for their support and encouragement throughout our life.

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Acknowledgements
Apart from our faculty members we would also like to thank our classmates and friends for being
with us in this journey and making it memorable.
Lastly we would like to thank all the faculty members of Hamdard Institute of Engineering and
Technology (HIET) for their support throughout the Degree.
Our project has been a result of our own hard work but this project could not have become a reality
without the support and help of many of our friends and faculty members. We take this opportunity
to acknowledge their help and thank them for their good will. We would like to thank our project
supervisor Engr Muhammad Siddique for his support and cooperation.

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CHAPTER 1
INTRODUCTION
Pakistan has a sparse population, peaky energy demand profile and extensive untapped renewable
energy resources. The energy sector understands that continuing on the path of traditional power
generation and transmission / distribution system augmentation is becoming ever-more expensive.
The situation is seemingly right for the broad scale adoption of alternatives such as energy storage.
Electricity supply can be divided into four stages: generation, transmission, distribution, and retail.
Although there is a growing base of renewable energy supply in Australia (e.g. wind, hydro, solar)
most electricity is generated by burning fossil fuels (e.g. coal, gas and oil) at large scale
conventional power stations.
These generators, and their fuel, are typically located a long way from where the electricity is
consumed. Moving electricity across these long distances therefore requires a capital-intensive
transmission network to deliver electricity to substations located near demand centers.
Balancing electricity supply and demand at all times becomes more challenging in power systems
with higher levels of renewable generation. Inevitably, a significant part of the renewable energy
supply will be intermittent, depending on weather conditions that are variable on several time
In an article from the Pakistan “Rooftop solar panels overloading electricity grid” it was reported
that feeding so much solar power back into the network is stressing the system and causing voltage
rises which could damage household devices. In addition to this a spokesman from Energex told
The Pakistan that “it is becoming more difficult for electricity distribution authorities to set up the
power system to ensure correct voltages.
1.1 What is Power and Energy?
Before exploring how to store energy there are two terms, which definitions need to be clarified;
these are Power and Energy:

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Power is the rate of which work is done in Watts (W)
Energy is the potential to do work in Joules (J).
It should be noted that electrical energy is not "stored" in an electrical network as water or gas is
stored in pipes which transports it. Energy is produced by the movement of electrons in a current;
when an appliance is switched on, energy is instantly transmitted to it from the generator (via this
current) at close to the speed of light. If the generator were to be turned off the current would
instantly stop.
1.2 What is Compressed Air?
Compressed air is a form of stored energy that is used to operate machinery, equipment, or
processes is shown in figure 1.1. Compressed air is used in most manufacturing and some service
industries, often where it is impractical or hazardous to use electrical energy directly to supply
power to tools and equipment.
Figure 1.1 Conversion of atmospheric air into compressed Air
Powered by electricity, a typical air compressor takes approximately seven volumes of air at
atmospheric conditions, and squeezes it into one volume at elevated pressure (about 700 kpa). The

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resulting high pressure air is distributed to equipment or tools, where it releases useful energy to
the operating tool or equipment as it is expanded back to atmospheric pressure. (Cunha, 2012)
It’s important to remember that compressing air involves two different variables which are
Pressure and Volume:
Pressure (kPa) is the measure of how hard the air is pushing against the inside of whatever it is
contained in.
Volume (m3) determines how much air will fit inside of a container.
1.3 Compressed Air Storage
Compressed air energy storage is a developing technology that has the potential to meet the needs
of intermittent sustainable energy sources and high peak load electrical power demands. With a
very long service period, low cost of energy, low cost of maintenance and operation, and high
power efficiency the CAES power plant produces power by storing energy during off peak periods
(Das & McCauley, 2012). This is done in the form of compressed air and used on demand during
the peak periods to generate power with a turbo generator / gas turbine system.
The design behind a CAES system is to use electric power to run compressors that compresses air
into a tank / reservoir at very high pressure, and then the air is used under pressure, to turn a turbine
creating power on demand. The model shown in figure 1.2. Small scale systems have long been
used in such applications as propulsion of mine locomotives.
Large scale applications must conserve the heat energy associated with compressing air;
dissipating heat lowers the energy efficiency of the storage system.

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Figure 1.2 Compressed Air Storage
1.4 Project Aim
To investigate the feasibility of using a Small scale Compressed Air Energy Systems (SCAES) in
a domestic household application i.e. to offset the peak demand air conditioning places on local
distribution networks and household economies.
1.5 Project Objectives
1. Research the existing literature on renewable energies and in particular CAES.
2. Design a CAES as a storage and regeneration plant for a domestic household using off-the-
shelf componentry.
3. Identify all alternatives for the primary energy generation system. PV, wind, solar thermal etc.
4. Investigate direct air compression from the primary energy source, e.g. wind turbine driven
compressor.

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5. Identify efficiency of energy transfer of the various options
6. Identify cost effective componentry that matches the system requirements
7. Create a computational model to assist in system design and optimization
8. Use the model to analyses the potential for CAES to be employed as a cost effective functional
alternative energy storage and regeneration system for domestic households.
9. Implement the CAES design using off-the-shelf componentry into a domestic household
application to confirm design and results
1.6 Report Organization
This report describes the full development and testing of an Air compressed system as a storage.
The report is organized by section of the development process. The upcoming Chapters 1 are
going to provide further details about the compressed system and how it has been accomplished.
Chapter 2 Covers Literature review. Chapter 3 describes the dynamics and overall function of
the compressed system Chapter 4 describes the designing of the project and puts forth the
components used in the construction of the project and mentions the decision process of selecting
each component it also presents a block diagram of the compressed system Chapter 5 explains
how this project is implemented. Chapter 6 Introduce the compressed system and the components
used. Lastly Chapter 7 discusses conclusions of the project and further additions which could be
made to.

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CHAPTER 2
LITERATURE VIEW
2.1 Literature View
In order to better understand contemporary CAES technology and research, it was important to
perform a literature review of existing papers, books and other research material. The largest
information resource available was the internet, with selected textbooks on energy storage
available in academic libraries [2].
In carrying out the review it was found that there were concerns with the following:
1. The amount of losses within a system which decreased efficiencies. These losses were mainly
associated to the heat of compression.
2. The physical size of receiver for the hours of energy storage.
2.2 Energy Storage Technologies
Energy storage is a well-established concept yet still relatively unexplored (Connolly, 2010)[5]. A
number of very different methods exist to store “electric energy,” As explained in the
thermodynamics of gas storage section above, compressing air heats it and expanding it cools it.
Therefore, practical air engines require heat exchangers in order to avoid excessively high or low
temperatures and even so don't reach ideal constant temperature conditions, or ideal thermal
insulation.

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Figure 2.1 Classification of energy storage systems
Only two of those shown actually store the energy in electric form: super-capacitors and
superconducting magnetic energy storage, which keep the energy as electric charge or magnetic fields
respectively. These storage technologies can also be compared in terms of power quality and discharge
time.
Most energy storage systems require the useful energy to be converted from its initial state into
another form which is more suitable for storage is shown in figure 2.1[8]. When ready to use it is
then converted back into a useful form. In each conversion there is a loss associated with the
efficiency of the conversion process, and a comparison of several energy storage methods should
take the full turn around efficiency of the storage method into account.
Batteries actually store the energy in a chemical form, but the natural operation of the battery
converts the power to direct current electric power upon being provided with a pathway for the
power to flow. Mechanical storage includes several types of flywheels, compressed air and
pumped hydro systems. Thermal storage systems use electricity to heat a liquid to very high
temperatures and then use that, via a heat exchanger, to heat steam to drive a steam turbine
generator or a sterling cycle generator.
Energy storage systems have always had the back seat when generators can produce energy in real
time as it is being consumed. The large upfront costs of building storage system and the cost

