THE 8th INTERNATIONAL SYMPOSIUM ON ADVANCED TOPICS IN ELECTRICAL ENGINEERING May 23-25, 2013

Bucharest, Romania

The Automation of a Sustainable Billboard Management System

Bulgaru Andrei

Faculty of Electrical Engineering, Univeristy POLITEHNICA of Bucharest, Romania bulgaruandrei90@gmail.com

Abstract- This paper presents an improved and easy-to-use solution for an automated management system of a sustainable billboard. The main purpose of this application is to produce a self –sustainable system that will ensure the rotation of the billboard throughout the day. Using an intelligent solar tracking system and state of the art automation equipment, this model was created as a professional solution that meets the requirements and fulfills the aims initially set. The display can be seen from any point of the campus and it is self-sustainable, using only green energy. Keywords: Industrial automation, LED Display, tracking photovoltaic systems, optimal control. Introduction

I. INTRODUCTION

The Industrial Revolution [1] brought about, not only the manufacturing and automation processes that made the industry possible, but increasing the income for the people, which fostered the consumer culture. Sales and economy go hand-in-hand [1]. This came as a response to the need of maintaining high quality standards, ensuring safety requirements and managing new and more complex industrial processes. Industrial automation’s primary objective is to grant a more flexible and low cost approach, in a safer, more effective and faster way. A billboard [2] is a large outdoor advertising structure (a billing board), typically found in high traffic areas such as alongside busy roads. Billboards present large advertisements to passing pedestrians and drivers. Typically showing large, ostensibly witty slogans, and distinctive visuals, billboards are highly visible in the top designated market areas [2].The whole purpose of the billboard is to enhance the information distribution process, making it faster and more cost efficient, while maintaining its functionality (converting potential buyers into long-term clients). [3] Modern world bombs us with advertisements on every step: at home in front of a TV, while browsing on the internet or during a walk around a city. Advertisements are everywhere. Every day new ones come in different shapes and sizes. Can this process be supported and automated by a computer [3] ? Of course it can! Using LED technology and a tracking PV system, it is within our power to design a sustainable green energy system. The most important aspect of the billboard industry is the evolution of the LED technology. LED stands for "Light Emitting Diode" and, although it started being used at a small scale (decorations,

toys, etc.) now LEDs are beginning to be considered the future of lighting.

Fig. 1. Overview of the entire Structure and Bonding situated on the Polytechnic University’s rooftop.

II. OUTDOOR LED DISPLAY

Financial considerations-namely, purchase price and operating costs-always figure in the selection of lighting products, but many other aspects also come into play, varying in importance depending on the application. LEDs have several unique attributes, and it is critical to understand how they can be used advantageously.

The chosen model for this application was a long distance outdoor LED panel (Fig. 3) which has an estimated Visibility

Distance of over 400 m in normal weather conditions. It will be programmed using the PLC to display user defined messages, the clock and the ambient temperature. The application is designed for the most important building of

Fig. 2. The solar panel supporting system of solar the tracker.

978-1-4673-5980-1/13/$31.00 ©2013 IEEE

Polytechnic University of Bucharest, purposely its arched rooftop.

III. PV SYSTEM

Photovoltaic systems (PV systems) use solar panels to convert sunlight into electricity. The current system is made

Fig. 3. The Outdoor LED panel. of 18 photovoltaic panels, the rotating structure, electrical interconnections, the battery system and the solar tracker and energy management software which are embedded into the PLC. This small PV system may provide energy to power up the motor and automation equipment.

The electricity generated can be stored in the NiMH batteries, used directly, or fed into a large electricity grid powered by central generation plants (grid-connected/grid-tied plant).

A solar tracker is a device that orients various payloads toward the Sun (in this case photovoltaic panels).

[4] In flat-panel photovoltaic applications, trackers are used to minimize the angle of incidence between the incoming light and a photovoltaic panel. This increases the amount of energy produced from a fixed amount of installed power generating capacity. In standard photovoltaic applications, it is estimated that trackers are used in at least 85% of commercial installations greater than 1MW from 2009 to 2012 [4]. The type of PV panels chosen in this current application is monocrystalline silicon cut cells (model BP440J) designed by BP Solar, a company which [5] has been pioneering photovoltaic (PV) solar for almost 40 years. This experience shows that the best way to optimize module life and electrical

energy production is to attend to every detail in the design and manufacture of our products, our process controls and testing methods [5].This model was chosen for the system’s design & dimensioning because it provided a detailed technical datasheet, which helped improve the overall simulation results.

