School of Science and Technology 科技學院
Electronic and Computer Engineering 電子工程學系

Design and Evaluation of a Solar-Power Solution for Off-Grid Villages

Student Lau Hin Wing
Programme Bachelor of Science with Honours in Electronic and Computer Engineering
Supervisor Dr. Kevin Hung
Year 2021/22


In the modern society nowadays, several populations are still living in non-electricity places. Most of them locates in low developed or high-in-debt countries. They are hard to access the electricity. Teens Angel Family Centre (TAFC), an NGO in Hong Kong, observed this situation during their service trips. So, TAFC would like to develop a renewable energy system to help improve the situation.

However, they do not have much knowledge and experiences in building such kind of system in off-grid areas. Therefore, this project collaborates with TAFC and aims to provide a low cost, durable, and sustainable solar-power system for off-grid villages. The developed system would first test at Ta Kwu Ling in Hong Kong. Once the project is success, TAFC might decide to deploy the system to the places that lack electricity. Deal with this case, testing, analysis and evaluation have to be done to ensure the developed system is suitable and safe enough for off-grid households.

Demonstration Video



The project aims to provide a low-cost, durable, and sustainable solar-power system for off-grid villages. The solar-power system can generate a stable level and several amount of electricity. It should power different households' appliances and cope with the daily electricity consumption.


The objective of this project is to design, develop, build, deploy a solar-power system and evaluate the system's performance over time. Ta Kwu Ling will be the test site in Hong Kong within this project.

The solar-power system should contain the following core functions and features:
  1. Generate electricity from solar panels.
  2. Charge the portable batteries.
  3. Power different households' appliances by solar energy or battery.
  4. Provide raw data for comparison and analysis between simulation and actual results.
  5. Operate safely and efficiently in outdoor environment and under different weather conditions.

This project will carry out the following information and analysis:

  1. Statistics of electricity generated by solar-power system under different weather conditions.
  2. Statistics of electricity consumed by water pump and households' appliances.
  3. Analysis on the above statistics and system performance in Hong Kong test site.
  4. Estimations of the situation and system performance in off-grid villages in other countries.

Methodologies and Technologies used

System Design

Within the system, it is mode of a few major components which are solar panel, charge controller, battery and inverter. These four components need to be decided base on the requirements of the off-grid village and might vary between different households.

In this project, the size of 18V 300W thin-film solar panel is chosen. Since the test site in Ta Kwu Ling has a larger space for setting up the solar-power system, two pieces of this type solar panel will be installed on the roof top. The charge controller is going to use pulse width modulation (PWM) technology. It is because PWM controller is less expensive than maximum power point tracking (MTTP) one and it has a longer lifespan due to fewer electronic components. But one thing has to be concern is that there should be a matching voltage between solar panels and the battery. The model of inverter picked is KIM-001 with 3000W 220V output. For the battery, different types and capacities will be getting tested. No matter what type and size it is, only lead-acid batteries are being used. About the loads, the major load that needs to be tested and recorded is water pump. Besides, a data logger is added to record the performance of each devices for further analysis. In order to ensure the system safety, switch, circuit breaker and miniature circuit breaker (MCB) are installed to corresponding places to prevent electrical incident happening. Figure 1. and Figure 2. show about the design of the system.

Figure 2. Design of Whole System with all Components

Figure 1. Flow Chart of the System Design

System Development
In the development state, there are 9 processes for completing the whole system. They are “Requirement Collection”, “Design”, “Components Purchase”, “Implementation”, “Deployment”, “Testing”, “Maintenance”, “Data Analysis” and “Documentation”. Table 1. and Figure 3. introduce about the 9 processes.
Process Description
Requirement Collection This state is related to gather the requirements from NGO and supervisor for this project in order to design a system that can fit with the needs.
Design This state is related to design the system outline and the circuit wiring of the system.
Component Purchase This state is related to buy the suitable components of the system, and tools and equipment for building and testing.
Implementation This state is related to handle with each component individually, including testing the components' function in laboratory. The functionable components will then be combined together to do a whole system testing.
Deployment This state is related to the installation procedures in Ta Kwu Ling test site. The installing location will be discussed and set up the system onwards.
Testing This state is related to test whether the system can function properly under different circumstances.
Maintenance This state is related to adjust and modify the system if there is any failure happened to ensure the system running in track.
Data Analysis This state is related to collect the statistics in testing and using the data to analysis to evaluate the performance and efficiency of the system.
Documentation This state is related to make the documents related to the solar-power system, such as installation guideline and user handbook.

