Emrah Deniz

An Investigation into the Effects of Box Geometries on the Thermal Performance of Solar Cookers

The effect of box geometry, such as cylindrical and rectangular, on the performance of solar cookers has not been investigated. In this study, two different model box type solar cookers, which are in rectangular and cylindrical geometries, were constructed using the same material and were tested to investigate the effects of box geometries on the cooker performance. The experimental studies were conducted under the same operating conditions. The obtained results from the experiments were used to calculate the thermal efficiency and specific and characteristic boiling times. These parameters of the cookers were determined for 0.5, 1, and 1.5 kg of fresh water. It is observed that the cylindrical model has higher temperatures than the rectangular model under the same operating conditions. The thermal efficiency increased from 12.7 to 36.98% for cylindrical and 9.85 to 28.25% for rectangular model, when the quantity of water was increased from 0.5 to 1.5 kg; similarly, the characteristic boiling time was decreased from 39.56 to 14.35 for the cylindrical and 43.74 to 15.77 (min m−2 kg−1) for the rectangular model, respectively. The cylindrical model provided high thermal performance, which is indicated by high thermal efficiency and low characteristic boiling time, in comparison with the rectangular model.

Performance parameters estimation of MAC by using artificial neural network

In this study, a modeling of a mobile air conditioner system in different amounts of refrigerant and in different compressor revolution speeds was carried out via artificial neural network (ANN). The three-layered ANN that is utilized in order to be able to model this system has 2 cells in its input layer and 3 cells in its output layer. The least problem-yielding ANN structure was analyzed by examining the number of cells in hidden layer from 6 to 19. The best result was obtained in the ANN with 10 hidden cells. A 0.945 was obtained in estimating coefficient of correlation cooling capacity, 0.985 was found in the power consumed in compressor, and 0.994 was established in COP estimation. The obtained correlation coefficients showed that ANNs can be used with a high precision in guessing the performance parameters of mobile air conditioner (MAC) systems.

An Experimental and Theoretical Analysis of a Vacuum Tube Solar Collector-assisted Solar Distillation System

Abstract The conventional distillation processes, such as multi effect evaporation, reverse osmosis, and electro dialysis, are not only energy intensive but also are uneconomical for small demands of fresh water. However, developments in the use of solar energy have shown that it is ideally suited for desalination, when the demand of fresh water is not so much. Distillation is one of the important methods of getting clean water from brackish and sea water using the free energy supply from the sun. A vacuum tube solar collector-assisted solar water distillation system was designed and tested under actual conditions of Turkey. This study is the first to use vacuum tube solar collectors in distillation systems. As expected, the vacuum tube solar collector increased the fresh water generation. Additionally, a mathematical model is presented and compared with experimental results. The model gives a good match with experimental values.

Energy and exergy analysis of flat plate solar collector-assisted active solar distillation system

AbstractDue to the fast increase in the world population, the need for the energy and water increases rapidly. Various studies have been made to meet this extra energy and water demand. Most of these studies have focused on solar energy and solar driven desalination systems. Solar water desalination is a well-known and proven technique which has been used for a long time at remote areas and places suffering from shortage of potable quality water. In this study, a flat plate solar collector-assisted water distillation system was designed and tested under actual conditions and its energy and exergy efficiencies were analyzed, which is the main contribution of this study to the literature related to solar desalination systems. The system works under closed cycle in order to prevent efficiency losses caused by internal fouling in both solar collector and distillation unit. The maximum daily energy efficiency of the system was obtained as 48.1% and the maximum exergy efficiency was found as 2.76% for optimum f...

Solar-Powered Desalination

Drinkable fresh water, being a fundamental need of human beings, has become a serious concern for people especially living in crowded cities and countries with limited amount of water resources. Supplying fresh water is an energy intensive task especially when there is need for heating cold water to evaporate for distillation. Most of the big desalination plants around the world use fossil-based fuels as energy source to heat and vaporize the sea water or brackish water in order to produce fresh water. However, environmental concerns along with decreasing oil reserves and increasing fuel costs call for reconsideration on the fuel types used in many areas as well as in desalination or distillation processes. There are a number of well-known alternative and renewable energy sources in the world like wind, geothermal, solar, biomass, etc. but achievability, availability when needed and energy storage are also very critical issues to operate the distillation plant effectively. Since most of the desalination processes run on heat, solar energy can be used directly as heat source. Complex desalination systems which are all designed to improve the thermal efficiency and freshwater yield/productivity use many approaches such as multiple stage operation, pre-heating the feed water with the condensation energy, using additional heat sources (waste water from another process), concentrating solar energy to improve the operation temperature of the process, etc. Solar desalination systems can be a good solution to the water scarcity, especially the Sunbelt region. However, dominant use of clean and renewable energy sources for desalination process and replacing the fossil fuel–based operations require more R&D studies to find more efficient and/or less costly power plants with continuous operation by the means of energy storage solutions.

Solar radiation exergy and enviroeconomic analysis for Turkey

The knowledge of useful solar energy amount is important for designing solar energy systems. In this study, solar radiation exergy (SRE) values are calculated for the 81 cities in Turkey. The data are obtained from the General Directorate of Renewable Energy and the General Directorate of Meteorology. The approaches of Petela, Spanner and Jeter are used to calculate the exergy-to-energy ratios for determining the maximum utilisable solar radiation energy. The exergy-to-energy ratios, the SRE values, the locations having the highest solar exergy potential and the monthly, seasonal and annual total SRE maps are presented for Turkey. Finally, enviroeconomic analysis is performed and its results are presented. The available results are visualised via maps with colourbars.