In this study, a small scale hybrid solar heating, chilling and power generation system, including parabolic trough solar collector with cavity receiver, a helical screw expander and silica gel–water ...adsorption chiller, etc., was proposed and extensively investigated. The system has the merits of effecting the power generation cycle at lower temperature level with solar energy more efficiently and can provide both thermal energy and power for remote off-grid regions. A case study was carried out to evaluate an annual energy and exergy efficiency of the system under the climate of northwestern region of China. It is found that both the main energy and exergy loss take place at the parabolic trough collector, amount to 36.2% and 70.4%, respectively. Also found is that the studied system can have a higher solar energy conversion efficiency than the conventional solar thermal power generation system alone. The energy efficiency can be increased to 58.0% from 10.2%, and the exergy efficiency can be increased to 15.2% from 12.5%. Moreover, the economical analysis in terms of cost and payback period (PP) has been carried out. The study reveals that the proposed system the PP of the proposed system is about 18 years under present energy price conditions. The sensitivity analysis shows that if the interest rate decreases to 3% or energy price increase by 50%, PP will be less than 10 years.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•A MXene nanofluid is proposed for solar absorption for the first time.•The optical properties of MXene nanofluid are experimentally characterized.•A numerical model is developed to investigate the ...performance of MXene nanofluid.•A maximum photothermal conversion efficiency 77.49% is achieved with merely 100 ppm MXene loading.
A newly direct absorption solar collector (DASC) based on MXene nanofluid is proposed herein. The excellent optical properties of MXene nanofluids are experimentally determined, and a three-dimensional steady-state numerical model is developed to investigate the synergistic effect of the optical properties of MXene nanofluids and the structural parameters of the DASC. The effects of volume flow rate, working temperature, and solar concentration ratio on the photothermal conversion performance of the DASC are also analyzed. The results show that the transmittance of the MXene nanofluid evidently decreases because of the enhanced absorption of solar radiation of MXene. With the addition of MXene, the photothermal conversion efficiency of the nanofluid rapidly increases and then slightly decreases. The optimal MXene mass fraction is inversely proportional to the collector height. A mere 100 ppm of MXene nanofluid can achieve a maximum intercept efficiency of 77.49%, which is 55.47% higher than that of the base fluid. This work demonstrates the potential for the application of MXene nanofluids in the utilization of solar energy.
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IMTLJ, KILJ, KISLJ, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
•Integrated evacuated solar collector with solar still increased the productivity.•The ultrasonic humidifier was used as effectiveness method for water vaporization.•Using phase change materials ...increased the productivity after the sun set.•Cost analysis was explained and considered for the conventional solar still.•The maximum productivity for the system reached 7.4 kg/m2 for 35 mm water depth.
Desalination of brackish and sea water with renewable energy source is an important economical solution for obtaining potable water. There are different techniques were used to improve the solar still productivity. So, this research deals with improving the solar still productivity by using ultrasonic waves, reflectors and phase change material. A single solar still was designed, fabricated and tested under the climate conditions of Alexandria, Egypt. The solar still has base dimensions of 1 m × 1 m and integrated with an evacuated solar collector of 200 l capacity. Six ultrasonic humidifiers were installed to strengthen the evaporation frequency of the water basin. A photovoltaic solar panel of 280 W was used to provide the power for ultrasonic humidifiers. An evacuated solar collector was used to provide solar still with hot sprayed water inside the solar still after 13:00 local time. Experimental tests have constructed to powerfully assess the daily productivity of fresh water during the three summer months under the same climate conditions. Four cases were studied to investigate the daily fresh water productivity at different embedded components with the solar still: phase change material; ultrasonic humidifiers and phase change material; evacuated solar collector and phase change material and the forth case is phase change material and ultrasonic humidifiers combined with evacuated solar collector. The results showed that the maximum daily productivity are 5.34 and 7.4 kg per day for 25 and 35 mm water depths respectively in case of using solar still with phase change material and ultrasonic humidifiers integrated with an evacuated solar still. The ultrasonic humidifier was influential in case of integrating evacuated solar collector and improved the daily productivity by 25 and 44% at water depths of 25 and 35 mm respectively.
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IMTLJ, KILJ, KISLJ, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
•Carbon black-ethylene glycol (CB-EG) nanofluids were investigated.•Extinction coefficient increased linearly with CB concentration within 450–820 nm.•An enhancement of overall photo-thermal ...efficiency of 27.43% was obtained.•Local photo-thermal efficiency improves with concentration and depth of fluid.
