The Sun Recorded Through History
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The heat energy is supplied to a fluid, which is heated until it vaporizes; the vapor is then compressed at high pressure, and released at high pressure to give motion to a gas turbine that is coupled to a generator. When the turbine is set into motion by pressurized gas or water vapor it rotates the shaft connected to the generator, which in turn rotates the shaft connected to the coil of the generator giving motion to the coil of the generator.
A generator is a machine or a device, which converts mechanical energy to electricity. The mechanical energy that is converted to electrical energy can be obtained from nuclear and chemical energy found in various types of fuel, it can also be obtained from sources such as falling water or wind. This mechanical energy can be supplied to the generator using water or wind turbines, electric motors, gas combustion turbines, internal combustion engines and steam engines.
The working principle of a generator is based on the electromagnetic induction phenomenon. The generator has a conductor that is placed between two magnets; the movement of the conductor relative to the magnetic field created by the two magnets induces a voltage in the conductor. If there is an external circuit connected to the conductor, the voltage induced in the conductor would create a current in the circuit, and the energy in this circuit can be delivered to a load. To obtain a larger current from the conductor, a large force must be applied to rotate the conductor and keep it in motion.
Most modern generators have self excited fields; this means that the current in the field coils comes from the additional exciting winding found in the armature. Before the voltage is fed in the field coils, it is rectified by passing it through a diode bridge, then passes through a regulator. A portion of current that is generated by the generator flows into the field coil generating a magnetic field. However, before the generator is started the magnetic field is generated using the residual magnetism in the cores of the magnets or a current from a battery.
Biofuels, which include ethanol or biodiesel, are known as liquid sunlight. Ethanol is produced using plants to convert solar energy into a liquid that is used as a source of energy in transportation system. Plants capture the sun’s energy through the process of photosynthesis, and then transform the energy to cellulose, sugars and starches (Nelson par 8). Ethanol is later manufactured using various industrial processes by combining water with plant material with an addition of energy; the processes produce ethanol and byproducts, which include polluted water. The resultant product, which is ethanol, is then used in transportation systems.
The current processes of producing ethanol from sunlight are regarded as involving and costly. The required raw materials is from biomass, mostly from sugarcane and corn among other energy crops, and this energy crops must be grown extensively for large-scale production; this has a huge economic implication and creates competition for land with the food crops.
Technology of converting sunlight into fuel has taken another route in order to solve the problem of competition for land with for food crops, and reduce the cost of production. The latest technology uses bacterium that is genetically modified to convert sunlight, carbon dioxide and water to fuel; this technology is expected to produce more fuel than that produced by ethanol (Nelson par16). When 1litre of ethanol is burnt, it produces 23.5 million joules.
Rivers are natural systems that provide falling water or flowing water that sets a generator into motion. The falling or flowing water is because of the water cycle caused by sunlight, when the sunlight heats the earth surface, it causes evaporation of water from the earth surface, this water in the form of vapor rises up the earth surface, and when it reaches the high regions above the earth surface, it condenses, and later falls as rain. The rain water percolates through the soil and rocks, and collects in channels forming rivers. The water in the rivers flows and if a generator is placed in its path, it gives the generator a motion, if the water in the river encounters a steep rock it creates a waterfall, and when a generator is placed below the waterfall, the falling water gives the generator a motion.
This energy from falling or flowing water gives motion to the generator, and it is considered ultimately from the sun because without the sun, the water on the earth surface would not evaporate, condense and fall as rain that later collects to form rivers that flow. The ice that forms on top of mountains also melts to form water that flows down the mountain to join the rivers that flows giving motion to the generator; without sunlight, the ice on top of mountains would not melt to water, and there could be no water flowing in rivers to give motion to the generator.
The amount of energy that reaches the top atmosphere is 1,360 watts per square meter, and the amount arriving at the earth is 340 watt per every square meter. This is only one quarter of the solar irradiance; it is also the average amount of energy that reaches an individual’s roof per square meter. However, the exact amount reaching one’s roof in a day depends on the location of the house on the earth surface, the time of the year and time of the day. When one wants to use the 340 watt energy per square meter and the daily consumption of 14,400 watts per day, then a 26 square solar panel is required, which cost almost $16,000, and since sunshine is not consistent an inverter is required, which increases the cost of installation further. Looking at the annual electricity bill, it amounts to $91, it is better to use electricity from the main than pay for all that money for installation. The payback period for such an energy system is long, and considering the low efficiency of solar power systems, it is not worthy investing in them; this is why many people shy from using these systems.
