E. Kavak Akpinar

A Statistical Investigation of Wind Energy Potential

In this study, wind speed data from four stations, which are located in Elazig and its close regions, are analyzed. Data are fitted to the Weibull and Rayleigh probability distribution functions. Probability distribution functions are derived from cumulative function and used to calculate the mean wind speed and variance of the actual data. The best way of representing the performance of Weibull and Rayleigh distributions is to use the statistical parameters such as the correlation coefficient (R 2), chi-square (χ2) and root mean square error analysis (RMSE). The annual mean wind speed and power are 5.66 m/s and 246.27 W/m2 for Maden, 3.86 m/s and 98.90 W/m2 for Agin, 3.14 m/s and 41.37 W/m2 for Elazig, 2.27 m/s and 15.83 W/m2 for Keban. Maden has good wind energy potential when it is compared with the other three regions. In general, wind speed is higher during the summer months, notably June and July, and is lower during some winter and spring months. However, for the whole stations, Weibull distribution function was found to be better than Rayleigh distribution function.

An Analysis of the Wind Energy Potential of Elazig, Turkey

Abstract In this study, the wind energy potential of Elazig is statistically analyzed based on hourly measured wind speed data over the five-year period from 1998 to 2002. The probability density distributions are derived from cumulative distribution functions. Two probability density functions are fitted to the measured probability distribution on a yearly basis. The wind energy potential of the location is studied based on the Weibull and Rayleigh distributions. It was found that the numerical values of both Weibull parameters (k and c) for Elazig vary over a wide range. The yearly values of k range from 1.653 to 1.878 with an average value of 1.819, while those of c are in the range of 2.757–2.994 m/s with an average value of 2.824 m/s. In addition, yearly mean wind speed and mean power density of Elazig is found as 2.79 m/s and 38.76 W/m2, respectively. The wind speed distributions are represented by Weibull distribution and also by Rayleigh distribution, with a special case of the Weibull distribution for k = 2. As a result, the Rayleigh distribution is found to be suitable to represent the actual probability of wind speed data for Elazig.

An Assessment of Wind Turbine Characteristics and Wind Energy Characteristics for Electricity Production

This work is an analysis of wind turbine characteristics and wind energy characteristics of four regions around Elazig, Turkey, namely Maden, Agin Elazig and Keban. Wind speed data and wind direction in measured hourly time-series format is statistically analyzed based on 6 years between 1998 and 2003. The probability density distributions are derived from time-series data and distributional parameters are identified. Two probability density functions are fitted to the measured probability distributions. The wind energy characteristic of all the regions is studied based on the Weibull and the Rayleigh distributions. Using the Weibull probability density function, we estimated the wind energy output and the capacity factor for six different wind turbines between 300 and 2300 kW during the six years. It was found that Maden is the best region, among the regions analyzed, for wind energy characteristic and wind turbine characteristic.

Application of moisture transfer models to solids drying

Abstract In this paper, a comprehensive experimental investigation is conducted to measure the moisture content distributions within slab cut potato pieces during drying at temperatures of 60, 70, and 80°C and flow velocities of 1.0 and 1.5 m/s. Four drying models are employed to determine the drying process parameters (drying coefficient, lag factor, and half-drying time) and moisture transfer parameters (moisture diffusivity and moisture transfer coefficient), and to calculate moisture content distributions and compare them with extensive sets of experimental moisture data measured during the drying of slab cut potato slices at different drying air temperatures and flow velocities. Good agreement is obtained between the calculations and experimental measurements for the cases. In addition, experimental drying times are determined and compared with those obtained by the four different drying models. The results show that all four models are well able to determine the drying parameters and moisture content distributions. The experimental data and model findings are expected to be useful to the drying industry.

Energy and Exergy Aanalyses of Drying of Eggplant Slices in a Cyclone Type Dryer

In this paper, the energy and exergy analyses of the drying process of thin layer of eggplant slices are investigated. Drying experiments were conducted at inlet temperatures of drying air of 55, 65 and 75°C and at drying air velocities of 1 and 1.5 ms-1 in a cyclone type dryer. Using the first law of thermodynamics, energy analysis was carried to estimate the ratios of energy utilization. However, exergy analysis was accomplished to determine type and magnitude of exergy losses during the drying process by applying the second law of thermodynamics. It was deduced that eggplant slices are sufficiently dried in the ranges between 55-75°C of drying air temperature and at 1 and 1.5 ms-1 of drying air velocity during 12000-21600 s despite the exergy losses of 0-0.739 Us-1.