Direct absorption solar collector (DASC) is a promising method of harvesting solar energy. Present work considers carbon black-ethylene glycol (CB-EG) based nanofluids as the working fluids for DASC applications. Nanofluids were synthesized by the two-step method. Various studies carried out in this work include long time homogeneity, energy absorption characteristic and transient temperature profiles as functions of fluid thickness, light exposure time and concentration of the nanoparticles. Improved absorption characteristics, compared with those of the base fluid, towards incident irradiance were observed in all cases. About 27.90% increment in overall photo-thermal conversion efficiency over that of the ethylene glycol (EG) alone is observed for the case of 15 ppm carbon black (CB) concentration with an exposure time of 1200 s. Measured data show increasing trends in local photo-thermal efficiency with the thickness of the liquid layer as well as with the concentration of the suspended nanoparticles. These studies confirm that CB-EG based nanofluids can be used as potential working fluids for DASCs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Using thermal energy balance, this paper analyzes and investigates the thermal performance of a U-tube solar collector whose temperature thermal energy is high due to solar radiation. A working fluid ...of 20% PG (propylene glycol)–water is used. Solar collector efficiency was calculated and energy savings predicted for various nanofluids, such as MWCNT, Al2O3, CuO, SiO2, and TiO2. As a result, thermal conductivity increased as the concentration of nanofluid increased. Solar collector efficiency increased in the following order from greatest to least: MWCNT, CuO, Al2O3, TiO2, and SiO2 nanofluids. When the thermal loss value ((Ti−Ta)/G) was equal to 0, the solar collector using 0.2vol% MWCNT nanofluid showed the greatest efficiency (62.8%, a 10.5% improvement compared to 20% PG–water). By dispersing nanoparticles in the working fluid, the coal usage could be further reduced by approximately 39.5–131.3 kg per year when 50 solar collectors are used. Therefore, CO2 generation could be reduced by 103.8–345.3 kg and SO2 generation by 0.4–1.1 kg per year, compared to solar collectors using a base working fluid of 20% PG–water. These findings contribute to knowledge of solar energy technology, which has the potential to reduce electricity and energy consumption world-wide.
•Thermal performance of an U-tube type solar collector was analyzed theoretically.•MWCNT, Al2O3, CuO, SiO2, and TiO2 nanofluid with 20% PG-water were applied.•Solar collector using 0.2vol%-MWCNT nanofluid showed the highest efficiency.•By using nanofluids, the coal usage can be further reduced by 131.3–39.5 kg for one year when the 50 solar collectors are used.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•The use of thermoelectric generator for a solar and geothermal based energy system.•Hourly analysis of the system for four different days a year to observe the system.•Applying an optimization to ...determine the optimal design parameters.•To propose a system to produce electricity and fresh water with better efficiency.
In this research paper, an integrated energy system for the production of cooling, hot water, and electricity along with desalinated water is proposed, simulated, assessed, and optimized. This integrated energy system is composed of a geothermal well, a single-effect Li/Br and water absorption chiller, parabolic trough collectors (PTCs), a steam Rankine cycle (SRC) and, a reverse osmosis desalination unit. Instead of the condenser, thermoelectric generators (TEGs) are used to increase the generated electricity by the SRC. The system's performance is evaluated in terms of energy, exergy, and exergoeconomic, and the cases with the TEG is compared to the system with the condenser, and results are discussed and investigated. Using the TEG instead of a condenser, results in reducing the total cost rate and enhancing the system's exergy efficiency. Also, the performance of the system was evaluated for four different days in Shiraz city. For the selected days in spring, summer, fall, and winter, the highest generated electricity of the system with the thermoelectric generator is 1087 kW, 1158 kW, 1133 kW, and 766.5 kW, respectively. Thus, the system with thermoelectric is selected for optimization. To optimize the system, seven decision variables are selected namel, the geothermal fluid temperature, the total solar aperture area, the collector outlet temperature, the inlet pressure of the turbines, the TEG figure of merit, the turbine outlet pressure, and the evaporator pinch point temperature difference. Total cost rate and system exergy efficiency are considered as two objective functions. To determine optimum values of the objective functions, a multi-objective genetic algorithm is applied, and also the Pareto frontier figure is obtained. In this figure, the best point is chosen from the technique for order of preference by similarity to ideal solution (TOPSIS) decision-making criterion, where the cost rate is 10.41 ($ / GJ), and the exergy efficiency is 20.52%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Novel district heating system with photovoltaic/thermal collector and geothermal heat pump.•Sustainability evaluation model with energy, environment, economic and social indicators.•Comprehensive ...parametric system analysis with 11 indicators and weight factors.•The ideal solar subsystem is a photovoltaic/thermal collector with 100% photovoltaic coverage ratio.
District heating systems assisted by renewable energy harness local energy sources, save fossil fuels, and reduce greenhouse gas emissions. Here, geothermal and solar resources are integrated into district heating through a geothermal heat pump and an absorption heat pump by employing vapor-compressor and absorption cycles, respectively. A quantitative sustainability assessment model was constructed for the resulting hybrid district heating systems. Indicators on energy, environment, economic, and societal aspects were used to evaluate the composite sustainability index of hybrid systems with information entropy method. The results demonstrate that a district heating system coupled to compound parabolic concentrator-photovoltaic/thermal solar collector system with 100% photovoltaic coverage ratio is the ideal system for the case study when the annual cost saving ratio is given the highest impact in the composite sustainability index. A detailed analysis on the annual cost saving ratio shows that a higher ambient temperature, solar beam irradiance and grid electricity price would have a positive impact on the annual cost saving ratio. It can be concluded that the quantitative sustainability evaluation approach proposed helps to select the ideal hybrid system.
