Development and Research of a Two-Contour Solar System in the

Lorawan Network

KUNELBAYEV MURAT1*, IMANKULOVA BINARA2, SUNDETOV TALGAT2,

TYULEPBERDINOVA GULNUR1,2, ISSABAYEVA SULU3, SAGIMBAYEV LIDA1

1Al Farabi Kazakh National University, Almaty, KAZAKHSTAN

2International Information Technology University, Almaty, KAZAKHSTAN

3Egyptian University of Islamic Culture «Nur-Mubarak»,Almaty,KAZAKHSTAN

*Corresponding Author

Abstract: - This article examines the mechanism for researching and improving the energy efficiency of a solar

water heating system (SWH) in a building located in Kazakhstan. In this paper, we use data collected from

LoRaWAN to obtain information about various environmental and operational aspects of the system under

consideration, which determine the possibilities for improving the efficiency of various SWH subsystems and

develop management strategies for the effective operation of the entire system. With the help of data collected by

IoT, such as water consumption, the schedule of the heat pump and water pump, the availability of solar energy and

electricity consumption, we conduct a comprehensive energy audit to analyze the efficiency of subsystems, as well

as the performance of the system as a whole. Based on the findings obtained from the data analysis, appropriate

management strategies are developed for various subsystems in order to increase the efficiency of the entire system

and reduce the operating costs of SWH.

Key-Words: - Flat solar collector, two-contour solar installation, IoT, LoRaWAN, MQTT

Received: June 6, 2022. Revised: March 15, 2023. Accepted: May 12, 2022. Published: June 2, 2023.

1 Introduction

Traditional fuels and nuclear energy for the

sustainable development of energy resources should

now be replaced by renewable energy sources.

Renewable energy sources are sustainable and have

the potential to meet current and future projected

global environmental needs. Renewable energy

sources such as solar energy, wind, hydropower and

biogas are potential candidates to sustainably meet

global energy needs. The best alternative to meet the

growing demand for energy is solar energy. The

conversion of solar radiation into heat is one of the

simplest and most direct applications of this energy.

A flat plate solar collector is a device used to convert

solar energy into thermal energy. Flat plate solar

collectors are the most commonly used solar energy

collectors worldwide today in commercial and

domestic water heating systems. Therefore, the way

the domestic sector can reduce its environmental

impact is by installing flat plate solar collectors to

heat water. Flat plates, evacuated tubes or

concentration collectors are solar collectors for hot

water supply. The most commonly used type for low-

temperature applications is the single-layer, flat plate

type. The main component of a solar water heater is a

flat plate collector. The absorber plate serves as the

central component of the collector. The thermal

characteristics of the solar collector depend on the

optical and thermal properties, as well as on the

design of the absorber plate. A typical flat collector

consists of an absorber in an insulated box together

with transparent covers (glazing). The absorber is

usually made of a sheet metal with high thermal

conductivity, such as copper or aluminum, with

embedded or attached pipes. Its surface is coated

with a special selective material to maximize the

absorption of solar energy while minimizing solar

energy radiation. In, [1], an insulated box was

created that reduces heat loss in a flat solar collector

from the back and sides. The simplest and most

widely used devices for collecting and using solar

energy are thermosiphon or natural circulation solar

water supply systems (SWHS). They consist of a flat

collector, a storage tank and connecting pipes. The

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DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

collector consists of an absorber plate, a riser and

collector tubes, a glass cover, a casing and insulation.

The water in the riser pipes heats up and flows into

the storage tank due to the difference in density. This

flow depends on the thermosiphon head due to the

buoyancy force, which is associated with a change in

water density caused by an increase in water

temperature in the solar collector. Solar energy is

used in different types of fields for many

applications. In, [2], [3], [4], [5] we have conducted a

sufficient number of experiments on the conversion

of solar energy into thermal energy. A lot of work

has been done using single-phase heat transfer

technology. In studies, [6], [7], [8], [9], [10],

experiments were performed in a solar collector with

flat plates using a single-phase heat exchange process

using an uninsulated water tank and an uninsulated

connecting pipe, as well as an insulated water tank

and an insulated connecting pipe. For this purpose, a

flat plate solar collector acts as a heater, and a water

tank stores hot water. It is possible to reduce a huge

amount of heat loss from the tank, as well as from the

connecting pipe. The end result is the amount of

increased water temperature and the efficiency of the

flat plate collector will be increased.

