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Utilisation of solar ponds in the operation of membrane distillation (MD) could improve the costeffectiveness of water production from inland brackish water sources. Similarly, capacitive deionisation with renewable energy would also provide cost-effective water production. While, solar ponds could help to run either MD alone or MD coupled with reverse osmosis (RO), capacitive de-ionisation will be cheaper to operate when brackish water to be treated. This study discusses details of (i) Optimal footprint of a solar pond for the operation of MD or RO/MD system, and (ii) Appropriate configuration of capacitive de-ionisation system. [ABSTRACT FROM AUTHOR]

In calculating the total solar energy input into a salt gradient solar pond, the current method is insufficient mainly caused by two problems. Firstly, the existing equations of solar pond energy analysis can be only used for momentary calculations but it is very time-consuming for long time periods. Secondly, the shading effect inside the pond affects significantly the energy storage performance of the pond, especially in small ones. To solve the first problem, the mean values of variable parameters during the concerned time period is proposed in this work and the ‘first mean value theorem for definite integrals’ is used to derive the average values. For the second problem, a rectangular pond with vertical walls is investigated as an example, and the exact sunny areas in different depths of the pond are calculated at different time conditions. The experimental data of a published study is used for the validation. The energy efficiency of the low convective zone of the experimental pond is calculated theoretically, which shows a good agreement with the experimental value. The experimental data and theoretical results for the energy efficiency are 9.68% and 11.38% for January, 17.54% and 18.92% for May, and 28.11% and 30.94% for August, respectively. The modified equations can be used to predict a pond performance before its construction. [ABSTRACT FROM AUTHOR]

Salinity-gradient solar pond (SGSP) has been a reliable supply of heat source for power generation when it has been integrated with low temperature thermodynamics cycles like organic Rankine cycle (ORC). Also, thermoelectric generator (TEG) plays a critical role in the production of electricity from renewable energy sources. This paper investigates the potential of thermoelectric generator as a power generation system using heat from SGSP. In this work, thermoelectric generator was used instead of condenser of ORC with the purpose of improving the performance of system. Two new models of SGSP have been presented as: (1) SGSP using TEG in condenser of ORC without heat exchanger and (2) SGSP using TEG in condenser of ORC with heat exchanger. These proposed systems was evaluated through computer simulations. The ambient conditions were collected from beach of Urmia lake in IRAN. Simulation results indicated that, for identical conditions, the model 1 has higher performance than other model 2. For models 1 and 2 in T LCZ = 90 °C, the overall thermal efficiency of the solar pond power plant, were obtained 0.21% and 0.2% more than ORC without TEG, respectively. [ABSTRACT FROM AUTHOR]

Solar pond undoubtedly has been a reliable source of low grade heat supply by acting as both collector and storage for the incoming solar radiation. The thermal efficiency of the solar ponds is between 15 and 25% of the incoming horizontal solar radiation. Meanwhile, the thermoelectric technology enables the conversion of heat into electricity using thermoelectric modules. In this paper, the feasibility of the system by combining solar pond and thermoelectric modules is presented. This system can be achieved by using a thermoelectric modules-embedded heat exchanger module that will able to extract the heat available from the lower convective zone of the solar pond. The analysis in this paper was conducted by investigating the solar ponds operating in different climate conditions, which are Group A (Kuala Lumpur), Group B (Riyadh) and Group C (Melbourne and Granada) base on Köppen climate classification. The theoretical feasibility draws the limit on the performance and cost of the solar pond-thermoelectric system under commercially available thermoelectric technology at the present state. Later, the result was contrasted against the performance of the power generation units operate under realisable operating condition with solar pond. The result in this study revealed that, under ideal condition, the system is at least 10 times costly compared to other renewable energy sources like off-grid solar photovoltaic system with storage. Meanwhile, at its best operating climate, this system will be able to achieve annual carbon dioxide reduction of 2.38 kg/m 2 -year in a practical case. [ABSTRACT FROM AUTHOR]

Brine from seawater desalination plants is deposed to the sea causing a negative impact on the marine life. Solar evaporation ponds are especially suitable to dispose of reject brine from inland desalination plants in arid and semi-arid areas due to the abundance of solar energy. Nearly all forms of salt production require evaporation of water to concentrate brine and ultimately produce salt crystals. In this article research, an experimental shallow solar pond (SSP) having a surface area of 1*1 m2 and depth of 20 cm was built. Solar pond using two reflector mirrors extending for five days from 12 to 16 July 2015 was tested. Mirrors, which are movable for five different angles that makes with horizontal, were used as reflectors in order to increase the thermal energy for the surface of the solar pond during the day. The main factors affecting the evaporation rate which are relative humidity, wind speed, ambient air temperature and solar radiation were studied. The results showed that the little of decreasing evaporation rate was observed by increasing relative humidity and maximum evaporation rate was observed at relative humidity of 67.6%, while slight increasing of evaporation rate was observed by increasing ambient air temperature, evaporation rate appears to decrease slightly as wind speed increases and gradual increasing of evaporation rate with increasing solar radiation. Comparisons between experimental and theoretical results have been performed which good agreement has been achieved. Results showed that evaporation rate increases with decreasing the mirror's angle that makes with horizontal ß. It was concluded that using two mirrors are very effective more than using one mirror when they are used as reflectors and that the best performance of the evaporation can be achieved when the mirrors are employed as reflectors. In conclusion, this system proved to be promising using two mirrors which reduced the solar pond area and hence reduced area needed for brine evaporation in Gaza strip desalination plants. The research can be further developed to achieve better results using large scale solar pond. [ABSTRACT FROM AUTHOR]

The statistics of clear-sky index can be used to determine solar irradiance when the theoretical clear sky irradiance and the cloud cover are known. In this paper, observations of hourly clear-sky index for the years of 2010–2013 at 63 locations in the UK are analysed for over 1 million data hours. The aggregated distribution of clear-sky index is bimodal, with strong contributions from mostly-cloudy and mostly-clear hours, as well as a lower number of intermediate hours. The clear-sky index exhibits a distribution of values for each cloud cover bin, measured in eighths of the sky covered (oktas), and also depends on solar elevation angle. Cloud cover is measured either by a human observer or automatically with a cloud ceilometer. Irradiation (time-integrated irradiance) values corresponding to human observations of “cloudless” skies (0 oktas) tend to agree better with theoretical clear-sky values, which are calculated with a radiative transfer model, than irradiation values corresponding to automated observations of 0 oktas. It is apparent that the cloud ceilometers incorrectly categorise more non-cloudless hours as cloudless than human observers do. This leads to notable differences in the distributions of clear-sky index for each okta class, and between human and automated observations. Two probability density functions—the Burr (type III) for mostly-clear situations, and generalised gamma for mostly-cloudy situations—are suggested as analytical fits for each cloud coverage, observation type, and solar elevation angle bin. For human observations of overcast skies (8 oktas) where solar elevation angle exceeds 10°, there is no significant difference between the observed clear-sky indices and the generalised gamma distribution fits. [ABSTRACT FROM AUTHOR]

