Project 2 Thermal modeling of battery pack

AIM:

• For a 10 cell series lithium-ion battery model, simulate the thermal effects and compare life cycle performance at various temperatures, charge & discharge rates using MATLAB

OBJECTIVES:

• Explain the requirements as in detail
• Design a simulink model with the blocks of specified parameters
• Ensure with the inputs were going to feed
• Give a proper explanation about the deigned model
• Make sure that output will be the good resultant

1. FOR A 10-CELL SERIES LITHIUM-ION BATTERY MODEL, SIMULATE THE THERMAL EFFECTS AND COMPARE LIFE CYCLE PERFORMANCE AT VARIOUS TEMPERATURES, CHARGE & DISCHARGE RATES USING MATLAB

Following will gives the detailed information about the specified battery's working and operations and it's designed model through simulink,

LITHIUM-ION BATTERY:

• Lithium-ion batteries are one of the most widely used types of rechargeable battery, and their dominance continues to grow year-over-year. Here's a brief overview of a technology that has transcended generations in technology
• In the 1970s, a team of research scientists began working on what would become the lithium-ion (Li-ion) battery, a type of rechargeable battery that would one day power pretty much everything
• From portable electronics to electric vehicles, it's a technology that has well and truly shaped the electronics industry and our world
• Since 2020, three scientists behind the battery technology - John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino - were awarded the Nobel Prize in Chemistry for their work in developing it
• According to the Nobel Foundation, 'this lightweight, rechargeable and powerful battery' is now used in everything from mobile phones to laptops and electric vehicles
• It can also store the significant amounts of energy from the solar and wind power, making possible a fossil fuel-free society
• Despite being over four decades old, interest in Li-ion technology and its use in electronics applications continues to grow
• Recent estimations say that the market will grow at a compound annual growth rate (CAGR) of 18.16 percent and reach a value of $61.14 billion by 2023, up from $31.36 billion in 2019

Early Li-ion Battery Development:

Whittingham's first Li-ion battery

• In the early 1970s, Whittingham, who at the time was a chemist at Exxon, started exploring the idea of a new battery that could recharge on its own in a short amount of time: a Li-ion battery
• While his first attempt worked, it was based on a metallic lithium anode which was found to chemically react with the electrolyte, leading to instability and the growth of lithium 'whiskers' (i.e., dendrites) that could cause the battery to explode

Goodenough's improved Li-ion battery design

• Then in the 1980s, Goodenough, who was an engineering professor at the University of Texas at Austin at the time, had a different idea
• He experimented using lithium cobalt oxide as the cathode instead of titanium disulfide. This doubled the battery's energy potential from 2 V to 4 V

Yoshino's final design

• Finally, six years later (2016), Yoshino, who was working at Asahi Kasei Corporation, developed the use of graphite for the anode
• Initially, petroleum coke was used, but graphite was found to be a far better material. The Li-ion intercalated into the layered graphite, providing a huge boost as no free metallic lithium is used in the battery
• This made the battery far safer and enabled the first prototype Li-ion battery to be produced

• Together, these three developments led to the Li-ion battery as we know it today. In 1991, the Li-ion battery was commercialized by Sony and Asahi Kasei Corporation, with Samsung SDI beginning the manufacture of Li-ion batteries at their Cheonan, Korea plant in 2000

