Hybrid solar - biomass plants for power generation; technical and economic assessment
Environmental, economic and strategic reasons are behind the rapid impulse in the deployment of renewable energy sources that is taking place around the world. In addition to overcoming economic and commercial barriers, meeting the ambitious objectives set by most countries in this field will require the development of novel technologies capable of maximizing the energy potential of different renewable sources at an acceptable cost. The use of solar radiation and biomass for power generation is growing rapidly, particularly in areas of the globe where these resources are plentiful, like Mediterranean countries. However, solar energy plants necessarily suffer from the intermittency of day/night cycles and also from reduced irradiation periods (winter, cloudy days, and short transients).
Biomass power plants have to confront the logistic problems associated with the continuous supply of very large amounts of a relatively scarce and seasonal fuel. Hybrid systems may provide the solution to these limitations, maximizing the energy potential of these resources, increasing process efficiency, providing greater security of supply and reducing overall costs.
This work provides a practical introduction to the production of electricity from conventional Concentrating Solar Power (CSP) and biomass power plants, which is used as the basis to evaluate the technical and economic benefits associated with hybrid CSP-biomass energy systems. The paper initially analyses alternative configurations for a 10 MWe hybrid CSP- biomass combustion power plant. The Solar Advisor Model (SAM) was used to determine the contribution of the solar field using quasi-steady generation conditions. The contribution of the biomass and gas boiler to the power plant was estimated considering the available radiation throughout the year. An economic assessment of a 10 MWe power plant based on conventional CSP, biomass combustion and hybrid technology is calculated. The results show that investment costs for hybrid CSP- biomass power plants are higher than for conventional CSP and biomass combustion plants alone. However, owing to the shared use of some of the equipment, this value is significantly lower (24% saving) than a simple addition of the investment costs associated with the two standard technologies. In contrast, effective operating hours and, therefore, overall energy generation, are significantly higher than in conventional CSP (2.77 times higher) and avoids the need for highly expensive heat storage system.
Owing to the lower biomass requirements, hybrid plants may have larger capacities than standard biomass combustion plants, which implies higher energy efficiencies and a reduced risk associated with biomass supply. Universidad Politécnica de Madrid (UPM) is currently collaborating with a consortium of private companies in the development of a first commercial
Analysis of the evolution in biomass to energy
Global warming is one of the most serious challenges facing humankind as it has the potential to dramatically modify the living conditions of future generations. In order to reduce the emission of greenhouse gases, most countries are implementing regulations aimed at reducing their dependence on fossil fuels, promoting energy efficiency practices and favoring the deployment of low carbon energy technologies, including renewable energy sources. In line with the international commitments assumed as a member of the European Union (EU) and also as a signatory of the Kyoto Protocol, Spain developed a National Plan for Renewable Energies (PER 2005-2010) that forms the basis of the national strategy in this field. Spain has often been cited as an example for the rapid growth in the use of low carbon energy technologies. However, despite significant progress in the last decade, Spain is far from meeting the national objectives set in PER primarily due to slow growth in the demand for biofuels and the limited success of biomass fired power plants. The evolution in other energy technologies has been faster, situating Spain as world a leader in solar and wind energy. However, the contribution of these technologies to the national consumption is very marginal. In the midst of intense regulatory, commercial and R&D activity, this paper analyses the current situation with respect to the production of renewable energies in Spain, focusing primarily on the use of biomass resources. The paper offers a general view of policy and regulatory background, illustrates current progress towards meeting national objectives and provides a brief description of representative projects and market activity in biofuel production and biomass valorization. Current situation with respect to the production of renewable energies in Spain, focusing primarily on the use of biomass resources. The paper offers a general view of policy and regulatory background, illustrates current progress towards meeting national objectives and provides a brief description
Analysis and optimization of ventilation systems for an underground transport interchange building under regular and emergency scenarios
The work and conclusions gained from the analysis of five new underground interchange buildings ongoing in Madrid, Spain, is presented. An additional study was performed for a typical two-level interchange building, and the methodology and results are presented in this paper.
First, different ventilation and air conditioning strategies have been analyzed. The main goal is to find the most efficient design in order to maintain pollutants concentration and temperatures below the designed values, at minimum investment and operation costs. Different strategies have been modeled and compared using a Computational Fluid Dynamics (CFD) code, taking into account the buses circulation and the different pollution and heat sources. The final solution developed is based on a physical separation between the island area and the dock area. Conclusions on the efficiency of the different design strategies and possible pitfalls are presented.
