Refrigeration Capacity and Effect of Ageing on the Operation of Cellulose Evaporative Cooling Pads, by Wind Tunnel Analysis

This study investigates the temperature reduction capacity and water consumption of a fan-pad system installed in a greenhouse located in the coastal regions of Almería. The suitability of this system for coastal zones with high environmental humidity during the summer is analyzed. Historical temperature and relative humidity series are studied, obtaining the thermal difference and maximum, medium, and minimum monthly water consumption of the pads based on the operation data of the pads. Despite the high relative humidity of the air in the hottest hours of the day, a decrease of 5.92 ºC in the mean temperature and a water consumption of 13.55 l/h per square meter of an evaporative cooling pad are obtained in the month of August. Additionally, the operation of a cellulose evaporative cooling pad installed for 3 years in a greenhouse is analyzed in a wind tunnel and compared with that of a new pad of the same model. Over time and with low maintenance, the porosity of the pad decreases due to salt incrustation. The salt incrustation makes airflow more difficult in the pad, increasing the pressure drop by 170.04%; however, the air saturation efficiency of the pad increases by 6.6% due to the greater contact time between the air and the waterMinisterio de Economía y Competitividad de España AGL2015-68050-RUnión Europea (FEDER) AGL2015-68050-

Assessment of the cooling potential of an indoor living wall using different substrates in a warm climate

The use of vertical greenery systems in buildings is becoming very popular as they provide several benefits. In this work, the influence of an indoor living wall on the temperature and humidity in a hall inside the School of Agricultural Engineering (University of Seville) was studied. Four different substrates, Geotextile, Epiweb, Xaxim and coconut fibre, were used to grow the plants in order to assess their performance. Several parameters such as temperature, humidity, plant growth or water consumption were monitored and analyzed during a 4-month period. The cooling effect of the living wall was proven, with an average reduction of 4°C over the room temperature though maximum decrements of 6°C have been observed in warmer conditions. Higher air humidity levels were experienced near the living wall, increasing the overall humidity in the room. All the substrates tested were suitable for plant growing and their behaviour was similar. Geotextile showed the best cooling capacity but higher water consumption, coconut fibre presented degradation problems and Epiweb performance was the poorest. Therefore, these systems have been proven to be very useful and interesting for warm indoor environments due to the cooling effect observed in addition to their bio-filtration capacity and the aesthetic component

Energy Efficiency in Greenhouse Evaporative Cooling Techniques: Cooling Boxes versus Cellulose Pads

Evaporative cooling systems using a combination of evaporative pads and extractor fans require greenhouses to be hermetic. The greatest concentration of greenhouses in the world is located in southeast Spain, but these tend not to be hermetic structures and consequently can only rely on fogging systems as evaporative cooling techniques. Evaporative cooling boxes provide an alternative to such systems. Using a low-speed wind tunnel, the present work has compared the performance of this system with four pads of differing geometry and thickness manufactured by two different companies. The results obtained show that the plastic packing in the cooling unit produces a pressure drop of 11.05 Pa at 2 m·s−1, which is between 51.27% and 94.87% lower than that produced by the cellulose pads. This pressure drop was not influenced by increases in the water flow. The evaporative cooling boxes presented greater saturation efficiency at the same flow, namely 82.63%, as opposed to an average figure of 65% for the cellulose pads; and also had a lower specific consumption of water, at around 3.05 L·h−1·m−2·°C−1. Consequently, we conclude that evaporative cooling boxes are a good option for cooling non-hermetic greenhouses such as those most frequently used in the Mediterranean basin

Direct evaporative cooling from wetted surfaces: Challenges for a clean air conditioning solution

Producción CientíficaEvaporative cooling has a major role to play in fighting climate change and in achieving a low-carbon economy. As it helps to reduce energy demand for air conditioning, it is gaining attention in terms of improving energy efficiency in buildings. Evaporative cooling from wetted media can enhance water–air contact, thereby improving heat and mass transfer further and avoiding aerosols. Wetted media are commonly called evaporative cooling pads and are widely used in greenhouses, intensive livestock farming, and industrial facilities. However, a deep understanding of evaporative cooling pad performance can enhance their application to indoor occupied spaces such as residential or commercial cooling, or in hybrid air conditioning systems. Most studies analyze pad performance mainly in terms of pressure drop and saturation effectiveness. However, some studies propose alternative cooling efficiency parameters and others provide insights into key aspects such as power requirements and the coefficient of performance, water consumption, risk of water entrainment, material decay, and air quality, as well as the effect of water temperature and salinity, solar radiation, or wind speed. Existing results on these less studied performance issues are reviewed, and we identify the gaps in the literature in addition to highlighting the main challenges encountered, in an effort to guide future researchers in the field and enhance the application of direct evaporative cooling.Junta de Castilla y León - Fondo Europeo de Desarrollo Regional (grant VA272P18

Energy Efficiency in Greenhouse Evaporative Cooling Techniques: Cooling Boxes versus Cellulose Pads

