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The utilisation of renewable energy sources for generating electricity and potable water is one of the most sustainable approaches in the current scenario. Therefore, the current research aims to design and develop a novel co-generation system to address the electricity and potable water needs of rural areas.

The cogeneration system mainly consists of a solar parabolic dish concentrator (SPDC) system with a concentrated photo-voltaic module at the receiver for electricity generation. It is further integrated with a low-temperature thermal desalination (LTTD) system for generating potable water. Also, a novel corn cob filtration system is introduced for the pre-treatment to reduce the salt content in seawater before circulating it into the receiver of the SPDC system. The designed novel co-generation system has been numerically and experimentally tested to analyse the performance at Karaikal, U.T. of Puducherry, India.

Because of the pre-treatment with a corn cob, the scale formation in the pipes of the SPDC system is significantly reduced, which enhances the efficiency of the system. It is observed that the conductivity, pH and TDS of seawater are reduced significantly after the pre-treatment by the corncob filtration system. Also, the integrated system is capable of generating 6–8 litres of potable water per day.

The integration of the corncob filtration system reduced the scaling formation compared to the general circulation of water in the hoses. Also, the integrated SPDC and LTTD systems are comparatively economical to generate higher yields of clean water than solar stills.

This paper aims to present the numerical models and experimental outcomes pertain to the performance of the parabolic dish concentrator system with a modified cavity-type receiver (hemispherical-shaped).

The numerical models were evolved based on two types of boundary conditions; isothermal receiver surface and non-isothermal receiver surface. For validation of the numerical models with experimental results, three statistical terms were used: mean of absolute deviation, R² and root mean square error.

The thermal efficiency of the receiver values obtained using the numerical model with a non-isothermal receiver surface found agreeing well with experimental results. The numerical model with non-isothermal surface boundary condition exhibited more accurate results as compared to that with isothermal surface boundary condition. The receiver heat loss analysis based on the experimental outcomes is also carried out to estimate the contributions of various modes of heat transfer. The losses by radiation, convection and conduction contribute about 27.47%, 70.89% and 1.83%, in the total receiver loss, respectively.

An empirical correlation based on experimental data is also presented to anticipate the effect of studied parameters on the receiver collection efficiency. The anticipations may help to adopt the technology for practical use.

The developed models would help to design and anticipating the performance of the dish concentrator system with a modified cavity receiver that may be used for applications e.g. power generation, water heating, air-conditioning, solar cooking, solar drying, energy storage, etc.

The originality of this manuscript comprising presenting a differential-mathematical analysis/modeling of hemispherical shaped modified cavity receiver with non-uniform surface temperature boundary condition. It can estimate the variation of temperature of heat transfer fluid (water) along with the receiver height, by taking into account the receiver cavity losses by means of radiation and convection modes. The model also considers the radiative heat exchange among the internal ring-surface elements of the cavity.

This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver.

The coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction.

It is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss.

On-sun experimental tests need to be performed to validate the numerical study.

Numerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design.

Pressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source.

The present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.

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.

In this paper, the purpose of research is to verify good thermal performance of heat pipe receiver.

Mathematical model was set up, numerical calculation method was offered. Calculation results were compared with experimental results, with those of NASA project, and those of the basis heat receiver.

Simulation results show that heat pipe receiver involving heat pipe has the performance of perfect heat transfer and ideal identical temperature, the axial temperature difference of heat pipe is small, PCM canisters situated in different places of heat pipe can melt simultaneously and uniformly. At the same time, normal operation of wick ensures the uniformity of heat pipe circumference temperature, thus heat pipe receiver avoids phenomena of thermal spot. In addition, heat pipe receiver has axial and radial performance of ideal identical temperature, all PCM canisters can freeze simultaneously at the end of eclipse periods, and freeze fully at last, so heat pipe receiver avoids thermal ratcheting.

The research in this paper can be used to design heat pipe receiver.

The purpose of this paper is to present the numerical solutions of surface radiation and combined natural convection heat transfer in a solar cavity receiver. The paper aims to discuss sundry issues that take place in the said model.

The numerical solutions are developed by means of second-order upwind scheme using the SIMPLE algorithm.

