Plataforma Solar De Almeria Research Articles

Analysis of a Solar Office Building at the South of Spain Through Simulation Model Calibration

Prior to construction, the simulation of the thermal behaviour of a building is mandatory in the Spanish Building Technical Code. However, there are few post-occupancy studies for buildings in use implying simulation. In this work, the simulation model developed at the design stage of a Passive Solar Building is fitted/calibrated from experimental measurements. In this work it is also developed a new methodology for simulation model fitting in the context of occupied buildings. A new aspect of the methodology is the link between the experimental design and the model to be fitted. This technique is useful in two ways. First, it allows assessing the relative impact of the a priori model parameter assumtions on the real situation. Second, it permits the quantification of the energy demand reduction due to the Passive Strategies implemented.Results are presented for a Building located at Plataforma Solar de Almería (PSA) facilities, South Spain.

Geometrical Assessment of Solar Concentrators using Close-range Photogrammetry

Solar concentrating technology uses defined reflective surfaces to concentrate beam solar radiation into a receiver through a heat transfer fluid in circulation (i.e. thermal synthetic oil, water/steam, air, molten salt, etc.). These fluids are heated up by the concentrated solar radiation and the thermal energy collected can be used, among other things, to provide thermal energy to industrial processes. Reflective surfaces require a high geometrical precision in order to concentrate the solar radiation onto the receiver, minimizing radiation losses around the receivers. Close-range photogrammetry has been revealed as a highly efficient and precise technique to evaluate the geometrical assessment of solar concentrators. And this task has become essential on the evaluation of the different concentrators used nowadays on solar thermal systems. At the Plataforma Solar de Almería, a set of methods and algorithms based on close-range photogrammetry has been developed on the last years. These methods allow us to evaluate the geometrical quality of solar concentrators. The application of these techniques to different concentrators prototypes, permits us to determine their geometrical, optical and energy behavior as well as to detect improvements on their design. This paper includes the analysis performed to a small parabolic solar concentrator designed for industrial process heat applications.

Modeling of the heat transfer of a solar multi-effect distillation plant at the Plataforma Solar de Almería

Potable water supply by desalination systems has a significant role in today’s developing world. Multi-effect distillation (MED) is a progressing, low cost and easy operating system to produce drinking and pure water for both social and industrial applications. It is very important to understand in detail the process elements in order to determine the effects of the important design and operating variables on the parameters controlling the performance of the plant. A model is developed for the MED plant located at the Plataforma Solar de Almería (PSA), in the southeast of Spain. It is a vertical-arrangement forward-feed MED plant with pre-heaters, which uses hot water as the thermal energy source. The model has been developed dividing the MED plant into four blocks: the heater (consisting of the first effect), the evaporators (consisting of effects 2 to N), the pre-heaters (for effects 1 to N – 1) and the condenser (after effect N). To solve the model, a parameterization of the overall heat transfer coefficient of the four blocks has been carried out with experimental data for a wide range of operation, based on correlations found by other authors for similar plants. The adjustments were good for all the components with the exception of the condenser, which seems to behave differently than in other cases reported in the literature.

Estimate of thermal fatigue lifetime for the INCONEL 625lCF plate while exposed to concentrated solar radiation

A system for testing the thermal cycling of materials and components has been developed and installed at the DISTAL-I parabolic dish facility located at the Plataforma Solar de Almeria (PSA) in Spain. This system allows us to perform abrupt heating/cooling tests by exposing central solar receiver materials to concentrated solar radiation. These tests are performed to simulate both the normal and critical operational conditions of the central solar receiver. The thermal fatigue life for the INCONEL 625LCF® plate when subjected to concentrated solar radiation has been estimated with this system. We have also developed a numerical model that evaluates the thermal behavior of the plate material; additionally, the model yields the tensile-compressive stresses on the plate, which allow the estimation of the Stress-Life (S-N) fatigue curves. These curves show that the lifetime of the plate is within the High Cycle Fatigue (HCF) region at the operational temperatures of both 650 °C and 900 °C.