Secondly, different fire scenarios are analyzed. The main goal is to check whether the firefighting measures planned, such as mechanical ventilation and a curtains system to define smoke sectors are able to cope with a fire emergency situation. A model for the bus fire has been developed, including heat release and smoke production. The main results presented are temperature fields, visibility and smoke concentration.
The development of hybrid solar - biomass plants for the production of renewable energy; technical and economic assessment
Owing to environmental, economic and strategic considerations, the use of renewable energies is being promoted all around the world. In addition to overcoming economic and commercial barriers, meeting the ambitious objectives set by most countries will require the development of novel technologies capable of maximizing the energy potential of different renewable sources. Solar and biomass derived energy is increasingly being used for the generation of electricity. However, solar energy plants necessarily suffer from the intermittency of the day/night cycles and reduced irradiation periods (winter, cloudy days), and biomass power plants have to confront the logistics associated with the continuous supply of very large amounts of a relatively scarce and seasonal fuel. The development of hybrid solar-biomass power plants may provide the answer to these limitations, maximizing the energy potential of these resources, increasing process efficiency, providing greater security of supply and reducing overall costs.
This work provides a general assessment of technical, economic and environmental aspects associated with the production of electricity from existing Concentrating Solar Power (CSP) and biomass power plants. The paper also analyses alternative configurations for a 10 MWe hybrid CSP- biomass combustion power plant currently under development at Universidad Politécnica de Madrid (UPM). The results show that investment costs for hybrid CSP- biomass power plants are higher than for conventional CSP and biomass combustion plants alone. However, owing to the shared use of some of the equipment, this value is significantly lower (24% saving) than a simple addition of the investment costs associated with the two standard technologies. In contrast, effective operating hours and, therefore, overall energy generation, are significantly higher than in conventional CSP (2.77 times higher) and avoids the need for highly expensive heat storage system. Owing to the lower biomass requirements, hybrid plants may have larger capacities than standard biomass combustion plants, which implies higher energy efficiencies and a reduced risk associated with biomass supply.
Criterios geotectónicos para el emplazamiento de plantas termo-solares de producción de electricidad en el área iberomagrebí
La zona sur de la península Ibérica y el norte de áfrica presentan un gran potencial para la producción de electricidad mediante energía solar térmica. Un gran número de instalaciones de producción de energía solar térmica se están instalando o se encuentran en fase de proyecto en esta zona.
Estas instalaciones de energía solar, ya sean concentradores de tipo torre o de tipo cilindro parabólico, necesitan de una precisión milimétrica en la alineación de sus diferentes componentes para lograr una alta eficiencia en la producción de energía térmica.
Los terremotos en esta zona no están concentrados en un área estrecha, sino que se extienden sobre una zona amplia desde el norte de España y los Pirineos hasta el Atlas Sahariano. La sismicidad está caracterizada por una actividad continua de eventos de magnitud baja a moderada (M<5) y algunos eventos de mayor magnitud en intervalos de tiempo mucho mayores, que en algunas ocasiones ha llegado a destruir poblaciones por completo, lo que en una central de este tipo podría suponer la pérdida de buena parte de la inversión.
En este artículo se estudian las consecuencias que un sismo de diferentes intensidades tendrían sobre las distintas partes de estas instalaciones solares.
Design and construction of an experimental molten salts test loop
Benefits of thermal storage systems in Solar Thermal Power Plants are well known . Although molten-salt thermal storage systems are already being commercially implemented, experience and standard procedures to qualify and evaluate components and charge/discharge processes for this type of storage system are still needed. To assist in solving these problems, CIEMAT signed a turn-key contract to have at the PSA an experimental plant for thermal storage using molten salts. This molten salt plant was designed to evaluate components, instrumentation and operation strategies. The plant was designed to be fed by either a high-temperature or mid-temperature energy source. The plant components are large enough to allow the extrapolation of results to large commercial power plants, and sufficiently flexible to cover a wide range of research activities.
The most remarkable aspects regarding design and construction of this experimental plant are explained in this paper. Also straightforward recommendations are given in the paper to be taken into account during the design and construction of molten-salt thermal storage systems.
First experimental results of a solar ptc facility using gas as the heat transfer fluid
Parabolic Trough Collector (PTC) solar power plants have previously been designed to use thermal oil (mineral or synthetic) or, more recently, water as the heat transfer fluid (HTF). The purpose of this experimental facility at the Plataforma Solar de Almería (PSA) is to prove the feasibility of a pressurized gas as the HTF, in this case CO2, as proposed by Professor Carlo Rubbia. Facilities using such an innocuous gas have the advantages of being clean, safe, and simple to operate, with no fluid temperature limitations.
