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The standard flat-plate solar collector utilises a single copper tube to remove the absorber plate’s heat. This type of collector’s primary purpose is to provide hot water for a single application. Hot water can be required for different applications at different temperatures. Besides, using the standard collector’s configuration may increase thermal demand and increase the collector’s size. Therefore, this study proposes a novel solar water heating configuration that uses three in-line fluid passages. The goal is to design a single collector that provides hot water for various uses: Sterilisation, washing, and postnatal care. Thus, the proposed system was modelled, and a numerical simulation conducted. This analysis compares the proposed system’s output and the standard collector’s output. The results showed that the thermal load demand was reduced by 27% when the hot water demand for these services was generated using three separate tanks. The serpentine collector’s efficiency with three fluid passages is increased by 20% compared to the traditional serpentine collector. The thermal energy delivered to meet load was 30% higher than that of the traditional serpentine system. The experimental and simulated system performance is in near agreement with an average percentage error Cv(RMSE) of 8.75% and confidence level NSE of about 87%. Since the proposed serpentine collector has a higher overall thermal production, it is recommended for use with hot water, which has to be heated to different temperatures.

This work aims to quantify the long-term performance improvement of solar water heater system by using both simple and hybrid nanofluids. For this purpose, transient system simulations of a flat plate solar collector have been carried out and discussed using titanium oxide, magnesium oxide, and copper oxide/multiwalled oxide–carbon nanotube nanofluid-based nanoparticles. Tunisian climatic conditions with a typical household need has been considered, and the investigations have been established in terms of energy amounts, solar fractions, and harmful CO 2 emission avoidance. Results showed an increase in the collector performances using the considered nanofluids. In particular, using 0.2v% and 0.6v% TiO 2 homogeneously dispersed in water reduced the auxiliary energy up to 47.6 and 60.9%, respectively, compared to the reference case using water. The flat plate solar collector has an annual production of 1294 kWh for a need of 1998 kWh, which equates to an annual coverage rate of roughly 65%. Additionally, it was shown that when MgO with MWCNT were used instead of MgO nanofluid-based nanoparticles, the solar fraction increased by 5.14%. The use of 0.6 volume percent TiO 2 nanoparticles in water reduces hazardous CO 2 emissions by up to 0.829 tons annually.

Solar-powered absorption refrigeration systems have the potential to substitute conventional vapor-compression refrigerators in high solar irradiance areas with extensive cooling demands. Their feasibility relies significantly on system design and site. This study conducts an in-depth techno-economic and environmental assessment of an optimum solar absorption refrigeration system for Madinah, Saudi Arabia’s hot desert climate. A TRNSYS model for the dynamic system was developed, and a multi-variable parametric analysis was conducted in an attempt to ascertain the optimal configuration. The optimized design, an array of 100 m² evacuated tube collectors tilted at 38° and a storage tank of volume 1.5 m³, has an annual solar fraction of 32%. Economic analysis indicates high economic viability with the initial investment of $90,223, having a rapid Discounted Payback Period of 3.33 years, with a high Internal Rate of Return of 32.2% and a low Levelized Cost of Cooling of $0.028/kWh. Environmentally, the system accounts for an overall saving of 272.2 tonnes of CO 2 emissions per year. The report does contain a major negative point: a projected annual water consumption of 827.78 m³ of the cooling tower. The findings provide a sound, fact-oriented guide for the implementation of clean energy technology in desert environments but indicate the requirement for additional research in water-saving heat rejection technology and advanced control strategies for maximum sustainability.

To improve the adaptability of solar refrigeration systems to different heat sources, a single-double-effect LiBr−H 2O absorption refrigeration system (ARS) driven by solar energy was designed and analyzed. The system was optimized using a multi-objective optimization method based on Sobol sensitivity analysis to enhance solar energy efficiency and reduce costs. The model of the solar single-double-effect LiBr−H 2O ARS was developed, and the continuous operation characteristics of the system in different configurations were simulated and compared. The results show that the average cooling time of the system without auxiliary heat source is approximately 8.5 h per day, and the double-effect mode (DEM) generates about 11 kW of cooling capacity during continuous operation for one week under the designated conditions, and the system with adding auxiliary heat source meet the requirements of daily cooling time, the solar fraction (SF) of the system reaches 59.29%. The collector area has a greater effect on SF, while the flowrate of the hot water circulating pump and the volume of storage tank have little effect on SF. The optimized SF increases by 3.22% and the levelized cost decreases by 10.18%. Moreover, compared with the solar single-effect LiBr−H 2O ARS, the SF of the system is increased by 15.51% and 17.42% respectively after optimization.

