Wind Power Analysis - Literature review Example

?Wind Power (A Literature Review) In the study of wind power, it is essential to that several factors affect the conversion of wind energy and the advantages of utilizing wind power out of the useful energy form generated may vary depending upon the requirements of different systems of function it is intended for. As a form of solar energy, the energy of the wind is found to comprise turbulent masses of air rushing to even out the differences in atmospheric pressure formed when the sun heats the air more in one place than in another. For centuries, wind power has been utilized extensively in pumping water, grinding grain, and producing electricity of the modern age for which energy conversion systems ought to take into account the ‘general rules of thumb’ as indicated in the formula which the German physicist Alfred Betz came up with in 1927 in which – (1) the power in the wind is proportional to the cube of the wind speed; (2) the power in the wind is proportional to the area swept by the rotor; (3) the power in the wind is proportional to the density of the air (Park, 1982). According to history, the practical use of wind power began with the Egyptians around 2800 BC when slaves were made to row overseas using sails which were further employed in lifting water and operating grain-grinding stones even to within the period when Persians built panemones or vertical-shaft windmills in 700 AD. Some other civilizations of the Middle East followed the same tradition whereas the Crusaders of the West are believed to have improved the windmill concept that led the Dutch to put up propeller-type windmills structured with horizontal shafts or axes of propulsion. Technical developments continued during the Middle Ages and comparative studies show aspects of similarity among windmills founded in British colonies, New England, and Holland which altogether bore significant impact in the construction of the widely known ‘American Farm Windmill’ which was invented by Daniel Halliday who, in the mid-19th century, thought of creating a multi-bladed (Panemone Bladed Rotor Wind Energy Harvester with 8 Airfoils) windmill. At the turn of the century, wind-produced electricity as well as wind-charger technology became popular, especially to the farmers of the Great Plains who necessitated up to 1,000 Watts of DC-power in their mechanically run farming tasks. Eventually, a number of countries in Europe were inspired to create wind generators of enormous size and both the French and the Germans attempted to conduct feasibility experimentation on 100-kW and 300-kW wind generator units in the 50s and the 60s. Through the years, the continuous process of harnessing wind power made possible not only D. Halliday’s multi-bladed craft but even the succeeding advancements in the iron water-pump industry which heightened the demand for wind-powered deep well pumps in the past. While the energy derived from the wind had been discovered with other chief potentials as in heating houses and barns, running sawmills and washing machines, several Midwest farmers who already possessed gasoline or kerosene generators to charge batteries still sought the aid of wind power in minimizing troubles with wear-and-tear generators and in reducing costs of fuels used. Such capacities, however, depend upon the quantities of wind power in acquisition. In his findings, P.C. Putnam illustrates a method to approximate the amount of power which can be extracted from the wind and the means to locate wind power with considerations to the periodic fluctuations in wind power as well as its reliability and short-term predictability. The author regards the concepts of kinetics hereafter necessarily pointing out that, like the kinetic energy of any particle, the kinetic energy of the wind may be computed via half of its mass multiplied by the square of the wind velocity and in terms of the volume V of air passing over an area A per unit time, the wind’s kinetic energy equals the product between wind density and (1/2)*AV 3. This is nevertheless modified in the theory of A. Betz presenting the maximum fraction 16/27 of the power in the wind which could be extracted by an ideal aeromotor so that the optimum power reachable is theoretically calculated with 0.593KAV 3. By showing a graph of the power output of a generator in kilowatts as a function of the wind velocity, it is figured that an almost linear relationship exists between the rate of the wind and the corresponding power output and based on this information, it becomes possible to estimate the annual output at a wind site wherein long-term velocity-frequency distribution curve can be determined by converting the velocities to outputs, then multiplying by the hourly distribution and obtaining the sum for the total output in a year, expressed in kilowatt-hours. It is observed to this extent that “a wind-turbine whose design is economical will show a maximum overall efficiency of about 35 percent, usually at some low value or wind velocity, say 18 miles an hour, and will convert to electrical energy about 6 per cent of the energy in the wind which annually passes through the disc area”. On the basis of studies carried out for the Grandpa’s Knob, Mt. Washington, and Blue Hill, the variation in computed aero-electric output reflects that wind output is most reliable in the fall, spring, and winter, and least so in mid-summer. As predicted conditions manifest that no output results from winds moving at velocities less than 17.5 miles per hour, full output may be expected from those that travel at rates equal to or greater than 34 miles per hour with the prediction of some output within these two figures. Putnam infers that the ability to predict mean wind velocities at hub height suggests aerodynamic criteria via profiles of mountains and of airfoils that would be of ample advantage in selecting a wind-power site and where trees are deformed by wind, the long-term mean annual wind velocity at specimen height can be estimated directly to account for the ecological criteria of