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Abstract There are instances in remote areas where heat is being wasted, e.g., in internal combustion, engines, etc. Some of this heat can be recovered to produce distilled water in solar stills. The solar still replaces the cooling tower, ponds, or radiators normally used to control the engine temperature. The diesel cooling water in such a system remains separate from the saline water in the solar still. The advantages of using such a system compared with a conventional solar still are: 1. (a) water costs are very much reduced 2. (b) the area occupied is much less, i.e., about 1 5 th 3. (c) production has much less seasonal variation 4. (d) the efficiency of the solar still is improved due to the higher operating temperatures. From experiments conducted at Highett using a Mk VI solar still fitted with a simple heat exchanger and a separate electrically-heated source of hot water to simulate the waste heat, design data are not available for application to working systems. The information required to match a solar still to a diesel's cooling requirement is: 1. (a) engine efficiency 2. (b) hourly fuel consumption 3. (c) hourly solar radiation 4. (d) hourly ambient temperatures. A by-product of this work has been the production of a “solar water heater” which costs less than that of the cheapest conventional system. This “solar” hot water system uses a heat exchanger similar to what is used to transfer the waste heat to the saline water. It is envisaged to have hot water productions approximately the same as the distilled water productions. The influence of hot water production on the output of the waste heat solar still is discussed.

Abstract A linear relation between the efficiency of solar ponds and factor θ d H which is the temperature difference between the pond bottom and the ambient divided by the average insolation is presented. This relation, which has been developed based on a steady state analysis provides valuable information on the relative importance of the parameters involved in the operation of solar ponds. It is found that the existence and the thickness of the top convective zone has a profound negative effect on the yield of solar ponds. The optimum thickness of the density gradient layer under various conditions is also presented. The effect of ground losses is discussed, and it is shown that for the case of wet soil, especially if the level of the underground water is high, the pond should be thermally insulated. It is also shown that the steady state analysis can predict with good accuracy the yearly average response of solar ponds under transient conditions.

The salt gradient solar pond is a long-term heat storage system with a considerable warm-up time. A pond is efficient when it reaches the desired temperature quickly and maximum heat is subsequently retrieved at steady state. This requires optimum sizing of the non-convective zone. In the present work, the optimum size of the non-convective zone for fast warm-up is determined. This is found to differ considerably from the optimum size of the steady state criterion. The possibility of achieving both performance parameters, i.e. fast warm-up and maximum heat collection later on, is analyzed. It is suggested that when commissioning a pond, the size of the non-convective zone should at first be the optimum value from the warm-up rate criterion, but may later be changed to the optimum size from the steady state criterion.

Abstract Finding diverse applications of installed PV based power generating unit is necessary for optimal utilization of energy produced by these units over a period of time. This paper proposes a high gain boost converter that can be used as a DC source for electric vehicle charging application in existing PV based solar pump set-up. The proposed DC-DC converter uses two-stage boosting to achieve a high voltage gain in the form of quadratic quadrupled boost factor. Low turns ratio in coupled inductor reduces the loss components of magnetic part largely. Another advantage of the proposed converter is its operation at lower duty ratio (~0.5) to achieve the desired voltage gain for photovoltaic application. Further, leakage inductance is effectively utilized to achieve ZCS of solid-state devices in conjunction with magnetizing inductance, which provides ZVS for the efficient operation of converter. To analyze the performance of proposed converter for electric vehicle charging application, simulations were carried out using PSIM/MATLAB software and results were validated using experiments conducted on a 250 W hardware prototype developed in the laboratory. A boost factor of 7.8 is achieved at a turn’s ratio of 1.9 for ~35% duty ratio of main switch. The maximum efficiency of ~93% is measured for designed converter.

Abstract This article outlines the minimum set of concepts of hydrological optics required for an understanding of solar energy penetration into bodies of water. The practical application of these concepts to solar ponds, especially by means of the Monte Carlo modeling procedure, is discussed, and an account is given of the optical measurements that need to be made in order to arrive at an understanding of radiation transfer within any given solar pond. The results are presented of a series of Monte Carlo calculations of the behavior of solar radiation within idealized but realistic solar ponds with optical properties covering a wide range of values. The effect on energy collection efficiency of varying the concentration of colored substances, the scattering coefficient, and the albedo of the bottom are explored in detail. The optical criteria that must be satisfied for successful solar pond operation are briefly discussed.