IV. INDUCTION MOTOR

The utilization of squirrel cage induction motors with electronic inverters [6] presents great advantages regarding costs and energy efficiency, compared with other industrial solutions for varying speed applications. Nevertheless, the inverter affects the motor performance and might introduce disturbs into the mains power line. PWM voltage source static frequency inverters presently comprehend the most used equipment to feed low voltage industrial motors in applications that involve speed variation. They work as an interface between the energy source (AC power line) and the induction motor [6].

This kind of application (with an induction motor fed by PWM inverters operating in variable speed duty) was chosen in order to ensure a steady 10 rpm rotational speed. The aim was to use two AC induction motors (one to pull and one to push) with a Speed at Full Load of maximum 1500 rpm. This requires a good understanding of the whole power system, the automation of the system, as well as the interactions among its parts one another (power line – frequency inverter – induction motor – load). Thus, the batteries give energy to the AC induction motor which, using the Slewing Gear Transmission and the Slewing Ring, rotates the platform that has built-in the Outdoor LED panel and the PV system. In this application, NiMH battery was chosen using the Ragone chart (also called Ragone plot - Fig. 6) which is a chart used for performance comparison of various energy storing devices. On such a chart the values of energy density (in Wh/kg) are plotted versus power density (in W/kg). Both axes are logarithmic, which allows comparing performance of very different devices (for example extremely high, and extremely low power).

The system is similar with the one used for The General Motors EV1 (an electric car produced and leased by the General Motors Corporation from 1996 to 1999)and it was

Fig. 5. The Slewing Gear Transmission (right) and The Slewing Ring (left).

Fig. 4. The monocrystalline silicon PV model BP440J.

the first mass-produced and purpose-designed electric vehicle of the modern era produced by GM. It consists of the following: AC induction electric motor, IGBT power inverter and NIMH batteries. [7]A nickel–metal hydride battery, abbreviated NiMH, is a type of rechargeable battery that is very similar to the nickel–cadmium cell (NiCd).

Fig. 6. The Ragone Chart.

NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, being in essence a practical application of nickel–hydrogen battery chemistry. A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and their energy density approaches that of a lithium-ion cell. The typical specific energy for small NiMH cells is about 100 Wh/kg, and for larger NiMH cells about 75 Wh/kg (270 kJ/kg). This is significantly better than the typical 40–60 Wh/kg for NiCd, and similar to the 100-160 Wh/kg for lithium-ion batteries. NiMH has a volumetric energy density of about 300 Wh/L (1080 MJ/m³), significantly better than NiCd at 50–150 Wh/L, and about the same as lithium-ion at 250-360 Wh/L. NiMH operates at 1.2 V per cell, somewhat lower than conventional 1.5 V cells, but will operate most devices designed for that voltage [7]. For the battery charger management system, a Microchip PIC12F683 microcontroller was used that has an implemented function for this kind of operation. The 24V battery array can be charged and provide energy to the inverter (that will convert from DC to AC in order to power up the frequency inverter and thus the motor) and to the PLC,powering up the automation part of the application.

V. SYSTEM AUTOMATION

The chosen solution for the PLC (Programmable Logic Controller) was an improved and easy-to-use model produced by Unitronics, the Vision 350. This is actually an OPLCTM (Operator panel PLC), as the manufacturer states, because it is an all-in-one control solution, integrating the PLC and the HMI (Human Machine Interface) in one single, compact device. The system will acquire data from two light intensity sensors, a wind sensor and a temperature sensor. These, plus the 2 encoders inputs received, totals up to a number of 6 analog input ( required by the PLC). Therefore it is necessary to add some extension modules to the initially chosen PLC.

Fig. 8. The system’s functionality described using Block Diagrams.

