Light is everywhere. Light is the force that enables you to see. Light is in action as you read this text. Technically put, light (or visible light) is a form of electromagnetic radiation that can be seen by the human eyes. This radiation is precisely what enables the human eyes to see things. These electromagnetic radiations fall in the wavelength range between 380nm and 740nm. The corresponding frequency range is 405 THz to 790 THz. Over the past several decades, the study of light has erupted into a specialized branch of science called optics. The studies conducted in the past have led to the establishment of several properties of light. The properties of prime importance are those related to intensity of light, the direction of its propagation, the frequency and wavelength spectrum study, polarization direction, speed of travel in vacuum, etc. Light energy is produced from its sources and incident upon the collectors in the form of tiny collection or packets. These packets are known as photons. An amazing research outcome related to light has been the fact that photons of light exhibit properties of both waves and particles. This is called the property of duality of light’s nature.
Sources of Light Energy
A thorough understanding of any form of energy necessitates an introduction to the sources of that energy. When broadly classified, the sources of light energy end up in two categories based upon the origin of these sources. The categories are that of natural and artificial sources.
Natural Sources of Light Energy
Very obviously, sun is the primary source of light energy. Apart from sun, there are quite a few stars that contribute to the amount of light energy incident on the Earth. Light is by itself a product of some intense chemical reactions taking place inside the sun. Hydrogen atoms fuse together to produce helium atoms, and this is a very violent reaction. Light is one of the resultants of this reaction. Light forms a considerable part of the total energy released because of the fusion reactions taking place inside the Sun. The light related phenomenon of Aurora Borealis and Aurora Australis can be traced to times when the electrically charged particles that escape the sun charge the gases present in the upper reaches of atmosphere. These phenomena are also referred to as the northern and southern lights.
Meteors continue to travel across the atmosphere. In the process, they face resistance to free motion. This friction has a heating effect on the meteors and also leads to the production of light from their surface. Light produced as a result of heating is also known as incandescent light. In this way, meteors are sources of incandescent light. There are some sources of light energy that emit light when they are stuck by light (which might not necessarily be visible light, but also includes ultraviolet rays and many other forms of radiation), and these are said to be exhibiting fluorescence. If an object continues to give off light even after the radiation instigating the emission initially is turned off, or becomes ineffective, is known as a phosphorescent object. Light energy is also derived from some living organisms, most noticeably fireflies, and this phenomenon is called bioluminescence.
Artificial Sources of Light Energy
Generally, the artificial sources of light include all phenomena that produce light as a result of human manipulation. For instance, matches qualify as artificial light sources as they involve predictable and controlled chemical reactions. Incandescent electric lamps and other sources of incandescent light also make the cut as artificial sources of light because of the same reasons. Fluorescent lamps spring into action when phosphorescent substances contained in them are bombarded with ultraviolet rays. A similar bombarding mechanism is behind the lighting observed in neon lights where electrons are bombarded on gases. Electric current is also used in artificial sources of light energy, as is the case with the phosphorescent substances that give off light as a result of activation by electricity.
Properties of Light Energy
Before foraying into the technicalities of the properties of light energy, it is essential to understand as to what differentiates visible light from the other forms of waves like radio waves and X rays. The differentiating factor is the length of these waves. Light waves are just the perfect length to stimulate sensation in the optical nerves of human beings, whereas the other categories of waves are either on the shorter or the longer side.
Light is said to travel at the maximum possible speed for a material object, and the speed is approximately 299,792 kilometers per second. The speed of light is used as a fixed scientific constant and is used in several scientific equations with many practical purposes. The speed of light is the fastest in vacuum. As light moves from one medium to another, it tends to bend because of the change in speed it travels with. This is another important property of light energy which explains many routine phenomena seen around us, twinkling of the stars being one of these. Generally, not all portion of the light id refracted. Some of it is reflected back as well. Smooth and polished surfaces exhibit the reflection property of light. Two light waves can be made to reinforce each other, or even cancel out the effect of each other (depending upon whether the trough meets a trough, or a trough meets a crest respectively). This is known as the interference property of light and goes a long way in establishing the wave personality of light (light is in totality of wave as well as particle nature). Light energy waves bend as they pass obstacles and also spread as they are made to pass through openings. This is the diffraction property of light.
Uses of light energy
A strong measure of the usefulness of an unconventional form of energy is the utility it can provide. Light energy has resulted in quite a few commendable applications. The power of human beings to see is a result of the visible light. A world without light is unimaginable. Apart from lighting up the world around us, light energy has a lot more to offer to the present and future generations of the human race.
Light energy is a part of the life sustaining elements for plants. Scientifically put, plants use light energy to prepare their food through photosynthesis and thus are able to survive. During their life time, plants give off oxygen in the atmosphere and keep a tab on the amount of atmospheric carbon dioxide by absorbing it. This means that light energy has an indirect but prominent effect on the life sustenance of human beings. Since plants form a vital part of the food chain of human beings, light energy (being a basic requirement for plants) is also responsible for the physical growth of the human race.
Sunlight has a lot to contribute to the propagation of TV and radio signals. The reach of light has made it a viable medium of communication. Even otherwise, light energy has been historically used as a means of communication in the form of signals. Lighthouses have been around for centuries and served useful purposes to humans. Caution lights and emergency lights convey predefined meanings in times of emergencies.
