EMES301 Assignment 1: Battery Design (2023)
[Groups of 2]
You are a Battery Consulting Engineer who forms part of a team that works for a renewable energy
company. You have one client who would like for you to install an inverter system for his house that
will cater for the essential loads and load shedding conditions. The client would also like to ideally
have the system pay off for itself over time. The following information was provided to you:
Household Consumption:
Essential Loads
7 Rooms
- Lounge (TV, x6 LED lights, ceiling fan)
- Study room (lights, incandescent lamp, desktop PC)
- Bathroom (x6 LED ceiling lights, bathroom extractor fan)
- Bedroom 1 (x4 LED ceiling lights, incandescent bedside lamp)
- Bedroom 2 (x4 LED ceiling lights, TV, small bar fridge)
- Kitchen (florescent lights, microwave, fridge)
- Garage (Automated garage doors, garage fluorescent lights)
Security – (3 flood lights and exterior gate motor)
Client would like additional capacity to fully charge 2 laptops
*Take note:
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You as the engineer are required to inspect and determine the ratings of the above household
appliances of the client (use realistic values for each appliance).
You may decide on the size of appliances
Load shedding constraints
Yearly load shedding schedule for 1 year
Frequency
Summer (December – February)
Autumn (March – May)
Winter (June – August)
Spring (September – November)
Hours/day
2
4
6
1
Per Week
5
3
5
2
*Take Note:
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Assume each month is 4 weeks long in duration
Each hour constitutes a charge cycle
Client energy usage:
The client’s electricity bill consumption comes to 800kWh a month at R2/kWh. However, when the
client receives the inverter system that you suggested, he will be billed on a Time-Based tariff (he will
be able to use the batteries during on-peak periods and charge them during off-peak periods). This
will allow the client to be charged at R1.3/kWh.
Other:
The client would also like the inverter to be installed inside the guest room which is 5 meters away
from the distribution board of the main house.
Budget:
The budget that the client is willing to spend is R120,000.00. The client would like to ideally save where
he can (the whole budget does not need to be spent). The consulting engineer may request additional
money but needs to justify why (does the return on investment justify it).
Assignment Requirements
Design a battery backup system that will meet the clients essential load requirements as well as
survive the load shedding constraints for the year. You will be marked according to the following
criteria:
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Use real life information and prices on batteries, inverters and miscellaneous components
found within industry (make sure to reference sources of information e.g. websites, data
sheets, user manuals, YouTube videos etc.).
Determine and tabulate (i.e. put in a table form) the individual and total power requirements
of the clients’ essential loads.
Battery Design (2 proposals)
1. Design 1: Use Lead acid battery
2. Design 2: Use Lithium based battery
[Use battery datasheets and prices to assist you in your selection and explanation.
Consider the depth of discharge, total number of cycles]
3. Draw a circuit diagram of how you would connect the cells (whether it be in series,
parallel or both). The diagram should show and explain how it will meet the customer
requirements in terms of Ah and inverter requirements in terms of DC voltage input
Choose an appropriate inverter that will be used and give its specs in terms of:
1. DC input voltage
2. output kW rating (provide the output voltage and current as well)
3. The setting that will be used for battery cut-off voltage to ensure the correct DOD is
maintained on the battery
Provide a complete bill of materials for the system. Each quote should only differ in terms of
the batteries used (i.e. the same inverter and miscellaneous components will be used in each
quote).
Draw a block diagram of the overall system and explain how it works in terms of operation
and how it will meet the client’s needs throughout the year. You must also suggest the limits
in terms of recommending which appliances he should ideally use during the periods of load
shedding.
Based on the designs that you have recommended to the client, calculate how many years
and months it will take for each system to pay off for itself.