The V350-35-R34 has only 20 digital inputs and 2 digital outputs, so a Snap-In module will be added:V200-18-E4XB. This module has 18 npn/pnp isolated Digital Inputs (including 2 Shaft-Encoders inputs),4 Analog Inputs 12-14 bit 0-10V, 4-20mA and/or 4 TC/PT100 Temperature Measurement Inputs, 17 isolated npn/pnp Digital Outputs (including 2 High Speed) and 4 12-bit 0-10V,4-20mA isolated Analog Outputs. This current configuration fits the system’s need for the current sensors (given the fact that all of the devices have 4-20mA outputs). After that, if further I/O are needed ,there will be added an I/O Expansion Module Adapter EX-RC1 and, one by one, added a complementary I/O module at a time, so it will meet the system’s requirements perfectly. After the installation of the Expansion module, up to 8 I/O Modules can be installed. These modules are mounted easily on the DYN rail, making the system scalable and easy to extend at any given time, thus reducing costs significantly.The communication protocol is CAN bus. CAN bus (for Controller Area Network) is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other within a vehicle without a host computer. CAN bus is a message-based protocol, designed specifically for automotive applications but now also used in other areas such as aerospace ,industrial automation and medical equipment. The software considered for this application is VisioLogic, it is free and it can be downloaded

Fig. 7. The Slewing Gear Transmission (blue) and The Slewing Ring (pink).

at any given time from the official website. It uses Ladder Diagram, the mostly used PLC’s programming language. When a PLC is used primarily to replace relays, timers, and counters, it is hard to beat the simplicity and usefulness of ladder diagram programming. Due to the fact that all the sensors’ outputs are 4-20mA, there had to be found a way how to make the Data Acquisition as effective and precise as possible .So the first step is a filter, located on the FB (Function Block) menu, that enables you to take from 4 to 16 values and calculate an average.You can influence the average by configuring the function to discard a user-defined number of maximum & minimum input values or to weight the average according to the order of the input values(FIFO).

Fig. 9. Example of how the Filter works.

In this application, the first method was used and 10 values were selected. In Fig.9, Filter Calculate is linked to the configuration Filter_1. In this configuration, Parameter 1: Filter type is Dynamic Average; Parameter 2: Number of Values is 8; and Parameter 3: Discard Values is 2. MI 0 provides the input values. Each time Filter: Calculate is activated, the value in ML 0 is copied to the vector of the linked Filter Configuration,. In this example, 10 values are collected. As each new value is input, the oldest value is shifted out. Since Discard Values is 2, the 2 lowest and 2 highest values are discarded. The remaining values are summed, and then averaged (30+40+50+60=180/4). The result is 45, which is output to ML 0.The Filter Configuration holds the parameters that determine how the input values are averaged, therefore it must be activated before the Filter: Calculate function is called.Each time the Calculate function's activating condition is turned ON, the function's Input parameter is copied to the vector of the linked Filter Configuration, the average is calculated, and the result is placed in the linked output operand. The output value is overwritten each time the function is activated, thus he is not allocated PLC memory. The values are stored in the function (Stack-based solution). For the initialization of the Filter Configurator the program is using a System Bit (SB 2) which turns from 0 “logical” to 1 whenever the PLC is turned On. Given the fact that we have multiple sensors, the program

will use the same procedure to acquire the data from them every time the PLC is powered on. For the initialization of the Filter Calculator the program is using a System Bit (SB 13) which turns from 0 “logical” to 1 whenever the signal has a

Fig. 10. Example of how the Filter calculator works like a Stack.

Fig. 11. The Filter Configurator that provides data to the Filter Calculator.

rising edge (a transition from low to high). It is also named positive edge. When a circuit is rising edge-triggered, it becomes active when its clock signal goes from low to high, and ignores the high-to-low transition.If the process needs to acquire data faster in order to provide a faster response, SB 15 should be used. Until now, the signals received from the sensors passed through the filters. Now,each and every one of them receive a Personalized Function Block: Linearization .As shown above in Fig. 16,this block contains the scale of the measured signal (the minimum and maximum value of the scale),the measurement unit and the bit that provides the output that will be used further in the program. All the selected sensors have the same 24V DC Source and a 4-20mA output. They are the following:

• Temperature sensor :Pt100 Outdoor/Cold Store • two encoders : Kuebler D5.2102.2424.1000 • Wind sensor: DIR21+/4 - 20 mA • two light intensity sensors: Li65 – Outdoor

The two AC induction motors (one is used to pull the structure and one to push) are equipped with encoders that ensure that the motors are synchronized. If one moves too fast, than the encoder will send to the PLC a signal greater than the signal received from the slower motor. In the program, the first operation is to compare the two, then to subtract the smaller signal from the greater one. If the difference between the two is significant (this reference will be set after several experimental tests), it will be multiplied

with a factor K (also set after several tests) and the result will be added to the motor that moves slower. If the difference between the two is too big or if after an elapsed interval the two motors won’t synchronize, both will be shut down and a system fault message will be displayed.