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IMTLJ, KILJ, KISLJ, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZRSKP
Direct absorption using a nanofluid is an efficient way of harnessing solar energy. Present works aim to investigate hexagonal boron nitride-ethylene glycol (BN-EG) nanofluids and BN mixed with ...carbon black (CB) in EG (BN/CB-EG) hybrid nanofluids for applications in direct absorption solar collectors (DASCs). Nanofluids were prepared by using the two-step method. Stability and homogeneity were inspected photographically after storage of one month. The optical properties of the nanofluids were measured and computed under varying concentration mixing ratios (CMRs). An absorbed energy fraction of 98.92% was obtained in a 2.0 cm height of 90 ppm/15 ppm BN/CB nanofluid. Photo-thermal conversion performances of the nanofluids were investigated using a small in-house built experimental collector. Temperature-rises in the working fluids were measured under varying durations of exposure to a fixed irradiance, fluid height, and CMRs of the nanoparticles. An enhancement of 34.55% photo-thermal conversion efficiency over that of EG alone was obtained in the 90 ppm/15 ppm BN/CB nanofluid after 1200 s exposure to 437 W/m2 incident irradiance. Some basic approaches for designing a DASC in an optimized manner are also discussed. It is concluded that BN/CB-EG hybrid nanofluids can be the prospective working fluids in DASCs.
•Optical and photo-thermal conversion characteristics were experimentally studied•Absorbed energy fraction of 90 ppm BN-EG is 38.75 times of that of EG•Energy storage efficiency increases by 16.23% using 90 ppm BN-EG nanofluid•Using 20 mm 90 ppm/15 ppm BN/CB-EG nanofluid 98.92% energy is absorbed•Energy storage efficiency increases by 34.55% using 90 ppm/15 ppm BN/CB-EG
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In this study, a new microencapsulated phase change material, paraffin@titania (TiO2)/graphene oxide (GO), was prepared by in-situ hydrolysis and polycondensation of tetrabutyl titanate and the ...modification of GO on the TiO2 shell. The paraffin@TiO2/GO composite consisted of spherical particles with the diameters of 2–5 µm. Raman spectra analysis confirmed the compound of GO with the TiO2 shell. The melting temperature and latent heat of the paraffin@TiO2/GO composite were 60.04 °C and 74.99 J g−1, respectively, in which the encapsulation efficiency of paraffin was calculated to be 37.93%. It was noteworthy that the paraffin@TiO2/GO composite displayed better thermal stability than paraffin due to the shell material. Most of all, the novel heat transfer slurry prepared by dispersing the paraffin@TiO2/GO composite into water exhibited higher thermal conductivity, specific heat and light absorption properties along with outstanding photo-thermal conversion performance. The prepared paraffin@TiO2/GO composite with high heat storage capability and excellent photo-thermal conversion performance enable it to be a promising candidate in direct absorption solar collector for solar energy storage.
•We designed and synthesized the paraffin@TiO2/GO microcapsules.•The paraffin@TiO2/GO composite has good thermal storage capacility.•The paraffin@TiO2/GO slurry exhibits enhanced thermophysical properties.•The paraffin@TiO2/GO slurry has excellent photo-thermal performance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The main idea of this investigation is to increase the thermal efficiency of a flat plate closed-loop pulsating heat pipe solar collector by introducing a novel closed-loop pulsating heat pipe ...(CLPHP) with a dual-diameter structure. The CLPHP with dual-diameter configuration is made of copper with two diameters; larger in the condensation section (inner diameter of 3.5 mm) and smaller in the evaporation and adiabatic sections (inner diameter of 2 mm). The thermal performance of this type of CLPHP was investigated at different filling ratios and inclination angles. Results showed that the thermal performance of the dual-diameter configuration is considerably better than the single-diameter in the vertical and non-vertical orientations. Moreover, in this study, the performance of a flat plate solar collector coupled with the proposed dual-diameter CLPHP (DD-CLPHPSC) is investigated experimentally in outdoor and indoor modes during July and August of 2020, under local weather conditions of Mashhad, Iran. The effects of the filling ratio, inclination angle, and solar intensity were assessed. Under sunny weather conditions, when the direct normal irradiance was 1030 W/m2, the thermal efficiency of the DD-CLPHPSC with a filling ratio of 60% reached 72.4%.
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•Performance of CLPHP using a novel dual-diameter structure is enhanced.•A flat plate solar collector with inserted dual-diameter CLPHP is fabricated.•The effect of filling ratio, inclination angle and solar intensity is investigated.•Maximum 72.4% efficiency of the solar collector has been achieved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
