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- Multidisciplinary Digital Publishing Institute
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- © 1996-2019 MDPI (Basel, Switzerland) unless otherwise stated
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- 2075-5309
- DOI
- 10.3390/buildings8090119
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Abstract
buildings Article Smart Solar-Powered LED Outdoor Lighting System Based on the Energy Storage Level in Batteries ID Suhil Kiwan * , Anwar Abo Mosali and Adnan Al-Ghasem Mechanical Engineering Department, Jordan University of Science and Technology, 22110 Irbid, Jordan; anwaraym2012@gmail.com (A.A.M.); adnan100@just.edu.jo (A.A.-G.) * Correspondence: kiwan@just.edu.jo Received: 4 July 2018; Accepted: 29 August 2018; Published: 31 August 2018 Abstract: A novel smart solar-powered light emitting diode (LED) outdoor lighting system is designed, built, and tested. A newly designed controller, that continuously monitors the energy status in the battery and, accordingly, controls the level of illumination of the LED light to satisfy the lighting requirements and/or to keep the light “on” the longest time possible, has been developed. The use of such a reliable solar energy-driven lighting system, with maximum time when the light is “on”, will eliminate the sudden-death of light problem present in conventional photovoltaic (PV) outdoor lights and, therefore, will enhance the natural surveillance and feeling of safety in sustainable buildings and cities. Furthermore, the new smart control eliminates the overdischarge of the system battery and, thus, ensures a longer lifetime of the system battery. Experimental measurements on a system using a 30 W LED light showed that the operating hours of the new system reached 29.16 h (1750 min), while the operating hours for a similar conventional system were 20.86 h (1252 min). Thus, the new lighting system was demonstrated, securing more than 40% of operating hours than the conventional systems. Keywords: solar PV lighting; solar energy; smart lighting system; LED outdoor light 1. Introduction Demand for energy increases more and more as the global population grows, and economies of the developing countries continue expanding and expected to be tripled by 2050. Nowadays, energy resources come from hydrocarbon fuel, which is a finite resource and considered as one of the main reasons for international conflicts [1]. Solar energy is one of the most attractive alternative energy resources for many countries, including oil-producing countries. However, the continuous increase in oil prices is forcing many countries to seek alternative sources of energy, for example, in countries like Jordan, the average daily solar radiation is between 5.5–7.5 kWh/m , with sunshine duration of 3000 h per year [2]. Photovoltaic (PV) technology presents a practical solution for numerous power application problems in isolated areas, as well as in the center of the large cities. Stand-alone PV lighting systems are one of the most common applications of PV. Since using energy-efficient lighting is an important factor for sustainable development and energy strategies, the combination of high-efficiency PV with LEDs allows the release of stand-alone PV lighting systems that provide a practical energy-efficient solution for lighting systems [3]. Wu et al. [4] have presented and investigated the design of solar-powered LED roadway lighting using high power LED luminaries (100 W), and estimated the total cost of installations for a 10 km highway with two lanes. A comparison between LED lighting using solar power and grids, with traditional mercury lamps, regarding cost, found that 75% of energy can be saved by using LED lighting. Considering the payback and lifetime, LED lighting using solar power or grid power were found to be economically feasible. Since energy efficiency is a major concern in designing off-grid Buildings 2018, 8, 119; doi:10.3390/buildings8090119 www.mdpi.com/journal/buildings Buildings 2018, 8, 119 2 of 18 renewable energy systems, [5] have presented a characterization of the potential benefits of using LED lighting and conventional metal halide systems. They found that using LED luminaries is not a direct replacement for metal halide systems when higher levels of luminance are required, since LED light does not provide the same magnitude of illumination as metal halide. However, they presented collected illumination data that may be useful in designing a renewable energy-powered microgrid that uses multiple LED fixtures to illuminate an outdoor area to replace a conventional metal halide system. Costa et al. [6] had suggested an autonomous street lighting system as an alternative for remote localities, such as roads and crossroads. The suggested lighting system was implemented in DC to present high efficiency and scotopic human sensitivity. Huang et al. [7] introduced a high-performance charge/discharge controller for a stand-alone solar LED lighting system. The introduced controller incorporates a near-maximum-power-point operation (nMPPO), pulse width modulation (PWM), battery charge control, and a PWM battery discharge control to drive the LED directly from the battery. A similar performance of maximum power point tracking (MPPT) was obtained with the introduced controller by proper matching between the PV module specifications and the battery. They performed a reliability test for the light decay of LED lamps, which showed that the light decay of PWM-driven LED was the same as that of constant-current-driven LED. Based on this result, the DC/DC converter was removed from the stand-alone solar system to eliminate the DC/DC conversion loss and cost. A simple design for a direct current (DC) regulator has been proposed by Fathi et al. [8], the proposed DC driver was implemented to solar LEDs lamp based on white diodes of phosphorus GaN, and it was applied in a PV stand-alone outdoor lighting system. Energy saving has become a more and more important motivation in illumination, so that a need for light dimming arose to save energy, and became a must. Liu et al. [9] utilized a dimming control method by varying switching frequency in their dimmable electronic ballast. The interface circuit for analog dimming control had been analyzed and tested. The experimental results showed that the ballast could dim the power of high-pressure sodium (HPS) lamp from 33% to 100%, without acoustic resonance, and with an efficiency higher than 90.3% through the whole dimming range. Recently, Kim and Park [10] introduced an alternative design for community street lighting by applying “Crime Prevention Through Environmental Design” (CPTED) concepts to enhance natural surveillance and feelings