Photovoltaic power pattern clustering is fundamental in providing enhanced knowledge on the impacts of integrating photovoltaic systems into the electrical grid without extensive analysis and simulations. This paper investigates a set of clustering algorithms and validity indices to find the most efficient ones in grouping photovoltaic power patterns data. Furthermore, the introduction of the recently-developed bio-inspired optimization method, Bat, with various objective functions in clustering photovoltaic power patterns is presented. In order to evaluate the clustering results in a comprehensive manner, six internal validity indices are employed and a method to determine the optimum number of clusters is introduced. The clustering results on two datasets show that bio-inspired clustering algorithm Bat based on within-cluster-sum-of-squares to between-cluster variation (Bat WCBCR) as an objective function produces significantly high separated and well compact clusters. [ABSTRACT FROM AUTHOR]

The mismatch losses of photovoltaic (PV) systems are mainly caused by partial shading and the largest mismatch losses are caused by sharp shadows. However, in large scale PV plants majority of shading events is caused by moving clouds which lead to gentle irradiance transitions causing typically only minor irradiance differences between adjacent PV modules. Irradiance transitions caused by the edges of cloud shadows have an average length of almost 150 m meaning that even the largest PV power plants are widely affected by them. In addition of mismatch losses, these irradiance transitions can lead to failures in maximum power point tracking and cause significant fluctuations in the output power of PV systems. In this paper, the effects of PV array shape, electrical configuration and orientation on mismatch losses caused by moving clouds were studied based on apparent velocity and other measured characteristics of roughly 27,000 irradiance transitions. The study was conducted using a mathematical model and parametrisation method of irradiance transitions and an experimentally verified simulation model of a PV module based on the well-known one-diode model of a PV cell. The studied electrical PV array configurations were series-parallel, total-cross-tied and multi-string. The results of this study confirmed a prior conclusion, namely, that the mismatch losses decrease with decreasing PV string length. It was also found that the array orientation has a considerable effect on the mismatch losses of the studied array layouts. The mismatch losses were the smallest when the dominant direction of movement of the shadow edges was perpendicular to the PV strings. The differences in the mismatch losses between the studied electrical array configurations were very small. The results indicated that the mismatch losses caused by moving clouds have only a minor effect on the overall efficiency of PV arrays. [ABSTRACT FROM AUTHOR]

Thermochemical energy storage (TCES) systems utilize reversible reactions to store solar energy in chemical form. The present work focuses on the cobalt/cobaltous oxide (Co 3 O 4 /CoO pair) based redox cycle in which the active oxide is coated on a cordierite honeycomb structure. During the redox cycle, cobalt oxide uptakes and releases oxygen from/to an air stream coming in direct contact with it. Thus air acts as a reaction medium as well as a heat transfer fluid (HTF). In this configuration, the storage material works as a heat storage medium and also a heat exchanger. A two-dimensional, axisymmetric numerical model to simulate the heat and mass transfer and the chemical reaction in the thermochemical heat storage reactor has been developed. Experimental results from a 74 kW h th -capacity prototype reactor installed at the Solar Tower Jülich test facility, Germany, were used to validate the numerical model. The time-dependent boundary conditions in the form of inlet temperature and inlet mass flow rate from the experiments were employed in the numerical model. The temperatures of the redox material at different locations inside the prototype thermochemical storage/heat exchanger reactor were used for the numerical model validation. Total energy stored/released (sensible as well as chemical) during the experiments was also compared with the numerical model results. From this study, it is concluded that the numerical model can accurately predict charging/discharging processes for the cobalt oxide based thermochemical storage reactor system for multiple redox looping cycles. The model allows a better understanding of the complete process and helps to identify the effect of variation of boundary conditions on the system. [ABSTRACT FROM AUTHOR]

This brief note addresses the method of adding heat to a solar pond from an external source which is used to enhance the performance of a solar pond. Heat energy collected by Evacuated Tube Solar Collectors (ETSC) is transferred by circulating fluid from the Lower Convective Zone (LCZ) of a solar pond. While adding the heat, a strange phenomenon is observed here which is against the intuition that higher the amount of heat added to the pond higher will be the temperature of the pond always. It is noticed that in the case of no or low heat extraction from the pond the heat is actually lost from the pond to the circulating heat adding fluid in specific periods of time which causes a drastic downfall of solar pond temperature. Moreover, it is observed that larger the capture area of the ETSC, larger is the heat loss from the pond. A strategy to control the heat loss from the solar pond by installing temperature sensors and flow controller in LCZ and the circulating fluid exiting ETSC is discussed here. [ABSTRACT FROM AUTHOR]

To address the intermittency in solar energy system due to unforeseen weather conditions and to improve dispachability, the requirement of Thermal Energy Storage (TES) system is becoming increasingly inevitable. A single tank packed bed thermocline TES system has potential to provide an effective solution. A comprehensive one-dimensional non-thermal equilibrium model is considered and is solved using method of characteristics to investigate energy storage in a single tank packed bed thermocline storage system. Thermal characteristics including temperature profiles and discharge effectiveness with different commercially available Heat Transfer Fluids (HTFs) are explored and analyzed. A tank size of 12.5 m in height and 8 m in diameter is considered with a capacity of 40 MW h t for the present study. The effect of porosity on discharge effectiveness of the storage tank with different HTFs is investigated with porosity, ε varied from 0.1 to 0.7. It is found that the discharge effectiveness consistently drops when ε value increases from 0.1 to 0.7 for all the HTFs. Two-dimensional numerical simulation is also carried out to explore the transient temperature distribution inside the tank for different HTFs with a porosity of 0.2. It is observed that as the operation time of the tank increases, filler material eventually loses heat to adjacent fluid and attains equilibrium. The thermocline moves at a faster rate in Solar Salt than the HITEC due to its higher viscosity. [ABSTRACT FROM AUTHOR]

