CFD modelling of the ammonia vapour absorption in a tubular bubble absorber with NH3/LiNO3

The absorber is a key component of absorption cooling systems, and its further development is essential to reduce the size and costs and facilitate the diffusion of absorption cooling systems. Computational fluid dynamics (CFD) can facilitate the characterization of the equipment used in absorption cooling systems at lower costs and complexity, but they must be properly developed and validated to provide reliability. This study provides a detailed description and assessment of a 3D CFD bubble absorber model developed to simulate the absorption process in a vertical double pipe with the NH3/LiNO3 solution. It includes a comprehensive methodology to develop the CFD model and its validation considering the effect of the solution flow and the cooling water temperature on absorber performance parameters such as the absorption mass flux and the solution heat transfer coefficient. The results show that the ‘Volume of Fluid model’ and the ‘Realizable k-epsilon model’ provide the lowest residuals and computational times in the simulations while a good correspondence between the CFD model and the experimental data with errors below 10% and 7% for the absorption mass flux and solution heat transfer coefficient, respectively, was obtained. The maximum absorption rate and heat transfer coefficient were 0.00441 kg m−2 s−1 and 786 W m−2 K−1, respectively

The energy potential of agriculture, agroindustrial, livestock, and slaughterhouse biomass wastes through direct combustion and anaerobic digestion. The case of Colombia

In Colombia, agriculture and livestock production, and the processing agroindustry (including slaughterhouses) are a significant source of biomass wastes, which often generate significant environmental impacts. Waste-toenergy technologies, particularly direct combustion and anaerobic digestion systems are an alternative to revalorize these wastes as energy sources while reducing their environmental impacts. To this end, is necessary to identify the biomass-based energy potential from the available biomass wastes. It is additionally necessary to highlight potential applications of the biomass-based energy potential, to replace unsustainable energy sources like fossil fuels or cooking wood in the end-use energy mix. To this end, an inventory of the main crops and livestock produced in Colombia, and the share processed in agroindustry was developed to identify the available biomass wastes for energy applications. Based on the inventory, the biomass-based energy potential was calculated for the use of direct combustion and anaerobic digestion systems. The results show a bioenergy potential of 60,000 to 120,000 GWh per year, with higher potentialities for direct combustion systems than for anaerobic digestion. In particular, the biogas potential account for 90% of the use of natural gas and LPG. Moreover, using around half of the solid biomass available in direct combustion systems can potentially replace the use of solid fuels (i.e. wood and coal). In total, the combined use of direct combustion and anaerobic digestion can support from 50 to 97% of the use of gaseous and solid fuels. Using combined heat and power systems for heat and electricity production can increase the biomass share in the end-use energy mix up to 15 to 28%, including 27 to 53% of the 68,943 GWh of electricity produced in 2018

Modeling wind speed with a long-term horizon and high-time interval with a hybrid fourier-neural network model

The limited availability of local climatological stations and the limitations to predict the wind speed (WS) accurately are significant barriers to the expansion of wind energy (WE) projects worldwide. A methodology to forecast accurately the WS at the local scale can be used to overcome these barriers. This study proposes a methodology to forecast the WS with high-resolution and long-term horizons, which combines a Fourier model and a nonlinear autoregressive network (NAR). Given the nonlinearities of the WS variations, a NAR model is used to forecast the WS based on the variability identified with the Fourier analysis. The NAR modelled successfully 1.7 years of windspeed with 3 hours of the time interval, what may be considered the longest forecasting horizon with high resolution at the moment

Estado del arte del proyecto: “evaluación y comparación del potencial energético de la biomasa en Colombia y otros países”

La biomasa está llamada a ser una fuente esencial de energía en el futuro, como el principal sustituto de los combustibles fósiles. Adicionalmente, el uso de la biomasa permitirá reducir las emisiones netas de gases de efecto invernadero, al ser un combustible más amigable con el medioambiente. Por consiguiente, definir el potencial energético de la biomasa en un país es esencial para promover la implementación de sistemas de energía basados en biomasa. En Colombia el potencial energético de biomasa de no se ha estudiado a profundidad, por lo que se desconoce cómo puede explotarse, que tecnologías son las más adecuadas, y cuál es la viabilidad económica a pequeña, mediana o gran escala para las diferentes fuentes de biomasa disponible en la agricultura, el sector pecuario, los residuos sólidos municipales, etc., de implementar las tecnologías energéticas disponibles. Una vía de identificar estrategias de explotación del potencial energético de la biomasa, es la comparación con el potencial de otros países donde se han implementado sistemas biomasa-a-energía de forma satisfactoria

