Central Receiver Research Articles

Olfaction-Inspired MCs: Molecule Mixture Shift Keying and Cross-Reactive Receptor Arrays

In this paper, we propose a novel concept for engineered molecular communication (MC) systems inspired by animal olfaction. We focus on a multi-user scenario where several transmitters wish to communicate with a central receiver. We assume that each transmitter employs a unique mixture of different types of signaling molecules to represent its message and the receiver is equipped with an array comprising <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> different types of receptors in order to detect the emitted molecule mixtures. The design of an MC system based on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">orthogonal</i> molecule-receptor pairs implies that the hardware complexity of the receiver linearly scales with the number of signaling molecule types <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> (i.e., <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R = Q</i> ). Natural olfaction systems avoid such high complexity by employing arrays of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cross-reactive</i> receptors, where each type of molecule activates multiple types of receptors and each type of receptor is predominantly activated by multiple types of molecules albeit with different activation strengths. For instance, the human olfactory system is believed to discriminate several thousands of chemicals using only a few hundred receptor types, i.e., <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Q</i> ≫ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> . Motivated by this observation, we first develop an end-to-end MC channel model that accounts for the key properties of olfaction. Subsequently, we present the proposed transmitter and receiver designs. In particular, given a set of signaling molecules, we develop algorithms that allocate molecules to different transmitters and optimize the mixture alphabet for communication. Moreover, we formulate the molecule mixture recovery as a convex compressive sensing problem which can be efficiently solved via available numerical solvers. Finally, we present a comprehensive set of simulation results to evaluate the performance of the proposed MC designs revealing interesting insights regarding the design parameters. For instance, we show that mixtures comprising few types of molecules are best suited for communication since they can be more reliably detected by the cross-reactive array than one type of molecule or mixtures of many molecule types.

A Model Predictive Control Approach for Heliostat Field Power Regulatory Aiming Strategy under Varying Cloud Shadowing Conditions

Weather conditions have significant impacts on the solar concentration processes of the heliostat fields in solar tower power plants. The cloud shadow movements may cause varying solar irradiance levels received by each heliostat. Hence, fixed aiming strategies may not be able to guarantee the solar concentrating performance. Dynamic aiming strategies are able to optimize the aiming strategy based on real-time shadowing conditions and short-term forecast, and, therefore, provide much more robust solar concentration performance compared to fixed strategies. In this work, a model predictive control approach for s heliostat field power regulatory aiming strategy was proposed to regulate the total concentrated solar flux on the central receiver. The model predictive control method obtains the aiming strategy, leveraging real-time and forecast shadowing conditions based on the solar concentration model of the heliostat field. The allowable flux density of the receiver and the aiming angle adjustment limits are also considered as soft and hard constraints in the aiming strategy optimization. A Noor III-like heliostat field sector was studied with a range of shadow-passing scenarios, and the results demonstrated the effectiveness of the proposed method.

Performance investigation of seawater desalination system powered by central receiver concentrated solar thermal plant

Seawater desalination using solar energy is a promising solution for addressing water scarcity in arid and semi- arid regions, as it not only provides a reliable source of fresh water, but also utilizes the abundant solar energy resources in the region to power the desalination process in a sustainable way. For this, the aim of this research is to investigate the performance and economic feasibility of a concentrated solar power plant coupled with a desalination unit for sustainable electricity and freshwater production. Six different coastal sites throughout the Middle East and North Africa region were considered, i.e., Agadir (Morocco), Algiers (Algeria), Sharm el-Sheikh (Egypt), Dammam (Saudi Arabia), Salalah (Oman), and Aden (Yemen). The concentrated solar power facility has a 100 MWe net output with two tanks of direct thermal energy storage using wet cooling with seawater as the cooling agent in the condenser; the solar tower model was validated using the Gemasolar power facility in Spain; and the desalination process include a direct-contact membrane distillation (DCMD) system numerically solved using the MATLAB software®, with experimental data used to validate the model. The findings indicate that large-scale central receiver concentrated solar thermal facilities are more competitive in Sharm el-Sheikh, where annual energy output and capacity factor are expected to be 586.28GWh and 67%, respectively, while the cooling water demand is expected to be 1,793,310 m3. The nominal levelized cost of electricity (LCOEnom) is 11.2 ¢/kWh. Furthermore, water production costs are <0.5 $/m3 in Aden, Damman, Sharm el-Sheikh, and Salalah, but >1.0 $ /m3 in Agadir and Algiers. The results obtained indicate that the combination of these two technologies can be a reliable source of power and fresh water for these locations.

