Solar Collector

The objective of this paper is to model and optimise solar organic rankine cycle (ORC) engines for reverse osmosis (RO) desalination using currently available solar thermal collectors. The proposed systems are intended to be potentially attractive for remote areas without (or with very high cost) access to the public electricity grid.

From 2002 to 2006, a combined R&D project named AQUASOL has been carried out at the facilities of the Plataforma Solar de Almería (Spain). Main objective of this project has been the development of a hybrid solargas desalination system based on multi-effect distillation process that meets at the same time the requirements of low-cost, high efficiency and zero discharge.

This paper investigates the physical limits of a solar collector for orbit deflection of near-Earth asteroids (NEAs) on a collision course with Earth. For decades of warning time a small change of NEA orbital velocity v by a few mm/s might suffice to alter the collision path into an Earth fly-by and consequently avert a local or even global catastrophe. In principle this can be achieved by a spacecraft that carries a large solar collector. The latter focuses sunlight onto the NEA surface in order to vaporize surface material, hence transferring a continuous momentum to the NEA. We model evaporation process and vapour expansion to show that the functionality exists. From the analysis of focussing misalignments and collector degradation we find that a considerable operational effort is required to maintain operating conditions. The most important result is that the collector lifetime is limited to only a few minutes. Therefore a solar collector might only be applicable to NEAs with size < 250 m if v < 0.1 mm/s is required. We also discuss capabilities for the prolongation of collector lifetime and hence an increase of NEA application size range.  2006 Elsevier SAS. All rights reserved.

Over the last few years, the possible scenario of an asteroid threatening to impact the Earth has stimulated an intense debate among the scientific community about possible deviation methods. In this paper we present a comparative assessment of some of the more feasible mitigation schemes reviewed in the literature (i.e. solar collector, nuclear blast, kinetic impactor, low-thrust propulsion and mass driver). For each strategy, a multi-criteria optimization method has been used to construct a set of Pareto optimal solutions, minimizing both the mass of the spacecraft and the warning time, while simultaneously maximizing the deviation. A dominance criterion has then been defined and used to compare all the Pareto sets. The achievable deviation at the MOID, either for a low-thrust or for an impulsive maneuver, has been computed through a set of analytical formulas. The variation in the orbit of the NEO has been estimated through a deviation action model that takes into account the wet mass of the spacecraft on the Earth. Finally the technology readiness level of each strategy has been used to recompute a more realistic value for the required warning time.

We report on an experimental study conducted to investigate the impact of heat enhancement devices on the thermal performance of a flat-plate solar collector. Different passive heat enhancement devices that include twisted strip, coil-spring wire and conical ridges were studied. The comparison showed no appreciable difference in the heat flux to the collector fluid. A detailed investigation of the observed trend showed significantly high values of Grashof, Richardson and Rayleigh numbers indicating that the heat transfer mode in the solar collector is of mixed convection type with free convection as the predominant mode. It is concluded that due to the significant damping of shear-produced turbulence by buoyancy forces, the applied passive methods based on the enhancement of shear-produced turbulence are ineffective in augmenting heat transfer to the collector fluid in flat-plate solar collectors.

Solar cooling applied to buildings is without a doubt an interesting alternative for reducing energy consumption in traditional mechanical steam compression air conditioning systems. The study of these systems should have a closely purely fundamental approach including the development of numerical models in order to predict the overall installation performance. The final objective is to estimate cooling capacity, power consumption, and overall installation performance with relation to outside factors (solar irradiation, outside temperature.). The first stage in this work consists of estimating the primary energy produced by the solar collector field. The estimation of this primary energy is crucial to ensure the evaluation of the cooling capacity and therefore the cooling distribution and thermal comfort in the building. Indeed, the absorption chiller performance is directly related to its heat source. This study presents dynamic models for double glazing solar collectors and compares the results of the simulation with experimental results taken from our test bench (two collectors). In the second part, we present an extensive collector field model (36 collectors) from our solar cooling installation at The University Institute of Technology in St Pierre, Reunion Island as well as our stratified tank storage model. A comparison of the simulation results with real scale solar experimental data taken from our installation enables validation of the double glazing solar collector and stratified tank dynamic models.