The main categories of solar water heating systems (SWHSs) are the thermosyphon and the forced circulation (FC). This paper presents an experiment carried out with the aim to compare the energy performance of the FC with a thermosyphon SHWS. Identical SWHSs were installed side by side at the University of West Attica in Athens, Greece. Domestic hot water load was applied to both systems via a microcontroller-based dispensing unit which mimics the demand profile. The trial period comprised the last two months of spring (April and May). For the first law assessment, two energy indicators were utilized: the solar fraction (SF) and the thermal efficiency of the system (ηth). On days with distinctive weather conditions, both systems obtained approximately equal SF and ηth values, without a specific preference between the ambient conditions and the type of SWHS. Regarding a four-day nonstop operation, the FC overperformed the thermosyphon system at both energy indicators. Namely, for the FC and the thermosyphon SWHS, the SF was calculated to be 0.62 and 0.48, and the ηth was 68.2% and 53.3%, respectively.

This study presents a sophisticated numerical simulation model for a forced circulation solar water heating system (FC-SWHs), specifically designed for the unique climatic conditions of Algeria. The model aims to cater to the hot water needs of single-family houses, with a daily consumption of 246 L. Utilizing a dynamic approach based on TRNSYS modeling, the system’s performance in Ain Temouchent’s climate was scrutinized. The model’s validation was conducted against literature results for the collector outlet temperature. Key findings include a maximum monthly average outlet temperature of 38 °C in September and a peak cumulative useful energy gain of 250 W in August. The auxiliary heating system displayed seasonal energy consumption variations, with the highest rate of 500 kJ/hr in May to maintain the water temperature at 60 °C. The energy input at the storage tank’s inlet and the consistent high-level energy output at the hot water outlet were analyzed, with the former peaking at 500 W in May. The system ensured an average water tank temperature (hot, middle and bottom) and water temperature after the mixer, suitable for consumption, ranging between 55 °C and 57 °C. For applications requiring cooler water, the mixer’s exit temperature was maintained at 47 °C. The study’s key findings reveal that the TRNSYS model predicts equal inlet and outlet flow rates for the tank, a condition that is particularly significant when the system operates with high-temperature water, starting at 55 °C. The flow rate at this temperature is lower, at 7 kg/hr, while the water mass flow rate exiting the mixer is higher, at 10.5 kg/hr. In terms of thermal performance, the system’s solar fraction (SF) and thermal efficiency were evaluated. The results indicate that the lowest average SF of 54% occurs in July, while the highest average SF of over 84% is observed in September. Throughout the other months, the SF consistently stays above 60%. The thermal efficiency of the system varies, ranging from 49 to 73% in January, 43–62% in April, 48–66% in July, and 53–69% in October. The novelty of this research lies in its climate-specific design, which addresses Algeria’s solar heating needs and challenges. Major contributions include a thorough analysis of energy efficiency metrics, seasonal auxiliary heating demands, and optimal system operation for residential applications, supporting Algeria’s goal of sustainable energy independence.