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associated with energy losses that occur in converting the energy from one form to another for
storage has made it hard for energy storage to compete.
2.3 Methods of Conventional CAES
The CAES technology consists of converting excess base load energy into stored pneumatic
energy in pressure vessels or underground caverns by means of a compressor for later release
though a gas turbine as premium peaking power [7].
During compression, heat is generated which is removed before it is stored. This heat energy can
be stored in thermal energy storage for use at a later stage. In a power plant with a standard gas
turbine, approximately two-thirds of the gas is used to compress the air. It therefore makes sense
to use off-peak electrical power to pre-compress the air, and later use the compressed air in the gas
turbines when the turbines are producing electricity during peak hours. In this way, three times the
power is produced for the same fuel consumption [7].
Three different types of underground cavities have been considered for CAES; excavated salt
domes because salt self-seals under pressure, cavities in rock formations (either natural or
excavated) and aquifers. Due to the limited availability of natural locations, sites can be costly and
the stability of any cavern to withstand cycling temperature and pressure must be fully tested and
understood prim 2011.
Currently two CAES plants are operational in the world, one in Huntorf, Germany, and the other
in McIntosh, Alabama, USA. Both plants use excavated salt domes for storage.
Table shows that the McIntosh plant has a lower total amount of energy per unit output, but this is
a new plant with a recuperate which utilizes the waste heat in the turbine exhaust gases to preheat
the compressed air entering the turbines prim 2011.
2.4 Small Scale CAES
SCAES is the same concept of the larger CAES system just on a small scale. This technology
would dramatically lighten the loads on networks, help people who cannot connect to a power grid
and serves as an advantage to those people living in developing countries.
Dominique et al investigated the possibility of, off the gird CAES system which uses photovoltaic
(PV) panels as the energy source. Specific details of the paper were the development of PV-CAES

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systems that can be operated at very low powers to optimally utilize the output of individual PV
panels [9].
To achieve this, a single stage isothermal compression system running (10-60 RPM) at that utilizes
a fluid piston was designed and examined. Focus was on achieving high efficiencies that can utilize
the entire range of the electrical output of a standard residential 160 Watt PV panel, which may
not be conducive for operating commercial compressors.
An advantage of the hybrid system was that there would be a decrease in energy losses. This is
due to the reduction in the number of moving parts / components required for the multistage
conversion of solar energy to compressed air to powering household units [12]
The hybrid system employs a fluid piston which increases volumetric efficiency as well as reduce
dead volume, which corresponds to the clearance between piston radius and outlet.
For different stroke lengths the liquid volume was varied and pressures monitored. In a closed
system the increase in fluid amount leads to an increase in final pressure due to the consequent
decrease in "dead volume".
Paloheimoetal have studied CAES for portable electrical and electronic devices like mobile phones
and rural off grid connection which would help developing countries.
Assessments were made on renewability efficiency and compared the storage mediums with the
likes of batteries. During the course of the study it was obvious that different types of storage
equipment use different principles and therefore a direct comparison of storage mediums tends to
be very complex. For comparison between storage systems the following parameters were used;
overall efficiency, optimal power output and stored energy.
It was said that the benefits of compressed air over electric storage are the longer lifetime of
pressure vessels compared to batteries and the materials are entirely benign as well as the costs are
potentially lower. But the costs for production of advanced pressure vessels are still high. On the
other hand, batteries provide nearly constant voltage over their entire charge level, whereas the
pressure of compressed air storage varies the charge level (Paloheimo & Omidiora, 2009)[9].
First generation refers to a conventional plant which comprises of both compression and generation
components.

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The first operational system was Huntorf, Germany in 1979 and the second was McIntosh,
Alabama in 1991 is shown in figure 2.2.
Figure 2.2 First generation of cases
Second generation is shown in figure 2.3 very similar to the first however advancements were
made in technology and turn around efficiencies are approximately 54% compared with (48%-
50%) for a first generation system.
Figure 2.3 Second generation
Third generation or adiabatic CAES system does not use natural gas in the generation process (as
the latest design uses molten salt heat storage, heated with solar thermal power generators) is
shown in figure 2.4. This system stores the heat of compression which is re-used during generation
to warm the compressed air.

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One benefit of this generation is zero carbon emissions as there is no fuel consumption required in
the turbine section.
Figure 2.4 Third generation
Large CAES plants require a suitable sealed underground cavern for air storage as above ground
vessels do not have the scale necessary. It has been found that the mined salt rock caverns are the
best option for storage, while aquifers and abandoned mines and depleted oil and gas fields are
promising. Salt cavern for CAES operated between 40-100bars. These pressures result in the
cavern being contained between 450m deep and a volume of 150,000m or 580000m.
Varin Vongmanee conducted a study on the renewable energy applications for uninterruptible
power supply based on compressed air energy storage system. The study used wind energy to
produce the compressed air power via a compressor.
Varin states ‘because wind power is primarily uncontrollable as an energy source it requires a
CAES plants to store wind energy. Which then can be distributed during power outage, used during
peak hours or peak shaving, or when energy is needed and cost of energy is high’.

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As wind energy is kinetic energy and requires large masses of air moving over the earth’s surface.
The wind turbine receives kinetic energy that is transformed to mechanical or electrical forms
depending on end use.
The simulation results show that the compression and expansion pressure directly depends on air
flow rate and system efficiency. With improvements to the system efficiency of thermodynamic
conversion, the system should be able to operate by increasing pressure ratio of compression, or
increasing the pressure of expansion power [15].
Although more stages can increase efficiency, the system is complex and incurs high initial and
maintenance cost. His proposed simulation results could be used for backup power system and
peak shaping for energy management applications.

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CHAPTER 3
DYNAMICS OF COMPRESSOR
3.1 How Can Air Generate Power?
The normal state of air, barometric, is called atmospheric pressure. When air is compressed, it is
under pressure greater than that of the atmosphere and it characteristically attempts to return to its
normal state. Since energy is required to compress the air that energy is released as the air expands
and returns to atmospheric pressure. Our ancestors knew that compressed air could be used for
power when they discovered that internal energy stored in compressed air is directly convertible
to work. Air compressors were designed to compress air to higher pressures and harness that
energy. Unlike other sources of power, no conversion from another form of energy such as heat is
involved at the point of application. Compressed air, or pneumatic devices are therefore
characterized by a high power-to-weight or power-to-volume ratio. Not as fast as electricity, nor
as slow as hydraulics, compressed air finds a broad field of applications for which its response and
speed make it ideally suited. Where there is an overlap, the choice often depends on cost and
efficiency, and air is likely to hold the advantage. Compressed air produces smooth translation
with more uniform force, unlike equipment that involves translatory forces in a variable force field.
It is a utility that is generated in-house, so owners have more control over it than any other utility.
In addition, air does not possess the potential shock hazard of electricity or the potential fire hazard
of oils. The advantages of air power will be discussed further in the proceeding pages.
3.2 Advantages of Air Power
When there are a dozen or more forms of energy to choose from, Here compressed air stacks up
against two of its competitors—electricity and hydraulics.

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3.3 Air Power versus Electric Power
Cost Air tools have fewer moving parts and are simpler in design, providing lower cost
maintenance and operation than electric tools.
Flexibility Air tools can be operated in areas where other power sources are unavailable, since
engine-driven portable compressors are their source of air power. Electric power requires a
stationary source.
Safety Air-powered equipment eliminates the dangers of electric shock and fire hazard. Air tools
also run cooler than electric tools and have the advantage of not being damaged from overload or
stalling.
Weight Air tools are lighter in weight than electric tools, allowing for a higher rate of production
per man- hour with less worker fatigue.
3.4 Air Power versus Hydraulic Power
Cost An air system has fewer parts than a hydraulic system, lowering service and maintenance
costs. Also, the use of a single compressed air supply permits operation of many separate systems
at once. Hydraulic systems require more complex and costly controls.
Flexibility Compressed air systems offer simpler installation than hydraulics, particularly where
tools are frequently interchanged. Compressed air systems also offer better adaptability for
automation and flexibility for changing or expanding operations.
Maintenance Air systems have less downtime than hydraulic systems because they have less
complex controls. Less preventative maintenance is required with air, whereas hydraulic fluids
must be monitored and replaced periodically.
Safety Hydraulic devices operating near open flame or high temperatures present fire hazards,
unless fire-resistant fluids are used. Leakage in hydraulic systems can result in the presence of
dangerous hydraulic fluids and even complete system shutdown. In contrast, compressed air
devices operate with lower system pressures, and accidental air leaks release no contaminants.