The effects of physical factors such as Rayleigh number (10⁴ ≤ Ra ≤ 10⁶), inclination angels of insulated walls (0º ≤ θ ≤ 10º) and the wall surface emissivity (0 ≤ ε ≤ 1) on natural convection-surface radiation heat transfer rate are analyzed. Impact of sundry parameters on flow quantities are discussed and displayed via graphs and tables. Stream lines and isothermal lines have also been drawn in the region of cavity. The numerical results reveal that increasing the Rayleigh number, wall surface emissivity and inclination angels of insulated walls in an open cavity enhances the mean total Nusselt number. The variations of the surface radiation and natural convection heat transfer mean Nusselt numbers are very small to the inclination angle of θ, while a significant change is noted for the case of Rayleigh number and emissivity.

To the best of authors’ knowledge, this model is reported for the first time.

Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress.

The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events.

The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions.

Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

The purpose of this paper is to investigate a cylindrical flow insert for a parabolic trough solar collector. Centrally placed and eccentric placed inserts are investigated in a systematic way to determine which configuration leads to the maximum thermal enhancement.

The analysis is performed in SolidWorks Flow Simulation with a validated computational fluid dynamics model. Moreover, the useful heat production and the pumping work demand increase are evaluated using the exergy and the overall efficiency criteria. The different scenarios are compared for inlet temperature of 600 K, flow rate of 100 L/min and Syltherm 800 as the working fluid. Moreover, the inlet temperature is examined from 450 to 650 K, and the diameter of the insert is investigated up to 50 mm.

According to the final results, the use of a cylindrical insert of 30 mm diameter is the most sustainable choice which leads to 0.56 per cent thermal efficiency enhancement. This insert was examined in various eccentric positions, and it is found that the optimum location is 10 mm over the initial position in the vertical direction. The thermal enhancement, in this case, is about 0.69 per cent. The pumping work demand was increased about three times with the insert of 30 mm, but the absolute values of this parameter are too low compared to the useful heat production. So, it is proved that the increase in the pumping work is not able to eliminate the useful heat production increase. Moreover, the thermal enhancement is found to be greater at higher temperature levels and can reach up to 1 per cent for an inlet temperature of r650 K.

The present work is a systematic investigation of the cylindrical flow insert in a parabolic trough collector. Different diameters of this insert, as well as different positions in two dimensions, are examined using a parametrization of angle-radius. To the authors’ knowledge, there is no other study in the literature that investigates the presented many cases systematically with the followed methodology on parabolic trough collectors. Moreover, the results of this work are evaluated with various criteria (thermal, exergy and overall efficiency), something which is not found in the literature.

A mixed metal oxide-based spinel ceramic pigment has been successfully synthesized incorporating inorganic, high-temperature stable furnace cement as an inbuilt binder. Step by step synthesis was done for the spinel and cement mix formulations.

The pigment mix was synthesized by a solid-solid method where the inorganic binder was incorporated in the mix. The results suggested that CoCuMn-based spinel ceramic pigment with cement mix could be obtained at an annealing temperature of 1,100ºC for 1 h and the size, morphology and crystallinity of spinel mix were greatly influenced by the calcination temperature.

The pigment mix synthesized was applied as a coating to different substrates such as aluminum, glass and Mild steel. The results revealed that spectral selectivity of TSSS paint coatings based on the CoMnCu spinel ceramic mix was much better than that of solvent-based coatings for high-temperature applications. The presence of cement as an inorganic binder makes the functioning and application of paint easy as it becomes that of a waterborne type.

Ease of application, stability at high temperatures, best absorptivity at the solar selective spectrum and excellent adhesion properties for the selected surface are the key features of the designed pigment system. The applied pigment mix was studied as a coating to get the results for solar selective system.

Gas‐cooled solar heat exchanger units (panels) are envisaged for installation in solar tower power plants. The thermal stresses arising in the panel in solar operation are high and are in part unique, so that design and development of this hot component has to rely on experimental studies. The present paper describes experimental studies done on a panel. For the tests a 3 MW hot‐gas test facility built primarily for the testing of hot components is used. Solar operating conditions are simulated on a panel prototype and the resulting thermal loads measured on critical panel components. Planning and optimizing of the test program as well as the evaluation of test results have been supported with finite element computing. The test results presented here show what stresses are exerted on the components by the solar‐specific operating conditions. Moreover, it is shown how rapidly changing unsteady thermal loads at high temperatures can be precisely detected and evaluated. In combination with efficient modern methods of calculation (e.g. finite element analysis) these results can be also be used to solve similar problems on other hot components.