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Annals of West University of Timisoara - Physics
The Journal of West University of Timisoara
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Comparison Between Measurements and WRF Numerical Simulation of Global Solar Irradiation in Romania

References [1] V. Badescu and A. Dumitrescu, "Testing Magicsol under the climate and latitudes of Romania", COST Action ES1002 "WIRE", Workshop on Remote Sensing Measurements for Renewable Energy, Technical University of Denmark DTU, Wind Energy Department Riso campus, Roskilde, Denmark, May 22-23, 2012. [2] L. Martin, L. F. Zarzalejo, J. Polo, A. Navarro, R. Marchante, M. Cony, "Prediction of global solar irradiance based on time series analysis: Application to solar thermal power plants energy production planning", Solar

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LIDAR Measurements Comparison Of Two Volcanic Eruptions: Environmental Influences Upon The Romanian Territory

Abstract

The eruption of both the Eyjafjallajokull (April 2010) and Grimsvotn (May 2011) volcanoes cumulated with two moments that gave headaches to the authorities and air traffic, and their impact on the environment upon Iasi region have been studied by means of different tools evidencing the complexity of the phenomena. In order to evidence the intrusion of pollutants in the cloud systems and to obtain additional data on the intrusion when the ash cloud was over our country, LIDAR measurements, meteorological (NMA), Satellite data (EUMETSAT), and various forecasting models (ECMWF, VAAC-Met Office, HYSPLIT) have been used. The new 3D Atmospheric Observatory Site of the Alexandru Ioan Cuza University of Iasi, as part of RADO (Romanian Atmospheric 3D Observatory) is presented, too.

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Experimental Assessment of the Meliss Simulation Model Accuracy of the Direct Solar Irradiance in Brasov, Romania

Abstract

The solar irradiance is the main input parameter when designing solar energy conversion systems. A poor accuracy of the solar irradiance simulation models negatively affect the output energy and the durability of the solar energy conversion system. In the paper, the measured values of the direct solar irradiance in the entire month of July 2016 are analysed and, based on the daily received direct solar energy and the variability of the direct solar irradiance, the days are classified in four categories: clear sky days, partially clear sky days, partially cloudy days and cloudy days. Based on this classification, only four clear sky days were identified in July 2016. The same procedure was applied for the months of July 2013, 2014 and 2015 resulting 13 clear sky days in the entire monitoring period of four years (2013-2016). The measured values of the direct solar irradiance in these 13 selected clear sky days are comparatively analysed against the direct solar irradiance simulated with Meliss clear sky model. Further on, a statistical analysis is performed for the time interval 8:00-16:00 to evaluate absolute, relative and root mean square errors between the measured and simulated values. The results show that the simulation model overestimates, in eleven out of the thirteen clear sky days, the solar direct irradiance in the central part of the day. The measurements were performed in the Renewable Energy Systems and Recycling (RESREC) Research Centre located in the R&D Institute of the Transilvania University of Brasov, Romania.

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Modeling of Daily Global Solar Irradiation in Timisoara by Using a Fuzzy Approach

Abstract

This paper proposes a new simple model to forecast daily global solar irradiation one day ahead using the Takagi-Sugeno fuzzy methods. The model is based on solar radiation data measured in Timisoara, Romania. The daily clearness index represents the direct variable used by the fuzzy algorithm. The model forecasts the clearness index at the moment of time t on basis of two previous values measured at time t-1 and t-2. An assessment of the model accuracy is performed.

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Online Forecasting of the Solar Energy Production

Abstract

Forecasting the solar energy production is a key issue in the large-scale integration of the photovoltaic plants into the existing electricity grid. This paper reports on the research progress in forecasting the solar energy production at the West University of Timisoara, Romania. Firstly, the experimental facilities commissioned on the Solar Platform for testing the forecasting models are briefly described. Secondly, a new tool for the online forecasting of the solar energy production is introduced. Preliminary tests show that the implemented procedure is a successful trade-off between simplicity and accuracy.

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Improving The Accuracy of the Empirical Clear Sky Solar Irradiance Models

References [1] Solar Radiation Monitoring Station of the West University of Timisoara, Romania http://solar.physics.uvt.ro/srms [2] M. Kottek, J. Grieser, C. Beck, B. Rudolf, F. Rubel, Meteorologische Zeitschrift 15 (2006) 259. [3] V. Badescu, Theoretical and Applied Climatology 72 (2002) 127. [4] M Paulescu, V Badescu, Theoretical and Applied Climatology 103 (2011) 459. [5] M. Paulescu, Z. Schlett, Renewable Energy 29 (2004) 767. [6] M. Paulescu, Z. Schlett

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Fluid Flow Control in Domestic Hot Water Systems During Days with Different Radiative Stability Levels

Abstract

This paper presents models/strategies for optimum performance of solar collector in closed loop systems. These models aim to maximize the obtained energy by thermal conversion of solar energy. The mass flow rate of the fluid from the primary circuit of the system is the control parameter. The semi empirical models and optimal control methods are in brief presented. The volume of the storage tank is important and the ratio Vs/Ac between this volume and area of the collectors is a key factor in appropriate sizing of the DHW system. Therefore, the paper establishes a relationship between this ratio and the mass flow rate of the fluid in the collector This paper also analyses the variation of the energetic performance (useful heat flux transferred to the storage tank, heat flux transferred to the water, water temperature in the storage tank) with the volume of the storage tank. Analysis was performed on an extensive set of meteorological data from Timisoara, Romania, with instantaneous data (measured at 15 seconds) for summer days, from July 2009, with different relative sunshine values, σ. Important differences have been observed between days with different stability levels - days more or less stable.

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On The Information-Theoretical Entropy for Some Quantum Oscillators

References [1] A. Wehrl, Rep. Math. Phys. 16 (1979) 353. [2] D. Popov, Density matrix - General properties and applications in physics of many particle systems, Editura Politehnica, Timisoara, 2004 (in Romanian) [3] A. Miranowicz, H. Matsueda, M. R. B. Wahiddin, J. Phys. A: Math. Gen. 33 (2000) 5159. [4] V. P. Belawkin, O. Hirota, R. L. Hudson, Quantum Communications and Measurement, Plenum Press, New York (1995). [5] J. R. Klauder, J. Math. Phys. 4 (1963) 1055. [6

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