Evaporative cooling systems using a combination of evaporative pads and extractor fans require greenhouses to be hermetic. The greatest concentration of greenhouses in the world is located in southeast Spain, but these tend not to be hermetic structures and consequently can only rely on fogging systems as evaporative cooling techniques. Evaporative cooling boxes provide an alternative to such systems. Using a low-speed wind tunnel, the present work has compared the performance of this system with four pads of differing geometry and thickness manufactured by two different companies. The results obtained show that the plastic packing in the cooling unit produces a pressure drop of 11.05 Pa at 2 m·s−1 , which is between 51.27% and 94.87% lower than that produced by the cellulose pads. This pressure drop was not influenced by increases in the water flow. The evaporative cooling boxes presented greater saturation efficiency at the same flow, namely 82.63%, as opposed to an average figure of 65% for the cellulose pads; and also had a lower specific consumption of water, at around 3.05 L·h−1 ·m−2 ·°C−1 . Consequently, we conclude that evaporative cooling boxes are a good option for cooling non-hermetic greenhouses such as those most frequently used in the Mediterranean basin.Junta de Andalucía P09-AGR-4593Ministerio de Ciencia e Innovación AGL2010-22284-C03-0

Naturación urbana y jardinería vertical: de las fachadas verdes a los muros vegetales

En las últimas décadas, las urbes están creciendo considerablemente, dedicándose un porcentaje cada vez más elevado a edificaciones. Se prevé que en el periodo entre 2000 y 2030, la población urbana del mundo habrá aumentado un 72%, mientras que la superficie de las zonas edificadas donde viven 100.000 o más personas podría aumentar en un 175%. En este difícil contexto, la aplicación de los principios de sostenibilidad en las áreas urbanas se erige como uno de los mayores retos de las políticas ambientales del siglo XXI. Su éxito dependerá en gran medida del modelo de ciudad a desarrollar, particularmente en lo que se refiere a la relación entre desarrollo urbano y consumo de recursos ambientales

Aprendizaje basado en proyectos y trabajo en equipo: experiencia de innovación docente en hidráulica para graduados en Ingeniería Agrícola

En este trabajo se describe un proyecto de innovación docente para la mejora de los procesos de enseñanza-aprendizaje de Hidráulica en el Grado de Ingeniería Agrícola. El proyecto consistió en plantear, en dos etapas diferenciadas, metodologías de aprendizaje basadas en proyectos y en el trabajo en equipo. En la primera etapa, un estudiante de último curso de titulación diseñó, construyó y validó la funcionalidad de dos bancos didácticos de ensayo de bombas centrífugas. Este trabajo le permitió alcanzar un nivel avanzado de conocimientos teórico-prácticos de Hidráulica así como la realización de su Proyecto Fin de Carrera. En una segunda etapa, los bancos didácticos de ensayo de bombas fueron utilizados en la docencia de la asignatura de Grado en la que se imparte Hidráulica. Los profesores propusieron a los estudiantes diversas actividades prácticas de trabajo en grupo en las que debían utilizar los bancos de ensayo. En estas actividades los estudiantes debían resolver empíricamente (i.e. utilizando los bancos) problemas planteados previamente por los profesores y comparar dichos resultados con los obtenidos de forma analítica de acuerdo a los contenidos teóricos explicados en las clases de aula. Los resultados de un único curso académico indican que la utilización y manipulación por parte de los estudiantes de sistemas de impulsión reales no incrementó el grado de adquisición de competencias específicas relacionadas con los sistemas hidráulicos de impulsión frente al resto de competencias específicas de la asignatura

Multidisciplinary Education for New Landscape Engineering Concepts using Problem-Based Collaborative Learning. A Case Study in Spain

Problem-based learning (PBL) is widely regarded as a successful educational method. In Spain, most engineering degrees are still based mainly on old style lecture classes where a great deal of information is given to the students. This work assesses the introduction of a PBL strategy as a complement to traditional engineering education. The instructors’ and students’ attitudes towards its implementation are studied. A new approach has been proposed for the PBL strategy: instead of a single problem, a chain of problems was developed that could be solved in a collaborative environment. Results from the experience showed a high level of student acceptance. Response to the PBL initiative was found to be positive both for instructors and students, though lack of time, difficulties in evaluations and an increase in students’ and teachers’ workloads were the main disadvantages. Compared with traditional engineering curricula, the mixed traditional–PBL model appears to inspire a higher degree of involvement in study activities where on-line learning tools played an important role

Influence of Water and Air Flow on the Performance of Cellulose Evaporative Cooling Pads Used in Mediterranean Greenhouses

Evaporative cooling systems are a widely used technique in Mediterranean greenhouses. In this study, the cellulose evaporative cooling pads most commonly used in this region were tested in the laboratory using a new methodology in a wind tunnel to determine the water flow on the pad and air flow through it, as well as the water consumption and pressure drop caused by each pad as a function of air speed. Greater water flow increased the pressure drop, but the main effect on performance was caused by modifying the air flow through the pad. We recommend a range of air speeds through the pad of 1 to 1.5 m s‐1, at which the pressure drop was between 3.9 and 11.25 Pa, depending on the type of pad and the water flow applied. On the other hand, saturation efficiency ranged between 64% and 70%, while the amount of evaporated water varied between 1.8 and 2.62 kg h‐1 K‐1 per square meter of pad area

Vertical Greening Systems and Sustainable Cities

Urban development is causing environmental and social concerns that are compromising human welfare and cities sustainability. New urban greening concepts are appearing in order to mitigate these problems in a sustainable and natural way. Vertical greening systems can be defined as structures which allow vegetation to spread over a building facade or interior wall. These systems are becoming popular though they are still evolving and more knowledge on some of their particular impacts is required. In the last five years, the number of studies published in the scientific literature on this topic, especially involving living walls, has significantly increased. This scientific interest has been corresponded with an increased and parallel attention by the general public. This work offers a broad description of the different systems and a comprehensive review of the particular benefits of these green infrastructures. Knowledge gaps and shortcomings have also been identified and discussed