Renewable energy, biomass & sustainability

Mobile mini-DOAS measurements of the outflow of nitrogen dioxide from the Toluca Valley Metropolitan Area, Mexico

Claudia Inés Rivera-Cárdenas — 2024-01-22

NO₂outflow fluxes were calculated from the City of Toluca, Mexico during January-February 2017 using a mobile zenith viewing mini-DOAS instrument. Measurements were performed in a cross-section of the outflow plume from the Toluca Valley Metropolitan Area with an instrument operating in the visible wavelength region (356 to 510 nm). NO₂retrievals were conducted in the 405 to 465 nm wavelength range. From these measurements, differential vertical columns of NO₂along the measurement route were derived. Using mass-averaged wind speed and wind direction from the Weather Research & Forecasting model, with a 1 km resolution, outflow fluxes of NO₂were calculated from each of the transect measurements. The average NO₂outflow flux for the entire campaign was 1.81 kg/s (156.24 ton/day). To our knowledge, this is the first time that mobile mini-DOAS measurements have been conducted around the City of Toluca and therefore the first time that NO₂outflow fluxes have been reported for this metropolitan area. Comparing our results with emissions inventories we found large variabilities of NO_xemissions reported in emissions inventories and between emissions inventories and our measurements. From these discrepancies we infer that emissions inventories underestimate NO_xemissions from the TVMA. This study contributes to our understanding of outflow fluxes from metropolitan areas and their possible exchange, being the Toluca Valley Metropolitan Area a few kilometers away from the Mexico City Metropolitan Area, one of the largest megacities of the world.

Evaluation of the viability of the use of Lactobacillus casei in the removal of organic contaminants in waste from the craft brewing industry

Itzel Díaz-González — 2024-01-25

Brewers’ spent grains (BSGs) are the most abundant waste generated from the craft brewing process, accounting for approximately 85% of the total byproduct obtained. The need to develop beneficial alternatives for the contribution of the industrial sector and sustainable development has increased interest in the fermentation processes used to produce biomass, using probiotic microorganisms that provide health benefits for those who consume it, obtaining byproducts rich in nutrients. Therefore, this research aimed to evaluate the growth of Lactobacillus casei in Mar, Rogosa and Sharpe broth (MRS) and to evaluate the feasibility of growing L. casei in craft beer residues. To achieve this goal, a 10% v/v inoculum of probiotic bacteria was used in both media. The process consisted of monitoring the biotransformation process at 37°C and 120 rpm for 72 hours and evaluating carbohydrate consumption and cell growth. At the end of 52 h, the carbohydrate concentration in combination with BSG was completely consumed, considering that the initial value was 16.49 g/L. In the case of the MRS medium, a value of 3.42 g/L was obtained at 72 h. Regarding the pH range with the MRS broth and with BSG, the values were 6.89-5.43 and 5-4.41, respectively. Due to the acidity of the synthetic medium, the pH of the synthetic medium was greater than that of BSG. However, L. casei managed to develop in a similar way since quite similar cell growth values were obtained in both media, so it is feasible to use BSG as a culture medium for the development of probiotic species.

Operation of hydropower plants without storage by optimizing the turbine flow. Variations to the optimization model

Juan Manuel Blanco — 2024-02-03

Flowing water power plants take advantage of the flows that circulate through the river in which they are implanted. They do not have in their design storage systems that allow the accumulation of river flows for later use. They only have the infrastructures necessary for the conduction of flows and their use. These types of plants are designed and automated to operate between certain flow limits, working with "constant head", using the available flows at any given time. The operating limits are set by the "equipment flow", for which the plant is designed, and the "technical minimum flow", which corresponds to the minimum flow value with which the plant can work, and which depends on each turbine type. This article is a continuation of the research carried out and part of the results of which have been presented in previous congresses. They established the optimization algorithms to take advantage of times of low flow level (dry season) to use the plant's channels as a storage element for flow rates below the technical minimum and to subject the plant to sequential emptying/filling cycles of the same channels, thus allowing energy recovery, which we will call operation by "optimal flow". This article intends to analyze the response of the proposed optimization model to variations in both the design and operation of the power plants in which its implementation is possible. The response of the plant to variations in the usable volume in the channels, the minimum time established for the operation of the plant, as well as the hydrological characteristics of the year of application is presented.