In, [11], [12] developed a solar collector that is

able to capture solar energy by absorbing liquid, and

then stored in a tank used for a specific purpose. The

thermal efficiency of photovoltaic air heating using

fins attached to the collector was also investigated.

The article, [13] presents many examples of

electronic monitoring used in hospitals and medical

centers with the Arduino platform as a cheap and

simple control system. In the article, [14], an

efficiency control system was developed to control a

photovoltaic solar power plant

For automated systems, real-time monitoring is a

necessary and important stage of work, which is

carried out through constant data exchange and

communication between IoT devices and a server for

data processing and visualization. Systems that are

used for the industrial sector are often expensive and

complex. There are studies that show that the

problems of high cost, compatibility, complexity can

be solved by using inexpensive materials, as well as

written open source code. To date, the market offers

inexpensive materials and solutions that have

characteristics compatible with many systems. At the

same time, there is a great interest in systems using

solar energy as the main one, since the receipt and

consumption has an environmental advantage over

other types of energy production. The prototype is a

digital control and monitoring system for the

functioning of the solar heat supply system. The basis

of this system is a solar collector, a device that

collects thermal energy, which is used to heat water.

The key and promising aspect of the proposed system

is the Internet of Things (IoT). The use of IoT was

initially focused on the wireless transmission of data

received from sensors with low power consumption,

as evidenced by the development of technologies

such as Bluetooth Low Energy, ZigBee, NB-IoT,

LoRaWAN, etc.. The LoRa communication protocol

was used in the work because of its features, such as

transmission distance, low power consumption, low

cost. The Internet of Things is a combination of

different technologies to present solutions in different

industries. The LoRaWAN (Long Range wide-area

networks) specification is a low-power, wide-area

Network (LPWA) protocol designed to wirelessly

connect battery-powered "things" to the Internet and

targets the key requirements of the Internet of Things

(IoT). The LoRaWAN network architecture is based

on the "star" topology, in which gateways relay

messages between end devices and a central network

server. The gateways connect to the network server

via standard IP connections and act as a transparent

bridge, simply converting RF packets into IP packets

and vice versa. In the article, [15], communication

between gateways was developed, which is carried

out using wireless solutions using broadband LoRa or

FSK modulation. Security is an integral part of

LoRaWAN, there are two layers of security: one for

the network and one for the application. Network

security ensures the authenticity of the node in the

network, while the application security layer ensures

that the network operator does not have access to the

end user application data. In, [15], AES encryption

was developed, which is used for key exchange using

the IEEE EUI 64 identifier. In, [16], a comparative

study of LPWAN technologies for large-scale IoT

deployment was conducted, technologies such as

LoRa, Sigfox, NB-IoT were compared. This article

summarizes the technical differences between

Sigfox, LoRa and NB-IoT, as well as discusses their

advantages in terms of IoT factors and main

problems. LoRa technology, compared to other

technologies, is a cheaper option for network

deployment, with a very long range and with a long

battery life. The article, [17] provides a

comprehensive overview of LoRa networks,

including the technical problems of deploying LoRa

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DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

networks and the latest solutions, which will allow us

to consider the issue from a broader overview and

allow for a more practical deployment. In, [18], the

mechanism of research and improvement of the

energy efficiency of the solar water heating system

(SWH) in a hospital building located in Singapore is

studied. With the help of data collected by IoT, such

as water consumption, the schedule of the heat pump

and water pump, the availability of solar energy and

electricity consumption, we conduct a comprehensive

energy audit to analyze the efficiency of subsystems,

as well as the performance of the system as a whole.

The article considered data transmission using LoRa

technology.

The control controller system described in this

article includes temperature sensors and a real-time

sensor assembled on the STM32 microcontroller. To

improve the existing IoT solution for system

monitoring, the LoRa communication protocol is

used as a communication channel for data

transmission. The controller allows you to connect

several sensors, has good functional compatibility,

data transmission can also be carried out over long

distances, has low cost and power consumption.

2 Research Methodology

Flat solar collectors with thermosiphon circulation

are used to convert incident solar radiation into

thermal energy. This energy accumulates in the form

of tangible heat in the liquid storage tank and is used

as needed to power the premises and heat the water.