Moreover,

• By 2050, lithium ion-based batteries will be the least expensive way to store energy from power generation like solar or wind farms, according to a new study by researchers at the Imperial College of London
• The new research determines the cost of storing energy with various technologies, such as pumped-storage hydroelectricity and large-scale batteries, and forecasts those costs into the future
• Based on these predictions, lithium-ion-based battery technologies are expected to be the most economical way of storing energy for the majority of applications, including ensuring that energy grids do not suffer large fluctuations and letting consumers manage the bills
• These applications are especially critical for energy sources that may be intermittent including solar power or wind
• The new study, published in "Joule", could help industry and policymakers choose where to invest in research and industry to make the best use of energy storage technologies
• While previous studies of energy storage cost mainly focused on the investment costs, the new study determines the 'levelized cost of storage', which includes the full costs of storing energy with the investment, operation, and charging expenses, as well as the efficiency, the technology lifetime, and performance degradation
• "Our model is the first to project full energy storage costs into the future, allowing predictions of which technology will be most competitive in a particular application at a particular time," said lead researcher Oliver Schmidt, from the 'Grantham Institute and the Centre for Environmental Policy' at Imperial College
• The model reveals that presently, the "cheapest energy storage method" is pumped-storage hydroelectricity, where spare energy is used to pump water to a higher elevation
• It is then released to collect the energy when demanded. However, the study suggests that as time progresses, pumped-storage hydroelectricity costs do not decline, whereas lithium-ion battery costs drop, making them the cheapest options for most applications from 2030, according to the study
• 'Flywheel' and 'Hydrogen storage' technologies also become the least expensive for particular applications, including when the stored energy has to be released over a long time period, or when it must be discharged very frequently
• Despite this, lithium-ion technologies were found to be the cheapest for the bulk of applications
• Schmidt explained, "Our projections show that lithium-ion technologies will see a rapid decline in costs over the next couple of decades
• This is driven mainly by the fact that lithium-ion is manufactured at scale. The resulting reduction in initial investment costs is more significant than for other newer technologies such as flow batteries and flywheels, potentially outcompeting any performance advantages of these newer technologies"

And also,

• Economics of Lithium-Ion Battery Technology has Same Pattern as Crystalline Silicon Solar Panels - Dr. Iain Staffell, senior author on the article from the Center from Environmental Policy, said, "We have found that lithium-ion batteries are following in the footsteps of crystalline silicon solar panels
• First-generation solar cells were high performance but very expensive, so cheaper second and third generation designs were developed to supersede them
• However, sheer economies of scale mean these first-generation panels now cannot be beaten on price
• "Similarly, lithium-ion batteries were once expensive and only suited to niche applications, but they are now being manufactured in such volumes that their costs are coming down much faster than the competing storage technologies"
• Schmidt added, "This doesn't mean that these other technologies should be abandoned, but they have to perhaps focus on performance and efficiency, making them the best they can be before being deployed at a larger scale"
• The team made their model open access, which lets academics, consumers, as well as industry, and policymakers run their own simulations with the data for particular applications

Lithium-ion Batteries in EV:

• Lithium-ion batteries are the energy storage systems were used in HEVs, PHEVs, and EVs. It's currently used in most portable consumer electronics such as cell phones and laptops because of their high energy per unit mass relative to other electrical energy storage systems
• They also have a high power-to-weight ratio, high energy efficiency, good high-temperature performance, and low self-discharge
• Most components of lithium-ion batteries can be recycled, but the cost of material recovery remains a challenge for the industry
• The U.S. Department of Energy is also supporting the Lithium-Ion battery recycling prize to identify solutions for collecting, sorting, storing and transporting spent and discarded lithium-ion batteries for eventual recycling and materials recovery
• Most of today's PHEVs and EVs use lithium-ion batteries, though the exact chemistry often varies from that of consumer electronics batteries
• Research and development are ongoing to reduce their relatively high cost, extend their useful life and address safety concerns in regard to overheating

Working of Lithium-ion Batteries:

• Like any other battery, a rechargeable lithium-ion battery is made of one or more power-generating compartments called cells
• Each cell has essentially three components: a positive electrode (connected to the battery's positive or +ve terminal), a negative electrode (connected to the negative or -ve terminal) and a chemical called an electrolyte in between them
• The positive electrode is typically made from a chemical compound called lithium-cobalt oxide (LiCoO2) or in newer batteries, from lithium iron phosphate (LiFePO4)
• The negative electrode is generally made from carbon (graphite) and the electrolyte varies from one type of battery to another - but isn't too important in understanding the basic idea of how the battery works
• All lithium-ion batteries work in broadly the same way. When the battery is charging up, the lithium-cobalt oxide, positive electrode gives up some of its lithium ions, which move through the electrolyte to the negative, graphite electrode and remain there
• The battery takes in and stores energy during this process. When the battery is discharging, the lithium-ions move back across the electrolyte to the positive electrode, producing the energy that powers the battery
• In both cases, electrons flow in the opposite direction to the ions around the outer circuit. Electrons do not flow through the electrolyte: it's effectively an insulating barrier, so far as electrons are concerned
• The movement of ions (through the electrolyte) and electrons (around the external circuit, in the opposite direction) are interconnected processes, and if either stops so does the other
• If ions stop moving through the electrolyte because the battery completely discharges, electrons can't move through the outer circuit either - so you lose your power
• Similarly, if you switch off whatever the battery is powering, the flow of electrons stops and so does the flow of ions
• The battery essentially stops discharging at a high rate (but it does keep on discharging, at a very slow rate, even with the appliance disconnected)
• Unlike simpler batteries, lithium-ion ones have built in electronic controllers that regulate how they charge and discharge
• They prevent the overcharging and overheating that can cause lithium-ion batteries to explode in some circumstances

Advantages of Lithium-ion Batteries:

• Compared to the other high-quality rechargeable battery technologies (nickel-cadmium or nickel-metal-hydride), Li-ion batteries have a number of advantages
• They have one of the highest energy densities of any battery technology today (100-265 Wh/kg or 250-670 Wh/L)
• In addition, Li-ion battery cells can deliver up to 3.6 Volts, 3 times higher than technologies such as Ni-Cd or Ni-MH
• This means that they can deliver large amounts of current for high-power applications, which has Li-ion batteries are also comparatively low maintenance, and do not require scheduled cycling to maintain their battery life
• Generally, lithium ion batteries are more reliable than older technologies such as nickel-cadmium (NiCd, pronounced "nicad") and don't suffer from a problem known as the "memory effect" (where nicad batteries appear to become harder to charge unless they're discharged fully first)

• Since lithium-ion batteries don't contain cadmium (a toxic, heavy metal), they are also (in theory, at least) better for the environment, although dumping any batteries (full of metals, plastics, and other assorted chemicals) into landfills is never a good thing
• Compared to heavy-duty rechargeable batteries (such as the lead-acid ones used to start cars), lithium-ion batteries are relatively light for the amount of energy they store

Disadvantages of Lithium-ion Batteries:

• As a power source for automobiles, we really need to compare them not with other types of batteries but with gasoline
• Despite considerable advances over the years, kilo for kilo, rechargeable batteries still store only a fraction as much energy as ordinary gas
• In more scientific words, they have a much lower energy density (they store less energy per unit of weight). That also explains why you can fully "recharge" (refuel) a gas-powered automobile in a couple of minutes
• Whereas it'll generally take you hours to recharge the batteries in an electric car. Then again, you have to bear in mind that these disadvantages are balanced by other advantages
• Such as the greater fuel economy of electric cars and their relative lack of air pollution (zero tailpipe/exhaust emissions from the vehicle itself)
• Li-ion batteries have a tendency to overheat, and can be damaged at high voltages. In some cases this can lead to thermal runaway and combustion
• This has caused significant problems, notably the grounding of the "Boeing 787" fleet after onboard battery fires were reported
• Because of the risks associated with these batteries, a number of shipping companies refuse to perform bulk shipments of batteries by plane

Series Lithium-ion Battery Model:

• When the positive terminal of one battery is connected with the negative terminal of the second battery, the battery is considered to be connected in a series connection
• In the case of a series connection, the total voltage of the battery is increased and is given by the sum of the voltage of all the batteries connected in series

SIMULINK MODEL: [Runtime - 3600 secs]

Note:The above workout file has attached below for the reference

EXPLANATION:

Following are the blocks were used to designed the above simulink model of 10-cell series connection of battery pack,

1. Lithium Battery (masked)

• The masked lithium cell blocks represents an ideal lithium-ion cell used in a battery pack along with thermal ports
• Connections '+'ve and '-'ve are electrical conserving ports through which the cells are inserted into the circuit. The Thermal port used for further thermal network connections

Cell Parameters: 01-04; 05; 06-10

Main Input

Electrical

Thermal

Table Breakpoints

• Above are the inputs for the each cell's electrical and thermal parameters were feed from the matlab workspace. Those inputs were shown below

