• Energy Research

This research aims to investigate the effect of integrating a simple solar collector, floatable black wicks, and orientation as modified double-slope solar still (MDSSS), and to compare its performance with conventional double-slope solar still (CDSSS). Costs of the developed desalination system were estimated, and its performance was compared with the previous literatures. A black hose was coiled and used as simple solar collector for preheating the saline water that is fed to the solar still. The floatable black wicks were used to increase the evaporation surface area and cause a localization of absorbed insolation at the evaporation surface of saline water. The longitudinal axis of solar still was oriented to north-south and east-west, the and productivity from each side was quantified. The northern side of MDSSS has more yield than the southern side by 33.98% for the east-west orientation and preheating. For the east-west orientation, preheating, and floatable black wicks, the total yield of MDSSS exceeded the CDSSS by 45.65%. And at the same conditions, the daily average efficiency of southern and northern sides of MDSSS was 25.33 and 37.25%, while for CDSSS, it was 13.87 and 30.73%, respectively. Estimated costs revealed that cost per liter water was about 0.062 and 0.059 $ for CDSSS and MDSSS, respectively. Solar still can provide a reasonable amount of water for irrigation based on daily production by installing the MDSSS in furrow, but keeping the longitudinal axis to east-west can secure more amount of water. The used modifications improved the solar still productivity and efficiency. Graphical abstract.

Energy is an essential ingredient of socio-economic development and economic growth. Renewable energy provides a variable and environmental friendly option and national energy security at a time when decreasing global reserves of fossil fuels threatens the long-term sustainability of global economy. The integration of renewable resources in desalination and water purification is becoming increasingly attractive. This is justified by the fact that areas of fresh water shortages have plenty of solar energy and these technologies have low operating and maintenance costs. In this paper an attempt has been made to present a review, in brief, work of the highlights that have been achieved during the recent years worldwide and the state-of-the-art for most important efforts in the field of desalination by renewable energies, with emphasis on technologies and economics. The review also includes water sources, demand, availability of potable water and purification methods. The classification of distillation units has been done on the basis of literature survey till today. A comparative study between different renewable energy technologies powered desalination systems as well as economics have been done. The real problem in these technologies is the optimum economic design and evaluation of the combined plants in order to be economically viable for remote or arid regions. Wind energy technology is cheaper than the conventional ones, and used extensively around the world. The slow implementation of renewable energy projects especially in the developing countries are mostly due to the governments subsides of conventional fuels products and electricity. The economic analyses carried out so far have not been able to provide a strong basis for comparing economic viability of each desalination technology. The economic performances expressed in terms of cost of water production have been based on different system capacity, system energy source, system component, and water source. These differences make it difficult, if not impossible, to assess the economic performance of a particular technology and compare it with others. Reverse osmosis is becoming the technology of choice with continued advances being made to reduce the total energy consumption and lower the cost of water produced.

Abstract This paper presents a new hybrid desalination approach comprising of evacuated solar water heater, jut geotextile and solar still. An evacuated solar water heater is integrated with the desalination stills to evaluate the continuity production of distillate. Two identical portable solar wick and one basin solar stills were designed to evaluate the systems performance. Jut linen woven fabrics were stitched to the plane wick (lengthwise and crosswise) and integrated with solar still. The jut fabrics were used to reduce the rate of water flow to the appropriate rate. The following variables are studied: Single and double layers wick; plane wick, lengthwise and crosswise linen; feeding hot water during night and two base slope angles of wick still (20 and 30°). Theoretical analysis is verified through experiments. Water productivity is increased by 114% over conventional still for double layer square wick (DLSW) solar still at 30° base slope angle. The daily average efficiency of DLSW was 71.5%. During experimentation, the distillate water productivity increased by 215% when hot brackish water was fed during night time.

The photovoltaic (PV) system is one of the renewable energies that attract the attention of researchers in the recent decades. The PV generators exhibit nonlinear I–V and P–V characteristics. The maximum power produced varies with both irradiance and temperature. Since the conversion efficiency of PV arrays is very low, it requires maximum power point tracking (MPPT) control techniques. The maximum power point tracking (MPPT) is the automatic control algorithm to adjust the power interfaces and achieve the greatest possible power harvest, during moment to moment variations of light level, shading, temperature, and photovoltaic module characteristics. The purpose of the MPPT is to adjust the solar operating voltage close to the MPP under changing atmospheric conditions. It has become an essential component to evaluate the design performance of PV power systems. This investigation aims to assess different MPPT techniques, provide background knowledge, implementation topology, grid interconnection of PV and solar microinverter requirements presented in the literature, doing depth comparisons between them with a brief discussion. The MPPT merits, demerits and classification, which can be used as a reference for future research related to optimizing the solar power generation, are also discussed. Conventional methods are easy to implement but they suffer from oscillations at MPP and tracking speed is less due to fixed perturb step. Intelligent methods are efficient; oscillations are lesser at MPP in steady state and tracked quickly in comparison to conventional methods.