A sealed space between absorber and cover glass in a flat plate solar collector makes it possible to reduce the influence of humidity condensate and dust at the same time as the enclosed space can be filled with a suitable gas for lowering the heat losses. This article describes the influence of different gases on the heat losses in a typical flat plate solar collector. A model of a gas-filled flat plate solar collector was built in Matlab with standard heat transfer formulas. The results show that the overall heat loss can be reduced by up to 20% when changing from air to an inert gas. It is further possible to reduce the distance between absorber and cover in order to reduce the mechanical stresses in the material with similar heat losses.

In this study solar-assisted heat pump (SAHP) system with flat plate collectors was investigated experimentally and tested for domestic space heating. SAHP system was located in a test room with 60 m 2 floor area in Firat University, Elazig (38,411N, 39,141E) Turkey. The experiments were performed in heating season of January 2003. The coefficient of performance of the SAHP system was calculated. The system COP of the SAHP was obtained as 3.08 while the exergy loss of the solar collector was found to be 1.92 kW. The second law efficiency of the compressor, condenser, evaporator and solar heat exchanger in SAHP system were evaluated 42.1%, 83.7%, 43.2% and 9.4%, respectively. The first law efficiency and exergetic efficiency of the whole system are found to be 65.6%, 30.8%, respectively. Consequently the energy and exergy loss analysis results show that the COP increase when the exergy loss of evaporator decrease.

The use of booster reflectors in front of solar collectors is an established technique for increasing the irradiation onto solar collectors. By using corrugated instead of flat booster reflectors it is possible to increase the annual irradiation onto the collector plane, thereby maximising the annual output from the collector-reflector arrangement. The paper includes a description of a ray tracing program which calculates the annual optical performance of a collector-booster reflector system with different V-corrugated reflectors. Calculations based on Swedish solar radiation data show that the use of a booster reflector with varying V-corrugations along the reflector, instead of a flat booster reflector, can increase the annual reflected direct radiation on to the collector by 10%. This is estimated to result in a 3% increase in the annual collector output. The ray-tracing calculations are compared with measurements of the reflection characteristics of single V-shaped reflector arrangements.

Seventy to ninety percent of the electric energy used by dishwashers and washing machines heats the water, the crockery, the laundry and the machine and could just as well be replaced by heating energy from solar collectors, district heating or a boiler. A dishwasher and a washing machine equipped with a heat exchanger and heated by a hot water circulation circuit instead of electricity (heat-fed machines) have been simulated together with solar heating systems for single-family houses in two different climates (Stockholm, Sweden and Miami, USA). The simulations show that a major part of the increased heat load due to heat-fed machines can be covered by solar heat both in hot and cold climates if the collector area is compensated for the larger heat load to give the same marginal contribution. Using ordinary machines connected to the hot water pipe (hot water-fed machines) and using only cold water for the rinses in the washing machine gives almost the same solar contribution; however considerably lower electrical energy savings are achieved. The simulations also indicate that improvements in the system design of a combisystem (increased stratification in the store) are more advantageous if heat-fed machines are connected to the store. Thus, using heat-fed machines also encourages the use of more advanced solar combisystems.

The design, construction and test results of non-evacuated stationary CPC solar collectors with flat absorbers are presented and discussed. The proposed collector design is based on a truncated asymmetric CPC reflector, consisting of a parabolic and a circular part. A flat bifacial absorber is installed at the upper part of the collector, parallel to the glazing to form a thermal trap space between the reverse absorber surface and the circular part of the mirror. Two prototypes based on the same collector geometry were constructed and tested. The first model consists of one mirror-absorber unit and the second of three smaller units integrated in one collector device. The truncated CPC mirror and the installation of the absorber parallel to the glazing keep the optical efficiency at a satisfactory level. The reduction of radiative thermal losses by using selective absorbers and the suppression of convection thermal losses from the reverse absorber surface to the collector cover result to a significant decrease of the total collector thermal losses. The experimental results showed that the proposed CPC collector could achieve a maximum efficiency of 0.71 and a stagnation temperature of about 1808C, with the multiunit collector device being more efficient and practical.

Continuous escalation of the cost of generating energy is preceded by the fact of scary depletion of the energy reserve of the fossil fuels and pollution of the environment as developed and developing countries burn these fuels. To meet the challenge of the impending energy crisis, renewable energy has been growing rapidly in the last decade. Among the renewable energy sources, solar energy is the most extensively available energy, has the least effect on the environment, and is very efficient in terms of energy conversion. Thus, solar energy has become one of the preferred sources of renewable energy. Flat-plate solar collectors are one of the extensively-used and well-known types of solar collectors. However, the effectiveness of the collector’s absorber plate to absorb solar energy limits the efficiency of this type of collector, as does the inefficient transfer of the solar energy via heat transfer to the fluid in the collector’s flow channels. To improve its efficiency and perf...

