Thermal energy use for dehumidification of a tomato greenhouse by natural ventilation and a system with an air-to-air heat exchanger

Abstract

The aim of the study was to estimate the amount of thermal energy used for dehumidification of a naturally ventilated tomato greenhouse and to estimate how mechanical ventilation with the use of a heat exchanger recovering heat from the exhaust to the supply air may decrease the energy use. Measured use of thermal energy in a naturally ventilated tomato greenhouse was compared to modelled values using Powersim® software. By the help of the model an estimation of the amount of energy used for dehumidification was made for the months April -September. A non-hygroscopic rotary air-to-air heat exchanger was studied, and its temperature and moisture efficiencies were measured. Modelling for leaf area index (LAI) 3.5 and 4.0 m 2 m -2 indicated that 23 and 29% of the total thermal energy was used for moisture removal respectively. Modelling for the heat exchanger indicated thermal energy savings of 15 and 17% for the same LAI respectively.

A New Online Computer Program (Bidasys) for Ordinary and Uncertainty Weighted Least-Squares Linear Regressions: Case Studies From Food Chemistry

“…Chemometric techniques have become an important tool in modern analytical chemistry for designing experiments, achieving instrumental calibrations, and ascertaining the quality (precision, accuracy, and uncertainties) of analyses in a wide variety of chemical matrices (Miller and Miller, 2010;Verma, 2016). In food chemistry, many authors (e.g., Raco et al, 2015;Fernández et al, 2016;Giordani et al, 2016;Maslak and Nimmermark, 2017;Foereid, 2017) have used linear regression models. Furthermore, some other publications where the OLR model was applied are as follows: Moreno-Rivas et al (2016) in biosorption of cadmium from aqueous solution by baker's yeast; Borges et al (2017) in analysis of buffalo milk; Gómez-Favela et al (2017) in modelling of water absorption in chickpea seeds; Chaparro et al (2017) in selection of the process parameters and drying protectant to granulated bioproducts based on microorganisms; Fuentes-Ortega et al (2017) in study of the process variables of microencapsulation sesame oil by spray drying; Pérez-Grijalba et al (2017) in study of the bio-functionality properties of blackberry juice; and Xu et al (2017) in seasonal and annual variations of atmospheric Hg and Pb isotopes in Xi'an, China.…”

Comprehensive Review on Climate Control and Cooling Systems in Greenhouses under Hot and Arid Conditions

“…Natural ventilation can be considered as a passive cooling system since it is based on a greenhouse design that does not resort to the use of equipment. Many works have been carried out on natural greenhouse ventilation systems, which are controlled by the window openings at the side-wall and roof levels [68][69][70][71][72]. The researchers found that the climate of greenhouses is highly impacted by the rate of the air exchange through natural convection, which mainly depends on the area of the openings.…”

“…Accordingly, natural ventilation is not sufficient to maintain the desired climate and it becomes more energy intensive, especially in cold periods [5]. For instance, in Sweden and Spain, the energy consumption designed for greenhouse dehumidification via natural ventilation is estimated to be between 20 and 30% of the total energy consumption [5,71,73].…”

“…According to Amani et al [5], operating the air-to-air exchanger during the early morning and in the summertime becomes more economically relevant, as it requires more ventilation input to increase the dehumidification capacity. A rotary air-toair exchanger, which was modeled by Maslak and Nimmermark [71] and was intended for greenhouse dehumidification, exhibits around a 70% effectiveness. They found that, compared to natural ventilation, this process leads to a reduction of up to 17% of the overall energy consumption.…”

Opportunities for Implementing Closed Greenhouse Systems in Arid Climate Conditions

“…According to Maslak and Nimmermark [93], implementing an air-to-air heat exchanger for dehumidification reduced energy use in a closed greenhouse in Sweden by up to 17%.…”