Tran 1 Solar Energy EssayAbout 47 percent of the energy that the sun releases to the earth actually reachesthe ground. About a third is reflected directly back into space by the atmosphere. Thetime in which solar energy is available, is also the time we least need it least – daytime.
Because the sun’s energy cannot be stored for use another time, we need to convert thesuns energy into an energy that can be stored. One possible method of storing solar energy is by heating water that can beinsulated. The water is heated by passing it through hollow panels. Black-coated stealplates are used because dark colors absorb heat more efficiently. However, this method only supplies enough energy for activities such as washingand bathing.Order now
The solar panels generate low grade heat, that is, they generate lowtemperatures for the amount of heat needed in a day. In order to generate high gradeheat, intense enough to convert water into high-pressure steam which can then be used toturn electric generators there must be another method. The concentrated beams of sunlight are collected in a device called a solar furnace,which acts on the same principles as a large magnifying glass. The solar furnace takes thesunlight from a large area and by the use of lenses and mirrors can focus the light into avery small area. Very elaborate solar furnaces have machines that angle the mirrors andlenses to the sun all day. This system can provide sizable amounts of electricity and createextremely high temperatures of over 6000 degrees Fahrenheit.
Solar energy generators are very clean, little waste is emitted from the generatorsinto the environment. The use of coal, oil and gasoline is a constant drain, economicallyand environmentally. Will solar energy be the wave of the future? Could the worlds Tran 2requirement of energy be fulfilled by the powerhouse of our galaxy – the sun? Automobiles in the future will probably run on solar energy, and houses will have solarheaters. Solar cells today are mostly made of silicon, one of the most common elements onEarth. The crystalline silicon solar cell was one of the first types to be developed and it isstill the most common type in use today. They do not pollute the atmosphere and theyleave behind no harmful waste products.
Photovoltaic cells work effectively even in cloudy weather and unlike solar heaters,are more efficient at low temperatures. They do their job silently and there are no movingparts to wear out. It is no wonder that one marvels on how such a device would function. To understand how a solar cell works, it is necessary to go back to some basicatomic concepts. In the simplest model of the atom, electrons orbit a central nucleus,composed of protons and neutrons. Each electron carries one negative charge and eachproton one positive charge.
Neutrons carry no charge. Every atom has the same numberof electrons as there are protons, so, on the whole, it is electrically neutral. The electrons have discrete kinetic energy levels, which increase with the orbitalradius. When atoms bond together to form a solid, the electron energy levels merge intobands. In electrical conductors, these bands are continuous but in insulators andsemiconductors there is an energy gap, in which no electron orbits can exist, betweenthe inner valence band and outer conduction band Book 1.
Valence electrons help to bind together the atoms in a solid by orbiting 2 adjacentnuclei, while conduction electrons, being less closely bound to the nuclei, are free to movein response to an applied voltage or electric field. The fewer conduction electrons thereare, the higher the electrical resistively of the material. Tran 3In semiconductors, the materials from which solar sells are made, the energy gapE. g. is fairly small. Because of this, electrons in the valence band can easily be made tojump to the conduction band by the injection of energy, either in the form of heat or lightBook 4.
This explains why the high resistively of semiconductors decreases as thetemperature is raised or the material illuminated. The excitation of valence electrons to the conduction band is best accomplishedwhen the semiconductor is in the crystalline state, i. e. when the atoms are arranged in aprecise geometrical formation or lattice.
At room temperature and low illumination,pure or so-called intrinsic semiconductors have a high resistively. But the .