The experimental facility consists of two 50-m Parabolic Eurotrough Collectors connected to a blower that propels the gas, and to an air cooler for heat exhaust into the atmosphere.
To demonstrate the feasibility of the control system, and at the same time investigate the possibilities of scaling up to a commercial plant, the experimental plant can be operated with collectors connected either in parallel or in series.
As the conditions of direct solar irradiation change with the time of day and with the weather conditions, facility control must vary the gas flow rate to maintain an almost constant temperature at the collector outlet.
Another significant plant component is the air cooler, which simulates the presence of a commercial power block, and controls the collector gas inlet temperature.
This paper presents and discusses the first experimental results and corresponding conclusions regarding its control feasibility. The leaks problem that have appeared in the rotating joints is stated as well as the pros and cons of using CO2 as heat transfer fluid. Finally, some results of the performed tests are given.
Cladding of Ni superalloy powders on AISI 4140 steel with concentrated solar energy
The Present work deals with Ni alloy cladding on AISI 4140 steel samples made with high power density concentrated solar beams. The quality of the cladding is high concerning the adherence, low dilution and high hardness of the coating. Some considerations are presented concerning the future of high power density beams related to surface modification of metallic materials with Solar Energy
Catalytic acceleration of graphitization of amorphous carbon during synthesis of tungsten carbide from tungsten and excess amorphous carbon in a solar furnace
Amorphous carbon is one of the allotropes of carbon possessing carbon activity a(C) higher than that of graphite (standard state with a(C) . 1). Amorphous carbon is in a metastable state but, under normal circumstances, it takes several hours to be graphitized to an extent detectable by X-ray diffraction even at temperature higher than 15008C. In the present work, we report the accelerated graphitization of amorphous carbon induced apparently by the catalytic action of tungsten (W) or tungsten carbide (WC) during synthesis of WC started from Wand active carbon in solar furnace under controlled atmosphere (Ar or N2). This degree of graphitization of amorphous carbon didnot proceed by the similar reaction undertaken in the traditional laboratory furnace under the comparable conditions. # 1999 Elsevier
X-ray diffraction characterization of carbide and carbonitride of Ti and Zr prepared through reaction between metal powders and carbon powders (graphitic or amorphous) in a solar furnace
Carbide formation of Va-group metals (V, Nb and Ta) in a solar furnace
In our recent series of solar carbide synthesis for Si and d-group transition metals (Ti, Zr; Cr, Mo, W) using graphite (G) or amorphous carbon (aC) as carburizing medium, we observed some evidences indicative of involvement of photochemical effects in the reaction process. For example, (1) graphitization of aC was accelerated during carburization of W under solar radiation; (2) high-temperature mono-carbide phase of Mo (a-MoC1yx) formed at a temperature appreciably lower than the lower-threshold temperature of the stability range of the a-MoC1yx phase given in the available equilibrium phase diagram for Mo+C system. In this work, we investigated solar carburization reactions for Va-group metals (V, Nb, Ta) in Ar or N2 gas environment. For this group of metals, only carbide phases formed even in N2 atmosphere without forming carbonitride like the cases with VIa-group metals (Cr, Mo, W). For carburization of Ta with aC in Ar, an unexpected formation of sub-carbide Ta2C besides mono-carbide TaC took place, while Ta2C phase did not form through carburization of Ta with aC in N2 or carburization of Ta with G in either Ar or N2 atmosphere. No graphitization promotion for aC was detected during the carburization of none of the Va-group elements.
Photochemically promoted formation of higher carbide of molybdenum through reaction between metallic molybdenum powders and graphite powders in a solar furnace
At temperatures between 1190°C and 1655°C, stable phase of Mo+C system is a hexagonal sub-carbide b-Mo2C and, at temperature lower than 1190°C, an orthorhombic sub-carbide a-Mo2C. Hypo-stoichiometric mono-carbide phase MoC1yx (0 < x < 0.5) exists only at temperatures higher than 1655°C in reported equilibrium Mo+C phase diagram; a complex hexagonal a-MoC1yx up to 1960°C and a face centered cubic (fcc) b-MoC1yx between 1960°C and 2580°C (melting temperature). By reaction between Mo and graphite in a solar furnace, hexagonal mono-carbide a-MoC1yx formed in 30 min at 1600 . 20°C. This evidence seems to indicate occurrence of some photochemical reaction promotion towards formation of higher carbide of Mo at comparatively low temperature by the heating with solar beam.