Optimising position control of a solar parabolic trough

In today’s climate of growing energy needs and increasing environmental concerns, alternatives to the use of non-renewable and polluting fossil fuels have to be investigated. One such alternative is solar energy. This study is based on the implementation of a mathematical computation – the PSA (Plataforma Solar de Almeria) computation developed at PSA (the European Test Centre for solar energy applications) – embedded in a control algorithm to locate the position of the sun. Tests were conducted on a solar parabolic trough (SPT) constructed at the Solar Thermal Applications Research Laboratory of the Mangosuthu University of Technology (Durban, South Africa) for optimal position control using the PSA value. The designed control algorithm embedded in an industrial Siemens S7-314 C-2PtP programmable logic controller compared the PSA computation to a measured position of the SPT to optimally rotate the SPT to a desired position with the constant movement of the sun. The two main angles of the sun relative to the position of the SPT on earth, the zenith angle and the azimuth angle, both calculated in the PSA from the vertical and horizontal planes, respectively, were applied to the control algorithm to generate an appropriate final tracking angle within a 0.007 radian (0° 24′ 3.6″) tolerance, in accordance to the construction specifications and solar collector testing standards of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE, 1991). These values, together with the longitude and latitude applicable to the geographical location of the SPT, were processed in the control software to rotate the SPT to an optimal position with respect to the position of the sun in its daily path, for solar-to-thermal conversion.

The AQUASOL System: Solar Collector Field Efficiency and Solar-Only Mode Performance

Water scarcity is a global problem that will be of capital importance during the first half of this century, when seawater desalination will often be the only way to achieve sustainable development. Despite significant energy efficiency improvements during recent years, seawater desalination is still an intensive energy consumer; therefore, in the current instability of oil prices and environmental requirements, the sustainability of this technological solution inevitably passes through continued improvement of energy efficiency of the physical processes involved, as well as the use of renewable energy resources such as solar energy. In 2006, the “Enhanced Zero Discharge Seawater Desalination Using Hybrid Solar Technology” Project (AQUASOL) concluded with the erection of a complete solar desalination facility at the Plataforma Solar de Almeria (Spain) for the main purpose of developing an improved-cost, energy-efficient multi-effect distillation (MED) solar desalination technology. The system was designed to make the following three desalination operating modes feasible: (a) solar-only: the energy to the first distillation effect comes exclusively from thermal energy from the solar collector field, (b) fossil-only: a double-effect absorption heat pump powered by gas supplies all of the heat required by the distillation plant, and (c) hybrid: the energy comes from both the heat pump and the solar field. In this paper, solar-only mode system performance is presented and discussed. Optimum working conditions achieved in the solar-only mode were in the range of 64–67°C of MED first cell inlet temperature, which implies specific thermal energy consumption from around 58 kW hth/m3 to 62 kW hth/m3 and a performance ratio of 11.1–10.4, respectively.

Connection of absorption heat pumps to multi-effect distillation systems: pilot test facility at the Plataforma Solar de Almería (Spain)

Theoretical analysis demonstrates that coupling a double effect absorption heat pump (DEAHP) cycle to a multi-effect distillation (MED) process shows higher overall performance than other conventional heat pumps like steam ejectors. However, only two demonstration facilities have been implemented worldwide to date, both of them at the Plataforma Solar de Almeria (Spain). The first experience (1992) allowed the expected performance results to be achieved, but some operational problems showed that the technology was not mature enough for its commercial implementation. This paper reports on the assessment of a second heat pump prototype (2005) more successful than the first one. Advances in both the DEAHP unit and design layout of the desalination system as a whole have led to proven reliability of the DEAHP/MED concept, which has an overall performance ratio of 20 with stable and fully automatic operation. It requires a 180°C saturated steam supply which can be provided by solar linear-focusing concentrators. This is a 100% increase over the performance ratio of the MED unit, thus becoming the most efficient solar distillation technology.

Resistance of Fusarium sp spores to solar TiO2 photocatalysis: influence of spore type and water (scaling‐up results)

