Development of Low-cost IoT System for Monitoring and Enhancing

Renewable Energy Feed-in Tariff at Household in Hong Kong

C. C. Lee

and George Chan

School of Science and Technology, The Open University of Hong Kong, Hong Kong, China

Research and Development Department, ASM Pacific Technology Ltd., Hong Kong, China

Keywords: IoT, Feed-in Tariff, Smart Renewable Energy.

Abstract: Feed-in tariff schemes become more popular in many countries nowadays. In October 2018, the Hong Kong

Government launched a new policy scheme which was comprised of feed-in tariff scheme and renewable

energy certificates. The work mentioned in this paper aims at improving the efficiency of implementing the

feed-in tariff scheme at household in Hong Kong by using an automatic intelligent and relatively low-cost

IoT system. Besides improving the energy efficiency, the proposed system also includes a website and an

App for monitoring the system performance. The experimental results showed that the energy generated by

using the proposed system is three times more than the system without smart features. The payback period

can be greatly reduced from 11 to 6 years by using the proposed system. It encourages the development of

renewable energy sources in Hong Kong or other similar developed cities.

1 INTRODUCTION

Fossil fuel was used to be the most abundant energy

resource when human discovered how electricity

could be generated. For years, Hong Kong relied on

the combustions of fossil fuels to generate electricity.

The coal dominated the overall fuel mix with more

than 50%. The data is shown that fossil fuels actually

brought more harms than benefits to the environment

(Ajlif, 2020). As planned, it should be reduced to

around 20% in 2022, and it is expected to be

completely eliminated in 2030. It is expected that

Hong Kong's per capita annual carbon emissions of

nearly 6 metric tons will be reduced to about 3.3 to

3.8 metric tons in 2030 (EcoSmart, 2019). Therefore,

effort should be made to use more renewable energy.

It seems that Hong Kong is not a suitable place to

invest renewable energy. But, Hong Kong has a

subtropical climate where the sun shines usually from

the south at noon. There could be a huge potential for

Hong Kong to develop renewable energy sources like

solar energy. According to the research of local

officials, the daily average horizontal solar irradiation

was 3.56 kWhm

-2

day

-1

in 2017. Besides, the average

https://orcid.org/0000-0001-9365-9397

https://orcid.org/0000-0003-2821-7212

global solar radiation in 2018 was 433.5 MJm

-2

. In

addition, the average wind speed of the particular site

was about 7 ms

-1

and the median wind speed was 6.6

-1

. These are the considerable conditions for Hong

Kong to highly develop renewable energy sources

including solar and wind.

As a result, the development of renewable energy

sources would be inevitable. However, the

contributions of renewable energy such as solar and

wind energy have been less than 1% of the total

energy resources of Hong Kong up to now. There are

only a few people who installed solar or wind power

facilities. The reason is obviously lack of policy

incentives (Sauma, 2015).

Renewable Energy Feed-in tariff (FiT) could be

an opportunity for residents and office owners to take

part in by installing a renewable energy system on the

buildings or houses. The user could charge the

electricity suppliers by selling their electricity via the

successfully connected grids. However, the long

payback period hestiate the people to join the FiT

scheme. In this work, it aimed to develop an IoT

system for monitoring and enhancing renewable

energy FiT at household or small office in Hong Kong

or similar developed cities.

Lee, C. and Chan, G.

Development of Low-cost IoT System for Monitoring and Enhancing Renewable Energy Feed-in Tariff at Household in Hong Kong.

DOI: 10.5220/0010484403150322

In Proceedings of the 6th International Conference on Internet of Things, Big Data and Security (IoTBDS 2021), pages 315-322

ISBN: 978-989-758-504-3

315

Figure 1: The schematic diagram of the smart IoT system for monitoring and enhancing renewable energy feed-in tariff at

household or small office in Hong Kong or similar developed cities.

2 RELATED WORK & CURRENT

TECHNOLOGY

Automatic intelligence IoT systems become more

feasible and cost-effective in recent years due to the

development of sensors and wireless communication

technology (Mittal, 2019). One of the usage of such

technology is to control and monitor the industrial

production. It is expected that sensors and automation

machine are also applicable in renewable energy

system.

