Examinando por Autor "Zaragoza, Guillermo"
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Publicación Assessment of different configurations for combined parabolic-trough (PT) solar power and desalination plants in arid regions(Elsevier, 2011-08) Palenzuela, Patricia; Zaragoza, Guillermo; Alarcón-Padilla, Diego C; Blanco, Julián; Guillén, Elena; Ibarra Mollá, Mercedes; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0003-4145-9224The combination of desalination technology into concentrating solar power (CSP) plants needs to be considered for the planned installation of CSP plants in arid regions. There are interesting synergies between the two technologies, like the possibility of substituting the condenser of the power cycle for a thermal desalination unit. This paper presents a thermodynamic evaluation of different configurations for coupling parabolic-trough (PT) solar power plants and desalination facilities in a dry location representing the Middle East and North Africa (MENA) region. The integration of a low-temperature multi-effect distillation (LT-MED) plant fed by the steam at the outlet of the turbine replacing the condenser of the power cycle has been simulated and compared with the combination of CSP with a reverse osmosis (RO) plant. Furthermore, an additional novel concept of concentrating solar power and desalination (CSP+D) has been evaluated: a LT-MED powered by the steam obtained from a thermal vapour compressor (TVC) using the exhaust steam of the CSP plant as entrained vapour and steam extracted from the turbine as the motive vapour of the ejector. This new concept (LT-MED-TVC) has been analyzed and compared with the others, evaluating its optimization for the integration into a CSP plant by considering different extractions of the turbine.Publicación Comparative evaluation of two membrane distillation modules(Elsevier, 2011-07) Guillen Burrieza, Elena; Blanco Gálvez, Julián; Alarcón Padilla, Diego C.; Zaragoza, Guillermo; Palenzuela, Patricia; Ibarra Mollá, Mercedes; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-8044-969XFreshwater shortage difficulties make it necessary to find new sources of supply. Nowadays desalination is the solution adopted in many countries to solve this problem. All around the planet, regions with lack of freshwater match up with those with large amounts of available solar radiation. Therefore, solar desalination can be a suitable and sustainable option to tackle the water scarcity problems in those particular areas, especially in the coastal ones. Membrane distillation (MD) is a thermal membrane technology developed since late 60’s which uses low exergy heat to drive a separation process in aqueous solutions. One of its applications is desalination where thanks to its separation principle, very high distillate quality can be obtained. MD is a thermally driven process that differs from other membrane technologies in that its driving force, rather than the total pressure, is the difference in water vapour pressure across the membrane, caused in turn by a temperature difference between the cold and the hot side of it. In comparison with other membrane-based desalination processes like reverse osmosis (RO), MD shows very high rejection rates and much lower operational pressures, also the nature of MD membranes (larger pore sizes than RO) makes them much less sensitive to fouling. Compared to conventional thermal desalination processes like MSF or MED, MD is less demanding regarding vapor space and building material’s quality [1] leading to potential lower construction costs. Amongst its advantages, its low operating temperatures (ranging between 60–90°C [2]) make possible the use of low-grade heat, the kind of energy delivered by static solar collectors, as the only thermal supply. This, jointly with its low operational pressure and small footprint, make solar membrane distillation (SMD) in principle, a promising technology. Despite these advantages, SMD has been developed to a lesser extent, compared with other solar desalination technologies like PV-driven RO or solar stills, and although many encouraging laboratory experiences can be found in literature, large-scaling and module design is still an issue. It is precisely because of this preliminary state MD is in, that very preliminary, low energy efficiency and not commercial available MD prototypes are still found. In MD there is still a trade-off between efficiency (heat consumption) and production (distillate per square meter of membrane), as a result very high specific distillate fluxes can be attained (up to 80 kg h–1 m–2 of membrane [3]) but heat losses (mainly trough the membrane by conduction) are still substantial. Under the framework of an European project (MEDESOL: Seawater Desalination by Innovative Solar Powered Membrane Distillation) which main objective was to develop a stand-alone desalination system based on multi stage MD to supply decentralized rural areas [4], the status and future possibilities of currently developed MD have been evaluated. This paper presents the results obtained from the experiments realized with two different pre-commercial MD modules, coupled to a solar field comprised of static collectors. Both modules were tested in the same facility under the same conditions, in order to make a reliable comparison between them. Data on energy efficiency, production ratios and operational issues will be shown.Publicación Experimental analysis of an air gap membrane distillation solar desalination pilot system(Elsevier, 2011-09) Guillén Burrieza, Elena; Blanco, Julián; Zaragoza, Guillermo; Alarcón, Diego-César; Palenzuela, Patricia; Ibarra