Abstract The traditional method (TM) of dates syrup (dibs) extraction takes long extraction period and has poor productivity. The TM depends on putting heavyweights above the heap of dates at room temperature, and wait until dibs extraction. This study aims to design two innovative solar electro-thermal energy systems with hydraulic pressure to extract dates syrup. The electro-thermal systems were used to heat and circulate dates dibs extraction medium, while hydraulic pressure (6 ± 1 and 7 ± 1 bar) was used to squeeze dates instead of traditional weights. Solar water bath (SWB) and solar air bath with rocks storage bed (SABWRSB) were used to catalyst the extraction process. The syrup dibs quality and quantity from different methods were evaluated. For innovative methods, the dates temperature inside the extraction tank was about 49–54 °C. The efficiency of the SWB and SABWRSB for syrup extraction was 48.87% and 13.16%, respectively. Using SWB saved time about 38%, and increased the productivity by 28.75% and 36.66% at a pressure of 6 ± 1 and 7 ± 1 bar, respectively, compared to TM. Heating with SWB increased the productivity by 3.6% and 5.68% compared to SABWRSB at 6 ± 1 and 7 ± 1 bar, respectively. The SWB is recommended for providing the appropriate environment for the dates dibs extraction.

Abstract Solar PV system powered mixed-mode solar tunnel dryer (STD) for drying potato chips was studied. The STD was equipped with axial dc fan and flat plate solar air collector to enhance the thermal performance by maintaining a reasonable high temperature inside the drying chamber. The STD performance was evaluated without load and with load; and without and with using thermal curtain above potato slices during sunny days. Different airflow rates (2.1, 3.12 and 4.18 m3/min) and pre-treatments for potato slices were investigated. The PV powered STD exhibited the ability to produce chips with safe moisture level within 6 and 7 h for without and with using thermal curtain, respectively at airflow rate of 3.12 m3/min. The frying time of potato chips was shortened to be only 15 s. The best chips color was achieved with 1% sodium meta-bi-sulphite with using black thermal curtain above slices. Predicted and experimental moisture ratio of chips using developed STD were compared through several thin-layer drying models. The highest drying efficiency of 28.49 and 34.29% was recorded at airflow of 0.0786 kg/s in case of without and with using thermal curtain, respectively. The developed STD provides chips in good quality and suitable for rural areas.

Abstract In this work, the performance of solar still was enhanced using nanotechnology and cotton hung pad. The cotton hung pad has threads with ends immersed in seawater, hence the capillary property moves the water upward towards the evaporation surface. The cotton hung pad (small layer), and nanoparticles have a significant effect on localizing the heat that speed up the seawater evaporation rate and improve the performance. The Fe3O4, and CuO nanoparticle materials are used and spreaded to the top surface of the cotton pad with different concentrations in the range of 25 g/m2 to 300 g/m2. Also, the exergoeconomic of the desalination system and environmental analysis are investigated. The results showed an enhancement of about 17.55% in the productivity for the modified solar still (MSS) with cotton hung alone compared with the TSS. The configuration of cotton hung pad and nanoparticles with a concentration of 150 g/m2 enhanced the distillate productivity by about 42.3% and 56.6% for Fe3O4 and CuO nanoparticles, respectively compared to TSS. The highest efficiency was about 51%, 45%, 34.5% and 30% for MSS with CuO, MSS with Fe3O4, cotton hung pad only and TSS, respectively. The exergy values showed enhancement of 103% for MSS with CuO compared to TSS. The economic analysis of different modifications indicated that the cost per liter of fresh water was 0.018 $, 0.016 $, and 0.015 $ for MSS with cotton pad and Fe3O4; cotton pad and CuO; and cotton pad only, respectively while the cost for TSS was 0.0189 US$. Furthermore, the exergoeconomic and environmental analysis of enhanced solar stills showed that these systems are cost-effective and helpful in cutting down carbon footprint by mitigation of CO2. Overall, integrating nanoparticles with cotton hung pads were proved to be very effective and promising from economic, environmental, and exergy point of views.

Abstract This work presents a design and installation of solar dish concentrator (SDC), simple solar collector and modified boiler for brackish water desalination. The design of two axes tracking system is performed using an open-loop control based on programmable logic controllers (PLC). Glass mirrors are used as reflective surface for dish concentrator. A coiled black rubber hose is used to preheat brackish water before feeding to the boiler. A mini single slope-air tight solar still is designed and installed at the focus of dish concentrator which is used as a boiler. The automatic tracking system, new boiler design; and with and without preheating of brackish water are investigated. The developed desalination system is evaluated and compared with the conventional solar still (CSS). The results indicated that, the daily average of distillate water was 6.7 l/m 2 /day for SDC with preheating of brackish water, while the distillate productivity was 1.5 l/0.5 m 2 /day for CSS. In the present study, the daily average efficiency of SDC and CSS was 68 and 34%, respectively. The increase in distillate production for SDC is about 244% and 347% higher than that of CSS without and with preheating, respectively.

Abstract This paper offers a hybrid solar desalination system comprising a humidification-dehumidification and four solar stills. The developed hybrid desalination system reuses the drain warm water from humidification-dehumidification to feed solar stills to stop the massive warm water loss during desalination. Reusing the drain warm water increases the gain output ratio of the system by 50% and also increased the efficiency of single solar still to about 90%. Furthermore, the production of a single solar still as a part of the hybrid system was more than that of the conventional one by approximately 200%. The daily water production of the conventional one, single solar still, four solar still, humidification- dehumidification and hybrid system were 3.2, 10.5, 42, 24.3 and 66.3 kg/day, respectively. Furthermore, the cost per unit liter of distillate from conventional one, humidification- dehumidification and hybrid system were around $0.049, $0.058 and $0.034, respectively.