A few IoT-based monitoring systems periodically

tracked the quality of power plants were proposed and

demonstrated to endorse a better energy management

from a single building to a wider context (Domova

and Dagnino, 2017), (Carchiolo, 2019). There were

also systems using modelling to manage and optimize

the energy efficiency in various environment (Clarke,

2016), (Dao, 2017). However, there is a lack of IoT

system which is comprised of both hardware and

software to monitor and enhance the renewable

energy in the household areas.

IoT system with sensors and feedback mechanism

should be fully utilized. In the developed cities, like

Hong Kong, most of the solar energy companies still

using supporting stand for the solar panel. Although

there are some adjustable solar panel. It could only

be adjusted manually but not automatically. Solar

tracking mount technology is also a developing

technology which is similar to the proposed solar

panel. Standalone trackers allow solar panels to

maximize electricity production by following the sun

as it moves across the sky. On the other hand, some

companies have Apps to monitor the system and

power generation (Atasoy, 2015). However, the

technology is not stable yet until 2021 to replace

ground mount solar panel. Most importantly, the cost

of implementing the existing tracking solar panel is

not efficient at household or small office. Also, there

is no other sensors, like humidity sensor and wind

sensors, and no other renewable energy source as a

whole to implement the entire IoT system.

To the best of the authors’ knowledge, the

proposed work is the first low-cost IoT system for

monitoring and enhancing feed-in tariff on various

renewable energy sources at household and small

office in the developed cities.

3 METHODOLOGY

As an IoT work, the implementation of this system

required a large proportion of combination between

hardware and software. In the aspect of hardware

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316

Figure 2: Proposed residential installation of the system.

development, selection of appropriate renewable

energy devices, such as solar panels and wind turbine,

is the most critical. It will directly influence the

power output from the system. Besides, selection of

development board is also crucial because it is the

central processor of the system. Other selected

components should be compatible to the selected

development board. It can enhance the combination

between hardware and software and reduce the time

for troubleshoot in later stages.

In the aspect of software development, the system

will be connected to the Internet through WiFi

technology. By using Application Programming

Interface (API), data will be uploaded automatically

to the Google Cloud and stored in the Google

Spreadsheet. The sketch of the development board

and the procedure of proceeding the Authorization

between Temboo platform and Google Developer are

essential. Finally, the data will be displayed in the

website (called EcoSite) and the Smart App (called

EcoView). The EcoSite is a website for real time

monitoring of the renewable energy system. It shows

the chart in the page of Monitor that user can

understand the amount of power generated, profit and

paid back period of the renewable energy system. For

the EcoView, it was developed to process, calculate

and displace the raw data on the spreadsheet

automatically and upload the results (total, average by

hour, minimum and maximum of the income, energy,

and power of EcoStar with the operative duration) to

the Firebase project EcoStar thunkable 1 daily at

midnight. More importantly, EcoView can display

the charts and the data of the desired date. EcoView

is applicable on both IOS and Android system. In the

system, Google Sheets API is enabled in order to

allow Temboo Application get access to the

designated spreadsheet. Besides, AppendRow API is

used to append rows of data to the spreadsheet. The

Figure 1 shows the schematic diagram of the smart

IoT system for monitoring and enhancing renewable

energy feed-in tariff at household or small office,

while the Figure 2 shows the proposed residential

installation of the system in Hong Kogn or similar

devleoped cities. Figure 3 shows the logical flow

chart of the proposed system.

Figure 3: Logical flow chart of the proposed system.

Development of Low-cost IoT System for Monitoring and Enhancing Renewable Energy Feed-in Tariff at Household in Hong Kong

317

Figure 4: The base of adjustable solar panel.

3.1 Hardware Configuration

For the design of the system, all the renewable energy

devices are connected to batteries through a charge

controller. All the devices and components are DC

(Direct Current). This setting is due to the budget and

scale limitations of the project. However, if the

system is applied to residential or commercial use, all

the renewable energy devices will be connect to a

meter by using special PV connector and Grid Tie

Inverter (GTI). The meter will be provided by the

Electric company. The meter used can only get the

input of AC (Alternative Current) power. Therefore,

it is recommended to use GTI for the conversion from

DC power to AC power.

In the past, people used AC generator to convert

DC power to AC power for providing back-up

electricity. However, using AC generator will cause

a high extent of power loss. During the conversion,

the load current will flow through the armature of the

AC generator. The resistance and inductive reactance

of the armature will cause a voltage drop. Therefore,

the voltage and power generated will be lost. For

providing back-up electricity, the amount of power

loss can be acceptable. However, for energy FiT

schemes, the money earned depends on the amount of

energy generated. It is unacceptable to have a high

extent of power loss.

