The parts of solar panel and how solar panels collect electricity
Technical description
11/1/2015
I. Introduction
Solar Panel is an engineering device which generates energy by absorbing sunlight by the phenomenon of photoelectric effect. A solar panel is collection of solar cells. This document provides information about parts of solar panel and how solar panels collect energy. After reading the document, the reader would be able to identify parts of a solar panel and how solar energy is collected and converted for residential and commercial use.
II. Components
Internal Components
A. Cover Glass - The cover glass is made of glass or other clear material such clear plastic, which seals the cell from the external environment. The cover glass protects panel from the surrounding environment.
B. Transparent Adhesive- The transparent adhesive are doped metal oxides used in optoelectronic devices which serves as a collector of electrons. A transparent adhesive holds a protective glass cover over the antireflective coating that ensures all of the light filters through to the silicon crystalline layers.
C. The Antireflective Coating (AR Coating) – The Antireflective Coating has a combination of a favorable refractive index, and thickness. This layer serves to guide light into the solar cell. Without this layer, most of the light would simply reflect off the surface.
D. N-Type Semiconductor - N-type silicon is created by doping (adding impurities) the Si with compounds that contain one more valence electrons than Si does, such as with either Phosphorus or Arsenic. Doping is the process of adding impurities to intrinsic semiconductors to change their properties. A valence electron is an electron found in the outermost electron shell. An element containing more valence electrons will try to donate valence electrons to an element containing fewer valence electrons. Since only four electrons are required to bond with the four adjacent silicon atoms, the fifth valence electron is available for conduction.
E. P-Type Semiconductor- P-type silicon is created by doping with compounds containing one less valence electrons than Si does, such as with Boron. When silicon (four valence electrons) is doped with atoms that have one less valence electrons (three valence electrons), only three electrons are available for bonding with four adjacent silicon atoms, therefore an incomplete bond (hole) exists which can attract an electron from a nearby atom. Filling one hole creates another hole in a different Si atom. This movement of holes is available for conduction.
F. Back Contact - The back contact is made out of a metal, which covers the entire back surface of the solar cell. The back contact acts as a conductor
.I. Substrate- The panel is backed by aluminum/plastic substrate that has a high strength to weight ratio and can stand up to physical abuse.
External Components
Parts of the Circuit
1. Solar Panels: The photovoltaic solar panels function through the photoelectric effect. A solar panel is a group of cells connected electrically and packaged into a module. The photovoltaic cells are made of semiconductors such as silicon.
2. Smart Inverter: A smart solar inverter is required to convert the Direct Current (DC) power of photovoltaic solar panel into Alternating current (AC) power of utility frequency for commercial and residential consumption.
3. Power control system: The solar panels are connected to a smart power control system to efficiently manage voltage and frequency using two way communication and control capabilities. The control system utilizes a combination of intelligence and central coordination to effectively manage energy, provide dynamic forecasting and maximize power backup.
4. Battery Storage: The Solar panels are connected to battery, which stores energy during periods of excess generation to minimize energy costs and backup power for emergencies and catastrophic events. The lithium ion batteries also provide electricity at times of low energy generation and higher net load.
5. Distributed energy resource- The solar panels can be configured through central control to integrate solar energy source with existing utility grid, conventional generation and other controllable loads through a microgrid to meet energy needs.
6. Gateways and Meters- The metering equipment are used to monitor local energy generation and help to monitor system performance.
III. Limitation Analysis and Consideration
The use of solar energy has been limited because of obstruction caused by cost, pollution, location and reliability. The high initial cost of purchasing and installing solar panel has hindered widespread use of solar panels. In most of the cases solar panels require batteries, inverters and a microgrid which increases investment. Although cost of solar panels is decreasing rapidly, conventional sources of energy are still cheaper and more reliable in many places. The solar energy collection also depends on location and availability of sunlight. Areas where houses are surrounded by huge buildings, trees and other obstructions cannot rely on solar energy because of low electricity generation. Clouds can diminish the power of solar panels, especially in habitually foggy or overcast regions. The unpredictability of solar panels make them an unreliable solution. As solar panels are made up of silicon, pollution in the environment can degrade the quality and efficiency of photovoltaic cells. The solar panels sometimes can gradually become damaged by ultraviolet radiation. Rain, snow, dirt, temperature fluctuations, hail and wind also pose serious hazards. Thin-film PV cells contain a number of more toxic materials than those used in traditional silicon photovoltaic cells, including gallium arsenide, copper-indium-gallium-diselenide, and cadmium-telluride. Cadmium Telluride (CdTe) is used in thin film technology, which is an optimal material for converting sunlight into electricity. The cadmium is harmless when sealed inside solar panel. But, if leaked from the panel, cadmium can inflict serious environmental damage especially to soil. The solar panels are not 100% clean as they emit harmful photoelectric energy which has potentially hazardous consequences for the environment. Workers also face risks associated with inhaling silicon dust while installing the solar panel. Moreover, most of solar panels have efficiency rate of 40% which means 60% of energy is reflected off the solar panels. The low efficiency of solar panels means large array of solar panels need to be mounted to obtain sufficient energy for apartments and commercial buildings. Thus, solar panels require relatively large areas for deployment. The solar panels require batteries to ensure constant supply of electricity. Although solar panels have long lifespan and can work for up to 30 years, batteries must be replaced periodically. The batteries contain lead and sulfuric acid, which are both highly toxic and can cause a number of impairments in exposed children, including developmental disabilities. Also, solar panels must be disassembled for roof maintenance and repairs, which requires a lot money and time. So, a lot of precautions must be taken to avoid negative effects of solar panels.
The solar energy offers one of the best ways to reduce dependency on the conventional utility grid and provides clean and reliable energy. But, there exist certain limitations and dangers attached to the usage of solar panels.
Works cited
1. Jessica Toothman; Scott Aldous: How solar cells work.
2. National Renewable Energy Laboratory (NREL). 2012: Renewable Electricity Futures Study. Hand, D. eds. 4 vols. Golden, CO: National Renewable Energy Laboratory.
3. Special Materials research and technology: How solar cells work-Solar cells overview http://specmat.com/Overview%20of%20Solar%20Cells.html
4. Solar Energy Development Programmatic EIS 2013: Solar Energy Development Environmental considerations
5. Solarcity: Gridlogic Microgrid solution
http://www.solarcity.com/commercial/sustainable-energy-solution
