Solar photovoltaic modules play a vital role in the global clean energy transition. However, their efficient performance is hindered by rising operating temperature especially under harsh environments. Conversion efficiency of modules drops by at least 0.4–0.5 % for each 1.0 °C increment in its operating temperature from the standard testing condition of 25.0 °C. Hence, thermal management is essential for a module's sustained efficient performance. Evaporative cooling with water is more effective than any other passive module thermal management technique. In spite of seawater's abundance and inexpensiveness, it has not yet been utilized for module evaporative cooling in any of the available literatures. Hence, in this work, a novel passive evaporative cooling system utilizing a still seawater layer over a horizontally oriented module is proposed and tested under the climatic conditions of Visakhapatnam, Andhra Pradesh, India. This approach reduced module temperature on an average by around 8.8 °C. A 5.0 mm thick seawater layer improved the module's instantaneous power output by 0.14–31.0 %. Despite providing a tremendous cooling effect, seawater layer thickness of 30.0 and 4.0-mm had negative impact on a module's daily energy output due to increased light attenuation at high thickness and salt deposition caused by fast evaporation under low thickness, respectively. Low relative humidity and high wind speed facilitated rapid seawater evaporation, resulting in salt buildup over the module, emphasizing the importance of constant makeup water supply while operating at low water thickness (less than 5.0 mm) to avoid dry out. The overall heat transfer co-efficient of evaporatively cooled module was about 69.38–92.89 W/m2K, which was at least twice the value observed with the reference module. The observed results justifies the proposed thermal management technique because it is efficient and competitive with fin and phase change material-based module thermal management strategies. This highlights the necessity for further research and development towards improvement of this proposed technique for large scale applications.

This study proposes a novel stagnant water layer cooling concept to enhance performance of solar photovoltaic (PV) modules. Three distinct types of water-seawater (Scenario 1), tap water (Scenario 2), and desalinated water (Scenario 3)-were utilized to cool a 10 WP polycrystalline PV module by establishing a stagnant layer of 1.0 cm thickness over it, under the climatic conditions of Visakhapatnam (17.62°N, 83.21°E), India. The average daily temperature variations between the reference and modified PV modules were approximately 7.0 °C, 7.2 °C, and 8.2 °C for Scenarios 1, 2, and 3, respectively. The daily average electrical efficiency & energy output of the modified PV modules under Scenarios 1, 2, and 3 were approximately 16.2 & 14.9, 18.6 & 16.6, and 30.8 & 28.3%, relatively higher than the reference PV module, respectively. Exergy efficiency, sustainability index and specific CO2 emission of desalinated water-cooled PV module were 7.41%, 1.08, and 406 g/kWh, respectively. However, the desalinated water-cooled PV module exhibited 29.1 and 15.1% higher evaporation losses than those of the seawater and tap water-cooled PV modules, respectively, under similar solar energy of 21.4 MJ/m²d. The proposed cooling technique is effective and economic, depends on the type of utilized water.

Easy access to grid electricity and clean water is practically impossible in developing nations' arid coastal desert sites. However, this problem can be solved by harnessing the copious solar energy and saline water supplies in these areas. This study proposes a photovoltaic (PV) module-based co-generation system known as the PV-DESAL module, which can generate electricity & desalinated water and conceptually investigates the same in twentythree African and Asian sites. Polycrystalline PV module of 335 Wp incorporated as absorber in the PV-DESAL module effectively utilized the waste heat energy to produce desalinated water passively. Because of its vertical orientation, superior performance was found during the winter months than in the summer months at the analysed sites (5-36 degrees Latitude). In the African and Asian sites under consideration, the PV-DESAL module's annual electricity output potential varied from 293.0 to 474.0 kWh and 310.0 to 450.0 kWh, respectively. The annual desalinated water generation potential of the PV-DESAL module was around 226.0-462.0 kg and 262.0-556.0 kg in the African and Asian sites, respectively. The PV-DESAL module had an electrical, exergy, cogeneration efficiency and sustainability index of at least 15.0 %, 17.0 %, 24.0 %, and 1.21. The specific CO2 emission of PV-DESAL module was around 0.10-0.16 kg per kWh of electricity generated and 0.08-0.20 kg per kg of desalinated water generated. The performance index results suggested that the PV-DESAL module is viable and may favourably contribute to the sustainable development of nineteen of the twenty-three arid coastal desert sites.