Solar cells are used in satellites, calculator and solar power production systems; they are also referred to as photovoltaic cells. Photovoltaic cells are constructed using semiconductor materials such as silicon; these cells convert sunlight straight into electricity. When the sun’s light strikes the solar cell, part of it is absorbed in the semiconductor material, and knocks the electros in the structure making them free to flow. The electric field in the semiconductor material then forces the free electrons to flow in a particular direction, and as the electrons flow they create an electric current.
Silicon, a material used to make the solar cell havespecial properties, especially when it is in crystalline form, it has 14 electrons in its three shells, the first and second shells have two and eight electrons respectively. The third hell has only four electrons, this means that this level is half full, therefore, it will always seek for how to fill the remaining space for four electrons. Silicon will be forced to share electrons with the atoms surrounding it, forming a pure crystalline structure; this structure does not readily conduct electricity because it has no free electrons (Martínez 321). Therefore, the structure is mixed with atoms with free electrons such as phosphorus to make it conduct electricity. When the sunlight strikes this structure, it forces the electrons to break free, and each electron leaves a hole behind and looks for another electron to occupy; this causes the electrons to move randomly in the crystalline lattice, and as they move, the carry current.
The performance of a PV cell depends on conditions such as the type of PV cells, solar spectral, angle of incidence, solar irradiance and the temperature. Approximately 90% of solar panels used today are made of crystalline silicon; they convert 15-20% of the sunlight to electricity (Martínez 346). There are solar cells that have a thin film of crystalline silicon, this type of solar cells converts 4-10% of sunlight reaching it.
The solar cell produces a DC current, which can be used to power DC devices, however, for systems that are designed to power AC machines or appliances, an inverter is included to change the DC current to AC.
A refrigerator is a system that transfers heat from a region of low-energy to a region of high-energy reservoir. This system consists of the following components, the cooling coil, evaporator, condenser, compressor, condenser pump, cooling tower, cooling tower fan. The refrigerant absorbs heat from the chiller or freezer chamber, then moves evaporates in the evaporator and sucked by the compressor and discharged outside the refrigerator.
The air condition uses the working principle similar to that of a refrigerator, however, the difference is that the air conditioner cools a bigger space when it is compared to the refrigerator; it can cool an entire room, while a refrigerator cools only a chiller or freezer. The air conditioner consists of a compressor, condenser and evaporator; the working fluid goes through the compressor at while it is cool and at a low pressure, it is then compressed and passed to the condenser at a high pressure, then passed to the evaporator where it changes from liquid to vapor, as it cools the room (OECD Nuclear Energy Agency 285). The vapor is then cooled in the condenser and sacked back into the compressor, and the cycle repeats itself.
The refrigerator can be used as an air conditioner if it is improvised by placing the evaporator in an open place that needs to be cooled. This is because their mode of operation is the same. The only difference is the size of the area they are cooling.
The conversion of heat energy to electricity has been tried using several physical phenomena, however, the direct conversion has not been fully achieved; this is because of the temperature levels between the processes of operation. The Carnot efficiency is an efficiency that operates within the same limits of temperature between the source and the sink. Many systems converting heat energy to electricity have tried operating within the same limit of temperature, but the result is only a small percentage of the ideal efficiency, which is the Carnot efficiency (Chen par 12). This is because of the inefficiencies of the converting system, an example of such systems is a system that converts heat energy to electricity using thermocouple; this system produces electromotive force when one of the dissimilar conductor gains heat while the other remains cold. The conductors of the thermocouple are metals that are inefficient in converting heat to electricity; the metals are good electricity conductors, and at the same time good thermal conductors, this makes the hot conductor lose the heat it has gained to the cold metal conductor, thus lowering its temperature. Such a system cannot achieve Carnot efficiency because the Carnot cycle assumes that all the heat gained from the source is converted to electricity without loses.
