INTRODUCTION
Problem statement
Energy is fundamentally the capacity to perform work, with electricity being the most widely utilized energy source in our daily lives As energy demand continues to rise, it has become essential for sustaining modern life This project aims to develop a device capable of generating electricity from human movement, particularly through footsteps, addressing the growing need for sustainable energy solutions.
The urgency of addressing energy generation is critical, as various sources such as coal, natural gas, petroleum, and nuclear power contribute to our electricity supply However, many of these energy sources have significant environmental drawbacks, particularly coal, which is a major contributor to air pollution and global warming.
As conventional energy sources dwindle, the search for alternative energy solutions becomes increasingly urgent While solar energy is often proposed as a viable option, its high costs and inconsistent availability during rainy and winter seasons raise concerns about its reliability Therefore, it is essential to explore and invest in diverse renewable energy sources to ensure a sustainable energy future.
Electricity is a vital resource for humanity, making it essential to harness wasted energy Walking, a common human activity, generates energy loss through vibrations on surfaces This project explores the conversion of this wasted energy into electricity, highlighting its potential applications in high-traffic areas like educational institutions, universities, transportation hubs, shopping malls, and pedestrian streets By effectively utilizing the energy produced during walking and running, we can enhance energy efficiency in these environments.
Figure 1.5: Application of Footstep Generation
Description of the Project
The increasing reliance on walking presents a significant opportunity to harness wasted energy through innovative renewable energy solutions like piezoelectricity This technology utilizes the piezoelectric effect, where specific materials generate electric charge in response to mechanical stress, converting kinetic energy from footsteps into usable electricity Not only is piezoelectricity an abundant and sustainable energy source, but it is also environmentally friendly, making it an ideal choice for domestic applications.
Benefits of the system
Piezoelectricity stands out as a clean energy source, as it generates energy without contributing to pollution or harming the environment, unlike thermal energy, biomass production, or hydro energy.
Piezoelectricity offers a sustainable solution by utilizing land without the need for extensive rehabilitation or destruction By installing piezoelectric tiles underground, this technology encourages population growth in the area rather than displacing residents, promoting efficient land use while harnessing energy.
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, discovered by Pierre and Jacques Curie in 1880, marked a significant advancement in the study of materials By integrating their expertise in pyroelectricity with insights into crystal structures, the Curie brothers successfully demonstrated this phenomenon using various crystals, including 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, known as the piezoelectric effect, refers to the unique ability of specific materials to produce an alternating current (AC) voltage when subjected to mechanical stress Additionally, this effect encompasses the converse phenomenon, where an electric field induces stress within the material Consequently, piezoelectric materials serve as effective mediums for power harvesting.
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.
Various materials, both natural and synthetic, demonstrate piezoelectric effects Notable naturally occurring piezoelectric materials include Berlinite, which shares a structure with quartz, along with cane sugar, quartz itself, Rochelle salt, topaz, tourmaline, and dry bone The piezoelectric properties in dry bone are attributed to apatite crystals, and this effect is believed to function as a biological force sensor.
The Piezoelectric sensor is a unique device that generates varying voltage readings in response to different applied forces The complexity of the voltage and current values increases when these sensors are connected in series or parallel, as they depend on both the applied forces and the specific piezoelectric material used Figure 2.4 illustrates the voltage and current values for each type of connection, revealing that the voltage levels are quite low, necessitating the use of multiple sensors for effective measurement.
Figure 2.4: Value of Piezoelectric sensor of each connection
The graph illustrates that while a series connection provides high voltage, it results in low current Conversely, a parallel connection offers strong current but at the expense of voltage However, these limitations are addressed in a series-parallel connection, which successfully delivers both high voltage and current.
To address the voltage issue in both connections, a series-parallel combination is essential This approach, as illustrated in Figure 2.5, effectively balances the voltage and current ratios while simultaneously lowering the overall resistance in the circuit.
Figure 2.5: Value of the series-parallel connection
Full-wave bridge rectifier
This project involves an electronic circuit that utilizes a DC power supply to power essential components from the AC mains supply A full-wave bridge rectifier, composed of four diodes arranged in a closed-loop configuration, efficiently converts the input AC voltage into a DC output The principle behind the full-wave bridge rectifier is to ensure effective conversion of alternating current to direct current.
