IRJET- Implementation of IoT based Dual Axis Photo-Voltaic Solar Tracker with MPPT using Raspberry-Pi and NodeMCU

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 06 Issue: 08 | Aug 2019 www.irjet.net p-ISSN: 2395-0072
© 2019, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1082
Implementation of IoT based Dual Axis Photo-Voltaic Solar Tracker
with MPPT using Raspberry-Pi and NodeMCU
Mr. A M Veera Sai1, Dr. K Rama Sudha2
2Professor, Department of Electrical Engineering, Andhra University College of Engineering, Andhra Pradesh, India
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Abstract – In this study IoT (Internet of Things) based
Dual Axis Photo-Voltaic (PV) solar tracker with maximum
power point tracking (MPPT) is proposed. In order to
extract more amount of energy from PV module, MPPT
technique along with calculation of azimuth angle and sun
elevation angle are done. So that we can obtain the
position of the sun with respect to the PV panel
geographical location. Unlike sensor-based PV tracker
which uses auxiliary devices such as LDR, small PV cells,
photo diodes, etc, to obtain the position of the sun, here we
have used sun equations to obtain the sun’s position taking
input parameters as latitude, longitude, time and day
number. MQTT (Message Queuing Telemetry Transport)
protocol is used to transmit and receive data form PV
module (Node-MCU) and server (Node-RED). The shared
information will be voltage, current, azimuth angle,
altitude angle and duty cycle for boost converter. Here
Algorithm for solving sun equations and MPTT logic is
placed in Node-RED, it calculates the duty cycle required
to extract the maximum power from the PV system. Node-
RED platform is installed on the Raspberry-Pi in which
mosquito broker is installed, and for changing the position
of PV module 2 servo motors were used and one Node-MCU
which acts as a client for the server and also it acts as a
controller for the PV module and boost converter. A
photovoltaic system has been constructed and
experimentally verified that the proposed sun tracker finds
the sun’s position with a tracking error of 0.1o and 0.47o
for altitude and azimuth angle respectively, and there is
an increase in energy of 31.92%, using proposed sun
tracker.
Key words: IoT, Node-RED, NodeMCU, MPPT,
Photovoltaic system.
1. INTRODUCTION
IoT (Internet of Things) is defined as “A network
of internet connected objects able to collect and
exchange data”. The IoT is influencing our lifestyle from
the way we react to the way we behave form air
conditioners that you can control with your smartphone
to smart cars providing the shortest route or your smart
watch is tracking your daily activities IoT is a giant
network with connected devices[1]. These devices gather
information and share data about how they are used in
the environment and how they are operated it’s all done
Node-RED is a powerful tool for building IoT
applications with a focus on wiring code blocks or sensor
blocks, known as nodes, together to perform a task[5].
Node-RED is a flow-based programming development
tool for visual programming. Originally it was developed
as an open source project at IBM to meet their need to
connect their hardware and devices to web service and
other software, but now it has become as an essential
tool for IoT programming. Node-RED was pre-installed
in Raspberry-Pi, SIMATIC IoT 2020, Artik, etc. Using
Raspberry-Pi, we can use Node-RED[6] and access the
node-red ui from the browser using (raspberry-pi ip
address):1880[7].
MQTT (Message Queuing Telemetry Transport) is a
messaging protocol that works on the principle of
publish and subscribe mechanism, for simply
communicating between the machines. For running it is
required to install a server which is named as broker. We
can install the broker on almost all platforms (windows,
mac os, linux…) and on raspberry-pi. Here mosquito
broker [8] is installed on Raspberry Pi. MQTT consumes
11 times less energy compared to HTTP for transferring
messages [9].
using sensors, sensors are embedded in every physical
device which can be traffic lights, smart watches, etc that
we come across in day to day life [3]. These sensors
continuously emit data about the working state of the
devices, but the important question is how they share
this huge amount of data, and how do we put this data to
our benefit. Internet of Things provides a common
platform for all these devices to dispose their data and a
common language for all these devices to communicate
with each other. Various sensors which emit data are
sent to IoT platform security. IoT platform integrates the
collected data from various sources further analytics is
performed on the data and valuable information is
extracted as per requirement [4]. Finally, the result is
shared with other devices for better user experience
automation and improving efficiencies. The future of IoT
industry is huge. Business insider intelligence estimates
that around 24 billion internet connected devices will be
installed by 2020[2].
1M. Tech Student, Department of Electrical Engineering, Andhra University College of Engineering,
Andhra Pradesh, India.