• Now let's discuss about the subsystem of masked(inside) lithium cell blocks and it's parameters

• Inside the mask, it contains the thermal model subsystem and lithium cell 1RC block which helps to calculate the battery's temperature and thermal effect
• Voltage sensor: This block represents an ideal voltage sensor, that is a device that converts voltage measured between any electrical connections into a physical signal proportional to the voltage
• Controlled voltage source: This block represents an ideal voltage source that is powerful enough to maintain the specified voltage at its output regardless of the current flowing through the source
• PS gain: This block performs element-wise multiplication of the input physical signal by a constant value (gain). You specify the gain as the Gain parameter value and unit

• Inside of thermal model, it contains the ambient temperature of controlled heat flow rate source block, temperature sensor to sense the rate of temperature and battery thermal mass block

• Inside of lithium cell 1RC has consists of capacitance value table which depends on an external physical signal inputs SOC and T
• It is assumed that the capacitance value is slowly varying with time, and hence the equation i = C*dv/dt holds
• Resistance value (R) table which depends on an external physical signal inputs SOC and T
• Voltage value (EM) which implements the cell's main branch voltage source, and determines values for capacity (C) and state of charge (SOC). The defining equations depend on cell temperature, T

• Em_table: This block implements the cell's main branch voltage source, and determines values for capacity (C) and state of charge (SOC). The defining equations depend on cell temperature, T
• C1_table: Models a capacitor where the capacitance value (C) depends on an external physical signal inputs SOC and T. It is assumed that the capacitance value is slowly varying with time, and hence the equation i = C*dv/dt holds
• R1_table: Models a resistor where the resistance value (R) depends on an external physical signal inputs SOC and T
• R0_table: Models a resistor where the resistance value (R) depends on an external physical signal inputs SOC and T

• Following will shows the each assigned excel variables of the cell's resistance and capacitance values as follows from the workspace

Em_LUT

C1_LUT

R1_LUT

R0_LUT

• Temperature reading - This subsystem helps to get the reading of each cell's temperature while charging and discharging as respectively

2. Conductive Heat Transfer

• The Conductive Heat Transfer block represents a heat transfer by conduction between two layers of the same material
• The transfer is governed by the Fourier law and is described with the following equation:
  `Q=k*A/D(T_A-T_B)`
• Connections A and B are thermal conserving ports associated with material layers. The block positive direction is from port A to port B. This means that the heat flow is positive if it flows from A to B

3. Convective Heat Transfer

• The Convective Heat Transfer block represents a heat transfer by convection between two bodies by means of fluid motion
• The transfer is governed by the Newton law of cooling and is described with the following equation:
  `Q=k*A*(T_A-T_B)`
• Connections A and B are thermal conserving ports associated with the points between which the heat transfer by convection takes place
• The block positive direction is from port A to port B. This means that the heat flow is positive if it flows from A to B

4. Temperature Source

• This Temperature Source block represents an ideal source of thermal energy that is powerful enough to maintain specified temperature at its outlet regardless of the heat flow consumed by the system
• The source generates constant absolute temperature, defined by the Temperature parameter value

5. AC Current Source

• The AC Current Source block represents an ideal current source that maintains sinusoidal current through it, independent of the voltage across its terminals
• The output current is defined by the following equation:
  `I=I_0*sin(2π*f*t+φ)`
• The positive direction of the current flow is indicated by the arrow

6. SoC Calculation

• In this above SoC calculation subsystem, we used the rate transition, gain and discrete-time integrator blocks were sum with constant value to check the status of SoC for the entire runtime
• The model estimates the battery SoC using the counting method. The intial SoC of the battery is assumed to be 100%
• This subsystem takes current as input and gives the battery SoC as output A current sensor block is used to measure discharge current and connected to SoC estimation

GRAPHICAL REPRESENTATION:

Now we have to compare the life cycle performance of the designed model at various temperatures, charge and discharge rates,

CASE-1 [Default Input]

1. Initial Ambient Temperature Source (K)

• In this case, the input of initial ambient temperature has set at 293.15 °C as from the workspace. It has shown by the display block