Abstract To operate centrifugal pump against higher discharge pressure and to achieve specific speed for delivering the water, the level of irradiance required is quite high. Therefore, by knowing the operating pressure this problem may be minimized by using energy storage devices like battery or supercapacitor operated in parallel with the SPV module. Here is the need to select a proper configuration of solar PV water pumping system (SPVWPS) using energy storage devices for the economic application. Therefore, a new approach is made towards studying different configurations of 7SPVWPS with battery and supercapacitors under varying discharge pressure and evaluate the performance parameters. Four different configurations of SPVWPS using centrifugal pump are considered, namely, directly coupled, with battery, with the supercapacitors and with a battery-supercapacitor hybrid, to determine the optimum configuration for higher system performance. The experiment have been carried out on a small scale SPVWPS with 2 m and 3 m dynamic head of the pump on sunny days at Haldia, India. The comparison of the performance for the different configurations have been reported. The study reveals that the supercapacitor based configuration give highest instantaneous efficiency. The centrifugal pump powered by SPVWPS using battery delivers a maximum of 2964 L per day for 2 m dynamic head whereas for 3 m dynamic head SPVWPS using supercapacitor delivers a maximum of 1826 L per day. An economic comparison is also done for the different topologies.

Abstract In this study, comparative performance assessment of different passive solar stills systems based on energy matrices, exergy, economic, exergoeconomic, environmental, exergoenvironmental, enviroeconomic, and exergoenviroeconomic viewpoints is performed. Six systems of passive solar stills are considered namely, traditional solar still (TRD still), solar still with phase change materials (PCM), solar still with PCM embedded in a pin fin heat sink (PCM-PF), solar still with PCM incorporated with steel wool fibers in the basin (PCM-SWF), solar still with SWF only in the basin (with SWF) and finally solar still with pin fined heat sink in the basin (with PF). The performance of the six systems is experimentally evaluated and compared to each other under the same meteorological conditions of New Borg El-Arab City, Egypt (Longitude/Latitude: E 029°42′/N 30°55′). The results indicated that PCM-based solar stills systems performed poor performance based on energy matrices, freshwater production cost, exergoeconomic, exergoenvironmental and exergoenviroeconomic parameters. Whereas, solar still with SWF gives the highest performance among all studied systems by employing these enhanced (exergy/economic/environmental) approaches. The daily energy and exergy outputs for conventional still are the minimum at 2.5 and 0.1528 kWh/day, respectively and still with SWF are the maximum at 2.856 and 0.1869 kWh/day, respectively. The annual amount of CO2 emission mitigated for conventional still, still with PCM, still with PCM-PF, still with PCM-SWF, still with SWF and still with PF are 33.02, 35.88, 38.26, 37.05, 41.6 and 38.35 tons, respectively based on energy approach. Whereas, the corresponding values based on exergy are 0.961, 0.6652, 0.6217, 0.756, 1.56 and 1.189 tons, respectively.

Abstract The world which is hot and arid strives for fresh water and thermal comfort, thus there are two basic requirements. In this work, performance of wind tower in combination with solar air heater assisted humidification-dehumidification desalination system working with closed and open air water cycle is analysed numerically for cooling effect and fresh water production. The behaviour of system has been studied by different air flow rate in tower, temperature drop due to energy stored in wall and clay conduits, temperature drop due to evaporative cooling, humidity of moist air available for cooling, amount of potable water produced in dehumidifier and its variation with design and operating variables. A mathematical model based on fluid flow, heat transfer, energy and mass balance in components of system has been developed. Study reveals that comfort condition is achieved mainly by evaporative cooling in wind tower. Optimized column height is found as 8–9 m suitable to design the wind tower with 65% decrease in air velocity, 31% decrease in air temperatures and change in relative humidity up to 90%, however 42% reduction in water requirement in humidifier is also achieved at 5 m height with a cooling effect of 3.5 kW. Air mass flow rate of 0.032–0.035 kg/sec in solar air heater found suitable with maximum productivity of 5 and 4.2 kg/day for closed and open water cycle respectively. Water mass flow rate of 0.035–0.038 kg/sec in dehumidifier has been found suitable for 200% increase in productivity.

Abstract In this paper, an attempt has been made to evaluate and compare the energy matrices of a hybrid photovoltaic thermal (HPVT) water collector under constant collection temperature mode with five different types of PV modules namely c-Si, p-Si, a-Si (thin film), CdTe and CIGS. The analysis is based on overall thermal energy and exergy outputs from HPVT water collector. The temperature dependent electrical efficiency has also been calculated under composite climate of New Delhi, India. It is observed that c-Si PV module is best alternative for production of electrical power. Maximum annual overall thermal energy and exergy is obtained for c-Si PV module. The maximum and minimum EPBT of 1.01 and 0.66 years on energy basis is obtained for c-Si and CIGS respectively, whereas on exergy basis maximum EPBT of 5.72 years is obtained for a-Si and minimum of 3.44 in obtained for CIGS PV module. EPF and LCCE increase with increasing the life time of the system.