Techno-Economic Analysis of Rural 4th Generation Biomass District Heating

Biomass heating networks provide renewable heat using low carbon energy sources. They can be powerful tools for economy decarbonization. Heating networks can increase heating efficiency in districts and small size municipalities, using more efficient thermal generation technologies, with higher efficiencies and with more efficient emissions abatement technologies. This paper analyzes the application of a biomass fourth generation district heating, 4GDH (4th Generation Biomass District Heating), in a rural municipality. The heating network is designed to supply 77 residential buildings and eight public buildings, to replace the current individual diesel boilers and electrical heating systems. The development of the new fourth district heating generation implies the challenge of combining using low or very low temperatures in the distribution network pipes and delivery temperatures in existing facilities buildings. In this work biomass district heating designs based on third and fourth generation district heating network criteria are evaluated in terms of design conditions, operating ranges, effect of variable temperature operation, energy efficiency and investment and operating costs. The Internal Rate of Return of the different options ranges from 6.55% for a design based on the third generation network to 7.46% for a design based on the fourth generation network, with a 25 years investment horizon. The results and analyses of this work show the interest and challenges for the next low temperature DH generation for the rural area under analysis

The calcium-looping process for advancing in the development of both C02 capture and thermochemical energy storage systems.

The Calcium-Looping process is based on the multicycle calcination-carbonation of calcium carbonate, which is one of the most abundant materials in the Earth. The process shows promising results facing to solve two of the main challenges within the future energy scenario: CO2 capture from fossil fuel combustion processes and energy storage in renewable-based plants. This thesis is focused in the assessment of the Calcium-Looping allowing a better understanding of the process integration for both applications. Post-combustion CO2 capture based on Calcium-Looping process consist of reacting the CO2 present in the flue gas exiting the fuel power plant with CaO particles according the carbonation reaction, which produces solid CaCO3 as product. CO2 capture efficiencies over 90% have been proved at MWth pilot-scale. After carbonation, solids are sent to a separated reactor where CaO is regenerated according the endothermic calcination reaction. The heat to carry out the reaction is provided by fuel oxy-fuel combustion to ensure a pure CO2 stream exiting the reactor, which after a purification process is ready to be stored or used in another process. The regenerated CaO is sent again to the carbonator reactor for a new CO2 capture cycle. On the other hand, by integrating the Calcium-Looping as thermochemical energy storage system in solar thermal power plants, the process starts performing the calcination reaction from concentrated solar power. CO2 and CaO streams produced are stored separately for later use. When energy is demanded, both components are brought together to the carbonator where the stored energy is released by the carbonation reaction. The carbonation is highly exothermic and therefore a proper integration of the heat released (i.e. for power production) is fundamental for the process efficiency. In spite that both applications are based on the same process, the specific operation conditions required leads to a different behaviour which suggest that the process must be analysed in detail according to each application. This thesis is focused on the development of models and process integration schemes based on lab-scale results under specific conditions selected from the analysis of the potential industrial scale implementation. It involves a multidisciplinary approach combining chemical reactions and process engineering to advance in the response of the challenges posed. This document is structured as follow: the first section introduces the reader to the Calcium- Looping applications, stressing the research opportunities that have motivated the present thesis. This leads to the formulation of the objectives of the work, which are addressed in the presentation and the discussion of the main results of the work. After the conclusions, new research lines to be faced in the near future are summarized.El proceso de Calcium-Looping se basa en la reacción multicíclica de calcinación-carbonatación del carbonato de calcio, el cual es uno de los materiales más abundantes de la tierra. El proceso muestra resultados prometedores para su aplicación como sistema de captura de CO2 poscombustión, así como usado en sistemas de almacenamiento termoquímico de energía en plantas renovables. La presente tesis está enfocada en el análisis del proceso de Calcium-Looping avanzando en la integración del proceso para ambas aplicaciones. La captura de CO2 poscombustión basada en Calcium-Looping consiste en hacer reaccionar el CO2 presente en los gases de combustión de una planta de potencia con partículas de CaO de acuerdo a la reacción de carbonatación, la cual produce CaCO3 como producto. Eficiencias de captura superiores al 90% han sido demostradas a escala piloto. Después de la carbonatación, los sólidos son enviados a otro reactor donde el CaO es regenerado mediante la reacción de endotérmica de calcinación. El calor necesario para llevar a cabo la reacción es obtenido mediante oxicombustión para asegurar una corriente de CO2 pura al a salida del reactor, la cual después de un proceso de purificación está lista para ser almacenada o usada en oro proceso. El CaO regenerado se envía de nuevo al reactor de carbonatación para un nuevo ciclo de captura. Por otro lado, integrando el proceso de Calcium-Looping como sistema de almacenamiento termoquímico de energía en planas termosolares, el proceso comienza llevando a cabo la reacción de calcinación a partir de energía solar concentrada. Como consecuencia de la reacción, CO2 and CaO son producidos y almacenados por separados para su posterior uso. Cuando es necesaria la producción de energía, ambos productos de la calcinación son llevados a un nuevo reactor donde la energía solar almacenada es liberada mediante la reacción de carbonatación. Esta reacción es altamente exotérmica por lo que una adecuada integración del calor liberado es fundamental para la eficiencia del proceso. A pesar de que ambas aplicaciones están basadas en el mismo proceso, las condiciones específicas requeridas llevan a un comportamiento diferente, lo que sugiere que el proceso debe ser analizado en detalle de acuerdo a cada aplicación. Esta tesis se centra en el desarrollo de modelos y esquemas de integración de procesos basados en resultados a escala laboratorio obtenidos a partir de condiciones que simularían la implementación del proceso a escala industrial. Esto conlleva un enfoque multidisciplinar que combina reacciones químicas e ingeniería de procesos para avanzar en la respuesta a los retos planteados.Premio Extraordinario de Doctorado U