Thermal energy storage for solar dryer has recently attracted increasing interest as the availability of solar energy is intermittent. The effectiveness of thermal energy storage using Phase Change Material (PCM) in solar dryer application was investigated in this work. A solar cabinet dryer having 3 evenly spaced trays that provide maximum heat flow with drying area of 0.5 m2 (each) that caters to a family was constructed and its performance evaluated. The experiments were done on the dryer with and without thermal storage for 3 days each during the month of April when the sunshine remains considerable in Annamalai Nagar located at 11.39° N Latitude and 79.69° E Longitude. The temperature at different vital locations was recorded from 10 a.m. onwards until the cabinet temperature fell to that of the atmosphere. The mass flow rate of air during experimentation varied between 0.001- 0.003 kg/s. A paraffin (n-docosane)-kerosene composite of 12.5 kg and 2:1 mass ratio was used for thermal storage in the dryer. The PCM was filled in 20 numbers of 20 mm diameter aluminum tubes having 500 mm length and 100 aluminum cans of 150 ml capacity (excluding space for phase change). The results were analysed for the variation of thermal absorption and storage based on air velocity, temperature gradient, and solar intensity. The cabinet temperature remained 25-30°C higher than that of atmosphere during mid-day. The peak heat gain fell by 18% on the days of experimentation with thermal storage due to the heat conducted by PCM pipes. On an average, the thermal efficiency of the system with thermal storage improves by 50 % of its efficiency without thermal storage unit. It was found that the dryer with thermal storage can sustain the required temperature for 3 hours after sunshine hours and then it falls gradually [ABSTRACT FROM AUTHOR]

Aquifers are underground porous formations containing water. Confined aquifers are surrounded by impermeable layers on top and bottom, called cap rocks and bed rocks. A confined aquifer with a very low groundwater flow velocity was considered to meet the annual cooling and heating energy requirements of a residential building complex in Tehran, Iran. Three different alternatives of Aquifer Thermal Energy Storage (ATES) were employed to meet the heating/cooling demands of the buildings. These alternatives were using ATES for: cooling alone, heating alone by coupling with at-plate solar collectors, and cooling and heating by coupling with a heat pump. For the economic evaluation of the alternatives, a life cycle cost analysis was employed. For the environmental evaluation, Ret Screen software was employed. For the considered 3 operational alternatives, using ATES for cooling alone had the minimum payback period time of 2.41 years and the life cycle cost of 16000 $. In the environmental perspective, among the 3 alternatives, coupling of ATES with heat pump for cooling and heating had the minimum CO2 generation, corresponding to 359 tons/year. [ABSTRACT FROM AUTHOR]

In this paper, a Dish-Stirling Concentrating Solar Power (CSP) system was examined in which the engine works no longer as a receiver but is displaced away from it. In this arrangement it is necessary to adopt a heat transfer fluid capable of transmitting the useful power from the receiver to the hot spring in the Stirling engine head. Various components of the system need designing and especially the heat exchanger in charge of transferring power to the engine head thanks to the cooling of the fluid. The Dish-Stirling system under study includes a linear piston Stirling engine of 4 kW total rated power (3 kW thermal and 1 kW electric). The minimum temperature for starting of the engine is 190 °C, while the maximum is 565 °C. There are many innovative aspects of dish Concentrating Solar Power systems with Stirling engine dislocated, for example, the possibility of using an increased number of engines powered by a single greater dish and energy savings in the solar tracking system. The work covers the search for the most suitable fluids for the purpose, risks and benefit evaluation of fluids never used previously in the field of solar concentration. The heat exchanger sizing was carried out examining different geometric configurations. The study was conducted using a computer and setting up thermo-fluid dynamics simulations in the ANSYS 14.5 environment. Finally, the results were tested and validated through a comparison study with empirical correlations found in the literature. [ABSTRACT FROM AUTHOR]

The problem associated with the reverse osmosis (RO) system is its brine disposal. Experimental salinity gradient solar pond (SGSP) with surface area 4.65 m 2 was established to extract and apply heat on laboratory scale direct contact membrane distillation (DCMD). In this study, the performance of the SGSP and DCMD system under Pakistan’s climatic condition of Islamabad was evaluated. The heat extraction was carried out using internal heat exchanger by passing fresh water through it at different flow rates in summer and winter. Maximum temperature of 37 °C in summer and 28.5 °C in winter was extracted. The extracted heat from SGSP can be used to pre-heat the brine for temperature driven desalination processes. Least drop in lower convective zone (LCZ) temperature of SGSP was observed at flow rate of 7.5 L/min. In DCMD, two temperatures obtained from SGSP (28.5 and 37 °C) at feed side were maintained to investigate the permeate flux, percentage salt rejection and total dissolve solids (TDS). Two further temperatures 50 and 60 °C were maintained to investigate the DCMD performance. Flux increased as temperature difference between feed and permeate increased. 28.5 °C in terms of SGSP temperature was also feasible for DCMD process as flux was maintained over time. [ABSTRACT FROM AUTHOR]

In this study, an integrated model system which is consisted of a solar pond, flat-plate collectors and an organic Rankine cycle (ORC) was designed to determine not only thermal and electricity but also hydrogen generation performances. The flat-plate collectors assisted by a solar pond to enhanced the thermal performance of the system in order to generate electrical energy with ORC. In addition, mass, enthalpy, entropy, energy and exergy balance equations of the system was solved by using a software which is called Engineering Equation Solver (EES). Thus, the thermodynamic analysis of the system were done. As a result, a significant amount of electrical energy is produced by using ORC which works with the thermal energy comes from the integrated system. Thus, this system can reach up to a hydrogen production rate of 2.25 kg/day by the water electrolysis system. The results show that hydrogen production performance increased by increasing the performance of the thermal system. Thus, the performance of a solar pond is an important effects at the performance of the integrated system. We believe that the theoretical results obtained in this work are very useful for making realistic and accurate predictions about the pre-planned integrated systems to produce the hydrogen energy. [ABSTRACT FROM AUTHOR]

In this article, a transient modeling method for the heat extraction process in the rectangular solar ponds is presented by using a finite difference technique. Firstly, the thermal behavior of the pond, during the heat extraction operation is modeled. Then the model is verified using experimental data, and the maximum observed percentage error of this method is 2.03%. This method is used to model the heat extraction from a hypothetical pond in Tehran for three months of August, September, and November. The results present the temperature profiles, the extracted heat and the rate of heat extraction. All of these parameters have the highest value in August, and the lowest values are allocated to November. Moreover, the percentages of the extracted heat during the operation are studied. For all the three months, this parameter has a high value in the first 40% of the time needed to full heat extraction. Between the 40% and 70% of the total time, the heat extraction rate reduces drastically, and after the 70% of the total time, it is almost constant at a low value. Also, the modeling results are used in a low-temperature organic Rankine cycle, and it is found that for the designed pond, the pond can be used as the heat source of the cycle only in August and for 7.31 h of operation. [ABSTRACT FROM AUTHOR]