Photochemical Effects in Carbide Synthesis of d-group Transition Metals (Ti, Zr; V, Nb, Ta; Cr, Mo, W) in a Solar Furnace at PSA (Plataforma Solar de Almería)
During the course of our recent series of solar carbide and carbonitride synthesis work for d-group transition elements (Ti,Zr;V,Nb,Ta;Cr,Mo,W), we detected several intriguing evidences apparently indicative of involvement of photochemical effects in some reactions under solar radiation. 1) Acceleration of graphitization of amorphous carbon during carburization of W under solar radiation. 2) Promoted formation of high temperature mono-carbide phase of Mo under solar radiation at a temperature lower than the one indicated in equilibrium phase diagram. 3) Formation of sub-carbide Ta2C besides mono-carbide TaC in the carburization of Ta with amorphous carbon under solar radiation.
Only mono-carbide TaC formed by the carburization of Ta with graphite under solar radiation in accordance with the equilibrium phase diagram. These features were already published individually elsewhere. This article is the brief summary of the reported facts in our earlier publications. Although the results so-far-obtained are rather primitive and still lacking quantitative characterization, there seems to be no doubt that solar materials processing would open new routes for unique products which cannot be prepared through traditional industrial manufacturing processes. @DOI: 10.1115/1.1350565#
Beam Characterization and Improvement with a Flux Mapping System for Dish Concentrators
A flux mapping system able to measure the flux distribution of dish/Stirling systems in planes perpendicular to the optical axis was built and operated at the Plataforma Solar de Almería (PSA). It uses the indirect measuring method with a water-cooled Lambertian target placed in the beam path and a CCD-camera mounted on the concentrator taking images of the brightness distribution of the focal spot. The calibration is made by calculating the total power coming from the dish and relating it to the integrated gray value over the whole measurement area. The system was successfully operated in a DISTAL II stretched membrane dish and in the new EURODISH in order to characterize their beams and improve the flux distribution on their receivers. @DOI: 10.1115/1.1464881#
Characterization of solar-synthesized TiCx (x = 0.50, 0.625, 0.75, 0.85, 0.90 and 1.0) by X-ray diffraction, density and Vickers micro-hardness
Homogeneous single-phase hypo-stoichiometric carbide TiCx of titanium with known stoichiometric ratio x (0.50, 0.625, 0.75, 0.85, 0.90 and 1.0) was prepared from mixed powders of Ti metal and graphite through 30 min solar heating in inert Ar atmosphere and characterized by X-ray diffraction (XRD), density ? and Vickers micro-hardness Hv. In spite of short radiation period at relatively low temperature (no higher than 1600 ?C), formed TiCx specimens were all with relatively high degree of crystallinity judging from good separation between K_1 and K_2 peaks of XRD patterns at high (h k l) index. Measured density of prepared TiCx powders was practically identical to the calculated value from the measured lattice parameter for respective x implying that f.c.c. (face centered cubic) Ti lattice was with no defect and 100x% of the O-sites (octahedral interstitial sites) were filled with C atoms leaving the rest 100(1-x)% of O-sites vacant. Reflecting polycrystalline nature of the prepared TiCx compact, measured Hv scattered over range of +400 around 1100. Application of 50 h heat treatment at 600 ?C appeared to realise C atoms ordering re-configuration over O-sites leading to slight extent of tetragonal distortion for TiCx specimens with x = 0.50 and 0.625. ® 2002 Elsevier Science B.V. All rights reserved.
Leaching Characteristics of Mercury Mine Wastes Before and After Solar Thermal Desorption
Mercury mine waste contains other toxic metals in addition to Hg, such as Ag, Cd, Cu, Ni, Pb, Fe, Mn, As, and Sb, which may contribute to environmental pollution. Leaching characteristics of mine waste treated by solar thermal desorption were studied, and removal and mobilization processes were evaluated. Concentrations of Cd, Ni, and Pb in mine waste leachates before thermal treatment do not exceed the limits in European standards, and after the treatment, their concentration decreased significantly in some samples. Hg is the only metal with concentrations above the European leaching limits, although, in the treated samples, the concentrations of dissolved Hg decreased significantly, showing the effectiveness of the thermal treatment. Thus, in the mining wastes sample AS, Hg concentrations decreased from 1100 lg/L in the original sample to 73 lg/L in the treated sample, although this concentration is above the European leachate concentration levels (30 lg/L). In the calcine sample M03, Hg leached only decreased from 13 to 9 lg/L in the treated sample, although when characterized by percolation experiments, these levels were below the European leachate limits for nonhazardous solid-waste landfills. In the soil samples M02 and BS, the Hg leaching showed an opposite behavior, indicating in the Azogue soil sample M02 that the Hg concentration decreased from 66 to 6 lg/L in the treated sample, while in the Bayarque soil sample BS, the concentration of leached Hg increased from 9 to 51 lg/L in the treated sample.