The Ammonia Looping System for Mid-Temperature Thermochemical Energy Storage

Thermochemical reactions have a great potential for energy storage and transport. Their application to solar energy is of utmost interest because the possibility of reaching high energy densities and seasonal storage capacity. In this work, thermochemical energy storage of Concentrated Solar Power (CSP) based on an ammonia looping (AL) system is analysed. The AL process for energy storage is based on the reversible reaction of ammonia to produce hydrogen and nitrogen. Concentrating solar energy is used to carry out the decomposition endothermic reaction at temperatures around 650 ºC, which fits in the range of currently commercial CSP plants with tower technology. The stored energy is released through the reverse exothermic reaction. Our work is focused on energy integration in the system modelled by pinch analysis to optimize the process performance and competitiveness. As result a novel configuration is derived which is able to recover high-temperature heat for electricity production with a thermal-to-electric efficiency up to 27 %. The current study shows a clear interest of the system from an energy integration perspective. Further research should be conducted to access the potential for commercial applications

El cambio climático y las nuevas tecnologías : posibilidad de aseguramiento de estos riesgos.

El cambio climático consiste en la variación del clima mundial debido a la acumulación de gases residuales en la atmósfera. Los efectos del impacto se evidencian en el aumento de los terrenos áridos y el incremento de las lluvias que han aumentado el nivel de los ríos y mares. La comunidad internacional viene estructurando regímenes de responsabilidad civil para proteger los efectos del daño ambiental, sin embargo la dificultad en la medición del riesgo hace que la mayoría de éstos efectos resulten inasegurables pues la problemática de la contaminación ambiental que indiscutiblemente tiene incidencia en los cambios climáticos, no se resuelve con una póliza de seguro y el sector asegurador está frente a un reto en el que debe incursionar. Nota: Para consultar la carta de autorización de publicación de este documento por favor copie y pegue el siguiente enlace en su navegador de Internet: http://hdl.handle.net/10818/887

The Calcium-Looping (CaCO3/CaO) Process for Thermochemical Energy Storage in Concentrating Solar Power Plants

Articulo aceptado por la revista. * No publicado aún [28-06-2019]Energy storage based on thermochemical systems is gaining momentum as potential alternative to molten salts in Concentrating Solar Power (CSP) plants. This work is a detailed review about the promising integration of a CaCO3/CaO based system, the so-called Calcium-Looping (CaL) process, in CSP plants with tower technology. The CaL process relies on low cost, widely available and non-toxic natural materials (such as limestone or dolomite), which are necessary conditions for the commercial expansion of any energy storage technology at large scale. A comprehensive analysis of the advantages and challenges to be faced for the process to reach a commercial scale is carried out. The review includes a deep overview of reaction mechanisms and process integration schemes proposed in the recent literature. Enhancing the multicycle CaO conversion is a major challenge of the CaL process. Many lab-scale analyses carried out show that residual effective CaO conversion is highly dependent on the process conditions and CaO precursors used, reaching values as different as 0.07-0.82. The selection of the optimal operating conditions must be based on materials, process integration, technology and economics aspects. Global plant efficiencies over 45% (without considering solar-side losses) show the interest of the technology. Furthermore, the technological maturity and potential of the process is assessed. The direction towards which future works should be headed is discussed.Ministerio de Economia y Competitividad CTQ2014-52763-C2, CTQ2017- 83602-C2 (-1-R and -2-R)Unión Europea Horizon 2020 Grant agreement No 727348, project SOCRATCES

