The power efficiency of a wind turbine may be influenced by several parameters such as wind speed... more The power efficiency of a wind turbine may be influenced by several parameters such as wind speed and type and age of the turbine and its accessories. This study was conducted at Ashogoda village to compare the theoretically predicted power from the wind speed of Ashogoda area with electrical power generated from the wind turbines. Daily data of 10-minute intervals of six months were obtained from the company but data of two months were excluded because they were incomplete. The data were analyzed and comparisons of different parameters were made for fifteen turbines that had full data over the four months. Both wind and turbine powers showed diurnal variability that was difficult to predict. Variability between days over the four months showed some kind of cyclic patterns with one major peak and two minor peaks every 33±4 days but consecutive peaks occurred every 3-7 days. Both turbine power output and the power coefficient were nearly 25% (250 kW output for a 1 MW rated turbine) thereby limiting the rated power to 20-30%. The efficiency of the output power decreased with increasing wind speed possibly due to high friction loss at high wind speeds. The variability among the turbines was low and none of them revealed efficiency in excess of 27%. The efficiency of the turbines claimed by the company (38%) exceeded the average actual efficiency (~25%) by about 34%.
Solar energy is the prime energy source of hydrologic parameter such as evapotranspiration and ae... more Solar energy is the prime energy source of hydrologic parameter such as evapotranspiration and aerodynamic parameter like wind. Knowledge of daily global solar radiation is important to estimate all solar energy related parameters. In this study, mean daily global solar radiation at Haramaya University (HU) and Dire Dawa (DD) meteorological stations were estimated using sunshine duration data, which were recorded using Campbell-Stock Heliograph as the input of Angstrom-Prescott model. These values were further used to calculate the half hourly power intensity of solar radiation by applying Collares-Pereira and Rabl's model. A 14 cm by 14 cm 12 V solar module was used to take indirect measurements of the solar radiation at the interval of 30 minutes from sunrise to sunset throughout the course of the study period. Readings were made in terms of voltage using a multi-meter, from which power intensities were calculated. Finally, comparisons were made between the estimated values of the half hourly power intensity of the solar radiation and the corresponding measured values to examine the degree of variability between the measured and estimated values of solar radiations using quadratic and Gaussian fits. The estimated values of the half hourly power intensity of the solar radiation agreed closely with the corresponding measured values within the error range of 15% when Gaussian fit was used but only within the error range of 10% when the quadratic fit was used. Gaussian fit reflected the actual solar radiation better than the quadratic fit despite the larger difference between the estimated and measured values. It could be concluded that satisfactory estimates of mean daily global solar radiation were obtained at both locations by using solar modules in the absence of pyranometers, and the errors could be minimized by selecting the appropriate mathematical function.
Physical exercise is important for maintaining physical fitness and contributes positively to mai... more Physical exercise is important for maintaining physical fitness and contributes positively to maintaining a healthy weight, promoting physiological well-being, and strengthening the immune system. It is a fact that many life threatening conditions can be prevented by regular exercise. This research attempted to investigate the effects of intensified physical training on physiological changes and performance efficiencies on Haramaya University first year sport science students. An informal design (i.e. before and after without control) was applied. Twenty participants were selected from first year sport science department. Ten male and ten female students participated in different physical training programs of varying intensities for 3 consecutive months, i.e. 3 days per week and 60 minutes duration per day. Pre and post training performances and laboratory tests were conducted and analyzed for performance efficiency levels and major physiological changes. Findings of this study revealed a significant effect of physical exercise on cardio vascular endurance, muscular endurance, muscular strength, flexibility and body composition as well as some physiological changes. Based on the findings, it was concluded that intensified physical training had a positive effect on performance and physiological changes of the subjects.
Drought can generally be defined as the persistence of precipitation deficit. It can range from m... more Drought can generally be defined as the persistence of precipitation deficit. It can range from mild to extreme depending on the severity of the lack of precipitation. The area around abun affected by drought and consistently demanding grain charity. This study attempts to investigate the cyclic pattern and severity of the drought and its link to the atmospheric tel stations (Mieso, Chiro and Hirna) were obtained and analyzed. Out of the three stations Chiro station data were found to be slightly similar to Mieso data. For the data analysis Mieso dat analyzed Chiro rainfall data. The analyses were made using Dekadal Dryness Indicator (DDI), Start of Season ( (SPI) and the Standard Precipitation and seasons selected for the analysis were Feb. Sept. (the main rainy season) separately and by combining the two seasons. Besides, the drought years were related to global atmo teleconnections. The averaged rainfall results reveal the first dekad of July as start of season ( respectively. The three months or less. The run theory exhibited drought intensities of mm and Based on SPI analysis severe d season had four moderate drought years. The combined six months rainy season experienced 2 severe and six moderate drought years. SPEI showed identical drought years (2002 extremely severe of the two seasons seem to have 10 year cycles and the moderate dry years came six years after the severe drought years. Nearly 50% of the time there were start of season failures, which partly contributed to t generally stronger during El Nino years dominated by El Nino dominance period and when ENSO was positive. Since it is roughly possible to predict these events, it is possible to roughly predict the drought years but it may sti intensities.