Influence of eccentricity on the thermomechanical performance of a bayonet tube of a central solar receiver

This work numerically evaluates the thermal and mechanical behaviors of eccentric bayonet tubes to be used in external central receivers of solar power tower plants. A bayonet tube is composed of two tubes, one inside the other, creating circular and annular sections, through which the molten salt of the receiver sequentially flows. Eccentricity in the annular section is achieved by displacing the axis of the interior tube with regard to the exterior one. For comparative purposes, two examples of conventional tubes (single tubes with circular cross-sections with diameters of 25mm and 50mm) are also investigated in this work to compare their performances with those of bayonet tubes. The results obtained with the eccentric configurations show an enhancement of the heat transfer to the molten salt and a reduction of the tube wall overheating compared with the concentric bayonet tubes and the largest simple tube. For conditions representative of the normal operation of a solar power tower, eccentric bayonet tubes could reduce the pressure drop by 30.8% and increase the convective heat transfer achieved in a concentric configuration of the bayonet tube by 26.1%. Nevertheless, this pressure drop was considerably higher than those obtained in the smallest and largest simple tubes, which were 1.28 bar and 0.13 bar, respectively. To investigate whether the enhancement of the convection heat transfer experienced by bayonet tubes compensates for their higher pressure drop or not, a Performance Evaluation Criterion (PEC) was proposed and used to compare the global performance of bayonet tubes with that of conventional tubes. The bayonet tubes with eccentricity 0.45 obtained the largest PEC, which was up to 13% higher than reference conventional tubes. Enhancement of the tube wall refrigeration produced when increasing the eccentricity is reflected in the maximum tube temperature and thermal stresses, which are found to diminish by approximately 8.8% with the highest eccentricity. In addition, the largest eccentric bayonet tube layout obtains the smallest peak temperatures compared to conventional tubes. The lower inertial moment of the smallest conventional tube indicates that its thermal stress is 2.1% lower than the stress obtained in the most eccentric layout analyzed in this work. Nevertheless, the time to rupture associated with creep damage of the eccentric bayonet tube is 1.04 times higher than that obtained in the smallest simple tube, demonstrating that bayonet tubes could be a potential alternative to the current tubes of external tubular receivers.

Thermal performance of a supercritical CO2 based central receiver

This study investigates the thermal performance of a supercritical carbon dioxide (sCO2) based central receiver for a 3rd generation concentrated solar thermal (CST) plant having 10 MW thermal capacity. A thermo-optical modelling methodology is deployed to evaluate the thermal performance of tubular receivers with outer radii of 6.2 mm, 12.4 mm, and 24 mm. Solar PILOT ray tracing software is used to obtain the solar flux arrangement around the central receiver. The maximum heat flux permitted in the smaller tube receiver (ro = 6.2 mm) results in a smaller receiver and heliostat field for a particular power output. Heat flux concentration is found to be 77 % higher in a smaller tube (ro = 6.2 mm) receiver than in a large tube (ro = 21 mm). However optical efficiency is 3% higher in large tube receivers compared to smaller tubes. Computational fluid dynamics (CFD) simulation is performed to investigate the receiver performance considering Inconel 640 as a receiver material. Tube having ro = 21 mm has the highest solar to thermal efficiency (58.14%) i.e., 4.5% higher than the large tube (55.6%). Hence, further investigation is performed for the smallest tube to examine the variation of temperature, pressure drop, and Nusselt number as a function of Reynold’s number along the tube. There is a marginal change (1%) in the local Nusselt number from the receiver tube’s entry to exit.

