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Solar flat plate collectors are commonly used to transform solar energy into thermal one by heating a heat transfer fluid (HTF). The available thermal energy to the user is characterized by a certain thermal capacity and a certain temperature level. Comparing to the case of a single collector, when a higher thermal capacity is required in the user process, more collectors should be coupled in parallel, so that the HTF mass flow rate is increased, exiting the solar collector at the same temperature. Another case may be encountered when the user process requires the same mass flow rate of HTF, but at a higher temperature. In this last case, a series connection is considered. The aim of the present paper is to compare these cases and to build a solar panel map that could be used to choose the best arrangements for a specific user need. A study is performed regarding the map dynamics with respect to HTF consumption to the user for three storage tank capacities of 100L, 200L and 300L respectively. The results reveal a recommendation regarding collectors coupling function on user needs. [ABSTRACT FROM AUTHOR]

Storage processes are usually integrated in solar energy systemsapplications due to daily variation of this energy source availability. Among different thermal storage solutions, phase change materials (PCM) lately became more extensively used covering a wide range of operating temperatures. In this regard, a numerical simulation of a PCM melting process is performed under ANSYS CFD environment. A particular configuration is considered consisting in a 2m length annular tube having a 5.48 cm external diameter. The tube is filled with paraffin chosen as PCM. A concentric interior tube of 2.54 cm diameter is used for transporting the heat transfer fluid (HTF) from the solar collector. Heat is transferred through the 1mm thick pipe wall to the PCM placed all around the HTF tube. The numerical results reveal the melting process of the PCM at different instances and tube sections. The time variation of the PCM liquid fraction is emphasized. The results describe the dynamic behavior of a PCM melting process and might be further integrated in any solar power plant storage charging process simulation. [ABSTRACT FROM AUTHOR]

This paper describes the development of a small-scale solar simulator for research and educational purposes. The main goal is to provide a uniform and stable distribution of irradiation from a set of four floodlight halogen lamps, over a targeted area of 40x40 cm². The floodlights are placed perpendicularly to each other, on the top end of a light tube. Two types of halogen lamps were characterised and the total irradiation of the solar simulator was measured over a 5x5 grid. The results showed that the two arrangements of lamps are able to achieve a level of 1000 W/m² on the 40x40 cm² targeted area, but the non-uniformity is unsatisfactory. In order to reach a non-uniformity level of 10% using the proposed lamps arrangements, the targeted area should be reduced to 31x31 cm². [ABSTRACT FROM AUTHOR]

The paper presents a comparative analysis of two solar powered systems aiming to produce electricity. The potential user could be a duplex house or an office building. One system consists of an Organic Rankine Cycle (ORC) modeled to operate at variable mass flow rate, constraint by the heat source temperature which is provided by a parabolic dish collector. The second one is a Stirling engine modeled by taking into account the internal and external irreversibilities, using the concentrated solar radiation from dish collector, too. Both engines have to deliver the same electrical power (constraint), according to the user's daily energy consumption profile. The study considers the daily solar radiation and ambient temperature variation under cloudy sky conditions, and the receiver heat losses dependence on these data. The analysis results emphasize the required solar collector dimensions in each case. The comparison is done to previous obtained results under clear sky conditions. [ABSTRACT FROM AUTHOR]

Daily operation of a solar powered simple effect one stage water - lithium bromide absorption cooling system is analyzed. The whole system is composed by a parabolic trough collector concentrating solar energy into a tubular receiver, a fully mixed thermal water storage tank and the absorption cooling system. Water is solar heated and stored to be used for maintaining the cooling system in operation as long as possible during the considered day. Time dependent cooling load is considered for the air conditioning of a residential two-storeys house. The aim is to correctly size the solar collector and storage tank and thus a parametric study is performed in this regard. The results emphasized high operation instability of the cooling system due to the large interval of variation for desorber temperature. Optimum dimensions of the storage tank associated to a specific solar collector dimension are determined to ensure the longest continuous startup operation of the cooling system. [ABSTRACT FROM AUTHOR]

The paper presents the effect of natural ventilation on the interior air temperature of a vegetable greenhouse located in Muntenia, Romania. Energy balance equation is applied for the greenhouse in order to determine the interior air temperature without adding any exterior heating or cooling load. The solar irradiance received by the greenhouse is estimated based on isotropic sky analysis models in clear sky conditions. Interior air temperature profile is numerically simulated all along a day, in winter and in summer. In order to maintain a constant optimum interior air temperature during vegetation, heating and respectively cooling loads are consumed. In order to diminish the cooling load, natural ventilation is generally applied. Different dimensions of the ventilation window are considered. A daily profile for optimum opening is proposed in order to maintain the interior air temperature as close as possible to the set value and thus to minimize the cooling load. [ABSTRACT FROM AUTHOR]