Figure 1 shows a two-circuit solar installation with

thermosiphon circulation, [15], [17].

Fig. 1: Schematic diagram of a two-circuit solar

installation with thermosiphon circulation, [15], [17].

The operation of the proposed installation is

carried out as follows. Solar energy E with

temperature t0 is absorbed by the solar collector 1,

with temperature t1, heating the flow of solar energy

passes through the translucent insulating glass 2. The

heat received from the solar flow heats the liquid in

the coils 3, which is removed from the collector, and

in its place comes cold water from the pipeline with a

valve for cold water 8, and from the siphon of the

dispenser tank 7 there is a constant thermal siphon

circulation using a circulation pipe 10. Next, the

liquid enters the heat pump 11, which consists of an

evaporator 12 of a condenser with a temperature of

t2, in which the heat exchanger is made in the form

of a spiral, absorbing the heat of the coolant, lowers

its temperature below the ambient temperature (Q2)

using a throttling valve 14, thereby contributing to

additional absorption of heat from the atmospheric

air. The diagram also shows solar radiation reflected

from the translucent coating (Q0) and the surface of

the absorbing panel (Q1). In the heat pump, the

energy of the heat carrier, with a relatively low

temperature, is transferred to the heat carrier of the

condenser heat exchanger 15 in the form of a spiral

with a higher temperature t2, which increases the

area, as well as the intensity of heat exchange. To

carry out such a cycle, a compressor 13 with a

temperature of t3, with an electric drive 17 is used.

Further, by means of the condenser heat exchanger

15 with temperature t4, heat from the heat pump (Q5)

is transferred to the accumulator tank of the heat

exchanger Q6 with temperature t6 of the heating

system 18. Since the installation has two circuits, it is

equipped with automatic circulation pumps 19 and 20

for the circulation of liquid between the solar

collector and the evaporator, the condenser and the

battery tank. The water temperature is brought to the

required technological level and supplied to the

consumer for the purpose of hot water supply and

heating, [15], [17].

WSEAS TRANSACTIONS on HEAT and MASS TRANSFER

DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

Fig. 2: Full-scale model of a flat solar collector, [15],

[17].

Figure 2 shows a full-scale model of a flat solar

collector. The solar collector is the main heat

generating unit of the solar installation. To achieve

this goal, we have developed a fundamentally new

flat solar collector, on the basis of which a standard-

sized range of solar installations for heating water

and heating the building and room will be created.

The novelty of this research is the development of a

two-circuit solar system with thermosiphon

circulation, which has a flat solar collector, which is

a heat-insulating transparent double-glazed window

with reduced pressure, and the coolant is made of

thin-walled corrugated stainless pipe. The heat

received from the solar flux heats the liquid in the

coils, which is removed from the collector, and in its

place comes cold liquid from the siphon and there is

a constant thermal circulation, which increases the

efficiency of heat transfer, eliminating additional

intermediate walls between the panel and thermal

insulation. In the article, [15], a heat pump was

developed, where the condenser and evaporator are

made in the form of a "spiral in a spiral" heat

exchanger, the heat exchanger pipelines are located

one above the other, which increases the area, as well

as the intensity of heat exchange.

3 Implementation of the IoT System

The controller combines six digital temperature

sensors (Dallas DS18B20) (Figure 3) which register

the temperature of a flat solar collector with a

thermosiphone. Real-time Clock (RTC), records the

date and time of temperature data measurements. The

sensors are connected to the STM32 microcontroller,

the power comes from the 5V pin, the digital contact

is connected via a 4.7kOhm resistor. The

microcontroller is connected to LoRa based on

SX1276/SX1278 - it is a long-range transceiver

operating at a frequency of 868 MHz. Connection to

valves. Temperature data, date, time and valve states

of the system are displayed on the display.

Fig. 3: Connection diagram of the system controller

To transfer data from end devices to the gateway,

the LMIC library was selected and installed, it allows

you to send uplink packets, encrypt and verify the

integrity of messages, receive downlink packets,

configure data parameters, activate over a wireless

network. The architecture of the system is shown in

Figure 4.

Fig. 4: System architecture: End devices in the

LoRaWAN network deployment

LoRa is a broadband radio signal with linear

frequency modulation CSS (Chirp Spread Spectrum).

