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One of the existing and commonly used solar energy harvesting devices is the parabolic trough solar collector (PTSC). Because of their ability to operate in low and medium temperatures, parabolic trough concentrators are widely used in power generation plants and industrial process heating applications. Therefore, the investigation of how different operating conditions affect these devices’ overall efficiency has received a great deal of attention in the recent decade. This study aims to enhance the thermal performance of the PTSC and reduce the system cost.

In the novel configuration, a noncirculated nanofluid absorbs solar radiation through a glass wall. The base fluid was synthetic oil (5W30), and the nanoparticles used were copper oxide. The heat captured is immediately absorbed by the water circulating inside the copper tube immersed in the nanofluid. ANSYS FLUENT 15.0 was used for carrying out computational fluid dynamics simulations for two models of single and triple copper tubes. The experimental results obtained from a test rig constructed for this purpose were compared with the numerical outcomes of the single copper tube model.

The findings of the simulation demonstrated that performance was superior for the single copper tube model over the triple copper tube model. The numerical findings of the single copper tube model were compared with the experimental results. The numerical and experimental results differed from 3.17% to 5.6%. Investigations were carried out to study the effects of varying the volumetric flow rate of (20, 40, 60 and 80 L/h) and water inlet temperatures of (300, 315 and 330 K) on the effectiveness and performance of the newly developed model. Additionally, two nanofluid volume fractions of 0.05% and 0.075% were used for investigating their effect on the performance of the novel configuration. According to the findings, the highest thermal efficiency of 55.31% was recorded at 0.075% concentration and 80 L/h volume flow rate.

In this study, a novel direct absorption solar collector configuration using a noncirculated nanofluid was designed to enhance the thermal efficiency of PTSC. This new approach makes it possible to boost the thermal performance of the PTSC and lower the system’s cost.

Because of its increased absorptance in fluid and reduced heat loss, direct absorption nanofluid (DANF) is receiving intense interest as an efficient way to harvest solar energy. This work aims to investigate, for the first time, the application of DANF in parabolic trough collectors (PTC), a promising collector for solar thermal systems.

A representative flow and heat transfer study of different fluids in a straight tube is conducted, and the basic energy equation and radiative transfer equations are numerically solved to obtain the fluid temperature distribution and energy conversion efficiency. Ethylene glycol (EG) and different concentrations of (i.e., 0.1-0.6 per cent) multi-wall carbon nanotubes (MWCNT) in EG are used as sample fluids. Four cases are studied for a traditional PTC (i.e., using metal tube) and a direct absorption PTC (i.e., using transparent tube) including a bare tube, a tube with an air-filled glass envelope and a tube with vacuumed glass envelop. The numerical results are verified by an experimental study using a copper-glass absorber tube, which reveals the good potential of DANFs.

Compared with a conventional PTC, using DANF shows an increase of 8.6 per cent and 6.5 K, respectively, in thermal efficiency and outlet temperature difference at a volume fraction (0.5 per cent) of nanoparticles. The results also show that the improvement in solar efficiency increases with increasing particle concentrations, and the vacuum insulated case has the highest efficiency.

In all previous studies, an important section was missing as the effect of photons on the direct solar absorption trough collector, which is considered in this study. This paper proposes a new concept of using direct solar absorption nanofluids for concentrated solar collectors and analyzes the performance of both absorptance and transmittance efficiency considerations. To reveal the potential of the new concept, an analytical model based on energy balance is developed, and two case studies are performed.

Effective cooling is one of the challenges for photovoltaic thermal (PVT) systems to maintain the PV operating temperature. One of the best ways to enhance rate of heat transfer of the PVT system is using advanced working fluids such as nanofluids. The purpose of this research is to develop a numerical model for designing different form of thermal collector systems with different materials. It is concluded that PVT system operated by nanofluid is more effective than water-based PVT system.

In this research, a three-dimensional numerical model of PVT with new baffle-based thermal collector system has been developed and solved using finite element method-based COMSOL Multyphysics software. Water-based different nanofluids (Ag, Cu, Al, etc.), various solid volume fractions up to 3 per cent and variation of inlet temperature (20-40°C) have been applied to obtain high thermal efficiency of this system.

The numerical results show that increasing solid volume fraction increases the thermal performance of PVT system operated by nanofluids, and optimum solid concentration is 2 per cent. The thermal efficiency is enhanced approximately by 7.49, 7.08 and 4.97 per cent for PVT system operated by water/Ag, water/Cu and water/Al nanofluids, respectively, compared to water. The extracted thermal energy from the PVT system decreases by 53.13, 52.69, 42.37 and 38.99 W for water, water/Al, water/Cu and water/Ag nanofluids, respectively, due to each 1°C increase in inlet temperature. The heat transfer rate from heat exchanger to cooling fluid enhances by about 18.43, 27.45 and 31.37 per cent for the PVT system operated by water/Al, water/Cu, water/Ag, respectively, compared to water.

