DOCTOR OF PHILOSOPHY
PROPOSAL
CHARACTERISATION AND EFFECTIVENESS OF THERMAL
CONSERVATION STORAGE INTEGRATION IN VARIABLE
HEAT SCHEME FOR STABILITY ENERGY DELIVERY TO
GREEN THERMAL PROCESSES
BY
NG KHAI MUN
MECHANICAL ENGINEERING
FACULTY OF ENGINEERING
UNIVERSITI PUTRA MALAYSIA
SEM II 2012/2013
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Proposed Research Title: Thermal Storage and Management Programme
Characterisation and Effectiveness of Thermal Conservation Storage Integration in
Variable Heat Scheme for Stability Energy Delivery to Green Thermal Processes
Research background including Hypothesis /Research Questions and Literature
Reviews (Assume the energy supply is solar, however waste heat can be the input as alternative)
Subject of sustainable energy has been raised since half century ago. Until today
green energy concept still serves a direction of research and development for better
future. Renewable energy harnessing methods are undergoing development and some
have been realised in real applications, such as solar, geothermal, wind and tidal
based technologies. Nevertheless of all the advancement of the systems, the
uncontrolled variables of energy sources have made the systems ineluctably facing
intermittent behaviour in their performance following the nature trends. It may lead
to a mismatch between the energy demand and supply. These drawbacks have
attracted attention from researchers to figure out solutions to optimise the
conservation of renewable based technology. As for our country, the sky shows a
high frequency of raining rate and cloudy occurrences throughout the year. As
mentioned, the irregular nature of solar energy source may interrupt the thermal heat
source for a system. Although solar insolution on the ground is promising in general,
the temporary blockage of the energy source has inherently placed the solar
technology in a paradox status.
The concept of energy storage, which is known to be the solution, has been a topic of
discussion addressing the issue. Thermal storage system could function as an energy
reservoir to buffer and supply energy in thermal form that can perform continuously
with better prediction of heat management. Looking into the current solar collector
technology employed in the country, high concentrating solar collector is seldom
used in the field. Most of the systems are using flat plat collector and evacuated tube
collector that have been employed in many ways for heating and cooling purposes.
Those collectors mean for the low and medium heat collections that lead to a limited
range of heat supply. It could be a topic of interest if high amount of energy content
is stored in constant and stable heat content, such as latent thermal storage. While
most of the processes use sensible thermal storage with water as common medium,
the current emergence of latent heat concept has provided an insight for the possible
improvement of the thermal supply methodology. In the latent heat storage, the
scheme of storing thermal energy using phase change material (PCM) can provide a
greater energy density under a specific temperature range which is more constant
than the sensible way. Larger amount of heat can be stored under a lower
temperature range for less thermal loss and it is expected that the efficiency of
collector could be improved. The fluctuation of heat transfer contributes to the
instability of heat content has increased entropy and added difficulty in heat
management. It has showed that a control strategy should be investigated and
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optimised after knowing the behaviour of a system to achieve a high efficiency. The
stable heat supply is important for system operation and latent heat storage is one of
the solutions. Besides, a storage tank design, specifically for PCM could be proposed
after knowing the behavior of the storage medium. Presently, the storage tank with
cylinder shape is used in common prescriptively without considering the other
potential configurations of tank that may possibly enhance the storage strategic.
To the best knowledge of the author, there is lack of information concerning the
potential of solar thermal storage systems (TES) operated under hot tropical climates.
The choice of a TES system would be suspected if there is no data or evidence about
the characterisation of a solar based TES operated in nation. Although applications
and experiments of some solar energy systems integrating TES have been
demonstrated, the studies were carried out for different systems without specifically
focusing on the effectiveness of the TES itself. The knowledge of the use of TES
under different schemes of thermal heat is limited. The unstable solar heat input may
influence the effectiveness of the heat stored in different heat schemes, which is
difficult to be justified by a single system. For all the stated reasons, therefore an
investigation on the TES should be highlighted to provide information to the public
and industries about its characteristics and effectiveness in variables heat schemes to
minimise the risk of investment and concurrently broader the use of renewable
thermal energy source.
In Malaysia, researches have been working on various applications of solar thermal
in building heating and cooling, drying of agricultural products and other areas that
can potentially benefit from this free energy source. Several studies of using TES
have been conducted to optimise heat management strategies. The development of
storage system can encourage the usage of renewable energy in accordance with the
government policy. It is expected that the adoption of PCM in TES should be able to
magnetise the parties who concern about the stable temperature control in green
thermal energy systems for long time.
Objective of the Research
In general, the proposal intends to achieve the following objectives:
(i)
To identify suitable phase change material (PCM) that could potentially be
integrated with solar collector under different heat scheme.
(ii)
To investigate the internal thermal behaviour, enthalpy, entropy and exergy
of the PCM thermal storage under the continuous mode for different heat
scheme.
