Spain. A study to investigate how to improve greenhouse production with passive heating and cooling systems is being investigated in Spain by the Ministry of Agriculture, Livestock, Fisheries and Sustainable Development, through the Institute of Agri-Food and Fisheries Research and Training (IFAPA).
Specifically, the IFAPA Center of La Mojonera (Almería) is developing a project for the integration of sustainable technologies under greenhouse in the Mediterranean area that allows reducing climate stress in horticultural production. The production of greenhouse vegetables on this coast takes place in low-tech greenhouses, with low cost and energy consumption, and mostly lacking active climate control. Therefore, the results are subject to the evolution of the local climate, which often represents a major limitation for production and its quality.
The study, funded by the National Institute of Agricultural and Food Research and Technology (INIA), involves researchers from IFAPA, the University of Almería (UAL), the Cajamar Foundation and the Murcian Institute for Agricultural and Food Research and Development (Imida). The objective is the development of a technology that integrates a passive heating and cooling system into the greenhouse.
Thus, in the cold period, flexible polyethylene sleeves filled with water are arranged in the greenhouse that accumulate heat during the day to give it at night; activating a thermal display before sunset limits the loss of heat stored to the outside during the night. And for the warm period, a passive cooling system is incorporated that consists of textile screens of hydrophilic material, with good water retention capacity, installed in parallel to the cultivation lines that allow the evaporation of water, which generates an increase in humidity and reduces the temperature and the deficit of vapor pressure of the air; at the same time, the activation of a mobile shading mesh, activated during the central period of the day depending on the temperature and incident radiation, limits the heat load on the crop. Specifically, this project studies the influence of the integration of these systems on the greenhouse climate, production and quality of pepper fruit.
Experiments carried out previously show that the incorporation in the greenhouse of this passive heating system, in the cold period of the crop cycle, allowed to increase the temperature between 2.2 and 3.3 ºC with respect to the reference greenhouse. The system also avoided thermal inversion in the greenhouse with respect to the outside and improved the minimum thermal levels recorded in the reference greenhouse in a very unfavorable range for the crop (6-10 ºC). The effect of passive heating on the night temperature of the greenhouse air, although discreet, is an interesting advantage in cold periods in which night temperatures have been below 12ºC and, therefore, sub-optimal for the development and production of crops and has led to significant increases in production, around 15%.
The short-term heat storage system, installed in the greenhouses of the Mediterranean area, where the thermal regime is not rigorous during cold periods, is of interest as a sustainable method to improve the climatic conditions in the greenhouse and productivity. An experiment is currently being carried out in which the integration of the developed heating and cooling systems is evaluated.
Source: Junta de Andalucía.