Table 1. Description of Processes

Figure 3. Flow Chart of the Processes

Tools and Equipment
There are some tools and equipment for developing the system, the summary is shown in Table 2. During development, multimeter and power supply are the necessary equipment for the whole system testing. Multimeter handles the measurements of voltage and current, which can check the specification of each component. Power supply provides a stable power source to test the stability of PWM charge controller and the charging of the lead acid battery in laboratory. In setting up the system, screwdriver, spanner and so on are the essential tools for hardware assembly, which can help to secure the system. The system needs to use solar cable to connect the solar panel and the charge controller as it deals with high UV radiation and high temperatures. Since the PWM does not have data recording function, a data logger is required to collect the information needed for data analysis. Besides, a weather station is also needed to collect the raw data of weather condition to ensure the system is reliable and for data analysis.
1.      Power Supply 5.      Power Cable 9.      Cutting Pliers
2.      Multimeter 6.      Screwdriver 10.  Ladder
3.      Data Logger 7.      Spanner 11.  Shovel
4.      Weather Station 8.      Tether And so on…

Table 2. Tools and Equipment needed

Implementation and Experiments

System Deployment

The solar power system was going to deploy at the position shown in Figure 4. The equipment station would be placed near the well, so it could reduce some of the cabling work. The solar panels would be installed on the iron frame in the farmland where did not have any obstacle covered the solar panels.

Figure 4. Planned Location of System

Materials and Equipment Purchase
In order to develop a solar system and obtain enough data for analysis, the following items had been bought.
Item Brand / Model Specification
1.      Solar Panel 驫陽 300W 18V 12A (maximum) with 20% efficiency
2.      Solar Charge Controller 日辰 CY1230 12V 30A
3.      Inverter KIM Maier KIM 001 12V 24V DC to 220V 3000W AC
4.      Water Pump (Load) 美慧 12V 120W with 7 meters wire

Table 3. Items for Solar Power System

Figure 5. Solar Panel

Figure 6. Water Pump (Load)

Figure 7. Solar Charge Controller

Figure 8. Inverter

Lead-acid batteries were going to be used in this project. To decide the size of battery for the system, it has to concern how many watts the system needed. The range of size should be from number of watts used by the load to the daily power consumption. Therefore, there are three cases suitable for the project.

  • Power used by the Load

If the water pump needs to operation 5 hours each day, then the number of watts required equals to . So two of them required 1800Wh per day, which equals to .

  • Daily Energy Generation

For the power generated by the two solar panels, since the average insolation duration in Hong Kong is 5 hours per day, the best case of total electricity provided is .

  • Daily Power Consumption

In Hong Kong, a three-member household was using around 9 kWh daily as mentioned before. This electricity consumption required at least 750 Ah battery array to support.

Deciding on the size that is the most suitable for this project, the aims act an important role. So, case B was chosen in this project. To leave some energy for spare or emergency situation, 300Ah could be a better choice for one day energy storage. Since it was hard to buy a 300Ah battery, building a battery array was decided to use for the solution. Four 12V batteries with two capacities which were 80Ah and 72Ah were being bought. The capacity in total was 304Ah for the battery array. They all were produced by AMARON with model 105D31R (80Ah) and 85D26L (72Ah).

Figure 9. Lead-acid Batteries

Other than the battery, cable was another important thing for the system work properly. Since this was a solar power project, photovoltaic cable had to be used here. Before choosing the diameter of the cable, we had to know how large the current passes through. According to the specification of the solar panel, the maximum value of current in operation was 16.6A and 17.1A for short circuit condition. As two solar panels were connected parallelly, the current passing through the PV cable would stack up which became 33.2A. For over 32A current, 6.0mm2 diameter was required. Therefore, the model PV1-F PV cable, having 6 mm2 diameter with black and red colour for each 50 meters, was bought for components linking.

Figure 10. Photovoltaic Cable

Since there were some distances between the equipment station and the well, we had to extend the length of the cable of the water pump. However, due to the characteristic of direct current, the voltage after passing through 50 meters cable was not able to power on a water pump. A transformer needed to be added before each water pump and AC 220V was used from the inverter to the transformer. Two model S-120-12 transformers of the brand SOMPOM with 12V 10A in operation were bought here.

Figure 11. Step Down Transformer (AC 220V to DC 12V)

For data collection, Table 4. showed the equipment needed to record enough statistic for data analysis.
Item Brand / Model Specification
1.      Data logger 科順 KSA 8 Channels with isolation (Monitoring Software included)
2.      Weather Station misol WH2310CA Measured Elements includes: Temperature, Humidity, Pressure, Light & UV Level, Wind Speed & Direction, and Rainfall.

