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SOLAR THERMAL POWER PRODUCTION USING HELIOSTATS Prithivieraaj T*, Gobinath M**

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SOLAR THERMAL POWER PRODUCTION USING HELIOSTATS Prithivieraaj T*, Gobinath M** Imperial International Journal of Eco-friendly Technologies Vol.- 1, Issue-1 (2016), pp.63-67 IIJET SOLAR THERMAL POWER PRODUCTION USING HELIOSTATS PrithivieRaaj T*, Gobinath M** *,**Department of Mechanical Engineering, Adhiyamaan College of Engineering, Tamilnadu *[email protected], **[email protected] Abstract activate turbines that produce electricity. The focusing of solar power can be achieved by parabolic dishes. Solar This paper is based on the solar technology which deals thermal power production is basically done by the following with the heating of the salt or fluids by the use of the components is explained in the schematic diagram. heliostat, receiver (solar salt tower) which includes a receiver and many no thin walled tubes. The salt can be melted and their temperature increased and then passed through a receiver by focusing a point focus method on the receiver as it collects and heat the salt to high temperature of 868K. It is further used in the steam production by the use of the turbine and heat exchanger. The salt which is used is a mixture of potassium nitrate and sodium nitrate as they can hold high temperature for more than 14 hours. We can store the heat in the salt, even we can use it in the night time also. This technology Figure 1: Solar Power Production Components 100% eco-friendly. The salt which we are using is initially A. Heliostat Mechanism melted by thermal oil it can also be heated by the solar arrays which are naturally available. The salt which we A heliostat is a mechanism that includes a dual axis sun- using can be reused for a prolonged period until the tracking mirrors mirror, usually a plane mirror which turns so power plants maintenance break. as to keep reflecting sunlight toward a defined target, compensating for the sun's apparent motions in the sky. The I. Introduction target may be a physical object, distant from the heliostat, or a direction in space. To do this, the reflective surface of the This research paper vividly explains about the solar mirror is kept perpendicular to the bisector of the angle technology by the use salt and heliostat mirrors. This energy between the directions of the sun and the target as seen from is a largely available on the earth. Renewable energy is a eco- the mirror. The target is stationary relative to the heliostat, so friendly energy when compared to energy produced by the light is reflected in a fixed direction. Nowadays, most nuclear energy, coal and other fossil fuels. Renewable energy heliostats are used for day lighting or for the production of resources exist over wide geographical area, in contrast to concentrated solar power, usually to generate electricity. other energy sources. Rapid deployment renewable energy They are also sometimes used in solar cooking. A few are and energy efficiency is resulting in significant energy used experimentally, or to reflect motionless beams of security, climatic change, mitigation and economic benefits. sunlight into solar telescopes. Before the availability of lasers Solar thermal energy is arising as a leading power production and other electric lights, heliostats were widely used to technology using renewable resources. This technology produce intense, stationary beams of light for scientific and which produce electricity by concentrating solar energy in other purposes. Most modern heliostats are controlled by single focal point this concentrated energy is then used to computers. The computer is given the latitude and longitude develop heat on salt and use it to produce the steam and of the heliostat's position on the earth and the time and date. 63 Imperial International Journal of Eco-friendly Technologies Vol.- 1, Issue-1 (2016), pp.63-67 IIJET From these, using astronomical theory, it calculates the Heliostat costs represent 30-50% of the initial capital direction of the sun as seen from the mirror, e.g. its compass investment for solar power tower power plants depending on bearing and angle of elevation. Then, given the direction of the energy policy and economic framework in the location the target, the computer calculates the direction of the country. It is of interest to design less expensive heliostats for required angle-bisector, and sends control signals to motors, large scale manufacturing, so that solar power tower power often stepper motors, so they turn the mirror to the correct plants may produce electricity at costs more competitive to alignment. This sequence of operations is repeated frequently conventional coal or nuclear power plants costs. Besides cost, to keep the mirror properly oriented. percent solar reflectivity and environmental durability are factors that should be considered when comparing heliostat B. Mirror designs. Most are countries are attempting to lower the costs of heliostats is by replacing