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Weight High ratio of power-to-weight in air tools contributes to a lower operator fatigue versus
hydraulic tools.
3.5 Types of Compressors
Air compressors in sizes from 1/4 to 30 horsepower include both reciprocating and rotary
compressors, which compress air in different ways. Major types of reciprocating compressors
include reciprocating single acting, reciprocating double acting, reciprocating diaphragm, and
reciprocating rocking piston type. Major types of rotary air compressors include rotary sliding
vane, rotary helical screw and rotary scroll air compressors.
3.5.1 Reciprocating Single Acting Compressors
Reciprocating single acting compressors are generally of one-stage or two-stage design.
Compressors can be of a lubricated, non-lubricated or oil-less design. In the single-stage
compressor, air is drawn in from the atmosphere and compressed to final pressure in a single
stroke. The single-stage reciprocating compressor is illustrated in figure 3.1.
Figure 3.1 Reciprocating single stage
Single-stage compressors are generally used for pressures of 70 psi (pounds per square inch) to
135 psi.
In the two-stage compressor, air is drawn in from the atmosphere and compressed to an
intermediate pressure in the first stage. Most of the heat of compression is removed as the

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compressed air then passes through the intercooler to the second stage, where it is compressed to
final pressure. The two-stage reciprocating compressor in figure 3.2.
Figure 3.2 Reciprocating two stage
Single and two-stage reciprocating Compressors are frequently used in auto and truck repair shops,
body shops, service businesses, and industrial plants. Although this type of compressor is usually
oil lubricated, hospitals and laboratories can purchase oil-less versions of the compressors.
3.5.2 Rocking Piston Type
Rocking piston compressors are variations of reciprocating piston type compressors figure3.4. This
type of compressor develops pressure through a reciprocating action of a one-piece connecting rod
and piston. The piston head rocks as it reciprocates. These compressors utilize non-metallic, low
friction rings and do not require lubrication. Some of the advantages of rotary sliding vane
compressors are smooth and pulse-free air output, compact size, low noise levels, and low
vibration levels.

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The rocking piston type compressors are generally of smaller size and lower pressure capability.
Figure 3.4 Rocking piston type
3.5.3 Diaphragm Type
Diaphragm compressors are a variation of reciprocating compressors in figure 3.5. The diaphragm
compressor develops pressure through a reciprocating or oscillating action of a flexible disc
actuated by an eccentric. Since a sliding seal is not required between moving parts, this design is
not lubricated. Diaphragm compressors are often selected when no contamination is allowed in the
output airline or atmosphere, such as hospital and laboratory applications. Diaphragm compressors
are limited in output and pressure, and they are used most for light-duty applications.
Figure 3.5 Diaphragm type

30
3.5.4 Rotary Sliding Vane Type
The rotary sliding vane compressor consists of a vane-type rotor mounted eccentrically in a
housing (Figure3.6). As the rotor turns, the vanes slide out against the housing. Air compression
occurs when the volume of the spaces between the sliding vanes is reduced as the rotor turns in
the eccentric cylinder. Single or multi-stage versions are available. This type of compressor may
or may not be oil lubricated. Oil-free rotary sliding vane compressors are restricted to low-pressure
applications because of high operating temperatures and sealing difficulties. Much higher
pressures can be obtained with oil lubricated versions. Some of the advantages of rotary sliding
vane compressors are smooth and pulse-free air output, compact size, low noise levels, and low
vibration levels.
Figure 3.6 Rotary vane type
3.5.5 Rotary Helical Screw Type
Rotary helical screw compressors utilize two intermeshing helical rotors in a twin-bore case. In a
single-stage design, the air inlet is usually located at the top of the cylinder near the drive shaft
end. The discharge port is located at the bottom of the opposite end of the cylinder in figure 3.7.
As the rotors unmet at the air inlet end of the cylinder, air is drawn into the cavity between the
main rotor lobes and the secondary rotor grooves. As rotation continues, the rotor tips pass the
edges of the inlet ports, trapping air in a cell formed by the rotor cavities and the cylinder wall.

31
Compression begins as further rotation causes the main rotor lobes to roll into the secondary rotor
grooves, reducing the volume and raising cell pressure. Oil is injected after cell closing to seal
clearances and remove heat of compression. Compression continues until the rotor tips pass the
discharge porting and release of the compressed air and oil mixture is obtained. Single or multi-
stage versions are available. This type of compressor can be oil lubricated, water lubricated or oil-
free. Some advantages of the rotary helical screw compressors are smooth and pulse-free air
output, compact size, high output volume, low vibrations, prolonged service intervals, and long
life.
Figure 3.7 Rotary helical screw
3.5.6 Rotary Scroll Type
Air compression within a scroll is accomplished by the interaction of a fixed and an orbiting helical
element that progressively compresses inlet air in Figure 3.8. This process is continuously
repeated, resulting in the delivery of pulsation-free compressed air. With fewer moving parts,
reduced maintenance becomes an operating advantage.

32
Scroll compressors can be of a lubricated or oil-free design.
Figure 3.8 Rotative scroll
3.6 Types of Controls
Controls are required for all compressors in order to regulate their operation in accordance with
compressed air demand. Different controls should be chosen for different types of compressor
applications and requirements. For continuous operation, when all or most of the air requirements
are of a steady nature, constant speed controls are required. Use constant speed controls whenever
the air requirement is 75 percent or more of the free air delivery of the air compressor or when
motor starts per hour exceed motor manufacturer recommendations. Constant speed controls
include load/unload control for all types and inlet valve modulation for rotary compressors.
Start-stop controls Are recommended for a compressor when adequate air storage is
provided and air requirement is less than 75 percent of the compressor free air delivery.
Dual controls Allow for switching between constant speed and start-stop operation by setting
a switch. With dual controls, the operator can select a different type of control to suit his or her
specific air requirements each time the compressor is used. Dual controls are helpful when a
compressor is used for a variety of applications.

33
Sequencing controls Provide alternate operation of each compressor at each operating cycle
and dual operation during peak demands. Sequencing controls are ideal for operating a group of
compressors at peak efficiency levels.
3.7 Types of Drives
Most compressors are driven with electric motors, internal combustion engines, or engine power
takeoffs. Three types of drives are commonly used with these power sources.
V-Belt Drives are most commonly used with electric motors and internal combustion engines.
V-Belt drives provide great flexibility in matching compressor load to power source load and speed
at minimum cost. Belts must be properly shielded for safety.
Direct Drives provide compactness and minimum drive maintenance. Compressors can be
flange mounted or direct-coupled to the power source. Couplings must be properly shielded for
safety. Lower horsepower compressors also are built as integral assemblies with electric motors.
Engine Drives gasoline or diesel engine, or power takeoff drives, are used primarily for
portability reasons. A gearbox, V-Belt, or direct drive is used to transmit power from the source to
the compressor.
3.8 Air Compressor Package Units
Air compressor packaged units are fully assembled air compressor systems, complete with air
compressor, electric motor, V-belt drive, air receiver, and automatic controls. Optional equipment
includes after coolers, automatic moisture drain, low oil safety control, electric starter, and pressure
reducing valve. Air compressor units come with a variety of configurations: gasoline or diesel
engines, optional direct drive, optional separate mounted air receivers, and more. The most
common type of packaged unit compressor configuration is the tank-mounted single acting, single-
or two-stage reciprocating design. Models are offered in the range of 1/4 through 30 horsepower.
Electric motors or gas engines drive the compressors. Most compressors available in this
horsepower range are air cooled. Installation is convenient because the unit requires only a
connection to electrical power and a connection to the compressed air system.