Also, if it is too windy, the motors will also be shut down. The wind should be at all times within a safety range for the system to be running.If all is functioning within normal parameters, the structure will rotate itself, like a sunflower. The solar tracker uses the following principle: two light intensity sensors, one on each arm of the structure. The algorithm is similar to the one used in the encoder’s case: we compare the two signals and we subtract the small one from the greater one. The only difference is that, in this case, if the difference is significant, the motors will start to move the structure until the difference is null.

Fig. 12. P&ID - Piping and Instrumentation Diagram.

The temperature sensor will be used to display the recorded value on the Outdoor LED display. Also, if the temperature is too high, the PV panels will overheat and produce less energy. In order to prevent and to obtain a certain degree of self ventilation, the motors will spin the structure faster.The aim in this situation is to find the right ratio between the amount of energy spent rotating the structure faster and the amount of energy lost from the overheated PV system. Therefore, the difference of the two signals will be compared to a third value which will be obtained from several experimental tests (because if it moves extensively, it would run out of energy).

VI. CONCLUSION

This paper suggests a control method of a rotating LED display billboard situated on the top of a building. Using sensors, the controller predicts the system evolution as a function of the control inputs and makes decisions accordingly thus ensuring that the photovoltaic system will rotate following the Sun, using a maximum power point tracking algorithm, storing the optimized amount of energy in the NiMH batteries in a controlled rate and assuring that the display indicates the user defined messages, the clock and the ambient temperature. All of these devices are using only green, solar energy. It is the first system of its kind and it is guaranteed to make an impact, changing outdoor advertising as we know it, especially since it grants a very good global power efficiency. As stated before, this system is designed for the Polytechnic University’s rooftop not only because of the solar power potential of the geographical area ([8] one of the most important solar projects was the installation of a 30 kw solar panel on the roof of the Politehnica University of Bucharest that is capable of producing 60 MWh of electricity per year[8]) but also because the school saves electricity and raises students’ energy awareness. [9] The main mechanical structure was presented in Estonia, on march 21st-31st 2013, at the Ideal Eco-city: imagine, create, promote! [9]

REFERENCES [1] D.Grager, “A Century of Candy Bars: An Analysis of Wrapper Design”

Accessed 3-3-2013 [2] Frederic P. Miller, Agnes F. Vandome, J. McBrewster ,“Billboard: Out-

of-Home Advertising” Accessed 16-3-2013 [3] M. Jakop, “System for automation of billboard management” Accessed

3-2-2013 [4] J. Roberts, “Tracking Systems Vital to Solar Success” Accessed 4-3-

2012 [5] 40W Photovoltaic module BP 440J. ©BP Solar 2010. Available:

http://powerupco.com/site/wpcontent/files/Solar% 20Modules/BP%20 Solar/BP%20440J.pdf

.[6] K. Siddiqui, Dr.V.K. Giri,” Modelling and Detection of Rotor Broken Bar Fault using Induction Motor Fed PWM Inverter” IJCST Vol. 3, Issue 1, Jan. - March 2012

[7] (2011) "Ni–MH Batteries Technical Bulletin".Retrieved 4 November 2011.[Online].Available:http://www.giesseimpianti.com/index.php/nickelmetal-hydride-battery

[8] CENTRALA FOTOVOLTAICA DE 30 kW" (in Romanian). Asociatia Generala a Inginerilor din Romania. 2006. Retrieved 2009-02-25

[9] A. Bulgaru.(2013) “Sustainable Billboard :Showcase & Innovation”,in Ideal eco-city,Tallin,Estonia.[Online]. Available: http://www.synergyforyou.ro/proiecte/ideal-eco-city-imagine-create-promote-youth-exchange-estonia-21-31-march-2013.html