Le travail présenté est l'étude d'un système de chauffage solaire pour un local monozone. Le système est composé d'un champ de capteurs solaires plans, d'une cuve de stockage d'eau chaude, et d'un local à chauffer. Le système de distribution est composé d'un serpentin en cuivre intégré au milieu du plancher. La modélisation mathématique du système est basée sur le calcul des bilans thermiques au niveau des éléments constituants le système de chauffage: fluide caloporteur, plancher et air intérieur du local. Les équations différentielles obtenues sont résolues par la méthode des différences finies avec un schéma explicite. Les résultats obtenus du modèle ont été confrontés aux résultats d'une étude similaire du Pr. Zaheer-Uddin. La confrontation montre une bonne concordance. Le modèle a été utilisé ensuite pour simuler le comportement thermique du système complet sur le site de Bouzaréah (Alger).

In this work a drying system was constructed, consisting of three parts (solar collector, solar drying cabinent, and air blower). Two identical air solar collectors having V-corrugated absorption plates of two air passes, a single glass cover was used. The total area of the collectors is 2.4 m 2. The dimensions of the drying cabinet are 1 × 0.33 × 2 m (width, depth, and height). The cabinet is divided into six divisions separated by five shelves. The distance between the shelves is 0.3 m except the upper one, which is 0.5 m from the roof. Each shelf is 0.95 × 0.3 m and is made of metallic mesh. The drying chamber walls are made of aluminum plate except the southern side, which was fixed with glass plate having the dimensions 1 × 2 × 0.002 m. Two types of fruit and one type of vegetables were dried during the present work. These were grapes, apricots, and beans. The moisture content of apricot was reduced from 80 to 13% within one day and a half of drying. Moisture content of grapes was reduced from 80 to 18% in two and a half days of drying, while that of beans was reduced from 65 to 18% in one day only. The results show that the most effective factor on the drying rate is the temperature of the air inside the cabinet. The effect variation of speed of air inside the drying cabinet is small and can be neglected. The relative humidity of air exit from the cabinet was small between (25-30%) and therefore there is no need for high velocity air inside the cabinet.

The performance of water-in-glass evacuated tube solar water heaters is evaluated using experimental measurements of optical and heat loss characteristics and a simulation model of the thermosiphon circulation in single-ended tubes. The performance of water-in-glass evacuated tube solar collector systems are compared with flat plate solar collectors in a range of locations. The performance of a typical 30 tube evacuated tube array was found to be lower than a typical 2 panel flat plate array for domestic water heating in Sydney. Solar 2005

The Solar Energy Research Group in the Universiti Kebangsaan Malaysia has been set-up more than two decades ago. One of the activities is in the field of solar thermal process, particularly in development of solar assisted drying systems. Solar drying systems technical development can proceed in two directions. Firstly simple, low power, short life, and comparatively low efficiency-drying system. Secondly, the development of high efficiency, high power, long life expensive solar drying system. The group has developed four solar assisted drying systems namely (a) the V-groove solar collector, (b) the double-pass solar collector with integrated storage system, (c) the solar assisted dehumidification system for medicinal herbs and (d) the photovoltaic thermal (PVT) collector system. The common problems associated with the intermittent nature of solar radiation and the low intensities of solar radiation in solar thermal systems can be remedied using these types of solar drying systems. These drying systems have the advantages of heat storage, auxiliary energy source, integrated structure control system and can be use for a wide range of agricultural produce.

The paper is focused on the dynamic simulation of a Photovoltaic/Thermal collector (PVT) integrated in a high-temperature Solar Heating and Cooling (SHC) system. The system is based on the following main components: concentrating parabolic PVT (photovoltaic thermal) collectors, a double-stage LiBr-H2O absorption chiller, storage tanks, auxiliary heaters, balance of plant devices. The PVT is made-up by a parabolic dish concentrator and a triple-junction receiver. The polygeneration system provides electricity, space heating and cooling and domestic hot water for a given building, whose simulation is also included in the model. In particular, PVT produces electric energy, which is in part consumed by the building loads (lights and equipments), in part by the system parasitic loads, whereas the eventual excess is sold to the public grid. Simultaneously, the PVT provides the heat required to drive the absorption chiller. The system was simulated by means of a zero-dimensional transient model, that allows the evaluation of temperature profiles and also heat/electrical energy flows for whatever period of the year. It is also possible to evaluate the overall energetic and economic performance on whatever time basis (day, week, month, year, etc.). The economic results show that the system under investigation can be profitable, if a proper funding policy is available. The paper also includes an extensive parametric analysis aiming at evaluating the set of design and operating parameters (solar field area, tank volumes, set point temperatures, etc.) that maximize the energetic and/or economic performance of the system.