The frequency of the CSS radio signal can either

increase (up-chirp) or decrease (down-chirp). It is

possible to express the signal mathematically in the

form:

WSEAS TRANSACTIONS on HEAT and MASS TRANSFER

DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

󰇛󰇜 󰇡 

󰇢

 





Also the parameters that describe the signal:

󰇛󰇜 - center (carrier) frequency of the

radio signal;

󰇡 

󰇢󰇛 󰇜 - lower radio

frequency;

 󰇡 

󰇢󰇛 󰇜 - upper radio

frequency;

BW – radio spectrum width (bandwidth);

SF – spectrum spreading factor (varies in the range

from 7 to 12);

 

 - radio signal duration;

  

 - radio frequency change rate;

      – radio signal base.

The system allows monitoring using LoRa with

characteristics such as 125 kHz spectrum width,

spectrum expansion coefficient (SF) 7, encoding rate

(CR) 4/5 of the operating frequency band. The choice

of bandwidth also affects the length of the payload.

For example, for the same 125 kHz bandwidth at 868

MHz, if SF = 7, then the bandwidth will be 5470

bits/s, and the payload will be 230 bytes. In, [19],

[20], the transmission parameters for LoRa are

presented.

The data from the end devices in the upstream

message transmits the payload to the LoRa gateway.

Next, the gateway transmits messages to the network

server via Wi-Fi or GSM (the gateway board has a

Wi-Fi module 802.11 b/g/n and an additional slot for

a GSM SIM card). There are several options for

network servers, in this case the choice was made on

a third-party server The Things Network (TTN), [21].

Figure 5 shows a detailed connection diagram of the

LORA radio module with further data transfer to the

server.

Fig. 5: Block diagram of the system

To work in the The Things Network system, we

need to register devices, choose a frequency plan

depending on the region (in this project, the

frequency of 868 MHz was selected). To join the

LoRa network, the terminal devices must go through

the activation process (Figure 6).

Fig. 6: Initialization process in TTN: selection of

operating mode

After the gateway registration procedure is

completed, the end node will be ready to transmit

sensor readings at a specified interval. To analyze

message latency, the timestamps of each sent packet

are recorded on the LoRa server. After the

connection is established, the data is converted to the

payload format in the form of hexadecimal code

(HEX) (Table 1).

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DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

Table 1. Example of the analysis of the data received

from one temperature sensor

Parameter

HEX

data

Decimal

equivalent

Ratio

Data

Temperature

7400

0.01 °C

Signed

MSB

The payload has a size, it is equal to 14 bytes

(when adding new sensors or adjusting data, the size

can be changed). Next, on the TTN server, you can

see the process of decoding the payload to obtain a

readable format (Figure 7).

Fig. 7: Code snippet for the decoder

As shown in Figure 7, the code snippet is a

decoder used to convert data from a given payload.

In the console, the decoder function is programmed

in JavaScript.

The main function of data transfer between

server components is MQ Telemetry Transport

(MQTT), [22]. The gateway connector protocol

allows you to exchange messages over two network

protocols, via rpc and MQTT (with TLS encryption).

TTN does not allow storing data, a database (DB)

was created on MySQL for storing data with further

displaying them in the browser. In this case, the SDK

on Node was used.JS with npm (package manager).

The MySQL data warehouse is used. To display the

data in the browser, a MySQL web administration

tool, phpMyAdmin, was used on the Apache web

server.

4 System Testing and Results

Experimental studies were carried out using an

automatic control controller, for stability and

accuracy of operation for a two-circuit solar

installation with thermosiphon circulation. Figure 8

shows the operation of a two-circuit solar installation

with thermosiphon circulation on a clear day. The

heat pump was running continuously from 10 a.m. to

7 p.m., so the collection of solar energy took place

during this time period. When the heat pump was

running, the water temperature at the outlet of the flat

solar collectors gradually increased in the morning,

and then gradually in the afternoon, the water

temperature at the inlet constantly increased and

decreased when the heat pump was turned off. When

the temperature of the hot water in the accumulator

tank increased, it led to an increase in the

temperature of the water at the entrance to the flat

collectors. Another reason is that the ambient

temperature and solar radiation also increased in the

morning and then gradually decreased in the

afternoon. The water temperature at the outlet of the

flat collectors reached its maximum value of 74.5 ° C

at 14:05. When the heat pump was started, the

variable mass flow in the circuit increased greatly,

and then gradually decreased. This is due to the heat

accumulated in the collector, which leads to a sudden

increase in the outlet temperature, and then to a rapid

decrease.

