Osman Yaldiz

MATHEMATICAL MODELING OF THIN LAYER SOLAR DRYING OF SULTANA GRAPES

Thin layer solar drying experiments were conducted for Sultana grapes (cv. Thompson seedless) grown in Antalya, Turkey. An indirect forced convection solar dryer consisting of a solar air heater and a drying cabinet was used in the experiments. Air heated by the solar air heater was forced through the product by an electric fan. In order to examine the effect of drying air temperature and velocity on a thin layer drying of Sultana grapes, twenty-two experiments were performed. Eight different thin layer mathematical drying models were compared according to their coefficient of determination to estimate solar drying curves. The effects of drying air temperature and velocity on the model constants and coefficients were predicted by the regression models. According to the results, a two-term drying model could satisfactorily describe the solar drying curve of Sultana grapes with a correlation coefficient (r) of 0.979. The constants and coefficients of this model could be explained by the effect of drying air temperature and velocity.

Comparison of some existing models for estimating global solar radiation for Antalya (Turkey)

Abstract Solar radiation data for Antalya (36°53′ N, 30°42′ E) in Turkey were used to test the applicability of twenty six models available for computing the monthly average daily global radiation on a horizontal surface. The models were compared on the basis of statistical error tests using the mean percentage error (MPE), root mean square error (RMSE) and the mean bias error (MBE). According to our results, the Samuel model below (Samuel T.D.M.A. Estimation of global radiation for Srilanka. Solar Energy 1991;47(5):333) showed the best estimation of global solar radiation on a horizontal surface for Antalya by means of the MPE (1.5%), RMSE (0.27 MJ/m 2 ) and MBE (−0.02 MJ/m 2 ) statistical tests: H H 0 =−2.4275+11.946 S S 0 −16.745 S S 0 2 +7.9575 S S 0 3

Estimation of monthly average daily global radiation on horizontal surface for Antalya (Turkey)

In this study, multiple linear regression models were used to estimate the monthly average daily global radiation using nine different variables for Antalya, Turkey; the extraterrestrial radiation, solar declination, mean relative humidity, ratio of sunshine duration, mean temperature, mean soil temperature, mean cloudiness, mean precipitation and mean evaporation. The results showed that the models can estimate global radiation within relative error (|e|) of −5.7 and 3.9%, a mean error (MPE) of 2.0% and root-mean square error (RMSE) of 2.5% for Antalya.

Composting of spent mushroom compost, carnation wastes, chicken and cattle manures

This study has purposed to determine the optimum mixture ratio of used mushroom compost, chicken manure, cattle manure and carnation waste for composting. For this purpose, these materials have been mixed in seven various ratios (R1-R7) and composted in the experimental composting reactors. The highest dry material losses and temperature values have been obtained by the R4 which contains 50% carnation waste, 25% chicken manure and 25% spent mushroom compost. Beside R4, mixtures of R2, R5 and R6 have also provided high process temperature and dry material loss values. The lowest dry material loss and temperature values have been obtained in the R7 which contains only carnation wastes. In the study, it has also seen that FAS (free air space) parameter is effective on the process and must be in the interval of 24-32%.

The prospective of potential biogas plants that can utilize animal manure in Turkey

The feasibility study of potential biogas plants was conducted on a nationwide scale that may be established in each province of Turkey using potentially 10% of all annually collected animal manure. The analysis was carried out using the centralized anaerobic digestion model at thermophilic temperatures. Both equations and data used to calculate the capital and operating cost of biogas plants, as well as combined heat and power system were obtained from the available literature. The production of methane, electrical and heat energy, digestate, revenues, and CO2 savings due to biogas process were evaluated. The economic viability of biogas plants was evaluated based on the net present value (NPV), benefit-to-cost ratio (B/C ratio), internal rate of return (IRR), and payback period (PBP) based on the inclusion and exclusion of heat revenues at two different electricity purchase prices (0.066 and 0.11 ş/kWh). The results showed that the highest amounts of electrical and heat energy generated were for East Marmara (380.22 GWhe/year and 434.54 GWht/year), respectively, while those of the lowest production were for Istanbul region, 5.25 (GWhe/year), and 6.00 (GWht/year), respectively. The revenues from the produced electrical energy ranged from 0.35 Million Euros per year for Istanbul region to 25.09 Million Euros per year for East Marmara region while the heat revenues from biogas production ranged from 0.20 Million Euros per year for Istanbul region to 14.43 Million Euros per year for East Marmara region. It has been concluded that certain financial mechanisms have to be put into effect, such as increasing market price of electricity produced from biogas plants to give an incentive to biogas producers, as well as fundraising to support construction of biogas plants, and offering both long-term credits and tax breaks for investors.

Methane Production from Plant Wastes and Chicken Manure at Different Working Conditions of a One-stage Anaerobic Digester

Abstract This article presents laboratory scale studies on the anaerobic digestion of plant wastes using a continuously flow type vertical cylindrical biogas plant. In the first experiment, plant wastes and chicken manure mixture at a dry matter content of 12%, retention time of 30 days, and fermentation temperature of 35°C were examined (Exp. 1). In the second experiment, fermentation material was grass and grass silage, covered marketplace wastes, rumen waste, chicken manure, and cattle manure. The experiments were conducted at a dry matter content of 9%, retention time of 47 days, and fermentation temperature of 35°C (Exp. 2). According to the results, biogas production was 1,055.7 l per day in Exp. 1 and 721.4 l per day in Exp. 2. The raw material specific biogas production was 0.310 l per g of organic dry matter per day in Exp. 1 and 0.443 l per g of organic dry matter per day in Exp. 2. The reactor specific biogas production was 1.05 l per l per day in Exp. 1 and 0.72 l per l per day in Exp. 2. Reactor specific methane production was 0.425 l per l per day in Exp. 1 and 0.381 l per l per day in Exp. 2. Raw material specific methane production was 0.125 l per g of organic dry matter per day in Exp. 1 and 0.234 l per g of organic dry matter per day in Exp. 2. The material pH value was 5.59 and 6.15 for inlet and 7.97 and 8.19 for outlet for Exp. 1 and Exp. 2, respectively. The methane content ranged between 40.3 and 52.9%.