• Energy Research

Abstract The fluid flow, heat transfer, and gas-phase chemical reactions for a natural-draft plancha-type biomass cookstove are studied at steady state with a commercial CFD code, ANSYS Fluent™. Different firepowers (in the range of real operating conditions), modeled as different flow rates of wood volatiles entering the 3D computational domain, were investigated. Firepower was found to have minimal effect on the air flow rate through the cookstove and the efficiency, but to strongly affect stove temperatures and heating rates. The main results were duplicated by a simple analytical model with one tunable parameter, and with simplified combustion, heat transfer, fluid properties, and pressure losses. The analytical model highlights the importance of the air mass flow rate through the cookstove, which is affected by design choices. The largest diferences between the CFD model and the analytical model occurred at the lower firepowers, when temperatures were so low that combustion was incomplete.

This study applies environmental life cycle assessment to quantify and compare the environmental profile of the production and use of wood pellets for residential heating (baseline) and compares the pellet system with two different alternative systems for residential heating in Mexico: (1) the use of LPG heater and (2) one electricity heater powered by three different sources of electricity. The baseline system boundaries include the stages of forest management, transportation, industrial, distribution, wood pellet energy conversion, and ash management. First-hand data and measurements of the emission profiles in the field and laboratory were developed. The functional unit was 1 MJ of thermal energy for residential heating. Environmental impacts were calculated for six impact categories from the ReCiPe midpoint method. Furthermore, a sensitivity analysis was performed to evaluate the influence of the allocation criteria (mass and economic) as well as adopting different values for the electricity sources (system’s hotspots). The results obtained for each impact category show a relatively wide range of variation when the five scenarios of the heating systems are compared and analyzed. Electricity heater powered with photovoltaic electricity is better for all the impact categories analyzed. The performance of pellets and LPG is very close, but the pellets have lower impacts on global warming (three times), fossil resource scarcity (four times), and acidification. Therefore, the use of pellets in an efficient boiler is a promising option for residential heating.

AbstractImproved cookstoves are used to reduce carbon emissions into the atmosphere and the impact of deforestation, thus improving the quality of life of their users. The main objective of this work is to evaluate three combustion chamber geometries for biomass plancha-type cookstoves, in the range of 9.5–12.5 kW, which corresponds to real operating conditions. The first geometry corresponds to a traditional rocket elbow section that is widely used in this kind of device. The other two geometries are new modified designs. They make use of three and four chamfers above the rocket elbow. Additionally, for all the geometries, the effect of a baffle close to the exit of the chimney is evaluated. Numerical simulations for fluid flow, heat transfer, and gas-phase chemical reactions for the three-dimensional internal volume of the geometries are conducted using ANSYS Fluent 2019 R3. Results for the average temperature on the comal and total mass flow rate at the exit of the chimney are validated with experimental measurements and a theoretical model, respectively. The main findings are that the use of a baffle in all geometries increases the flow recirculation below the comal; as a result, the average temperature of the comal and hence the thermal efficiency reach higher values. Based upon numerical predictions, the cookstove with three chamfers and a baffle provided a more temperature homogeneous distribution on the comal.

This paper introduces a new methodology for the development of appropriate technology that allows satisfying energy needs in rural communities. The methodology integrates the technological development, taking particularly into account the assessment of environmental impacts as well as evaluation of the functionality of the technology. Therefore, it is implemented as a case study in the development of a solar wood-dryer in an artisan community in Mexico. Relevant issues were identified for the success of the methodology, which includes identifying key participants in the community, as well as the use of specialized simulation- and computer-based design tools, and a prior evaluation of the potential environmental impacts through Life-Cycle Assessment (LCA) of the solar wood-dryer. Three geometries of a solar wood-dryer prototype were proposed and analyzed with computer-based simulations, which showed better interior heat transfer than the traditional wood brick-dryer. LCA revealed that the new solar wood-dryer prototype has environmental impacts in all analyzed categories that are 5% or smaller than those of the traditional dryer. Therefore, it was demonstrated that the solar wood-dryer developed with our introduced methodology leads to less environmental impacts compared to those of the traditional wood brick-dryer previously used by the rural community.

ABSTRACTThis investigation aims to develop a device that meets the specific requirements of energy‐intensive household cooking tasks, such as the nixtamalization process. In particular, a pot‐type biomass stove is designed and built. A computer‐aided design (CAD) model of the stove was created, followed by a metal prototype. Thermal performance was evaluated by means of numerical simulations as well as experimental thermographic images. The numerical and experimental results were compared, and the quantitative correlation was found to be in good agreement. The results show that this stove can handle energy‐intensive cooking tasks like nixtamalization of maize. The development of this stove resulted in significant improvements in thermal efficiency and fuel consumption when compared to conventional stoves.

This paper describes and applies a Newton method based on a Numerical Differentiation process to initialize electromagnetic transient simulations in power systems. In order to increase the simulation speed, LAPACK libraries are used to efficiently handle matrix operations. Simulations of the application of the method to the IEEE 5, 14, 30, 57 and 118-bus test systems are presented. Comparisons with a classical Brute Force approach are conducted to establish the efficiency of the proposed numerical algorithm. This method can be used as an alternative to the application of power-flow program to solve the initial value problem in electromagnetic transient studies.

Abstract In this work, the fluid flow, heat transfer, and combustion processes for a plancha-type biomass cookstove are numerically studied. This approach takes into account the numerical solution of mass, momentum, thermal energy, and chemical species conservation equations by using ANSYS Fluent™. Besides the fluid domain, a solid one representing the metallic comal is also considered for the simulations. In particular, numerical results for the CO2 mass flow rate emissions, unburned volatile combustion efficiency (UVE), and thermal efficiency are compared with experimental Water Boiling Tests (WBT) data. For different firepower values, a good comparison is observed. Differences between numerical and experimental results are in the ranges of 2–9% and 1–2% for the CO2 mass flow rates and combustion efficiencies, respectively. Results indicate that the thermal efficiency is higher for the low firepower cases, which is in agreement with experiments.