Using GTI can also convert DC power to AC

power. However, a grid tie inverter can produce sine

wave AC electricity that matches the voltage and

frequency of the grid exactly. After matching the

voltage and phase of the grid sine wave AC

waveform, people can inject electrical power

efficiently and safely into the grid. Therefore, the

problem of power loss can be eliminated. As a result,

if the smart system is applied to residential or

commercial use, the charge terminals of the charge

controller will be connected to a GTI through a

special PV connector.

There would be three options of development

boards for the Smart System, which would be

Arduino UNO Rev 3, Raspberry Pi Model B 3+ and

Micro:bit. Since the development board is the core in

the system, therefore there is a need to be extremely

careful when selecting the development board.

Besides, there are other criteria for the selection of

development board for the Smart System. For

example, in order to monitor and control some

hardware components, such as light sensor and servo

motor, open source for hardware design is one of the

requirements. Because of the connection to the

hardware components, both digital and analogue I/O

are required. Finally, since the connection of the

Smart System is WiFi, therefore on-board WiFi chip

is preferred. Therefore, Arduino UNO was chosen as

the development board for the Smart System.

The phototransistors (light sensors) is placed on

protective cases, which is produced by 3D printing

that stuck on the edge of solar panel at the top and the

bottom, in order to track solar orbit by comparing the

light intensity. The smart system compares the light

intensity and adjust the solar panel perpendicular to

the sun by the movement of servo motor which was

fixed on the 3D-printed stand on the base of

adjustable solar panel as shown in Figure 4.

Therefore, the solar panel is expected to enhance the

efficiency by strengthening the light intensity

collection.

Miroad KY55 5528 is selected as the light sensor

in the system as it contains a MV358I chip that would

make the control easier. In order to keep measuring

the power generated by the solar panel and wind

turbine, ACS712 current sensor as shown in Figure

S12 was used. The ACS712 is a Hall effect based

linear current sensor. The ACS712 Chip, as shown in

Figure S13, works like a magnetic isolator since the

current sensing element is electrically isolated from

the measure device. The magnetic field surrounding

the piece of wire when current flows through the

current sensing metal and the Hall effect sensor

detects that current through a little bit of integral

electronics provides a signal on those pins that is

between 0V and 5V.

After the selection of appropriate hardware

devices and components, a circuit is designed to

connect all these devices and components into a

single system. For the operation of the system,

Arduino UNO Rev 3 is the core development board.

Iduino Yún Shield is a supplementary development

board especially used for providing WiFi support.

Two development boards can be connected by simply

combining them together.

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Generally, the positive terminal of all the

renewable energy devices are connected to the

positive input terminal of the charge controller. The

negative input terminal of the charge controller are

connected to IP+ (current in) terminal of all the

current sensors. The IP- (current out) terminal of all

the current sensors are connected back to the negative

terminal of all renewable energy devices. Two

batteries are connected in serial. The positive and

negative terminal of the battery are connected to the

positive and negative charge terminal of the charge

controller respectively. The battery capacity indicator

is connected to the batteries in parallel.

A servo motor and two light sensors are used.

Together with the current sensors, all the sensors and

the servo motor are powered by the 5V output pin of

the Arduino UNO. All the above DC devices are

connected in parallel. The negative terminal of these

DC devices is connected to the ground provided by

Arduino UNO.

For the arrangement of I/O pins, 5 analog pins and

1 digital pin are used. Top and bottom light sensors

are connected to analog pin A1 and A2 respectively.

Current sensors for adjustable solar panel, fixed solar

panel and wind turbine are connected to analog pin

A3, A4 and A5 respectively. Servo motor is

connected to digital pin D9. The system is powered

by the DC power supply, in order to mimic the stable

power supply in residential house. However, if the

system is directly connected to DC power supply, the

current would be large enough to damage the

development boards. Therefore, a resistor is

connected to the development boards in parallel, in

order to prevent large current flowing to the

development boards. By using the Digital Multimeter

(DMM), the resistance of the whole system is

measured to be 11.4286Ω. After calculation, the

suitable range of resistance of the selected resistor is

between 10 and 12Ω. After some experiments, the

suitable power rating of the resistor is 20W.