This paper presents a detailed review of the numerical studies carried out by various researchers in order to obtain enhanced heat transfer in free, forced, and mixed convection, under laminar, transition, and turbulent flow regimes, by using nanofluids in different solar collector geometries. Recently, nanofluids have been increasingly used in various solar collector configurations. Nano-sized metallic or non-metallic particles such as Cu, Au, Al2O3, SiO2, TiO2, CuO, etc, were used in the heat transfer fluid for various solid volume fractions. The average size of the particles was less than 100 nm. The higher conductivity of nanoparticles even at low particle concentration results in higher thermal conductivity of the base fluid and improves the thermal characteristics of the system. Nanoparticle size, type and shape are important factors for the thermal conductivity enhancement of the nanofluid with nanoparticles.

A solar timber kiln with the capacity to season 3"24 m 3 of lumber was designed, constructed and used for seasoning commercial sawnwood. The kiln was constructed of a timber frame covered with transparent polythene sheet on the top and black leatherette on the sides. Corrugated, galvanized-iron sheet painted black and tilted at 30 ° to the horizontal served as a heat collector. Two fans were fitted for air circulation. The kiln attained a maximum temperature of 24 ° above the ambient temperature. The average efficiency of the heat collector was 38"5%. The solar kiln reduced timber drying time by 33.3-57"1% when compared with an air-drying technique. Sawnwoods (25 mm by 300 mm by 360 ram) of Mansonia altissima and Terminalia superba were dried from 46.16 to 15.02% and from 52 to 15.4% moisture content respectively in 12 days.

This paper presents a detailed review of the numerical studies carried out by various researchers in order to obtain enhanced heat transfer in free, forced, and mixed convection, under laminar, transition, and turbulent flow regimes, by using nanofluids in different solar collector geometries. Recently, nanofluids have been increasingly used in various solar collector configurations. Nano-sized metallic or non-metallic particles such as Cu, Au, Al2O3, SiO2, TiO2, CuO, etc, were used in the heat transfer fluid for various solid volume fractions. The average size of the particles was less than 100 nm. The higher conductivity of nanoparticles even at low particle concentration results in higher thermal conductivity of the base fluid and improves the thermal characteristics of the system. Nanoparticle size, type and shape are important factors for the thermal conductivity enhancement of the nanofluid with nanoparticles.

This work includes the evaluation of the solar contribution in solar cooling systems by the newly developed solar cooling design chart. The effect of collector area and storage volume on the solar fraction is well taken into account in the cooling design charts. The results of several experimental installations are compared with the present cooling f-chart predictions. The agreement is very good, which verifies the validity of design predictions by the new cooling f-chart. Changing the collector area in a solar cooling system has a similar effect on the solar fraction as that in a solar heating system. Storage volume appears to show an optimum in a solar cooling system with a marked influence on the solar contribution. The cooling f-chart may be used in equation form for design purposes. Design by solar cooling design charts is applicable for different building constructions, solar collector types, length of cooling season, location and meteorological conditions.

Evacuated tube solar collectors have better performance than flat-plate solar collectors, in particular for high temperature operations. A number of heat extraction methods from all-glass evacuated tubes have been developed and the water-in-glass concept has been found to be the most successful due to its simplicity and low manufacturing cost. In this paper, the performance of a water-in-glass evacuated tube solar pre-heater is investigated using the International Standard test method ISO 9459-2 for a range of locations. Factors influencing the operation of water-in-glass collector tubes are discussed and a numerical study of water circulation through long single-ended thermosyphon tubes is presented. Preliminary numerical simulations have shown the existence of inactive region near the sealed end of the tube which might influence the performance of the collector.

An integrated transient simulation program is developed for simulating the Iraqi solar house cooling system, using TRNSYS as a design tool. The simulation is modeled for other virtual solar cooling systems similar to the Iraqi solar house. A number of computer programs were developed and used in parallel with TRNSYS for developing an integrated program for the complete simulation of a solar cooling system with a lithium bromide-water absorption chiller. The results obtained from the simulation were used to develop a general design procedure for solar cooling systems, presented in a graphical form called the cooling f-chart. Using this design chart simplifies the designerÕs task for predicting the long term cooling energy supplied from a solar collector array serving an absorption chilled water system. A correlation was developed from the simulation results for estimating the hot water storage size necessary for the solar cooling system. This was based on minimizing the energy discarded from the vent valve when the solar heated water attains a temperature higher than the boiling temperature.