Salt-gradient solar ponds are water bodies that act as solar collectors with integrated storage that are a promising renewable energy source for low-temperature applications. Evaporation is an important challenge for efficient operation of solar ponds, especially in arid locations without water sources to replenish the evaporative losses. In this work, transparent partial covers were used to investigate how evaporation suppression affects both the water and energy balance of a laboratory-scale solar pond. In our experiments, the evaporation reduction efficiency was related to the cube root of the relative covered area. This evaporation reduction efficiency is smaller than that of natural water bodies because of the influence of the warm lower convective zone. Also, as the covered fraction of the surface area increased, the thickness of the non-convective zone decreased and the heat losses through this zone increased. As a result, the temperature in the lower convective zone did not increase as the covered fraction increased. Nonetheless, the heat content within the solar pond slightly increased, demonstrating that the reduction of evaporation improves the heat storage capacity of the pond. Moreover, an economic analysis showed that although the evaporation reduction efficiency in solar ponds is smaller than that of natural water bodies or reservoirs, the benefits related to the additional energy collected in the solar pond when reducing evaporation overcome the smaller water saving benefits. Therefore, suppressing evaporation in solar ponds not only is valuable in locations with no water to replenish the evaporative losses but also improves its economic benefits. [ABSTRACT FROM AUTHOR]

Solar ponds are low cost pools of brine solutions with integrated storage zones that harvest incident solar energy and store it as thermal energy. The current study examined the performance of a salinity gradient solar pond under the Mediterranean climatic condition for ten consecutive months of operation, from October 8, 2014 to July 31, 2015. The presented results are based on the experimental data of a small-scale circular pond, 61 cm in diameter a height of 55 cm, constructed and operated at Middle East Technical University, Northern Cyprus Campus (METUNCC). The study showed the necessity of regular surface washing and having excess undissolved salt at the lower convective zone (LCZ) to maintain the pond stability. The variations in the temperature of the non-convective (NCZ) and lower convective zones (LCZ) are found to be a function of both ambient temperature and solar irradiation (insolation). The variation of the overall pond’s temperature strongly follows the changes in ambient temperature while solar insolation directly affects the increase in temperature gradient by depth. During the period of this study, the pond reached the highest average temperature of 48 °C in July 2015 while the average ambient temperature for this month was 30 °C. [ABSTRACT FROM AUTHOR]

In this study, a composite electrospun nanofiber membrane was fabricated and used to treat a geothermal brine source with lithium enrichment. An in-situ growth technique was applied to incorporate silica nanoparticles on the surface of nanofibers with (3-Aminopropyl) triethoxysilane as the nucleation site. The fabricated composite nanofiber membrane was heat pressed to enhance the integration of the membrane and its mechanical stability. The fabricated membranes were tested to evaluate their performance in feedwater containing different concentrations of NaCl in the range of 0–100 g/L, and the wetting resistivity of the membranes was examined. Finally, the optimal membrane was applied to treat the simulated geothermal brine. The experimental results revealed that the in-situ growth of nanoparticles and coating of flourosilane agent dramatically improved the separation performance of the membrane with high salt rejection, and adequate flux was achieved. The heat-pressed membrane obtained >99% salt rejection and flux of 14–19 L/m2h at varying feedwater salinity (0–100 g/L), and the concentration of the Li during the 24 h test reached >1100 ppm from the initial 360 ppm. Evaluation of the energy efficiency of the membranes showed that the heat-pressed membrane obtained the optimum energy efficiency in the high concentration of salts. Additionally, the economic analysis indicated that MD could achieve a levelized cost of 2.9 USD/m3 of lithium brine concentration as the heat source is within the feed. Overall, this technology would represent a viable alternative to the solar pond to concentrate Li brine, enabling a compact, efficient, and continuous operating system. [Display omitted] • A novel omniphobic electrospun membrane was prepared by chemical modification. • The omniphobicity was enhanced by in situ growth of nanoparticles. • The membrane was applied for lithium enrichment from geothermal brine. • The concentration of lithium exceeds 1100 ppm after treatment by MD. • Economic evaluation was performed to analyze the efficiency of the MD system. [ABSTRACT FROM AUTHOR]

Winter propagation of black swans Cygnus atratus is introduced at Kwangpho on the east coast of the Democratic People's Republic of Korea located in the temperate zone of northeast Asia. The natural lake Kwangpho was selected as a rearing site to provide the environment which matched most closely to black swan's natural habitats. Comparison of the climate data of Kwangpho with Australia and New Zealand led to the conclusion that it is necessary to increase winter temperature 10 °C for artificial rearing. In order to overcome the low temperature with renewable energy, a passive solar greenhouse with a water pond was introduced, where black swans were reared simultaneously while observing the microclimate such as air temperature, humidity and water temperature in winter. When the pond depth was 0.4 m and 0.8 m, there was no significant difference in indoor temperature, the depth fixed at 0.4 m to reduce pumping power by more than 50%. During the study, 80 mature black swans wintered safely and 13 pairs of them laid 74 eggs, the artificial hatching rate was 65% and the natural hatching rate was 53%. It was confirmed that the passive solar greenhouse with a pond can raise the winter minimum temperature 8–10 °C higher than outside, and in this microclimate it is possible to propagate the black swan and it is believed that the greenhouse has abundant potential to enable the artificial breeding as well as wintering of black swans, in temperate zone occupying wide area of the earth. • Winter propagation of black swan is feasible in a solar greenhouse. • In the greenhouse environment the temperature rises 8–10 ℃ higher than outdoor. • The proper pond water depth is 0.4 m. • Natural hatching rate is higher in summer, lower in winter than artificial one. [ABSTRACT FROM AUTHOR]

Solar ponds have been widely utilised in providing low grade heat needed for industrial processes and for heating applications <100 °C. In this paper, a small scale passive electric power generation unit was devised for generating electricity from the heat available in the solar pond. The power generation unit proposed operates without the use of a pump and involves no moving parts. The design of the power generation unit was finalised after performing a comprehensive theoretical study on the possible geometrical arrangements. The power generation unit was fabricated and tested experimentally. The power generation unit consists of 120 commercially available thermoelectric cells accommodated in the outer and inner layers of this dual layer power generation unit. The power generation unit had produced a maximum power of 40.8 W under the condition of T h = 99 °C. Under the normal operation of solar pond, the lower convective zone will have a temperature that lies within in the range of 40 °C –80 °C. Thus, maximum output in the range of 19.5 W–27.4 W is more realistic for the system proposed with the heat to electric conversion efficiency ranges between 0.37%–0.68%. [ABSTRACT FROM AUTHOR]

Thermophilic anaerobic digestion (AD) is an efficient treatment process for waste activated sludge with enhanced hydrolysis and digestion rates. However, the costs associated with maintaining high temperature for thermophilic digester should be minimized and the thermal stability of the reactor should be maximized for its practical use. This study tested an integrated system consisting of a solar pond and an AD reactor for digestion of waste activated sludge. The integrated system could be stably operated at 51.6 ± 1.5 °C in sunny days (and nights) and maintained digestion performance over at least three days with cloud and rain. On the contrary, the control reactor without solar pond experienced significant temperature fluctuation and poor digestion performance. After 29d, the integrated system thermophilic reactor removed 65.0 ± 4.2% of total chemical oxygen demands and produced 79% excess biogas. The concentrations of soluble chemical oxygen demand, protein and saccharides in digester with solar pond were higher than those in that without the pond. Also, the presence of solar pond enhanced hydrolysis and degradation of soluble microbial byproduct-like compounds with carboxylic groups and amide-2 groups in sludge. [ABSTRACT FROM AUTHOR]