Comparison Between CSP Systems and Effect of Different Heat Transfer Fluids on the Performance

While fossil fuel sources have declined and energy demand has increased, in addition to the climate change crisis, the world turned to using renewable energies to get its energy. Concentrated solar power (CSP) is one of the main technologies used for this purpose. This study aims to compare the different concentrated solar power technologies in terms of their efficiency, cost, concentration ratio, and receiver temperature. Results showed that technologies were arranged according to temperatures from high to low as follows; the parabolic dish reflector, central receiver collector, linear Fresnel reflector, and parabolic trough collector. According to cost, the parabolic dish reflector has the highest price, while the linear Fresnel reflector has the lowest price. Also, the parabolic dish reflector has the highest efficiency among the others, followed by the central receiver collector, then the linear Fresnel reflector, and the parabolic trough collector respectively. Additionally; the study represented that point-focus devices have a high percentage of concentration ratio than line-focus devices. Finally, in order to exploit these sources throughout the day, it is recommended to use phase change materials to store the excess thermal energy as a positive and effective approach to solving the energy problems.

Solar simulator based on induction heating to characterize experimentally tubular solar central receivers

Solar receiver tubes in solar power tower plants are subjected to non-homogeneous heat flux and temperature that produce early failure derived from the thermal stress. To reduce these problems, the thermomechanical characterization of the receiver is required. However, there are limitations in the data acquisition during operation due to the extreme working conditions, the different scale lengths, and the disturbance of the normal operation, being not possible to determine experimentally the thermomechanical behaviour of this device or to validate specific models developed.In this work an experimental facility able to reproduce the operation conditions of solar receivers has been designed and tested. To obtain the non-homogenous heat flux an induction heating system has been used. The facility has also been equipping of sensors and cameras that allow to measure the temperature distribution, the displacement and the strain field in a tube stretch. It is obtained a circumferential variation of the temperature of 160 °C, and a tube displacement due to the bending produced by the temperature gradient in combination to the mechanical boundary conditions of 2.251 mm. The data obtained with the cameras have been checked with the displacement and temperature sensors, obtaining maximum differences of 3 %, it means 5 °C and 0.05 mm. Thus, it is possible to derivate the tube displacement to obtain the hoop and axial strain field. These results are the first step for the thermomechanical characterization of tubes with non-homogeneous temperature profiles in the three directions. The proposed solar simulator will allow the validation and development of thermomechanical models able to reproduce the operation conditions of the receiver with the final goal of improving the receiver design and operation.

MHD Non-Aligned Stagnation-Point Flow of Nanofluid over a Stretching Surface with a Convective Boundary Condition

In the present paper, MHD non-aligned stagnation-point flow has been found to be interesting and innovative in the analysis of viscous nanofluids over a stretching surface with a convective boundary condition in presence of the porous medium. Due to its many engineering and industrial uses, such as cooling nuclear reactors during an emergency shutdown, soft sheet extrusion, metal spinning, and solar central receivers exposed to wind current, the study of oblique stagnation point flow is important. The suitable similarity transformation is utilized for the reduction of a set of governing equations, which are solved by using the Differential Transformation Method (DTM) with Maple software. The Nusselt number (Nux), skin friction (Cf), and Sherwood number (Shx) are tabulated. A strong agreement is seen, and the accuracy of the results tabulated using DTM and the numerical method (fourth-order Runge-Kutta-Fehlberg integration scheme) is illustrated. Further, velocity, temperature, and nanoparticle volume fraction profiles are shown graphically and studied various parameters. It is reported that the magnetic parameter reduces the axial and oblique velocity gradients while enhancing the temperature and volume fraction profiles. The porosity parameter reduces the axial and oblique velocity gradients while enhancing the temperature profile.

