Solar Cell


      Solar Cell is the creation in the electronics field aiming to convert solar energy to be electrical energy, by the electrical conduction of semiconductor such as Silicon which has the lowest cost and appears most abundantly on the world surface. They will be conducted through scientific process to be thin, pure, and flat. As soon as the light hits the Solar Cell, ray of light that has energy particle named Photon will transfer energy to Electron in the semiconductor until there is enough energy to jump out of atom gravity and Electron will mobile independently. Hence, when Electron can mobile and complete the circuit loop, the DC (Direct Current) electricity will be generated.

      The important material used to make Solar Cell is Silicon (Si) which is the same material used to make chips in computer and electronics devices. Silicon is a non-toxic material. There is the use of Si to produce Solar Cell widely due to the cheap cost, durability, and reliability. Moreover, there are still other materials able to be used to produce Solar Cell, such as, Gallium-Arsenide, CIS, and Cadmium-Telluride. However, the cost of these materials are still high, and some kind still has no proof of period of use whether they can be used in a long term.

      
          Disadvantages of the Silicon: purification and preparation of ready substance to produce the cell are still expensive and fragile in the production process

          The Operation of Solar Cell is the process to change the light energy to electricity directly. When the light, which is electromagnetic wave and has energy, hits on the semiconductor, there will the energy transfer to each other. Light energy will cause the movement of electrical current (Electron) inside semiconductor material. As a result, the electricity can be connected out to be used.

          n – type Silicon is at the front of cell, the doped semiconductor with Phosphorus,  has the property as the Electron donor when receiving energy from the sun.
          p – type Slicon is the semiconductor material doped with Boron, resulting in material structure loss of Electron (Hole). When receiving energy from the sun light, it will serve as the Electron acceptor.
          When taking 2 types of Silicon to connect together with p – n junction, the result will become “Solar Cell” in the environment that still has no sun.

          n - type silicon, which is located in front of the cell, most components are ready to donate Electrons but still has some mixing little Holes. In front of n – type side, there will be a layer of metal called Front Electrode, responsible to accept Electrons. For p – type side which is located at the back of cell, main structures are Holes, but still has some mixing little Electrons. At the back of p – type side, there will be a layer of metal called Back Electrode, responsible to gather Holes.   

 

     When there is sun light hitting, the sun light will transfer energy to Electrons and Holes, resulting in the movement. When reaching the high-level of energy state, both Electrons and Holes will run towards the conduction layers. Electrons will run to the n – type layer, and Holes will run to the p – type layer. Electrons will run together to Front Electrode layer, and Holes will run together to Back Electrode layer. When there is the circuit connection from Front Electrode and Back Electrode, completing the circuit loop, the electrical circuit will be created because both Electrons and Holes will run to each other.   

 

       The Important variables make Solar Cell has the different working performance in each location and have the importance to be determined and used in each location, along with the system calculation or the evaluation of the number of Solar Cell needed to be used in each location, are light intensity and temperature.

       Electrical current is directly proportional to the intensity of light. Meaning, when the light intensity level is high, electrical current received from Solar Cell will be high as well. Meanwhile, electrical voltage hardly varies with the light intensity. Light intensity used to measure for the standard is light intensity measured on the earth surface in the clear-weather condition, without clouds or fog, and measured at the sea level in the state that sun light is perpendicular to the earth surface. The light intensity will equal to 100 mW per square centimeter or 1,000 W per square meter, which equal to AM 1.5 (Air Mass 1.5). And if the sun light angle equals to 60 degrees with the earth surface, light intensity will have the value equal to 75 mW per square centimeter or 750 W per square meter, which equals AM2. In case of Solar Cell, AM 1.5 will be used as a standard to measuring the performance of cells.

      
       Electrical current will not vary with the temperature change, while electrical voltage will decrease when temperature increases. In average, every increase in 1 degree of temperature will cause the voltage decrease 0.5%. Furthermore, in case of standard Solar Cell used to determine the cell performance, the standard is based on the temperature level at 25 Celsius degree. For example, setting that Solar Cell that has Open Circuit Voltage (or Voc) at 21 V at 25 Celsius degree, meaning, there will be the voltage from Solar Cell when unconnected to the electrical equipments at 25 Celsius degree that equals to 21 V. If the temperature is higher than 25 Celsius degree, such as, 30 Celsius degree, the voltage from Solar Cell will drop down 2.5% (0.5% x 5 Celsius degree). As a result, the electrical voltage from Solar Cell at Voc will decrease down 0.525 V (21 V x 2.5%), remaining only 20.475 V (21 V – 0.525 V). In conclusion, when the temperature is higher, electrical voltage will decrease, resulting in the maximum electrical power of Solar Cell decreases as well.

  

                       

 

 

                                                                             

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