Solar pond (SP) has been a reliable supply of heat source for heating process that requires temperature <100 °C. In this work, the capability of solar pond in generating electricity has been explored experimentally using a plate type power generation unit (PTPGU). The open channel PTPGU was designed and fabricated in order to accommodate the TECs. The heat stored in the lower convective zone (LCZ) is used as the heat source needed for generating electricity by utilising thermoelectric cells (TECs) and thus a combined SP-PTPGU system is proposed. The PTPGU was tested with different hot water temperatures and flow rates. Also, the possibility of performance enhancement utilising copper mesh as insertion is presented. From the testing conducted, the PTPGU is able to generate 35.9 W of electricity at the flow rate as low as 5.1 LPM (litre per minute) at the hot water temperature of 81 °C. Besides coupling with solar pond, the PTPGU designed can also be coupled with other type of hot water source, such as hot spring. [ABSTRACT FROM AUTHOR]

The thermal performance of a shallow solar pond with and without the single transparent glass cover has been investigated experimentally. This experiment has been performed during the summer season of 2014 under the operational condition for five different storage volumes of water upto a maximum of 10 liter. The pond performance is investigated in terms of the rate of energy collected and its collection efficiency. A Low Density Polyethylene (LDPE) black sheet liner of 200 μm thickness was laid on all the interior sides of the pond for solar energy absorption. A clear transparent PVC plastic sheet of 150 μm thickness was laid over the water surface as evaporation suppressing membrane. Calibrated Copper constantan thermocouples were used to measure the temperatures of the system. A highest temperature of 81.5 °C has been achieved for the stored volume of 2 liter of water, when the pond was used with a single transparent glass cover of 5 mm thickness. When the shallow solar pond was used without the transparent glass cover the system attained a maximum temperature of 62 °C for the same stored volume of 2 liter. A comparison between the two conditions of with and without the transparent glass cover, on the thermal performance of the SSP has been reported. A shallow solar pond system of the present type could be used us a source of warm water, of desired temperature, below 10 °C which are required for the domestic and industrial utilities. The global warming is increased day by day; inorder to reduce global warming a typical method of small scale shallow solar pond has been used to absorb the radiation from the sun to convert it to useful heat energy by the source of water. The SSP is an eco friendly way to generate energy without polluting our environment and in an environment safety manner. Based on environmental safety this study has experimentally investigated the thermal performance of the shallow solar pond. [ABSTRACT FROM AUTHOR]

Salinity gradient solar ponds can be used to store heat by trapping solar radiation. The heat can then be employed to drive various industrial applications that require low-grade heat. In this study, a comprehensive finite difference transient model has been developed incorporating many processes that affect the performance of a solar pond to predict the hourly temperature distribution. The model includes novel approaches to simulation of both the Heat Storage Zone (HSZ) and the Upper Convective Zone (UCZ) where in addition to convective, evaporative and radiative heat losses, the cooling effect of adding freshwater to the surface of the pond is taken into account. The HSZ is treated as one layer, with uniform temperature, in the finite difference method. A solar pond of 100 m 2 surface area is simulated for southern Turkey. The results indicate that, if the operation starts on the first day of June, the HSZ would take 65 days to reach the boiling point while this would be 82 days if the operation commences on the first day of December. The simulations highlight that 41–47 l of freshwater will need to be supplied to the UCZ daily and the associated cooling effect of such addition is approximately 10 times larger than the convective heat loss in the first 65 days of operation. In addition, as 22.4% of the incoming radiation in the form of long wavelength radiation, is absorbed within the top 1 cm of the pond, there is a sharp increase in the temperature of the UCZ creating a hot-zone which slowly moves downwards to the Non-Convective Zone (NCZ) and eventually the HSZ. Hence, the HSZ does not initially prevail as the hottest zone in the pond. However, as the temperature rises and the pond approaches pseudo-steady state, the hot-zone slowly moves downwards and finally reaches the HSZ. This phenomenon is consistent with experimental studies and proves the imprecision of pseudo-steady state models. Furthermore, the HSZ becomes more resistant to losing the accumulated heat to the layers above as its temperature increases due to the better establishment of the NCZ as the insulator for the HSZ. [ABSTRACT FROM AUTHOR]

The main purpose of this study is to develop a sustainable zero liquid discharge desalination system. Direct contact membrane distillation unit is connected directly to salinity gradient solar pond (SGSP) to achieve zero liquid discharge desalination. The used system contains a hydrophobic microporous membrane module and a plastic pipe circulating all over the pond water surface to be used as a cooling system. The pipe also used as a wave suppression system as it is floating over the top of the pond water surface. The system is sourced by the hot and high concentrated saline water that is extracted from non-convective zone as a feed solution, then, the brine discharges at the lower convective zone of the solar pond. Therefore, if the saturated brine is used to produce salts, there will not be any brine left over which may lead to zero liquid discharge desalination. The system is modelled theoretically and solved by Matlab simulation program. It has been found that the system has the ability to deliver 52 l/day of fresh water for m 2 of membrane coupled with SGSP, consuming almost 11 kW/m 2 of thermal energy. Also, the trans-membrane coefficient of the used membrane is proved to be 0.001 kg/m 2 /Pa/h. The results are analysed and the system performance is evaluated and presented in this paper. [ABSTRACT FROM AUTHOR]

The increasing importance of a significant reduction of CO2 emissions in the atmosphere asks the scientific community to find other solutions than fossil fuels with respect to the air conditioning of indoor environments. Nowadays, a priority is represented by the energy expenses reduction, in which residential buildings report one of the highest energy consumption levels among developed countries. The application of alternative energies in residential buildings is an issue debated in the European Commission for the reduction of greenhouse gas emissions with the objective to obtain 20% of the demand from renewable sources. This paper suggests the application of the solar energy stored in solar ponds to air-condition small residential buildings, through the use of absorption machines. A feasibility analysis was carried out in some places characterized by climates that are suitable to make the solution here suggested sustainable from an energetic point of view. Buildings characterized by different boundary surface/volume ratios were examined and the energy saving, the amount of CO2 that was not emitted in the environment and the return of investments with respect to a more traditional solution were evaluated. [ABSTRACT FROM AUTHOR]