A review study on solar tower using different heat transfer fluid

The object of research is distinguishing the different heat transfer fluids (HTF) in concentrating solar power (CSP). CSP technologies are gaining more attention these years due to the fact that the world is facing significant problems, especially concerning environmental issues and the increasing electricity demand. The world countries are currently committed to mitigating climate change and limiting greenhouse gas emissions to keep the global temperature rising below 2 °C. As a result, renewable energy sources are required for power generation. One of the most widely used technologies is the solar tower, where mirrors reflect solar radiation into a central receiver on top of a tower that contains a working fluid known as heat transfer fluid. The HTF is one of the most important components in solar power tower plants used to transfer and store thermal energy to generate electricity. This study focuses on the HTF used in solar power towers and how it can affect the efficiency of the plant. The HTF discussed in this study are air, water/steam, molten salts, liquid sodium, and supercritical CO2. Among the review of HTFs in the solar tower system, the result of the research shows that the Air can reach the highest temperature while liquid sodium achieves the highest overall plant efficiency.

Energy and exergy analysis of microchannel central solar receivers for pressurised fluids

Within the new generation of advanced central solar receivers, microchannel pressurised gas receivers are emerging as reliable and efficient alternatives to operate at high temperatures and pressures. This paper presents an optimisation and comparative analysis of different compact plate-fin type structures, constituting the receiver’s absorber panels, classified according to the type of fin arrangement inside: plain rectangular, plain triangular, wavy, offset strip, perforated, and louvred fin. A versatile thermo-fluid receiver model is implemented, allowing simple variation of characteristic geometric parameters of each structure. Exergy efficiency is chosen as the optimisation function, as it considers both heat and pressure losses.The framework of the analysis is set by the receiver’s boundary conditions, operating at the design point conditions of a solar thermal power plant. For each compact structure, the optimal configuration is determined, providing interesting findings that have not been reported in the state-of-the-art to date. Although all geometries show good thermal performance, the perforated and plain rectangular configurations demonstrate the best exergy efficiencies of 59.21% and 58.80%, respectively, favouring taller and narrower channels. This analysis methodology could be seamlessly extrapolated to other gases and working conditions, owing to the thermo-fluid model’s versatility, to reveal the optimal configuration for each case.

Assessing the sustainability impacts of concentrated solar power deployment in Europe in the context of global value chains

In the context of the European Green Deal and the Recovery Plan for Europe, CSP can play its role, by providing dispatchable and flexible energy when other renewable technologies cannot. The aim of this paper is to identify the potential socioeconomic, social and environmental impacts associated to the future deployment of CSP projects in Spain, taking into account the global value chain. Based on an extended multiregional input-output model developed by the authors, this paper identifies the country and sector-origin of nine sustainability indicators for the two dominant CSP technologies (parabolic trough and central receiver). The research considers the deployment of a 200 MW CSP power plant in Spain to compare the sustainability impacts of these two technologies under three different scenarios regarding the country-origin of the main components. The results show that central receivers have more positive economic impacts, both in terms of value added and employment creation, and lower negative environmental and social impacts than the parabolic trough alternative. The economic and environmental impacts of the CSP deployed in Spain depend on the origin of components, with the highest negative environmental impacts occurring when the components come from China and the lowest when they come from Germany. The same occurs for the social impacts and supply risks, which are lower when Germany supplies the main components. The scenario in which Spain supplies all the components performs better than the Chinese supply scenario in terms of social risks, whereas no major differences among them were found on supply risks.

