Transcritical Carbon Dioxide Charge-Discharge Energy Storage with Integration of Solar Energy

New and improved energy storage technologies are required to overcome non-dispatchability, which is the main challenge for the successful integration of large shares of renewable energy within energy supply systems. Energy storage is proposed to tackle daily variations on the demand side, i.e., storing low-price energy during off-peak or valley periods for utilization during peak periods. Regarding electrical energy storage, several technologies are available with different potentials for scalability, density, and cost. A recent approach for grid-scale applications is based on transcritical carbon dioxide charge and discharge cycles in combination with thermal energy storage systems. This alternative to pumped-hydro and compressed air energy storage has been discussed in scientific literature, where different configurations have been proposed and their efficiency and costs calculated. The potential of the concept has been demonstrated to be an economical alternative, including hybrid concepts with solar thermal storage. Even at low temperatures, the addition of solar energy has proved to be cost effective. This paper explores the effect of introducing solar-based high temperature heat on the performance of different configurations of “Transcritical carbon dioxide ‒ thermal energy storage system” cycles. A base-cycle with 8-hour discharge time is compared with different layouts. Discussions include details on the models, parametric analyses -including solar technology alternatives-, and simulation results. Round trip efficiency of the base case, without solar support and at pressure ratio of 9.4, is 52%. When solar input is considered, the efficiency is above 60%, increasing the turbine inlet temperature to 950 K. Estimated levelized cost of electricity values are in the range of pumped hydro and compressed air energy storage, 90-140 USD/MWh in agreement with other works on this thermal storage technology. The global analysis shows clear advantages for advancing in the study and definition of this technology for exploitation of synergies at different power ranges, integrated with mid/high temperature solar power plants and with smaller-scale renewable installations.Unión Europea. Fondo Europeo de Desarrollo Regional SOE1 / P3 / P0429E

Análisis de la dinámica de un grupo motobomba diesel: Implicaciones en las causas de rotura

En este artículo se analizan las causas de las averías sistemáticas que se producen en un grupo motobomba. Éstas consisten en la rotura de los rotores de la bomba (6 etapas) por la sección de admisión así como del cierre. El análisis se ha desarrollado en tres etapas: a) desarrollo de un modelo dinámico de torsión, b) desarrollo de un modelo dinámico para identificación de velocidades críticas, c) validación experimental y medida de magnitudes instantáneas. El análisis ha permitido identificar de forma inequívoca la operación de la motobomba muy próxima a una resonancia a torsión del sistema, lo que ha provocado un deterioro prematuro del chavetero así como la abrasión de los rotores.In this paper the causes of a pump-engine systematic failure are analyzed. These consist of the breakage of the rotors of the pump (6 stages) by the admission section as well as of the closing. The analysis has been developed in three steps: a) development of a torsion dynamic model b) development of a dynamic model in order to identify the critics speeds, c) experimental validation and measure of instantaneous parameters. The analysis has allowed identifying the operation of the pump-motor system closely to a torsion resonance, which has caused a premature deterioration of the keyway, as well as the abrasion of the rotors

Carbon capture and utilization for sodium bicarbonate production assisted by solar thermal power

In this paper, a novel carbon capture and utilization process is proposed. It is based on using a fraction of the captured carbon dioxide to produce sodium bicarbonate, a widely used product in the chemical and food industries. The process couples the Dry Carbonate process for carbon dioxide capture with sodium bicarbonate production. Raw material is trona or sodium sesquicarbonate dehydrate, which is a relatively abundant mineral composed by approximately 46% sodium carbonate and 35% sodium bicarbonate by weight. In the process, trona is firstly converted into sodium carbonate in a fluidized bed reactor operated at 180–200 °C and 1 bar. Heat required in the fluidized bed reactor for decomposing trona can be supplied by renewable sources such as low/medium temperature solar energy or biomass. A fraction of the sodium carbonate generated is recirculated for carbon dioxide capture by means of the dry carbonate process. The rest is converted to sodium bicarbonate in a carbonating tower through the reaction with carbon dioxide and water. After separation of sodium bicarbonate and other salts from water, the sodium bicarbonate produced is suitable for direct sale. The use of renewable sources for supplying the energy required at the sorbent regenerator and for trona decomposition yields a near-zero carbon dioxide emissions global system. As case of study, carbon dioxide capture coupled to sodium bicarbonate production has been analysed for a 15 MWel coal fired power plant. Heat required in the carbon capture process penalizes the global system efficiency by a 10.2%, which is reduced just to the electricity parasitic consumption for solids transport and carbon dioxide compression (∼3%) if renewable energy sources are integrated. From an economic perspective, the penalty in electricity consumption is fully compensated by the new by-product sales. Taking into account the reduction of electricity sales and current prices of trona and sodium bicarbonate a return of investment is obtained in the range between 3 and 8.7 years with an internal rate of return over 12%. These values improve the current forecast of any other carbon capture and storage process up to date, which suggests a high interest of the proposed conceptual integration specially for regions where trona is widely available