Water stress and water quality represent major environmental challenges in the 21st century. In response, wastewater management and its potential reuse emerge as strategies to mitigate these problems. This research aims to verify the law of reciprocity in the solar disinfection process of real secondary wastewater effluents for different faecal microorganisms. Flat disinfection reactors, subjected only to natural and continuous UV radiation, were used. The study focused on the optical effect of UV radiation, eliminating the significant influence of the thermal effect and its synergy in solar disinfection at temperatures above 45 °C, by controlling the temperatures of the water samples to levels below 20 °C. Three experimental tests were carried out on sunny days. Each test comprised two trials, under the following conditions: (a) low solar irradiance over a prolonged time (duration approximately: 2.6 h) and (b) high solar irradiance and a shorter period of time (approximately 2 h), with each receiving the same UV dose. Inactivation kinetics was analysed for E. coli, E. faecalis, and C. perfringens (including spores). The results validated the reciprocity law for E. coli in all tests for UV doses > 20 Wh/m2, showing no significant deviations, with inactivation rates of 0.44 to 0.51 m2/Wh for initial concentrations of 106–107 CFU/100 mL. In contrast, for E. faecalis, the reciprocity was only valid at intensities < 700 W/m2, with rates of 0.04 and 0.035 m2/Wh for 105–106 CFU/100 mL; above this irradiance value, the law varied significantly and was not valid. C. perfringens did not show significant disinfection results during the experiments to verify this law, mainly due to the resistance of its spores. Additional experimentation with C. perfringens is necessary, by extending the length of the experiments and/or conducting them at higher irradiance values, in order to reach bacterial inactivation to enable the analysis of the reciprocity law. In general, the main conclusion from these results is that the reciprocity law in solar disinfection would be difficult to use for the estimation of water solar disinfection based on the irradiance and exposure times, as there are deviations from it at least in one specie (E. faecalis). Mores studies should be carried out to fully understand and determine the validity of this law and its potential application for forecasting solar water disinfection.

Development of the Open SolWat system, which uses exclusively solar energy and is intended for tertiary treatment in a WWTP, as it could improve environmental sustainability and reduce energy consumption. Two prototypes of different sizes have been studied: Small and Large Open SolWat. These consisted of an open water disinfection reactor on a photovoltaic module, which had a pumping system that constantly cooled the surface of the module by means of a thin film of free-falling wastewater. The experiments took place on sunny days with climatic variability. Microbiological, physicochemical and photovoltaic performance analyses of the system were carried out. Large Open SolWat stood out with very beneficial results. It obtained reclaimed water after a SODIS treatment of 4 h under real sunlight, which could be used for other uses according to Spanish (RD 1620/2007) and European (R(EU) 2020/741) regulations. Simultaneously, the system generated energy with an energy efficiency that improved by 15-21 % compared to the reference PV module, as a consequence of the successful cooling of the module temperatures (16.2-30.6 degrees C) with wastewater. The energy generated could be used to selfsupply the pumping system and compensate the energy demand of a WWTP in the future, using renewable energy.

