1. Energy Harvesting Under Submarine Using Renewable
Energy Sources
Gaurav Phadake
Department of Engineering- Electrical Engineering
California State University, Fresno
California, US
gauravphadke93@mail.fresnostate.edu
Manasa Santoshi Yaganti
Department of Engineering- Computer Engineering
California State University, Fresno
California, US
manasasantoshi@gmail.com
Abstract—Energy power transmission in submarines has been
used from many years with the help of optical fibers or HVDC
lines, for that we need to have a constant DC power. Harvesting
systems are capable of transforming unused environmental
energy into useful electrical energy has been extensively studied
for the last two decades. Energy harvesting is an attractive as
inexhaustible replacements for batteries in low power electronic
devices and has received increasing research interest in recent
years. This paper presents a technique for energy harvesting
using three forms of energy which are Tidal, Wind, geothermal,
which will intern generate an AC supply. All renewable energies
are first converted to mechanical energies and by the use of
motors and turbines, it will get converted to AC electrical energy.
An AC-DC convertor will convert AC voltage to DC voltage,
which will be stored in batteries. The experimental measures are
carried out in PSIM to validate the theoretical predictions. This
can be carried out using piezoelectricity, but the way we are
doing it is better as it generates more energy.
Index Terms—Energy Power Transmitter, Energy Harvesting,
Wind, Tidal, Geo-thermal, Mechanical Energy to Electrical
Energy to DC Motor Forms, Piezo Electricity. (key words)
I. INTRODUCTION
Real-time communication has become a technological
standard in many aspects of our lives. It has also driven a
desire for immediate interaction with data in the work-
place and the availability of data has also driven the
development of applications for real-time analysis.
Nowadays many people think that global communications
are carried via satellite i.e., 3% of global communications
are carried out via satellite communication, which means
that 97% of the world's communications are transported
around the world via fiber optic submarine cables. Energy
harvesting technique allows energy to be dynamically
harvested from natural resources and stored in capacitor
batteries that can be used for future data transmissions.
Submarine communication can be a wired or a wireless
communication. A submarine communications cable is a
cable laid on the sea bed between land-based stations to
carry telecommunication signals across stretches of ocean.
A constant DC voltage supply required for the base stations
under submarine, which are connected through fiber optic
cables can be generated through renewable energy sources.
Common renewable energy sources that are available
under sea water include Solar, Wind, Tidal and
Geothermal. In this paper we are mainly going to focus on
the generation of constant DC voltage supply by the use of
Geothermal Energy.
II. GEOTHERMAL ENERGY
The heat that is produced within the Earth is called as
Geothermal energy. It is a renewable resource that can be
harvested for human use. Earth’s temperature rises with
depth from the surface to the core. This steady change in
temperature is known as the geothermal gradient. If
underground rock formations are heated to about 700-
1,300° C, it can become magma. Magma is molten rock
infused by gas and gas bubbles. Magma exists in the
mantle and lower crust, and sometimes bubbles to the
surface as lava. Magma heats nearby rocks and
underground aquifers. Geysers, hot springs, steam vents,
underwater hydrothermal vents, and mud pots release hot
waters. All these are the sources of geothermal energy.
Their heat can be captured and used directly for heat, or
their steam can be used to generate electricity. Ocean
Ridges are areas with enormously high heat flow, where
temperatures above 300 °C can be reached at shallow
depths. The high temperatures of the ocean ridges make
them a good target for exploitation of geothermal energy.
Therefore, innovating designs to generate electricity
installing a little submarine on top of the vent with a binary
cycle plant have been developed which is focused on the
utilization of renewable energy sources. This paper
presents a technique for energy harvesting using
geothermal energy, which will intern generate an AC
supply. All renewable energies are first converted to
mechanical energies and by the use of motors and turbines,
it will get converted to AC electrical energy.
Today, more than 10.7 gigawatts(GW) of geothermal
power capacity is online across 26 countries with a
combined output of approximately 67 terawatt hours
(TWh) of electricity. Currently, the United States is the

2. global geothermal leader with 3,086 megawatt (MW) of
installed capacity. Seven countries account for 88%
of global capacity, and among countries utilizing
geothermal resources, seven obtain 10-30% of their total
electricity supply from domestic geothermal sources.
Figure:1: Energy produced using geothermal energy
Simulink, developed by The Math Works, is a commercial
tool for modeling, simulating and analyzing multi domain
dynamic systems. Its primary interface is a graphical block-
diagramming tool and a customizable set of block libraries. It
offers tight integration with the rest of the MATLAB
environment and can either drive MATLAB or be scripted
from it. Simulink is widely used in control theory and digital
signal processing for multi domain simulation and design.
Figure:2: Mathematical model of Geothermal energy in
simulink
For writing the differential equation who describe the process ,
we start with the thermodynamics equations:-
 The quantity of heat which is transfer in time unit
represents the thermal flux:
 The ground body heat is given by:
dQ=m.c.dӨ
where, Ø represent the thermal flux , c represent specific
feature heat , m represent mass of body , C represents thermal
capacity, Ө represents the temperature , Q represent heat, dt
represents the derivative.
If we considerӨ1 the temperature of hot water and Ө0 as the
temperature of cold water, we obtain the next equation:
Figure:3: Simulink results when ᶿ1= 40 and Ø=20
III. POWER GENERATION FROM GEOTHERMAL
ENERGY
There are several basic processors that can be used for
power generation from geothermal resources. According to the
source temperature, we can choose a particular process.
Figure:2: Basic processes to generate power from
Geothermal energy
In binary cycle, the high temperature geothermal water is
used to heat a fluid that vaporizes at temperatures lower than
water that is used in closed cycle system. Binary cycle system