the conventional heliostat design These are parabolic mirrors shaped like half pipe.The sun with one that uses fewer, lighter materials. A conventional shines onto the panels made up of glass which is 94% design for the heliostat's reflective components utilizes a reflective where as ordinary mirrors are only 70% reflective. second surface mirror. The sandwich-like mirror structure It is automatically tract the sun throughout day. The source of generally consists of a steel structural support, an adhesive mirror breakage is wind. We can protect it from those layer, a protective copper layer, a layer of reflective silver, breakages by turning it during intense wind storms which and a top protective layer of thick glass. This conventional often occurs in deserts. Another factor which reduce its heliostat is often referred to as a glass/metal heliostat. efficiency is deposition of sand on the mirror it can be Alternative designs incorporate recent adhesive, composite, rectified by automated washing mechanism at regular and thin film research to bring about materials costs and interval. A curved mirror 2m*3m which is about a thickness weight reduction. Some examples of alternative reflector of 3mm is more effective. There are two types of focusing designs are silvered polymer reflectors, glass fiber reinforced mirrors, they are line focus, point focus mirror. Line focus is polyester sandwiches (GFRPS), and aluminized reflectors. less expensive, technically less difficult, but not as efficient Problems with these more recent designs include as point focus. The basis for this technology is a parabola- delaminating of the protective coatings, reduction in percent shaped mirror, which rotates on a single axis throughout the solar reflectivity over long periods of sun exposure, and high day tracking the sun. The point of focus in a line focus mirror manufacturing costs. array can only reach temperatures around 300°C. Point focus, though initially costlier and technically more nuanced. The II. Solar salt tower point focus technique requires a series of mirrors surrounding a central tower, also known as a power tower. The mirrors The solar power tower, also known as 'central tower' power focus the sun's rays onto a point on the tower, which then plants or 'heliostat' power plants, is a type of solar furnace transfers the heat into more usable energy. We can obtain using a tower to receive the focused sunlight. It uses an array more energy in point focus mirror. In the northern of flat, movable mirrors (heliostats) to focus the sun's rays hemisphere, evacuated tube collectors should be installed upon a collector tower. Concentrated solar thermal is seen as pointing towards true south. This is, however, not the same as one viable solution for renewable, pollution-free energy. magnetic south or the south that your compass shows us. This Early designs used these focused rays to heat water, and used difference between magnetic south and true south is called the resulting steam to power a turbine. Newer designs using the azimuth. Depending on the longitude of your location liquid sodium have been demonstrated, and systems using (direction East and West) determines your azimuth. Azimuth molten salts (40% potassium nitrate, 60% sodium nitrate) as is different from location to location, and we should align our the working fluids are now in operation. These working solar collector on the azimuth for optimum performance. In fluids have high heat capacity, which can be used to store the addition, solar collectors must be installed at the right angle energy before using it to boil water to drive turbines. These in order to ensure that they perform with the highest possible designs also allow power to be generated when the sun is not efficiency and deliver the highest returns on investment and shining. the shortest payback period possible. The optimum installation angle for solar collectors is your latitude plus 15 A. Design degrees. For instance, we live at 30 degrees North Latitude; It is a tower which is about a height of 640 feet and hold a our solar collectors should be installed at 45 degrees – 30 solar energy receiver at the upper part. It appears like circular degrees plus 15 degrees. but actually consist of 14 panels, each made of 66 thin walled C. Design straight tubes. Some Concentrating Solar Power Towers are 64 Imperial International Journal of Eco-friendly Technologies Vol.- 1, Issue-1 (2016), pp.63-67 IIJET air-cooled instead of water-cooled, to avoid using limited Molten salt has already proved itself as a storage medium. desert water.Flat glass is used instead of the more expensive The use of similar salt as a heat transfer medium not only curved glass. Thermal storage to store the heat in molten salt leads to considerable storage in power plant technology but containers to continue producing electricity while the sun is also allows the operating temperature to be increased relative not shining. Steam is heated to 500 °C to drive turbines that to the thermal oil.
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