of safety. They compared these alternatives to existing lighting. Yoomak and Ngaopitakkku [11] developed an analysis of lighting quality for dry and wet road surfaces using the DIALux software, and made a comparison between high pressure sodium (HPS) and LED luminaires. Results show that the HPS luminaires can provide better average illuminance than LED luminaires, however, LED luminaires can achieve better overall visual and comfort performances, including energy saving, due to their light distribution efficiency. Campisi et al. [12] evaluated the feasibility of the redevelopment of public lighting of the municipality of Rome. The consideration of the study was to replace the conventional lamps with LED lamps. They focused on the factors that affect the project, like energy and maintenance cost. Based on real options used to evaluate the economic cost-saving of the project, they reported a reduction on the energy consumption and maintenance cost, lower emission of CO into the atmosphere, and positive effects on the street. Campisi et al. [13] discussed the techno-economic feasibility of replacing the traditional lamps in public lighting in Rome with LED luminaires. They reported, based on the possible energy saving and cost, that despite the cost of the LED luminaires, the use of LED technology is economically feasible. Cucchiella et al. [14] investigated the economics of the photovoltaic energy systems with battery storage for residential areas. They concluded that the benefits of such systems are higher in countries that have high values of solar insolation, and suffer from an excessive energy cost and a strong dependence on imports. Furthermore, they reported several break-even points (BEPs) of the investments, at which the residential PV battery systems become economically viable. Some solutions to enhance the energy efficiency of centralized lighting systems are recently proposed in the literature [15,16]. There are two main differences between the system proposed in this work and the work of Park et al. [15] and Elejoste et al. [16]. The system proposed in this paper applies Buildings 2018, 8, 119 3 of 18 to stand-alone single light, while the others apply to centralized systems. The second difference is that they worked on the demand management system, while in this work, the concentration was on the supply system (i.e., battery). For instance, Park et al. [15] proposed smart energy management to increase the power efficiency of the microgrid in conjunction with a distributed power supply. They used a centralized ESS (energy storage system) to examine the problems related to ESS in the smart grid. They applied a dispersion ESS and intelligent LED system to street light a city, and this system has low cost and generates an easy-to-manage IoT (internet of things) environment. This system reduced the installation cost by 33%, and made IoT-based intelligent energy, power monitoring of street light, and efficient energy possible within a microgrid. On the other hand, Elejoste et al. [16] presented an intelligent streetlight management system based on LED lamps. This system aimed at minimizing the investment cost of traditional wired systems using wireless communication technologies, which needs civil engineering for burying of cables underground. The developed system helps to reduce the energy consumption. However, similar energy efficient demand resource management applied by [16] to the microgrid can be applied to the supply management system proposed by this work for the standalone system, to further enhance the energy savings. In this paper, the stand-alone LED lighting system is considered. The newly designed system is equipped with a new controller, which is designed to enhance the efficiency of the system by the efficient use of the available energy in the battery. The smartness of the new system comes from the fact that the system main controller has continuous monitoring capabilities to measure the level of energy in the battery and, based on the state of charge of the battery, the controller decides the level of illumination of the light, to maximize the time when the light is on. Thus, the proposed system uses the diming technique to increase the time when the light is “on” based on the available energy in the battery. 2. The Main Concept of the New System Conventional PV-lighting systems suffer from the sudden death of light. That is, once the level of energy in the battery reaches the minimum value of the depth of discharge (DOD) with a constant load, the light turns “off” suddenly. The newly proposed system will eliminate this problem by disconnecting the load when the level of energy in the battery reaches a certain level. The new system is composed of similar components to the conventional system, but the discharge controller is different. The main modes of operations of the new system are as follows: a. Charging Mode: During the day, the PV panels converts the solar energy into electrical energy and store it in the battery. b. Discharging Mode: During the night with no solar irradiation, the light requirements are triggered via a photosensor. The controller turns the light “on”. Energy is then withdrawn from the battery to turn the light load “on”. During this period, the controller keeps track of the voltage of the battery. If the battery voltage reduces below a certain threshold (which will be decided later) the dimmer starts to reduce the intensity of light. This will reduce the energy withdrawal from the battery. A further drop in the battery voltage requires more dimming of light, and then less withdrawal of energy from the battery and, thus, keeps the system “on”. Using the newly controller will increase the time of using the energy stored in the battery, and thus, the time of having the light “on”. System Prototype Although the proposed controller is built and tested on the PV-LED lighting system, it can be used in all standalone solar-powered systems. These systems are off-grid systems that can provide electrical power ranging from few milliwatts to kilowatts. Storage batteries are integrated with the stand-alone PV systems to supply the load with electricity at night or when the solar radiation is low Buildings 2018, 8, 119 4 of 18 (e.g., cloudy weather). Figure 1 shows a diagram of a typical stand-alone PV system for outdoor light. Buildings 2018, 8, x FOR PEER REVIEW 4 of 19 The system is composed of a PV panel, charge controller, battery, discharge controller, and a bulb. A prototype of the PV outdoor light was designed and built to carry out the experimental A prototype of the PV outdoor light was designed and built to carry out the experimental investigations on the performance of the new system, and compare it with conventional