Photovoltaic Panels

• Solar Panels on a roof, courtesy www.ecobob.co
  
  Photovoltaic, or solar, panels are devices designed to harness the energy in light and change it into usable electrical current. Photovoltaic panels are mounted on roofs, the tops of cars or other areas where they receive maximum exposure to the sun. They are heralded as ecologically friendly devices since they produce no noise or pollution as a by-product and have no moving parts that need oil or replacements. Originally, photovoltaic panels were used most often in satellites and spacecraft that could draw constant power from the sun, but there are many commercial uses for solar energy today, from recharging batteries to reducing home energy bills.
  
  

Solar Energy

• At the heart of the photovoltaic panel is the photovoltaic cell, a small working device that harvests sunlight and turns it into a low electrical current, which is combined with the current of surrounding cells and sent to be stored or to power other devices. Panels usually contain around 40 solar cells, a configuration called an array. Solar plants have thousands of such arrays designed to catch the maximum amount of solar energy possible. Household solar devices usually only have one to several arrays, enough to partially power electrical appliances or power a single utility, such as the water heater.
  
  The photovoltaic cells themselves work using semi-conductive materials that have been produced to be especially light-sensitive. The most common material used is porous silicon, similar to the kind used to create computer chips, but synthetically formed to have different properties and covered with a light honing film. When most objects encounter photons, or the wave-particles that make up light, they absorb some and reflect some back, allowing our eyes to perceive color. Objects that absorb a large amount of photons quickly gain energy, as most people have experienced by wearing black clothes on a sunny day. The same heat that black objects gain as they absorb sunlight is used by solar panels to produce electricity.
  
  

Photovoltaic Cells

• As the cells gain energy from the focused photons, their atoms become energized and eventually start to give up electrons. Since the cells are carefully divided into a positive and negative side, these electrons naturally move from one side to the other. If mini-conductors are attached to the two sides, the electrons will flow through the conductors on their way, creating an electrical current. This process is affected by a myriad of different factors, including the type of cell, the films used to enhance their abilities, and what kind of protective coatings they have. Even today, the maximum efficiency of any photovoltaic cell is about 20 percent, meaning that out of all the energy the sunlight sends into the cell, only 20 percent, often less, makes it through as electricity. The rest is lost in heat and the uncertainty of the electron transference process.