Node-RED dashboard is a best tool for controlling
monitoring our IoT application. It is a user interface for
all our flow which was designed on node-red docker.
2. ANALYSIS OF PROPOSED TRACKER
2.1 Earth – Sun equations:
First, we must know the location of the sun
relative to the collection device in order to collect energy
from sun. Unique vector approach is used to obtain the
sun equations[10]-[12]. Let us start finding Earth-Sun
Angles (hour angle, declination angle, latitude angle). As
we know earth revolves around the sun in an elliptical
orbit in 365.25 days with a distance of 1.496*1011m(1
AU) from sun and on aphelion(3rd of July) earth reaches
its maximum distance form sun, and minimum distance
on perihelion(2nd of Jan) over the ecliptic plane.
Earth is inclined with polar axis by 23.45O. The tilt of this
axis produces seasons with revolving around the sun.
Time is measured with rotation of the earth about its
axis, taking Greenwich, England and poles which is
known as Prime Meridian. Since earth’s orbit around the
sun is elliptical, it travels faster when it is nearer to sun,
due to which we have two times solar time and standard
time. In solar time solar noon occurs at the instant when
sun positioned is due south with relative to the
geographic location, there is a difference of around
44minutes between solar and standard time.
Hour angle (ω) is described as the distance between the
meridian of the observer and meridian in which sun rays
are parallel. ω = 0 on solar noon and it is increased by
15o for every hour.
ω = 15(ts – 12) degrees (1)
where ts = solar time in hours.
Equation of time (EOT) is defined as the difference
between mean solar time and true solar time on a give
date. EOT is determined from the below equation which
was developed by Woolf (1968) which have a accuracy
of around thirty seconds.
EOT = 0.258cosx – 7.416sinx – 3.648cos2x – 9.228sin2x
minutes (2)
X = degrees (3)
The variation of EOT with respect to month in a year is
shown below
Fig – 1- Equation of Time(minutes)
For the conversion between solar and clock time, we
need knowledge of the location, N and the local
standards. The conversion between ts and LCT (local
clock time) in 24hours is given below
LCT = ts - + LC + D hours (4)
Where D is one if the location is in a region with daylight
savings time other it is zero and EOT should be in
minutes and LC is longitude correction and is given by
LC =
hours (5)
Declination angle (δ) is defined as an angle between the
lines drawn between the centre of the earth and sun,
during noon δ = 23.5O in summer (summer solstice), and
δ = -23.5O in winter (winter solstice).
Sin δ = 0.93795 cos [0.98563 (N – 173)] (6)
Fig – 2 Earth-Sun Angles