34
3.9 Air Compressor Performance
Delivery (ACFM/SCFM) The volume of compressed air delivered by an air compressor at
its discharge pressure, normally is stated in terms of prevailing atmospheric inlet conditions
(acfm). The corresponding flow rate in Standard cubic feet per minute (scfm) will depend upon
both the Standard used and the prevailing atmospheric inlet conditions. Varying flow rates for
more than one discharge pressure simply reflect the reduction in compressor volumetric efficiency
that occurs with increased system pressure (psig). For this reason, the maximum operating pressure
of a compressor should be chosen carefully.
Displacement (CFM) Displacement is the volume of the first stage cylinder(s) of a compressor
multiplied by the revolutions of the compressor in one minute. Because displacement does not take
into account inefficiencies related to heat and clearance volume, it is useful only as a general
reference value within the industry.
Diagnostics Controls Protective devices designed to shut down a compressor in the event of
malfunction. Devices may include high air temperature shut down, low oil level shut down and
low oil pressure shut down, preventative maintenance shut down, etc.
Accessories Standard accessories are available to help ensure reliable and trouble-free
compressor operation. Some special purpose devices also are available to meet unusual
requirements. Below is a list of commonly used accessories.
Air Receiver A receiver tank is used as a storage reservoir for compressed air. It permits the
compressor not to operate in a continuous run cycle. In addition, the receiver allows the
compressed air an opportunity to cool.
Belt Guard A belt guard protects against contact with belts from both sides of the drive and is
a mandatory feature for all V-belt driven compressor units where flywheel, motor pulley, and belts
are used.

35
Intake Filter He intake filter eliminates foreign particulate matter from the air at the intake
suction of the air compressor system. Dry (with consumable replacement element) or oil bath types
are available.
Manual and Magnetics Starters Manual and magnetic starters provide thermal overload
protection for motors is shown in figure 3.9 motors and are recommended for integral horsepower
and all three-phase motors. Local electrical codes should be checked before purchasing a starter.
Figure 3.9 Starter type
3.10 Air Compressor Installation
The main key points before the installation we check are as follows:
3.10.1 Location
The air compressor location should be as close as possible to the point where the compressed air
is to be used. It is also important to locate the compressor in a dry, clean, cool, and well-ventilated
area. Keep it away from dirt, vapor, and volatile fumes that may clog the intake filter and valves.
If a dry, clean space is unavailable, a remote air intake is recommended. The flywheel side of the
unit should be placed toward the wall and protected with a totally enclosed belt guard, but in no

36
case should the flywheel be closer than 12 inches to the wall. Allow space on all sides for air
circulation and for ease of maintenance. Make sure that the unit is mounted level, on a solid
foundation, so that there is no strain on the supporting feet or base. Solid shims may be used to
level the unit. In bolting or lagging down the unit, be careful not to over-tighten and impose strain.
3.10.2 Motor Overload Protection
All compressor motors should be equipped with overload protection to prevent motor damage.
Some motors are furnished with built-in thermal overload protection. Larger motors should be
used in conjunction with starters, which include thermal overload units. Such units ensure against
motor damage due to low voltage or undue load imposed on the motor. Care should be taken to
determine the proper thermal protection or heater element. The user should consider the following
variables: the load to be carried, the starting current, the running current, and ambient temperature.
Remember to recheck electric current characteristics against nameplate characteristics before
connecting wiring.

37
CHAPTER 4
HARDWARE DESCRIPTION
The term hardware refers to the various electronic components that are required for you to use a
computer or machine along with the hardware components inside the computer/Machine case. As
you know your project equipment is made of several common components.
 Air compressor cylinder
 Motor
 Piston
 Valves assembly
 Pressure gauge
 Air flow turbine
 DC generator
 Voltage divider circuit
 Power supply circuit
 LCD 16*4
 Arduino UNO rev 3
 Servo motor
4.1 Air Compressor
An air compressor is a device that converts power (usually from an electric motor, a diesel engine
or a gasoline engine) into potential energy by forcing air into a smaller volume and thus increasing
its pressure. The energy in the compressed air can be stored while the air remains pressurized. The
energy can be used for a variety of applications, usually by utilizing the kinetic energy of the air
as it is depressurized.

38
4.2 Types
 Positive Displacement (for brief introduction see article no 3.5)
 Reciprocating (for brief introduction see article no 3.5)
 Rotary Screw (for brief introduction see article no 3.5)
 Dynamic (for brief introduction see article no 3.5)
 Centrifugal (for brief introduction see article no 3.5)
 Axial flow (for brief introduction see article no 3.5)
4.3 Types of Drivers
Most compressors are driven with electric motors, internal combustion engines, or engine power
take offs. Three types of drives are commonly used with these power sources.
V-Belt Drives Are most commonly used with electric motors and internal combustion engines.
V-Belt drives provide great flexibility in matching compressor load to power source load and speed
at minimum cost. Belts must be properly shielded for safety.
Direct Drives Provide compactness and minimum drive maintenance. Compressors can be
flange mounted or direct-coupled to the power source. Couplings must be properly shielded for
safety. Lower horsepower compressors also are built as integral assemblies with electric motors.
Engine Drives Gasoline or diesel engine, or power takeoff drives, are used primarily for
portability reasons. A gearbox, V-Belt, or direct drive is used to transmit power from the source to
the compressor.
4.4 Accessories of Compressors:
Standard accessories are available to help ensure reliable and trouble-free compressor operation.
Some special purpose devices also are available to meet unusual requirements. Below is a list of
commonly used accessories.

39
Air Receiver A receiver tank is used as a storage reservoir for compressed air. It permits the
compressor not to operate in a continuous run cycle. In addition, the receiver allows the
compressed air an opportunity to cool.
Belt Guard A belt guard protects against contact with belts from both sides of the drive and is
a mandatory feature for all V-belt driven compressor units where flywheel, motor pulley, and belts
are used.
Diagnostic Controls Protective devices designed to shut down a compressor in the event of
malfunction. Devices may include high air temperature shut down, low oil level shut down and
low oil pressure shut down, preventative maintenance shut down, etc.
Intake Filter The intake filter eliminates foreign particulate matter from the air at the intake
suction of the air compressor system. Dry (with consumable replacement element) or oil bath types
are available.
Manual and Magnetic Starter Manual and magnetic starters provide thermal overload
protection for motors and are recommended for integral horsepower and all three-phase motors.
Local electrical codes should be checked before purchasing a starter.
4.5 Turbine
A turbine is a rotary mechanical device is shown in figure 4.1 that extracts energy from a air flow
and converts it in to useful work. A turbine is a turbo machine with at least one moving part called
a rotor assembly, which is a shaft or drum with blades attached. Compressed air acts on the blades
so that they move and impart rotational energy to the rotor. When the solenoid valve of the
compressed air is open then the compressed air through the stationary nozzle hits the blades and
rotate the turbine. Due to the air pressure the blades will move along his rotor. As the pressure of

40
the air through nozzle increase it will increase the rotation of the turbine. This turbine is fully
synchronized with DC Generator through Belt .As well as turbine moves the Generator will also
with same speed. And this Generator gives DC volts as a output.
Figure 4.1 Air flow turbine
4.6 Pressure Gauge
The pressure gauge is used for the indication of pressure .it has a diaphragm in side to which the
needle is attached. Adjacent to the mechanical safety valve is the pressure gauge given below in
figure. This is a china made pressure gauge with gauge comes with a electronic switch is shown
in figure 4.2. This switch has a trigger alarm which gives a digital signal if the pressure reaches a
certain limit. That signal will be send to the automated control system later in the project a
maximum display of 150 psi.
Figure 4.2 Pressure gauge

41
4.7 DC Generator
It is a machine which converts mechanical energy into electrical energy. It has a moving part called
rotor and a stationary part called stator. A generator has two types of windings: Field winding and
armature winding. It produces electrical energy working on the principle of Lenz’s law; emf = -
dΦ/dt. Simply, emf is induced if a coil is rotated in a fixed magnetic field (DC generator) or if a
magnetic field is rotated around a fixed coil (AC generator).
4.7.1 Turbo-Generators
A turbo generator is the combination of a turbine directly connected to an electric generator for
the generation of electric power. Different ways of coupling of Generators one of them is coupling
through pullies and rubber belt.
4.7.2 Permanent Magnet Generator (PMG)
In a permanent magnet generator, the magnetic field of the rotor is produced by permanent
magnets. Other types of generator use electromagnets to produce a magnetic field in a rotor
winding. The direct current in the rotor field winding is fed through a slip-ring assembly or
provided by a brushless exciter on the same shaft.
4.7.3 Tacho Generator
An electromechanical generator is a device capable of producing electrical power from mechanical
energy, usually the turning of a shaft. When not connected to a load resistance, generators will
generate voltage roughly proportional to shaft speed. With precise construction and design,
generators can be built to produce very precise voltages for certain ranges of shaft speeds, thus
making them well-suited as measurement devices for shaft speed in mechanical equipment. A
generator specially designed and constructed for this use is called tachometer or tacho generator.
Often, the word "tacho" (pronounced "tack") is used rather than the whole word.By measuring the
voltage produced by a tacho generator, you can easily determine the rotational speed of whatever
it’s mechanically attached to. One of the more common voltage signal ranges used with tacho
generators is 0 to 10 volts. Obviously, since a tacho generator cannot produce voltage when it’s
not turning, the zero cannot be "live" in this signal standard. Tacho generators can be purchased