systems. Thus, Buildings 2018, 8, x FOR PEER REVIEW 4 of 19 investigations on the performance of the new system, and compare it with conventional systems. the prototype is used twice: in the first time, it is used as a conventional system when the conventional Thus, the prototype is used twice: in the first time, it is used as a conventional system when the A prototype of the PV outdoor light was designed and built to carry out the experimental controller is used, and for the second time, the system is equipped with the new controller. Figure 2 conventional controller is used, and for the second time, the system is equipped with the new investigations on the performance of the new system, and compare it with conventional systems. demonstrates the general assembly of the prototype which has been manufactured and assembled at controller. Figure 2 demonstrates the general assembly of the prototype which has been Thus, the prototype is used twice: in the first time, it is used as a conventional system when the Jordan University of Science and Technology (JUST). manufactured and assembled at Jordan University of Science and Technology (JUST). conventional controller is used, and for the second time, the system is equipped with the new controller. Figure 2 demonstrates the general assembly of the prototype which has been manufactured and assembled at Jordan University of Science and Technology (JUST). Figure 1. Typical photovoltaic (PV) outdoor light system components. Figure 1. Typical photovoltaic (PV) outdoor light system components. Figure 1. Typical photovoltaic (PV) outdoor light system components. Figure 2. The general picture of the prototype. Figure 2. The general picture of the prototype. Figure 2. The general picture of the prototype. Buildings 2018, 8, 119 5 of 18 Though this system will be used for experimentation purposes, it was designed and sized using the typical procedure of sizing real PV-LED lighting systems. Table 1 lists the general specifications of the prototype. Table 1. Sizing summary of prototype system components. Application Stand-Alone Outdoor Lighting System Location JUST Latitude 32.5 N Longitude 35.7 W Loads A1 Battery Voltage 12 volts A2 Rated Wattage (LED Fixture) 30 W A3 Hours Per Day Used 10 h A4 Energy Per Day (A2 A3) 300 Wh A5 Total energy demand per day (A4) 300 Wh A6 Total amp-hour demand per day (A5/A1) 25 Ah A7 Peak dc power requirement (A2) 30 W Battery sizing B1 Days of storage required (autonomy) 3 days B2 Allowable depth-of-discharge limit 0.75 B3 Required battery capacity (A6 B1/B2) 100 Ah add 20% losses = 120 Ah B4 Amp-hour selected battery (Philadelphia solar company) 100 Ah B5 Number of batteries in parallel (B3/B4) 1 battery B6 Number of batteries in series (A1/battery voltage) 1 battery B7 Total number of batteries (B5 B6) 1 battery B8 Total battery amp-hour capacity (B5 B4) 100 Ah B9 Total battery kilowatt-hour capacity (B8 A1/1000) 1.200 kWh PV array sizing C1 Total energy demand per day (A4) 300 Wh C2 Battery round trip efficiency (0.70–0.85) 0.8 C3 Required array output per day (C1/C2) 375 Wh C4 Selected PV module max power voltage at STC (x.85) 15.1 V C5 Selected PV module guaranteed power output at STC 90 W C6 Peek sum hours at design tilt for design month 5 h C7 Energy output per module per day (C5 C6) 450 Wh Module energy output at operating temperature (DF C7) C8 DF = 0.80 for hot climates and critical applications. 405 Wh DF = 0.90 for moderate climates and non-critical applications Number of modules required to meet energy requirements C9 1 module (C3/C8) Number of modules required per string (A1/C4) rounded to the C10 1 module next higher integer Number of strings in parallel (C9/C10) rounded to the next C11 1 string higher integer C12 Number of modules to be purchased (C10 C11) 1 module C13 Nominal rated PV module output 90 W C14 Nominal rated array output (C13 C12) 90 W 3. New Smart Battery Discharge Controller Design The specific objective of this controller is to control the DC current supplied to the load (LED light) to maximize the time of using the available energy in the battery, and therefore, increase the system operating hours with no sun. This controller brings other benefits to the system, such as protecting the battery from being overdischarged, by turning the LED light off when the DOD of the battery reaches a certain level. The new smart controller is composed of hardware and software to derive the controller. The controller was constructed using a low-cost programmable interface controller (PIC) microcontroller and simulated using Proteus ISIS Professional package. The next section explains both hardware and software components. Built-in ADC Buildings 2018, 8, x FOR PEER REVIEW 6 of 19 The new smart controller is composed of hardware and software to derive the controller. The controller was constructed using a low-cost programmable interface controller (PIC) microcontroller and simulated using Proteus ISIS Professional package. The next section explains both hardware Buildings 2018, 8, 119 6 of 18 and software components. 3.1. Hardware Design 3.1. Hardware Design The controller is composed of five main parts (subsystems); the regulator, scaling voltage circuit, The controller is composed of five main parts (subsystems); the regulator, scaling voltage circuit, light-dependent resistor (LDR) sensor circuitry, microcontroller unit, and LED driving circuit. The light-dependent resistor (LDR) sensor circuitry, microcontroller unit, and LED driving circuit. The analog signals received from sensors are converted into digital signals so they can be handled by the analog signals received from sensors are converted into digital signals so they can be handled by the microcontroller. The block diagram of the overall controller is shown in Figure 3, while the complete microcontroller. The block diagram of the overall controller is shown in Figure 3, while the complete schematic diagram for the complete controller is shown in Figure 4. schematic diagram for the complete controller is shown in Figure 4. Battery Voltage Scaling Voltage LED Driving Circuit LDR Sensor 5 V regulated PIC16F877A Voltage Microcontroller Figure 3. Block diagram of the proposed smart discharge control system. Figure 3. Block diagram of the proposed smart discharge control system. Buildings 2018, 8, 119 7 of 18 Buildings 2018, 8, x FOR PEER REVIEW 7 of 19 Figure 4. Complete schematic diagram of a discharge controller. Figure 4. Complete schematic diagram of a discharge controller. Buildings 2018, 8, x; doi: FOR PEER REVIEW www.mdpi.com/journal/buildings Buildings 2018, 8, 119 8 of 18 Buildings 2018, 8, x FOR PEER REVIEW 8 of 19 Buildings 2018, 8, x FOR PEER REVIEW 8 of 19 3.1.1. Power Supply Circuit 3.1.1. Power Supply Circuit 3.1.1. Power