The Carnot cycle efficiency is computed using the formula %u1DAF = 1– T2/T1 where T2 is the temperature of the conductor and T1 is the temperature of the source of heat (Chen par 15). This is the best efficiency one can hope for when converting heat energy to electricity.
The earth is an engine that is controlled by the heat from the sun, the goes round the sun and because of its spherical shape it receives varying heat from the sun, with the tropics receiving more heat than the poles. This creates an imbalance in the available heat on the earth surface, and to balance the heat, energy is transferred from places with low latitudes to those of high latitude. The imbalance in the earth heat is also brought about by the rotation of the earth around the sun, which creates days and nights; places that experience day and night receive more heat energy from the sun at a given when compared to those experiencing night.
The imbalance of heat on the earth which caused by uneven heating of the earth by the sun determines the earth’s vegetation cover, ice, precipitation and temperature. The difference in temperatures controls the movement of air from one region to another; this movement involves cold and warm air, and depending on the kind of air present in a region, the region is referred to as either warm or cold. The difference in precipitation and vegetation cover is also caused by uneven heat of the earth by the sun, when the earth is heated the water on the earth surface rises in form of vapor and later condenses and falls in form of precipitation, and the precipitation gives vegetation enough water required for its growth. This explains why the tropics receive much rain and have more vegetation cover than the poles. The uneven heating also controls the amount ice in different regions, with regions receiving less heat from the sun having more ice than those receiving more heat. The above described aspects also affect the population of people and animals in various regions around the earth; areas with high precipitation and vegetation are mostly inhabited by people and animals, while those with less vegetation, precipitation or covered with ice are avoided by human being and most animals. All this is controlled by the heat from the sun.
Nuclear fission is a process where elements with large nucleus are split into small nuclei, nuclear power plants and industries that manufacturing nuclear weapons use this process. Elements that are used in this process include plutonium-239, Uranium-233 and Uranium-235, when these elements are struck by a neutron moving at a slow speed, they undergo fission. An example of such a reaction process is
The result of the fission process is elements of smaller nuclei and a neutron, the neutron can be used to split another Uranium-235. The process goes on and on leading to a chain of reactions, however, the reaction should be controlled, else the chain reactions would lead to an explosion. The moderated reaction can be used in a nuclear reactor as a source of fuel; it is used together with control rods to control the process by absorbing excess neutrons.
Elements are identified using the nuclei of the parent atoms, for instance, carbon is an element with 6 protons in its nucleus while Uranium is an element with 92 protons in the nucleus. Uranium is the heaviest element; heavy elements are formed from light elements through the process of fusion. The simplest reaction being hydrogen and hydrogen, and later, the fusion reactions merge to form heavier elements. During the formation of the universe, there were high temperatures and density known as big bang, and only the elements with heavy nucleus were formed, this includes, hydrogen, beryllium, helium and lithium. Heavier elements such as Uranium were created during a nuclear reaction that took place in the stars, as well as during huge stellar explosions referred to as supernovas (MacDonald 256). The sun and other stars, and planets such Earth had other elements apart from hydrogen and helium, and these elements, which included Uranium formed after the explosion of the 1st generation of enormous stars known as supernovas (OECD Nuclear Energy Agency 357). Uranium was first discovered on the planet Uranus, and at first it was named Uranus by Martin Klaproth. It is found in pitchblende ore, which is an ore of zinc and iron, however, it can also be found in coffinite, uranophane, carnotite and uraninite minerals.
Uranium is considered as a solar power, this is because its formations originated from the formation of energy emitted by the Sun. The solar power was formed from the fusion of hydrogen atoms to form helium atom, the helium atom later combined with other hydrogen atoms to form heavier atoms. The heavier atoms such as Uranium were formed through the fusion of atoms that were lighter that themselves; this shows that power that comes from Uranium is actually solar power because without the initial reaction to form solar power, then the other reactions that led to the formation of Uranium could not have happened.