Increasing surface temperature has a significant effect on the electrical performance of photovoltaic (PV) panels. A closed-loop forced circulation serpentine tube design of cooling water system was used in this study for effectively management of the surface temperature of PV panels. A real-time experiment was first carried out with a PV panel with a cooling system at heat transfer fluid (HTF) flow rates of 60 kg h −1 , 120 kg h −1 , and 180 kg h −1 . Based on the experimentation, a correlation for a nominal operating cell temperature (NOCT) and thermal efficiency for collector was developed for experimental validation of useful energy gained, cell temperature, and electric power generation. The developed correlations were validated with the use of electric power electrical power and useful energy gained in photovoltaic serpentine thermal solar collector (PV/STSC) and fitting into the experimental results with a deviation of 1% and 2.5% respectively. Further, with the help of developed correlations, a system was developed in the TRNSYS tool through which an optimization study was performed based on electric and hot water demand. The findings indicated an optimal system with an 8-m 2 PV/STSC area, a HTF flow rate of 60 kg h −1 , and thermal energy storage (TES) system having a volume and height of 280 l and 0.8 m could meet 91% and 33% of the hot water demand for Ac loads and 78% or DC loads, respectively.

In this paper, the production of low to medium temperature water for industrial process heat using solar energy is considered. In particular, the paper outlines the perspective of an optimum design method that takes into account all of the typical variables of the problem (solar irradiation, system architecture, design constraints, load type and distribution, and design and optimization criteria) and also considers the use of the fossil fuel backup system. The key element of the methodology is the definition of a synthetic combined energetic and economic utility function. This considers the attribution of an economic penalty to irreversibility in connection with the use of a fossil fuel backup. This function incorporates the share of the solar system production (solar fraction) as an optimum design variable. This paper shows how, using the proposed criteria, the optimal value of the solar fraction, defined as the share of operation of the solar system with respect to the whole energy demand, can be increased. Current practice considers values in the range between 40 and 60%. However, levels up to 80% can also be obtained with the proposed methodology. Thus, penalizing the use of fossil fuels does not exclude a priori their contribution.

This paper focused on the performance monitoring and modeling of a 6.0 kW, 2000 L hybrid direct expansion solar assisted heat pump (DX-SAHP) water heater used for the production of hot water in a university students’ accommodation with 123 females. The data of total electrical energy consumed, volume of hot water consumed, ambient temperature, relative humidity, and solar irradiance were obtained from the data acquisition systems and analyzed in conjunction with the energy factor (EF) of the system. A multiple linear regression model was developed to predict the EF. The EF of the hybrid DX-SAHP water heater was determined from the summation of the coefficient of performance (COP) of the heat pump unit and the solar fraction (SF) of the solar collectors. The operations of the hybrid energy system were analyzed based on three phases (first phase from 00:00–08:00, second phase from 08:30–18:30, and third phase from 19:00–23:30) over 24 h for the entire monitoring period. The average EF of the hybrid energy system per day during the second phase of operation was 4.38, while the SF and COP were 0.697 and 3.683, respectively. The developed multiple linear regression model for the hybrid DX-SAHP water heater accurately predicted the determined EF.

The main limitation of Integrated Collector Storage systems lies in their low efficiencies and high loss coefficients. In this paper, experimental and numerical setups are conducted to assess the thermal performances of low cost Cylindrical Parabolic Integrated Collector storage (CP-ICS). The conceived system has two aluminum plates in parabolic form serving as reflectors, each with a surface area of 2 m2. The storage tank has a volume of 160 L covered with a layer of black paint with single and double transparent insulations. Results of the experimental tests using Input-Output method showed that the daily thermal efficiency ηd of the developed systems is equal to 48.21% and 49.46% for single and double insulation cover configurations, respectively. The total store heat capacity Cs, the useful collector surface Ac* and the storage tank heat losses coefficient Us of the system found using Dynamic System Testing procedure are equal to 0.56 MJ/K, 0.74 m2 and 1.59 W/K, respectively. Even if the energy efficiency of the system is slightly lower than that recorded in conventional systems, numerical results of long-term study using TRNSYS software showed that the system provides a reasonable solar fraction for the needs of a family in Tunisian climate. A comparative assessment of the developed solar collector performances in different representative climates showed that the use of the CP-ICS system presents a promising solution for countries with annual ambient temperatures fluctuating from 13°C to 33°C, such as Araxos with a solar coverage of 30.65% for a daily supply volume of 160 L. More importantly, in Faya-Largeau location, presenting Chadian climate data, the solar fraction is found to be the highest and reached an average of 67.25%.