Fig. 8: Operation of a two-circuit solar installation

with thermosiphon circulation on a clear day

Figure 8 shows the operation of a two-circuit

solar installation with thermosiphon circulation on a

cloudy day. The heat pump worked continuously

from 10:00 to 17:00, and the collection of solar

energy also took place between these times. During

the operation of the heat pump, the water temperature

at the outlet and inlet gradually increased until 15:15

pm, and then gradually decreased. The temperature

of the hot water in the accumulator tank gradually

increased, and the variable mass flow rate also

increased. As can be seen in Figure 9, the variable

flow rate fluctuated greatly between 11:22 and 3:58

pm, which is due to solar radiation, leading to a

change in water temperature at the outlet of flat solar

collectors.

WSEAS TRANSACTIONS on HEAT and MASS TRANSFER

DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

Fig. 9: Operation of a two-circuit solar installation

with thermosiphon circulation on a cloudy day

Fig. 10: Changes in heat loss and water temperature

of the battery tank on a periodically cloudy day

Figure 10 shows the change in heat loss and

temperature of hot water in the accumulator tank

depending on the time on a periodically cloudy day.

Heat losses through the walls of the battery tank

gradually decreased between 7:00 and 9:20 a.m., and

then gradually increased due to an increase in the

temperature of hot water in the battery tank, changes

in solar radiation and ambient temperature.

Criteria that were evaluated when testing the system:

Delay: The process of transmitting data from sensors

to the server in real time was 5 seconds, which gives

a clear picture when monitoring the system.

Transmission Distance: The system, in particular

the LoRa protocol, provides a long data transmission

distance. The data stated by the manufacturer

indicates the provision of data transmission over a

distance of up to 15 km, especially in remote areas

without obstacles or with large obstacles.

Low Power Consumption: This is one of the main

advantages of the system, as LoRaWAN technology

allows you to achieve the low consumption required

for data transmission from sensors to the server.

Interoperability and Scalability: System

components are compatible, which makes it possible

to use materials from different manufacturers to

expand the system. If there is a need to connect new

sensors, that is, to improve the systems, then the

proposed system will allow this to be done.

Low Cost: The system is relatively inexpensive due

to the use of inexpensive materials and devices, also

meets the monitoring requirements.

5 Conclusion

In this work, we have developed a two-circuit solar

system with thermosiphon circulation and a control

controller of the solar system (Almaty, Kazakhstan).

The developed two-circuit solar installation with

thermosiphon circulation has a flat solar collector,

which is a heat-insulating transparent double-glazed

window with reduced pressure, and the coolant is

made of thin-walled corrugated stainless pipe. The

developed solar system control controller is able to

control the current temperature of the solar thermal

system. Experimental results showed that the

contribution of the useful heat gain during the day for

two cases was 35.1, 22.06 kWh, respectively. While

the change in mass flow varies from 2.35 to 22.4

l/min, the amount of mass flow depends on direct and

indirect parameters, such as the water temperature at

the outlet of the flat solar collector, the temperature

of hot water in the heat pump, solar radiation and the

load of hot water for consumers.

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Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023

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Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

-Kunelbayev Murat, Imankulova Binara carried out

the simulation and the optimization.

-Sundetov Talgat, Tyulepberdinova Gulnur has

implemented the Algorithm.

-Issabayeva Sulu, Sagimbayev Lida has organized

and executed the experiments of Section 4.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

No funding was received for conducting this study.

Conflict of Interest

The authors have no conflict of interest to declare.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

This article is published under the terms of the

Creative Commons Attribution License 4.0

https://creativecommons.org/licenses/by/4.0/deed.en_

WSEAS TRANSACTIONS on HEAT and MASS TRANSFER

DOI: 10.37394/232012.2023.18.5

Kunelbayev Murat, Imankulova Binara,

Sundetov Talgat, Tyulepberdinova Gulnur,

Issabayeva Sulu, Sagimbayev Lida

E-ISSN: 2224-3461

Volume 18, 2023