The paper deals with optimal flow control in closed loop flat plate solar collector systems. The water storage tank operates in the fully mixed regime. Two design configurations were considered: (A) one serpentine in the tank (for the secondary circuit) and (B) two serpentines in the tank (for both primary and secondary circuits). An indirect optimal control technique based on Pontryagin's maximum principle was implemented. A detailed collector model and realistic meteorological data from both cold and warm seasons were used in applications. Configuration (A) gives better performance than configuration (B) but cannot be used during the cold season at higher geographical latitudes. The optimal operation strategy involves two step up and down jumps between zero and a maximum allowable fluid flow rate in the primary circuit. During days with overcast sky, the pump in the primary circuit operates almost continuously. During days with cloudy or clear sky, the pump often stops. Heat provided to the user increases when the maximum fluid flow rate increases. This applies to both configurations (A) and (B). In the case of configuration (B), the heat provided to the user becomes rather constant at higher flow rates. When a constant flow rate strategy is adopted, there is an optimum ratio between the volume of the storage tank and the area of the solar energy collection surface: V s /A % 33.3 L/m 2 . The optimal control strategy does not exhibit such an optimum: the thermal energy supply to the user (slightly) decreases by increasing the ratio V s /A.

A solar assisted absorption refrigeration system (SAARS) was designed for acclimatizing of villas in Mardin which is located in Turkey and the performance of the system under different temperatures was analyzed by using MATLAB. Hourly cooling load calculation of the villas was done between 15th of May and 15th of September by considering the season for the cooling. Cooling capacity

The purpose of this research is to design a water distillation system that can purify water from nearly any source, a system that is relatively cheap, portable, and depends only on renewable solar energy. From the results of project calculations a truthful estimate was made to prototype the most effective geometries of the distiller and trough concentration system, one that will maximize evaporation/condensation and re capture waste heat to minimize thermal losses. To achieve this goal, a system was designed incorporating a parabolic solar trough coupled with a custom designed distillation device. The incoming solar radiation from the sun is focused and concentrated onto a receiver pipe using a parabolic trough, heating the incoming impure water, at which point it is sprayed into our custom designed distillation device where it evaporates and is re-condensed into pure potable water. Future goals for this project include calculation refinement, material research/testing, and fabrication.