The position of the sun relative to the coordinates on the
surface of the earth is described by two angles which are
solar altitude and the solar zenith angle. The all angles
are described with respect to the central ray from the
sun.
The solar altitude angle (α) is defined as the angle
between the central ray from the sun, and the horizontal
plane containing the observer and is given in terms of
zenith angle (θz) which is the complement of α.
θz = 90o – α degree (7)
α = sin-1 (sin δ*sin ɸ + cos δ*cos ω*cos ɸ) degrees (8)
where ɸ is latitude of the particular location
Azimuth angle (A) is an angle measured horizontally
clockwise from north base line till the meridian at which
observer is present and is given by
A’ = sin-1( ) degrees (9)
Where if cos ω ((tan )/(tan ɸ)) then A=180O- A’
Where if cos ω ((tan )/(tan ɸ)) then A=360O+ A’
Using above Earth sun equations (1-9) we can get the
position of the sun with relative to the observer[12]. In
this study dual axis tracker is used which tracks both
altitude and azimuth angles.
2.2 MPPT:
A MPPT controller plays an important role in PV
system. The duty of the MPPT is to increase the efficiency
of the PV module by adjusting the output power of PV to
the PV module by adjusting the output power of PV to its
MPP under all conditions. There are so many and
different topologies are available in the literature. MPPT
technique is mainly applied to the system whose output
Power varies with time and is not constant for a
time period.
The main problem faced by MPPT[13] is that the power
transfer efficiency of the solar panel depends on two
factors, one is the amount of sunlight falling and other is
the electrical characteristics of load. As we know that
sunlight varies with time, so the corresponding load
characteristics which gives highest power transfer
efficiency changes. So, in order to have high efficiency
the load characteristics should also change w.r.t change
in the sunlight, at this particular load characteristics we
can say that MPP is achieved and the task of the MPPT to
find MPP is also accomplished.
In this study P&O[14] algorithm is used. Which perturbs
the PV module current and voltage and power is
calculated, and it was compared with previous value to
determine perturbation in next step.
Fig – 3 V vs I and P vs V (MPP)
2.3 Node-RED:
There are three main types of nodes in node-red. First is input node allows us to give input to the node-red (e.g.
inject), second is output node which allows us to send data to outside services like twitter, email, Etc, next is memory node
or processing node which allows us to process data, these nodes have both input and one or more output. Using third type
of nodes we can incorporate functionalities like delay, trigger, storing and receiving data from a file, mathematical
operations, Etc.

Fig – 4: Node-RED flow used in this study
Figure 4 showing the node palette (left), flow canvas
(centre) and output pane (right) the main pane is the
flow creation workspace in the middle. This is where we
drag and drop nodes and connect them with wires. A set
of tabs that can be seen on the top of the workspace.
Previously created workspace can be accessed by the
tabs, flows which are created using that previous
workspace can also be seen. The output pane which is on
the right-hand side of the screen is used to toggle
between the info and debug tabs. When info is selected,
information of the selected node is shown there. When
debug is selected, it will display the output of debug
nodes, errors and warnings.
For calculating the position of the sun, Earth-Sun
equations algorithm is written in SUN EQUAITONS
function node which takes the input as timestamp and
gives us the azimuth and altitude angle, it will execute
for every five seconds. Here we must provide our
geographical location as an input to the sun equations to
know the sun location.
The part of the program for sun equations is given below Fig – 5 program for calculating sun angles
2.4 Electrical components:
1. MG996R[15] servo: Two identical servo motors are
used for adjusting the both altitude and azimuth angles.
This servo motor is having maximum stall torque of