the site selection. D. Marier documents another way of estimating the wind energy available at a site via the ‘power curve method’ whereby power curves for many of the commercially available wind systems at distinct speeds are kept by manufacturers particularly in reference to the rotor’s cut-in speed at which the generator begins charging (Marier, 1987). An equivalent endeavor in the assessment of the wind resource is demonstrated by the collaborative work of R. Hunter and G. Elliot on wind-diesel systems detailing an advice on choosing a decentralized wind energy site as well as providing guidance on wind resource evaluation considering the mean wind speed, frequency distribution of the wind speed, wind speed as a function of wind direction, and the Weibull parameters applied thereon. Different assessment techniques are inclusive of examination of published data and topographic maps, inspection of sites in order to verify and update the topographic maps and filter out sites with negligible contribution, and a variety of wind measurement programs with numerical modelling strategies. For a typical Wind Turbine Generator (WTG), Elliot and Hunter proposed steps in site selection which involve survey of available meteorological information, inspection and selection of candidate sites, simple ‘guidelines’ terrain model, more sophisticated numerical terrain models, and other techniques on assessing wind origins and dimensions. Regional wind-power survey is subjected to specification under two cases – a timbered region and a non-timbered region in which observation stations are set up to evaluate wind velocity by studying the geometry of the site and a range of mountains comprised in the area of concern (Hunter & Elliot, 1994). With their research on wind structure and statistics, U. Hassan, D.M. Sykes, and company focuses on the nature of atmospheric winds on discussing mean wind speed profiles and averaging periods, claiming that it is of huge essence to acquire some knowledge about the structure and behavior of the wind for a designer to gain better understanding and prediction of wind turbine performance. From site to site, wind profiles may vary depending on the general climate of the region, the physical geography of the locality, the surface condition of the terrain around the site, plus many other factors that present details regarding the nature of winds in the atmosphere. Hassan et al. manages to make simultaneous recordings of wind speed at three heights during strong atmospheric conditions from which the outcomes indicate that: (1) the wind speed increases with height; (2) turbulence or wind speed fluctuations exist in the monitored region; (3) the turbulence is spread over a broad range of frequencies; and that (4) the turbulence at different heights is correlated with correlation being stronger for small separations and at low frequencies (Freris, 1990). Similarly, E.W. Golding investigates on wind characteristics and distribution with respect to the nature and occurrence of wind, the relationship between power generation and wind characteristics, and world distribution of wind and its economic use. Here, wind power concerns are analyzed in association to differences in air density and variations in temperature which bring about the flow of air latitude upon latitude or from a point of higher pressure to a point of lower pressure by which the author finds that the resultant direction of the wind is influenced at an appreciable degree by the velocity of the earth’s surface which falls from about 1000 mph at the equator to zero at the poles. Demonstrating the link of wind characteristics to power production, Golding addresses how the wind is distributed over time in short and long periods alike, what yearly amounts of energy can be expected, the probable durations of very high wind speeds, and what parts of the world have adequate wind supply so that utilization of wind power would prove economically beneficial (Golding, 1976). Based on Golding’s efforts, the annual mean wind speed and the cost of power generation by alternative methods along with the annual capital charges of the power plant with optimum design for a specific climate all govern the economic use of wind power. Relative to other evidences contained in literature, it is affirmed that the annual average wind speed at any site relies upon its geographical position, its more pronounced designation in terms for instance of altitude and distance from the sea, its exposure and the nature of the surrounding ground in which the wind is exposed, and the shape of the land in the immediate vicinity. Typical good sites that satisfy requirements toward ideal wind power are found to pertain to landforms such as hills that are smooth, steep, and are lying near a sea or large body of water. Moreover, it is discovered that development of hill clusters like the ones (Wind Farm Layout and Design) present in Great Britain and Ireland consequently yields to the desired wind-power area that is said to achieve certain likeness with the strategy of a hydroelectric framework which serves the advantages of – (a) reduction of transmission costs which would improve the economic potentialities of a group of sites at some considerable distance from the supply network; (b) reduction of the cost of transporting the materials of construction: a central depot, storehouse and assembly workshop could e established; (c) reduction of maintenance costs through the possibility of a small staff being able to concentrate on attention to a close group rather than having to travel round an extensive district; and (d) clusters of hills suitable for such development are of little value for agriculture or any other purpose. Prior to its evolution to wind turbine, a windmill in its earliest form normally consists of a mill with vertical shaft at the center as it turns a number of sails radially mounted on the vertical axis about which the sails revolve via the action of wind forces or torques. The principle of rotation is very common in ancient times when people like the Persians were