42
with different "full-scale" (10 volt) speeds for different applications. Although a voltage divider
could theoretically be used with a tacho generator to extend the measurable speed range in the 0-
10 volt scale, it is not advisable to significantly over speed a precision instrument like this, or its
life will be shortened.
Tacho generators can also indicate the direction of rotation by the polarity of the output voltage.
When a permanent-magnet style DC generator's rotational direction is reversed, the polarity of its
output voltage will switch. In measurement and control systems where directional indication is
needed, tacho generators provide an easy way to determine that.
Tacho generators are frequently used to measure the speeds of electric motors, engines, and the
equipment they power: conveyor belts, machine tools, mixers, fans, etc.
4.8 Servo Motor
A servomotor is a rotary actuator that allows for precise control of angular position, velocity and
acceleration is shown in figure 4.4. It consists of a suitable motor coupled to a sensor for position
feedback. It also requires a relatively sophisticated controller, often a dedicated module designed
specifically for use with servomotors.
Servomotors are not a specific class of motor although the term servomotor is often used to refer
to a motor suitable for use in a closed-loop control system.
Figure 4.4 Servo motor

43
4.8.1 Mechanism
As the name suggests, a servomotor is a servo mechanism. More specifically, it is a closed-
loop servomechanism that uses position feedback to control its motion and final position. The input
to its control is some signal, either analogue or digital, representing the position commanded for
the output shaft.
The motor is paired with some type of encoder to provide position and speed feedback. In the
simplest case, only the position is measured. The measured position of the output is compared to
the command position, the external input to the controller. If the output position differs from that
required, an error signal is generated which then causes the motor to rotate in either direction, as
needed to bring the output shaft to the appropriate position. As the positions approach, the error
signal reduces to zero and the motor stops.
The very simplest servomotors use position-only sensing via a potentiometer and bang-bang
control of their motor; the motor always rotates at full speed (or is stopped). This type of
servomotor is not widely used in industrial motion control, but it forms the basis of the simple and
cheap servos used for radio-controlled models.
More sophisticated servomotors measure both the position and also the speed of the output shaft.
They may also control the speed of their motor, rather than always running at full speed. Both of
these enhancements, usually in combination with a PID control algorithm, allow the servomotor
to be brought to its commanded position more quickly and more precisely, with less overshooting.
Figure 4.5 Mechanism of servo motor

44
4.9 Arduino UNO Revision 3 Board
The Arduino Uno is one of the most common and widely used Arduino processor boards. There
are a wide variety of shields (plug in boards adding functionality). It is relatively inexpensive
(about $25 - $35).
The latest version as of this writing (3/2014) is Revision 3 (r3):
 Revision 2 added a pull-down resistor to the 8U2 HWB line, making it easier to put into
DFU (Device Firmware Update) mode.
 Revision 3 added
 SDA and SCL pins are now brought out to the header near the AREF pin (upper left on
picture). SDA and SCL are for the I2C interface.
 IOREF pin (middle lower on picture that allows shields to adapt to the voltage provided
 Another pin not connected reserved for future use the board can be powered from the
USB connector (usually up to 500ma for all electronics including shield), or from
the2.1mm barrel jack using a separate power supply when you cannot connect the board
to the PC’s USB port.
Figure 4.6 Arduino UNO revision 3 board

45
4.10 Valves (ball valves)
Ball valves are a low torque quarter turn valve, with low resistance to flow, suitable for many on-
off utility and process services. They have a straight through configuration. They have a good
control characteristic (equal percentage), but is not generally used forth rootling applications in
their standard form because of the potential for seat damage and cavitation (high pressure
recovery). Designs include floating ball and turn-on mounted ball types. Most designs are double
seated, but there are some special single seated designs e.g. eccentric ball (Orbit) types.
 The majority of valves have soft seat inserts and elastomer or polymer seals. Such valves
are recommended for clean service only and are unsuitable for dirty/abrasive service or
high temperatures. Hard metal seated designs are suitable for abrasive and scaling service
and versions having graphite stem, etc. seals can be used at elevated temperature.
 Reduced opening valves should normally be specified for lines which do not have to pass
pigs and if the increased velocity and pressure drop can be accommodated. They are not
recommended for fluids containing solids in which the resulting high velocity could cause
erosion.
 Levers should be mounted such that in the open position, the lever is parallel to the pipe
axis. Because smaller valves are lever operated (fast open/close), the possibility of
accidental operation should be considered.
 If “water hammer “would be unacceptable on liquid systems, valves should be gear
operated.
4.10.1 Body Design
There are three basic body designs:
 End or side entry (ball fitted through body ends).
 Top entry.
 All welded design.
All may be obtained in full opening (full bore) or reduced opening (reduced bore) versions is
shown in figure 4.7. End entry valves may comprise a single piece body (usually small, low

46
pressure designs with a threaded seat retainer. The removal of the central section of three piece
valves is only recommended in small sizes/low pressures. If larger size (e.g. >DN150 (NPS6)) end
entry valves are manufactured to order, at least one valve of each unique size and rating should be
hydro-tested with blank flanges or welded end caps so as to load the body joints
Figure 4.7 Floating ball valves
Bolting torque for other valves should then be confirmed to be identical. Top entry designs have
the advantage of only a single leak path to the environment which is not subject to piping loads
and offer the possibility of in-situ maintenance. In practice, in-situ maintenance may be limited by
the valve location, weight of ball, availability of lifting, etc. equipment and removal of the
complete valve is often necessary.

47
CHAPTER 5
IMPLEMENTATION OF THE PROJECT
The challenge of ensuring Pakistan has the energy it needs after the depletion of existing non-
renewable global energy is an issue that has been addressed in recent years with the development
of renewable energy sources such as solar and wind. This was an important step in ensuring that
energy provision problems do not arise for future generations. For this purpose we introduce a
“compressed air energy stored system” which not only increases the efficiency of renewable
sources but also save the source for other different purposes.
The major components used in our project are as follows:
1. Compressor system.
 Tank.
 Motor.
 Compressor.
2. Pressure gauge.
3. Control Solenoid valve.
4. Turbine.
5. Generator.
6. Arduino UNO rev3.
7. Control circuitry of valve.
5.1 Compressor System with Accessories
An air compressor is a device that converts power (usually from an electric motor, a diesel engine
or a gasoline engine) into potential energy by forcing air into a smaller volume and thus increasing
its pressure. The energy in the compressed air can be stored while the air remains pressurized. The
energy can be used for a variety of applications, usually by utilizing the kinetic energy of the air
as it is depressurized.