Table 4. Items for Data Logging

Figure 12. Data Logger

Figure 13. Weather Station


Developed System

After development and deployment, the solar-power system was installed in Ta Kwu Ling test site. Two solar panels were connected in parallel to remain 12V to the charge controller. A 60A PWM solar charge controller was being used. Two 80Ah and two 72Ah batteries formed a 304Ah battery array by connecting in parallel. The inverter was used as the plan stated before. Then, two transformers were applied to step down AC 220V to DC 12V matching the needs of two water pumps (Load). A switch was installed in front of each water pump. For the data collection part, the data logger collects the instant power generation by the solar panels and the current voltage of the battery array. The weather station continuously logs the weather condition as an independent system.

Figure 15. Modified Design of Whole System with all Components

Figure 14. Flowchart of Developed System

Figure 16. Full View of Installation Point

Figure 17. Final View of Equipment Station

Figure 18. Final View of Power Distribution Box

Figure 19. Final View of Weak Electricity Box


Developed System

A solar power system was designed and deployed. Two 12V 600W solar panels connected in parallel to remain the same voltage because of the limitation of and the design of remaining parts at the load output of charge controller. As mentioned before, the 30A charge controller was replaced by a 60A charge controller to make the system power matched with the controller. The lead-acid batteries were also connected in parallel since the whole system was using 12V. Then the 12V 30A power would join with 12V 10A power from wind power system due to the given scenario by TAFC and form a 12V 40A power to the inverter. The inverter stepped up the DC 12V to AC 220V and delivered the electricity to the transformers. The transformers further stepped down the electricity back to DC 12V to reduce the voltage lost resulted from the cable length. The AC loads could obtain power at the inverter, while the DC loads could be connected at the transformers side. For the data logger, its channel 5 and channel 6 were attached to the input source of charge controller and the voltage of battery array. Since the output source of charge controller was always the same when there were appliances in use, no channel was decided to connect with it in this case. The weather station would collect the weather condition as a stand-alone system.

Besides, the developed system successfully achieved the objectives listed in Section 1.3. The solar panels generated power and transferred to a 60A PWM charge controller. Then, the charge controller output DC 12V 30A to charge up a 304Ah battery array when there was no appliance in use. If there was (were) appliance(s) in use, the charge controller would provide power directly from solar panels in daytimes or battery array when bad weather condition and night times. The inverter converted the DC 12V input power source to AC 220V for power up AC loads like the data logger. Two transformers then stepped down AC 220V to DC 12V to minimize the voltage drop crossed by distance to give electricity for DC loads such as water pumps to use. There were also 5V USB ports for small voltage devices like smart phone to charge. The system could satisfy most of the electricity needs of household appliances. The data logger could successfully obtain data from the solar panels and the battery array, while the weather station could log the weather information also. These provided enough statistic for the data analysis part. The whole system ran safely in the data collection period, but it is still required to monitor for the typhoon season.


To deal with the cases mentioned in section 6.4 and section 6.5, some measures could be done to improve and enhance the system. The solar panels should be connected both in series and in parallel to prevent the power generation part falling into suspension due to a failure of one solar panel. For the climate change and bad weather condition, the solar power system could join with other renewable energy system like wind power or hydro power to complement the weaknesses and maintain good performance of the system in these situations. If the budget is enough, concentrated PV cell panel could be used as it could trace the sun from time to time. This would further push up the power generating efficiency. To increase the flexibility for the change in number of appliances and people, the battery array could further expend the size and capacity. This also solves the limitation of the battery which only discharge within the first 30% normally. Since most of the days are in sunny weather, the charging of the battery should not be a problem from the system despite it becomes large in scale. Besides, larger voltage fans required as the temperature inside the equipment station could reach above 40°C under the sun which is not good for the system operating in a high temperature environment.

Future Development

The solar power system could be used independently or mixed with the electricity provided by supplier. For the data collection system, the weather station has already reserved the function of uploading the collected data to some weather information website when there is a network connection. To make the distance monitoring for data logger to success, it requires a USB to RS485 converter (or a wireless module), a computer that can connect networks, and the monitoring software and mobile app given. We can check back the statistics history by logging in into the corresponding website or software. Undoubted that a program can be written for showing all data together, or even control the system. To do so, Internet USB or WiFi model is a must to link the system with the Internet and further transfers the data.

Risk Assessment

Project Risks

In this project, there are a few critical tasks. If these tasks fail, the schedule will possibly be postponed, even lead to failure of the project. The critical tasks are related to the PWM charge controller, battery and data logger. It is necessary to define PWM charge controller and battery part as critical because once the PWM charge controller is not functioning properly or getting problem in converting voltage and current to battery, the basic objective of providing electricity for night and without sunlight condition is failed. Another reason is that the mismatching voltage between solar panel and battery might lead to damage of battery. Besides, data logger is an important component in the process of gathering raw data. If the data logger gets failure or having bad connection in between the system components and the data logger, it is hard to continue to work on the data analysis which is to evaluation the system.