Solar energy is so far the most promising and sustainable alternative energy source to fossil fuels. The new solar technology proposed in this research, building-integrated
photovoltaic-thermal (BIPV/T) systems, can be attached to the façade or replace conventional cladding, enabling on-site generation of solar electricity and heat, which can fulfill a significant portion of the building energy requirements. The overall objective of this research is to develop (a) prototype BIPV/T systems coupled with open-loop corrugated Unglazed Transpired Solar Collectors (UTC); (b) new modeling
representations for design, analysis, and control of BIPV/T integrated in the operation of building Heating, Ventilation and Air Conditioning (HVAC) systems; (c) an innovative
energy management framework, over a future planning horizon, based on model-predictive control algorithms that can anticipate the variability of solar irradiance and building load, thus enabling the optimal operation of high performance buildings with distributed solar energy resources and active thermal energy storage.
To this end, high-resolution, three-dimensional Computational Fluid Dynamics (CFD) models are developed to investigate the complex airflow and heat transfer mechanisms in BIPV/T systems and provide a solid foundation that supports the
formulation of thermal analysis models. The CFD models are validated using data from an experimental set-up in a state-of-the-art solar simulator facility, in terms of the cavity
exit air temperature (the error less than 1°C), the stream-wise development of plate surface temperature (the error less than 1°C), and vertical profiles of stream-wise velocity (average error within 10 %) and turbulent kinetic energy (average error within 20 %).
Energy prediction models for both corrugated UTCs and UTCs integrated with BIPV/T systems are established to evaluate their performance (electrical and thermal energy output, outlet air temperature, etc.) for different weather (incident solar radiation
and wind speed) and system design parameters (corrugation geometry, PV module coverage ratio, suction velocity, etc.). Comprehensive Nusselt number and effectiveness correlations, representing both the exterior and interior convective heat transfer processes in BIPV/T systems, are obtained from the CFD simulations and subsequently used in the energy models. Experimental data for prototype BIPV/T collectors installed at Purdue’s Architectural Engineering Lab are used to validate the energy models. Comparison between the model predictions and the experimental data verifies the dynamic response
of the collectors to weather and operating conditions, with the root mean square error within 1 °C in terms of cavity exit air temperature for the UTC configuration and within 2 °C (PV surface temperature) for the model of UTC with PV modules. The methodology for the analysis of the thermal boundary layer development and convective heat transfer process can be generalized to uniform approaching flow over corrugated plates with discrete suction, while the Nusselt number and effectiveness correlations and the physical modeling approach can be adopted to other BIPV/T systems.
Then the energy models are implemented in building simulation platforms to enable integration of BIPV/T with building HVAC systems (air handling unit and radiant floor heating) and active thermal storage systems. Finally, a deterministic model-predictive control algorithm is formulated for the integrated solar system. This includes building up a detailed dynamic system model in TRNSYS, presenting a system
identification approach to obtain simplified gray and black-box models that capture the relevant system dynamics and are computationally efficient for implementation in real controllers, formulating the cost function and setting up the constraints and the optimization environment, and examining the potential impacts associated with the prediction accuracy of the solar irradiance, which is the most significant disturbance acting on the system. The energy saving potential of the integrated system and the predictive controller is investigated in comparison with baseline operation strategies used in commercial buildings, using the Hydronic Laboratory at Purdue’s Living Laboratories as a simulation test-bed. The investigation shows that efficient integration concepts and
optimal control strategies are necessary to predict and plan the energy cost for the integrated solar system, resulting in total energy savings for the integrated solar system that can be up to 45 %. The modeling representations and approaches developed in this study can be generalized and extended to other commercial buildings with different integrated solar systems, HVAC systems and energy storage.
In summary, the solar technology (prototype BIPV/T collectors), systems representation, validated models, and the numerical prototypes of predictive-control algorithms developed in this dissertation found to be an efficient approach for buildingscale
renewable energy generation and utilization in high performance commercial buildings. The research presented herein is a necessary precursor for future investigation and expansion of smart buildings or net-zero energy buildings and the adoption of innovative energy management concepts in engineering practice. With large-scale deployment, this could be an effective pathway to reduce greenhouse gas emissions and
the need to build new fossil fuel power plants.

This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP cycle ) and solar coefficient of performance (COP s ), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed.

In this paper, a numerical investigation of the two modes of heat transfer, natural convection and surface thermal radiation, in a tilted slender cavity such a collector is presented. The 2-D conservation of mass, momentum and energy are coupled with a radiative model through the boundaries and solved by the finite volume method. The studied parameters are: aspect ratios (8≤A≤16), inclination angles (15°≤≤35°) and Rayleigh numbers (104≤Ra≤106). The results indicated that the radiative surface radiation coupled with the natural convection modifies the flow patterns and the average heat transfer in the slender cavity between the absorber plate and the glass in the collector. The convective heat transfer coefficient and the radiative heat transfer coefficient as a function of the aspect ratio and the inclination angles are shown. It was found that the radiative heat transfer contributes more than 40% of the total heat transfer. A comparison between the present Nusselt numbers against the ones used for the design of solar collectors reported in the literature is presented.

Prinsloo, G.J. (2014). Automatic positioner and control system for a motorized parabolic solar reflector. MSc Thesis, Stellenbosch University. p 1-142. DOI: 10.13140/RG.2.1.1130.3522
This project deals with the CAD design and construction of an automatic Solar Tracking system for Sun Tracking and Sun Following based upon the sun vector and the sun's position at any given time and the position of the sun for any GPS location on the earth. It drives hybrid solar Stirling technology for thermal and electricity generation and finds application in smart microgrid development for power and energy distribution an dispatch in off-grid and grid-tied applications. Automatic sun tracker positioner and control system for a motorized parabolic dish solar reflector and mechatronic solar tracking control system project describes the development and CAD design in a dual-axis sun tracker application for a stand-alone off-grid 3 kW solar electrical self-tracking concentrating solar power system. This autonomous power stand-alone solar tracking application and parabolic collector harness sunlight in a dish Stirling system or concentrated photovoltaic system by implementing a dynamic mechatronic platform and digital electronic control system for an autonomous concentrating solar power for CSP and CPV. The same sun tracker can also be used in solar PV photovoltaic where the solar panels follow the sun throughout the day. Design specifications required a high-precision automatic positioning and solar tracking control system for a self-tracking motorized parabolic solar collector with an optical solar harnessing capacity of 12 kW solar thermal. The solar receiver is a point-focussing parabolic dish that pinpoints towards the sun to collect sun energy, but may also be a line-focussing solar trough. Stand alone off-grid concentrated solar and solar tracking system require intelligent digital control approaches to ensure optimal energy efficiency and management of the power budget. In co-generation systems, this is especially true for digitally controlled solar micro combined heat and power (mCHP or CHP), solar micro combined cooling heating and power (mCCHP or CCHP) trigeneration and polygeneration type systems that feed into microgrid and smartgrid systems in district power systems, remote areas, island power, rural villages, eco-estate housing schemes and industrial process heating systems.

