The design of the proposed hybrid green power supply system based on solar panels and windmill takes advantage of both natural resources of energy to charge batteries. The hybrid system is interfaced through a micro controller that takes input from solar power as well as windmill to charge batteries for powering appliances through inverted set. The system provides some design constraints that must be met for effective utilization of natural resources for harnessing energy. In this section, we will analyze the design concept and associated challenges.
The microcontroller provides interface to natural resources by taking input in terms of analog voltage. The windmill provides varying voltages through a synchronous generator whose rotor is connected to the wind turbine. The solar power system utilizes solar panels to produce voltages on photovoltaic cells. These cells are connected as analog input to the microcontroller. This system provides two variables DC power supplies for feeding battery connected as output with the microcontroller. The output of the microcontroller will be fed to the battery in terms of analog voltages. The overall circuit implementation is shown below:
Figure 1: Overall Layout of Circuit
The main challenge of the proposed design is voltage synchronism. The natural resources would be producing variable voltages are different standards that contain fluctuations due to variation in the solar intensity as well as wind speed. The voltage fed to the battery should be uniform within a certain range. This design consideration is met through a voltage regulator that produces constant output voltage for a given certain range of analog input voltage. The variations in wind speed and the Sun’s intensity will not severely affect the operation of the battery charging system.
Another design constraint is the control system for generating power from wind turbine and solar panels. The control system for wind turbine will consist of speed regulators and limiters for maintaining speed of the rotor of the wind turbine in a certain range. The output voltage of the stator of the synchronous generator will be maintained through controlled rectifiers. The variation of wind on a certain scale will not affect the output voltage of the system used for charging batteries. The control circuit of the windmill is shown below:
Figure 2: Control Circuit of Windmill
Similarly, the controller for the solar system is realized through rotating panel for gathering the maximum intensity of the Sun (Mousazadeh, 2009). The control feature of the system is to optimize the Sun’s intensity in a given place. The small variations in the Sun’s radiation will be regulated at the output of the microcontroller feeding the battery. However, the large variations will be minimized through rotating panel and inherent voltage control mechanism of photovoltaic cells (Mousazadeh, 2009). The rotating panel is realized through a servo motor whose rotation is programmed to receive the maximum intensity of the Sun. The servo motor control could also be programmed through the microcontroller used as interface.
The analysis of the design concept shows that it optimizes the utilization of natural resources since it increases the reliability of the system. It comprises multiple sources of energy so that if one fails, the other would act as the backup source. Moreover, the sources of energy are different so that they don’t suffer from the same type of failure like Solar panels will not work a night but windmills will continue to operate and charge batteries. The overall design maintains redundancy and diversity in terms of the power production.
Description of Test Bed
The test bed comprises the hardware and software of the system. The components of the system are tabulated below:
• Atmel Atmega328 microcontroller for input from hybrid resources of energy and output in the form of digital voltage after adding the voltages from both wind turbine and solar panels. It is basically the backbone of this system that provides decision making capabilities. The controlling mechanism is ensured in the software. The addition of the voltages obtained from the two sources is also performed in the software.
• Solar panels with rotating controllers for optimizing the Solar intensity for keeping the voltage within a given range. The controlling feature of the solar cells is provided by the rotating panels mounted in the servo motor controlled through the microcontroller. The times of the day in which the maximum intensity of the Sun is available, the servo motor tries to harness as much energy as possible.
• Wind turbine for harnessing wind energy through magnetic coupling between stationary and rotating part. The controller is available for maintaining rotor speed and voltages of the stator.
• The voltage regulator available at the output of the microcontroller for producing voltages for charging a 12V battery. The voltage regulator is a simple Zener diode that produces constant output for a given range of input.
• The digital to analog converter for output of the microcontroller before feeding to charge 12V battery. The output of the microcontroller is in the form of digital voltage that must first be converted to the analog output for charging batteries.
• LCD for displaying the voltages produced from the hybrid system. It provides monitoring option for operation and maintenance of the system.
• The power supply set for running the microcontroller. The power supply is AC source rectified to DC and then used for powering the microcontroller that typically runs on standard between 5V to 10V.
• C programming language environment and compiler as software tools for programming the microcontroller for performing the desired functions.
