Essay on Building a Solar Light System

Everyone needs light to lead an everyday life, including animals, insects, and plants; even the latest technology needs a source of light for its efficient operation (Garg & Prakash, 2000). According to (Perlin, 2002), even a human eye needs light for its proper function. The natural form of light is sunlight, and this sunlight can be utilized as a source of power by converting sunlight to electric energy. Solar energy can be converted directly into electricity by using photovoltaics (PV) or indirectly using concentrating solar power (CHP). Solar energy applications have been improving for decades; however, utilization of the same is increased recently due to the scarcity of conventional energy sources. Many solar energy applications exist; however, the solar light system is a typical application of the energy-efficient system (Oke, Adigun & Fenwa, 2013).

The solar light system can be utilized in many ways, such as street lights and household lights. The benefits of a solar light system are that it is almost maintenance-free, the use of sensors eliminates manual interventions to switch ON and OFF, eliminates overhead wirings. The solar light system is powered by photovoltaics (PV) that convert solar energy directly into electricity (Callister, 2018); this generated electricity is stored in the battery. The charge controller is used in between to avoid overcharging as well as discharging of the battery. Relay and sensors in the system decide when to switch ON the system based on the availability of the ambient sunlight. The system is switched ON when it gets darker and switches OFF when sunlight or another form of light. The sensor called LDR (Light-dependent resistor) is used to accomplish this; the operation of LDR resembles a human eye (Oke, Adigun & Fenwa, 2013).

This report illustrates the function of each element used in the solar light system, along with the connections between these elements. The report also shows quick electricity calculations required by the battery and electricity generated by the solar panel.

Elements in the solar light system

Solar panel

The assembly of photovoltaic cells is called solar panels. Solar panels are used in solar applications to convert solar energy into electricity. Photovoltaic cells in solar panels are made of semiconductors. The silicon crystals are laminated into n and p-type and stacked on each other. Electricity is generated due to the photovoltaic effect when the sun rays strike the crystals (Kyocera, n.d.). The produced electricity is referred to as direct current and can be utilized instantly or stored in the batteries to be used later. Most solar plants and applications use multiple panels due to limited power generation by a single solar panel. A typical solar system has an array of solar panels, the inverter, solar tracker in some cases, and the necessary wiring for the connections system (Oke, Adigun & Fenwa, 2013).

Charge controller

The charge controller is used to control the charging process of the battery. Many new technologies are available in the market; the one with MPPT- Maximum Power Point Tracking can provide efficiency up to 98%. The charge controller is usually located in between the solar panel and the battery. The charge controller prevents the battery from overcharging; it also prevents it from over-discharge. The charge controller consists of an electronic circuit with an operational amplifier, an electronic switch, a transistor, and a relay on electromechanical principles. The circuit within the charge controller switched ON and OFF by the transistor, which is operated based on a signal received from LDR (Oke, Adigun & Fenwa, 2013).

Battery

The electrical device that converts the chemical energy into electricity is known as a battery. The battery has a minimum of two or more cells connected in parallel or series. Every cell within a battery consists of a positive and negative electrode along with liquid or solid electrolyte. One of the electrodes forms electrons due to the electrolyte, which has an ionic conductor, whereas another electrode accepts these electrons. An electric current flows when these electrodes are connected to the load or a device to be powered (Oke, Adigun & Fenwa, 2013).

Stepdown transformer

The function of the step-down transformer is to transform the electric power from one circuit to another while reducing the voltage and current while keeping the frequency constant. For example, the step-down transformer used in the solar light system reduces the voltage of the external power supply to the system voltage (Raviteja, 2017).

Microcontroller

A microcontroller is a control device usually located in the charge controller; however, the microcontroller is being used as a core element for this system. The detailed functional diagram is shown in figure 1. The microcontroller consists of an integrated circuit design that governs Switching ON and switching OFF the system based on the signals received from the LDR sensors. The input signal from the LDR is processed in the microcontroller and provided to the relay as a form of output. A typical microcontroller consists of memory, input and output connections, and a processor (Rouse, 2012).

Sensors and relays

The sensors detect the intensity of the light, whereas the relays are electromechanical devices operating according to the signals received from sensors. The light-dependent resistor is used in this system which is light sensitive and responds to the intensity of the light; the system switched ON to start the flow of electricity when the intensity of the light is low, for example, during heavy overcast, dusk. On the other hand, when these sensors detect excessive light, the circuit is switched OFF to disconnect the flow of electricity (Oke, Adigun & Fenwa, 2013).

