MIET2131: Electrical Energy Storage Systems Essay


1- Explain the main components of a battery and how electricity is produced
2- What happens to the capacity of a battery as it is cycled over a year (charge / discharge)? Why are higher voltages needed to recharge a battery with age? (1 mark)
3- From the following table:
a. Which 2 elements would make the best theoretical battery?
b. What would the theoretical potential be?
c. Would this power a load requiring the theoretical potential calculated above and why?
d. Name two other potential elements and their advantages over that mentioned in
part A.
4- What are four main differences between capacitors and supercapacitors, what are the two primary forms of supercapacitance and how do they work? (2 marks)
5- What are the current draw backs of lithium based batteries for portable devices? What benefits and detriments would be gained by moving to sodium based batteries? specific values where applicable and references)
6- You are considering purchasing a plug-in hybrid vehicle, a 3.0 kW solar PV system, and a 6.4 kWh Tesla PowerWall system to reduce your greenhouse gas emissions footprint. You wish to calculate the full life cycle greenhouse gas impacts of this system with that of an equivalent ICE (petrol) vehicle and determine when (if at all) that your system will result in net greenhouse gas benefits [relative to an equivalent ICE (petrol) vehicle].
The PowerWall system will be used to store the solar PV output, and will be used exclusively for recharging the PHEV at night. The average daily electricity PV output that can be used for the system is tabulated below.


Q1: Components of a Battery

A battery is composed of three main components including the anode, cathode as well as an electrolyte. The anode is the negative electrode or the reducing electrode which releases electrons to the external circuit and is often being oxidized during an electrochemical reaction. The cathode is the positive electrode or the oxidizing which receives the electrons released from the external circuits and is often reduced when an electrochemical reaction (Bonaccorso et al., 2015).

The electrolyte is the substance which offers the transport mechanism of ions between the anode and the cathode in the battery. The electrolyte as well prevent the flow of electrons that takes place between the cathode and an ode to allow electrons to move more easily via the external circuit as opposed to passing through the electrolyte. The electrolyte is very important in the operation of a battery. Since electrons are not able to go through it, they are pushed to move through electrical conductors in the nature of a circuit which connects the anode to the cathode (Ippolito et al., 2014).

Electrolytes are mostly thought of as liquids for example water among other solvents, with dissolved alkalis or acids which are needed for ionic induction. Note should be taken however that most of the batteries among them conventional batteries are composed of electrolytes which act as ionic conductors at the room temperature (Kyriakopoulos & Arabatzis, 2016).

Separator: Separators tend to be porous materials which inhibit the anode and the cathode from coming into contact with each other which results in short circuiting inside a battery. The separators are often made from an avalanche of materials among them nylon, cardboard, cotton, polyester as well as synthetic polymer films. Separators are not chemically reactive with the cathode, anode or even the electrolyte (Larcher & Tarascon, 2015).

How electricity is produced

A chemical reaction inside the battery results in the buildup off electrode at the anode part which in turn results in an electrical difference between the cathode and the anode. Such a difference acts as an unstable buildup of electrons which results in an attempt of the electrons to reorganize to eliminate such a difference. This is attained by the electrons repelling each other, moving to the cathode. The electrolyte prevents the electrons from going into the cathode from the anode inside the battery. Upon closing the circuit the electrons move to the cathode resulting in the generation of electricity (Luo, Wang, Dooner & Clarke, 2015).

Q2 Discharge: Batteries start fading from the first day of their manufacture. A brand new battery should be capable of offering 100 percent delivery capacity. The charge time of a battery shortens with an increase in its rock content portion since there is less space that needs to be filled. Shorter charging times on faded batteries is observable more often with the case of nickel based batteries along as in part of lead acid which may not necessary be the case with Li-ion. A reduced capability of transferring charge which blocks the flow of electrons lengthens the time of charge with an old or aged Li-ion. Quite often, the reduction is linear and the faced in the capacity is in most case a function of the age and the cycle count.


(a) F2 (g)/Li(s)

(b) Theoretical potential: = +2.87-(-3.04) =5.91V

(c) This would not power a load that requires the calculated theoretical potential. The load would need an extra power to initiate the process of powering. The power transfer from the source would be the same as the power that the load consumes since the load power and the source of power are the same. The system would only be best operational when the voltage drops as well as the line of loses are kept at minimum value as an operation with a bulk power transmission ability would reduce the economic value of the system.

(d) Zn/Fe

Advantages of Zn/Fe potential elements

  • It is cheaper as compared to the combination in (a) above
  • More durable as it takes a long time to wear out bearing its manufacture properties
  • Has higher energy capability with more energy delivery efficiency

Q4. Difference between capacitor and superconductors


Super capacitor


Energy is stored in the electric field

Differs from a conventional capacitor owing to high capacitance

Energy Density

Relatively low

Relatively very high

Dielectric materials

Use polymer films or aluminium oxide are often used as the materials for separation of the electrodes

Use activated carbon as the physical barrier between the various electrodes. This forms a barrier between the two electrodes such that should n electrode be applied, there is generation of a double electric field. The electric field serves as a dielectric.