The experimental setup of the designed circuit is as shown below:
Figure 3: Experimental Setup
This experimental setup provides the required circuit configuration in terms of required hardware components. The wind turbine output from the stator terminal is connected to the input of the microcontroller. Then it is converted to digital input through built in A/D converter. In the similar fashion, the output of the solar panels is input and converted to digital format in microcontroller. The controllers of solar panel and wind turbine provide efficient energy harnessing. The output voltages of solar energy and wind turbine energy are added up to boost charge the battery. It wouldn’t be possible to charge battery in as fast manner as in this configuration with the single source of energy. The hybrid circuit configuration enhances the charging speed while still maintaining the desired control. The output of the circuit could charge a number of batteries in parallel if we employ large size wind turbines and solar panels.
The purpose of individual components and equipment is already described in the previous sections. The heart of the circuit is the microcontroller that is programmed to take input from the two sources of energy, convert them into digital version, add them, and then output the voltage in digital format to the D/A converter. The analog output is then regulated finally to charge batteries. The final output is the combination of that obtained from the solar panels and wind turbine power generation. At the end, the circuit is fabricated on the printed circuit board. The layout of the printed circuit is shown below:
Figure 4: PCB Layout
Results and their Evaluation
The performance of the experimental setup can be realized in the light of the following experimental results:
• The output voltage from the microcontroller is digital and varies only slightly between 11V and 13V that is ideal for regulator to keep it constant at 12V. The small variations in the output of the circuit are attributed to the fluctuations in the wind turbine output and solar panels even though they have their own controllers. The charging time of the battery varies depending on the strength of the natural sources. During times of high wind velocity and the Sun at its peak, the output of the circuit is very high and consistent. The charging time would be very small in that case.
• The individual energy sources are tested independently for checking whether they provide correct input to the microcontroller for charging battery. The output of the solar panels and wind turbine are tested to provide the same voltage standards so that they are synchronized. The inputs obtained from both sources are added in software and output to the digital output of the microcontroller.
• The performance of the software program is assessed in the C programming environment debugger. The code is run in modules to check whether each component is behaving in the desired manner.
• The controlling mechanism of wind turbines and solar panels are also tested to check whether they regulate the output of the corresponding energy source in case of variation in the intensity of Sun light and wind speed. The rotating solar panels mounted on the servo motor and control axis/voltage regulator of the wind turbine behave in the desired manner.
The table showing the detailed hardware components is provided below. The references of the circuit components could easily be found in the detailed circuit diagram of the project showing all hardware components.
Table 1: Hardware Component Specification
Category Quantity References Value
Capacitors 1 C1 470uF
Capacitors 1 C2 10uF
Capacitors 2 C3-C4 22p
Capacitors 1 C5 10uf
Capacitors 1 C6 470 uF
Capacitors 1 C8 100n
Resistors 1 R1 330R
Resistors 2 R2,R7 15K
Resistors 3 R3-R4,R6 10k
Resistors 2 R5,R8 4.7K
Resistors 2 R9,R14 4.7k
Resistors 2 R10,R15 47k
Resistors 1 R11 1k
Integrated Circuits 1 U1 ATMEGA328
Integrated Circuits 1 U2 7805
Integrated Circuits 1 U4 LM358
Transistors 1 Q3 IRFz44
Diodes 2 D1,D4 DIODE-LED
Diodes 3 D2-D3,D6 1N5408
Miscellaneous 1 BATTRY 2 pin
Miscellaneous 1 BR1 W04G
Miscellaneous 1 BR3 2W005G
Miscellaneous 2 J1,WINDMILL 2 pin
Miscellaneous 1 J2 12V Solar Panel
Miscellaneous 1 J3 male berg
Miscellaneous 1 LCD1 10u
Miscellaneous 1 RES SW button
Miscellaneous 1 RV1 10K
Miscellaneous 1 X1 16mh
The overall performance of the designed circuit on software environment and hardware platform shows that it charges the 12V battery in quite an efficient manner. The circuit exhibits robustness against natural disturbances in the wind turbine and solar panel parameters. The effects of disturbances and variations in the parameters don’t significantly affect the output of the circuit. The performance of the voltage regulator connected at the analog output of the circuit prevents fluctuations in charging supply of the battery and provides constant voltage for healthy charging system.
The overall setup of the circuit in the hardware is presented in the following images. These images show the practical implementation of the overall designed circuit on hardware.
Figure 5: Real Hardware Screenshot 1
Figure 6: Real Hardware Screenshot 2
Figure 7: Real Hardware Screenshot 3
The main contribution in this research project is designing a robust hybrid technology comprising solar energy and wind energy for charging batteries. This circuit is innovative in the sense that the sources of the energy act independently in terms of all operations including control. The outputs of the individual sources could easily be added up for providing reliable DC power supply for charging 12V battery. The environmental footprints of the proposed circuit are minimized considering the green sources of energy.