Miguel Ángel Porta-Gándara

Automated Irrigation System Using a Wireless Sensor Network and GPRS Module

An automated irrigation system was developed to optimize water use for agricultural crops. The system has a distributed wireless network of soil-moisture and temperature sensors placed in the root zone of the plants. In addition, a gateway unit handles sensor information, triggers actuators, and transmits data to a web application. An algorithm was developed with threshold values of temperature and soil moisture that was programmed into a microcontroller-based gateway to control water quantity. The system was powered by photovoltaic panels and had a duplex communication link based on a cellular-Internet interface that allowed for data inspection and irrigation scheduling to be programmed through a web page. The automated system was tested in a sage crop field for 136 days and water savings of up to 90% compared with traditional irrigation practices of the agricultural zone were achieved. Three replicas of the automated system have been used successfully in other places for 18 months. Because of its energy autonomy and low cost, the system has the potential to be useful in water limited geographically isolated areas.

Thermal performance of the condensing covers in a triangular solar still

An experimental investigation has been carried out into an attic-shaped solar still subject to natural conditions of Grashof numbers up to 1.7×108. The performance of the condensing covers was studied under two still orientations, east–west and north–south. A continuous recording of the main parameters affecting productivity was made, and significant thermal and distillate differences between the two condensing plates were found. A procedure to estimate each cover production in triangular solar stills as a function of still temperature and area fraction is proposed as an extension to the model proposed by Dunkle. Predictions made with this procedure show closeness to experimental data for the cases studied.

Local wind patterns for modeling renewable energy systems by means of cluster analysis techniques

A method based on cluster analysis techniques is proposed in order to obtain representative local wind patterns. Modeling renewable energy systems, in an accurate way which strongly depends on wind loads, requires reliable data to analyze their response and evaluate their performance. Otherwise poor agreement with the models may be obtained. In a case study for La Paz, Baja California Sur, Mexico, four different wind patterns were obtained from a one-year data set recorded at 10-min intervals.

Effect of passive techniques on interior temperature in small houses in the dry, hot climate of northwestern Mexico

A simple lumped parameter model is used to represent the time variations of internal temperature of a simple house, under hot, extreme weather variation, characteristic of northwestern Mexico. Results are validated by experimental work in a physical model without ventilation, with materials and building techniques typical of low-income family housing in this region. Energy balance in the present work is achieved by means of a system of three simultaneous differential equations, each depicting energy equilibrium in one of the basic building elements: the window glazing, the building materials, and inside air. With the mathematical model properly calibrated, heat transfer coefficients between walls, ceiling and windows are calculated. Passive techniques, such as window shading, orientation and thermal inertia, are evaluated by a normalized temperature index. Results show that interior temperature in the house can be reduced resulting in comfort increase. Then economical pertinence of studied passive elements can be evaluated.

Experimental measurement of the water-to-cover heat transfer coefficient inside shallow solar stills

Abstract The purpose of this work is to measure the overall heat transfer coefficient from water to cover in shallow solar stills using yield measurements. The geometry under analysis represents a real solar still operating with laboratory-controlled temperatures and induced heat flows in steady-state. Temperature differences between the water and the glass cover varied from 2 to 16 K, and water temperature from 298 to 353 K, corresponding to the range of heat flows from 0 to 650 W m−2, in accordance with the operation of a solar still in ambient conditions.

Smartphone Irrigation Sensor

An automated irrigation sensor was designed and implemented to use in agricultural crops. The sensor uses a smartphone to capture and process digital images of the soil nearby the root zone of the crop, and estimates optically the water contents. The sensor is confined in a chamber under controlled illumination and buried at the root level of the plants. An Android App was developed in the smartphone to operate directly the computing and connectivity components, such as the digital camera and the Wi-Fi network. The mobile App wakes up the smartphone, activating the device with user-defined parameters. Then, the built-in camera takes a picture of the soil through an antireflective glass window and an RGB to gray process is achieved to estimate the ratio between wet and dry area of the image. After the Wi-Fi connection is enabled, the ratio is transmitted via a router node to a gateway for control an irrigation water pump. Finally, the App sets the smartphone into the sleep mode to preserve its energy. The sensor is powered by rechargeable batteries, charged by a photovoltaic panel. The smartphone irrigation sensor was evaluated in a pumpkin crop field along 45 days. The experimental results show that the use of smartphones as an irrigation sensor could become a practical tool for agriculture.