48
The Compressor system we are using in our project is ‘OWENG BM-2050’. Three major parts
combine to build a compressor system more efficient and effective to work in different conditions.
Names of the parts are:
 Air Receiver Tank.
 Motor.
 Compressor.
5.1.1 Air Receiver Tank
An air receiver tank is an integral and important part of any compressed air system. Typically a
receiver tank is sized at 6-10 times the flow rate of the system. So, if a compressor has a rating of
25 scfm at 100 psig, the receiver tank should be 150 cubic feet, minimum. In a compressed air
system, a receiver tank provides the following benefits:
1. The receiver tank acts as a reservoir of compressed air for peak demands.
2. Separate some of the moisture, oil and solid particles that might be present from the air as it
comes from the compressor or that may be carried over from the after cooler.
3. The receiver tank minimizes pulsation in the system caused by a reciprocating compressor or
a cyclic process downstream.
Much like a water reservoir provides water during times of drought and stores water during the
wet times, an air receiver tank compensates for peak demand and helps balance the supply of the
compressor with the demand of the system.
Receiver tanks are required by law to have a pressure relief valve and a pressure gauge. The relief
valve should be set to 10% higher than the working pressure of the system.
5.1.2 Motor
An electric motor is an electrical machine that converts electrical energy into mechanical energy.
The reverse of this would be the conversion of mechanical energy into electrical energy and is
done by an electric generator. In normal motoring mode, most electric motors operate through the
interaction between an electric motor's magnetic field and winding currents to generate force as
shown in figure 5.1 within the motor. In certain applications, such as in the transportation industry

49
with traction motors, electric motors can operate in both motoring and generating or braking modes
to also produce electrical energy from mechanical energy.
Figure 5.1 Motor
5.1.3 Reciprocating Single Acting Compressor
Reciprocating single acting compressors are generally of one-stage or two-stage design.
Compressors can be of a lubricated, non-lubricated or oil-less design. In the single-stage
compressor, air is drawn in from the atmosphere and compressed to final pressure .Single-stage
compressors are generally used for pressures of 70psi (pounds per square inch) to 150psi.
5.2 Pressure Gauge
The pressure gauge is used for the indication of pressure .it has a diaphragm in side to which the
needle is attached. Adjacent to the mechanical safety valve is the pressure gauge given below in
figure 4.2. This is a china made pressure gauge with gauge comes with an electronic switch. This
switch has a trigger alarm which gives a digital signal if the pressure reaches a certain limit. That
signal will be send to the automated control system later in the project a maximum display of 150
psi.

50
5.3 Solenoid Valves (ball valves)
Ball valves are a low torque quarter turn valve, with low resistance to flow, suitable for many on-
off utility and process services. They have a straight through configuration. They have a good
control characteristic (equal percentage), but is not generally used for throttling applications in
their standard form because of the potential for seat damage and cavitation (high pressure
recovery). Designs include floating ball and turn-on mounted ball types. Most designs are double
seated, but there are some special single seated designs e.g. eccentric ball (Orbit) types.
5.4 Turbine
A turbine is a rotary mechanical device that extracts energy from an air flow and converts it in to
useful work. A turbine is a turbo machine with at least one moving part called a rotor assembly,
which is a shaft or drum with blades attached. Compressed air acts on the blades so that they move
and impart rotational energy to the rotor. When the solenoid valve of the compressed air is open
then the compressed air through the stationary nozzle hits the blades and rotates the turbine. Due
to the air pressure the blades will move along his rotor. As the pressure of the air through nozzle
increase it will increase the rotation of the turbine. This turbine is fully synchronized with DC
Generator through Belt .As well as turbine moves the Generator will also with same speed. And
this Generator gives DC volts as an output is shown in figure 4.1.
5.5 12V DC Motor (Generator)
A DC motor used as a generator is a machine which convert mechanical energy in to Electrical
energy is shown in figure 5.2. Stepper motor can be used as an AC generator in the small level
projects. We use steeper motor as a generator and following are the main features of generator.
Features of generator are given below
 Nominal voltage: 12 V
 No load speed: 3990rpm

51
 No load current:14.6mA
 Nominal speed:2360rpm
 Nominal torque:12.6mNm
 Nominal current:0.240A
 Stall torque:31.9mNm
 Starting current:0.578A
 Maximum efficiency:70%
 Terminal resistance:41.5
 Terminal inductance:5.02mH
Figure 5.2 Diagram of DC motor
5.6 Control Circuitry
In a control circuitry we made a circuit which normally control the opening and closing of ball
valve with respect to the pressure in the thank. The major part of control circuitry is:
 Arduino UNO rev3(see the article 4.9)
 Power supply and some other parts(see the article 4.10)

52
5.6.1 Tacho Generator
An electromechanical generator is a device capable of producing electrical power from mechanical
energy, usually the turning of a shaft. When not connected to a load resistance, generators will
generate voltage roughly proportional to shaft speed. With precise construction and design,
generators can be built to produce very precise voltages for certain ranges of shaft speeds, thus
making them well-suited as measurement devices for shaft speed in mechanical equipment. A
generator specially designed and constructed for this use is called tachometer or tacho generator.
We are using simple DC Motor (0-9volt) as a Tacho Generator, which connected with the shaft of
turbine to measure the rotational speed of turbine and generate a voltage with respect to speed of
turbine. The output voltage of the Motor (using as a generator) is directly proportional to the speed
of turbine. The voltage of the tacho generator is send to Comparator IC then these voltages will
compare with reference voltage. If the voltage from tacho generator is less than the reference
voltage then a PWM is generated across these voltages and send to Microcontroller which signals
the valve to open more and draw more air pressure.
5.7 Hardware Layout
The final design is shown in figure .In this design a compressor system is shown which comprise
of tank, motor and a compressor. In our design air receiver tank is an integral and important part
of any compressed air system. Typically a receiver tank is sized at 6-10 times the flow rate of the
system. So, if a compressor has a rating of 25 scfm at 100 psig, the receiver tank should be 150
cubic feet, minimum. In our system the big advantage we have is an air power doesn’t need its
own bulky and heavy motor (normally 1.5kw motor is drive from solar system/wind turbine). The
compressor which we are using in our design is of reciprocating single acting compressor. In the
single-stage compressor, air is drawn in from the atmosphere and compressed to final pressure in
a single stroke. The single-stage reciprocating compressor is illustrated in article. Single-stage
compressors are generally used for pressures of 70psi (pounds per square inch) to 150psi.
A turbine is a rotary mechanical device that extracts energy from an air flow and converts it in to
useful work. A turbine is a turbo machine with at least one moving part called a rotor assembly,
which is a shaft or drum with blades attached. Compressed air acts on the blades so that they move

53
and impart rotational energy to the rotor. When the solenoid valve of the compressed air is open
then the compressed air through the stationary nozzle hits the blades and rotates the turbine. Due
to the air pressure the blades will move along his rotor. As the pressure of the air through nozzle
increase it will increase the rotation of the turbine. This turbine is fully synchronized with DC
Generator through Belt .As well as turbine moves the Generator will also with same speed. And
this Generator gives DC volts as an output.
A generator is a machine which convert mechanical energy in to Electrical energy. In our project
the DC motor is used as a AC generator.
Figure 5.3 Hardware layout 1
The output voltage of the DC motor (using as a generator) is directly proportional to the speed of
turbine. The generator voltage is send to the voltage divider circuit. Here the usage of voltage
divider circuit is to save the controller chip and then we send the analog voltage signal to the
Arduino UNO rev3 board. The Arduino board convert the analog signal into digital signal and also
generate the PWM which can send to the Microcontroller Atmega328. Then these voltages will
compare with reference voltage (5V). If the voltage from generator is less or more than the

54
reference voltage then a PWM is generated across these voltages and send to Microcontroller
which signals the Servo motor to move forward and backward and set the position of valve
according to the angle which is set by the programming in Arduino board. The opening and closing
of valve is increase and decrease the pressure of air which is send to our turbine blades and directly
proportional to the voltage generation.
Figure 5.4 Hardware layout 2

55
CHAPTER 6
RESULTS & DISCUSSION
MATLAB which is a high-level language and interactive environment for numerical
computation was used to create a model to analyses the SCAES system. A main goal was to
produce some correlation between the theoretical analysis and the data from the dyno. It was
found that the dyno results were substantially lower.
6.1 Theoretical Analysis
Isothermal and adiabatic equations are ‘ideal’ equations that are never actually achieved by
physical machines. An actual air compressor and motor will not achieve the values that these
formulae. Isothermal equation produces more specific energy then adiabatic equation. This is
due to the assumption that the air stays at constant temperature during expansion. This we know
to be untrue, as air drops in temperature during expansion which is evident after periods of
running an air tool they tend to be cold. To keep the temperature constant, energy must be added
and this is in the form of heat (adiabatic process). This heat energy is seen as work in expanding
the air which is why more energy’s gained from isothermal expansion. These were produced
using pressures, temperatures and volumes you would see on an off the shelf air compressor.
The pressure range was from 100kpa to a maximum 1000kpa of and a receiver volume of
0.065m^3. When using the ideal equations, knowledge of the specific gas constant for air needed
to be known which is 0.0287 kj/kg.
6.2 Practical Analysis
This was done to create a performance curves for each air motors when operated at different
torques for different pressures. It was found that the dyno results were substantially lower than
the theoretical results, as the theory does not take into account losses like compressor mechanical
and storage tank thermal losses, compressor and air motor thermodynamic efficiency, air motor
mechanical efficiency and friction and flow losses.