11kg/cm, the angle of the servo motor can be easily
controlled by connecting them to Node-MCU digital pins,
It is less power consumption compared to stepper motor
and cost is also less.
2. Node-MCU[16]: NodeMCU is used as a client for the
server which can interact with hardware, and it has Wi-
Fi MCU ESP8266 integrated in it which is best tool for
IoT application development at the low cost.it has 16
GPIO pins, some which can be utilised for producing
PWM signals up to 1MHz frequency.
3.Boost converter: boost converter[17] used in this
system is shown in Figure – 6, it consists of one
MOSFET(IRNZ44N) is used as switch, with a duty cycle of
D=Ton/T, and constant switching time period of T=1/f,
where f is the switching frequency and Ton is on time
period. Here current through the load (IL) is constant
during steady state (PV voltage is constant) and is given
as IL = VPV/(Rds + RL), Rds is drain source resistance.
Current through the capacitor is ignored and the average
load current is approximately equal to the PV output
current.
IPV = D*IL (10)
Fig – 6 Boost converter
4. PV Module: A commercially available PV module (12V
150mA) is used with following specifications.
Peak Voltage: 13.97V, Peak Current: 0.152A.
3. EXPERIMENTAL RESULTS
A PV tracking system has been built and
experimentally validate the theoritical results and
performance of the proposed system. The MPPT logic is
implemented in MPPT node in the Node-RED.
Fig – 7 Block diagram of the proposed tracker
NodeMCU is used as the controller for the PV tracker and
the information for the NodeMCU is being sent from
Node-RED server which is installed on raspberry pi
through mosquitto broker using MQTT publish and
subscribe protocol., here raspberry pi is a server and
nodeMCU is a client. The MPPT logic is running on Node-
RED and duty cycle information is sent to the nodeMCU
and PWM pulses is given from the pwm pin of the MCU
to the MOSFET in the Boost converter.
The overall blockdiagram of the proposed tracking
system is shown in the Fig. 7 the PV output current is
measured using ACS712 sensor and the voltage is
measured using voltage sensor which is resistive based.
Here load for the PV panel is resistive load. NodeMCU
will send information of voltage, current, power of the
PV panel to the Node-RED using MQTT protocol, and
Node-RED will send Duty cycle, altitude and azimuth
angle information to NodeMCU The information has to
be converterd to the string data type for transmission
between nodeMCU and Node-RED.
Two MG996R servo motors each for altitude and
azimuth angle adjustments, when the nodeMCU receives
the information of altitude and azimuth it will adjust he
servos to the respective angles. These servos has an stall
torque of 9.8kg/cm (4.8V). The node-red dashboard is
designed to control and monitor the PV tracker remotely.
To access the dashboard we have to type
“[ipadress]:1880/ui” in the browser. The dashboard
created in this study is shown in below fig.8. A dropdown
selection is created on the dashboard which allows the
user to send the which type of information, If it is
selected as automatic node-RED will send altitude and
azimuth angles of the sun which are calculated using sun
equations. If we select as manual, on the right side down

of the panel we have to set the angles of which are send
to nodeMCU and it adjusts these angles to the PV panel.
Fig – 8 Dashborad of the proposed tracker
In the experiment, the constructed sun tracker was
activated. The actual data of altitude and azimuth angles
of the sun position in the sky was obtained from the
SUNCALC.ORG website at a geographical position of
(17.6868° N, 83.2185° E) were measured from hour to
hour in daylight (6:00-18:00) on Aug.10, 2019. Fig 10,
Fig. 11 compare the actual altitude and azimuth angles of
the sun position with the altitude and azimuth angles
tracked by the tracker. The comparision shows that the
average tracking error of altitude and azimuth angles are
0.1o and 0.47o respectively, which validates the
theoretical result presented in section II. The overall
experimental setup is shown in Fig.9 .
Fig – 9 The overall experimental setup
Fig – 10 comparision of actual and calculated altitude
angles
Fig – 11 comparision of actual and calculated azimuth
angles
The experiment was conducted in fixed mode and
tracking mode, for fixed mode the angle of the pv is set to
the value of the latitude angle. The fig.12 shows the
comaprision of the Power ouput with both fixed and
tracking mode. In fixed mode the total energy obtained
during a day was 11.098 Wh and in tracking mode the
total energy obtained was 14.64 Wh, so there is an
increase in the energy efficiency of 31.92% using the
proposed tracker.
0
20
40
60
80
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Altitudeangle(deg)
Time (hour)
Suncalc.org data Tracker data
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Suncalc.org data Tracker data
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source
Raspberry-Pi
NodeMCU and
Boost converter

Fig – 12 comaprision of the Power ouput with both fixed
and tracking mode
4. CONCLUSION
An IoT based sensor less dual axis sun tracker regulated
by MPPT unit was proposed. This proposed system is
very well used to test various tracking algorithms and to
control and monitor the PV cell remotely which is very
useful for research purpose. The advantage of the IoT
enabled tracker is that it reduces the effort of collecting
the data and analysing it, and to change the position of
the PV module can be done remotely. The algorithm used
in this study has successfully calculated the position of
the sun with an average tracking error of both azimuth
and altitude angles of only 0.285o.
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