Water and energy are intimately related, as water is required for energy applications and energy is required for water-based technologies. Two large groups of photovoltaic adoptions have been identified in this review: first, those in which the photovoltaic system is separated from the water technology. In second group, the photovoltaic system is in physical contact with the water technology thereby its performance is affected either in a positive or negative way. The novelty of this review work lies in the classification of photovoltaic system adoption in various water related technologies. Apart from classification, discussions on system configurations, working aspects, performance aspects, economic aspects and scope for further investigations have been presented in detail. Wastewater treatment plants are identified to be the most suitable site for photovoltaic module installation and utilization. Among power sectors, hydro power plants are highly compatible with photovoltaic adoption because it enhances hydro power plant's operation time and utilization. Floating photovoltaic, submerged photovoltaic, agrivoltaic, aquavoltaic and solar photovoltaic + water disinfection are relatively new, highly attractive and have more scope for further improvements. Agrivoltaic and aquavoltaic increases crop & sea food production, enhances farmers' income, encourage clean energy transition and rural electrification. Research works in the area of unmanned photovoltaic based water vehicles, photovoltaic salt harvest and various applications of water based photovoltaic/thermal modules have also been discussed. This review will serve as a guidebook for re-searchers and policy makers to identify and select suitable configuration of photovoltaic-water related technologies for implementation and further investigations.

The aim of this study is to verify the reciprocity law in the wastewater disinfection process using UV light. The optical power UV-LEDs used were 1.6 mW and 50 mW, and the wavelengths were 265 nm and 275 nm. E. coli, Enterococcus faecalis, and Clostridium perfringens were the three microorganisms analysed in the study. The results showed lower inactivation rates around 0.063–0.065 cm2/mJ for 265 nm and 0.047–0.049 cm2/mJ for 275 nm for the Clostridium perfringens compared with the other two bacteria. For E. coli and Enterococcus faecalis, the inactivation rate was almost identical; 0.28 and 0.21 cm2/mJ, respectively, using 265 nm wavelength. There was a slightly better inactivation performance using the medium-power 275 nm UV-LEDs of 0.39 cm2/mJ and 0.29 cm2/mJ for E. coli and Enterococcus faecalis, respectively, and 0.33 cm2/mJ and 0.26 cm2/mJ using the low-power 275 nm UV-LEDs. The analysed data justify the reciprocity law for UV-LEDs disinfection using 265 nm and 275 nm UV-LEDs with two optical powers of 1.6 mW and 50 mW.

Energy consumption in wastewater treatment plants (WWTP) is a critical part of their operation and maintenance costs, with tertiary treatments being one of the most energy demanding stages, although as they are not required by law, they are not usually included in the wastewater treatment line. In this research, a photochemical–photovoltaic hybrid system was developed and studied: Open SolWat, which allows solar disinfection of the water while cooling the temperatures on the front surface of the photovoltaic module by means of a thin layer of water flowing from the top, thanks to a pumping system. In comparison to the SolWat technologies studied so far, the improved system allowed better quality reclaimed water (RD1620/2007, R(EU)2020/741) to be obtained from the secondary effluent of a WWTP, with the simultaneous generation of energy. However, this time it also productively improved its energy efficiency (15–21%). The tests were carried out under a 4 h SODIS treatment with real sunlight. Therefore, the possible implementation of the system as a tertiary treatment of a WWTP is considered, as it could improve environmental sustainability and reduce energy consumption.

The efficiency of photovoltaic panels decreases with the increase in panel temperature while converting light into electricity. The issue of temperature rise and the associated decrease in efficiency has been widely analysed by active and passive cooling methods. In those processes, normally water is used as a cooling medium, and it results in water loss along with power loss due to circulating or compensating for the lost water. The current study aims to address both efficiency as well as water loss by combining an evaporative cooling technique with a solar still. A Photovoltaic panel with rear-side evaporative cooling is attempted by using a jute sack dipped in water at both ends. As a result of capillary action, the water from a solar still rises through the sack and cools the panel's rear side. Solar still operation is ensured by an extended portion of glass. During desalination, the evaporated vapour from the solar still condenses on the back cover of the glass surface and is collected in a collection trough. As a result, the output power increased by 5.6 % and the electrical efficiency increased by 14.51 % and the surface temperature are reduced by 8 degrees C. After seven hours of sunshine, the proposed PV panels and solar still system produced approximately 550 ml of water.