56
6.3 Total Energy Compressor Used to Fill Receiver
In order to calculate the results the total energy used in pumping up the receiver from empty to
full needed to be calculated. This was done using the time taken to fill the receiver and the electric
motors running current. The compressor was found to draw less current when the receiver
pressure was low and more current as the pressure increased. This is due to the compressor
having to overcome the receiver pressure on each stroke before any air enters the receiver.
Using MATLABs interpolation function a larger number of points could be produced given a
smoother plot over the whole time. The overall time which the compressor took to fill 0.056m3
the receiver was 120 seconds which worked out that the total energy which the compressor used
was 54.5Whr. This total energy will be used to calculate the efficiency of the system.
It is possible that this result could have been improved if the compressor was new. The
compressor used had been in service for 30 years on building sites to run various air tools like
drills and nail guns. The compressor had little maintenance done yet though the calculations seen
in Appendix the output 8.5cfm was which the name plate read 8.8Cfm.
6.4 Estimation on Size of Receiver for SCAES
Using the data collected in the dyne test and linear scaling, it was estimated 65000L that a
receiver with dimensions of that would be needed to store 3KWHR of energy. This amount of
stored energy will not be enough to supply an average household for one day as the average
consumption of energy is between 20-30kwhr. If this amount of energy was to be storage then
the receiver would have 65000L to be which is equivalent to a 25-metre swimming pool.
When considering this as a storage method, considerations need to be made on the safety aspects
of the system as the stored pressure could potentially have the effects of a bomb. Certification
for the receiver and relief values and restraining devices for pipework would all need to be
current and checked on a regular basis as if the receiver did fail the consequence could be very
high.

57
In addition to this the size would not be a feasible option due the area and size it would occupy
in a yard is shown in figure 6.1.
Figure 6.1 Size of energy storage
6.5 The Efficiency of a Compressed Air System
The overall efficiency of a compressed air system can be as low as (Markowitz, 2010). When
considering the efficiency of the system all the possible losses must be taken into consideration
which may occur from the moment a certain quantity of air enters the compressor until it is
exhausted from the air motor.
These losses are chargeable:
1. To air being taken into the compressor if it is being supplied from a hotter place. This results
in a lesser quantity (weight) of air being taken into the cylinder per stroke, thereby increasing
the power required to compress a given quantity of air per unit of time. This loss can be prevented
by making adequate provisions for the air in-take from the coolest outside place around the
compressor building.
2. To friction in the compressor. This will amount ordinarily to a power loss of from. It can be
reduced by good workmanship to about, but cannot be avoided altogether.

58
3. To a series of imperfections in the compressing cylinders, such as insufficient supply of free
air, difficult discharge, defective cooling arrangements, poor lubrication, etc.
4. To heat generated during compression which increases the power required for compressing a
given quantity of air, for which there is no return, as the heat is afterward dissipated in
transmission.
5. To loss of pressure in the pipe line, due to friction, etc.
6. To friction and fall of temperature during expansion of the air in the cylinder of the air engine.
7. To leaks in the compressor, the pipe line, and in the air engine (Simons, 1914).
From the literature review on the Huntorf and McIntosh plants it is said that the cycle efficiency
of the systems are and respectively. But theses efficiencies are based on the assumption of gas
used in a combined cycle gas turbine has a realistic efficiency. When looking at the input energy
and using the total electricity plus the total gas the efficiencies drop to and respectively. These
efficiencies are reasonable considering that these are sophisticated plants with the McIntosh plant
costing million dollars (Energy C., 2012).
The low efficiency which was calculated from the testing of even though is quite poor could be
improved with the use of new equipment or a change in design. It must be mentioned that all the
equipment used in the practical test had already been in service for many years.
The compressor was made years ago and over this time has had little to no maintenance to any
internal components of the compressor. If a new compressor was used then the input energy
could be lower which in-turn would improve overall efficiency.
6.6 Other Alternatives
In the project specification for this dissertation one of the outcomes was to investigate other
alternatives for a primary energy source or direct drive of the compressor, like using wind
turbine, solar thermal etc.
In the literature it was found that there was research conducted on using renewable energies for
the primary energy for CAES system which are known as Hybrid CAES (HCAES).

59
The traditional way of utilizing wind energy is for a turbine to drive a generator and produce
electricity which in turn would power an air compressor. When considering a direct drive
compressor using a wind turbine the air compressor and turbine need to be matched so that they
operate at the same speed range for all wind conditions which would be more involved than
generating electricity to power the air compressor. This also raises a point that if the wind turbine
was producing electricity then multiple compressors could be run whereas direct coupled on one
compressor could be used.
Another option would be to use hydraulics, which would be much more efficient then air but
does come with its own problems. Like the close fitting components in the pump which causes
much friction and requires a lot of force to turn the motor, or having the oil at the right
temperature. If the oil is cold this would increase the viscosity creating more friction. The last
consideration would be to the size of receiver required to store a reasonable amount of energy.
There is very limited information regarding solar thermal energy and compressed air. The
literature did reveal though that solar air-conditioning is considered as a thermal storage unit.
But it uses the thermal energy to preheat the refrigerant before it is directly feed into the
compressor. If this was to be considered to direct drive a compressor the energy would need to
be converted into form i.e. electricity, before it can be utilized to power a compressor. With this
conversion there would inherently be some losses.
When considering a pumped storage hydro as an energy system there are three main factors that
determine the generating potential at any specific site: the amount of water flow per time unit,
the vertical height that water can be made to fall (head) and the body of water used as storage.
Unlike wind and solar which are abundant in times of drought the volume of water storage will
decrease and evaporate leaving no water to use for energy to power the compressor. Like wind
turbines pumped storage hydro systems are typically connected to generators producing
electricity on demand to run equipment like air compressors.
With any of these other alternatives there is still an issue with the storage of compressed air and
the size of receiver required to store the amount of energy needed. This was very evident with
the SCAES system on which this dissertation is based. By using these other alternative energy
source this is not going to change the size of receiver but could improve the efficiency of the

60
system. More research would be required to investigate how these alternatives would behave if
the SCAES systems pressure was raised above, as with higher pressures the specific power and
energy from the compressed air is much greater and more air can compressed into a receiver.

61
CHAPTER 7
CONCLUSION & FURTHER RECOMMENDATION
7.1 Conclusion
The initial basis of this research was the assumption that compressed air could offer an
alternative to commercial energy storage technologies for house hold use. The focus was on off
the shelf products that could be combined in order to deliver the required energy storage and
delivery method. The overall efficiency of the SCAES system was very low and with further
research it would be possible to increase efficiencies of SCAES by improving. Compression and
decompression by using more effective isothermal processes
 Adding intermediate air receivers between pressures to increase the usable storage time
and helping more effective heat transfer to take place.
 Increasing the pressure above 1000kpa with larger compressor.
 Replacing air tool with air motors designed for this application.
 Recapturing the waste heat and using it in other areas.
 Heating the air on output of receiver to add more energy back into the compressed air.
7.2 Further Recommendation
The air compressor power plant is one of the promising renewable energy options to substitute the
increasing demand of conventional energy. A new strategy should be applied to reduce the
dependency of fossil fuel minimize the cost and enhance the efficiency of existing power plant by
means of hybridization with any renewable source. All the existing compressor power plants
should integrate with any renewable source. The most successful option is use of compressed air
and generation of air by means of renewable instead of using any kind of fossil fuel. By this process
the expenses will be goes very high because for this we to build a new plants. By this our
dependency of power plants on fossil fuel will be ended. Then we will be able to generate power
on less cost. In our project all of the valves can be automatically controlled, rpm can be controlled
using motor. Microcontrollers can be used to automatically handle the power plant.

