Research and Analysis of a Smart System for Intelligent Control of
PCM Water Storage Tank for Stock Farm Needs
MILENA HARALAMPIEVA, ROSEN PETROV, DENIS CHIKURTEV, VENETA YOSIFOVA
Institute of Information and Communication Technologies,
Bulgarian Academy of Sciences,
Sofia, 25 Acad. G. Bonchev str.,
BULGARIA
Abstract: - Energy efficiency is a very important component in modern systems. Modern research examines
innovative methods and techniques for increasing the efficiency of heat generation systems. A popular
approach is to apply combined methods of using energy from different heat sources. This article describes а
basic algorithm for developing an intelligent control for a system of hot-water storage tanks with PCM adapted
for a stock farm's needs. The main components of the system are described along with the PCM advantages.
The prerequisites for the system’s operation are analyzed and adapted for its management. The developed
algorithm and a control system are tested in a simulated environment and are presented conclusions of the
system’s energy efficiency improvement.
Key-Words: - Hot water storage, Intelligent control, Control system, Energy Efficiency, Phase Changing
Materials, Solar installations, Stock farms.
Received: March 21, 2024. Revised: August 23, 2024. Accepted: September 14, 2024. Published: October 18, 2024.
1 Introduction
One of the most popular topics nowadays is the
usage of renewable sources and The Green
Transition in Europe, [1]. With the advancement of
green energy technologies comes the need for
storage and releasing the gained energy. As part of
the loop of big energy users and an important
economic source, farming has the potential to
reduce energy consumption. More than 23% of the
energy costs in a farm is used for heating water, [2].
Some of the most common hot water needs include
cleaning of milk lines, tank washing, calf drinking
water, etc. This is why optimizing this division by
improving the energy efficiency of a water heating
system is essential. The processes that require the
usage of hot water usually take place during the
daylight hours, because of animals’ routines. This
factor can significantly affect the logistics and
management principle of water heating systems.
One solution is to use solar water heating panels, but
they can provide only some of the heat for the
water, which is unlikely to produce stable
temperatures for all farm needs, [3]. They can be
implemented together with indirect hot water
storage cylinders that work by using an external
source (like solar panels) to heat the stored water.
The system contains a heat exchanger, which is
where water from the boiler passes through and in
turn, heats the water inside of the indirect hot water
cylinder. Once the water has passed through, it
returns to the boiler. This process is repetitive. The
water circulates between the top of the tank where it
is hot, and the bottom where it is cooler, but heated
up by the exchanger, [4]. The hot water tanks can
store energy, thus they improve energy efficiency,
and reduce the cost of heating, [5].
Solar panels are popular in stock farms. They
have large open spaces and wide roof space where
the panels can be installed or the construction of the
solar panels can be used for providing the animals
with shade, [6]. Unfortunately, they are a seasonal
solution, most effective during the warm seasons.
Solar heating system’s thermal performance can be
improved with tanks with PCMs (Phase Changing
Materials). Using this type of material can prolong
the heat release and the steady water supply can be
provided for a longer period. The melting point for
the PCMs is between 40 and 80 °C, it is relevant for
industrial, commercial, and residential buildings.
The system’s construction can be adapted to the
conditions where it will operate. Some of the
prerequisites that should be taken into consideration
for example are purpose, flow rate, desired
temperature, weather conditions etc., [7]. The
integration of these hot water systems is a topic of
investigation and analysis, [8]. For increasing the
energy efficiency on site, they can be improved by
WSEAS TRANSACTIONS on ENVIRONMENT and DEVELOPMENT
DOI: 10.37394/232015.2024.20.47
Milena Haralampieva, Rosen Petrov,
Denis Chikurtev, Veneta Yosifova
E-ISSN: 2224-3496
484
Volume 20, 2024
intelligent control depending on the particular farm
conditions and animal needs.
An example of the high usage of warm water is
with milking robots. For each milked cow,
considerable amounts of hot water are used to clean
the teat cups and disinfect the udder. The inclusion
of energy-efficient systems in the cleaning and
disinfection systems of the milking robots will
contribute to reducing the power consumption for
heating water, [9].
This article describes the design and
development of an intelligent system for controlling
а hot water tank with PCM suitable for stock farms.
The first chapter describes the system components
and scope of operation. The second chapter
describes the system's initial algorithm for operation
based on the specific needs of a farm. A conclusion
is presented with results of the system’s
performance and energy efficiency.
2 System’s Design
The presented hot water storage system with PCM is
designed with the following main components:
2.1 Hot Water Storage Tank with Phase-
Change Material
The tank is made of steel, with aluminum
cylindrical tubular containers filled with phase-
changing material (paraffin) placed in its volume.