Relatively cheap

Relatively expensive


· Less drain of the battery-No deletion occurs to the car battery as a result of the capacitor

· Powerful stereo-woofers and subwoofers whose working mechanisms are based on capacitors illustrate powerful stereos

· Less damage to an equipment-It aids in the prevention of drawing charge

· High storage energy-In comparison with the conventional capacitor, it has high magnitude energy density

· Relatively low series resistance-In comparison with batteries, they are of relatively low resistance hence offering high capability of power density.

· Fast charge/discharge-Thy can quickly be charged or discharged without making any damages to the other parts (Patteeuw et al., 2015).


· Power supplies

· Axial electrolyte

· Disk ceramic of high voltage

· Metalized polypropylene

· Micro computers


· CMOS micro computer

· Power source of various toys

· Micro computer, RAM

· Driving motor

Types of super capacitors

Asymmetric super capacitors: This super capacitor join battery type electrode with capacitor type electrode

Hybrid battery super capacitors: Combines an electrochemical duo layer capacitance positive electrode types using a Li-ion type of battery.

Q5. Drawbacks of lithium based batteries for portable devices

  • They are sensitive to high temperatures
  • They are costly
  • They have an aging effect
  • They are accompanied by numerous safety concerns (Ren, Ma & Cong, 2015)

Advantages of Sodium based batteries

  • Cheap and readily available battery grade salts as compared to the battery grade salts of lithium. This renders them affordable more often in place where the energy density as well as weight tend to be a minor concern for example storage of grid energy for renewable sources of energy including solar power and the wind energy
  • Cells can be stored and transported safely: It is possible to fully drain the cells to attain a zero charge without having the active materials damaged. Lithium-ion batteries have to retain approximately 30% of the charge during the process of storage, charge that is large enough to short-circuit and ignite fire during the shipment process.
  • Excellent features of the electrochemical: These excellent features are with regard to the reversibility, high capacity of the specific discharge, reversibility ad well as the efficiency of the coulomb (Zhao et al., 2015).

Drawbacks of Sodium-ion batteries

  • They take a relatively longer time to charge
  • They take a relatively longer time to discharge
  • They discharge at a very slow rate which does not offer enough power density that can be adopted in high power applications.

In general terms, there exists a trade-off between the discharge or charge rate with regard to the capacity so that trials to enhance the rate of discharge or charge have led to greatly reduced capacity.

Q6. Yearly Cost Excluding Without Power Wall:

Cost per Day=6*(1-.0.202)+14kWh*(1+0.819)+10kWh*(1+0.202)*A


Cost per Year=365.25*Cost per Day

Using A=$0.188 @ kWh that offers a cost per year of $0.188kW/h*40.72*365.25=$2714.63 per year

Yearly Cost including Power Wall

The yearly cost of electricity for a family that uses 20kWh Off-Peak; 10kWh Partial Peak for the whole year for every state average

Cost @ Day=20kWh*(1-0.202+0kWh)*0kWh*(1+0.819) +10kWh*(1+0.202)

=27.98 kWh*A

Cost per Year=365.25 per year*Cost per Day

The cost of @ year using Power Wall 2 Strategy would translate to $0.188 kW/h*27.98 kWh/day*365.25 days @ year=$1920 year

Savings=$2714.63 -$1920


Number of Years=2714.63/794.37=3.4 years

Q7. South African platinum strike

Employees at the main producers of platinum in South Africa went on strike on November 15, 2014 protesting a doubling of their wages. The strike turned out to be longest and most costly strike in the history of South Africa. The strike resulted in a loss amounting to 1.2 million ounces of generation whose worth was approximately $2.5 billion (Zakeri & Syri, 2015).


Bonaccorso, F., Colombo, L., Yu, G., Stoller, M., Tozzini, V., Ferrari, A.C., Ruoff, R.S. and Pellegrini, V., 2015. Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage. Science, 347(6217), p.1246501

Ippolito, M.G., Di Silvestre, M.L., Sanseverino, E.R., Zizzo, G. and Graditi, G., 2014. Multi-objective optimized management of electrical energy storage systems in an islanded network with renewable energy sources under different design scenarios. Energy, 64, pp.648-662

Kyriakopoulos, G.L. and Arabatzis, G., 2016. Electrical energy storage systems in electricity generation: energy policies, innovative technologies, and regulatory regimes. Renewable and Sustainable Energy Reviews, 56, pp.1044-1067

Larcher, D. and Tarascon, J.M., 2015. Towards greener and more sustainable batteries for electrical energy storage. Nature chemistry, 7(1), p.19

Luo, X., Wang, J., Dooner, M. and Clarke, J., 2015. Overview of current development in electrical energy storage technologies and the application potential in power system operation. Applied energy, 137, pp.511-536

Patteeuw, D., Bruninx, K., Arteconi, A., Delarue, E., D’haeseleer, W. and Helsen, L., 2015. Integrated modeling of active demand response with electric heating systems coupled to thermal energy storage systems. Applied Energy, 151, pp.306-319

Ren, G., Ma, G. and Cong, N., 2015. Review of electrical energy storage system for vehicular applications. Renewable and Sustainable Energy Reviews, 41, pp.225-236

Zakeri, B. and Syri, S., 2015. Electrical energy storage systems: A comparative life cycle cost analysis. Renewable and Sustainable Energy Reviews, 42, pp.569-596

Zhao, H., Wu, Q., Hu, S., Xu, H. and Rasmussen, C.N., 2015. Review of energy storage system for wind power integration support. Applied Energy, 137, pp.545-553

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