Experimental evaluation of wind induced pressure fluctuations in cavity shaped open volumetric air receivers

In this study wind induced surface pressure fluctuations during operation of an open volumetric cavity receiver were investigated in wind tunnel experiments. Due to the process design of the open volumetric receiver, surface pressure fluctuations impact the receiver mass flow which is crucial for cooling the highly irradiated receiver. For this study a model of a solar tower was constructed under the concept of similitude which allows wind tunnel experiments at Reynolds numbers up to 13.17 × 106. Transient pressure measurements were conducted under 17 different flow directions to evaluate the impact of separation induced pressure fluctuations. The experimental design further allows a rotation of the model to evaluate the impact of changes in wind direction on the surface pressure at the receiver. For cases under a constant wind direction, a critical angle range could be identified in head on wind with a horizontal inclination of 45.0 to 78.8° relative to the central receiver axis. The results further show that surface pressure fluctuations are more sensitive to changes in wind direction as the amplitudes with maximum 20Pa for a Reynolds number of 13.17 × 106 are about one order of magnitude higher compared to the cases with a constant flow direction. Furthermore, a frequency analysis shows the shielding effect of the cavity design for side-wind as no peaks in the pressure spectrum appear. For flow directions within the critical range of 45.0 to 78.8° a main vortex shedding frequency under constant Strouhal numbers of 0.25 to 0.50 can be observed.

Optimization of biomimetic heliostat field using heuristic optimization algorithms

Central receiver systems are one of the most promising solar energy harvesting technologies. They consist of a large field of sun-tracking mirrors known as heliostats that focus sunlight onto a receiver at the top of a tower to generate high temperatures for running a heat cycle. Optimum localization of heliostats in the field plays an essential role during the design phase of a central receiver system. A good design aims to obtain the highest energy yield and efficiency at the lowest cost. The primary parameter that affects the energy yield of a central receiver system is the optical efficiency of its heliostat field. Optimization is carried out to obtain an arrangement of heliostats, which maximizes optical efficiency. This study presents the optimization process of a biomimetic heliostat field design using different heuristic optimization algorithms, namely advanced particle swarm optimization, genetic algorithm, whale optimization algorithm, and gravitational search algorithm. In un-optimized biomimetic heliostat fields, the efficiency is 66.4% which is enhanced to 68.7% after optimization. The results show that the advanced particle swarm is the fastest method that converges in less than 20 iterations. The instantaneous efficiency of the field increases by approximately 3.48% after optimization by particle swarm optimization, followed by 3% with the gravitational search algorithm, 2.88% from the whale optimization algorithm, and 1.99% with the genetic algorithm. The results are compared with other similar works in optimizing the biomimetic heliostat field.

Effect of Actual Recuperators’ Effectiveness on the Attainable Efficiency of Supercritical CO2 Brayton Cycles for Solar Thermal Power Plants

One of the most promising concentrated solar power technologies is the central receiver tower power station with heliostat field, which has attracted renewed research interest in the current decade. The introduction of the sCO2 recompression Brayton cycles in the near future installations instead of the Rankine cycle is very probable, due to the prospects of a significant efficiency improvement, process equipment size and capital cost reduction. In this study, energy and exergy analysis of a recompression Brayton cycle configuration for a central receiver power station are performed. Special emphasis is given to the computation of actual performance for the High-Temperature Recuperator and the Low-Temperature Recuperator. The results define realistic thermal and exergetic efficiency limits for the specific cycle configurations applied on a central receiver solar power plant with variable turbine entry temperature. Thermal efficiency, predicted with the improved accuracy of heat exchanger computations, does not exceed the 50% target. Overall, a realizable total power plant efficiency of 37% at 900 K turbine entry temperature is predicted, which is a significant improvement on the current state-of-the-art with steam Rankine cycles.

Thermoeconomic optimization of a solar-assisted supercritical CO2 Brayton cycle, organic Rankine cycle and multi-effect distillation system