Mollá, Mercedes; Gernjak, Wolfgang; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0001-9859-2435; https://orcid.org/0000-0003-3317-7710Freshwater shortage difficulties make it necessary to find new sources of supply. Nowadays desalination is the solution adopted in many countries to solve this problem. All around the planet, regions with lack of freshwater match up with those with large amounts of available solar radiation. Therefore, solar desalination can be a suitable and sustainable option to tackle the water scarcity problems in those particular areas, especially in the coastal ones where the majority of human population lives. Membrane distillation (MD) is a thermal membrane technology developed since late 60´s which uses low exergy heat to drive a separation process in aqueous solutions. One of its applications is desalination where thanks to its separation principle, very high distillate quality can be obtained. Amongst its advantages, its low operating temperatures, ranging between 60-90º C [Lawson and Lloyd, 1997] make possible the use of low-grade heat, the kind of energy easily delivered by static solar collectors, as the only thermal supply. This, jointly with its low operational pressure and small footprint, make MD coupled with solar energy (Solar Membrane Distillation) in principle, a promising technology. Under the framework of a European project (MEDESOL Project) funded by the European commission, an innovative desalination system based on solar air gap membrane distillation has been investigated. The system is intended to be technically simple to operate, robust and able to cover water demands of small settlements. The experimental set-up was built at Plataforma Solar de Almería facilities (leading partner) and tested during 4 months. The desalination system consists of a three MD desalination modules system supplied with the thermal energy of a static collector’s solar field. Desalination and solar circuits are connected through a plate heat exchanger especially coated to withstand hot seawater operational conditions. The system was run during solar hours (as the layout doesn’t contemplate heat storage) and the experiments were designed to characterize the system. The overall performance of the system was evaluated with both tap water and a 35 g L-1 NaCl aqueous solution. The distillate production and quality were evaluated as a function of the operational parameters, as well as the thermal consumption and specific desalination parameters such as performance ratio (PR). The system can work at temperatures up to 95ºC on the hot feed side and up to 60 ºC on the refrigeration side. This paper will show the experimental results as well as the operational experiences of the system.Publicación Modeling of the heat transfer of a solar multi-effect distillation plant at the Plataforma Solar de Almería(Elsevier, 2011-07) Palenzuela, Patricia; Alarcón, Diego; Blanco, Julián; Guillén, Elena; Ibarra Mollá, Mercedes; Zaragoza, Guillermo; https://orcid.org/0000-0001-8044-969X; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0001-7329-380X; https://orcid.org/0000-0003-4145-9224; https://orcid.org/0000-0002-4452-9980Potable 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.Publicación Parametric equations for the variables of a steady-state model of a multi-effect desalination plant(Taylor and Francis Group, 2012-07-10) Palenzuela, Patricia; Alarcón, Diego; Zaragoza, Guillermo; Blanco, Julián; Ibarra Mollá, MercedesIn the present work a steady-state model is developed of an MED plant. Its development and validation have been carried out by experimental data obtained from an MED pilot 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. In order to run the model a series of parametric equations for these variables: the overall heat transfer coefficient for the first effect (Uh), the overall heat transfer coefficient for the pre-heaters (Up(i)), the vapor temperature inside the first effect, (Tv(1)) and the cooling seawater outlet temperature (Tcwout) have been determined. They have been obtained from a three-level factorial experimental design (3k), performing a total of 81 experiments (34). The results obtained showed a good fit to the estimated models for the response variables.Publicación Performance of a 5 kWe solar-only organic Rankine unit coupled to a reverse osmosis plant(Elsevier, 2014) Ibarra Mollá, Mercedes; Rovira de Antonio, Antonio José; Alarcón Padilla, Diego C.; Zaragoza, Guillermo; Blanco Gálvez, Julián; https://orcid.org/0000-0002-8843-8511; https://orcid.org/0000-0002-4452-9980; https://orcid.org/0000-0001-7329-380XOrganic Rankine Cycle (ORC) systems are one of the most promising energy conversion technologies available for remote areas and low temperature energy sources. An ORC system works like a conventional Rankine cycle but it uses an organic compound as working fluid, instead of water. A small ORC unit coupled with a solar thermal energy system could be used to convert solar thermal energy into electricity in remote areas, offering an alternative to Photovoltaic (PV) systems to provide the energy required by desalination applications like reverse osmosis (RO). In this work an analysis of the performance of a specific solar desalination ORC system at part load operation is presented, in order to understand its behavior from a thermodynamic perspective and be able to predict the total water production with changing operation conditions. The results showed that water production is around 1.2 m3/h, and it is stable during day and night thanks to the thermal storage and only under bad irradiance circumstances the production would stop.