Sustainable production of potable water is one of the United Nations sustainable development goals set for 2030. Among available renewable energy resources, solar energy is abundantly available in most of the fresh water scarce rural and remote locations. Moreover, solar distillation units and solar photovoltaic (PV) modules have been acknowledged as suitable candidates for addressing rising fresh water and electricity demands in these regions. In recent years, researchers have proposed a number of novel hybrid solar distillation units where the solar PV modules are integrated with solar thermal distillation units in different ways to harvest both electric power and potable water. In this work, a detailed review highlighting the classification, working principle, performance and features of these novel hybrid units have been carried out. In most of these hybrid units, integration is highly beneficial for solar thermal distillation units rather than for PV modules. Direct utilization of PV module as absorber, condenser and reflector in solar stills has few drawbacks. However, indirect utilization like utilizing electric power and waste heat energy recovered from PV module in distillation units has posed significant distillate yield enhancement up to 300.0%. In some cases, the integrated PV module has even generated sufficient power for carrying out essential domestic activities. Integrated PV module's performance has also improved significantly in few studies but the magnitude of improvement has not been disclosed clearly in most of the studies as more focus has been given to distillation units rather than PV modules. However, these novel hybrid configurations have not been fully explored & optimized and their techno-enviro-economic aspects have not yet been disclosed in these available precious literatures and they are still available as a potential research gap.

Two hybrid SolWat systems operating in static (without flow circulation) versus dynamic (with flow circulation) mode were simultaneously compared. This work aims to demonstrate the viability of SolWat in dynamic mode to: a) adapt to the operation of the WWTP with a continuous flow, in which the wastewater flows continuously for treatment, b) treat a larger volume of water in the system and c) increase the cooling of the PV modules thanks to the cooling of the temperature of the water sample to improve the energy efficiency in the system. Real secondary wastewater effluents from wastewater treatment plants were used, using solar energy for water disinfection and photovoltaic energy production, in order to use the SolWat systems and implement it as a tertiary treatment. A total of five experiments were performed during autumn, winter, spring and summer. Solar disinfection of Escherichia coli, Enterococcus faecalis and Clostridium perfringens was assessed, and physicochemical parameters were also analysed. The UV dose received by the SolWat systems was the same, but not for the microorganisms in the water sample. The static SolWat irradiated a particle (microorganism) for 4 h, while the dynamic SolWat irradiated intermittently, so the latter system received a shorter UV exposure time, and therefore a lower UV dose. Results indicated that, although the microorganisms did not obtain the absolute bacterial inactivation during the SODIS treatment in any SolWat system, adequate inactivation levels were achieved to allow the reuse of the water for various uses (Royal Decree 1620/2007, Regulation (EU) 2020/741), although to a lesser extent for SolWat in dynamic mode, which treated twice the volume of water and reached cooler temperatures. C. perfringens proved to be the most resistant bacterium tested. The total photovoltaic energy production in the dynamic mode system was more energy efficient than the static mode, being even more efficient than the single PV reference system during the spring (3.5%) and summer (2.7%) test, due to the compensating effect by the cooling of the water on the photovoltaic module against the losses caused by radiation.

Environmental bacteria strains are known to be more resistant but studies on UV-LEDs are scarce, especially for Clostridium perfringens and Enterococcus faecalis. UV-LEDs of different wavelengths (268 nm, 279 nm and 307 nm) have been used for treating real wastewater from the effluent of the municipal plant in Linares (Spain), with real organic matter content, for E. coli, Enterococcus faecalis and Clostridium perfringens disinfection. Experimental results demonstrate that 268 nm was the most effective wavelength for inactivation of the three different bacteria strains: E. coli showed an inactivation rate of 0.561 at 268 nm vs. 0.245 at 279 nm and 0.0029 for 307 nm; E. faecalis inactivation rate was 0.313 at 268 nm, 0.231 at 279 nm and 0.0023 at 307 nm; and C. perfringens inactivation rate was 0.084 at 268 nm, 0.033 at 279 nm and 6.9e-4 at 307 nm. In general, 307 nm wavelength showed a significantly lower inactivation rate so it would not be recommended for practical applications. C. Perfringens required higher UV doses and longer times to achieve complete inactivation.