In this paper, the simulation and optimization of a combined supercritical carbon dioxide Brayton cycle, an organic Rankine cycle and multi-effect distillation system driven by solar energy have been applied for power and freshwater generation. In this cycle, the solar collector, the central receiver reflected the sun’s light by heliostats, enters the storage system and then enters the fluid stream according to the amount of heat required to initiate the cycle. The working fluid of solar receiver is a mixture of the 60% NaNO3 and 40% KNO3, supercritical carbon dioxide is working fluid of the Brayton cycle and R600 is the working fluid of the organic Rankine cycle. The innovation of this article is using power and fresh water cycle without fuel consumption (with solar system and storage tanks). The simulation of this combined cycle was carried out by engineering equation solver software and energy and exergy efficiency changes in terms of different parameters are obtained. Then, a multi objective optimization of this system considering exergy efficiency and cost of system as objective functions is performed by genetic algorithm in Matlab software. Decision variables of the whole cycles are including Compressor inlet temperature, Turbine inlet temperature, Number of MED effect, The temperature of the water fed the desalination, Evaporator pinch point, Mass flow (Critical Carbon Dioxide), Turbine inlet pressure, Compressor inlet pressure and Pressure drop. The two objective functions optimization including exergy and economic parameters of this cycle is carried out for achieving reduction of electricity generation cost and increase of the exergy efficiency. The results of this optimization showed, the maximum exergy efficiency of this combined system is 61.78% and the minimum cost of electricity production is 0.2617 $/kWh. In this regard, the multiple effect distillation system produces 530.9 KgS freshwater in 15 stages.

Brayton technology for Concentrated Solar Power plants: Comparative analysis of central tower plants and parabolic dish farms

Concentrated solar power plants intend to be key in the pool of renewable energy production technologies in the next future because of their versatility and high efficiency. In this work a comparative study between two promising technologies is developed. A central tower receiver surrounded by a heliostat field and a farm of parabolic dishes, both coupled to a hybrid Brayton cycle, are considered. Two power scales are surveyed (between 5 and 20 MW) at three different locations with quite different latitudes (between Sahara desert and medium European latitudes) and meteorological conditions. A modelling scheme developed by our group that allows to obtain the expected thermodynamic and thermo-economic plant records is applied. Key indicators like efficiency, net generated energy, levelized cost of electricity, and specific plant investment are calculated and analysed. Variability of natural gas prices and also land cost uncertainty are reflected on levelized cost of electricity range. Among the plants compared, minimum values are found within the interval [135–163]USD/MWh for central towers at the highest power considered and southern latitudes. In addition, the area needed for the installation of the plants and the influence of CO2 taxes is also analysed. Displayed cashflows show larger investment costs for central tower than for dish farms. Finally, those systems are put into the context of other concentrated solar power, other renewable, like wind or photovoltaic, and other conventional power plants.

Numerical Investigation of Concentrated Solar Central Billboard with Hexagonal Tubes.

The solar receiver is the most important component of any central solar tower power plant (CSP) system. A numerical analysis of four billboard geometry designs of the central tower receiver was undertaken in this study. On the receiver, the surface area, heat transfer fluid (HTF), and intensity of beam radiation were all constant. The mass flow rate of HTF was modified, and the temperature gain was used as a metric to determine the most efficient design based on the analytical results. Four different models of vertical tube receivers were designed and analyzed. In the analysis, the surface area of the receivers was the same. When compared to the vertical variable circular tube receiver design, the vertical variable hexagonal tube receiver design achieved a marginally higher temperature for the HTF fluid at lower mass flow rates.

Performance of the world’s first integrated gas turbine–solar particle heating and energy storage system

• A proof-of-concept gas turbine–solar particle heating hybrid system was developed. • The particle heating receiver is able to heat the falling particles up to 720 °C. • Harnessing solar energy was demonstrated. • Utilizing the stored thermal energy during off-sun operation was demonstrated. • Excessive heat loss was traced and estimated. The world’s first integrated gas turbine–solar particle heating hybrid system has been realized on the campus of King Saud University (KSU), Saudi Arabia. The system was built and tested as a proof-of-concept, such that, upon successful completion of the test, a larger, commercial-scale system can be built with confidence. The successful execution of this project has yielded the following important observations: (1) the particle’s central receiver system can heat the falling particles to 720 °C; (2) the hybrid system can store solar thermal energy in particles and transfer this energy (via a particle-to-working-fluid heat exchanger) to the compressed air before entering the microturbine.; (3) the microturbine can still operate using the stored thermal energy even after the solar field was shut down; (4) although the temperature rise of the compressed air across the heat exchanger was not high, it was adequate to prove the system’s ability to use the particles’ stored energy as a heat source.

