Wireless Control of a Self-Sustained Solar Power

Generation System

Fatima Adly, Nourhan Bayassi, Rola Mahainy, Rawan Al-Kurd, Ghada Shubair

Supervisors: Dr. Reyad El-Khazali, Dr. Ibrahim Abualhaol

Electrical and Computer Engineering, Khalifa University

The solar power generation system is designed to be simple, practical, and efficient. The system is capable of utilizing the most of the solar energy and aiming it to a heat exchanger placed on a top of a receiver. The design of the system is shown in Fig.1

SYSTEM DESIGN

INTRODUCTION

• Each Fresnel lens heats up the temperature up to 60℃. • Combining the three lenses, the temperature reaches 150℃, and a steam is generated.

In addition, the user can monitor and read the temperature of each reflector on the GUI. The algorithm of the integration between temperature and position is shown in Fig. 10. The system invests in one of the most important, natural, infinite, green, and

renewable source of energy which solar energy. The main goal is to generate electrical power using solar energy and use it in different applications. The system combines wireless technology along with some computing capabilities to implement a wirelessly-controlled, self-sustained solar power generation system. The sun reflectors used in the system are known as Heliostats. The system is composed of three heliostat models which are used to reflect sunlight to a heat exchanger on top of a receiver tower. Three Fresnel lenses are placed around the heat exchanger to focus the reflected light on one spot. The heat exchanger produces pressurized steam to rotate a turbine-generator unit, and produce electricity. The system is wirelessly monitored and controlled using a proportional-integral-derivative control algorithm. A graphical user interface unit is designed to monitor the whole system using both a PC and a Tablet PC to add mobility to the system. A photovoltaic (PV) solar cell unit is used to generate the necessary power to make the system self-sustained.

The structure and design of the proposed solar heat exchanger is a unique one. Inspired by the use of the greenhouse effect in agriculture and cultivation, the same concept is used in our heat exchanger to preserve the hot environment around the internal components, as can be seen by Fig.3.

There are two prisms; one inside another, the outer one made of special anti-fire glass plays the role of maintaining the greenhouse effect, while the inner one is made of copper. Within the inner copper prism, there is a condenser that plays a similar role to that connected to the fridge compressor, but smaller and shorter.

The three heliostat models are distributed around the circumference of a 2 meter diameter circle, and separated by 120o. The forth model in the above figure represents the brain for the real-time sun-tracking system, and will be placed next to any of the heliostat models.

SUN-TRACKING ALGORITHMS

GPS-based sun-tracking system:

• The main sun-tracking system is based on the GPS location.

• In this mode of operation, the user have the choice of either using one of the

locations which are already stored in the GUI.

• Or, if the location is not available, the user manually enters his location

(latitude, longitude and time zone) and then the Arduino program does all

the necessarily calculations.

• The Arduino program depends on a look-up table that gives the hour angles

in degrees. These angles are used in predefined equations to orient and

move the reflectors with respect to the heat exchanger.

Real-time sun-tracking system:

• The backup sun-tracking system is based on real time tracking algorithms.

• The tracker uses a set of LDRs distributed evenly around a wooden cylinder.

• The tracker measures the incident angel of the sun using an algorithm

based on a comparison process between different values of light intensity.

• The incident angle is used by the microcontroller as an input for a more

sophisticated computing algorithm which calculates the orientation of the

reflectors.

Azimuth and elevation coordinates:

• Each reflector has its own Azimuth coordinate and all the reflectors are

placed in the center point (0,0) of their specified azimuth coordinate.

• The azimuth angel is defined from 0o to 180o counter clock-wise and from

0o to -180o clock-wise.

• The elevation angle is defined from 0o to 90o

MIRROR REFLECTION ALGORITHMS

SYSTEM WIRELESS MONITORING

PC design algorithm: The PC GUI is shown in Fig.8.

Tablet design algorithm:

The Tablet PC is first protected by an encrypted password, which if entered incorrectly more

than three times a trip alarm signal is sent to the PC. Once the password entered is correct,

then the user chooses which heliostat to monitor. The tablet PC monitoring includes also:

Wind protection: Mirrors take a horizontal position so the effect of the wind on the

mirrors is minimized.

Dust protection: If dust level increases above certain level, a light starts to flash.

Manual control to direct heliostat machine in any direction the user wants.

Notes recording facility to help the user to take notes as he/she walks around the site.

IP protection contour: An alarm signal is sent to the PC and the Tablet PC if the Heliostat

field is crossed by strangers.

Some of the application screenshots shown in Fig. 11.

and the general algorithm of the Tablet GUI is shown in Fig.12.

EXPERIMENTAL RESULTS

Figure 1: Design of system

Figure 2: Heliostat mirror design

Figure 3: Design of heat-exchanger

Figure 5: LDRs arrangement & Real—time tracking algorithm

The position of each reflector is displayed on the PC GUI once it has been set. The user has the choice to reset the position manually, or apply a new position. The algorithms of so are shown in Figs9.

Figure 4: GPS algorithm

Figure 6: Azimuth & elevation coordinates

Figure 13: Target position simulation & GPS readings

Figure 8: PC GUI

Figure 9: PC control algorithms

Figure 10: PC temperature readings

Figure 11: User tablet application design

Figure 12: Tablet algorithm & communication with Arduino microcontroller

CONCLUSIONS

The GPS system was compared against a simulation program, in which the time, date and location are input to the system, and the sun and heliostat machine position are output. The simulation results are shown in figure below:

0 5 10 15 20 250

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Hour

Helio

sta

t A

ltitude u

sin

g G

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Simulation

GPS algorithm

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Hour

Heliosta

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GPS algorithm

• Half-way vectors equations are used to find the

target location and to orient the reflect with

respect to it.

• The algorithm depends on the slope direction

to move motors.

• Since the algorithm is based on many

approximations, an RTC is used to make the

calculations more accurate.

Aim