AbstractBACKGROUND: Common irrigation water disinfection methods, which may be unable to inactivate all types of pathogens or even become phytotoxic themselves, are not very effective in controlling phytopathogens. Water disinfection by photocatalysis is a promising irrigation‐water treatment for destroying phytopathogens without the drawbacks of conventional disinfection methods. Previous research has shown that solar photocatalytic technology can be used in the disinfection treatment of bacteria, protozoa and fungi, either through solar disinfection only. The purpose of this work was evaluate the TiO2 photocatalysis process to inactivate Fusarium spores in distilled and well water.RESULTS: This paper reports on the ability of solar photocatalysis to inactivate Fusarium spores in a solar bottle reactor and in a new 60 L compound parabolic collector (CPC) prototype reactor. Inactivation of Fusarium sp spores by titanium dioxide (Degussa P25) was evaluated in distilled and natural well water. The experiments were carried out using 5 or 6 h exposure to natural sunlight at the Plataforma Solar de Almeria (Southeast Spain). The highest Fusarium spore inactivation rate during experiments was achieved with a 30 L min−1 flow rate and 100 mg L−1 TiO2 concentration. Three different Fusarium spores (microconidia, macroconidia and chlamydospores) were individually evaluated to determine whether there were differences in resistance to the photocatalytic treatment. The results showed that chlamydospores were the most resistant, followed by macroconidia, and finally microconidia were the most sensitive.CONCLUSIONS: Microconidia, macroconidia and chlamydospores in distilled and well water were inactivated with TiO2 slurry in a 60 L CPC photoreactor, demonstrating for the first time that it is possible to scale‐up photocatalytic treatment for use and reuse of water for irrigation. Copyright © 2010 Society of Chemical Industry

Optimization of a solar cooling system with interior energy storage

This paper focuses on the optimization of the performance of a solar absorption cooling system composed by four units with interior energy storage. A full dynamic simulation model that includes the solar collector field, the absorption heat pump system and the building load calculation has been developed. It has been applied to optimize the coupling of a system based on this new technology of solar powered absorption heat pump, to a bioclimatic building recently constructed in the Plataforma Solar de Almeria (PSA) in Spain. The absorption heat pump system considered is composed by four heat pumps that store energy in the form of crystallized salts so that no external storage capacity is required. Each heat pump is composed of two separate barrels that can charge (store energy from the solar field) and discharge (deliver heat or cold to the building) independently. Different configurations of the four units have been analysed taking into account the storage possibilities of the system and its capacity to respond to the building loads. It has been shown how strong the influence of the control strategies in the overall performance is, and the importance of using hourly simulations models when looking for highly efficient buildings.

One-point fitting of the flux density produced by a heliostat

Accurate and simple models for the flux density reflected by an isolated heliostat should be one of the basic tools for the design and optimization of solar power tower systems. In this work, the ability and the accuracy of the Universidad de Zaragoza (UNIZAR) and the DLR (HFCAL) flux density models to fit actual energetic spots are checked against heliostat energetic images measured at Plataforma Solar de Almería (PSA). Both the fully analytic models are able to acceptably fit the spot with only one-point fitting, i.e., the measured maximum flux. As a practical validation of this one-point fitting, the intercept percentage of the measured images, i.e., the percentage of the energetic spot sent by the heliostat that gets the receiver surface, is compared with the intercept calculated through the UNIZAR and HFCAL models. As main conclusions, the UNIZAR and the HFCAL models could be quite appropriate tools for the design and optimization, provided the energetic images from the heliostats to be used in the collector field were previously analyzed. Also note that the HFCAL model is much simpler and slightly more accurate than the UNIZAR model.

Evaluation of operational parameters involved in solar photo-Fenton degradation of a commercial pesticide mixture

Photo-Fenton degradation of a mixture of commercial pesticides typically used in greenhouse agriculture, Vydate ® (10% oxamyl), Metomur ® (20% methomyl), Couraze ® (20% imidacloprid), Ditimur-40 ® (40% dimethoate) and Scala ® (40% pyrimethanil), has been evaluated. The experiments were performed at an original dissolved organic carbon of 200 mg/L (40 mg/L of each commercial pesticide). A battery of degradation studies was carried out under sunlight at the Plataforma Solar de Almeria in a pilot plant specially developed for photo-Fenton applications. Photo-Fenton efficiency gradually rose with temperature. Nevertheless, at 50 °C there was a decrease in efficiency. The influence of Cl − and SO 4 2− between 100 and 2000 and 50 and 500 mg/L, respectively, was also analyzed. A central composite experimental design and its surface response analysis were employed to study the effect of these anions.