• LBM simulation of thermosolutal convection in a SGSP enclosure with porous layer. • Cross-diffusive effects on thermosolutal convection in this SGSP enclosure are analyzed. • Attaching a porous layer at the bottom inhibits the thermal and solutal transfer processes. • Du enhances both thermal and solutal transfer processes, while Sr boosts the solutal one. • Internal heat generation reduces the positive influence of Soret and Dufour effect. Salt gradient solar pond (SGSP) is a promising alternative for low-temperature industrial applications. Thermal and solutal transfer processes occur simultaneously at SGSP, which induce the cross-diffusive effects and make the internal flow more complicated. In the present work, thermosolutal convection under cross-diffusive effects inside a simplified SGSP enclosure attached with a porous layer are investigated through Lattice Boltzmann Method (LBM). Influences of internal heat generation, buoyancy ratio, thickness and permeability of porous layer combined with Soret and Dufour parameters are considered on the thermal and solutal transport characteristics. Average Nusselt and Sherwood numbers as well as mean temperature and concentration are presented to analyze the thermal and solutal transport processes in the SGSP enclosure. Results indicate that Soret effect mainly boosts the solutal transport process, while Dufour effect can greatly enhance both the thermal and solutal transport processes. Internal heat generation can inhibit the thermal and solutal transport processes and reduce the positive influence of Soret and Dufour effect. Buoyancy ratio can boost thermal and solutal transport processes. In the opposing situations (N < 0), Soret effect weakens the thermal transport process, while Dufour effect is reverse. Furthermore, attaching a porous layer at the bottom wall can suppress the thermal and solutal transfer processes, and then increases the thermal storage capacity. Permeability and thickness of porous layer have a significant influence on thermal and solutal transport processes. Present study is beneficial to the thermal storage enhancement and the future development of SGSP. [Display omitted] [ABSTRACT FROM AUTHOR]

The common process in all applications of a salinity-gradient solar pond (SGSP) is the energy extraction process using single-phase mode heat transfer with some limitations such as pumping the large amount of mass flow rate, and need for big size of heat exchanger. In every respect, two-phase mode heat transfer can be selected as an advantage due to its passive case of operation and comparatively high heat transfer capacity with rational system size. In this paper, an enhanced design of a large scale SGSP power plant using some two-phase closed thermosyphons has been simulated and compared with the single-phase mode heat transfer. The simulation results showed that the overall thermal efficiency of the solar pond power plant was the highest using both thermosyphons and heat exchangers. [ABSTRACT FROM AUTHOR]

In this study, heat extraction from both the gradient and heat storage zones of a salinity-gradient solar pond (SGSP) has been evaluated. For this purpose, an experimental solar pond pilot plant was constructed in 2009 in Barcelona (Spain). The structure of the pond is a cylindrical tank of 3-m height and 8 m diameter with a total area of 50 m 2 . The main objective was to evaluate a heat-extraction system from the SGSP designed to enhance the system efficiency under different conditions. Thus, an in-pond heat exchanger covering all of the lateral wall area of the pond was installed, and its performance was compared with the traditional in-pond heat exchanger situated on the bottom of the pond. Heat extraction experiments were performed using both heat exchangers individually or both at the same time. The study covers the experiments performed at three different seasonal temperature conditions: winter (December), summer (July) and autumn (October and November). The variations of the temperature inside the pond during the heat extraction were measured and analyzed. The results demonstrated that the efficiency of the pond increases when the heat is removed from the lateral heat exchanger alone compared to either using the bottom heat exchanger or using both heat exchangers simultaneously. [ABSTRACT FROM AUTHOR]

Salt-gradient solar ponds (SGSPs) are water bodies that capture and accumulate large amounts of solar energy. The design of an SGSP field has never been analyzed in terms of studying the optimal number of solar ponds that must be built to maximize the useful energy that can be collected in the field, or the most convenient way to connect the ponds. In this paper, we use constructal design to find the optimal configuration of an SGSP field. A steady-state thermal model was constructed to estimate the energy collected by each SGSP, and then a complementary model was developed to determine the final temperature of a defined mass flow rate of a fluid that will be heated by heat exchangers connected to the solar ponds. By applying constructal design, four configurations for the SGSP field, with different surface area distribution, were evaluated: series, parallel, mixed series-parallel and tree-shaped configurations. For the study site of this investigation, it was found that the optimal SGSP field consists of 30 solar ponds of increasing surface area connected in series. This SGSP field increases the final temperature of the fluid to be heated in 22.9%, compared to that obtained in a single SGSP. The results of this study show that is possible to use constructal theory to further optimize the heat transfer of an SGSP field. Experimental results of these configurations would be useful in future works to validate the methodology proposed in this study. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Although the costs of desalination have declined, traditional desalination systems still need large amounts of energy. Recent advances in direct contact membrane distillation can take advantage of low-quality renewable heat to desalinate brackish water, seawater, or wastewater. In this work, the performance of a direct contact membrane distillation (DCMD) system driven by salt-gradient solar ponds was investigated. A mathematical model that couples both systems was constructed and validated with experimental data available in the scientific literature. Using the validated model, the performance of this coupled system in different geographical locations and under different operational conditions was studied. Our results show that even when this coupled system can be used to meet the future needs of energy and water use in a sustainable way, it is suitable for locations between 40°N and 40°S that are near the ocean as these zones have enough solar radiation, and availability of excess water and salts to operate the coupled system. The maximum freshwater flow rates that can be obtained are on the order of 3.0 L d per m of solar pond (12.1 m d acre), but the expected freshwater production values are more likely to be on the order of 2.5 L d per m of solar pond (10.1 m d acre) when the system operates with imperfections. The coupled system has a thermal energy consumption of 880 ± 60 kWh per m of distillate, which is in the range of other membrane distillation systems. Different operational conditions were evaluated. The most important operating parameters that influence the freshwater production rates are the partial pressure of air entrapped in the membrane pores and the overall thermal efficiency of the coupled system. This work provides a guide for geographical zone selection and operation of a membrane distillation production system driven by solar ponds that can help mitigate the stress on the water-energy nexus. [ABSTRACT FROM AUTHOR]

This paper describes the authors’ experience of constructing a 113 m 2 solar pond at Umm Al-Qura University, Saudi Arabia. The work demonstrates the technical viability of solar pond technology in the Middle East. A sustainable system for heat extraction from the experimental pond was designed and implemented. A new scheme for the measurement of temperature throughout the pond was also introduced for the purpose of further enhancing performance. The aim of this research is to develop an operational protocol which achieves high levels of thermal and mechanical efficiency and within which salt is conserved by first concentrating the surface discharge of saline in an evaporation pond followed by its re-circulation to the base of the pond via a salt charger. [ABSTRACT FROM AUTHOR]

