INTRODUCTION :
With the intensification of energy crisis all over the world, all the countries are looking for the way to solve this serious problem. One way is to search the new energy and take advantage of the renewable energy. Another way is to exploit the new energy-saving technologies to reduce energy consumption, and improve utilization efficiency of energy. Solar energy is the most direct, common, and clean energy on our planet we have already found until now. Total solar energy absorbed by the Earth is about 3,850,000 exajoules (EJ) in one year, which is even twice as much as all the non-renewable resources on the earth found and used by human being, including coal, oil, natural gas, and uranium etc. The solar resources can be seemed inexhaustible. LED is a solid state semiconductor device which can convert electrical energy into visible light. It is characterized with small size, low power consumption, long service life, environmental protection and durance. The spectrum of the LED is almostly concentrated in the visible light spectrum, so it has a high luminous efficiency which can be described as the great reform in the solid light source. This essay briefly describes the solar led street lighting system. It uses the solar radiation energy to charge the battery with the solar panel during day time, and offer energy to the LED light equipment at night. This system has a double advantage in both utilization of new energy and energy-savingThe solar street light does not need to set up the transmission line or route the cable, and no any special management and control are required. It can be installed in the entire public place such as the square, the parking lot, the campus, the street or the highway etc. The street lighting is closely related to people's daily life. Following quick development in process of the global urbanization, the green, efficient, and long-life LED light gradually enters into our lives.
Working principle:
The Photovoltaic (PV) cell is composed of at least two layers of the semiconductors which have been “doped” with different impurities. This makes an excess of free electrons (n-type) on one side of the junction, and a lack of free electrons (p-type) on another side. When the photovoltaic cells are irradiated with sunlight, some photons are reflected and the others are absorbed by the solar cell. When the photovoltaic cells keep enough photons, the negative electrons are released from the semiconductor material. Due to the manufacturing process of the positive layer, these free electrons naturally migrate to the positive layer which creates voltage differential. When the solar cell is connected with the external load, there will be a current circulation in the circuit. Each single solar energy cell produces only 1-2 watts. In order to increase output power, these cells (from one to several thousands) are connected in series or in parallel with others, what is called a solar array.
Using the requirements:
Solar panel
Wooden board
LDR (Light Dependent Resistor) sensors-1
4 v.lead acid battery-1
Circuit board (555 TIMER IC)
LED (Light Emitting Diode) lights-7
ON/OFF switch-1
Wires
Cool drink straws-6
Block color chart
Fevikwik+glow sticks+others
LDR Working Principle:
Working Principle of LDR. This resistor works on the principle of photo conductivity. It is nothing but, when the light falls on its surface, then the material conductivity reduces and also the electrons in the valence band of the device are excited to the conduction band.
Solar panel working principle:
They work on the principle of the photovoltaic effect. When certain materials are exposed to light, they absorb photons and release free electrons. ... Based on the principle of photovoltaic effect, solar cells or photovoltaic cells are made. They convert sunlight into direct current (DC) electricity.