INTRODUCTION
Problem statement
Problem statement: Energy is nothing but the ability to do the work In day-to-day life, Electricity is most commonly used energy resource Now-a-days energy demand is increasing and which is lifeline for people Thus, this project was driven by the need for a device that could generate electricity from human movement, especially footsteps.
The urgency of project: There are many sources from which electrical energy can be generated The main energy sources include coal, natural gas, petroleum and nuclear power Most of these sources have disadvantages environmental effects including air pollution; for example: coal energy production has become one of the important causes of global warming
There by an alternative source must be discovered, many people proposes for solar energy, but it is going to be a costliest affair, moreover availability of solar energy is poor particularly in rainy & winter seasons, as a result it is not dependable As the availability of conventional energy declines, there is need to find alternate energy sources
Application of project: Electricity has become important resources for human being hence, it is needed that wasted energy must have to utilize, walking is the most common activity done by human being while walking energy is wasted in the form of vibration to the surface And this wasted energy can be converted into electricity This project gives idea about how wasted energy is used in walking or running and being applied widely and efficiently in some places where frequent expectation the movement of large numbers of people such as in educational institutions, universities and stations, airports, entrances,shopping malls and pedestrian streets.
Figure 1.5: Application of Footstep Generation
Description of the Project
By reviewing and analyzing all these critical problems, designing new form of renewable energy such as piezoelectricity would be a perfect option in which it is useful for domestic application The use of walking is increasing day by day when we are stepping amount of this wasted energy is utilized and converted to electricity byPiezoelectric effect Piezoelectric effect is the effect of specific materials to generate an electric charge in response to applied mechanical stress It is not only considered an unlimited source of energy but also very clean and environment friendly
Benefits of the system
No population: Unlike thermal energy, biomass production or hydro energy, piezoelectricity does not lead to any kind of pollution nor does it cause any harm to the environment and surroundings.
No rehabilitation: Instead of destroying thousands of acres of lands, piezoelectricity makes judicial use of it With all its apparatus laying under the ground, a piezoelectric tile instead of removing people from the area, asks for more populace to join in.
Independence in conditions weather: Is functional on sunny, cloudy, dry, windy and wet days
Objectives
The aim of this research is to harvest energy from footstep using piezoelectric disk based on the concept of polarization The objectives of the study are as follow:
To produce renewable electricity from footstep using piezoelectric disk placed along a pathway
To reduce the cost for power generation besides increasing the efficiency of power generation
To replace with available energy sources through human movement
To protect the natural environment beside that improving health through physical activities
BACKGROUND CONTENT
Introduction to Piezoelectricity
The direct piezoelectric effect was first seen in 1880 and was initiated by the brothers Pierre and Jacques Curie By combining their knowledge of pyroelectricity with their understanding of crystal structures and behaviours, the Curie brothers demonstrated the first piezoelectric effect by using crystals of tourmaline, quartz, topaz, cane sugar, and Rochelle salt.
The piezoelectric effect finds many applications such as the production and detection of sound, generation of high voltages, electronic frequency generation, high voltage and power sources, sensor, piezoelectric sensor,
Piezoelectricity, also called the piezoelectric effect This piezoelectric effect has two properties First one is the ability of certain materials to generate an AC voltage when stress is applied Second one is the converse effect, the generation of stress when an electric field is applied That means material used as a power harvesting medium
Figure 2.1: Piezoelectric effect when creating pressure
When piezoelectric material is placed under mechanical stress, a shifting of the positive and negative charge centres in the material takes place, which then results in an external electrical field
When reversed, an outer electrical field either stretches or compresses the piezoelectric material.