Supply Circuit A 12–15 V battery is used as a power supply/store energy for the system. A 5V-L7805 positive A 12–15 V battery is used as a power supply/store energy for the system. A 5V-L7805 positive A 12–15 V battery is used as a power supply/store energy for the system. A 5V-L7805 positive voltage regulator is used to convert the voltage from the 12 V battery to 5 V to perfectly drive the voltage regulator is used to convert the voltage from the 12 V battery to 5 V to perfectly drive the voltage regulator is used to convert the voltage from the 12 V battery to 5 V to perfectly drive the microcontroller unit (MCU) and some analog ICs and sensor circuitry. The L7805 positive voltage microcontroller unit (MCU) and some analog ICs and sensor circuitry. The L7805 positive voltage microcontroller unit (MCU) and some analog ICs and sensor circuitry. The L7805 positive voltage regulator circuit is illustrated in Figure 5. regulator circuit is illustrated in Figure 5. regulator circuit is illustrated in Figure 5. Figure 5. Schematic diagram of the 5 V regulated voltage. Figure 5. Schematic diagram of the 5 V regulated voltage. Figure 5. Schematic diagram of the 5 V regulated voltage. 3.1.2. Voltage Scaling Circuit 3.1.2. 3.1.2. Vo Voltage ltage Sc Scaling aling C Cir ircu cuit it The voltage divider circuit, shown in Figure 6, is used to scale the voltage measured from the The The voltage voltage divider divider circ circuit, uit, shown in F shown in Figur igure e 6, 6, is used to scale the voltage me is used to scale the voltage measur asured ed fr from th om the e battery to the level that can be handled by the microcontroller (from 15 V to 5 V). It is composed of battery battery to the l to the level evel tha thattcan can be ha be handled ndled by by the mi the micrcr ocontr ocont oller roller (fr(fr om om 15 15 V V t to 5oV). 5 V). It is composed of It is composed of R1 R1 = 20 kΩ and R2 = 10 kΩ. = R1 20 = 20 kW kand Ω an R2 d R =210 = 1 k0W k .Ω. Figure 6. Schematic diagram of a voltage scaling circuit. Figure 6. Schematic diagram of a voltage scaling circuit. Figure 6. Schematic diagram of a voltage scaling circuit. Buildings 2018, 8, x; doi: FOR PEER REVIEW www.mdpi.com/journal/buildings Buildings 2018, 8, x; doi: FOR PEER REVIEW www.mdpi.com/journal/buildings Buildings 2018, 8, 119 9 of 18 Buildings 2018, 8, x FOR PEER REVIEW 9 of 19 3.1.3. LDR Sensor Circuit 3.1.3. LDR Sensor Circuit LDR is a resistor in which its value changes proportionally to the change of the incident light LDR is a resistor in which its value changes proportionally to the change of the incident light intensity falling on its surface. Its primary function here is to detect sunlight to trigger the main circuit intensity falling on its surface. Its primary function here is to detect sunlight to trigger the main circuit of the system: “on” when there is no light, and “off” when sunlight is detected. LDR is made of a of the system: “on” when there is no light, and “off” when sunlight is detected. LDR is made of semiconductor material with high resistance, like cadmium sulfide (CdS) and cadmium selenide a semiconductor material with high resistance, like cadmium sulfide (CdS) and cadmium selenide (CdSe). The LDR construction of reference [17] is used because it gives a minimum area and (CdSe). The LDR construction of reference [17] is used because it gives a minimum area and maximum maximum length from CdS. It is fixed on the surface of the ceramic substrate in the form of zigzag length from CdS. It is fixed on the surface of the ceramic substrate in the form of zigzag wire. wire. The sensor is enclosed in a circular metallic or plastic case with two terminals, and covered with The sensor is enclosed in a circular metallic or plastic case with two terminals, and covered with glass to protect it from moisture and dust. It is used in many applications like fire alarms, Lux meters, glass to protect it from moisture and dust. It is used in many applications like fire alarms, Lux meters, and outdoor light controllers. The block diagram of the sensor function and the schematic diagram for and outdoor light controllers. The block diagram of the sensor function and the schematic diagram the sensor are shown in Figure 7 [18]. for the sensor are shown in Figure 7 [18]. Figure 7. Schematic diagram of the LDR sensor. Figure 7. Schematic diagram of the LDR sensor. 3.1.4. Microcontroller Unit 3.1.4. Microcontroller Unit The programmable interface controller (PIC) (Microchip Technology Inc., San Jose, CA, USA) is The programmable interface controller (PIC) (Microchip Technology Inc., San Jose, CA, USA) is a a small computer on a single integrated circuit composed of a relatively simple central processing small computer on a single integrated circuit composed of a relatively simple central processing unit unit (CPU), timers, input/output (I/O) ports, and volatile memory (RAM) and non-volatile memory, (CPU), timers, input/output (I/O) ports, and volatile memory (RAM) and non-volatile memory, ROM. ROM. Microcontrollers are, generally, designed for small and dedicated applications (not general Microcontrollers are, generally, designed for small and dedicated applications (not general purpose purpose applications), such as automobile engine control systems, implantable medical devices, and applications), such as automobile engine control systems, implantable medical devices, and remote remote controls. PIC16F877A microcontroller (Microchip Technology Inc., San Jose, CA, USA) from controls. PIC16F877A microcontroller (Microchip Technology Inc., San Jose, CA, USA) from Microchip Microchip Technology is selected in this controller because it is a very popular MCU, due to its Technology is selected in this controller because it is a very popular MCU, due to its availability, low availability, low cost, and simplicity in design. The PIC16F877A is the superset MCU in the PIC16 cost, and simplicity in design. The PIC16F877A is the superset MCU in the PIC16 family of MCUs, with family of MCUs, with most of the features, and it was the most high-end device in the PIC16 family most of the features, and it was the most high-end device in the PIC16 family until the new PIC16F887 until the new PIC16F887 was released. It is now recommended by Microchip for new designs. The was released. It is now recommended by Microchip for new designs. The differences between both the differences between both the PIC16F877A and the PIC16F887 are limited [19–21]. PIC16F877A and the PIC16F887 are limited [19–21]. Pulse width modulation (PWM) is used to generate signals of varying frequency and duty cycle. Pulse width modulation (PWM) is used to generate signals of varying frequency and duty cycle. Two modules, CCP1 and CCP2, of PIC16F877A chip are