Performance investigation of salt gradient cylindrical solar pond integrated and nonintegrated with evacuated tube solar collectors

In this study, the energetic and exergetic efficiencies of a salt gradient cylindrical solar pond (SGCSP) that integrated and nonintegrated evacuated tube solar collectors (ETSCs) are investigated to improve daily heat preservation performance of the heat storage zone (HSZ). The integrated system is consisted of an SGCSP and four ETSCs. The SGCSP has a surface area of 2 m2, a depth of 1.65 m, salty water layers at different densities, and HSZ in which the cylindrical serpentine type heat exchanger (CSHE) is located. Thus, the daily effects of the heat storage performance of both the ETSCs and the SGCSP in the winter season was determined experimentally. The analysis of the data regarding the efficiencies of the system is investigated separately by means of experimental studies where the SGCSP is integrated and nonintegrated with the ETSCs. The number of ETSCs integrated with SGCSP is increased to 1, 2, 3, and 4, respectively, and each of the five different experimental systems is performed separately. The temperature distributions of the integrated system are measured by a data acquisition system on 11 different points per hour. The efficiencies are calculated using the data obtained from these studies. Consequently, the energetic and exergetic efficiencies of the SGCSP are obtained without collectors as 10.4% and 4.3% and with one collector as 12.83% and 6.15%, with two collectors 14.88% and 8.25%, with three collectors 16% and 9.35%, and finally with four collectors 16.94% and 10.3%, respectively. Furthermore, the theoretical efficiencies are found to be consistent with the experimental results obtained by increasing the collector numbers. © 2019 John Wiley & Sons, Ltd.The authors acknowledge the support provided by Cukurova University in Turkey (Grant Nos. FEF2009D2, FEF2010BAP5, and FEF2012D20)

An investigation of the effect of transparent covers on the performance of cylindrical solar ponds

The effect of the transparent covers (glass, polycarbonate, and mica) on the small cylindrical solar pond performance is studied. The temperature and density distributions are measured to evaluate the performance of the covered cylindrical solar pond. The pond covers provide a significant potential for energy savings and storage by insulating upper convective zone. Thus, such transparent covers are used for reducing the thermal energy losses from the top surface of the cylindrical solar pond. The transmission, reflection, and absorption coefficients of the covers are calculated to determine the monthly solar energy contents of the solar pond. The energy efficiencies of the solar pond are found for each type of covers from November 2008 to March 2009. As a result, the highest efficiency is determined to be 17.86% for glass cover in March, while the efficiencies of polycarbonate and mica become 16.95% and 15.86%, respectively. In this regard, the glass cover appears to be the best option for the solar ponds.Council for Higher Education FEF 2009 D2, FEF 2004 BAP4, FEF 2010 BAP5 University of Ontario Institute of TechnologyThe authors acknowledge the support provided by University of Cukurova (Grant Nos: FEF 2004 BAP4, FEF 2009 D2, and FEF 2010 BAP5), the Council of Higher Education in Turkey, and University of Ontario Institute of Technology in Canada

Assessment of electricity and hydrogen production performance of evacuated tube solar collectors

In this work, a unified renewable energy system has designed to assess the electricity and hydrogen production. This system consists of the evacuated tube solar collectors (ETSCs) which have the total surface area of 300 m2, a salt gradient solar pond (SGSP) which has the surface area of 217 m2, an Organic Rankine Cycle (ORC) and an electrolysis system. The stored heat in the heat storage zone (HSZ) transferred to the input water of the ETSCs by means of an exchanger and thereby ETSCs increase the temperature of preheated water to higher level as much as possible that primarily affects the performance of the ORC. The balance equations of the designed system were written and analyzed by utilizing the Engineering Equations Solver (EES) software. Hence, the energy and exergy efficiencies of the overall system were calculated as to be 5.92% and 18.21%, respectively. It was also found that hydrogen generation of the system can reach up to ratio 3204 g/day. © 2018 Hydrogen Energy Publications LL

Investigation energy, exergy and electricity production performance of an integrated system based on a low-temperature geothermal resource and solar energy