Abstract: This study was conducted to assess change in rainfall, temperature and relative humidit... more Abstract: This study was conducted to assess change in rainfall, temperature and relative humidity at Bahir Dar city in relation to global climate change. The study focused on analyzing changes in meteorological data, specifically temperature, rainfall and relative humidity. Bahir Dar city was selected due to its proximity to Lake Tana and its rapid urbanization over the past few decades. Debre Markos city (with no lake nearby) was selected for comparison, to assess the thermal inertia effect of the lake on Bahir Dar. The assessments in this study showed that Bahir Dar city has experienced mean temperature change of about 0.4 oC per decade, which is higher than the global average (0.08 oC per decade) and a decrease in rainfall of about 30 mm per decade. Monotonic increment of minimum temperature (0.60 oC decade-1) surpassed that of maximum temperature (0.25 oC per decade) and this was further confirmed by a decrease in change of diurnal temperature range of -0.34 oC per decade. The ...
Issues around geometry of the universe, density of the universe (Underweight), expansion of the u... more Issues around geometry of the universe, density of the universe (Underweight), expansion of the universe and theories held-up by scientists such as Stephen Hawking, John Wheeler, Albert Einstein, etc have been looked into. The equations formulated by these people; that is E =mc 2 , E = hν and PV = nRT were treated to give meaning under the general truth that the universe has only two entities; MATTER and ENERGY and HEAT and COLD to manipulate them. The Energy x Time oMatter x Space relationships is suggested in this paper in place of, Energy.Matter = Space.Time, which was summarized by Albert Einstein. The three dimensionness of space were incorporated into E = mc 2 to give E/N Ξ c 3 . E = hc/λ o which had the notion of space divided by space is re-related to space per time and PV = nRT is revisited until it was modified to be in congruent with the above two fundamental formulations; that is PVΞ KT/N. These new relationships ( THEORIES ) are in agreement with each other and could be...
This study was conducted at Haramaya University to assess the levels of physical water quality pa... more This study was conducted at Haramaya University to assess the levels of physical water quality parameters in water samples collected from four wells, the main water reservoir and taps delivering water to three zones of the campus. The physical water quality parameters examined were total solids, dissolved solids, suspended solids, turbidity, pH and electrical conductivity. Besides, heating and cooling temperatures at which most of the solids could be extracted were also tested. The results from the wells were compared pair-wise and likewise the results of each water sample from the three zones with the water sample from the main reservoir. One of the four wells (W3) and two of the distribution zones (Z1 and Z2) had total solids in excess of 1000 mg L-1. All the sampling sites showed dissolved solids in excess of 500 mg L-1. Suspended solids at all the sites accounted for less than 25% of the total solids. One of the wells (W3) showed significant difference (P < 0.05) from the res...
The use of FAO-56 Penman-Monteith (PM) equation is the recommended equation to estimate potential... more The use of FAO-56 Penman-Monteith (PM) equation is the recommended equation to estimate potential evapotranspiration. However, when data that satisfy the PM equation is not available or incomplete, the use of PM equation is not an option. In this study, one such method known as Temesgen-Melesse's (TM) method was assessed in relation to the PM equation using data of eight class-I meteorological stations in Ethiopia. In the study, first the problems with this method were identified and the TM equation was modified. The modifications made were replacement of the average maximum temperature at the denominator of the equation varying with time with the average of Tmax for each location (which is a constant for a given location). The Second consideration was calibrating the power of the maximum temperature at the numerator using PM data instead of taking it as a constant 2.5 suggested by the authors in their original equation. Then the three (the original TM, the modified TM with constant power of 2.5 and the modified TM with the power calibrated) methods were fitted against PM equation. Thereafter tests using statistical parameters, model tendency parameters and model performances were carried out. The results indicate the modified TM equation to be better than the original TM equation in terms of percent slope (0.8-12.3 against 1.3-15.1) and the correlation coefficient (R 2 ) and the slope (100% good or satisfactory against 25%). The modified and calibrated equation gave best results in terms of percent error by slope (0.5-2.3), by coefficient of efficiency (100% good or satisfactory), by R 2 and slope (100% good or satisfactory) and by mean percent error (5.7-13.6%). Therefore, whenever data that satisfy PM equation are available (even if for limited years), it is better to calibrate the power of the maximum temperature and to consider more decimal places rather than taking 2.5 as suggested by the authors. When data is not available it is better to use the modified TM equation rather than using the original TM equation. The study would benefit those who want to study long-term climate changes and drought patterns, which involve the use of evapotranspiration with limited data that satisfy the PM equation, but have long-term data of temperature.