Preliminary study on the performance of biomorphic silicon carbide as substrate for diesel particulate filters

This paper presents the results of a preliminary experimental study to assess the performance of biomorphic silicon carbide when used for the abatement of soot particles in the exhaust of Diesel engines. Given its optimal thermal and mechanical properties, silicon carbide is one of the most popular substrates in commercial diesel particulate filters. Biomorphic silicon carbide is known for having, besides, a hierarchical porous microstructure and the possibility of tailoring that microstructure through the selection of a suitable wood precursor. An experimental rig was designed and built to be integrated within an engine test bench that allowed to characterizing small lab-scale biomorphic silicon carbide filter samples. A particle counter was used to measure the particles distribution before and after the samples, while a differential pressure sensor was used to measure their pressure drop during the soot loading process. The experimental campaign yielded promising results: for the flow rate conditions that the measuring devices imposed (1 litre per minute; space velocity = 42,000 L/h), the samples showed initial efficiencies above 80%, pressure drops below 20 mbar, and a low increase in the pressure drop with the soot load which allows to reach almost 100% efficiency with an increase in pressure drop lower than 15%, when the soot load is still less than 0.01 g/L. It shows the potential of this material and the interest for advancing in more complex diesel particle filter designs based on the results of this workMinisterio de Economía y Competitividad (España) MAT2013-41233-R DPI2013-46485-C3-3-RFondos FEDER MAT2013-41233-R DPI2013-46485-C3-3-RUniversidad de Sevilla VI Plan Propio I.3B - C.I. 24/05/2017 MAT2016-76526-

Almacenamiento termoquímico en plantas CSP basado en calcium-looping: retos y oportunidades

Libro de Actas del XVI Congreso Ibérico y XII Congreso Iberoamericano de Energía Solar, 20 – 22 de junio de 2018 Madrid, EspañaLa integración de sistemas termoquímicos de energía en plantas CSP está ganando interés en los últimos años. De entre los posibles sistemas termoquímicos, el proceso de Calcium-looping (CaL), basado en la calcinación/carbonatación multicíclica de CaCO3, está considerado como uno de los más prometedores. Tras la aparente sencillez del proceso se encuentran una serie de retos que deben ser resueltos para que la tecnología pueda alcanzar una escala comercial. En el presente trabajo se muestra un análisis crítico del estado actual de la tecnología con el objetivo de evaluar los retos y oportunidades que presenta la integración del CaL como sistema de almacenamiento termoquímico en plantas CSP. El proyecto SOCRATCES, financiado dentro del programa H2020, tiene como principal objetivo desarrollar un prototipo a escala piloto de la integración CSP-CaL en Sevilla (España).Thermochemical energy storage is gaining attention in last years to be integrated in CSP plants. Among the various possibilities, the Calcium-looping (CaL) process, based on the multicyclic calcination/carbonation of CaCO3, is considered as one of the most promising systems. However, for a commercial deployment of CSP, several challenges must be solved. This work presents a critical analysis on the status of the technology with the aim of evaluating the main challenges and opportunities of the CSP-CaL integration. The SOCRATCES project, founded from the European Union’s Horizon 2020 research and innovation programme, aims to develop a CSP-CaL prototype at pilot scale in Seville (Spain)

Methodology for the estimation of cylinder inner surface temperature in an air-cooled engine

A methodology for the estimation of the mean temperature of the cylinder inner surface in an air-cooled internal combustion engine is proposed. Knowledge of this temperature is necessary to determine the heat flux from the combustion chamber to the cylinder wall. Along with the heat transfer coefficient this parameter also allows almost 50% of engine heat losses to be determined. The temperature is relatively easy to determine for water-cooled engines but this is not in the case for air-cooled engines. The methodology described here combines numerical and experimental procedures. Simulations were based on FEM models and experiments were based on the use of thermocouples and infrared thermography. The methodology avoids the use of data or correlations developed for other engines, providing more reliable results than extrapolating models from one engine to another. It also prevents from taking measurements from inside the combustion chamber, reducing invasion and experiments complexity. The proposed methodology has been successfully applied to an air-cooled four-stroke direct-injection diesel engine and it allows the cylinder mean inner surface temperature and cylinder-cooling air heat transfer coefficient to be estimated.Ministerio de Eduación y Ciencia CTQ2007-68026-CO2-02/PP

Power cycles integration in concentrated solar power plants with energy storage based on calcium looping