In this work, energy, exergy and electricity generation performance of an integrated system was conceptually investigated by using Engineering Equation Solver (EES)under 200–1000 W/m2 solar irradiation interval. The system comprises evacuated tube solar collectors (EVTSCs)with the surface area of 100 m2, an organic Rankine cycle (ORC)and a low-grade geothermal resource. The EVTSCs were used to enhance the temperature of the low-grade water coming from the geothermal source. The calculations were carried out for three geothermal sources in Kula (63 °C), Saraycık (74 °C)and Turgutlu (86 °C), respectively. N-hexane, n-pentane and n-butane were selected as a working fluid in the ORC. It was determined that the selection of the working fluid affected the performance of the ORC. And also, the waste heat is extracted from the ORC were used efficiently for space heating. As a result, the overall energy and exergy efficiencies of the system and power generation of the ORC were seriously affected by enhancing the water temperature of the geothermal resources by EVTSCs. The maximum overall energy and exergy efficiencies of the system were calculated as to be 6.92% and 21.06% by using n-butane for the source in Turgutlu, respectively. The minimum overall energy and exergy efficiencies of the system were calculated as 0.32% and 2.19% by using n-hexane for the source in Kula, respectively. The maximum and minimum generated electricity were calculated as to be 19.46 kW and 0.6168 kW for the sources in Turgutlu and Kula, respectively. It was seen that the best performance of the system was found for n-butane compared to n-pentane and n-hexane. © 2019 Elsevier Lt

Performance assessment of a solar pond with and without shading effect

In this study, we present an experimental investigation of energy distribution, energy efficiency and ratios of the energy efficiency with respect to shading effect on each zones of a small rectangular solar pond. The system is filled with salty water in order to form upper convective, non-convective and lower convective zones. A data acquisition device is used to measure and record the hourly temperatures at various locations in different solar pond zones (distributed vertically within and at the bottom of the pond, and horizontally and vertically within the insulated side-walls). A shading model is developed to gain a more profound understanding of the energy performance of the pond. The model results of the each zone are compared with and without shading effect, based on the corresponding energy efficiencies. The shading surface area of the zones does not contribute to the thermal performance of the pond but it takes place non-sunny area in the zones by shading. Thus, the efficiency of the solar pond decreases with increasing the shading area. The energy efficiencies of the inner zones with and without the shading effect for each zone in the energy analysis are specified as the average representative solar energy for each month of the year. The highest energy efficiencies for the cases of with and without shading area are found for the month of August to be: 4.22% and 4.30% for the upper convective zone, 13.79% and 16.58% for the non-convective zone, and 28.11% and 37.25% for the lower convective zone, respectively. The results confirm that the solar pond storage efficiency can be increased by eliminating the effect of shading area. Moreover, the ratios of shading effect are found to be: 0.651 at the lower convective zone, 0.279 at the non-convective zone and 0.068 at the upper convective zone. © 2012 Elsevier Ltd. All rights reserved.FEF 2009 D2, FEF 2004 BAP4, FEF 2010 BAP5The authors acknowledge the support provided by University of Cukurova in Turkey (Grant Nos: FEF 2004 BAP4, FEF 2009 D2 and FEF 2010 BAP5), the Council of Higher Education in Turkey and University of Ontario Institute of Technology in Canada

Investigation of turbidity effect on exergetic performance of solar ponds

The present paper undertakes a study on the exergetic performance assessment of a solar pond and experimental investigation of turbidity effect on the system performance. There are various types of solar energy applications including solar ponds. One of significant parameters to consider in the assessment of solar pond performance is turbidity which is caused by dirty over time (e.g., insects, leaf, dust and wind bringing parts fall down). Thus, the turbidity in the salty water decreases solar energy transmission through the zones. In this study, the samples are taken from the three zones of the solar pond and analyzed using a spectrometer for three months. The transmission aspects of the solar pond are investigated under calm and turbidity currents to help distinguish the efficiencies. Furthermore, the maximum exergy efficiencies are found to be 28.40% for the calm case and 22.27% with turbidity effects for the month of August, respectively. As a result, it is confirmed that the solar pond performance is greatly affected by the turbidity effect. © 2014 Elsevier Ltd. All rights reserved.The authors acknowledge the support provided by the University of Cukurova under a Grant (Nos. FEF2009D2, FEF2010YL26 and FEF2010BAP5 )