Javier Leal Iga

Modeling of the Climate for a Greenhouse in the North-East of México

Abstract Climate control is one of the principal reasons to use a greenhouse. The efficiency of the control depends of the precision of the model that better describes the dynamics variables inside the greenhouse. Is presented a modification of a climate model in an greenhouse in order to include the effects of: air density variations due to humidity changes, the humidity addition by nebulizers, the use of shade cloths and the use of forced ventilation. Such effects are required for greenhouses located in the north-east region of Mexico, because the warm extreme climate makes the use necessary of these elements like economic resources of cooling, being essential to include in the model the above mentioned effects. The introduced modifications are validated by comparisons between real measurements carried out in a greenhouse in this region of Mexico through of simulations. The results in section 5 show that the proposed model has a better behavior when effects mentioned are included on sections 3 and 4.

Effect of air density variations on greenhouse temperature model

Basically, a greenhouse temperature model is determined based on the balances of mass and energy. In most of the available models, the air density is considered constant. This fact limits the model because of the natural existing relationship between the air density and air humidity. In this work a way to include the effect of air density variation in a greenhouse temperature model is proposed. Through the proposed model it is possible to obtain a better sensibility of the temperature when variations in the air density are present. The pertinence of the proposed extension is analysed via simulations. The results show that the temperature calculus in the greenhouse can be improved when the air density variations effect is considered. As a consequence, strong humidity variations, such as the use of nebulizers inside the greenhouse will affect the prediction calculus of the temperature, which is why they must be taken into consideration.

MODELING AND VALIDATION OF A GREENHOUSE CLIMATE MODEL

Abstract In this work it is proposed an extension to the Greenhouse climate model given by (Tap, 2000). The extension considers the effect of humidity in the air temperature as well as some terms related to the use of fogs, shade cloth and fan. The introduced modification is validated using measurements of a greenhouse in north west Mexico. The results show that the proposed model is adequate to simulate the climate behavior of the Greenhouse.

Solar radiation in urban projects: financial analysis of a photovoltaic system for a habitation house in the metropolitan area of monterrey, nuevo leon, mexico.

Los sistemas Fotovoltaicos se han presentado como una alternativa a la sustitucion del consumo de energias fosiles en el desarrollo de los Proyectos Urbanos alrededor del mundo. Su implementacion depende de factores con alta variabilidad, como la cantidad de radiacion solar que llega al suelo, el clima en la zona, las costumbres de consumo, entre otras. Todas ellas son funcion directa de la ubicacion geografica donde se ubique el proyecto. Ademas, en la mayoria de los casos el factor economico es el que determina finalmente la factibilidad de implementacion. Asi, en el presente trabajo de investigacion, se efectua un Analisis Financiero de la implementacion de un Sistema Fotovoltaico para dos casas, una con consumos bajos y la otra con consumos altos, en la zona Metropolitana de Monterrey, Nuevo Leon, Mexico. En donde se tome en cuenta todos los factores involucrados. Con los resultados se elaboran tablas de amortizacion, en las que se establece el numero de anos necesarios para recuperar la inversion, con ellas es posible evaluar economicamente el uso de paneles fotovoltaicos que aprovechar el recurso solar en Desarrollos Urbanos en el area de estudio.

Influence of Air Density Variations in the Climate of a Greenhouse

Abstract Climate control is one of the principal reasons to use a Greenhouse. The control task requires of a dynamic model of the climate variables in the Greenhouse. There are different Greenhouse climate models in the literature, some of them include not only the air temperature, soil temperature but also the effect of the crop, CO2 concentration and humidity (Tap, 2000). In order to improve the existing dynamic climate models an approach to consider non constant air density in the climate model of a Greenhouse is proposed. The effect of variations in the air density, due to humidity, is modeled and included in a version of the climate model of (Tap, 2000). The effect of the proposed modification on the Greenhouse climate variables is shown via simulations. A comparison between the proposed approach and one with constant air density is discussed.