Efficient, low-cost and environmentally friendly storage of thermal energy stands as a main challenge for large scale deployment of solar energy. This work explores the integration into concentrated solar power plants of the calcium looping process based upon the reversible carbonation/calcination of calcium oxide for thermochemical energy storage. An efficient concentrated solar power-calcium looping integration would allow storing energy in the long term by calcination of calcium carbonate thus overcoming the hurdle of variable power generation from solar. After calcination, the stored products of the reaction (calcium oxide and carbon dioxide) are brought together in a carbonator reactor whereby the high temperature exothermic reaction releases the stored energy for efficient power production when needed. This work analyses several power cycle configurations with the main goal of optimizing the performance of the overall system integration. Possible integration schemes are proposed in which power production is carried out directly (using a closed carbon dioxide Brayton power cycle) or indirectly (by means of a steam reheat Rankine cycle or a supercritical carbon dioxide Brayton cycle). The results obtained show that the highest plant efficiencies (up to 45–46%) are achievable using a closed carbon dioxide Brayton power cycle.Ministerio de Economia y Competitividad CTQ2014-52763-C2-1-R, CTQ2014- 52763-C2-2-R, MAT2013-41233-

Analysis of a new analytical law of Heat Release Rate (HRR) for Homogeneous Charge Compression Ignition (HCCI) combustion mode versus analytical parameters

Homogeneous charge compression ignition (HCCI) engines produce very low NO and soot emissions and alsoimprove engine efficiency when compare to conventional spark ignition engines. The combustion process bases on the self-ignition of a homogenous air-fuel mixture without an external ignition source. The gas temperature is very important to initiate the combustion and to promote the appropriate chemical kinetics. As a result, the heat release rate and heat transfer inside the combustion chamber play a significant role in the HCCI combustion mode. The high relevance of gas temperature on this combustion mode means that heat transferis considered through a dedicated heat transfer model. In this system the forced convection from hot gases to the combustion chamber walls is the dominant heat transfer mechanism. This paper focuses on the relationship between HRR in HCCI combustion mode and the four parameters that are required for an analytical function to model this heat release rate. More specifically, the influences of the fuel-air equivalence ratio, engine speed and EGR on the four parameters that control HRR are examined. The analytical HRR law is validated over a wide range of operating conditions in HCCI combustion mode and shows that these four parameters are directly related to any load condition, including engine speed, fuel rate and EGR. These parameters can therefore be used to characterize this combustion mode.Ministerio de Ciencia y Eduación CTQ2007-68026-CO2-02/PP

A new heat release rate (HRR) law for homogeneous charge compression ignition (HCCI) combustion mode

Homogeneous charge compression ignition (HCCI) engines are drawing attracting attention as the next-generation’s internal combustion engine, mainly because of its very low NOx and soot emissions and also for improvement in engine efficiency. Much research has been carried out in order to go deeper in this combustion process using multizone models or CFD codes. These simulation tools, although they can give a detailed view of the combustion process, are very time consuming and the results depend a lot on the initial conditions. A previous step to be considered in the simulation of the HCCI process is a heat release law evaluated from results of the experiment and a zero-dimensional model. This paper focuses on the development of a new heat release rate (HRR) law that models the HCCI process when the combustion chamber is considered as a homogeneous volume. The parameters of this law have been adjusted through an optimization process that has allowed to fit the combustion chamber pressure. All the engine operative conditions from low to full load have been successfully simulated with this HRR law, with the maximum error in the estimation of combustion chamber pressure less than 2%.Ministerio de Ciencia y Eduación CTQ2007-68,026-CO2-02/PP

A new model of the carbonator reactor in the Calcium Looping technology for post-combustion CO2 capture

The Ca-Looping (CaL) process is considered as a promising technology for CO2 post-combustion capture in power generation plants yielding a minor penalty on plant performance as compared with other capture technologies such as conventional amine-based capture systems. This manuscript presents a new carbonator reactor model based on lab-scale multicyclic CaO conversion results, which take into account realistic CaO regeneration conditions that necessarily involve calcination under high CO2 partial pressure and high temperature. Under these conditions, CaO conversion in the diffusion controlled stage is a relevant contribution to the carbonation degree in the typical residence times. The main novelty of the model proposed in the present work is the consideration of the capture efficiency in the diffusion controlled phase of carbonation. It is demonstrated that increasing the residence time by a few minutes in the carbonator yields a significant improvement of the capture efficiency. Model predictions are shown to agree with experimental results retrieved from pilot-scale tests. The new model allows a more accurate evaluation and prediction of carbonator’s performance over a wider range of residence times. The results obtained may be relevant for the optimization of CaL operation parameters to be integrated in real power plants