Renewable Energy Resources and Technologies
Mehran Gheyrati; Asadollah Akram; Hassan Ghasemi-Mobtaker
Abstract
The orientation of greenhouses is one of the effective factors in terms of radiation they receive. In the present study, a multi-span greenhouse (40 m × 93.5 m with a coverage area of 5457.44 m2) located in the central region of Iran was investigated in three orientations including: North-South ...
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The orientation of greenhouses is one of the effective factors in terms of radiation they receive. In the present study, a multi-span greenhouse (40 m × 93.5 m with a coverage area of 5457.44 m2) located in the central region of Iran was investigated in three orientations including: North-South (N-S), East-West (E-W), and Northeast-Southwest (NE-SW: the most frequent orientation of the existing greenhouses in the study area). The solar irradiation received on the outside surface of the greenhouse cover and the amount of irradiation captured inside the greenhouse for each orientation during the cold season were calculated using mathematical modeling and the results were compared. According to the results, in the E-W orientation, the main sections of receiving solar irradiation, such as the south and north roofs, have a better angle toward the sun; therefore, the quantity of solar irradiation captured inside the greenhouse with the E-W orientation was on average 361.48 MJ day-1 more than that with the N-S orientation. The north wall of the greenhouse could not receive the beam radiation for all the orientations investigated, and the total irradiation captured by this section was composed of the diffused radiation and the ground-reflected radiation, which is an important result for insulation of some surfaces of greenhouses.
Hassan Ghasemi Mobtaker; Yahya Ajabshirchi; Seyed Faramarz Ranjbar; Mansour Matloobi; Morteza Taki
Abstract
Precise knowledge ofthe amount of global solar radiation plays an important role in designing solar energy systems. In this study, by using 22-year meteorologicaldata, 19 empirical models were tested for prediction of the monthly mean daily global solar radiation in Tabriz. In addition, various ...
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Precise knowledge ofthe amount of global solar radiation plays an important role in designing solar energy systems. In this study, by using 22-year meteorologicaldata, 19 empirical models were tested for prediction of the monthly mean daily global solar radiation in Tabriz. In addition, various Artificial Neural Network (ANN) models were designed for comparison with empirical models. For this purpose, the meteorological data recorded by Iran Meteorological Organization (1992–2013) was used. These data include: monthly mean daily sunshine duration, monthly mean ambient temperature, monthly mean maximum and minimum ambient temperature and monthly mean relative humidity.Theresults showed that the yearly average solar radiation in the region was 16.37 MJ m .Among the empirical models, the best result was acquired for model (19) with correlation coefficient (r) of 0.9663. Results also showed that the ANN model trained with total meteorological data in input layer (ANN5) produces better results in comparison to others. Root Mean Square Error (RMSE) and r for this model were1.0800 MJ m-2 and 0.9714, respectively. Comparison betweenthe model 19 and ANN5, demonstrated that modeling the monthly mean daily global solar radiationthrough the use of the ANNtechnique, yields better estimates. Mean Percentage Errors (MPE) for these models were 7.4754% and 1.0060%, respectively. -2 day-1