Liquid desiccant cooling systems (LDCS) are energy efficient means of providing cooling, especially when powered by low-grade thermal sources. In this paper, the underlying principles of operation of desiccant cooling systems are examined, and the main components (dehumidifier, evaporative cooler and regenerator) of the LDCS are reviewed. The evaporative cooler can take the form of direct, indirect or semi-indirect. Relative to the direct type, the indirect type is generally less effective. Nonetheless, a certain variant of the indirect type – namely dew-point evaporative cooler – is found to be the most effective amongst all. The dehumidifier and the regenerator can be of the same type of equipment: packed tower and falling film are popular choices, especially when fitted with an internal heat exchanger. The energy requirement of the regenerator can be supplied from solar thermal collectors, of which a solar pond is an interesting option especially when a large scale or storage capability is desired. [ABSTRACT FROM AUTHOR]

Solar pond has been a reliable supply of heat source for industrial process that requires heat at the temperature <100 °C. In this paper, the prospect of solar pond in generating electricity has been explored with the aid of using TEGs (thermoelectric generators) for converting the heat available at LCZ (lower convective zone) into electricity. By using the transient heat transfer model developed and the testing result of a thermoelectric module, this study has covered the potential of generating electricity for the solar pond operates in the climate of Group A, B, and C under Köppen climate classification. The effect of heat extraction, climatic variation, temperature polarisation, and the conversion efficiency of TEG on the thermal performance and electrical performance of the system has been discussed. The solar pond operates in Riyadh (Group B of Köppen climate classification) possesses the highest potential in generating electricity, which is about 4.834 kWh/year-m 2 at heat extraction of 15% of year average horizontal solar radiation (i.e. solar pond yearly efficiency of 15%) while having average LCZ temperature of 80 °C throughout the year. Overall, the thermal-electrical conversion efficiency, η t of this system is in the range of 1%–1.5% from the heat extracted. [ABSTRACT FROM AUTHOR]

Solar energy has a promising future as one of the most important types of renewable energy. Solar ponds can be an effective way of capturing and storing this energy. A new theoretical model for a heat transfer in a salinity gradient solar pond has been developed. The model is based on the energy balance for each zone of the pond; three separate zones have been considered, namely the upper convective zone, the lower convective zones, as well as the non-convective zone. The upper and lower zones are considered to be well mixed, which means the temperatures in these zones are uniform. The model shows that the temperature in the storage zone can reach more than 90 °C during the summer season whereas it can be more than 50 °C in winter if the pond is located in the Middle East. In addition, the time dependent temperature for the three layers has been found. Furthermore, it is concluded that heat loss from the pond’s surface occurs mainly by evaporation, in comparison to convection and radiation. Heat loss to the ground has been calculated by using three different equations. It was found that the perimeter of the pond has a significant effect on heat loss to the ground from a small pond, while its effect is small in the case of large pond. The validity of the model is tested against experimental data for several established ponds; good agreement is observed. [ABSTRACT FROM AUTHOR]

The subject of this study is the seawater distillation process enhancement through integration of the solar vacuum tube into the system. Positive effects on the rate of distillated freshwater achieved by means of the enhanced system have been investigated experimentally. Experiments were done in the Turkish city of Samsun in the Black Sea region. A distillation pond setup having the volume of 0.015m3 and a water surface area of 0.24m2 was constructed. The distillation pond is covered with a condensation glass and also equipped with a 0.15m solar vacuum tube that is inclined at an angle of 30° to the ground, a feed water tank connected with a ball cock, and distillated fresh water tank. Experimental results have shown that the rate of distilled fresh water was enhanced for about 62.5% by integrating the solar vacuum tube and the natural distillation pond. Isolation of the condensation glass not only prevents the light transmission to the pond but also heat loss from the pond; hence the rate of the distillated fresh water is increased for about 137.5% due to the natural distillation. [ABSTRACT FROM AUTHOR]

Geothermal energy pile foundations are sustainable, cost-effective alternative energy systems for heating and cooling needs of buildings. This paper presents the thermal modeling of two different configurations of energy pile foundations used for seasonal energy storage. Several two-dimensional (2D) transient analyses were carried out to find the optimum pile configuration and to obtain preliminary information about the heat exchange between the ground and the building. Two scenarios were modeled. In Scenario 1, a combination of long and short piles was simulated, while in Scenario 2 only long piles were considered. Long piles are structural piles and work as a heat exchanger throughout the year, while the nonstructural short piles operate only in the summer months to inject surplus solar energy into the ground. Simulation results show that in Scenario 1 the vertical temperature distribution was uneven, resulted in high temperatures at shallow depths (0-10 m) and near-freezing temperatures at greater depths. In contrast, Scenario 2 yielded a more uniform temperature distribution throughout the depth. More importantly, in Scenario 2, the temperature inside the storage system was maintained well above the freezing temperature. [ABSTRACT FROM AUTHOR]

Parsimonious constitutive expressions with good accuracy are developed for the fundamental thermodynamic and mechanical properties of aqueous sodium chloride in the ranges of temperatures and salinities arising in the operation of a salt-gradient solar pond. Specifically expressions for density, thermal conductivity and diffusivity, solubility, boiling point, specific heat and enthalpy at atmospheric pressure, dynamic viscosity and vapor pressure are expressed as functions of Celsius temperature and salinity (particle concentration) in kg/m 3 by contrast with the commonly used measures of molality or weight fraction. The constitutive expressions are constructed from data drawn from specialist articles spread around the literature and are parsimonious in the respect that at most floor(log(N)) adjustable parameters are allowed in each expression, where N is the number of data used in the estimation. A number of competing expressions are considered for each property with the expression of choice being that which minimizes mean relative error. [ABSTRACT FROM AUTHOR]

Performance of adding phase change material (PCM) to small salinity-gradient solar pond was studied experimentally. Two ponds with an area of 3.4 m 2 and depth of 1 m were chosen. Horizontal cylindrical capsules containing Paraffin Wax as PCM were used in one of the pond’s lower convective zone. The capsules were made of black iron whose thermal conductivity was about 80 W/m °C and its height and diameter were 0.5 m and 75 mm respectively. The study was covered within period of summer for 6 weeks. An internal heat exchanger was used in the lower convective zone of pond. The hourly as well as daily variation of temperatures of the storage zone, surface zone, ambient, inlet and outlet of the internal heat exchanger have been measured and analyzed for ponds. It was shown the assisted PCM pond decreases the temperature difference between night and day. In addition, the pond had more thermal stability over environmental condition and more thermal and salinity stability on heat extraction. Hence the maximum temperature of the pond, outlet water temperature of heat exchanger, and, accordingly, the thermal efficiency decreased by using PCM. However, the heat exchanger outlet water temperature and, accordingly, the thermal efficiency, can be constant by increasing the length of the heat exchanger pipe. Therefore, based on this study, in such applications which one needs lower temperature difference and more uniform temperature, or where applications need a specific temperature range or controlled maximum temperature, PCM with a suitable melting point might be beneficial. [ABSTRACT FROM AUTHOR]