LED lights

LED- Light Emitting Diodes are made up of semiconductors. Multiple LEDs are combined to produce LED lights or lamps. Each diode uses a negligible amount of power; therefore, these combined LED lights are cost-effective compared to compact fluorescent and incandescent lamps. Furthermore, these LED lights have high efficiency and long life. However, the cost is comparatively higher. In addition, the LED produces strong colored lights due to a tiny band of wavelength (Oke, Adigun & Fenwa, 2013).

Element connections

Figure 1: A functional block diagram of a solar light system (Sharmitha & Maithili, 2017)

Figure 1 shows the connection between all the elements in the solar light system in the form of functional blocks. This system is arranged considering the final output to reduce manual intervention to switch it ON and OFF. The microcontroller is used as a core element to achieve the automated operation of the system. The solar panel is connected with the battery through a charge controller. The relays are located on the output ports of the microcontroller to perform the function of switching ON and OFF, whereas LDR is located on the input ports of the microcontroller. The step-down transformer reduces the voltage from the external supply to the system, whereas the rectifier converts AC to DC supply since LED lights work on the DC supply. Voltage regulators ensure regulated DC output to the system.

Calculation

Light output, battery voltage, and current

The required light output depends upon the application of the solar light system, where it will be used, and the area it covers. Therefore, according to the CIE publication, class M (Lightening classes for Motorized traffic) will be considered (CIE, 1977).

2 LED lights of 30 Watts are being used in this system with one 12 Volts battery (Lithium); please note the standard voltage of battery available in the market is 12 V.

Battery Capacity

I am assuming a total lightning time of 9 hours starting from 20:00 to 5:00 in the morning, working on a full 100% load.

Several days the system is working, seven days.

To avoid over-discharge of the battery, assuming 80% of the discharge plus wastage of power during different loads, therefore,

Power and number of solar panel

Assuming average sunlight hours in the United States= 4 hours

Standard voltage and power of solar panel= 12 volts, 110 Wp

Therefore, it needs to configure more than 20% for the power of the panel

The Wp= 162W is just a theoretical value, as there is a need for power for the charge controller, rectifier, microcontroller. Therefore, it is necessary to add up to 25%, the actual power of the solar panel required is,

Solar charge controller sizing

Standard voltage and power of solar panel= 12 volts, 110 Wp

Conclusion

The solar light system has been designed considering its use as a street light. The calculations are completed based on the assumption made for the LED lights. A battery of 12 volts is used, whereas two solar panels of 110 Wp and 12 volts are connected in parallel to keep the voltage constant. The charge controller of 22 Amps is used between the panels and the battery. The assembly of microcontrollers, sensors, and relays is used for the automated operation of the solar light system. The external supply and the step-down transformer that acts as a backup inverter system could be eliminated to keep the light system solely working on the solar energy.

Work cited

Callister, W. (2018). Materials Science and Engineering: An Introduction (7th ed., p. 13). New York: John Wiley & Sons, Inc.

CIE. (1977). Recommendations for the lighting of roads for motorized traffic =. Paris: Bureau Central de la CIE.

Garg, H., & Prakash, J. (2000). Solar Energy, Fundamentals and Applications (1st ed., p. 1). New Delhi: Tata McGraw-Hill Education.

Kyocera. The principle of Solar Cell Retrieved from https://global.kyocera.com/prdct/solar/spirit/about_solar/cell.html

Oke, A., Adigun, A., & Fenwa, O. (2013). Design and Construction of Solar Power-Based Lighting System. International journal of engineering sciences & research technology, 2(9), 2289-2292.

Perlin, J. (2002). From space to earth (1st ed.). Cambridge, Mass.: Harvard University Press.

Raviteja. (2017). Step Down Transformer: Working, Applications, and Rating. Retrieved from https://www.electronicshub.org/step-down-transformer/

Rouse, M. (2012). What is a microcontroller? – Definition from WhatIs.com. Retrieved from https://internetofthingsagenda.techtarget.com/definition/microcontroller

Sharmitha, D., & Maithili, P. (2017). Solar-powered intelligent street lighting system for highway application. International Journal of Pure and Applied Mathematics, 116(11), 151-160.