The mOxy-CaL Process: Integration of Membrane Separation, Partial Oxy-combustion and Calcium Looping for CO2 Capture

CO2 capture and storage (CCS) is considered as a key strategy in the short to medium term to mitigate global warming. The Calcium-Looping process, based on the reversible carbonation/calcination of CaO particles, is a promising technology for post-combustion CO2 capture because of the low cost and non-toxicity of natural CaO precursors and the minor energy penalty on the power plant in comparison with amines capture based technologies (4-9 % compared to 8-12 %). Another interesting process to reduce CO2 emissions in power plants is oxy-combustion, which is based on replacing the air used for combustion by a highly concentrated (~95 % v/v) O2 stream. This work proposes a novel process (mOxy-CaL) for post-combustion CO2 capture based on the integration of membrane separation, partial oxy-combustion and the Calcium-Looping process. An oxygenenriched air stream, which is obtained from air separation by using highly permeable polymeric membranes, is used to carry out partial oxy-combustion. The flue gas exiting partial oxy-combustion shows a CO2 concentration of ~30 % v/v (higher than 15 % v/v typical in coal power plants). After that, the flue gas is passed to the CaL process where the CO2 reacts with CaO solids according to the carbonation reaction. Thermogravimetric analysis show that the multicycle CaO conversion is enhanced as the CO2 concentration in the flue gas stream is increased. Process simulations show that the mOxy-CaL process has a high CO2 capture efficiency (~95%) with lower energy consumption per kg of CO2 avoided than previously proposed post-combustion CO2 capture technologies. Moreover, the overall system size is significantly lower that state-of-the-art CaL systems, which allows for an important reduction in the capital cost of the technology

Identification of best available thermal energy storage compounds for low-to-moderate temperature storage applications in buildings

Award-winning paper at III International Congress and V National on Sustainable Construction and Eco-Efficient Solutions (CICSE) March 2017Over the last 40 years different thermal energy storage materials have been investigated with the aim of enhancing energy efficiency in buildings, improving systems performance, and increasing the share of renewable energies. However, the main requirements for their efficient implementation are not fully met by most of them. This paper develops a comparative review of thermophysical properties of materials reported in the literature. The results show that the highest volumetric storage capacities for the best available sensible, latent and thermochemical storage materials are 250 MJ/m3, 514 MJ/m3 and 2000 MJ/m3, respectively, corresponding to water, barium hydroxide octahydrate, and magnesium chloride hexahydrate. A group of salt hydrates and inorganic eutectics have been identified as the most promising for the development of competitive thermal storage materials for cooling, heating and comfort applications in the short-term. In the long-term, thermochemical storage materials seem promising. However, additional research efforts are required.Identificación de los mejores compuestos disponibles de almacenamiento de energía térmica para aplicaciones de baja a moderada temperatura en edificación. En los últimos 40 años se han investigado diferentes materiales de almacenamiento térmico con el objetivo de mejorar la eficiencia energética en los edificios, mejorar el rendimiento de sistemas y aumentar el uso de renovables. Sin embargo, la mayoría no cumple los principales requisitos para su eficiente implementación. Este artículo desarrolla una revisión de las propiedades termofísicas de los materiales existentes en la literatura. Los resultados muestran que las mayores capacidades de almacenamiento volumétrico para los mejores materiales de almacenamiento sensible, latente y termoquímico son 250 MJ/m3, 514 MJ/m3 y 2000 MJ/m3, respectivamente, correspondientes a agua, hidróxido de bario octahidratado y cloruro de magnesio hexahidratado. Un conjunto de sales hidratadas y eutécticos han sido identificados como los más prometedores para el desarrollo de materiales competitivos para aplicaciones de enfriamiento, calefacción y confort a corto plazo. A largo plazo, el almacenamiento termoquímico parece prometedor. Sin embargo, investigación adicional es requerida.Fondo Europeo de Desarrollo Regional SOE1/P3/P0429EUMinisterio de Educación, Cultura y Deportes FPU14/06583Ministerio de Economía y Competitividad BES-2015-0703149Ministerio de Economía y Competitividad CTQ2014-52763-C2-2-RMinisterio de Economía y Competitividad CTQ2017- 83602-C2-2