Results of geochemical modeling showed that the dominant species in the leachates of the untreated samples were HgClOH, Hg(OH)2, HgCl2, HgCl3 - , and Hg0, which was in agreement with the high Hg and chloride concentrations in some leachates. In the leachates of the treated samples, the dominant species were Hg0, Hg(OH)2, HgClOH, and HgCl2.
Tratamiento superficial de materiales mediante luz solar concentrada: una opción mediante energías renovables
En este artículo se explica de manera ilustrativa la posible aplicación de los hornos solares al tratamiento superficial de materiales. Se realiza una breve descripción de estos sistemas y se da un repaso a las posibles aplicaciones industriales o de ensayo para las que se ha demostrado su aptitud.
Feasibility of concentrated solar energy utilization in copper sintering process
Sintering processes as well as all industrial processes depend on conventional energies. This work tries to demonstrate the feasibility of the application of a renewable power source, as Thermal Solar Energy, in copper sintering. In order to evaluate in the future driving forces and transported material path according to characteristics of the system and the incident radiation, different experimental devices based on ideal particle models, cylinders in this case, were designed to simplify the real system geometry based on compact powders. These devices were evaluated in the Plataforma Solar de Almería (PSA) Solar Furnace. Later analysis of the test pieces showed the feasibility of sintering copper in solar furnaces, the test pieces, treated in slightly reducing atmosphere, have developed well-defined necks and reduced porosity, which are typical characteristics of sintering.
Application of solar thermal desorption to remediation of mercury-contaminated soils
Solar thermal desorption at temperatures up to 500 _C is an innovative technology applied to the removal of mercury and arsenic from soil polluted by mining operations. As the soil is heated in a low and high-temperature solar system, the pollutant vapor pressure rises, producing mass transfer to the gas phase, which is then extracted by vacuum pumps and blower systems. In the UPC low-temperature experiments, removal of mercury from the polluted soil was as much as 76%. The experimental results show that volatilization of mercury is only significant when the temperature is above approximately 130 _C, which agrees with the predominant mercury solid phases detected. PSA middle-temperature experiments, showed that when soil and mine waste samples were heated to 400-500 _C, mercury elimination was significant (41.3-87%). However, the results from heating to 320 _C or below 300 _C, indicated little or negligible removal, possibly, because the fluid dynamics in the fluidized-bed module and the presence of cinnabar and pyrite rich-Hg as dominant mineral phases.
These results show the potential for efficiently removing mercury and other pollutants from solid matrices (soil, waste, etc.) at low temperatures.
Mechanical Properties of Dense Cordierite Discs Sintered by Solar Radiation Heating
P.O. Box 22, 04200 Tabernas Spain 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 _ ¼ 2:45 _ 0:02 g/cm3, Vickers micro-hardness HV ¼ 7:31 _ 0:29 GPa, Young's modulus E ¼ 97 _ 5 GPa, shear modulus G ¼ 38 _ 2 GPa, Poisson ratio _ ¼ 0:27 _ 0:01, fracture toughness KIC ¼ 1:50 _ 0:15 MPa_m1=2 and modulus of rupture evaluated by ring-on-ring test
Metallic and carbonaceous ebased catalysts performance in the solar catalytic decomposition of methane for hydrogen and carbon production
Solar catalytic decomposition of methane (SCDM) was investigated in a solar furnace facility with different catalysts. The aim of this exploratory study was to investigate the potential of the catalytic methane decomposition approach providing the reaction heat via solar energy at different experimental conditions. All experiments conducted pointed out to the simultaneous production of a gas phase composed only by hydrogen and un-reacted methane with a solid product deposited into the catalyst particles varying upon the catalysts used: nanostructured carbons either in form of carbon nanofibers (CNF) or multiwall carbon nanotubes (MWCNT) were obtained with the metallic catalyst whereas amorphous carbon was produced using a carbonaceous catalyst. The use of catalysts in the solar assisted methane decomposition present some advantages as compared to the high temperature non-catalytic solar methane decomposition route, mainly derived from the use of lower temperatures (600e950 _C): SCDM yields higher reaction rates, provides an enhancement in process efficiency, avoids the formation of other hydrocarbons (100% selectivity to H2) and increases the quality of the carbonaceous product obtained, when compared to the non-catalytic route.