designated to generate the PWM signals, Two modules, CCP1 and CCP2, of PIC16F877A chip are designated to generate the PWM signals, which are used in this work to drive the LED. which are used in this work to drive the LED. The analog to digital converters (A/D) convert an analog input signal into a digital signal. The The analog to digital converters (A/D) convert an analog input signal into a digital signal. The PIC16F877A chip has 8 input channels and a 10-bit analog-to-digital module. In this study, two input PIC16F877A chip has 8 input channels and a 10-bit analog-to-digital module. In this study, two input channels are used to read the analog signals produced by LDR sensors and battery voltage, and channels are used to read the analog signals produced by LDR sensors and battery voltage, and convert convert them to a digital signal. The connection of the MCU is shown in Figure 8. them to a digital signal. The connection of the MCU is shown in Figure 8. Buildings 2018, 8, 119 10 of 18 Buildings 2018, 8, x FOR PEER REVIEW 10 of 19 Figure 8. Microcontroller unit circuit with input/output. Figure 8. Microcontroller unit circuit with input/output. 3.1.5. LED Driving Circuit by PWM 3.1.5. LED Driving Circuit by PWM To control the level of the light intensity of the LED, the driving circuit of LED is designed as To control the level of the light intensity of the LED, the driving circuit of LED is designed as shown in Figure 9. It receives the PWM signal from the PIC16F877A chip at a varying duty cycle, to shown in Figure 9. It receives the PWM signal from the PIC16F877A chip at a varying duty cycle, to switch the lamp on and off. The driving circuit components are as follows: switch the lamp on and off. The driving circuit components are as follows: • Optocoupler is an electronic device that transfers an electrical signal from one section of a circuit to another. It is composed of an infrared-emitting LED diode that is, optically, in line with a Optocoupler is an electronic device that transfers an electrical signal from one section of a circuit light-sensitive silicon semiconductor transistor, all enclosed in the same package [22]. It is used to another. It is composed of an infrared-emitting LED diode that is, optically, in line with a in this study to isolate the PIC16F877A chip circuit, which operates at 5 V, from the LED lamp light-sensitive silicon semiconductor transistor, all enclosed in the same package [22]. It is used driving circuit, which operates at 12 V. in this study to isolate the PIC16F877A chip circuit, which operates at 5 V, from the LED lamp • Push–pull output: It is an electronic circuit that uses a pair of active transistor Negative-Positive- driving circuit, which operates at 12 V. Negative type NPN (denoted by Q2 in Figure 9) connected to a positive voltage and a Positive- Push–pull output: It is an electronic circuit that uses a pair of active transistor Negative-Positive type PNP (Q1) connected to a negative voltage. This circuit is used to enhance Negative-Positive-Negative type NPN (denoted by Q2 in Figure 9) connected to a positive turn on–turn off for the Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) and suppress voltage and a Positive-Negative-Positive type PNP (Q1) connected to a negative voltage. This the current spikes to enhance the operating conditions for the PWM signals generated by the circuit is used to enhance turn on–turn off for the Metal-Oxide-Semiconductor Field-Effect Transistor PIC16F877A chip [23,24]. (MOSFET) and suppress the current spikes to enhance the operating conditions for the PWM • MOSFET: It is an important component in relatively high frequency, high-efficiency switching signals generated by the PIC16F877A chip [23,24]. applications in the electronic circuits. In this study, it is used to drive the LED streetlight using MOSFET: It is an important component in relatively high frequency, high-efficiency switching the PWM signals. IRLZ44N n-channel MOSFET with 49 A drains current and very low on- applications in the electronic circuits. In this study, it is used to drive the LED streetlight using the resistance of 17.5 mΩ is used in the driving circuit, provided with a heat sink to protect it from PWM signals. IRLZ44N n-channel MOSFET with 49 A drains current and very low on-resistance being overheated. The schematic diagram of the LED driving circuit is showing in Figure 9. of 17.5 mW is used in the driving circuit, provided with a heat sink to protect it from being overheated. The schematic diagram of the LED driving circuit is showing in Figure 9. Buildings 2018, 8, 119 11 of 18 Buildings 2018, 8, x FOR PEER REVIEW 11 of 19 Figure 9. Schematic diagram of LED driving circuit by PWM. Figure 9. Schematic diagram of LED driving circuit by PWM. 3.2. Controller Software 3.2. Controller Software The discharge control of the outdoor light system algorithm was constructed and implemented The discharge control of the outdoor light system algorithm was constructed and implemented based on battery load voltage. The programming language used to execute this algorithm was based on battery load voltage. The programming language used to execute this algorithm was MikroBasic pro (version 1, mikroElektronika, Belgrade, Serbia). Figure 10 shows the flowchart that MikroBasic pro (version 1, mikroElektronika, Belgrade, Serbia). Figure 10 shows the flowchart that describes the sequence of the algorithm. This algorithm was constructed according to the describes the sequence of the algorithm. This algorithm was constructed according to the characteristics characteristics of the battery given by the manufacturer. of the battery given by the manufacturer. Long debates and literature reviews have been carried out to decide the best indicator to Long debates and literature reviews have been carried out to decide the best indicator to measure measure the level of energy in a battery. In this work, it is decided to use the “load voltage” as an the level of energy in a battery. In this work, it is decided to use the “load voltage” as an indicator. This indicator. This means that to decide the level of illumination of the light, read the battery voltage means that to decide the level of illumination of the light, read the battery voltage when the light is on, when the light is on, then make the decision. Reading open voltage sometimes gives a false indication then make the decision. Reading open voltage sometimes gives a false indication because the chemical because the chemical reaction inside the battery is active. To decide the levels of stepping down light reaction inside the battery is active. To decide the levels of stepping down light levels for this system, levels for this system, the load voltage curve for the used battery (gel-acid) is experimentally the load voltage curve for the used battery (gel-acid) is experimentally measured as shown in Figure 11 measured as shown in Figure 11 using the experimental setup shown in Figure 12. The results are using the experimental setup shown in Figure 12. The results are obtained by applying a constant load obtained by applying a constant load (LED light) to the gel-acid battery, while continuously (LED light) to the gel-acid battery, while continuously measuring the battery voltage until the light measuring the battery voltage until the light turns off. Figure 11 also shows how battery discharge turns off. Figure 11 also shows how battery discharge curve is used in this work, and it is divided curve is used in this work, and it is divided into five regions. The first region (R1) when the load into five regions. The first region (R1) when the load voltage (V ) is greater than 12 V, the second voltage (VB) is greater than 12 V, the second region (R2) when VB is less than or equal 12 V and greater region (R2) when V is less than or equal 12 V and greater than 11.5 V, the third region (R3) when V is B B than 11.5 V, the third region (R3) when VB is less than or equal 11.5 V and greater than 11 V, the fourth less than or equal 11.5 V and greater than 11 V, the fourth region (R4) when V is less than or equal region (R4) when VB is less than or equal 11 V and greater than 10 V, and the fifth region (R5) when 11 V and greater than 10 V, and the fifth region (R5) when V is less than or equal 10 V, which is the VB is less than or equal 10 V, which is the cutoff region. The Proteus ISIS version 8, Labcenter cutoff region. The Proteus ISIS version 8, Labcenter Electronics Ltd., Yorkshire, England) Professional Electronics Ltd., Yorkshire, England) Professional package was used to simulate the program before package was used to simulate the program before downloading it into the PIC16F877A chip. downloading it into the PIC16F877A chip. Buildings 2018, 8, 119 12 of 18 Buildings 2018, 8, x FOR PEER REVIEW 12 of 19 Figure 10. Flowchart of the discharge controller algorithm. Figure 10. Flowchart of the discharge controller algorithm. Buildings 2018, 8, 119 13 of 18 Buildings 2018, 8, x FOR PEER REVIEW 13 of 19 Buildings 2018, 8, x FOR PEER REVIEW 13 of 19 R1 R4 R1 R2 R3 R4 R5 4 R2 R3 R5 0 100 200 300 400 500 600 700 0 100 200 300 400 500 600 700 Time (min) Time (min) Figure 11. Battery discharge curve regions. Figure 11. Battery discharge curve regions. Figure 11. Battery discharge curve regions. Figure 12. Schematic diagram of the experimental setup. Figure 12. Schematic diagram of the experimental setup. Figure 12. Schematic diagram of the experimental setup. 4. Experimental Procedure 4. Experimental Procedure 4. Experimental Procedure The fo The follow llowiin ngg are are the the steps that steps that have have b been een follow followed ed durin duringg in inquir quiring ing dat dataa from from the system the system to to The following are the steps that have been followed during inquiring data from the system to evaluate the system performance. It should be noted that this experiment has been carried out inside evaluate the system performance. It should be noted that this experiment has been carried out inside evaluate the system performance. It should be noted that this experiment has been carried out inside the l the laabora boratory to ensure compl tory to ensure compleete darkness te darkness aan nd d ensure ensure t t h hat at t t h hee o o n nly s ly s o ource urce of of light light is t is t h hee L L E ED bulb. D bulb. the laboratory to ensure complete darkness and ensure that the only source of light is the LED bulb. The measurements of light intensity were taken using the LDR sensors and at different locations on The measurements of light intensity were taken using the LDR sensors and at different locations on The measurements of light intensity were taken using the LDR sensors and at different locations on the groun the ground d. T . Th he LED e LED light light is 6 m is 6 m above above the gro the grou und. A nd. Alll measur l measured ed d daata were ta were colle colleccted an ted and d stored stored in in the ground. The LED light is 6 m above the ground. All measured data were collected and stored in the computer using data acquisition system. At the beginning of each experiment, the battery was the computer using data acquisition system. At the beginning of each experiment, the battery was the computer using data acquisition system. At the beginning of each experiment, the battery was ensured to be fully charged. During the experimentations, many physical quantities were measured: ensured to be fully charged. During the experimentations, many physical quantities were measured: ensured to be fully charged. During the experimentations, many physical quantities were measured: DC current withdrawn from the battery, battery voltage, light intensity at different locations, and DC current withdrawn from the battery, battery voltage, light intensity at different locations, and DC current withdrawn from the battery, battery voltage, light intensity at different locations, and ambient temperature. The data acquisition system gets the data from sensors with a scan rate of one ambient temperature. The data acquisition system gets the data from sensors with a scan rate of one minute. Figure 12 shows a schematic diagram of the experimental setup. minute. Figure 12 shows a schematic diagram of the experimental setup. Load voltage (V) Load voltage (V) Buildings 2018, 8, 119 14 of 18 Buildings 2018, 8, x FOR PEER REVIEW 14 of 19 ambient temperature. The data acquisition system gets the data from sensors with a scan rate of one minute. Figure 12 shows a schematic diagram of the experimental setup. Moreover, the experiment was repeated several times for two cases. In the first case, the newly Moreover, the experiment was repeated several times for two cases. In the first case, the newly designed controller is used, and in the other case, the conventional controller is used. The findings of designed controller is used, and in the other case, the conventional controller is used. The findings of each case are presented next. each case are presented next. 5. Results 5. Results 5.1. CASE 1: New Smart Controller 5.1. CASE 1: New Smart Controller In thi In this s ca case, se, ththe e babattery ttery is ful is lfully y chachar rged, ged, then th then e PV is the PV disconnected is disconnected, , and the LED and the lamp is LED lamp turned is on. During the daytime, the LED lamp is automatically turned off by the controller. Over the testing turned on. During the daytime, the LED lamp is automatically turned off by the controller. Over day thestesting , the redays, adings