Therefore, a resistor with 12Ω and 20W is connected

to the system in parallel.

By using parallel resistance formula, the

resistance of the system is reduced from 11.4286Ω to

5.8537Ω. The current flow of the system is increased

from 0.7A to 1.3667A. However, the current flow to

the development boards will be changed to 0.4481A,

which is calculated by using the formula 1.3667A ×

[5.8537Ω / (5.8537Ω + 12Ω)]. The resistor used

shares the rest of the current flow (1.3667A –

0.4481A = 0.9186A). The use of resistor is to reduce

the current flow to the development boards, in order

to protect it from damage.

By using the DC power supply, the optimum

voltage and current for powering up the system is

obtained to be 5V and 0.7A. The exact voltage of the

5V output pin from Arduino UNO is measured to be

4.1V, which is large enough to power up the servo

motor and all the sensors.

3.2 Firmware Design

In the system, the software support takes an important

part. For example, through the design of Arduino

sketch, different hardware devices, such as solar

panels and sensors, are optimum to monitor and

enhance renewable energy FiT. By the use of WiFi

technology, the system can be connected to the

Internet. Data, such as renewable energy generated

and the money earned by the users, will be uploaded

to the Google Cloud automatically. The uploaded

data will be further proceeded for analysis, and finally

the results will be displayed in EcoSite and EcoView.

When particularly focusing to the software

development of the system, it does not only required

to design the sketch for the operation of the hardware

devices such as motor and sensors, but also required

to design the sketch for the connection between

Arduino boards to the Internet. Before connecting to

the Internet, it is critical to get the Google

Authorization, which allows the Temboo application

getting access to a designated Google Spreadsheets.

After the operating sketch of the system has been

designed and accomplished, it will be complied and

uploaded to the Arduino boards. The uploading

method is through WiFi. Therefore, no wired

connection between the system and the personal

computer is required.

For the use of comparing energy efficiency, both

adjustable solar panel and fixed solar panel are

connected to the system during simulation. One of the

solar panels is installed to a fixed solar panel

positioner. Another solar panel is installed to another

solar panel positioner and controlled by a servo motor

and two light sensors.

In the sketch used to control the solar panel by

servo motor and light sensors, the light values are

compared. If the light value from the top sensor is

larger than that from the bottom sensor, the top sensor

will take control of the servo motor. If the light value

from the top sensor is less than or equal to that from

the bottom sensor, the bottom sensor will take

control. By executing the map() function, the servo

motor, jointed with the solar panel, will rotate to the

position that can obtain the highest light level.

For the simulation of generating renewable

energy, the measurement of energy generated by the

Development of Low-cost IoT System for Monitoring and Enhancing Renewable Energy Feed-in Tariff at Household in Hong Kong

319

renewable energy device is required. In order to

obtain the energy values, the power values are

required to be measured. In the system, current

sensors are used. The power generated by the

adjustable solar panel, fixed solar panel and wind

turbine are required to be measured. Therefore, three

current sensors are used for the system. After that, the

power values are obtained by multiplying those

voltage values with the corresponding current values.

Although the current sensors that we used are the

same in module and rating, they can never be

identical. Therefore, the above formula will be

slightly tuned for measuring different devices.

After the sensors got the data, these data will be

automatically uploaded to the Google Spreadsheet.

In order to achieve it, the Google API and Temboo

Platform is used. After creating the Temboo Header

File and setting the profiles, the Arduino sketch was

designed to upload data from Arduino to Google

Spreadsheet by calling Temboo application through

Arduino.

3.3 EcoSite Design

The Google-based application Google Site was

selected for the collaboration and communication

with the other users. It is because Google Site could

help the inexperienced applicants who have no

programming backgrounds to create and edit a

website in an intuitive way. The methodology of the

design and information sharing was simple and easy

by dragging and dropping the functions provided in

the toolbar. Moreover, the other Google-based

applications such as Google Docs and YouTube can

be included, integrated and organized in to one that it

could be compatible with Google Sheets to which the

raw data from EcoStar would be transferred.

3.4 EcoView Design

In order to allow the data, such as the units of energy

generated, to be automatically updated and uploaded

and the users of EcoStar to check for the data

remotely, the App, called EcoView, was created.