One of the important parameters that affects the performance of a flat plate solar collector is its angle of tilt with the horizontal. This is due to the fact that the variation of tilt angle changes the top loss coefficient and the amount of solar radiation reaching the absorber plate. A mathematical model has been developed for calculating the useful energy gained by a fiat plate collector under various operating conditions. The model is then used to determine the optimum tilt angles for a typical collector in Basrah on a daily basis, as well as on the basis of a specified period. The optimum tilt angle is found by searching its value for which the useful energy gained by the collector is a maximum for a particular day or a specified period.

Seeking innovative methods is critical for efficient solar energy utilization. In this study, a promising alternative to the conventional systems is introduced by integrating heat pipes to widely used flat plate collectors as a means of heat extraction devices. It is expected that such configuration can avoid some of the drawbacks that inherently exist in the traditional flat plate collectors. Transient performance analysis was performed for a complete forced circulation solar water heating system operating with a heat pipe flat plate collector (HPFPC). In addition, thermal behaviour of the whole system and its daily energetic and exergetic performances were discussed considering hourly weather data from the coldest month of the year with the mean daily temperature of 9.56 C in Fez, Morocco. Moreover, a simulation environment was introduced and dynamic simulations were performed to assess the overall performance under worst-case scenario. Performance factors including solar fraction, collector thermal and exergetic effi-ciencies were evaluated on hourly and daily basis. The simulation results were compared to the experimental results found in the literature and they showed a good agreement. These results proved that the solar water heating system was capable of maintaining reasonable thermal efficiencies of up to 33% and exergetic efficiencies of up to 4% with a daily solar fraction above 58% during the coldest month of the year in the studied location.

... Ahmet Koca a , Hakan F. Oztop b , Tansel Koyun c and Yasin Varol a , Corresponding Author Contact Information , E-mail The Corresponding Author. ... from 1.22 to 2.63 kW, whereas the rate of heat stored in the LHS unit were 111.2 and 79.9 W. Sari and Kaygusuz [11] conducted ...

In this paper a survey of the various types of solar thermal collectors and applications is presented. Initially, an analysis of the environmental problems related to the use of conventional sources of energy is presented and the benefits offered by renewable energy systems are outlined. A historical introduction into the uses of solar energy is attempted followed by a description of the various types of collectors including flat-plate, compound parabolic, evacuated tube, parabolic trough, Fresnel lens, parabolic dish and heliostat field collectors. This is followed by an optical, thermal and thermodynamic analysis of the collectors and a description of the methods used to evaluate their performance. Typical applications of the various types of collectors are presented in order to show to the reader the extent of their applicability. These include solar water heating, which comprise thermosyphon, integrated collector storage, direct and indirect systems and air systems, space heating and cooling, which comprise, space heating and service hot water, air and water systems and heat pumps, refrigeration, industrial process heat, which comprise air and water systems and steam generation systems, desalination, thermal power systems, which comprise the parabolic trough, power tower and dish systems, solar furnaces, and chemistry applications. As can be seen solar energy systems can be used for a wide range of applications and provide significant benefits, therefore, they should be used whenever possible.