Technical Risks

The major technical risk is the environment. The first factor to affect the system is typhoon. The damage brought by typhoon is hard to estimate. The strong wind, thunderstorm, heavy rains and so on can possibly destroy the system. Another factor is the trees. Most of the houses in rural area are built surrounding by trees. Once the trees lay down due to bad weather conditions or own illnesses, there is possibility that the solar-power system is one of the landing locations of the trees unfortunately. Other than that, shadows of surrounding items can affect the efficiency of the system. There might occur electricity gap as low sunlight leads to decrease in light density and not enough electricity can be converted. Besides, animals may also be a factor too. Like the solar panel and the wires, they are easily be broken by applying extra forces.

Jonathan Chiu
Marketing Director
3DP Technology Limited

Jonathan handles all external affairs include business development, patents write up and public relations. He is frequently interviewed by media and is considered a pioneer in 3D printing products.

Krutz Cheuk
Biomedical Engineer
Hong Kong Sanatorium & Hospital

After graduating from OUHK, Krutz obtained an M.Sc. in Engineering Management from CityU. He is now completing his second master degree, M.Sc. in Biomedical Engineering, at CUHK. Krutz has a wide range of working experience. He has been with Siemens, VTech, and PCCW.

Hugo Leung
Software and Hardware Engineer
Innovation Team Company Limited

Hugo Leung Wai-yin, who graduated from his four-year programme in 2015, won the Best Paper Award for his ‘intelligent pill-dispenser’ design at the Institute of Electrical and Electronics Engineering’s International Conference on Consumer Electronics – China 2015.

The pill-dispenser alerts patients via sound and LED flashes to pre-set dosage and time intervals. Unlike units currently on the market, Hugo’s design connects to any mobile phone globally. In explaining how it works, he said: ‘There are three layers in the portable pillbox. The lowest level is a controller with various devices which can be connected to mobile phones in remote locations. Patients are alerted by a sound alarm and flashes. Should they fail to follow their prescribed regime, data can be sent via SMS to relatives and friends for follow up.’ The pill-dispenser has four medicine slots, plus a back-up with a LED alert, topped by a 500ml water bottle. It took Hugo three months of research and coding to complete his design, but he feels it was worth all his time and effort.

Hugo’s public examination results were disappointing and he was at a loss about his future before enrolling at the OUHK, which he now realizes was a major turning point in his life. He is grateful for the OUHK’s learning environment, its industry links and the positive guidance and encouragement from his teachers. The University is now exploring the commercial potential of his design with a pharmaceutical company. He hopes that this will benefit the elderly and chronically ill, as well as the society at large.

Soon after completing his studies, Hugo joined an automation technology company as an assistant engineer. He is responsible for the design and development of automation devices. The target is to minimize human labor and increase the quality of products. He is developing products which are used in various sections, including healthcare, manufacturing and consumer electronics.

Course Code Title Credits
  COMP S321F Advanced Database and Data Warehousing 5
  COMP S333F Advanced Programming and AI Algorithms 5
  COMP S351F Software Project Management 5
  COMP S362F Concurrent and Network Programming 5
  COMP S363F Distributed Systems and Parallel Computing 5
  COMP S382F Data Mining and Analytics 5
  COMP S390F Creative Programming for Games 5
  COMP S492F Machine Learning 5
  ELEC S305F Computer Networking 5
  ELEC S348F IOT Security 5
  ELEC S371F Digital Forensics 5
  ELEC S431F Blockchain Technologies 5
  ELEC S425F Computer and Network Security 5
 Course CodeTitleCredits
 ELEC S201FBasic Electronics5
 IT S290FHuman Computer Interaction & User Experience Design5
 STAT S251FStatistical Data Analysis5
 Course CodeTitleCredits
 COMPS333FAdvanced Programming and AI Algorithms5
 COMPS362FConcurrent and Network Programming5
 COMPS363FDistributed Systems and Parallel Computing5
 COMPS380FWeb Applications: Design and Development5
 COMPS381FServer-side Technologies and Cloud Computing5
 COMPS382FData Mining and Analytics5
 COMPS390FCreative Programming for Games5
 COMPS413FApplication Design and Development for Mobile Devices5
 COMPS492FMachine Learning5
 ELECS305FComputer Networking5
 ELECS363FAdvanced Computer Design5
 ELECS425FComputer and Network Security5