Abstract
Greenhouse cultivation is a method of agricultural production that, despite advantages such as increased water-use efficiency, higher employment, greater yield per unit area, production of higher-quality crops, off-season production, and the ability to schedule planting according to market demand, is highly dependent on energy consumption due to off-season production. Previous studies conducted in the country, both before and after the implementation of targeted subsidies, indicate that the largest share of energy consumption in greenhouses is related to the heating system. Considering national development plans aimed at optimizing fuel consumption in production units, it was essential to calculate the actual fuel consumption in greenhouses across different regions of the country with varying structures, coverings, and cropping patterns, so that in the event of adjustments in energy carrier prices in the coming years, minimal adverse impact would occur in this sector. Accordingly, in a national project at the Agricultural Engineering and Technical Research Institute, the theoretical heating energy requirements for various regions of the country were calculated. The results for greenhouses in Isfahan Province indicate that, on average, approximately 13.2% of energy is consumed excessively. Regardless of the greenhouse location or crop type, fuel consumption can be reduced through effective management practices. Additionally, adopting climate-based management strategies in the province can slow the rate of energy consumption increase alongside the expansion of greenhouse cultivation.
EXTENDED ABSTRACT
Introduction
International statistics indicate that by 2050, the world's population is expected to reach approximately 10 billion people, with the majority residing in developing countries. This population growth will make the need for energy, water, food, and interaction with the environment the top priorities of humanity in the coming decades. For this reason, scientists have focused their attention on compensating for food shortages by increasing yields per unit area and using minimal production inputs (higher production efficiency).
 The introduction and use of high-yielding and transgenic varieties, the application of various types of chemical fertilizers and micronutrients, the use of chemical pesticides, and the cultivation of greenhouse crops are among these solutions. Given Iran's size, it appears to be an ideal region for the advancement of greenhouse cultivation in West Asia, where robust production of greenhouse products will not only satisfy domestic demands but also significantly contribute to the export of non-oil commodities, generate foreign exchange, and enhance the agricultural sector's trade balance. 
 The results of reports on the study of energy consumption in various greenhouses across the country have shown that the largest share of energy consumption in Iran is related to the energy required by heating systems. In a national project at the AERI, the amount of heating energy required for different regions of the country was calculated. Finally, solutions for optimizing fuel consumption in different greenhouse structures were presented. In this article, the results related to greenhouses in Isfahan province were presented and analyzed.
Material and Methods 
In this project, according to the technical specifications of greenhouses in different regions of the province with different climates and the desired cultivation pattern, the amount of heating energy required was calculated theoretically. For this purpose, a questionnaire was initially prepared, consisting of different sections including greenhouse information, structural information, and fuel consumption information was prepared. After validation, these questionnaires were completed in 25 greenhouses in Isfahan province. Then, using the technical specifications of the greenhouses, the amount of heating energy required (theoretical) was calculated and compared with the actual fuel consumption of the greenhouses visited.
Results and Discussion  
The results showed that regardless of region and crop, double-layering the greenhouse cover reduced fuel consumption. It showed the annual fuel consumption of a single-layer greenhouse with a high height (height from the eaves 4) and a rose crop in cold regions would be about 38.1 liters per square meter, which would be reduced to 26.7 liters per square meter by using double-layering the greenhouse cover. Another point obtained is the relationship between fuel consumption and the type of plant selected. The lower the heating requirement of the plant inside the greenhouse, the more significant the reduction in fuel consumption. In a double-walled greenhouse with a tomato crop in temperate regions of the province, diesel fuel consumption would be approximately 26.8 liters per square meter per year. In contrast, if the plant inside the greenhouse were changed to cloves, the amount of fuel required would be reduced to 14.8 liters per square meter.
 The results of calculating fuel consumption in a greenhouse with a medium-height structure were also similar, and regardless of the type of region and crop, double-layering the greenhouse resulted in reduced fuel consumption. It showed that the diesel fuel consumption of a single-layer greenhouse with a rose crop in cold regions of the province would be about 34.8 liters per square meter per year, which would be reduced to 24.4 liters per square meter by using double-layering the greenhouse cover or in a double-walled greenhouse with a tomato crop in temperate regions, the diesel fuel consumption would be about 24.5 liters per square meter per year. In contrast, if the plant inside the greenhouse were changed to cloves, the amount of fuel required would be reduced to 13.5 liters per square meter. The results of calculating the fuel consumption in a greenhouse with a short-height structure (height from the eaves 2) also followed the same trend. It showed that the annual diesel fuel consumption of a single-layer greenhouse with a rose crop in cold regions would be about 33 liters per square meter, which would be reduced to 23.1 liters per square meter by using two layers of greenhouse cover or in a double-walled greenhouse with a tomato crop in temperate regions, the annual diesel fuel consumption would be about 23.3 liters per square meter. In contrast, if the plant inside the greenhouse were changed to carnations, the amount of fuel required would be reduced to 12.8 liters per square meter.
Conclusions
The results of past research in the country, both before and after the targeting of subsidies, show that the largest share of energy consumed in greenhouses is related to the energy required by the heating system. Therefore, it was necessary to calculate the actual amount of fuel consumption in greenhouses to optimize it as much as possible, so that if the price of energy carriers is adjusted in the coming years, the least damage will be done to this sector. For this reason, in this national project, the technical specifications of greenhouses and cultivated plants were used to calculate the amount of heating energy required for different regions of the country. In this paper, the results of fuel consumption in various commercial greenhouse structures in Isfahan Province are presented. The results of greenhouses in Isfahan province indicate an average overconsumption of 13.2% in the province. Regardless of the type of greenhouse construction and crop, greenhouse fuel consumption can be reduced through effective management methods. Additionally, by leveraging the province's climate, the trend of increasing energy consumption, along with the development of greenhouses, can be slowed down.
Acknowledgements
This project was carried out with the joint support of the Ministry of Agricultural Jihad and the Fuel Consumption Optimization Company by the Greenhouse Engineering Research Department of the Agricultural Engineering and Technical Research Institute in 13 provinces of the country.
Data Availability Statement
Not applicable.
Ethical Considerations
The authors have observed ethical principles in conducting and publishing this scientific work, and this is confirmed by all of them.
Conflict of Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Funding Statement
This work was supported by the Ministry of Jihad-Agriculture.