The use of FAO56-PM is still the preferred method for the estimation of evapotranspiration (ET) r... more The use of FAO56-PM is still the preferred method for the estimation of evapotranspiration (ET) regardless of locations. But in places where data that satisfy all the meteorological variables of PM equation are non-existent or missing, the use of either temperature or radiation-based methods is the alternative option, since both radiation and temperature are the main drivers of ET. From the latter two, temperature-based ET estimation methods are still the simplest ones to use. However, there are challenges since some of the parameters used in the temperature-based equations are location dependent. Such location dependence is due to variability in terms of latitude, altitude and other geo-location parameters. Therefore, local calibration of temperature-based methods is necessary to get better estimates of ET. In this study, one temperature-based ET estimation method known as Temesgen-Melesse's (TM) method was assessed in relation to the PM equation using data of ten Class I meteorological stations in Ethiopia. In the study, three different techniques were tested to find location-dependent maximum temperature power ('n') used in TM equation (i.e., to calibrate the method). The first two techniques involve calibration using PM data. In the first case, monthly averaged data that span from 1 to 5 years were used (as five data sets of 12, 24, 36, 48 and 60 months). In the second case, daily values that span from 10 to 30 days were used in three groups of 10-, 20-, and 30-day data sets. In the third technique, an attempt was made to estimate 'n' from the location latitude, altitude and average of the monthly averaged maximum temperature (T̄m x ). The results obtained from each technique are given as follows. Calibration from the monthly averaged data gave good 'n' values for all the stations with R 2 values ranging from 0.80 to 0.92. There were no differences in the number of data points 36, 48 and 60 months) used, which means data points of 12 months are sufficient for the calibration. Calibration using the daily data gave satisfactory 'n' results for all the stations tested, though the statistical parameters and performance tests did not give results that are comparable to the monthly averaged values. The results were nearly the same for 10-, 20-, or 20-day data points, which means any one of them can be used for calibration purposes. Estimation of 'n' from latitude, altitude and T̄m x gave results that are comparable to the ones with 'n' calibrated. The percent differences between the 'n' calibrated using data of 131 months and the 'n' values obtained from monthly data and daily data calibrations are less than 0.16% and 0.5%, respectively. The calculated 'n' showed a percent difference of less than 1.1%. Using calculated 'n' is better than performing calibration using daily data. It can also be considered as option when at least 1-year PM data are not available for calibration.
Radiation is what everyone encounters every day both from natural and from manmade sources. Thoug... more Radiation is what everyone encounters every day both from natural and from manmade sources. Though little could be done to limit radiation from natural sources, limit should be made on radiation levels from man-made sources. In this study, radiation level assessments were made on 19 construction metals, 9 kitchen items and three groups of electronic items using Universal Survey Meter. Radiation rates from each item were measured at four different distances (10, 20, 30 and 40 cm) from the source. Background radiations were measured once daily and the background radiations were subtracted from the daily measured radiation rates of the items to get net radiations, from which dose levels were evaluated. The result (in terms of radiation rate variability with distance) showed radiation levels in excess of the background radiation even though the values were not consistent. The result revealed 12 of the metals, 2 of the kitchen items and one group of electronic items to have doses above t...
Radiation is what everyone encounters every day both from natural and from manmade sources. Thoug... more Radiation is what everyone encounters every day both from natural and from manmade sources. Though little could be done to limit radiation from natural sources, limit should be made on radiation levels from man-made sources. In this study, radiation level assessments were made on 19 construction metals, 9 kitchen items and three groups of electronic items using Universal Survey Meter. Radiation rates from each item were measured at four different distances (10, 20, 30 and 40 cm) from the source. Background radiations were measured once daily and the background radiations were subtracted from the daily measured radiation rates of the items to get net radiations, from which dose levels were evaluated. The result (in terms of radiation rate variability with distance) showed radiation levels in excess of the background radiation even though the values were not consistent. The result revealed 12 of the metals, 2 of the kitchen items and one group of electronic items to have doses above t...
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