When the inside temperature increases, the paraffin
goes through a phase transition from solid to liquid
states, thereby accumulating thermal energy, which
when passing from liquid to solid state (i.e. lowering
the temperature) is released and, accordingly,
accumulated by the water in the tank. The operating
temperature range of this material is between 45 and
68 °C, which allows hot water to be stored for a
longer period.
2.2 Solar Panels
Solar panels are flat with a selective coating and
include the following elements: absorber, coating,
thermal insulation, and connecting pipes. They are
located on the roof, and the installation follows the
slope of the roof and the orientation of the building.
2.3 Circulation Pump
The circulation pump is electronically controlled,
with variable regulation of flow rate and pressure.
Its function is to ensure the circulation of the
working fluid.
2.4 Two-way Valve
Valves are designed to vary the flow rate. The
valves with a logarithmic flow characteristic are
most often used. They are equipped with electric
actuators. Dual thermostatic valves operate with one
or two sensors. They have wider possibilities of
application. Along with the desired temperature,
they also maintain a set temperature difference.
2.5 Controller
A digital controller is a device that reads the sensor's
data and controls active devices by performing
software instructions. In the proposed installation,
this controller is the connection between the
individual components of the system: solar
collectors and storage tank with Phase-change
material (PCM) (Figure 1).
Fig. 1: Management of the individual circuits of the
installation through the innovative programmable
controller
2.6 Electronic Relay
Electromechanical component, that is controlled by
the main controller. It switches on/off the electrical
heater in the tank.
2.7 Temperature Sensors
Sensors work on the thermocouple principle.
Thermocouples are temperature sensors with wide
application in household and automation. They are
devices composed of two different conductors,
which are heated unevenly and generate a voltage
proportional to the difference in temperature
between the two ends of the conductors. This is the
so-called thermoelectric effect.
2.8 Sunlight Sensors
It is a multi-channel digital light sensor, which can
detect UV light, visible light, and infrared light.
2.9 Water Flow Sensor
This is a high-performance piezoceramic solution
for reliable and precise flow measurement of liquid
and gas flows using ultrasonic technology.
This type of installation is used for independent
or partial operation depending on the geographical
location and external atmospheric conditions. In the
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DOI: 10.37394/232015.2024.20.47
Milena Haralampieva, Rosen Petrov,
Denis Chikurtev, Veneta Yosifova
E-ISSN: 2224-3496
485
Volume 20, 2024
bright part of the day, the solar collectors transform
the solar energy into thermal energy, which is stored
in a hot water storage tank with a phase-change
material and is utilized by the consumers when
needed. The system is most productive in the period
from May to September, due to the presence of a
large number of sunny days, and it can satisfy 100%
of the energy needs. For the rest of the year, to
achieve the set operating parameters, the system
works in hybrid mode, and an additional heat energy
source (electric heater) is also included.
The control of the installation is carried out by
the digital controller (DC), which is connected to all
the components of the system utilizing various
sensors. When a set temperature of the fluid in the
solar panel is reached, the temperature sensor sends
a signal to the controller, which turns on the
circulation pump (CP). Fluid circulation continues
until the temperature in the solar panel (SP)
becomes lower than the temperature in the hot water
storage tank (HWT). Then the controller sends a
signal to the thermal valve (TV), which stops the
circulation process. In case of an insufficient
amount of solar energy, the controller turns on the
electric heater (EH), which heats up the water in the
tank to the set parameters. The process is illustrated
in detail in Figure 2.
Fig. 2: Schematic diagram of the management of a
solar installation with a storage tank with FPM
HWT - hot water tank, TV - thermostatic two-
way magnetic valve, CP - circulation pump, SP -
solar panels for hot water, EH - electric heater, t°S-
thermal sensor.
3 Control System Operation
The studied system for hot water storage is complex
and therefore it is necessary to develop a specialized
algorithm to provide the necessary functionalities.
In addition, we propose an IoT-based system for
remote access to a heating system and possibilities
for Smart solutions.
The proposed algorithm controls the desired
temperature of the water in the heating system. That
temperature depends on two circles of the heating
system: the main circle (MC) and the solar circle
(SC).
The mathematical description of the behavior of
the individual elements of the entire system is
presented in [10].
3.1 Control of the Main Cycle System
The main circle includes the HWT with built-in ET
and PCM. The main circle can operate
independently of the solar circle. The control
algorithm for that is proposed in Figure 3. The
algorithm is implemented in the controller. To
achieve optimal energy efficiency, the water
temperature in the HWT has to be in the operating
range of the PCM, described above. This approach
is expected to provide optimal energy efficiency
because we will use the generated energy of the
PCM during the entire cycle. Every time the water is
used for farm needs, we will have internal heating
from the PCM.
Fig. 3: Block diagram of the algorithm for control of
the main circle
According to the described assumptions, we
have to control the minimal water temperature in the
HWT. That temperature must not be lower than
45°C. Regarding the upper limit, the water should
not exceed 68°C. Therefore, the logic for controlling
the MC is to turn on the water heater when the
temperature is lower than 45°C and to turn it off
when the temperature is more than 68°C.