Mechanical Properties of Dense Cordierite Discs Sintered by Solar Radiation Heating

Consolidation of cordierite disc specimens was undertaken under concentrated solar beam in a solar furnace at PSA (Plataforma Solar de Almeria). Satisfactory extent of densification was achieved by the present solar-sintering experiment. The mechanical properties measured for the solar-sintered cordierite test pieces were; density p = 2.45 ± 0.02 g/cm 3 , Vickers microhardness HV = 7.31 ± 0.29 GPa, Young's modulus E = 97 ± 5 GPa, shear modulus G = 38 ± 2 GPa, Poisson ratio ν = 0.27 ± 0.01, fracture toughness K IC = 1.50 ± 0.15 MPa·m 1/2 and modulus of rupture evaluated by ring-on-ring test MOR ROR =57.8± 13.7MPa which were comparable to those of the counterparts sintered by conventional industrial gas furnace.

Analyzing Solar Power Plant Performance Through Data Mining

This work is devoted to application of data mining methods for monitoring of state of a solar thermal plant. The methods discussed are illustrated by example of a study performed for the DISS direct steam generation facility at the Plataforma Solar de Almeria (Spain). In order to deal with the problems of large dimensionality and high correlation among the data the methods of latent variables, principal component analysis and partial least squares, were applied. Results showed that normal and abnormal states during plant operation could be identified.

Field Test of Water-Steam Separators for Direct Steam Generation in Parabolic Troughs

Direct steam generation (DSG) represents a promising option to improve today’s parabolic trough technology for solar thermal power generation. The European DISS and INDITEP projects have proven the feasibility of the DSG process under real solar conditions at the DISS test facility at the Plataforma Solar de Almería (PSA) (Zarza, E., Valenzuela, L., Léon, J., Hennecke, K., Eck, M., Weyers, H.-D., Eickhoff, M., 2004, “Direct Steam Generation in Parabolic Troughs Final Results and Conslusions of the DISS Project,” Energy, 29, pp. 635–644). These projects have also shown that the recirculation mode is the preferred operation mode for DSG collector fields. This concept requires water-steam separators at the end of the evaporation section of the collector loop. Both compact water-steam separators for every single row or huge separation drums for the whole collector field are considered. Small compact water-steam separators show a lower inertia, reducing the time for start-up. Within INDITEP and the German R&D project SOLDI compact water-steam separators have been developed, manufactured, and tested by DLR and Siemens, with its subcontractor Framatome ANP. Prototypes of a cyclone and a baffle separator have been implemented into the DISS test facility. More than 200 tests have been performed to investigate the separation efficiency, the pressure loss, and the performance under transient conditions. This paper focuses on the steady-state tests.

Serial grey-box model of a stratified thermal tank for hierarchical control of a solar plant

The ACUREX collector field together with a thermal storage tank and a power conversion system forms the Small Solar Power Systems plant of the Plataforma Solar de Almería, a facility that has been used for research for the last 25 years. A simulator of the collector field produced by the last author has been available to and used as a test-bed for control strategies. Up to now, however, there is not a model for the whole plant. Such model is needed for hierarchical control schemes also proposed by the authors. In this paper a model of the thermal storage tank is derived using the Simultaneous Perturbation Stochastic Approximation technique to adjust the parameters of a serial grey-box model structure. The benefits of the proposed approach are discussed in the context of the intended use, requiring a model capable of simulating the behavior of the storage tank with low computational load and low error over medium to large horizons. The model is tested against real data in a variety of situations showing its performance in terms of simulation error in the temperature profile and in the usable energy stored in the tank. The results obtained demonstrate the viability of the proposed approach.

Environmental green chemistry as defined by photocatalysis

Photocatalysis is efficient in several fields. Firstly, in selective mild oxidation: oxidation of gas and liquid hydrocarbons (alkanes, alkenes, cyclo-alkanes, aromatics) into aldehydes and ketons. Primary and secondary alcohols are also oxidized into their corresponding aldehydes or ketones. The high selectivity was ascribed to a photoactive neutral, atomic oxygen species. Once platinized (only 0.5 wt.% Pt) titania may catalyze reactions involving hydrogen (deuterium-alkane isotopic exchange and alcohol dehydrogenation). For fine chemicals, high initial selectivities enable titania to address most of the twelve principles of “green chemistry”, such as the synthesis of 4- tert-butyl-benzaldehyde, an important intermediate in perfume industry by direct selective oxidation of 4- tert-butyl-toluene with air. A new field recently appeared: thio-photocatalysis. Oxygen was replaced by sulfur, using H 2S as a convenient and reactive source. For instance, the conversion of propene in 1-propanthiol was successfully obtained. The reaction was performed using either CdS or TiO 2. The latter was much more active than CdS. In environmental photocatalysis, titania becomes a total oxidation catalyst once in presence of water because of the photogeneration of OH radicals by neutralization of OH − surface groups by positive holes. Many toxic inorganic ions are oxidized in their harmless upper oxidized state. The total degradation of organic pollutants (pesticides, herbicides, insecticides, fungicides, dyes, etc. …) is the main field of water photocatalytic decontamination. The UVA solar spectrum can de advantageously used as demonstrated by many campaigns performed in the solar pilot plant at the “Plataforma Solar de Almeria” (Spain).