SolWat is a hybrid photovoltaic (PV) and photochemical technology, which integrating a PV module and a water disinfection reactor on top of it, was developed to meet the needs of safe drinking-water and electricity in developing countries. This paper assessed the effects of the water disinfection reactor on the electrical performance of the PV module integrated into the SolWat system regarding different hydraulic retention times (HRT) and PV technologies. With this aim, several tests were conducted outdoors under natural climatic conditions. Results showed that while no clear benefits were observed from the water disinfection reactor and reduced HRT on the electrical performance of both monocrystalline and multicrystalline technologies, the final energy output of a-Si thin film PV panels benefited from the cooling effect of water on its front surface being able to produce even more energy than a single PV panel when working at shorter HRT. In addition, the working module temperature was always lower when HRT was shorter; its efficiency under the diffuse light conditions created by the water disinfection reactor was better than monocrystalline and multicrystalline technologies; and its black surface enhanced the absorption of far infrared light and heat by the water disinfection reactor favouring higher water temperatures and thus higher disinfection rates. In conclusion, thin film PV technology is the most suitable to be integrated into the hybrid SolWat systems when comparing with monocrystalline and multicrystalline technologies.

Millions of Solar Home Systems (SHSs) have been progressively installed in rural areas of developing regions, usually in isolated locations that lacked access to electricity, clean water and/or sanitation. Monitoring has been identified as a one of the factors that contribute in rural electrification program success due to these actions increase the system lifetime and reduce the failure of operation of the PV system, improving confident level of the users on the system. This work focuses on the study of the current challenges for the mass scale SHSs monitoring in developing countries, highlighting the weak-nesses and the strengths of the applicable methods available. Monitoring systems applicable to SHSs are reviewed, including conventional dataloggers and the novel attempts that apply new technologies based on open source tools and the Internet of Things (IoT). Sensor distributions applicable to SHS monitoring have been reviewed. Main shortcomings related to conventional monitoring systems such as the elevated cost or the dependency on external hardware have been identified, issues that hinder their application of the mass-scale monitoring. Low-cost IoT-based monitoring systems are reviewed and presented as a potential solution to the mass-scale monitoring of SHSs. (c) 2020 Elsevier Ltd. All rights reserved.

This work evaluates the SolWat hybrid system for solar water disinfection and photovoltaic energy generation, for its implementation in tertiary treatment plants, using real wastewater directly from the effluent after its secondary treatment. Solar disinfection of E. coli, Enterococcus faecalis and Clostridium perfringens microorganisms was evaluated over the course of a complete year. Four experiments in batch mode were conducted in autumn, winter, spring and summer, and microbiological and physicochemical parameters were analysed. In addition, the kinetics of solar disinfection during 4 h were analysed, and the dose of lethal ultraviolet radiation for microorganisms established. Results showed that E. coli, Enterococcus faecalis and C. perfringens did not complete total bacterial inactivation after 4 h of treatment in the SolWat system, but that the inactivation levels achieved were sufficient as to allow for the reuse of water for various uses (urban, agricultural, industrial, etc.). Clostridium perfringens continued to be the most resistant bacteria vs. E. coli and Enterococcus faecalis. The total photovoltaic energy production in the hybrid system compared to the reference system was the same, generating both the SolWat module and the reference module identical electrical power due to the compensating effect of module water cooling vs. radiation losses.