the of t readings he sensors of the and b sensors attery and load v battery oltage load wervolt e regist ageere wer d eus register ing a dat edausing acquis ait data ion system. acquisition system. Fig Figur ure e 13 13 sho shows ws the t the time ime v variation ariation of th of the e lo load ad vol voltage tage of the b of the battery attery duri during ng the the experi experiment. ment. T The he load voltage reaches 10 V (minimum value) after 1750 min, then the light is turned off. It can be seen load voltage reaches 10 V (minimum value) after 1750 min, then the light is turned off. It can be fseen rom the fromfithe gure tha figuret the vol that theta voltage, ge, immedi immediately ately afteafter r the li the ght light turns of turns f, jump off, jumps s toto arar ou ound nd 11 11 V V . .T The he readings taken after the light turns off represent the open voltage for the battery, which is why it readings taken after the light turns off represent the open voltage for the battery, which is why it incre increases. ases. Thi This s behav behavior ior ssupports upports our de our decision cision tto o use use lload oad volt voltage age ffor or decid deciding ing o on n energy energy leve level l in inside side the battery. Another reason for this sudden increase is partly because of the active chemical reaction the battery. Another reason for this sudden increase is partly because of the active chemical reaction inside the battery. inside the battery. Figure 14 shows the variation of the electric current with time. The electric current varies because Figure 14 shows the variation of the electric current with time. The electric current varies because the load was varying, due to the dimming process derived from the controller. Figure 15 proves that the load was varying, due to the dimming process derived from the controller. Figure 15 proves the amount of energy withdrawn from the battery changes with the load variation driven by the that the amount of energy withdrawn from the battery changes with the load variation driven by dimmer and activated by the controller in Figure 16. The total energy withdrawn from the fully the dimmer and activated by the controller in Figure 16. The total energy withdrawn from the fully charged battery is 619 Wh. charged battery is 619 Wh. 0 500 1000 1500 2000 Time of operation, min. Figure 13. Variation of battery voltage during system operation with the smart controller. Figure 13. Variation of battery voltage during system operation with the smart controller. Battery load voltage, V Buildings 2018, 8, x FOR PEER REVIEW 15 of 19 Buildings 2018, 8, x FOR PEER REVIEW 15 of 19 Buildings 2018, 8, 119 15 of 18 Buildings 2018, 8, x FOR PEER REVIEW 15 of 19 3.00 3.00 2.35A avg. at 3.00 2.35A avg. at 100%Duty cycle 2.50 2.35A avg. at 100%Duty cycle 1.96A avg. at 2.50 100%Duty cycle 1.96A avg. at 80% Duty cycle 2.50 2.00 1.96A avg. at 80% Duty cycle 2.00 80% Duty cycle1.42A avg. at 2.00 1.42A avg. at 60% Duty cycle 1.50 1.42A avg. at 60% Duty cycle 1.50 0.89A avg. at 60% Duty cycle 1.50 0.89A avg. at 40% Duty cycle 1.00 0.89A avg. at 40% Duty cycle 1.00 40% Duty cycle 1.00 0.50 0.50 0.50 0.00 0.00 0 500 1000 1500 2000 0.00 0 500 1000 1500 2000 Time, min. 0 500 1000 1500 2000 Time, min. Time, min. Figure 14. Variation of load (discharge) current during system operation with the smart controller. Figure 14. Variation of load (discharge) current during system operation with the smart controller. Figure 14. Variation of load (discharge) current during system operation with the smart controller. Figure 14. Variation of load (discharge) current during system operation with the smart controller. 28.97W avg. 22.97W avg. 28.97W avg. 22.97W avg. 28.97W avg. 22.97W avg. 16.07W avg. 16.07W avg. 16.07W avg. 9.48W avg. 15 10 9.48W avg. 9.48W avg. 0 500 1000 1500 2000 -5 0 0 500 1000 1500 2000 -5 Time, min. 0 500 1000 1500 2000 -5 Time, min. Time, min. Figure 15. Power of the load during system operation with the smart controller. Figure 15. Power of the load during system operation with the smart controller. Figure 15. Power of the load during system operation with the smart controller. Figure 15. Power of the load during system operation with the smart controller. 30.00 30.00 30.00 25.00 25.00 25.62 Lux avg. 19.26 Lux avg. 25.00 25.62 Lux avg. 20.00 19.26 Lux avg. 25.62 Lux avg. 20.00 19.26 Lux avg. 14.33 Lux avg. 20.00 15.00 14.33 Lux avg. 15.00 14.33 Lux avg. 15.00 10.00 8.27 Lux avg. 10.00 8.27 Lux avg. 10.00 5.00 8.27 Lux avg. 5.00 5.00 0.00 0.00 0 500 1000 1500 2000 0.00 0 500 1000 1500 2000 -5.00 -5.00 0 500 Time 10,00 min. 1500 2000 -5.00 Time, min. Time, min. Figure 16. Variation of light intensity at the floor directly under the LED and 6 m away with using the Figure 16. Variation of light intensity at the floor directly under the LED and 6 m away with using smart controller. Figure 16. Variation of light intensity at the floor directly under the LED and 6 m away with using the smart controller. Figure 16. Variation of light intensity at the floor directly under the LED and 6 m away with using the smart controller. the smart controller. Load current, Load current, A A Load current, A Power Power Power , W , W , W Light Intensity Light Intensity Light Intensity , Lux , Lux , Lux Buildings 2018, 8, x FOR PEER REVIEW 16 of 19 5. Buildings 2. CASE 2018 2: , 8 C , x FO onven R P tiEER onal RE CVIEW ontroll er 16 of 19 Buildings 2018, 8, 119 16 of 18 The battery is fully charged and the system operated as in the previous case, continuously, until 5.2. CASE 2: Conventional Controller the battery is fully discharged. Figures 17–20 show that the light suddenly turns off after 1250 min of 5.2. CASE 2: Conventional Controller The battery is fully charged and the system operated as in the previous case, continuously, until operation. The voltage and energy consumption decrease linearly for the first 1000 min, and then the battery is fully discharged. Figures 17–20 show that the light suddenly turns off after 1250 min of start to decrease sharply. The energy delivered by the battery to the load during this test was 618 Wh, The battery is fully charged and the system operated as in the previous case, continuously, until operation. The voltage and energy consumption decrease linearly for the first 1000 min, and then which is almost the same amount delivered during the new controller tests (619 Wh). the battery is fully discharged. Figures 17–20 show that the light suddenly turns off after 1250 min start to decrease sharply. The energy delivered by the battery to the load during this test was 618 Wh, of operation. The voltage and energy consumption decrease linearly for the first 1000 min, and then which is almost the same amount delivered during the new controller tests (619 Wh). start to decrease sharply. The energy delivered by the battery to the load during this test was 618 Wh, which is almost the same amount delivered during the new controller tests (619 Wh). 