Solid media thermal storage for parabolic trough power plants

For parabolic trough power plants using synthetic oil as the heat transfer medium, the application of solid media sensible heat storage is an attractive option regarding investment and maintenance costs. In the project WESPE that is described in this paper, solid media sensible heat storage materials have been researched. Two storage systems with a storage capacity of about 350 kW h each and maximum temperatures of 390 °C have been developed. The test storage units of WESPE are erected at the Plataforma Solar de Almeria in Spain. The thermal energy is provided by a parabolic trough loop with a maximum thermal power of 480 kW. The first tests were performed at storage temperatures up to 325 °C by March of 2004; testing will be continued during 2004 to achieve the nominal operation conditions of 390 °C and to gain experience for long term behaviour. These storage systems are composed of modules with two different storage materials to identify the characteristics of these materials. A tubular heat exchanger is integrated into the storage material. This heat exchanger demands a significant share of the investment costs. The selection of geometry parameters like tube diameter and number of tubes therefore play an important role in the optimisation. The design of the WESPE test module is based on results provided by a numerical tool for simulation of the transient performance of storage systems.

06/01729 Behaviour of new refrigerant mixtures under magnetic field: Sami, S. M. and Kita, R. J. International Journal of Energy Research, 2005, 29, (13), 1205–1213

This paper presents the application of multi-output ARX (Auto-Regression with eXtra inputs) models to estimation of the U values of building components tested outdoors. Multi-output models make it possible to take interaction of the physical quantities involved in the process analysed into account. This approach has been used to analyse two quite different building components. The tests were carried out in one of the PASSYS test cells at the CIEMAT’s “Plataforma Solar de Almería (PSA)” in Tabernas (Almería, Spain). Several data sets were studied for each of these components using multi-output and single-output models, as well as theoretical values, and the results were compared. Very good performance of the multi-output models was observed for the samples analysed.

PSA Solar furnace: A facility for testing PV cells under concentrated solar radiation

Abstract The Plataforma Solar de Almeria (PSA), the largest centre for research, development and testing of concentration solar thermal technologies in Europe, has started to apply its knowledge, facilities and resources to development of the Concentration PV technology in an EU-funded project HiConPV. A facility for testing PV cells under solar radiation concentrated up to 2000× has recently been completed. The advantages of this facility are that, since it is illuminated by solar radiation, it is possible to obtain the appropriate cell spectral response directly, and the flash tests can be combined with prolonged PV-cell irradiation on large surfaces (up to 150 cm 2 ), so the thermal response of the PV cell can be evaluated simultaneously.

High meta-stability of tungsten sub-carbide W2C formed from tungsten/carbon powder mixture during eruptive heating in a solar furnace

At around 1600 °C, stable phase in W–C binary system being in equilibrium with excess carbon is acknowledged to be mono-carbide WC. Nevertheless, during carbide formation from mixed powders of tungsten and excess carbon (C/W atom ratio: 2) in inert Ar gas environment, sub-carbide W2C formed besides mono-carbide WC when the heating was done extremely rapidly (instant temperature rise to 1600 °C from ambient temperature within fractions of a second) in a solar furnace at PROMES-CNRS in Odeillo (France) and the formed W2C resisted to be converted fully to WC even after 30 min heating at a temperature exceeding 2500 °C in Ar gas. Under comparatively fast heating condition (heating from ambient temperature to 1600 °C in about 1 min) realised in a solar furnace at PSA (Plataforma Solar de Almeria) in Tabernas (Spain), equilibrium phase WC alone formed from the similar starting material (C/W atom ratio: 1.5). Consideration is given for the formation mechanism of W2C under the eruptive heating condition in the solar furnace at PROMES-CNRS and also for the meta-stability of the formed W2C phase.