Prinsloo, G.J. "Hardware Sun Tracking Systems and Digital Sun Position Hardware Solar Tracker Controllers". In Solar Tracking. GJ Prinsloo. 1st ed. Stellenbosch: SolarBooks, 2016. ISBN 978-0-620-61576-1. doi: 10.13140/2.1.2748.3201
Chapter in free eBook on Solar Tracking Systems, Sun Tracking Systems, Sun Tracker, Solar Tracker, Follow Sun, Sun Position. A number of commercial and proprietary solar tracking controller solutions for a variety of automation platforms are available in the market. These sun tracker solutions include algorithms for computing the sun vector, mostly for PLC (Programmable Logic Controller) and PAC (Programmable Automation Controller) processors as well as FPGA (Field Programmable Gate Arrays). Most of these solar tracking controllers are universal controllers suitable for a variety of solar systems and mode switchable to control point focus, linear (parabolic trough) or central receiver Heliostat solar receiver systems. This chapter aims at giving the reader a wide angle view of available sun tracker solutions and presents some of the solar tracking automation solutions presently available.
Free to download eBook on Practical Solar Tracking Design, following the sun solar tracking system, sun tracking system, sun tracker system, solar tracker system, sun positioning system, and sun path tracking with follow the sun position calculation (azimuth, elevation, zenith), sun trajectory, sun following system, sunrise tracking, sunset tracking, sunlight-phases, dawn, dusk, moon-phase, twilight, moonrise, moonset calculator. Solar Tracking is a key Technology to unlock the full potential of RE in RES.
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Solar Tracking, Sun Tracking, Sun Tracker, Solar Tracker, Follow Sun, Sun Position
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Drying for agricultural and marine products are one of the most attractive and cost-effective application of solar energy. Numerous types of solar dryers have been designed and developed in various parts of the world, yielding varying degrees of technical performance. Basically, there are four types of solar dryers; (1) direct solar dryers, (2) indirect solar dryers, (3) mixed-mode dryers and (4) hybrid solar dryers. This paper is a review of these types of solar dryers with aspect to the product being dried, technical and economical aspects. The technical directions in the development of solar-assisted drying systems for agricultural produce are compact collector design, high efficiency, integrated storage, and long-life drying system. Air-based solar collectors are not the only available systems. Water-based collectors can also be used whereby water to air heat exchanger can be used. The hot air for drying of agricultural produce can be forced to flow in the water to air heat exchanger. The hot water tank acts as heat storage of the solar drying system.

An analysis of the output of the literature scanned in Engineering Index during 1970-84 on solar power research indicates that the growth of the literature had been vigorous after the energy crisis in 1973 till 1982. The number of papers at conferences are quite close to the number of references in journals. The area of solar collectors and solar cells has received maximum attention. Publication output of literature by different countries follows the trend in basic sciences with USA being the major producer. The research activity became global after the energy crisis. Performance of the developed countries is low in some fields of solar power.

Solar Energy Engineering, I am looking to resolve the current situation with the goal of keeping the existing publication record intact. To this end, a discussion containing only your scientific and technical criticism of the following paper can be submitted for publication:

Energy resources and their utilization intimately relate to sustainable development. In attaining sustainable development, increasing the energy efficiencies of processes utilizing sustainable energy resources plays an important role. The utilization of renewable energy offers a wide range of exceptional benefits. There is also a link between exergy and sustainable development. A sustainable energy system may be regarded as a cost-efficient, reliable, and environmentally friendly energy system that effectively utilizes local resources and networks. Exergy analysis has been widely used in the design, simulation and performance evaluation of energy systems.The present study comprehensively reviews exergetic analysis and performance evaluation of a wide range of renewable energy resources (RERs) for the first time to the best of the author's knowledge. In this regard, general relations (i.e., energy, exergy, entropy and exergy balance equations along with exergy efficiency, exergetic improvement potential rate and some thermodynamic parameters, such as fuel depletion ratio, relative irreversibility, productivity lack and exergetic factor) used in the analysis are presented first. Next, exergetically analyzed and evaluated RERs include (a) solar energy systems; (a1) solar collector applications such as solar water heating systems, solar space heating and cooling, solar refrigeration, solar cookers, industrial process heat, solar desalination systems and solar thermal power plants), (a2) photovoltaics (PVs) and (a3) hybrid (PV/thermal) solar collectors, (b) wind energy systems, (c) geothermal energy systems, (c1) direct utilization (district heating, geothermal or ground-source heat pumps, greenhouses and drying) and (c2) indirect utilization (geothermal power plants), (d) biomass, (e) other renewable energy systems, and (f) country based RERs. Studies conducted on these RERs are then compared with the previously ones in tabulated forms, while the Grassmann (or exergy flow) diagrams, which are a very useful representation of exergy flows and losses, for some RERs are given. Finally, the conclusions are presented. It is expected that this comprehensive study will be very beneficial to everyone involved or interested in the exergetic design, simulation, analysis and performance assessment of RERs.