Simplified architectural method for the solar control optimization of awnings and external walls in houses in hot and dry climates

In extremely hot and dry climates, like northwestern Mexico, solar gain reduction in houses using solar passive techniques is important for improving comfort inside the construction and to save costs in electrical cooling during the whole year, because the winter season is also hot in those regions. A new one-dimension method is proposed to analyze the interaction between two common shading devices: awnings and external walls to reduce insulation on the facade and inside the house due to fenestration. The method is demonstrated by optimizing a typical dwelling with an azimuth of 90° (east), which, achieves 45% reduction in direct solar insulation during the summer solstice on the profile of the facade. Results showed that this method is simple and reliable in increasing the shadow on the facade and to block completely the solar beam radiation on the windowpane with optimal relations between these shading devices.

Economic feasibility of passive ambient comfort in Baja California dwellings

The economic evaluation of some passive thermal comfort techniques is performed in order to compare long-term energy savings. A direct comparison is made of vernacular architecture, based on adobe walls, against modern, concrete brick building of low-income family housing in tropical, dry-climate conditions in La Paz, Baja California Sur, Mexico. The expected energy requirements of each type, for the same comfort level, are calculated by means of a calibrated mathematical model, and present value of each option is obtained by conventional means using 10% interest over 15 years. The results indicate that, in cases as those analyzed, the use of vernacular passive techniques is more comfortable and economic than present light buildings by a very wide margin.

Wireless Beach Profiler

Abstract Gutiérrez, J.; Gómez-Muñoz, V.; Villa-Medina, F., and Porta-Gándara, M.Á., 2012. Wireless beach profiler. A wireless beach profiler was designed using a vertically aligned accelerometer to estimate slopes along several points of the beach. The accelerometer output from each point was measured as a tilt angle by a microcontroller and transmitted to a personal digital assistant via a radio frequency wireless link. The digital assistant was used to store the data file for subsequent analysis. The device was mounted on a metal board and pulled along a perpendicular path to the beach, where the sampling points were located. The system included a global positioning system (GPS) receiver to record the actual path traversed. The results of this proposed profiling system were compared with an electronic distance meter and with the Emery method. The wireless beach profiler was also evaluated on a robotic vehicle to automate the process. Results showed that this profiler system is a reliable alternative because of its accuracy, portability, and cost. Resumen Se diseñó un dispositivo inalámbrico para perfilar playas, basado en un acelerómetro alineado verticalmente, que permite estimar las pendientes de diversos puntos a lo largo de una trayectoria en la playa. La salida del acelerómetro es el ángulo de inclinación de cada punto que se mide con un microcontrolador y se transmite a un asistente personal digital, mediante un enlace inalámbrico de radiofrecuencia. En el asistente digital se almacena un archivo de datos para su análisis posterior. El dispositivo se coloca en una placa de metal y es jalado a lo largo de una trayectoria perpendicular a la playa, donde se encuentran los puntos de muestreo. El sistema incluye un GPS para registrar la ruta muestreada. Los resultados de este sistema perfilador de playas se compararon con otro sistema como el medidor de distancia electrónico y con el método de Emery. El perfilador inalámbrico también se evaluó en un vehículo robótico para automatizar el proceso. Los resultados mostraron que este sistema propuesto es una alternativa confiable debido a su precisión, portabilidad y costo.

Autonomous Surface Vehicle for Measuring Water Body Parameters

An autonomous surface vehicle (ASV) has been developed to perform autonomous trajectories in protected water bodies for the measurement of diverse parameters. The navigation track is accomplished based on the information from a GPS and an electronic compass. Several water body parameters are measured by means of an electronic sonde. The assigned track is composed by a set of points, each one with a heading angle and a distance. This information is transmitted from a control panel to the ASV by means of a personal digital assistant (PDA), using a graphic user interface (GUI). The wireless communication is achieved with a bidirectional radio modem link. Data from the sonde are also transmitted and stored in the PDA. Additionally, the ASV can be operated manually, in this case, the PDA is used like a conventional remote control. The ASV operation mode can be switched between manual and autonomous at any time. The robotic vehicle was tested both in an aquaculture pond and in a cove in both operation modes. Results show that the ASV is a trustworthy tool for measurement of protected water bodies.