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(iii) To investigate control strategies of PCM storage system that could optimise
the system through an analysis of stable energy supply in continuous mode.
(iv) To investigate an approach to enhance the thermal storage by configuring
the design of an energy storage tank.
(v)
To investigate the characterisation and effectiveness of a PCM storage
system under hot tropical climate using simulation methodology and labscale experiments.
(vi) To develop an expert systems and simulation tool to predict the
effectiveness of using PCM storage system that is compatible with the
nation weather condition.
Question to be answered:
(i)
What are the PCM materials could be employed to suit the thermal heat
provided by commercial solar collectors?
(ii)
What are the thermodynamics properties of a PCM thermal storage for
different heat scheme? Is there any relation among those properties?
(iii) What could be the effect on the efficiency of the collector under those
schemes?
(iv) What is the amount of heat can be collected and stored in daily basis then
monthly basis for different scheme of heat. Temperature of excess heat if
any?
(v)
How does the stability of the systems and its operation time can be achieved?
If control mechanism is to be responsible, how does it perform?
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(vi) Does the heat from the storage capable to provide long term heat supply to a
thermal system? If it can, then how long? How does the behaviour and
amount of heat consumption by the system affect the storage mechanism?
(vii) Is there any possibility of changing the configuration of storage tank to
enhance the thermal storage?
(viii) To what extend the storage system can solve the intermittent issue by
renewable source under hot tropical climate?
Expected Results/Benefit
The expected outcomes of the project:
(i)
Intends to introduce PCM with medium temperature ranging from 40 - 120
o
C in the integration of heat sources. It needs to be developed and
characterised to integrate with commercial collector. Material of low cost,
high latent heat of fusion, high heat transfer and stable should be selected.
(ii)
Intends to generate new knowledge on the application of PCM integrated
with commercial solar collectors for different heat scheme that could
potentially beneficial to thermal process systems and wider the market.
Generation of a deeper theoretical understanding.
(iii) Intends to present a finding in the use of PCM storage system operated
under local environment that serves as information to the public and
industries about its characteristic and effectiveness.
(iv) Intends to propose a storage tank design for PCM subjected to evaluation.
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(v)
Verifies the introduction of PCM thermal reservoir in improving the thermal
process systems.
(vi) Prepare evaluation report of the systems in energy efficiency, economics,
CO2 mitigation and potential markets if any.
(vii) Intends to develop a simulation tool to predict the effectiveness of using
PCM storage system. The tool might be useful for real case study of pilot or
industrial scale.
(viii) The knowledge does not limited to the renewable heat sources, but possibly
extended to standard thermal processes in surplus heat recovery such as
domestic and industry refuses, power plant, furnace sector and vehicles.
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Solar
(Renewable energy source)
(Under Malaysian Tropics)
PCM thermal
storage tank
Flat plat and
evacuated tube
Waster heat
Investigate the characterisation
and effectiveness of the PCM
storage integration for different
heat scheme, which is defined
within the temperature limit by
collectors.
Green Thermal
Process Systems
*
Industrial processes
(Surplus energy source)
(Standard industrial operation)
Figure 1 General concept of the proposal
* Note: Choose only one input method for the current project. Depends on the resources, it has to be
practicable and achievable in conducting an experiment.
GENERAL CONTENTS
CHAPTER
1
2
INTRODUCTION
1.1
Potential of Thermal Energy Storage Technologies
1.2
Current Status of Latent Heat Storage Systems
1.3
Problem Statement
1.4
Objectives
1.5
Scope and Limitation
1.6
Thesis Layout
LITERATURE REVIEW
2.1
Thermal Energy Storages
2.1.1 Sensible Heat Storage
2.1.1.1 Overview
2.1.1.2 Storage Media
2.1.1.3 Process Integration
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2.1.2
2.2
2.3
2.4
2.5
Latent Heat Storage
2.1.2.1 Overview
2.1.2.2 Storage Media
2.1.2.3 Process Integration
2.1.3 Thermo Chemical Heat Storage
2.1.3.1 Overview
2.1.3.2 Storage Media
2.1.3.3 Process Integration
Solar Thermal Collectors
2.2.1 Flat Plate Collector
2.2.2 Evacuated Tube Collector
2.2.3 Compound Parabolic Collector
2.2.4 Parabolic Trough
2.2.5 Parabolic Dish Engine
2.2.6 Central Receiver Tower
Phase Change Materials
2.3.1 PCM for Low Heat Scheme
2.3.2 PCM for Medium Heat Scheme
2.3.3 Material Properties
2.3.3.1 Thermo-Physical Properties
2.3.3.2 Kinetic Properties
2.3.3.3 Chemical Properties
2.3.4 Material Classification
2.3.4.1 Organic Materials
2.3.4.2 Inorganic Materials
2.3.4.3 Eutectics
2.3.5 Cost/ Economics
2.3.6 Commercial Products