62
REFERNCE
[1]Air Motors. (2012, 1 1). Retrieved 7 4, 2013, from Hydraulics and Pneumatics:
http://hydraulicspneumatics.com/200/TechZone/FluidPowerAcces/Article/False/6422/TechZone-
FluidPowerAcces
[2]Association, E. S. (2011). Electricity Storage Association. Retrieved 4 16, 2013, from
Technology http://www.electricitystorage.org/technology/tech_archive/technology_comparisons
[3]Australia, C. A. (2013). Air Nozzle Selection Guide. Retrieved 10 10, 2013, from Compressed
Air Australia: http://www.caasafety.com.au/air-nozzles-jets/air-nozzles
[4] Australia, G. (2011, 11 11). Geoscience Australia. Retrieved 5 1, 2013, from Energy:
http://www.ga.gov.au/energy/australian-energy-resource-assessment.html#
[5]Bossel, U. (2009). Thermodynamic Analysis of Compressed Air Vehicle Propulsion.
Switzerland.
[6] Challenge, C. A. (2003). Improving Compressed Air System Performance. Washington, DC:
Lawrence Berkeley National Laboratory.
[7] Connolly, D. (2010, 10 11). A review of energy storage technologies for the integration of
fluctuating renewable energy. Limerick, Limerick, Ireland: University of Limerick
.
[8]Consulting, M. H. (2012). Energy Storage in Australia. Brisbane: Marchment Hill Consulting.
[9] Cunha, I. F. (2012, 12 18). Sustainability Victoria. Retrieved 8 23, 2013, from Sustainability
Victoria: www.sustainability.vic.gov.au/.../best_practice_guide_compressed_air.pdf
[10]Das, T., & McCalley, J. D. (2012). Compressed Air Energy Storage. Iowa: Iowa State
University.

63
[11]Energex. (n.d.). Saving energy during peak times. Retrieved 7 24, 2013, from Energex Positve
Energy: http://www.energex.com.au/residential-and-business/peak-demand
[12]Energy, C. (2012). Huntorf Compressed Air Energy Storage Facility. Retrieved 2 2, 2013,
from Clean EnergyAction Project:
http://www.cleanenergyactionproject.com/CleanEnergyActionProject/Energy_Storage_Case_Stu
dies.html
[13]Energy, C. (2012). MacIntosh Compressed Air Energy Storage Plant. Retrieved 2 2, 2013,
from Clean Energy Action Projet:
http://www.cleanenergyactionproject.com/CleanEnergyActionProject/Energy_Storage_Case_Stu
dies.html
[14]H Paloheimo, M. O. (2009). A Feasibility Study on Compressed Air Energy Storage System
for Portable Electrical and Electronic Devices. Clean Electrical Power, 355 - 362.
[15]Harrison, P. J. (n.d.). Michigan State University. Retrieved 4 14, 2013, from Department of
Chemistry: http://www.chemistry.msu.edu/
[16]Hepworth, A. (2011). Rooftop solar panels overloading electricity grid. Sydney: The
Australian.
[17]Institute, S. S.-m. (2010). Analysis of compressed air storage. Lithuania: Strategic Self-
management Institute.
[18]International, F. D. (2010). Australia's Energy Future - A Time for Reflection. Perth: Future
Directions International.

64
Appendix-A Basic Definition
Absolute Pressure
Total pressure measured from zero. Gauge pressure plus atmospheric pressure. For example, at
sea level, the gauge pressure in pounds per square inch (psi) plus 14.7 gives the absolute pressure
in pounds per square inch (psi).
Absolute Temperature
See Temperature, Absolute.
Absorption
The chemical process by which a hygroscopic desiccant, having a high affinity with water, melts
and becomes a liquid by absorbing the condensed moisture.
Actual Capacity
Quantity of air or gas actually compressed and delivered to the discharge system at rated speed
and under rated conditions. It is usually expressed in cubic feet per minute (acfm) at compressor
inlet conditions. Also called Free Air Delivered (FAD).
Adiabatic Compression
See Compression, Adiabatic.
Adsorption
The process by which a desiccant with a highly porous surface attracts and removes the moisture
from compressed air. The desiccant is capable of being regenerated.
After cooler
A heat exchanger used for cooling air discharged from a compressor. Resulting condensate may

65
be removed by a moisture separator following the after cooler.
CFM, Free Air
Cubic feet per minute of air delivered to a certain point at a certain condition, converted back to
ambient conditions.
CFM, Standard
Flow of free air measured and converted to a standard set of conditions of pressure, temperature
and relative humidity.
Compressed Air
Air from atmosphere which has been reduced in volume, raising its pressure. It then is capable of
performing work when it is released and allowed to expand to its normal free state as it passes
through a pneumatic tool or other device.
Compression Adiabatic
Compression in which no heat is transferred to or from the gas during the compression process.
Compression Isothermal
Compression is which the temperature of the gas remains constant.
Degree of Intercooling
The difference in air or gas temperature between the outlet of the intercooler and the inlet of the
compressor.
Demand
Flow of air at specific conditions required at a point or by the overall facility.

66
Diaphragm
A stationary element between the stages of a multi-stage centrifugal compressor. It may include
guide vanes for directing the flowing medium to the impeller of the succeeding stage. In
conjunction with an adjacent diaphragm, it forms the diffuser surrounding the impeller.
Discharge Pressure
Air pressure produced at a particular point in the system under specific conditions.
Discharge Temperature
The temperature at the discharge flange of the compressor.
Displacement
The volume swept out by the piston or rotor(s) per unit of time, normally expressed in cubic feet
per minute.
Efficiency
Any reference to efficiency must be accompanied by a qualifying statement which identifies the
efficiency under consideration, as in the following definitions of efficiency.
Compression
Ratio of theoretical power to power actually imparted to the air or gas delivered by the compressor.
Efficiency Isothermal
Ratio of the theoretical work (as calculated on a isothermal basis) to the actual work transferred to
a gas during compression. Efficiency,
Mechanical
Ratio of power imparted to the air or gas to brake horsepower (bhp). Efficiency,

67
Polytrophic
Ratio of the polytrophic compression energy transferred to the gas, to the actual energy transferred
to the gas. Efficiency,
Volumetric
Ratio of actual capacity to piston displacement.
Exhauster
A term sometimes applied to a compressor in which the inlet pressure is less than atmospheric
pressure.
Filters
Devices for separating and removing particulate matter, moisture or entrained lubricant from air.
Gauge Pressure
The pressure determined by most instruments and gauges, usually expressed in psig. Barometric
pressure must be considered to obtain true or absolute pressure.

69
Appendix-C Storage Technology
The relationship between storage technology and power rating
Comparison of Storage Technology

70
Appendix-D Ideal Thermodynamics Calculations
Isothermal compressed energy storage
Variables
 Compressed air pressure = 100kpa
 Temperature in K = 20 +273 = 293 K
Free energy in this case is given by:

73
Appendix-E Evaluating True CFM Rating of an Air compressor

74
Appendix-F Comparison of Battery and Compressor
Difference
Comparison

75
Appendix-G Automation of Motor Control Coding
// include the library code:
#include <LiquidCrystal.h>
#include <Servo.h>
Servo myservo; // create servo object to control a servo
int volt = 0;
// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
int pos = 125; // variable to store the servo position
void setup() {
myservo.attach(9); // attaches the servo on pin 9 to the servo object
Serial.begin(9600);
// set up the LCD's number of columns and rows:
lcd.begin(16, 4);
// Print a message to the LCD.
lcd.setCursor(0,0);
lcd.print("Batt Replacement");
lcd.setCursor(0,1);
lcd.print("with Compressed");
lcd.setCursor(4,2);
lcd.print("Air Tank");

76
// lcd.print("Air Tank Project");
// lcd.print("Battery Replacement with Compressed Air Tank Project");
delay(1000);
lcd.clear();
}
const int sensorPin = A0;
int sensorValue = 0;
void loop() {
sensorValue = analogRead(sensorPin);
// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 0);
// print the number of seconds since reset:
lcd.print("INPUT = ");
lcd.print(sensorValue);
volt = sensorValue/63;
lcd.setCursor(0,2);
lcd.print("Volt = ");
lcd.print(volt);

77
if (volt > 3){
pos = pos + 8;
}
if (volt < 3){
pos = pos - 8;
}
if (pos > 125){pos = 125;}
if (pos < 40){pos = 40;}
myservo.write(pos);
lcd.setCursor(0,1);
lcd.print ("angle = ");
lcd.print(pos);
lcd.print(" ");
delay(500);
// lcd.clear();
}

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