Influence of Reynolds number on theoretical models for trailing vortices

We conduct direct numerical simulations for a NACA0012 airfoil at Reynolds numbers (Re) ranging from 300 to 7000 to determine the wake behavior behind this wing profile. We characterize the structure of the wing-tip vortex, finding a reasonable agreement with experimental results at Re=7000. In addition, we model the trailing vortex theoretically, thus obtaining the parameters for Batchelor’s and Moore and Saffman’s models. We compare the results of the best fitting for the axial vorticity and the azimuthal velocity, finding only small discrepancies. The main contribution of this research work is to study the evolution of these theoretical parameters as function of the Reynolds number. We observe that the wake becomes unstable at Re ≈1200, in agreement with previous results. These instabilities in the wake behind the wing produce a change in the trend of theoretical parameters (keywords: vortex dynamics, trailing vortices, theoretical models).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Carbonation of Limestone Derived CaO for Thermochemical Energy Storage: From Kinetics to Process Integration in Concentrating Solar Plants

Thermochemical energy storage (TCES) is considered as a promising technology to accomplish high energy storage efficiency in concentrating solar power (CSP) plants. Among the various possibilities, the calcium-looping (CaL) process, based on the reversible calcination-carbonation of CaCO stands as a main candidate due to the high energy density achievable and the extremely low price, nontoxicity, and wide availability of natural CaO precursors such as limestone. The CaL process is already widely studied for CO capture in fossil fuel power plants or to enhance H production from methane reforming. Either one of these applications requires particular reaction conditions to which the sorbent performance (reaction kinetics and multicycle conversion) is extremely sensitive. Therefore, specific models based on the conditions of any particular application are needed. To get a grip on the optimum conditions for the carbonation of limestone derived CaO in the CaL-CSP integration, in the present work is pursued a multidisciplinary approach that combines theoretical modeling on reaction kinetics, lab-scale experimental tests at relevant CaL conditions for TCES, process modeling, and simulations. A new analytic equation to estimate the carbonation reaction rate as a function of CO partial pressure and temperature is proposed and validated with experimental data. Using the kinetics analysis, a carbonator model is proposed to assess the average carbonation degree of the solids. After that, the carbonator model is incorporated into an overall process integration scheme to address the optimum operation conditions from thermodynamic and kinetics considerations. Results from process simulations show that the highest efficiencies for the CaL-CSP integration are achieved at carbonator absolute pressures of ∼3.5-4 bar, which leads to an overall plant efficiency (net electric power to net solar thermal power) around 41% when carbonation is carried out at 950 °C under pure CO.Ministerio de Economía y Competitividad CTQ2014-52763-C2, CTQ2017- 83602-C2European Union 72734

Optimizing the CSP-Calcium Looping integration for Thermochemical Energy Storage

Thermochemical energy storage (TCES) is considered a promising technology to overcome the issues of intermittent energy generation in Concentrated Solar Power (CSP) plants and couple them with yearly electricity demand. The development of this technology could favor the commercial deployment of CSP, which is considered as a key factor for new challenges in reducing GHG emissions. Among other possibilities, using the Calcium Looping (CaL) process for TCES is an interesting choice mainly due to the low cost of natural CaO precursors such as limestone (below $10/ton) and the high energy density that can be achieved (around 3.2 GJ/m3). This manuscript explores several configurations in order to maximize the performance of the CSP-CaL integration with the focus on power cycle integration in the carbonator zone. For this purpose, firstly, a discussion about the possibility of using open and closed power cycles is carried out, which leads to the conclusion that a CO2closed cycle is more appropriate. Then, a closed regenerative CO2Brayton cycle is analyzed in further detail and optimized by means of the pinch-analysis methodology. A main output is that high plant efficiencies (of about 45%) can be achieved using a simple closed CO2Brayton power cycle. The optimized integration layout shows good performances at carbonator to turbine outlet pressure ratios around 3, thus allowing for a feasible integration of the power cycle in the CSP-CaL system.Ministerio de Economía y Competitividad CTQ2014-52763-C2-2-