The temperature gradient of cereals as an optimization parameter of the milling process in hammermills

The wear degree of knives in hammermills strongly influences electricity consumption, productivity, and total operating costs. Currently, the timely replacement of the knives set is decided based on visual inspections, a feedstock load or a lifespan defined, the electric demand of the mill as compared to the limit of the motor driving it, or the vibrations of the hammermill. These approaches present different shortcomings. This study proposes the temperature gradient of the feedstock during the milling process as an indicator to monitor the wear degree of knives. The temperature gradient was implemented in a hammermill milling maize to compare two operating modes. In the conventional operating mode, the knives set mills with one edge during its lifespan, replacing the set once the electricity demand approaches the limit capacity of the electric motor driving the mill, or until the vibrations increase over safety limits. Moreover, in the proposed operating mode the temperature gradient is used to define the timely replacement/rotation of the knives edge. In this case, the four edges of the knives are used. The electricity consumption, productivity, and temperature gradient of the process were measured during the milling of ten maize loads of 2500 tons each. These data were used to characterize the performance of the hammermill, and the influence of the temperature gradient on its operational performance. As a result, a temperature gradient of 6.5 °C was defined as the optimal value to change the rotational direction or replacing the knives set in the hammermill assessed. As compared to the traditional operation approach, the use of the temperature gradient resulted in a reduction of the electricity consumption of 32%, and the greenhouse gas emissions by 37%, while reducing the total costs by 33%, and increasing productivity by 20%. Therefore, this approach stands as a significant opportunity to upgrade the operation of hammermills

Energy balance and exergy of a vertical cell furnace for lime production

This paper aims with methodologies and indicators for evaluating the impacts of freshwater use, the existing methods fundamentally analyze the amount of water used in relation to the impacts caused. Taking into account that there is a recognized need to consider the impacts, specifically on life cycle bases, the problem is that the data is considered insufficient or unreliable in the life cycle databases of water use, in addition not The method for evaluating the impact of the life cycle coincides with regard to the estimated impacts on the use of fresh water. These difficulties are highlighted and the advantages, limitations, differences in the results between different methods are analyzed, and the need for an improved methodology for evaluating the impacts of water use on life cycle bases. Quicklime production is a high energy consumer that is also characterized by high CO2 emissions. This work sets out to develop the energetic and exergetic balance of the limestone calcination process in order to identify the most influential factors in fuel consumption. The results show that the destruction of exergy during due to the combustion of the fuel and the transfer of heat and moment of the process are the most irreversible processes. The results also show that the energy and the exergy contained in the exhaust gases represent the main loss of the process. The combination of these factors represents more than 50% of the energy supplied to the process.El trabajo trata las metodologías y los indicadores para la evaluación de los impactos de uso del agua dulce, los métodos existentes analizan fundamentalmente la cantidad de agua usada con relación a los impactos ocasionados. Teniendo en cuenta que hay una necesidad reconocida para considerar los impactos, específicamente sobre bases del ciclo de vida, la problemática es que se consideran insuficientes los datos o no son confiables en las bases de datos del ciclo de vida del uso del agua, además no coincide el método de valoración del impacto del ciclo de vida para lo relacionado con los impactos estimados en el uso del agua dulce, se resaltan estas dificultades y se analizan las ventajas, limitaciones, diferencias en los resultados entre diversos métodos y se observa la necesidad de una metodología perfeccionada para la evaluación de los impactos del uso del agua sobre bases del ciclo de vida. La producción de cal viva es un alto consumidor de energía que además se caracteriza por elevadas emisiones de CO2. Este trabajo se propone desarrollar el balance energético y exergético del proceso de calcinación de calizas con el objetivo de identificar los factores más influyentes en el consumo de combustible. Los resultados muestran que la destrucción de exergía durante debido a la combustión del combustible y a la transferencia de calor y momento del proceso son los procesos más irreversibles. Los resultados además muestran que la energía y la exergía contenida en los gases de escape representan la principal pérdida del proceso. La combinación de estos factores representa más del 50% de la energía suministrada al proceso

Data supporting the improvement of forecasting and control of electricity consumption in hotels

