Renewable Energy Harvesting System Engineering Essay
The demand for fossil fuels has been on the rise for decades. Since the advent of the industrial revolution, the worldwide energy consumption has been growing steadily. There is little doubt the world is running out of fossil fuels. We’ve known it for some time. At current production rates, global sources of oil and gas will be exhausted within 40–60 years.
Burning fossil fuels creates another grave problem: global warming. The Earth is already showing many signs of worldwide climate change. The 20th century’s last two decades were the hottest in 400 years and possibly the warmest for several millennia, to a number of climate studies. Glaciers are rapidly melting — Industrialization, deforestation, and pollution have greatly increased atmospheric concentrations of water vapor, carbon dioxide, methane, and nitrous oxide, all greenhouse gases that help trap heat near Earth’s surface.
Energy harvesting is the process by which energy is derived from external sources (e.g., solar power, thermal energy, wind energy etc.) then stored. "Fuel" for energy harvesters is naturally present and is therefore considered free. The energy produced from these fuel or sources can be stored in a capacitor, super capacitor, or battery. Batteries leak less energy and are therefore used when the device needs to provide a steady power flow
The hybrid system is used due to the fact that we could easily switch between our resources to make most of them. When there is the access of wind we can use it in place of solar and when the sun is closer to the equator the solar energy could be exploit.
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The paper organization is such that the section I will provide the information about the basic components of the system then the section II would explain the operation, section III is about the results and discussion and finally section V is the conclusion.
SECTION I: Basic Building Blocks of the system
Wind power is produced by using wind generators to harness the kinetic energy of wind. A wind turbine is a rotating machine that converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill but when the mechanical energy is converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU), wind energy converter (WEC), or aero-generator.
The wind speed of some of the cities of Pakistan is stated in table 1, which shows that high electrical power can be derived from the wind energy.
Table 1: Speed of Wind in different Months of the year.
SPEED (in m/s)
The wind turbine is a mechanical transducer that converts mechanical energy into electrical energy by the principle of moving an electrical conductor into the presence of magnetic field. The detailed design description of the turbine is given below.
Turbine blades are made stiff to prevent blades from being pushed into the tower by high winds. We are selecting diameter of ~2 meters because wind power formula is:
P= η x D2 xV3 (1)
η = Efficiency Factor of Generator
D = Diameter of Turbine in meters
V = Velocity of Wind in m/s
Taking, η = 0.5, D = 2m, V=4m/s
P = 128Watts
When power is being transmitted through a shaft, a torque T will be present. This torque is given by:
T = P/ω (2)
P = Power in watts
ω = Angular velocity in rad/sec .
T = Torque in N.m /rad.
The generator is the unit of the wind turbine that transforms mechanical energy into electrical energy. The principle is electromagnetic induction. Wind application requires low RPM, high torque generator since wind blows at slow speeds, but larger diameter turbine can produce more torque from same wind.
An anemometer is a device for measuring the wind speed, and is one instrument used in a weather station. The term is derived from the Greek word anemos, meaning wind. Leon Battista Alberti gave the first known description of an anemometer in around 1450.
Anemometers can be divided into two classes: those that measure the wind's velocity, and those that measure the wind's pressure; but as there is a close connection between the pressure and the velocity, an anemometer designed for one will give information about both.
This work is to make use of solar power in productive and efficient way that can readily be implemented in its targeted areas. Solar power is by far the Earth’s most available energy source, easily capable of providing many times the total current energy demand. Solar power is the conversion of sunlight into electricity. Two main commercial ways of conversion of sunlight into electricity
Concentrating Solar Thermal Plant (CSP).
Photovoltaic Plants (PV)
PV is very successful in decentralizes applications.
A solar cell or photo voltaic cell is a device that converts solar energy into electricity by photovoltaic effect. Photovoltaic is the field of technology and research related to the application of solar cells or solar energy. Photovoltaic comes from the words photo meaning light and volt, a measurement of electricity.
It is the line of world’s fastest growing energy technology. Solar cells have many applications. Individual cells are used for powering, small devices such as electronic calculators; photovoltaic arrays generate a form of renewable energy.
An electrical inverter that converts DC power stored in batteries to AC power that can be used as needed. The size of an inverter is measured by its maximum continuous output in Watts. This rating must b larger than the total Wattage of all the AC loads planned to be operated at one time. The size of the inverter can be minimized if the number and size of the AC loads is kept under control. If the inverter is expected to run induction motors it must be designed to deliver power many times of its ratings for short period of time while these motors starts.