Impact of a mechanical attachment on the preheating temperatures of a central receiver tube

The receiver tubes of Solar Power Tower plants are typically attached through clips and sliding rods to the reradiating wall of the receiver in order to reduce the thermal deflection of the tubes. However, as a side effect, these mechanical attachments increase heat dissipation from the tube to the exterior and can reduce the local temperature of the tube during the receiver start-up, an operation performed every morning or after a severe drop of solar irradiation due to passing clouds. In the start-up operation, the empty tubes of molten salt receivers must be preheated with a careful aiming sequence of the heliostat field until their temperature is high enough to avoid the freezing of the incoming flow of the molten salt. This work numerically addresses for the first time the influence of the mechanical attachment on the preheating temperature of a receiver tube. To achieve this goal, a set of three-dimensional thermal fluid simulations of the temperature distribution in the tube and the mechanical attachment, described with different levels of detail, has been performed for the receiver of the Gemasolar Solar Power Tower plant. The results of this work show that the mechanical attachment locally affects the tube temperature, leading to a temperature overestimation above 25.1% when the tube is modeled without a mechanical attachment. In addition, the temperature measured separated from the attachment at the rear face of the tube to control the preheating sequence may not be very representative of the minimum tube temperature, which occurs in the internal face of tube just beneath the mechanical attachment. The results indicate that accumulation of heat not only by the clip but also by the guide and the rod of the mechanical attachment plays a significant role in the dissipation of heat from the tube to the attachment. This reveals the need of considering all the elements of the mechanical attachment if an accurate modeling of the preheat temperatures of the tube is needed. Besides, the use of a simplification in the modeling of the air and radiative heat transfer outside the tube reduces by a factor of 4.9 the computational cost involved in a full simulation of these transfer processes, with a temperature discrepancy between models below 14.3%. Finally, the effect of the size of the attachment clip on the minimum tube temperature is investigated, revealing that the minimum tube temperature of the preheated tube can decrease below the freezing temperature of the molten salt for clip heights larger than 170 mm . • Preheat temperatures in a receiver tube with a mechanical attachment are simulated. • The attachment clip, guide and rod need to be modeled to ensure accuracy. • The heat absorbed by the tube is partially transferred to the attachment. • The attachment creates a cold spot in the tube close to the clip during the preheating. • The control thermocouple temperature is not representative of minimum temperature.

Introducing and assessment of a new wind and solar-based diversified energy production system intergrading single-effect absorption refrigeration, ORC, and SRC cycles

This paper proposes and evaluates an integrated energy production system using two forms of renewable energy, solar and wind, in order to deliver cooling, heating, electricity, and water desalination. Along with organic Rankine cycle components (ORC), this diversified energy system includes an absorption refrigeration system, steam Rankine cycle (SRC), thermoelectrics, reverse osmosis, wind turbines, and parabolic-linear solar collectors. This study contains several innovations, including using thermoelectrics in the Rankine organic cycle instead of a condenser that gives the system a high capacity, utilizing parabolic solar collectors, and implementing wind energy as the direct source of electricity for such system. Energy, Exergy, and Exergoeconomic analysis approach is performed for the evaluation approach. EES software is used to model and analyze the data. As part of the validation process, the results are compared with those published previously and are found to be relatively consistent. The research results revealed four points. First, with the increase in solar radiation, the amount of freshwater produced for the system increased from 69.15 to 75.23 m3/h. Second, the total exergy efficiency increased from 54.24 to 77.27% when the steam turbine's inlet pressure was increased. Third, the system's total cost decreased from 77.27 to 28.30 $/h with increasing ambient temperature. Fourth, the highest exergy loss is associated with solar energy with a central receiver. Based on exergy losses, it was determined that a solar system with 60% and a wind turbine with 17% have the highest losses.