Emissions to the atmosphere by power plants in Baja California Sur, Mexico

Claudia Inés Rivera-Cárdenas — 2024-02-23

Sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) emissions to the atmosphere released by three power plants located in Baja California Sur, Mexico, were quantified using mini-DOAS instruments. In La Paz municipality, the Punta Prieta Power Plant released 65.67±77.80 tons/day of SO₂ and 6.66±12.57 tons/day of NO₂, while the Internal Combustion Power Plant Baja California Sur released 44.72±5.37 tons/day of SO₂ and 8.27±1.72 tons/day of NO₂. In the municipality of Comondú, the Internal Combustion Power Plant Agustín Olachea released 18.17±8.00 tons/day of SO₂ and 0.67±0.32 tons/day of NO₂. Comparisons of our measurements with emissions inventories and annual operating reports for the Punta Prieta Power Plant are in good agreement, however, we found differences for the Internal Combustion Power Plant Baja California Sur and the Internal Combustion Power Plant Agustín Olachea. Our analyses show that the Punta Prieta Power Plant has increased its SO₂ and NO₂ emissions between 2013 and 2022. The Internal Combustion Power Plant Baja California Sur has increased its SO₂ emissions, while NO₂ emissions have declined between 2013 and 2022. The Internal Combustion Power Plant Agustín Olachea has been decreasing its SO₂ and NO₂ emissions between 2010 and 2022, albeit in 2018, there was a considerable increase of NO₂ emissions.

Kinetic parameters of Lactobacillus acidophilus growth in the lactic fermentation of non-centrifugal cane sugar agroindustry wastes

Itzel Gonzalez-del Rosario — 2024-02-27

The use of sugarcane for the production of non-centrifugal cane sugar is one of the main economic activities in some areas of the central region of the state of Veracruz, México, however, this sector faces different social, techno-economic and environmental challenges. One of the most important problems affecting this agribusiness is the lack of adequate management of the waste generated in the process, mainly sugarcane scum (SCS) and mold wash water (MWW). Lactic fermentation is proposed as an alternative for the utilization of these wastes, since this process reduces the concentration of carbohydrates, producing lactic acid (LA) and increasing the nutrient content. An important aspect of the fermentation process is the knowledge of the kinetic parameters, since with these it is possible to carry out the scaling up. In the present work, the lactic fermentation of SCS and MWW was studied using the bacterium Lactobacillus acidophilus and the kinetic parameters were obtained with the Gompertz model and the Logistic model. The physicochemical characterization of the residues was carried out and the parameters of substrate consumption, lactic acid production and cell density were evaluated during fermentation of a 150 g SCS/L solution in a 0.5 L reactor. After 72 h of fermentation, a maximum growth of 7.63 log CFU/mL, a 50.32% carbohydrate consumption, and a maximum production of 7.56 g LA/L were obtained. For the Gompertz model, the parameters obtained were μ_max=1.2420 h^-1, λ=20.46 h y A=7.585 log CFU/mL, whereas for the Logistic model they were μ_max=0.3214 h^-1, λ=25.39 h y A=7.584 log CFU/mL. It was observed that both residues promote the development of the microorganism L. acidophilus, however, the kinetic parameters of μ_max y λ indicates that it needs more time to adapt to the residues, so it will be necessary to implement strategies to optimize these values.

An open-loop control algorithm for improved tracking in a heliostat

Job Ordaz Castillo — 2024-04-11

The growing energy demand and its relation to climate change have driven the search for sustainable alternatives, such as concentrated solar energy. In this context, heliostats play a crucial role by reflecting and concentrating solar light onto a receiver. However, traditional control approaches based on geographical data have limitations. This study introduces an autonomous control system for heliostats that eliminates the need for preloaded geographical data. The approach is based on communication between the heliostat and the solar tracker, with two configuration modes: map calibration and automatic. Centralized and autonomous heliostats are distinguished, with the latter being the focus of the study. Autonomous heliostats have their own control system and can make decisions regarding positioning and safety. The methodology involves a mathematical algorithm that calculates the optimal rotation and tilt of the heliostat to redirect light toward a target. Simulation and physical prototype testing validate a remarkable consistency between simulated and experimental data. A key result is the surprising similarity of 97.9% between the obtained data, validating the algorithm's effectiveness. This study provides a robust approach for designing autonomous heliostat control systems, integrating simulation and experimentation. These results support the algorithm's precision and ability to direct solar radiation effectively. Expanding towards autonomous control and complete heliostat system evaluation facilitates the path toward more efficient and sustainable concentrated solar energy.