This study is original and is not being considered for publication elsewhere. This is also not currently under review with any other journal.

This study has covered many types of solar-powered air-conditioning systems that may be used as an alternative to traditional electrically powered air-conditioning systems in order to reduce energy usage. Solar adsorption air cooling is a great alternative to traditional vapor compression air-conditioning. Solar adsorption has several advantages over traditional vapor-compression systems, including being a green cooling technology which uses solar energy to drive the cycle, using pure water as an eco-friendly HFC-free refrigerant, and being mechanically simple with only the magnetic valves as moving parts. Several advancements and breakthroughs have been developed in the area of solar adsorption air-conditioners during the previous decade. However, further study is required before this technology can be put into practise. As a result, this book chapter highlights current research that adds to the understanding of solar adsorption air-conditioning technologies, with a focus on practical research. These systems have the potential to become the next iteration of air-conditioning systems, with the benefit of lowering energy usage while using plentiful solar energy supplies to supply the cooling demand.

In the twenty-first century, the use of fossil fuels has increased drastically because the necessity of energy is increasing day by day which affects the world’s economy. The solar energy (photo-thermal energy conversion) system is the most economical and eco-friendly alternative source. To increase the use of domestic as well as commercialization purpose, the authors have reviewed this paper on the solar water heater along with its structural mechanism for energy enhancement and to create easier stair steps for climbing on the green world dream.

In this study, nanotechnology has remarkably built its own use for extending thermal efficiency by using some gradual experiments. It is a phenomenon, like nanofluid (as a working fluid for a direct solar collector), nanocoating (on the surface of a solar-evacuated tube by using the chemical vapor deposition/physical vacuum deposition/sol–gel technique) and nanorod-based solar collector tube.

This invention gives greater efficiency rather than the conventional systems, but also this advancement is not too much supported in a low- temperature environment also, we can consider the poor light absorption characteristics of the pure water (Bencic, et al., 2000).

The basic idea and understanding of this phenomenon to improve solar collecting performance for obtaining a high working-fluid temperature are discussed in this paper.

Integrated solar combined cycle (ISCC) using parabolic trough collector (PTC) technology is a new power plant that has been installed in few countries to benefit from the use of hybrid solar-gas systems. The purpose of this paper is to investigate the challenges in modeling the thermal output of the hybrid solar-gas power plant and to analyze the factors that influence them.

To validate the proposal, a study was conducted on a test stand in situ and based on the statistical analysis of meteorological data of the year 2017. Such data have been brought from Abener hybrid solar-gas central of Hassi R’mel and used as an input of our model.

The proposal made by the authors has been simulated using MATLAB environment. The simulation results show that the net solar electricity reaches 18 per cent in June, 15 per cent in March and September, while it cannot exceed 8 per cent in December. Moreover, it shows that the power plant responses sensibly to solar energy, where the electricity output increases accordingly to the solar radiation increase. This increase in efficiency results in better economic utilization of the solar PTC equipment in such kind of hybrid solar-gas power plant.

The obtained results would be expected to provide the possibility for designing other power plants in Algeria when such conditions are met (high DNI, low wind speed, water and natural-gas availability).

This paper presents a new model able to predict the thermal solar energy and the net solar-electricity efficiency of such kind solar hybrid power plant.

The purpose of this study is to examine the energy savings in the indoor environment, using strategies that adopt the characteristics of nature, called biomimetic solutions. This research designed a biomimetic window system to bring daylight into interior spaces in educational buildings where daylight cannot be reached. Specifically, this study assessed how the daylight that was achieved via a biomimetic window system would affect energy savings using an energy simulation method.

This study explored how biomimetic methods would affect the building environment and which biomimetic method would involve the building's energy saving with daylight. The research intended to develop a novel biomimetic window system that can bring daylight to the basement floor of an existing building on a university campus to find out how much the biomimetic window system would affect the energy savings of the building. Referring to the existing building's layout and structure, energy simulation models were developed, and the energy consumptions were estimated.

Simulation models proved that the biomimetic window system has sufficient performance to bring more daylight to the basement floor of the building. Furthermore, it was confirmed that the use of the biomimetic window system for the building could reduce energy usage compared to the actual energy usage of the current building without biomimetic windows.

First, this study was adopted as a computer-designed simulation method instead of using a real-world system. Although this study designed the biomimetic window system based on previous studies, it should be considered the possibility of other problems when the system is actually built in. Second, it is necessary to predict how much an initial budget is required when the system is built. It means that this study did not calculate the lifecycle cost of the biomimetic window system. It will also be necessary to compare energy consumption to the required initial budget. Lastly, this study was simulated based on weather data in cold regions, and it did not compare/analyze different climate regions. Different results may be predicted if the biomimetic window system is built in different climatic regions.