Many scientists worked hard to discover the source of sunshine, and in 1904, Ernest Rutherford discovered that the sunshine was emanating from the emission of alpha particles by radioactive substances. This discovery implied that nuclear energy was the source of sunshine; however, more research proved that the sun did not have much radioactive material, and instead, the sun contained more hydrogen gas. Scientists also discovered that the amount of energy generated by a star does not vary with temperature, but it depended on the interior temperatures of the star (MacDonald 167). These discoveries helped them come closer to the answer, later Aston discovered something that rested many scientists; he discovered that hydrogen nuclei was heavier than helium nucleus, a concept that was used by Eddington to conclude that the sunshine was because of the conversion of hydrogen atoms to helium. This process was known as fusion, and the energy produced from this process depends on the mass of the atoms, this relation was derived from Einstein’s energy equation; E =mc2. The process of fusion could make the sunshine for approximately 100 billion years.
41H→ 4He + 2e+ + 2ν+ energy,
This process of energy production utilized by the earth has been a dream of mankind to solve the nagging problem of energy around the world. Scientists and researchers have been working hard to achieve this process that produces abundance of energy, they have the equation that result in the large amount of energy, which is the fusion of 4 atoms of hydrogen to form one atom of helium, two positrons, two electrons and energy. However, they realized that hydrogen atoms are positive particles; this means that they repel each other, and bringing them together is difficult. According to Bahcall, it was realized that stars that were heavier than the sun fused the hydrogen atoms using carbon as a catalyst, however, the energy produced from this reaction was relatively low.
Scientists have also thought of the stellar evolution theory, which implies that the sun is heated at very high temperatures causing the nuclear fusion of hydrogen atoms to fuse through the gravitational energy emanating from the contraction of the solar mass from its initial large gas cloud. This has given the scientist and researchers of the required conditions for the hydrogen atoms to fuse, however, there is still a struggle to find out the exact conditions for the fusion to take place, and how the conditions can be made possible for the fusion of hydrogen on earth without causing destruction.
All energy used on the earth comes from the solar energy; this can either be direct or indirect. Looking at photovoltaic and solar thermal energy used on the earth, they directly comes from the sun, but utilized in the form of electricity and thermal energy respectively. These two forms of solar energy are harnessed directly from the sun.
Another form of energy that comes from the sun but indirectly is wind. The sun heats the earth unevenly, and this causes imbalance of heat on the earth surface; the regions that experience more heat have warm air at the surface of the earth, while those that experience less heat have cool air at the surface of the earth (MacDonald 134). Following this imbalance, the warm air will tend to move from a region of high pressure to a region of low pressure, and the vice versa happens to the cool air. This continuous movement of air on the earth surface is wind, and this wind can drive a wind turbine which is used to produce electricity, run wind pumps or wind mills.
Hydropower is also derived from the sun, and in this case, the sun heats the earth surface, and the water on the earth surface vaporizes and rises above the ground. As it moves up the sky, it reaches condensation where it forms clouds that later falls as rain. The rain water percolates through the soil and rocks to form rivers, the water in rivers can be utilized to produce energy using either the flowing water or waterfalls along the river channel.
Bio-fuels also come from the sun. The sun is used in the process of photosynthesis to produce sugars that are stored in the plant in the form of starch and forms of sugars. The starch and other forms of sugars are extracted from the plant and used in the production of ethanol as a bio-fuel. Another case of bio-fuel production using sunlight uses bacteria that have been modified to utilize sunlight, carbon dioxide and water to form nuclear bio-fuel.
Nuclear energy also emanates from solar energy in the sense that, Uranium, an element that is mostly used in energy production using the process of fission, was formed from the reactions that resulted to solar energy. The fusion of hydrogen atoms to form helium atom resulted in the sunshine, and the fusion of the resultant atoms led to atoms with larger nuclei, and Uranium being the heaviest element, it resulted from the fusion of lighter atoms.
Fossil fuels are fuels extracted below the earth surface, and they were formed by the accumulation of dead animals and plants. The dead plants contained sugars that were stored after the process of photosynthesis that was initiated by the sun, and the animals ate plants which derived their food from the process of photosynthesis. Therefore, it is only sensible to say that fossil fuels and other sources of energy originated from solar power.
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