In contemporary uses of light energy, solar cells make for the perfect example. Photovoltaic cells convert light energy into electricity which is further put to thousands of uses. A semiconductor material forms the basis for such PV (photovoltaic) cells. Solar cells collect renewable light energy from the sun in a clean manner and ensure the good health of the environment. The Sun is a source of as many as 1000 watts of free energy per second per square meter of the Earth’s surface. Solar cells are the tools which can be used to harness this energy and put it to good use. From heating water to powering the electricity of the house, these solar cells have hundreds and thousands of small and large applications. The use of such PV cells has been on the rise in the past few years. Solar cells find application in space satellites as well. Solar cells are also used with navigational vehicles. Small sized solar cells use light energy to power wrist watches and pocket size calculators. A collection of solar cells in an array is called a solar panel. Solar panels are put to use on a large scale. Even a single square meter of solar panel installed on your roof can drive enough power to illuminate a 100 W light bulb. Regions with sunny climate throughout the year have already started using solar panels for domestic lighting. A futuristic use of solar cells and panels is in light powered vehicles.
Solar furnaces are also finding some wonderful applications. A solar furnace is a planned array of mirrors which have been so arranged to concentrate a huge amount of Sun’s light energy to a small portion in order to build up a huge amount of heat quickly. The concentration of sunlight onto a small area leads to a very high temperature attained within very little time. Temperatures as high as 3000 degrees Celsius are known to have been achieved using solar furnaces! Solar furnaces are used at manufacturing plants and in heating residential set ups. Solar cookers also make for interesting applications of light energy. These small devices are used for domestic coking of food by using light energy from the sun. Not only does this prove cost effective, it also provides for a clean alternative to cooking fuels.
Advantages of Using Light Energy
Due to the fact that sun is the primary source of all light energy, all advantages associated with solar energy are inherent in the use of light energy. In fact, research in the field of better tapping and implementation of light energy is in full swing in the science quarters of the world these days.
The most obvious advantage of using light energy is the fact that it is economically appealing. Light as a fuel is free of cost, and it will continue to be so. This means that any appliance running on light energy will not require any expenses on fuel. As long as sunlight is up for use, there is no running cost (this does not include the maintenance cost) associated with light energy run equipment. Of course, there is a certain initial cost/investment associated with the implementation of a system using light energy as its fuel. However, the recovery or payback period with such investments is amazingly small which makes the investment all the more lucrative. Using light energy will be a necessity in the future when the supply of non renewable resources of energy will be limited or prohibitively expensive. This has led the world governments into doling out financial incentives to all those who opt for renewable energy resources like light energy. With light energy, you make yourself immune from the ever escalating costs of other fuels. And then, the savings begin to make themselves evident right from the initial phase of operation and accumulate quickly over time. There is also a sense of certainty about the quality of light energy, so there are no fluctuations of supply to attend to. More importantly, there are no indirect health costs to pay for clean sources of energy like light energy.
There is an environmental facet to the advantages of light energy along with the economic benefits. Light energy is clean and sustainable. This means that the environment does not have to pay any price for the use we put light energy to. There are no harmful emissions associated with the utilization of light energy, unless of course these emissions are a result of the appliance or system that light energy is being used to run. This puts a tab on the amount of undesirable and avoidable contents of greenhouse gases like carbon dioxide and nitrogen oxide which are generally associated with fossil fuels. In this way, light energy gives efficiency without global warming as a trade off. Light energy is directly used, so there are no secondary costs like transportation and distribution. This has a multiplier effect on the environmental health and economic viability of the investment in a light energy run plant or system.
Thirdly, light energy has a lot to contribute to your energy independence. This means that with a light energy powered electricity system installed at home, you become independent of the utility supplied energy. Not only does this reduce your electricity bill, it also lends you immunity against a power crisis. You are not required to plug into a power grid controlled by the state when you have a light energy based system running. Also, there are no connectivity issues, as sunlight does not recognize any geographic boundaries. Whether a person be in Atlanta or Afghanistan, the utility of light energy is the same. It is commonplace for centralized energy distribution systems to be paralyzed by natural calamities. This does not affect light energy run systems. And then, light energy implementation can bloom into a new industry in itself and provide employment and economic stability to thousands of workers and technicians.
Lastly, light energy systems are robust and do not require extensive maintenance. These systems can last for several years, and this increases their present day worth. There are no recurring costs associated with renewable and green fuels such as light energy. There is ease of scalability, as you can add on to the capacity as the need arises without incurring too hefty a cost.
Disadvantages of Using Light Energy
Whereas the advantages of light energy are pretty general, and hence worth a lot more attention than the disadvantages (which are mostly case specific), a note of some of the possible shortcomings of light energy does help proper understanding of the same.
The biggest inhibitor of the implementation of light energy based systems is the amount of initial capital and resource investment required for setting up the equipment. Although this is offset by the government powered finance schemes, there still remains a considerable degree of hesitation with the target audience. The fact that government processes are not always the smoothest of rides makes the threat of high initial expenses pretty real.
Another possible area for improvement as far as light energy based systems are concerned is their design. These systems are known to be pretty bulky and require quite an appreciable amount of space for installation. Such spaces are not always available, and this limits the implementation of the same. As research yields more results and breakthroughs, there is every possibility that this bottleneck will be removed. Till then, the constraint of proportionality between area and efficiency remains a considerable disadvantage.
The unprecedented growth seen by the real estate in the recent past has resulted in sky high towers and buildings. This means that the neighboring sites get a disrupted supply of sunlight. This in turn limits the efficiency of light energy tapping systems at such places. However, this can be overcome by the use of sunlight tapping components.
In areas that face overcast skies for a considerable part of the year, the viability of light energy as an alternative to fossil fuels will always be questioned. Similarly, night times also pose constraints on the usage of light energy. These shortcomings can be controlled and possible amended by using hybrid systems with contrition from components like batteries.