There are many materials, both natural and man-made, that exhibit a range of piezoelectric effects Some naturally piezoelectric occurring materials include Berlinite (structurally identical to quartz), cane sugar, quartz, Rochelle salt, topaz, tourmaline, and bone (dry bone exhibits some piezoelectric properties due to the apatite crystals, and the piezoelectric effect is generally thought to act as a biological force sensor
The Piezoelectric sensor is very special According to experimenters and scientists, when varying forces are applied on the Piezo material, different voltage readings corresponding to the force are displayed And when it is connected series or parallel, the value of the voltage and the current are extremely complicated because it depends on the forces which are applied and the material of the piezoelectric sensor And we found information like figure 2.4, which presented the value of the voltage and the current of each connection As the figure 2.4, we can see that the voltage of both connections is very small and we have to use more than one sensor
Figure 2.4: Value of Piezoelectric sensor of each connection
It can be seen from the graph that the voltage from a series connection is good but the current obtained is poor, whereas the current from a parallel connection is good but the voltage is poor But this problem is rectified in a series- parallel connection where a good voltage as well as current can be obtained.
To fix the problem of the voltage of the both connections, we have to combine series- connection and parallel-connection As the figure 2.5, the series-parallel combination not only provides an equally good voltage and current ratio but also reduces the net resistance offered by the circuit.
Figure 2.5: Value of the series-parallel connection
Full-wave bridge rectifier
In this project, the electronic circuit requires a DC power supply to power various electronic basic components from the available AC mains supply To convert the input AC to DC output, we use full-wave bridge rectifier The circuit consists of 4 diodes The four diodes are connected in a closed-loop configuration to efficiency convert the AC to DC. The principle of the full-wave bridge rectifier:
During the positive half-cycle of the input, D1 and D2 are forward-bias and conduct current D3 and D4 are reverse bias.
During the negative half-cycle of the input, D3 and D4 are forward-bias and conduct current D1 and D2 are reverse bias.
The advantage of full-wave bridge rectifier:
Don’t need a center-tapped (CT) so the price is low cost
In a bridge rectifier, the electric current is allowed during both positive and negative half cycles of the input AC signal Hence, the output DC signal is almost equal to the input AC signal.
The DC output signal of the bridge rectifier is smoother than the output DC signal of a half-wave rectifier.
The efficiency of the bridge rectifier is higher than the efficiency of a half-wave rectifier
Boost converter
The above illustrates the basic circuit of a boost DC voltage converter This circuit consists of 4 basic electronic components that are inductor L, semiconductor switch S (can be MOSFET, BJT or IGBT), diode D and capacitor C Input DC voltage source is connected to inductor The MOSFET semiconductor device acts as a switch capable of opening and closing it closes when the MOSFET is excited (a square wave is applied to the gate terminal at high level) and opens when the MOSFET is not driven (a square wave is applied to the gate terminal at low level)
The MOSFET conducts electricity, causing the right end of the inductor L to be connected to the negative terminal of the power supply Therefore, a current will flow between the positive and negative terminals of the power supply through the coil L and gradually increase from some initial value The coil accumulates energy in the form of a magnetic field Almost no current flows in the rest of the circuit because at this point
Figure 2.9: When MOSFET switch on
The circuit is active at the time we let the MOSFET break, at this time on the coil L there is an inductance voltage against the current reduction The voltage polarity across the coil L is in the opposite direction from the time the MOSFET conducts, allowing current to flow This results in two voltages, supply voltage V and voltage V across theIN L coil in series with each other This higher voltage (V + V ) forwards the diode D TheIN L generated current flows through D and charges the capacitor C to the value V + VIN L minus some voltage across D, while providing for load.
Voltage regulator circuit
In a power supply system, a regulator is an essential component, used to produce a constant output voltage in power electronics We need a voltage regulator that generates a stable output for the variations in input voltage There are different types of voltage regulators like Zener, series, shunt, fixed positive, IC, adjustable, negative, dual tracking, etc…Each type of circuit can provide an output dc voltage that is regulated or maintained at a set value even if the input voltage varies or if the load connected to the output changes In this project, we use a series voltage regulator.
The basic connection of series regulator circuit is shown in the block diagram ofFigure.2.10 The series element controls the amount of the input voltage that gets to the output The output voltage is sampled by a circuit that provides a feedback voltage to be compared to a reference voltage:
If the output voltage increases, the comparator circuit provides a control signal to cause the series control element to decrease the amount of the output voltage- thereby maintaining the output voltage.