Appears in: EDULEARN20 Proceedings Publication year: 2020Pages: 4006-4012ISBN: 978-84-09-17979-4ISSN: 2340-1117doi: 10.21125/edulearn.2020.1080Conference name: 12th International Conference on Education and New Learning TechnologiesDates: 6-7 July, 2020Location: Online Conference

A novel SolWat system designed exclusively as a Solar Home System that also meets the drinking water access in a family of a rural community in a developing country has been designed, manufactured and tested outdoors. The system is composed of 5 photovoltaic modules of monocrystalline silicon solar cells technology, each 20 Wp, parallel-interconnected, adding up to a 100Wp system. The modules have a water reactor on top with the capacity of providing a minimum of 37.5 L per day for a family of 5 members, guaranteeing the minimum daily needs. Experimental campaign run tests of SODIS of 3 h each, running the system 3 times per day (with a total of 9 h of experimentation per day). Results show that the water treatment of 3 h should be increased at certain periods of the day when the UV dose is not sufficient (late in the afternoon). E. coli and Enterococcus spp achieved total inactivation or almost total disinfection. Regarding electrical production, although energy losses of 5.6-10% were observed in comparison with a single PV module, it was sufficient to fully meet the load demand of the solar home system. The system could be used in a household of a developing country, using only solar energy to meet the electricity and drinking water demand. (C) 2020 Elsevier B.V. All rights reserved.

Developing countries have vast areas and large population groups where access to electricity and safe drinking water is still limited or inexistent. In Mexico, 1.1 million people do not have access to electricity, while more than 3 million people lack access to clean water. However, Mexico presents one of the best locations to exploit solar sources. Therefore, off-grid photovoltaic (PV) systems and solar water disinfection (SODIS) are two promising options to develop rural electrification and to improve the coverage of drinking water access. In this regard, the technology proposed consists of a hybrid photovoltaic and solar disinfection system (SolWat) that comprises a photovoltaic module and a water disinfection reactor fully integrated into a single unit. Its effectiveness was tested for the first time in a rural community of Oaxaca (Mexico), on the basis of natural climatic conditions and available drinking water sources. Main results showed that despite the meteorological conditions were not the most favourable, the strong solar irradiation conditions of Mexico allowed complete inactivation of E. coli and total coliforms after 3 h of sun exposure. Furthermore, although the SolWat PV module presented a decrease in ISC, the refrigeration effect of the water being purified on top of the PV cells compensated this loss. In conclusion, the present work confirms the feasibility of the SolWat system to contribute to mitigate the lack of access to safe drinking water and energy in developing countries, since under real operation conditions it was able to simultaneously produce clean water and electricity.

Internet of Things (IoT) makes a significant contribution to development in economical, social and ecological terms. In this work, the current context to successfully apply IoT in developing countries to achieve the Sustainable Development Goals (SDGs) of United Nations is studied. Potential and opportunities of the IoT in the developing world as well as the current challenges of IoT in developing countries are reviewed. The research methodology is focused on the IoT context in the developing world as well as profitable IoT projects carried out in developing countries, using the SDGs as a reference. Key features as a technical challenges, environmental conditions or social differences are studied to contextualize IoT in developing countries. Finally, the combination of low-cost IoT and pay-as-you-go is presented as the best scenario to better disseminate the Internet of Things for Development (IoT4D) to achieve the Sustainable Development Goals by 2030.

Though the solar photovoltaic (PV) module is used for power production, it usually works at high temperatures, decreasing its efficiency and therefore its output. So if an effective cooling method is to be implemented, it would reduce the heat from the solar PV module and increase its power production. Significant research in water cooling on both top and bottom surfaces of the PV module widen the scope for uniform cooling with constant module temperature throughout at any instant. In this work, uniform flow is maintained by means of overflow water from a tank fitted on the top of the PV module. Experiments were carried out with and without cooling. Performance parameters in terms of power output and efficiency have been presented for the PV module without cooling and cooling with three different mass flow rates. The results show that there is a significant rise in efficiency of the PV module by reducing its temperature. An accelerated output power of 23 W has been observed for a higher mass flow rate of 5.3 kg/min which is 15% higher than the photovoltaic module operating without cooling. Results were compared with previous researchers’ work and found to be a good enhancement. Theoretical results agree well with experiments.