experiencing a great deal of help from simple rotary machines to assist them in conventional livelihood of everyday. Primitive windmills of Europe are quite distinguishable from those of the Middle East as the building of the former had arranged sails along horizontal shaft until this type was further enhanced by the Dutch in featuring a windmill with propeller which later pioneered the device used to generate electricity. English windmills, on the other hand, exhibit progress in design according to the two principal types – ‘the post mill’ and the ‘tower mill’ whereby a post mill is made of a weather-boarded wooden body housing the machinery and carrying the sails on an inclined wind-shaft which projects through the top of one side while the tower mill has a fixed supporting brick-built tower with a cap that carries the rotatable sails. Nowadays, wind turbines as major replacements to windmills perform the course of wind power upon conversion of the wind’s kinetic energy to mechanical energy which sustains small to large farms and villages with clean and renewable loads of electricity. Modern technological advancements in the fields of engineering and science have revolutionized the old design in windmills with a flexible range of horizontal and vertical axes installed for efficient mode of energy capture. Unlike the old-fashioned energy conversion systems, the schematic complexity of wind turbines allow the force of lift to work with the force of drag in causing the rotor to spin, enabling the shaft to turn the generator in the making of electricity every time a pocket of low-pressure air collects on the downwind side of the blade (3). Besides their stand-alone applicability, other special purposes may be fulfilled by wind turbines if farmers, ranchers, and homeowners in general would prefer to attach the turbine device to a grid system of power utility or have it configured with photovoltaic panels in meeting the aim to produce a cheaper electrical power source. Unlike the previous state of wind industry, wind turbines of the current age are capable of energy output ranging from less than 1 kW up to capacity exceeding 3 MW and manufacturers are looking to extend wind turbine operations offshore. Grounds for turbine selection based upon the aforementioned wind velocity profiles, other relevant wind characteristics, and the geography of meteorological sites are acknowledged by gauging important factors namely – the size, wind resource and climate, availability for purchase, reliability, warranty, proximity of operation and maintenance teams, service contracts, and availability of spare parts (4). Hackleman discusses in the light of selecting a wind spinner that in getting more (power) for less (cost), increasing the efficiency of the part implies increasing the efficiency of the whole yet the efficiency of the whole cannot exceed the efficiency of the part known to be least efficient. He adds “if any part of the system is no more efficient than 10%, the whole system cannot be more efficient than 10%.” Equivalently, the usable wind energy may be augmented if there is a chance to – (i) increase either the efficiency of the aero-turbine or the entire wind system; (ii) adjust the size of the aero-turbine; or (iii) make increments to the wind velocity (Hackleman, 1977). B. Alboyaci, in line with the innovations perceived for the wind turbines, conveys in paper how the wind turbine generating systems (WTGS) represent wind turbine technology through fixed speed and variable speed designs. These categories signify the use of Squirrel Cage Induction Generator (SCIG) with fixed speed in the consumption of reactive power without contributing to voltage control and WTGS with variable speed that can opt to synthesize or consume reactive power, bearing the ability to regulate the power factor, respectively. Furthermore, since Alboyaci aims for the composition to review the connection requirements of wind farms to the grid and determine the manner by which grid codes must be adapted for the integration of wind power capacity to be attained in full measure as electrical stability remains unaffected within the quality wind turbine system. It is tackled in the formal report that if wind farms were to satisfy grid connection requirements under the single objective of maximizing power output, installations would have to be confined in establishing favorable settings with power control and frequency range, power factor and voltage control, and transient fault behavior / voltage operating range (5). References Jack Park, 1982. Wind Power Book. Edition. Cheshire Books. Donald Marier, 1987. Wind Power for the Homeowner: A Guide to Selecting, Siting, and Installing an Electricity-Generating Wind Power System. Edition. Horizon Book Promotions. Palmer Cosslett Putnam, 1974. Power from the Wind. New impression Edition. Van Nostrand Reinhold Inc.,U.S.. R. Hunter & G. Elliot, 1994. Wind-Diesel Systems: A Guide to the Technology and its Implementation. Edition. Cambridge University Press. Freris, L.L., 1990. Wind Energy Conversion Systems. Edition. Prentice Hall. E. W. Golding, 1976. The generation of electricity by wind power. Second Edition. A Halsted Press Book. Michael A. Hackleman, 1977. Wind and Windspinners: A Nuts and Bolts Approach to Wind-Electric Systems. Edition. Peace Pr Pub. THE WIND POWER BOOK. 2012. THE WIND POWER BOOK. [ONLINE] Available at: . [Accessed 03 July 2012]. Wind Turbines. 2012. Wind Turbines. [ONLINE] Available at: . [Accessed 03 July 2012]. Wind Power - Wind Energy - Renewable Energy World. 2012. Wind Power - Wind Energy - Renewable Energy World. [ONLINE] Available at: . [Accessed 04 July 2012]. Chapter 15: Turbine Selection and Purchase | Windustry. 2012. Chapter 15: Turbine Selection and Purchase | Windustry. [ONLINE] Available at: . [Accessed 05 July 2012]. COWI - Wind farm layout and design . 2012. COWI - Wind farm layout and design . [ONLINE] Available at: . [Accessed 05 July 2012]. scribd.com/doc/2428245/Grid-Connection-Requirements-for-Wind-Turbine-Systems-in-some-Countries-Comparison-to-Turkey Read More