0 200 400 600 800 1000 1200 1400 1600 Time, min. 0 200 400 600 800 1000 1200 1400 1600 Time, min. Figure 17. Battery discharge voltage behavior without the smart controller. Figure 17. Battery discharge voltage behavior without the smart controller. Figure 17. Battery discharge voltage behavior without the smart controller. 2.5 2.5 1.5 1.5 0.5 0.5 0 200 400 600 800 1000 1200 1400 1600 -0.5 0 200 400 600Time 8, 0 mi 0 n.1000 1200 1400 1600 Buildings 2018, 8, x FOR PEER REVIEW 17 of 19 -0.5 Figure 18. Load current with Tout the smart controller. ime, min. Figure 18. Load current without the smart controller. Figure 18. Load current without the smart controller. 0 500 1000 1500 -5 Time, min. Figure 19. Power consumed without the smart controller. Figure 19. Power consumed without the smart controller. 0 200 400 600 800 1000 1200 1400 1600 -5 Time, min. Figure 20. Variation of light intensity at the floor directly under the LED and 6 m away without using the smart controller. 6. Conclusions In this work, a novel simple solar driven LED outdoor lighting system is designed, built, and tested. The lighting system is equipped with a newly designed controller. This controller aims at elongating the time of operation of the standalone lighting system by managing the withdrawal of energy from the system battery and keeping the light “on” as long as possible. The test results showed that the designed controller was operating as designed. The operation hours of the newly designed system are compared with the conventional system. Results showed that the operating hours of the system with the new controller reached 29.16 h (1750 min), while the operating hours for the conventional system were 20.86 h (1252 min). Finally, it is worth addressing the issue of the cost of the new controller. The cost of all main parts of the controller developed in this work, which include the regulator, scaling voltage circuitry, LDR sensor circuitry, a microcontroller unit, and the LED driving circuit, is about $60. Moreover, it is believed that the cost of manufacturing the new controller will not be much higher than the conventional one. The additional cost of the new controller over the lifetime of such systems can be Light Intensity, Lux Power, W Lasd current, A Lasd current, A Battery load voltage, V Battery load voltage, V Buildings 2018, 8, x FOR PEER REVIEW 17 of 19 0 500 1000 1500 -5 Time, min. Buildings 2018, 8, 119 17 of 18 Figure 19. Power consumed without the smart controller. 0 200 400 600 800 1000 1200 1400 1600 -5 Time, min. Figure 20. Variation of light intensity at the floor directly under the LED and 6 m away without using Figure 20. Variation of light intensity at the floor directly under the LED and 6 m away without using the smart controller. the smart controller. 6. Conclusions 6. Conclusions In this work, a novel simple solar driven LED outdoor lighting system is designed, built, and In this work, a novel simple solar driven LED outdoor lighting system is designed, built, and tested. The lighting system is equipped with a newly designed controller. This controller aims at tested. The lighting system is equipped with a newly designed controller. This controller aims at elongating the time of operation of the standalone lighting system by managing the withdrawal of elongating the time of operation of the standalone lighting system by managing the withdrawal of energy from the system battery and keeping the light “on” as long as possible. The test results showed energy from the system battery and keeping the light “on” as long as possible. The test results showed that the designed controller was operating as designed. The operation hours of the newly designed that the designed controller was operating as designed. The operation hours of the newly designed system are compared with the conventional system. Results showed that the operating hours of system are compared with the conventional system. Results showed that the operating hours of the the system with the new controller reached 29.16 h (1750 min), while the operating hours for the system with the new controller reached 29.16 h (1750 min), while the operating hours for the conventional system were 20.86 h (1252 min). conventional system were 20.86 h (1252 min). Finally, it is worth addressing the issue of the cost of the new controller. The cost of all main Finally, it is worth addressing the issue of the cost of the new controller. The cost of all main parts of the controller developed in this work, which include the regulator, scaling voltage circuitry, parts of the controller developed in this work, which include the regulator, scaling voltage circuitry, LDR sensor circuitry, a microcontroller unit, and the LED driving circuit, is about $60. Moreover, LDR sensor circuitry, a microcontroller unit, and the LED driving circuit, is about $60. Moreover, it it is believed that the cost of manufacturing the new controller will not be much higher than the is believed that the cost of manufacturing the new controller will not be much higher than the conventional one. The additional cost of the new controller over the lifetime of such systems can be conventional one. The additional cost of the new controller over the lifetime of such systems can be easily justified, especially when the security and the lifetime improvements of the battery achieved, by avoiding the overdischarge in conventional systems, are considered. Author Contributions: All the authors collaborated in the study and the paper elaboration. In particular, S.K. designed the study, established the parameters to be assessed and followed-up the data analysis and finalized the paper writing. He is also the corresponding author. A.A.M. is a master student who carried out the literature review, prepared the experimental setup and carried out the experimentations. Furthermore, A.A.M. analyzed the data and drafted the paper. A.A.-G. followed the building and testing of the controller. Acknowledgments: The authors would like to express their gratitude to the Deanship of Research—Jordan University of Science and Technology—for funding this research under grant no. 144 in 2012. Conflicts of Interest: The authors declare no conflicts of interest. The sponsor had no role in the design of the study; in the collection, analyses, or interpretation of data and the writing of the manuscript. References 1. Foster, R.; Ghassemi, M.; Cota, A. 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Journal
Buildings – Multidisciplinary Digital Publishing Institute
Published: Aug 31, 2018