Supported by assistant online services including

Firebase, Google Sheets, Google Script and Google

Docs, the raw data of EcoStar from Google Sheets

could be automatically updated and calculated. Next,

the macro program written in Google Script would

transfer and calculate the new raw data on a newly

created sheet and upload the results to Firebase. Then,

the prepared charts corresponding to the trends of

data in Google Sheets would change along with the

Figure 5: Structural Diagram of EcoView.

new data and be published for users to view by

Google Docs. Simultaneously, as a real-time database

supported by Google, Firebase would store the

uploaded data in terms of links. The user may look for

the data of certain days by tracking through the links.

The process would be repeated daily with the support

of the time-based trigger setting of Google Script.

To develop EcoView, the App developer

Thunkable X was selected. There were three reasons

for the decision. Firstly, Thunkable X was compatible

with both IOS and Android systems so users of

different systems could be supported. Secondly, it

was designed with reference to another two well-

accepted App developers, MIT App Inventor and

Thunkable, which indicated that it was reliable and

mature for App development. Thirdly, Thunkable X

was built associated with the cooperative services

with Firebase and WebViewer that it would be more

convenient to upload data to or draw data from

Firebase and the viewing of the charts would be

allowed. The structural diagram of EcoView is as

shown in Figure 5.

4 EXPERIMENTAL RESULTS

The prototype for the system was built as shown in

Figure 6. All the hardware devices, including the

solar panels, wind turbine and water-proof box, are

set up at the rooftop. The SIM card router is set up in

an in-house area at 10/F of the building in the campus.

The WiFi extender is set up at the ladder between

10/F and 11/F of the same building.

The noncumulative power display on EcoSite

with blue line and red line is as shown in Figure 7 to

represent power (adjusted) and power (fixed)

respectively. Meanwhile, the noncumulative power

display on EcoView with blue line and red line is as

shown in Figure 8 to represent power (adjusted) and

power (fixed) respectively.

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320

Figure 6: The first prototype of the proposed system.

The data obtained by the system is transmitted to

the Google Sheet via the use of WiFi and Temboo

platform. The data analysis on five different duration,

time and date can be found in Table 1. The

experimental results showed that the energy

generated by using the proposed system is three times

more than the system without smart features. In order

to compare the payback period of system with and

without the proposed system, a control experiment

which do not have smart elements in it was also

conducted. By analysing the cost of system and the

gross profit earned. The payback period of smart

system is 5.84 years while that of control experiment

is 10.56 years.

5 CONCLUSIONS

A smart system, called EcoStar, was developed to

enhance the renewable energy generated, through the

well combination of hardware and software. As

shown in the experimental results, it is proved that the

development of this smart IoT system can increase

Figure 7: Noncumulative power display on EcoSite with

blue line and red line representing power (adjusted) and

power (fixed) respectively.

Figure 8: Noncumulative power display on EcoView with

blue line and red line representing power (adjusted) and

power (fixed) respectively.

Table 1: This caption has one line so it is centered.

Date and Time Duration Power of the Fixed Panel Power of the Adjustable Panel

Day 1

(10:01:12 - 12:45:42)

02:44:30 0.18 W 0.54 W

Day 2

(10:20:54 - 15:32:02)

05:11:08 0.27 W 0.56 W

Day 3

(12:22:49 - 17:25:17)

03:02:28 0.28 W 0.69 W

Day 4

(09:53:24 - 17:42:53)

07:48:29 0.21 W 0.58 W

Day 5

(09:27:34 - 14:55:29)

05:27:55 0.29 W 0.57 W

Day 6

(15:12:00 - 17:40:14)

02:28:14 0.20 W 0.53 W

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321

the energy efficiency of generating renewable energy.

An automatic and wireless system has been

developed, to not only increase the energy efficiency,

but also provide a convenient way for users to

monitor the results by the use of website and App.

During the construction of this system, many

opinions and feedback from different fields of

stakeholders are received. Under the system EcoStar,

a website called EcoSite and an App called EcoView

are developed for monitoring the renewable energy

feed-in-tariff. This smart system is a prototype,

however, the application of this system can be well-

projected as a cost-effective and intelligent system.

ACKNOWLEDGEMENTS

The work described in this paper was supported by

The Open University of Hong Kong Research Grants

(No. ROU/E08/19 and R5082).

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