2. Cell Temperatures (K)

Cell 01 - 04; 06 - 10

• From cell 01 - 04 and 06 - 10, the temperature raised gradually and maintained it's level between some range till the end of the runtime. Here mentioned two cell sections are maintained only a short range of distance between there
• This was happened because of these two sections were located at the start and end of the battery pack, that's why the temperature has achieved at low level from the starting temperature

Cell 05 Fault

• About this faulty cell 05, this has got the reading from some huge level of difference were compared with the other two sections

• Because of this single cell has situated at the centre of the battery pack, generally the level of temperature at centre location of an object has always in high level temperature, that's why it may get fault for sometime. To resist this kind of situation, we have to use the cooling technology as inside the battery pack

3. SoC Calculation (%)

• By the SoC calculation, the graph reading as we gets that the battery back has fluctuating every ~300 seconds which happened by the thermal behaviour of battery pack

Following will shows the summarized resultants of the above graphical representation's cell temperature reading,

CASE-2 []

1. Initial Ambient Temperature Source (K)

• In this case, the input of initial ambient temperature has set at 296.30 °C as from the workspace. It has shown by the display block. This internal temperature were changed in the workspace for each case

2. Cell Temperatures (K)

Cell 01 - 04; 06 - 10

• From cell 01 - 04 and 06 - 10, the temperature raised gradually and maintained it's level between some range till the end of the runtime. Here mentioned two cell sections are maintained only a short range of distance between there
• This was happened because of these two sections were located at the start and end of the battery pack, that's why the temperature has achieved at low level from the starting temperature

Cell 05 Fault

• About this faulty cell 05, this has got the reading from some huge level of difference were compared with the other two sections

• Because of this single cell has situated at the centre of the battery pack, generally the level of temperature at centre location of an object has always in high level temperature, that's why it may get fault for sometime. To resist this kind of situation, we have to use the cooling technology as inside the battery pack

3. SoC Calculation (%)

• By the SoC calculation, the graph reading as we gets that the battery back has fluctuating every ~300 seconds which happened by the thermal behaviour of battery pack

Following will shows the summarized resultants of the above graphical representation's cell temperature reading,

CASE-3 []

1. Initial Ambient Temperature Source (K)

• In this case, the input of initial ambient temperature has set at 299.45 °C as from the workspace. It has shown by the display block. This internal temperature were changed in the workspace for each case

2. Cell Temperatures (K)

Cell 01 - 04; 06 - 10

• From cell 01 - 04 and 06 - 10, the temperature raised gradually and maintained it's level between some range till the end of the runtime. Here mentioned two cell sections are maintained only a short range of distance between there
• This was happened because of these two sections were located at the start and end of the battery pack, that's why the temperature has achieved at low level from the starting temperature

Cell 05 Fault

• About this faulty cell 05, this has got the reading from some huge level of difference were compared with the other two sections

• Because of this single cell has situated at the centre of the battery pack, generally the level of temperature at centre location of an object has always in high level temperature, that's why it may get fault for sometime. To resist this kind of situation, we have to use the cooling technology as inside the battery pack

3. SoC Calculation (%)

• By the SoC calculation, the graph reading as we gets that the battery back has fluctuating every ~300 seconds which happened by the thermal behaviour of battery pack

Following will shows the summarized resultants of the above graphical representation's cell temperature reading,

REFERENCES:

• Cycle life analysis of series connected lithium-ion batteries with temperature difference - https://www.sciencedirect.com/science/article/abs/pii/S0378775314005229
• Electric car batteries working - https://www.edfenergy.com/electric-cars/batteries#:~:text=A%20Lithium%2Dion%20(Li%2D,or%20nickel%2Dcadmium%20rechargeable%20batteries
• Lithium battery model with thermal effects - https://www.youtube.com/watch?v=DN7aA3-fxyk

CONCLUSION:

• The required 10-cell series of lithium-ion battery model were designed and simulated with the thermal effects
• The comparison of all cell's performance in the battery pack were expressed the same value differences at each case studies by the resultants of graphical representation