Considering the thermal parameters of the PCM, we
have to include the generated thermal energy during
the process of draining hot water and entering cold
water in the tank. Therefore, we consider the
following equation:
Tt =ThtVht -TcVc+Tpcm (1)
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Where:
Tt - tank water current temperature,
Tht - hot water temperature,
Vht - hot water volume,
Tc - cold water temperature,
Vc - cold water volume,
Tpsm - released temperature from the PCM
We measure the hot water temperature even in
case no draining is detected. In that case, we expect
that the heat loss will be too low and the generated
heating of the PCM will provide enough energy. In
case of a lower temperature than the lower
threshold, the electric heater has to turn on. In that
case, the Vc and Tc are 0, so we use the same
equation for Tt.
Algorithm explanation: The desired water
temperature range is set in the beginning, then it is
compared to the current temperature of the water in
the HWT, and the operating range of the PCM is
also included. While the hot water is in the range of
the PCM, we expect that it will generate heat while
draining. To determine when to turn on the heater
we calculate the error using the following equation:
Err = Td-Tc (2)
Where:
Td - desired temperature threshold.
When the error drops below the lower threshold,
then the heater is turned on. The proposed control
system provides a prediction of the future water
cooling and can turn on the heater in advance when
an event of tank draining appears. This technique is
expected to provide even better energy efficiency.
The control system is illustrated in Figure 4. The
controller used is of a PID type and it activates the
heater relay. We use negative feedback by
temperature.
Fig. 4: Control diagram of the main circle
To verify that the proposed control system is
able to achieve the desired behaviour of the heating
system, we have completed some experiments in the
Matlab Simulink environment. In Figure 5, the
result from the simulation is shown. We show the
temperature difference between the set temperature
(yellow) and the real temperature (blue) while
draining the water tank. We change the temp set
point in the range (45-65), to test the system
behavior, according to the draining volume of the
water.
Based on the results, we may conclude that the
system is stable and provides the desired
performance. The generated heat from the PCM
lowers the energy consumption. The heater is
switched on, only when the temp is lower than 47
degrees. This proves that the suggested
methodology is making the system more efficient.
Fig. 5: Comparing temperature changes in the range
of 45-65 degrees
3.2 Control of the Entire Cycle System
When we consider using both circles the system
becomes more complex, because of the problems
described in the previous chapter. The inclusion of
the solar system circuit has the purpose of
improving energy efficiency and providing higher
water heating capacity. Therefore, the following
aspects of Table 1 should be addressed.
Table 1. Important points for consideration
Element
Consideration
Solar cycle
Requires
sunlight
Thermostatic
two-way
magnetic valve
Requires hot
water
Circulation
pump
May provides
efficiency
The hot water flow from the SC has to increase
the hot water in the tank. We control the SC flow by
switching on/off the CP. That process concerns the
temperature difference between the tank and SC
water. To achieve maximum efficiency, we turn on
the CP in three different cases:
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Milena Haralampieva, Rosen Petrov,
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Volume 20, 2024
- when the Tt is lower than the lower threshold and
the CP water temperature is higher than the Tt;
- when the Tt is in the range of the Td and the CP
water temperature is higher than the Tt;
- when an event of draining is activated and the CP
water temperature is higher than the Tt;
These cases will guarantee that the Tt will
always be at maximum level in the condition of
draining or lowering the current temperature in the
water tank. The control system with the included
solar system circuit is provided in Figure 6. We
have added one more controller for switching on/off
the CP and an additional block for adding the SC-
released heating in the tank.
To decide which heating source to be used we
add one more block at the beginning of the control
system. That block switches on/off the two PID
controllers according to the input values. We have
the following conditions:
- if the error is in the range of 2-10% and the SC
power is higher than 25%, switch on the PID2 only;
- if the error is in the range of 6-25% and the SC
power is higher than 50%, switch on the PID2 only;
- if the error is in the range of 25-50% and the SC
power is higher than 75%, switch on the PID2 only;
- if the error is higher than 50% and the SC power is
higher than 90%, switch on the PID2 only;
- in all cases when the SC power is not higher than
the required threshold, the system activates both the
PID1 and PID2 systems;
- in all cases, if the SC power is lower than 10%,
switch on the PID1 only.
Fig. 6: Control diagram of the MC and SC
3.3 IoT Transition System
To be part of an IoT network, the system must be
connected to the Internet and allow monitoring of
data and setting of control parameters. To perform it
qualitatively, we suggest the use of the following
technologies: Connecting the controller to an
Internet network, through a network adapter -
Ethernet, WiFi, LoraWAN; Building a
communication system based on MQTT
communication protocols; Connection of a
MongoDB-type database system for storing the
information from the sensors, from the management
and operation of the executive mechanisms;
Development of a data analysis system. This way
the system can be integrated with an application for
intelligent control from any mobile device.