In an inverter, direct current (DC) is switched back and forth to produce alternating current (AC). Then it is transformed, filtered and stepped to get it to an acceptable output waveform. They are relatively inexpensive, and many of the electrical devices we use every day work fine on them.
Section II: System Operation
The block diaagram of the system is shown in figure 1. The flow chart for the system operation is described in figure 2.The power generation comprises of two main systems, Wind system and solar system.
Relay Interface Board
Main Controlling System
Wireless Communication Module
Lab View HMI
Charge Controller/ Monitor
Power DC-AC Inverter For AC Loads
STORAGE & OUTPUT
Figure 1: Block diagram of the System
The wind system comprises of generator, blades and yaw. The three bladed rotor is the most important and most visible part of the wind turbine. It is through the rotor that the energy of the wind is transformed into mechanical energy that turns the main shaft of the generator. The wind is moving towards the blade, at a right angle to the plane of rotation, which is the area swept by the rotor during the rotation of the blades. The wind speed will produce a wind pressure at blade surface. The wind pressure is roughly in the same direction as the wind and is also roughly perpendicular to the flat side of the blade profile. The direction of the wind is determined by the yaw attached at the tail end of the turbine system. As the wind hits the blades the torque is produced which then rotate the shaft, the blades are bolted on to the hub, which is coupled, to the shaft of the generator. The magnet rotor disk is mounted on the bearing hub so that they can rotate the shaft. Electricity is generated when the magnets on the magnet disks rotate past the coils embedded in the stator casting. The magnetic field induces a voltage in the coils, which is ultimately fed to the ADC0808 as an analog data.
Initialization of hardware connected to microcontroller
Set Default O/P values and Serial Baud rate
Configure Wireless Module
Handshake With HMI
ADC Conversion Cycle
Save Data from ADC to Memory
Send Data from memory to Wireless Module
Command Received from HMI?
Process Received Command
Figure2: Flow Chart of the System
Solar power is the generation of electricity from sunlight. This can be direct as with photovoltaic (PV), The solar power gained from photovoltaic can be used to eliminate the need for purchased electricity, the energy obtained from the solar panel is directly fed into the second channel of ADC0808.
The Anemometer uses the third channel of ADC 0808 to measure the speed and the direction of the wind mounted on the same tower of the wind turbine. Not only this, we are recording the temperature of the environment as well. This is done though LM35, is connected to the non-inverting operational amplifier provide the gain. The output of the operational amplifier is connected to the 4th channel of ADC 0808.
ADC0808 has eight channels. It is connected to the one port of the microcontroller. It is used to convert the analog input values coming from its channels to digital output values. The microcontroller selects the channel on the ADC0808 one by one and stores the digital values in its memory. Second port of the microcontroller is connected to the relay interface board. The relay interface board is used for switching between wind and solar power systems. In auto mode, the microcontroller compares the output power between the solar and wind power system and selects the one with the highest power. The third port is used for the serial transmission with the Bluetooth module to send the system status (battery status, output power of the wind and solar power system, temperature, wind power, etc) to the central station terminal.
The charging and monitoring circuits are also connected to the microcontroller. The microcontroller monitors the voltage of the battery(s) in the system and either sends power from the wind or solar power system into the batteries to recharge them, or transfer the power from the wind or solar power system into a secondary load if the batteries are fully charged (to prevent over-charging).
SECTION III: Software Control
The wireless communication is done through Bluetooth module wirelessly showing the power produced by the wind turbine and the solar panel, the temperature of the environment, status of the battery, speed of the wind on HMI via LABVIEW. The main function also includes the manual switching between the wind power and the solar power systems from which we can easily control our plant from central station location.
Figure 3: Human Machine Interface(HMI)
LABVIEW is a graphical programming environment used by millions of engineers and scientists to develop sophisticated measurement, test, and control systems using intuitive graphical icons and wires that resemble a flowchart. LABVIEW offers unrivaled integration with thousands of hardware devices and provides hundreds of built-in libraries for advanced analysis and data visualization. Figure 3 shows the HMI front panel that has been designed on LABVIEW.
SECTION IV: Results & Discussion
Figure 4 shows a graph for the power generation of the wind turbine in each month of the year. The average power obtained in a month is plotted in horizontal axis as shown in the figure. The “Avg” in a graph represents the average power in a year while the “Min” and “Max” shows the minimum and maximum power a year respectively.
Figure 4: Average Power generation of the wind turbine in a year.
SECTION V: CONCLUSION
The current interest in the wind and solar energy were started by need to help clean, sustainable energy system that can be relied on long-term future. They now provide reliable, cost effective, pollution free energy for individual, community and national applications. So by using this economical energy nation can grow up with more increasing speed.
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