Abstract
Greenhouses are high energy-consuming and anti-seasonal production facilities. In some cases, energy consumption in greenhouses accounts for 50% of the cost of greenhouse production. High energy consumption has become a major factor hindering the development of greenhouses. To improve the energy efficiency of the greenhouse, it is important to predict its energy consumption. Furthermore, high energy consumption reduced the quality and increased the risks of production. Consequently, study about energy analysis in greenhouses is required due to the costs and greenhouse gas emissions from fossil fuels used in heating systems in greenhouses. In this research, the general objective is to achieve a sustainable development in providing energy, and the potential of closed greenhouse systems in the climatic conditions of Tehran. In this system, the natural ventilation for cooling, and dehumidifying the greenhouse is replaced by active systems, and the thermal energy removed from the greenhouse can be reused, which diminishes the total thermal load. The main aim of this study is to analyze energy in three types of conventional greenhouse, semi-closed greenhouse, and ideal closed greenhouse. Therefore, a transient model has been designed using the TRNSYS software to evaluate the performance of different greenhouses, and the accuracy of the proposed model is confirmed using measured data in the reference greenhouse (conventional greenhouse). The results showed that the thermal demand in the closed greenhouse compared to the conventional greenhouse is about 2 times lower, and the cooling requirement in that kind of greenhouse is approximately triple higher than the conventional greenhouse. Also, in the semi-closed greenhouse, different ventilation rates will be used to regulate the interior humidity level, the surplus energy ratio was studied for the ventilation rates of 0.5 h−1, 1 h−1, and 1.5 h−1. The results showed that the surplus energy ratio in the greenhouse is strongly dependent on the controlled ventilation rate. Here it values with using a 0.5 h−1 and 1.5 h−1 are reduced about 34% and 67% respectively compared to the ideal closed greenhouse.
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