4 Conclusion
This study presents a system for intelligent control
of a hot water tank with PCM with an algorithm for
its operation.
The main purpose of this research is to increase
energy efficiency in stock farms in terms of hot
water usage and improve the quality of life of the
animals. The use of PCM hot water tank has many
advantages in reducing the energy used such as
relative autonomy of the installation; lower
operating costs compared to a conventional system;
small carbon footprint; the possibility of integration
in small and medium farms; ability to automate
processes; a longer period of thermal energy storage
due to the integrated PCM.
Although the hot water storage tank with Phase
Change Material (PCM) presents several
disadvantages, the developed working model
significantly reduces energy usage. The system's
limited temperature range, typically between 45°C
and 68°C, may not suit all applications or climates,
as efficiency can be compromised if ambient
temperatures fall outside this range. The system's
efficiency depends directly on the geographical
conditions, being the highest in regions with intense
sunlight and potentially requiring supplementary
heating in less sunny areas. The need for a central
power supply to operate essential components such
as the circulation pump, digital controller, and
electric heater further limits its applicability in
remote or off-grid locations. Despite these
challenges, the model demonstrates notable energy
savings due to efficient energy storage and
optimized heat utilization.
The development and improvement of control
systems present several promising areas for future
research, of particular importance for improving
performance, reliability, and adaptability in various
applications. One of the important directions
includes the development and improvement of a
control algorithm. Future research should focus on
creating algorithms that can better manage
nonlinearity and uncertainty in dynamic systems.
Comparative studies of these algorithms in different
applications could provide information on their
relative strengths and weaknesses.
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Milena Haralampieva, Rosen Petrov,
Denis Chikurtev, Veneta Yosifova
E-ISSN: 2224-3496
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Volume 20, 2024
An important consideration is the analysis of
Multi-Control (MC) and Single-Control (SC)
systems. MC systems that include multiple
controllers working in tandem offer advantages in
terms of redundancy and fault tolerance, but can be
complex to design and manage. Conversely, SC
systems are simpler but may lack the robustness of
MC systems. Future studies should explore the
capabilities of MC and SC systems by investigating
how MC systems can be optimized for efficiency
and how SC systems can be improved for greater
reliability.
Another key area is the integration of Internet of
Things (IoT) technologies. Research should explore
how IoT-enabled sensors and actuators can improve
real-time data collection and control accuracy.
Scalability and flexibility of control systems are
important to adapt to different operating scales and
conditions. Research should focus on modular and
reconfigurable control architectures that can provide
systems that are more resilient to change and
capable of evolving over time without significant
redesign. Furthermore, future studies should
prioritize the development of control systems that
optimize energy use and minimize environmental
impact. This includes exploring energy-efficient
strategies for the control and use of renewable
energy sources.
The application of effective management
systems in the field of animal husbandry leads to a
significant reduction in energy costs and increases
the possibilities for precise monitoring of
technological processes.
Such a system can be applied not only in farms,
but also in different home, agriculture, and
industrial sectors. This way we can get one step
closer to the transition to a greener and safer future.
Acknowledgement:
The research leading to these results has received
funding from the Ministry of Education and Science
under the National science program INTELLIGENT
ANIMAL HUSBANDRY, grant agreement No
Д01-62/18.03.2021/
The research was partially supported by
National Research Program “Young scientists and
postdoctoral students -2” approved by DCM 206 /
07.04.2022: " Intelligent management systems for
sustainable microclimate ", financed by the Ministry
of Education and Science.
Declaration of Generative AI and AI-assisted
Technologies in the Writing Process
During the preparation of this work, the authors
used the AI-assisted technologies “Grammarly” and
“Google Translate” in the writing process in order to
improve the readability and language of the
manuscript
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Denis Chikurtev, Veneta Yosifova
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Volume 20, 2024
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
The authors equally contributed to the present
research, at all stages from the formulation of the
problem to the final findings and solution.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
The research leading to these results has received
funding from the Ministry of Education and Science
under the National science program INTELLIGENT
ANIMAL HUSBANDRY, grant agreement No
Д01-62/18.03.2021/
The research was partially supported by National
Research Program “Young scientists and
postdoctoral students -2” approved by DCM 206 /
07.04.2022: " Intelligent management systems for
sustainable microclimate ", financed by the Ministry
of Education and Science.
Conflict of Interest
The authors have no conflicts 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
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WSEAS TRANSACTIONS on ENVIRONMENT and DEVELOPMENT
DOI: 10.37394/232015.2024.20.47
Milena Haralampieva, Rosen Petrov,
Denis Chikurtev, Veneta Yosifova
E-ISSN: 2224-3496
490
Volume 20, 2024