3. efficiency depends on geothermal water temperature and
condenser cooling temperature. The higher the temperature
difference is, between the hot and cold extremities, better is the
efficiency.
The fluid used in ORC cycle (Organic Rankine Cycle) has a
special property of vaporizing at temperatures lower than the
temperature of water vaporization. These binary working fluids
are vaporized in the vaporizer by taking heat from the
geothermal water source. These vapors are driven in turbine
where they expand, causing the spinning of the router, which in
turn drives the electric generator. After passing through the
turbine, the binary fluid is condensed and is pumped back into
the evaporator. The spinning of the turbine will generate an AC
voltage source from the generator. According to the
requirement or design aspects, there could be a single phase or
a three-phase AC voltage generation.
Figure:3: ORC Cycle
Our aim is to develop such a system according to the DC
voltage requirement.
IV. SINGLE PHASE AC TO DC CONVERTOR
An AC to DC single phase convertor has been built in
Simulink, where the results have been observed. We have
given 110 RMS AC voltage as a source voltage. The thyristors
are connected in a bridge configuration and a pulse generator
has been used as a gating pulse for the thyristor. By changing
the phase delay, the change in the DC voltage can be observed.
The output voltage can be measured across the 100Ω
resistor.
Figure:3: AC to DC single phase convertor
For 110 AC RMS voltage, we generated 25V DC voltage.
The charging and discharging of the capacitor can be controlled
by phase delay of a pulse generator. From the figure3, the
charging and discharging of the capacitor can be observed.
Figure:4: Output results for ac to dc single phase convertor
V. DC TO DC BOOST CONVERTOR
This is a basic DC to DC boost convertor with open loop
configuration. The operation is explained below.
Figure:5: DC to DC Boost convertor(Open loop)
When T is off, the current iL is conducted through the diode
D of the inductor L towards Co and the load Ro. When switch Q

4. is ON, the diode D opens and the capacitor Co discharges
through the load R during this interval.
S.NO COMPONENTS VALUES
1 R 50Ω
2 L 400µH
3 E 100V/25V
4 CO 25µF
5 R1 0.1Ω
Table 1: Design Values of the Boost Convertor
VI. THE PID CONTROLLER
A Proportional-Integral-Derivative controller is a control
loop feedback mechanism commonly used in industrial control
systems. A PID controller keeps calculating the value of an
error e(t) continuously as the difference between a desired set
point and a measured process variable and applies a correction
based on proportional, integral and derivative terms which give
their name to the controller type.
The PID controller improves the dynamic response and
reduces the steady state error. The derivative controller
improves the transient response and integral controller will
reduce the steady state error of the system.
P denotes the present values of the error. I denotes the past
values of the error. D denotes the possible future trends of the
error, based on the current rate of change.
Figure:6: Block diagram of a PID controller
A block diagram of a PID controller in a feedback loop is
represented above where r(t) is the desired process value or set
point and y(t) is the measured process value.
Transfer Function:
A PID controller works in a closed loop system. The signal
u(t) which is the output of the system, is equal to the Kp times
the magnitude of the error plus Ki times the integral of the
error plus the derivative of that error.
This control signal will be then sent to the plant and the new
output y(t) will be obtained. This new output will then be sent
back to find the new error e(t). Here KP, Ki, Kd are all non
negative and denote the coefficients for the proportional,
integral and derivative terms respectively.
The controller takes this new error as input signal and
computes the gain values ( KP, Ki, Kd).
Figure:7: DC to DC Boost Convertor with PID
Controller(Simulink model)
A DC-Dc boost convertor acts as a “Plant”, where the
output of the convertor has to be controlled by a PID controller.
The output of the system is fed back and the reference voltage
is given as 200V. The combination of reference voltage and
feedback output voltage will generate an error signal and
efforts are made to reduce the error signal and increase the
efficiency of the system by the use of PID controller. Suppose,
the given input DC voltage is 25V, then boost convertor will
generate 50V stable output voltage. But, whenever we change
the input voltage to 100V there has to be a proportional change
in the output voltage with ideally no steady state error. The PID
controller thus, reduced the steady state error, increased an
efficiency of the boost convertor.
VII. SIMULATIONS AND RESULTS
We have designed boost convertor with PID controller in
SIMULINK and observed the result for incremental voltage
which is 100V.

5. Figure:8: Output Waveforms
We have plotted output current and voltage waveforms and we
can observe that the output voltage is stable at 200V DC. By
adjusting the gain of PID controller and reference voltage, the
system stability is achieved by reducing the steady state error.
VIII. CONCLUSION
Thus, we have designed a closed loop system where we can
generate AC voltage by the use of geothermal energy. The
ORC cycle could be designed according to the requirement of
DC voltage. Then, by the use of AC-DC convertor and
integration of a DC-DC boost convertor with PID controller we
can control the system.
Thus, in this paper we presented a new idea to charge the
batteries under submarine with the help of geothermal energy.
The same process could be applied to generate the DC voltage
from wind and tidal energy sources.
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