A salt gradient solar pond with porous medium bed has been paid more and more attention, due to potential positive effect of porous medium on the thermal performance of salt gradient solar pond and also the delay action salt diffusion. Stability of salt gradient solar pond depends on the maintenance of the salt gradient. In this paper the effect of the porosity porous material on the salinity diffusion under the constant Lower Convective Zone (LCZ) temperature is experimentally studied, and the cleaned and screened coal cinder was used as the adding porous material. Under the same salt gradient conditions, the salinity development of LCZ with porous medium layer with porosity of 61%, 65.5%, 67% and 74% is respectively studied, the blank experiment without adding any porous material was used for comparison, and according to the experimental data, the salt diffusion coefficient in each depth was calculated by numerical method. Experimental results show that within the experimental temperature range, the porous medium can delay the salt diffusion upward. Some signs show that the porous material seems to have the absorption effect on salt. The smaller porosity the porous medium is the more slowly salt diffuses. [ABSTRACT FROM AUTHOR]

This study investigated different shapes of solar ponds at two salt gradients. Ponds of rectangular and circular shapes with similar cross sections and volumes were examined. The results indicated that, with respect to shadow areas formed in both ponds, the maximum temperature of rectangular and circular solar ponds reached 74 °C and 71 °C, respectively, as a result of the smaller area of the shadow created in the rectangular solar pond. Moreover, the glazing plastic cover prevented heat from escaping the pond. This caused the temperature between the UCZ in both solar ponds and ambient to be 13 °C at the end of the test, hence causing a reduction of temperature difference from top to bottom of the ponds. Likewise, it was concluded that dusty weather negatively affected the efficiency of solar ponds and decreased the temperature in solar ponds in such a way that with weather returning to the normal condition (as it was before dust), the temperature of pond hardy went back to what it was after several days. On the other hand, plastic covers were applied to avoid turbidity of water in the pond as well as avoiding the entry of dust into the water, proving to have a positive effect on the preservation and sustainability of solar ponds. [ABSTRACT FROM AUTHOR]

A mini trapezoidal solar pond with surface 2.4 m × 2.4 m and bottom 1.0 m × 1.0 m is constructed. Thermal performance of the trapezoidal solar pond is numerically simulated by a one-dimension model base on the experimental data. The simulation builds a thermal and salt diffusion model, a modified bottom reflection and radiation transmission model, and a detailed heat dissipation model considering the heat loss from the surface, the wall and the soil layer. It shows a good agreement between the experimental data and the simulation. In the simulation the temperature of the trapezoidal pool is overall higher than that in the rectangular pool, the maximum difference is about 5 °C, and the trapezoidal structure contributes to reduce the heat loss of heat storage layer. It has great significance for the thermal performance of the solar pond to reduce the turbidity of upper convective zone and non-convective zone. The stability of the interface between non-convective zone and lower convective zone is better than that between upper convective zone and non-convective zone. [ABSTRACT FROM AUTHOR]

Desalination powered by renewable energy sources is an attractive solution to address the worldwide water-shortage problem without contributing significant to greenhouse gas emissions. A promising system for renewable energy desalination is the utilization of low-temperature direct contact membrane distillation (DCMD) driven by a thermal solar energy system, such as a salt-gradient solar pond (SGSP). This investigation presents the first experimental study of fresh water production in a coupled DCMD/SGSP system. The objectives of this work are to determine the experimental fresh water production rates and the energetic requirements of the different components of the system. From the laboratory results, it was found that the coupled DCMD/SGSP system treats approximately six times the water flow treated by a similar system that consisted of an air–gap membrane distillation unit driven by an SGSP. In terms of the energetic requirements, approximately 70% of the heat extracted from the SGSP was utilized to drive thermal desalination and the rest was lost in different locations of the system. In the membrane module, only half of the useful heat was actually used to transport water across the membrane and the remainder was lost by conduction in the membrane. It was also found that by reducing heat losses throughout the system would yield higher water fluxes, pointing out the need to improve the efficiency throughout the DCMD/SGSP coupled system. Therefore, further investigation of membrane properties, insulation of the system, or optimal design of the solar pond must be addressed in the future. [ABSTRACT FROM AUTHOR]

The solar hybrid Steam Injection Gas turbine (STIG) cycle uses both recuperated heat and solar heat in order to generate steam at a low temperature and pressure, and inject it into the cycle in order to augment the power output. This work addresses the addition of thermal energy storage to allow operation from solar energy beyond the daylight hours. An annual performance analysis of the Solar STIG cycle with latent heat phase change material (PCM) storage is presented for the climatic conditions of Sede Boqer, Israel. We show that the heat transfer limitation present in a real PCM storage leads to a slight performance penalty only compared to an ideal storage. We also analyze the impact of shifting electricity generation from daytime to evening, which can lead to a surprisingly high contribution of the thermal storage. Results show annual solar fraction of up to 35.2%. The annual solar to electricity efficiency was 20.1% when using the recuperated Brayton cycle as reference, and 13.9% for an optimal conventional STIG cycle as reference. These values are similar to or higher than the annual efficiency of current solar thermal power technologies, even though the hybrid STIG cycle uses low-grade solar heat at 200–280 °C. [ABSTRACT FROM AUTHOR]

In this work, a solar electrochemical-raceway pond reactor (SEC-RPR) is used to treat textile industrial wastewater by solar photoelectron-Fenton (SPEF) at pilot plant scale for the first time. The SEC-RPR is composed of an electrochemical filter press-cell coupled to RPR, where H 2 O 2 is electro-generated. A complete study about experimental variables such as current, catalyst concentration, pollutant load or liquid depth is conducted based on methyl orange removal, mineralization and decolorization. Validation of the SPEF process using SEC-RPR reached more than 80% of mineralization, as well as the complete decolorization of the solution. The good performance of the SPEF treatment in the new SEC-RPR led to quick degradation kinetics, mainly due to the synergetic action of solar radiation and good distribution of H 2 O 2 electrogenerated in the photoreactor. 100% Methyl Orange degradation was achieved after 150, 60, 45, 30 and 20 min of reaction time applying current density equal to 5, 10, 20, 40 and 60 mA cm−2, respectively. However, the increase of current density decreased the mineralization current efficiency. Up to 10 aromatics intermediates and 5 short-chain carboxylic acids were identified by LC-MS and HPLC analysis and a reaction pathway for MO mineralization by SPEF is proposed. This study represents an essential preliminary step towards the development of the first SEC-RPR at demo scale. • The application of SPEF process in a new electrochemical Raceway Pond Reactor (SEC-RPR) is proposed. • The system provided homogeneous distribution of electrogenerated H 2 O 2 in the RPR. • Almost complete mineralization of industrial textile wastewater was achieved in competitive treatment times. • Increasing current density increased Methyl Orange removal kinetics but decreased current efficiency. • 10 aromatics intermediates and 5 short-chain carboxylic acids were identified. [ABSTRACT FROM AUTHOR]