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
A bridge rectifier enables electric current to flow during both the positive and negative half cycles of an input AC signal, resulting in an output DC signal that closely resembles the input AC waveform.
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
A boost DC voltage converter circuit consists of four essential components: an inductor (L), a semiconductor switch (S), a diode (D), and a capacitor (C) The input DC voltage source is connected to the inductor, while the MOSFET serves as a switch that opens and closes based on gate terminal signals When a high-level square wave is applied to the gate, the MOSFET closes, allowing current to flow; conversely, it opens when the gate receives a low-level square wave.
The MOSFET allows electricity to flow, connecting the inductor L to the negative terminal of the power supply This connection enables a current to travel between the positive and negative terminals, gradually increasing from an initial value As the current flows through the coil L, it accumulates energy in the form of a magnetic field, while minimal current circulates through the rest of the circuit during this phase.
Figure 2.9: When MOSFET switch on
When the MOSFET is turned off, the circuit becomes active, causing the coil L to generate an inductive voltage that opposes the reduction of current The voltage polarity across coil L reverses compared to when the MOSFET was conducting, resulting in two voltages in series: the supply voltage V and the voltage V across the coil L This combined voltage (V + V) forward-biases the diode D, allowing the generated current to flow through D, charge the capacitor C to a value of V + VIN L minus the voltage drop across D, and supply power to the load.
Voltage regulator circuit
A voltage regulator is a crucial component in power supply systems, ensuring a constant output voltage despite fluctuations in input voltage Various types of voltage regulators exist, including Zener, series, shunt, fixed positive, IC, adjustable, negative, and dual tracking, each capable of maintaining a stable DC output voltage regardless of changes in input or load conditions This project focuses on the implementation of a series voltage regulator.
The block diagram in Figure 2.10 illustrates the fundamental structure of a series regulator circuit, where the series element regulates the input voltage reaching the output A feedback circuit samples the output voltage and compares it to a reference voltage to ensure proper regulation.
When the output voltage rises, the comparator circuit generates a control signal that prompts the series control element to reduce the output voltage, effectively stabilizing it.
When the output voltage drops, the comparator circuit generates a control signal that prompts the series control element to boost the output voltage, effectively stabilizing it.
Figure 2.10: Series regulator block diagram
DESIGN AND IMPLEMENTATION
Block diagram
Figure 3.1: Block diagram of Footstep power generation
Figure 3.1 illustrates the block diagram of a footstep power generation system, which consists of several key components: a piezoelectric sensor, a full wave bridge, a boost converter, a voltage regulator circuit, and a charge circuit.
Piezoelectric materials function as sensors by converting applied pressure, such as that from moving vehicles or pedestrians, into electrical energy The energy generated varies with each object's weight, resulting in an unstable output To address this variability, a bridge circuit is employed to transform the fluctuating voltage into a linear signal Additionally, an AC ripple filter is utilized to eliminate any extraneous fluctuations, ensuring a smoother waveform for more consistent readings.
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
Piezoelectric materials convert applied pressure, such as that from moving vehicles or pedestrians, into electrical energy Due to the low power output from a single piezo film, researchers explored combinations of multiple films using both parallel and series connections While the parallel connection showed minimal voltage increase, the series connection resulted in higher voltage output, albeit not in a linear fashion Therefore, a hybrid approach combining both configurations was utilized to achieve high current density Since the current generated by piezoelectric transducers is alternating, a full-bridge rectifier, consisting of four diodes, is employed to convert this AC output into stable direct current The electrical energy produced is typically around 3 volts, insufficient for directly charging a 6V battery, so a boost converter circuit is used to elevate the voltage to 6V Additionally, the output from the bridge rectifier contains ripples, which can be smoothed by incorporating a Zener diode at the output, ensuring a more stable voltage supply.
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
The simulation circuit demonstrates that varying gravitational forces on the sensor can alter voltage levels; however, these voltages are minimal Therefore, a booster and voltage stabilizer circuit is essential to charge a storage battery, enabling it to supply power for lighting operations.
In conclusion, our project highlights the significant potential of harnessing wasted kinetic energy as a renewable energy source due to its abundance and eco-friendliness This innovative approach can generate substantial electrical energy, particularly in densely populated areas, making it ideal for applications such as street lighting and charging ports, all without the need for extensive power lines Additionally, it can enhance the illumination of buildings along pavements, promoting a sustainable and efficient energy solution.
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.