2.3.7 Advantages and Disadvantages
2.3.8 Summary
Application of Latent Heat Storage Systems
Integrated Solar Collector for Low and Medium Heat Schemes
2.4.1 Water Heating Systems
2.4.2 Air Heating Systems
2.4.3 Green House
2.4.4 Heat pump
2.4.5 Drying food product
2.4.6 Cooling Systems – Refrigeration
2.4.7 Cookers
2.4.8 Power Generation (actually not recommended by
RShinnar ARPA pg 13)
2.4.9 Commercial Products
Storage Tanks
2.5.1 Tank Materials
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2.6
2.7
2.8
2.9
2.10
3
2.5.1.1 Steel
2.5.1.2 Concrete
2.5.1.3 Plastic
2.5.2 Tank Arrangement Schemes
2.5.2.1 Stratified Storage
2.5.2.2 Parallel Storage
2.5.2.3 Single Tank Thermocline
2.5.2.4 Two-Tank Direct
2.5.2.5 Two-Tank Indirect
2.5.3 Thermal Heat Losses from Tank
2.5.4 Sizing of Tanks
Heat Transfer In Latent Heat Thermal Energy Storage Systems
2.6.1 Types of Heat Transfer
2.6.2 Enhancement Techniques
2.6.2.1 Nanoparticle
2.6.2.2 Enhancement using high conductive
materials
2.6.2.3 Enhancement using extended heat transfer
surface
2.6.2.4 Enhancement using intermediate heat transfer
medium
2.6.2.5 Enhancement using heat pipes
2.6.2.6 Enhancement using multiple PCMs
2.6.2.7 Finned embedded enhancement technique
2.6.2.8 Metal insertion enhancement technique
2.6.2.9 Multi PCMs enhancement technique
2.6.2.10 Multi tubes enhancement technique
Arrangement, Control and Operating Strategies of Latent
Thermal Storage Systems
2.7.1 Direct Storage Systems
2.7.2 Indirect Storage Systems
Computational Numerical Modelling
Solar Irradiation in Malaysia
Closure
METHODOLOGY
Simulation:
Simulation software must be identified first. It is recommended to use CFD. If no
choice, then maybe can use Matlab, but then a full understanding on the formulae
and assumptions is a must for comprehensive programme coding.
Looking for all the formulae:
(1) Thermodynamic Model of Latent Heat Storage Systems – include internal
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(2)
(3)
(4)
(5)
(6)
(7)
(8)
physical characteristics
Thermodynamic Model of Collectors with solar radiation input. It is believe
that the model is quite comprehensive, just need to suit it to the local
environment that is believed existing already. Or use my own results on
radiation.
Energy Formulation
Enthalpy Formulation
Exergy Formulation
Heat Transfer Model: Charge and Discharge Models
Mathematical models for heat transfer enhancement
Mathematic Model for Collector–Storage Integration Performance (Model/
Knowledge that may need self-developed)
(9) Heat control/ mechanism simulation
(10) Tank configurations
Experiment:
All must consistent with the simulation. It should be designed referring to the
input and output parameters by simulation. Thus, a full set of expected results or
graphs should be identified before this.
(1) Define a range of temperature needed for an output: 40 – 100 oC depends on
capacity of collector; then the tests are conducted for several range of
temperatures desired for any particular application, say 10 oC interval; 40 –
50, 50 – 60, 60 – 70, 70 – 80, 80 – 90 and 90 – 100. The temperature depends
on the availability of the PCM materials for those ranges of temperature.
(Proposal: No system at the output is required, just discharge the constant heat
to atmosphere, it only can be done through proper control. Problems are: how
about the input temperature? How about the pressure? How about the flow
rate to supply heat? All those parameters require a system to answer. Maybe
check on certain or fix the applications first on what are the usual values
needed. Maybe find a normalise value for all the parameters. Maybe getting
external devices to control the parameters.)
It has to be simple and can address its necessary to be set that way and precise
in the measurement. Again, it must consistent to the simulation and can give
me the answer that I question.
(2) List all the materials and measuring devices needed for the experiment as well
as the installation and setting. Draft budget.
(3) Set the time and day for the test. Since it is dealing with the actual test
environment, then outdoor test are needed. So it may need to be tested for 6
months for sufficient data to be analysed. The problem is, if the test involved
several range of temperature with several PCM tank, then how? Many set of
tanks are needed by then. Maybe use only one evacuated tube; and it is
connected to all the tested PCM tank; all are conducted under the same set of
input parameter and measuring devices; but the control mechanism might be
different referring to the optimised setting recommended by simulation.
(It is reminded that the purpose of having test is to check whether the
simulation results can be trusted, and if experiment for the specific
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temperature cannot be done because of no funding, then maybe check the
results by referring to the literature data, or check with existing projects that
run the PCM project as well to work with them, but the projects should run
under tropical sun as pre-requisite)[Considering this point, it is better to
propose a system to work with, rather than various heat scheme; but again,
with no funding it can be very difficult]
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