This research showed new practical ways to capture and transmit solar heat and light using a biomimetic solution. Furthermore, using the proposed novel biomimetic window system, the amount of energy reduction can be calculated, and this method could be applied in the interior non-window spaces of academic and related types of buildings.

Solar selective coatings are designed and formulated for effective collection and retention of solar energy. Several types of coatings can be utilized for economical collection of solar energy, the most common and simplest will be ordinary non‐glass, heat resistant black paint. The coatings may be moderately selective or non‐selective absorbers, consisting of organic or inorganic matt black paints. These are easiest to apply and the least expensive of all collector coatings. In this category other types are ceramic and organic enamels and chemical or electrochemical metal conversion coatings. An impending energy crisis has already aroused interest and scientific pursuit in the field. An analysis of the state‐of‐the‐art in solar selective coatings was felt necessary at this time.

This paper aims to present experimental work examining the effect of opening size on the collection efficiency of cavity-type receiver geometries, e.g. modified cavity and spherical cavity with single- as well as dual-stage water heating. The correlations, obtained using the experimentally obtained data, are helpful in designing of cavity receivers (modified and spherical geometry type) to be used in solar-power harnessing assignments/projects, for yielding better system performance.

The parameters of study encompass receiver opening or aperture ratios (d/D, ratio of diameter of opening to the maximum diameter of spherical cavity) of 0.4, 0.47, 0.533 and 0.6; flow Reynolds numbers of 938, 1,175, 1,525 and 1,880 with water as a coolant; and receiver inclination angles of 90, 60, 45 and 30° (with 90° as receiver-opening facing downward and 30° as receiver-aperture facing closer to sideway). A modified cavity receiver was examined for opening ratios of 0.46, 0.6, 0.7 and 0.93. The glass covers, with thickness 2, 4 and 6 mm, were positioned at the opening of cavity to mitigate the energy losses.

The experiments have been conducted at a lesser incoming radiative heat flux, for receiver cavity wall surface temperatures ranging from 90°C to 180°C. The collection efficiency values of both the receivers, modified cavity and spherical cavity types, are seen increasing with coolant flow rate and receiver tilt (inclination) angles, i.e. 30° → 90°. The collection efficiency exhibits maxima at an opening ratio of 0.533 in case of both single- and double-stage spherical cavity receiver. This value was observed as 0.6 for modified cavity receiver. The mathematical correlations developed for obtaining the collection efficiency values of modified cavity-type receiver, spherical cavity receiver with single stage and spherical cavity receiver with dual-stage water heating are given as ɳ=0.4667 Re0.0798dD0.1651 δ0.0281θ̇−0.011, ɳ=0.2317 Re0.124 dD1.265δ0.0192θ̇0.2914 and ɳ=0.1137 Re0.1715dD0.8702θ̇0.2757, respectively.

The findings of the paper may be helpful in erecting concentrating solar collector systems for household water heating, concentrating solar-based power generation as well as for various agricultural applications.

The experimental investigations are fewer in the literature examining the combined geometrical influence on the efficiency of cavity receivers with single- and double-stage water heating provisions.

Present investigation conducts a study on the hydrothermal features of a double flow Parabolic Trough Solar Collector (PTSC) equipped with sinusoidal-wavy grooved absorber tube and twisted tape insert filled with nanofluid. This paper aims to present an effectual PTSC which is comprised by nanofluid numerically by means of finite volume method.

The beneficial results such as pressure drop inside the absorber tube, mean predicted friction factor, predicted average Nusselt number and hydrothermal Performance Evaluation Criteria (PEC) are evaluated and reported to present the influences of numerous factors on studied interest outcomes. Effects of different Reynolds numbers and environmental conditions are also determined in this investigation.

It is found that using the absorber roof (canopy) can enhance the heat transfer ratio of PTSCs significantly during all studied Reynolds numbers. Also, it is realized that the combination of inner grooved surface, outer corrugated surface and inserting turbulator can improve the thermal-hydraulic characteristics of PTSCs sharply.

Novel PTSC (N.PTSC) filling with two Heat Transfer Fluids (HTFs), inner and outer surface corrugated absorber tube, absorber roof and inserting twisted tape (N.PTSC.f) has the highest PEC values among all novel configurations along all investigated Reynolds numbers which is followed by configurations N.PTSC with two HTFs and inserting twisted tape (N.PTSC.e), N.PTSC with two HTFs and outer surface corrugated absorber tube (N.PTSC.b) and N.PTSC with two HTFs and inner surface corrugated absorber tube (N.PTSC.c), respectively. N.PTSC.f Nusselt number values can overcome the high values of friction factor, and therefore is introduced as the most efficient model in the current study.