If the output voltage decreases, the comparator circuit provides a control signal to cause the series control element to increase the amount of the output voltage - thereby maintaining the output voltage
Figure 2.10: Series regulator block diagram
DESIGN AND IMPLEMENTATION
Block diagram
Figure 3.1: Block diagram of Footstep power generation
The figure 3.1 indicates the block diagram of a footstep power generation This system can be divided into several parts: The piezoelectric material (sensor), the full wave bridge, boost converter, voltage regulator circuit and charge circuit.
The function of the piezoelectric material (sensor) is converts the pressure applied to it into electrical energy The source of pressure can be either from the weight of the moving vehicles or from the weight of the people walking over it Each object will generate different energy levels and the output of the piezoelectric material is not a steady one So, a bridge circuit is used to convert this variable voltage into a linear one The AC ripple filter is used to filter out any other fluctuations in the output to obtain a smoother wave image.
The boost converter (step-up converter) is a DC-to-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load).
The voltage regulator circuit is a circuit that has the function of generating or maintaining a stable voltage even if the input changes over a wide range We can simply
The voltage regulator circuit understand that the voltage stabilizer circuit always has a stable output voltage no matter how the input voltage changes.
The main function of the charging circuit is to store electrical energy to provide lighting, automatically cut off when fully charged, short circuit protection, overload protection, overcurrent protection.
Principle of Footstep power generation
The piezoelectric material converts the pressure applied to it into electrical energy The source of pressure can be either from the weight of the moving vehicles or from the weight of the people walking over it As the power output from a single piezo film was extremely low, combination of few Piezo films is investigated Two possible connections were tested - parallel and series connections The parallel connection did not show significant increase in the voltage output With series connection, additional piezo-film results in increased of voltage output but not in linear proportion So here a combination of both parallel and series connection is employed for producing voltage output with high current density The current produced by piezoelectric transducers is alternating in nature and hence cannot run, home appliances Thus, to make it a stable direct current, Full- bridge rectifier is commonly used as rectifier circuits to convert the AC output of a piezoelectric into a DC voltage The rectifying circuits consist of 4 diodes The produced electrical energy from piezoelectric crystal is very low in the order of 3 volts and is stored in battery to charge controller, since it is not possible to charge 6V battery through crystal output To increase the voltage, the boost converter circuit is used The level of voltage ranges 6v and it is stored in 6v battery On the other hand, the output of the bridge rectifier consists of undulating ripples superimposed on the DC voltage By connecting a simple Zener diode at the output of the rectifier circuit, we can get a more stable output
DC voltage With the charger we can store energy as well as serve for lighting activities
SIMULATION AND ANALYSIS
Boost converter
The figure 4.1 is the boost converter circuit After we connect the Piezoelectric sensor with full-wave bridge rectifier, we obtain direct current (DC),
The maximum voltage that the capacitor can operate must be bigger than voltage output
Choose maximum voltage that the capacitor can operate: 100 (V)
The maximum voltage that the diode can operate must be bigger than voltage output
Choose diode which , maximum voltage that the capacitor can operate: 60 (V)
Oscillating circuit
In the oscillating circuit, we use IC 555 According Texas Instrument’s company, we obtain the circuit
Series regulator circuit
Before connect series regulator circuit When connect series regulator circuit
Simulation
Figure 4.4: Connection of Piezoelectric sensor
Figure 4.7: The voltage after boost
Figure 4.8: The voltage after regulator
RESULT AND CONCLUSION
According to the simulation circuit, we can see that depending on the gravity acting on the sensor, it is possible to change a different voltage level, but this voltage is extremely small, so a booster and voltage stabilizer circuit is needed to can be charged to a storage battery and provide electricity for lighting operations
In the conclusion of our project, it can be seen that this is an extremely potential energy source because of its availability and environmental friendliness On the other hand taking advantage of wasted kinetic energy to convert into electricity provides a large amount of electrical energy that needs to be promoted on a large scale It is especially suited for implementation in crowded areas This can be used in street lighting without use of long power lines It can also be used as charging ports, lighting of pavement side buildings. Advantage:
Power generation is simply walking or running
Considered as available, clean energy and friendly with environment
Energy saving and easy maintenance
Battery is used to store the generated power.
Only applicable for the particular place
Initial cost of this arrangement is high.
Mechanical moving part is high
Care should be taken for batteries.