Improving and managing the electricity efficiency in hotel facilities is essential to reduce the hotel operation costs and its environmental impacts. The data presented shows the evolution of the electricity consumption and management between 2013 and 2015 in two hotel facilities in Cuba (one beach hotel and one city hotel). The data additionally includes the daily measures used to develop control tools for an energy management system. The data presented in the article relates to the research study: Tools to improve forecasting and control of the electricity consumption in hotels Cabello et al., 2016, and it corresponds to the energy audits developed in one beach hotel (Hotel A) and one city hotel (Hotel B) in Cuba

Environmental assessment of pig production in Cienfuegos, Cuba: Alternatives for manure management

As pork is indispensable in the diet of Cuban people, the government was forced to prioritize its production. Pig production causes several environmental impacts related with air, water and soil pollution, which can be quantified with the application of Life Cycle Assessment that allows to optimize products and processes by identifying their environmental impacts. Farming systems considered in different Life Cycle Assessment studies show substantial differences in their characteristics, namely: animal productivity, feed composition, manure management and production period, which influences the environmental performance of each system. Therefore, each study is unique for the system it assesses and should be analyzed individually. In Cuba, the environmental implications of pig production, whose understanding is cornerstone to eventually adopt more environmentally sound practices while ensuring high productivity standards, are yet to be quantified. This study provides some fundamental insights in the life cycle of pig production in the province of Cienfuegos. The assessment if focused in large farms of the province of Cienfuegos which causes large environmental impacts. Large farms accounts for the production of 77% of the pigs delivered to slaughter houses in the province. Pig production in Cienfuegos accounts for 7-12% of Cuban production. The quantification of the environmental impacts of pig production resulted in an impact per finished pig of 120 kg of live weight of 1892 MJ abiotic depletion of fossil fuels, 1019 kg-CO2-eq. global warming potential, 36 kg 1.4-dichlorobenzene-eq. human toxicity, 17 kg 1.4-dichlorobenzene-eq. terrestrial toxicity, 1 kg 1.4-ethylene-eq. photo-oxidant formation, 12 kg-SO2-eq. acidification potential and 6 kg PO4-eq. eutrophication potential. It appeared that the main opportunities to improve the environmental performance of pig production in Cienfuegos are reduction of the impacts of the anaerobic lagoons used for manure management on global warming potential, acidification potential and eutrophication and the impact on acidification potential of pig housing. Direct land spreading of manure appears as the best alternative to lagooning, considering the current situation of pig breeding in Cienfuegos

Data supporting the evaluation of the energy recovery potential of thermoelectric generators in diesel engines

Power generation with thermoelectric devices in internal combustion engines is an alternative to recover some of the energy loss with the exhausts. This data article supports a study that assesses the potentialities of energy recovery with thermoelectric generators in diesel engines and its influence on gaseous emissions. To this end, a set of experiments was developed with a thermoelectric generator and a waffle heat exchanger. The experimental design included nine operation points of the engine to characterize the energy recovery of the thermoelectric generator under different exploitation conditions. Three different fuels (i.e., diesel, B5, and B10) were used. The experiments were developed in a test bench with three data acquisition systems to measure the operational variables (e.g., electric power generation, pressure drop, temperature, etc.). Moreover, a gas analyzer (BrainBee AGS-688), Bacharach gas analyzer (PCA 400), and a smoke meter (BrainBee OPA100) were used to measure exhaust emissions

Assessing the biofuel – transport nexus. The case of the sugar industry in cuba

Cuba currently faces a limited availability of transportation to support the development needs of the country. Transport availability is mostly limited because of fuel shortage. Moreover, Cuba has an important production of sugarcane, with a significant potential to further increase its production. Using sugarcane-based bioethanol is a significant opportunity for sugarcane producer countries. There are different raw materials available in the sugar industry to produce bioethanol. Therefore, there are different scenarios to increase the production of sugarcane and energy cane, to increase bioethanol production. In this study, two scenarios of sugarcane and energy cane production were considered, from which there are eight possible scenarios of bioethanol production. These bioethanol production scenarios were matched with three transport scenarios, including a business-as-usual scenario, a scenario considering the use of bioethanol blends in standard gasoline and diesel engines, and the and introduction of vehicles running on high ethanol blends or pure bioethanol (i.e flexible fuel vehicles, and ethanol buses and trucks). In total, the production of sugarcane-based bioethanol might support from 4 to 58% of the yearly demand for transport energy in the transport scenarios. Additionally, the use of bioethanol as a transport fuel can potentially reduce transport-related greenhouse gas emissions by an estimated 3–30%