جستجوی مقالات مرتبط با کلیدواژه « Greenhouse » در نشریات گروه « فنی و مهندسی »

Providing electrical, thermal and cooling energy in greenhouses is a very important issue. Due to the low efficiency of most of the conventional systems in greenhouses, the use of simultaneous production of electricity, heat and cooling (CCHP) systems has been highly considered in recent years. The main purpose of this article is the technical and economic feasibility of CCHP technology for use in a greenhouse in Tehran. In this research, a cucumber greenhouse with an area of 1 hectare, which consists of two structures of 0.5 hectare, has been analyzed and investigated. In order to analyze the technical-economic system used, calculations for four scenarios including the basic and conventional system, CCHP with absorption chiller and selling electricity to the grid, CCHP with absorption chiller and self-supply and CCHP with compression chiller and self-supply accepted. According to the results obtained for each scenario as well as the comparison of the selected scenarios, the greenhouse considered for the implementation of the CCHP system is not economical. The results of the research show that in case of using the CCHP system with absorption chiller and selling electricity to the grid, in order to make the system economical, the minimum rate of buying electricity from these units should be 3223 Rials per kilowatt hour. In the CCHP system with absorption chiller and self-supply, if the location of the greenhouse is such that 176 kilometers of transmission line is needed, this scenario becomes economical.

In some places with hard winters, the heat from sunlight and stored in the soil may not be enough to heat the greenhouse. In such a situation, the additional heat needed must be provided by heating systems. The purpose of this study is to evaluate the effectiveness of the heating system in a glass greenhouse with side air vents and mechanical fans in both night and day periods. In this study, seven different greenhouse designs have been investigated in two periods, day and night. In the daily period, by changing the pressure of the fans, tried to obtain the best condition for providing the appropriate temperature in the greenhouse. Also, in this period, the effect of sunlight on the flow field and temperature changes inside the hall were also investigated. In the night period, the amount of temperature changes by opening and closing the side valves and changing the temperature of the hall floor has been studied. The results of the research show that a greenhouse with a pressure difference of 100 pascal during the day and a greenhouse with a floor temperature of 323.15 K and side vents closed at night have more suitable conditions for growing plants in the off-season.

This research simulates a geothermal heat pump system needed to grow hemp plants for medical applications in Ardabil, Iran. Supplying energy for the cultivation of hemp plants can sometimes impose many costs. On the other hand, it is impossible to ignore the release of carbon dioxide to produce energy for the cultivation of this plant. In this regard, in this article, we will check the performance of a geothermal heat pump system and evaluate its output for cultivating the Hemet plant in the greenhouse. The results show that considering the cultivation of industrial hemp twice a year, the equivalent of 17.74 to 26.62 tons of carbon dioxide is saved per hectare. According to the 4 hectares under cultivation in the designed greenhouse, a figure equal to 70.96 to 106.48 tons of carbon dioxide per year is stored due to hemp plant cultivation in the greenhouse. In addition, using a heat pump system equivalent to 6.64 tons of oxide prevents the emission of greenhouse gases through renewable energy, which creates a negative carbon greenhouse system. Also, the heat capacity of the geothermal pump to supply energy to the greenhouse is equal to 570.2 kilowatts, which is dependent on the height and optimal temperature of the greenhouse. With the increase of these design parameters, the required heat capacity also increases.

Today's world is moving towards the use of clean and renewable resources due to the limitation of fossil resources fuels and the environmental problems caused by the consumption of non-renewable fuels. Solar energy is one of these sources that has particular importance due to its proper distribution around the world and its compatibility with the environment. Drying the agricultural products under the sunlight is one of the first uses of this energy. The use of this method leads to the high losses, low efficiency, and poor quality of dried product. To overcome these problems, researchers have designed, built and studied the variety of greenhouse solar dryers. In this study according to different criteria, the introduction and classification of greenhouse dryers have been studied and there is attempt to provide the complete aquantane with this technology for reader. In general, this article is a comprehensive resource for researchers, farmers, and investors that it has been compiled to improve the expansion and industrialization of this science.

The purpose of this study is to identify the possibility, barriers and requirements of utilization renewable energy in the greenhouses of branch flowers) flowers and ornamental plants( of Khuzestan province. Due to high energy consumption and high costs in greenhouse production, this study was conducted to evaluate the possibility, barriers and requirements of using renewable energy. The research method was applied and survey and to do it, a researcher-made questionnaire, the validity and reliability of which was determined, was distributed among 165 greenhouse users of branch flowers in Khuzestan province as a statistical sample. Validity was obtained through the Patel of Experts and reliability was obtained through the Cronbach's alpha coefficient. Based on the research findings, all the requirements for the use of renewable energy were identified. Also, based on the results, 42.1% with a frequency of 59 people expressed the possibility of using renewable energy in greenhouses at a moderate level. Findings showed that there is a significant relationship between educational, technical, economic, social, policy and cultural requirements with the possibility of using renewable energy. The findings also showed that there is a significant relationship between educational, technical, economic, social, policy and cultural requirements with the possibility of using renewable energy. Further factor analysis of barriers to the use of renewable energy showed that educational and managerial poverty, poor support services, incompatibility with greenhouse conditions, lack of financial support, lack of technical facilities and lack of knowledge and awareness are the most important barriers and non-use of these energies.

Today's energy consumption is increasing in developing countries. Most countries generate electricity from fossil fuels. Combined cycle plants produce 1 kg of 660 g of carbon dioxide gas. In study Firouzkouh province of Tehran province has been studied to use a small turbine to supply electricity to greenhouses. According to the study, Firuz Mountain has a wind density142 (w / m2) at a height of 10 meters from the ground. In this The wind speed is 5.6 m/s. Due to the wind speed and wind density in the Firoozkouh region, wind turbines of 10 and 5 kW have been used for further investigation. The 10 and 5 kW Hummer turbines produce 2394 and 1532 watts, respectively, with respect to the region's wind velocity, respectively. To reduce greenhouse costs, it is possible to invest in wind energy, while taking advantage of the environmental benefits of dispersed production and reducing the cost of greenhouse products in the long run. The reviews of this paper show that turbines 10 and 5 kilowatts of hammer in the Firoozkooh area and 10 meters high for installation and use.

Limitation of fossil fuel resources together with commitment to conservation of environments have caused the views to be focused on the use of renewable energy resources. Biogas is produced by the anaerobic decomposition of organic matter in WWTPs (wastewater treatment plants) and is considered to be a sustainable energy resource due to permanency of wastewater flow. This research focuses the process of biogas fuel engine implemented in Kashan WWTPs. This system can reduce the fuel consumption rate and use renewable energies in production of heat and electrical power reliable a part of processing consumption of WWTPs. Specifications of biogas production in Kashan WWTPs is taken as sample and the necessary elements for installation and construction of biogas fuel engine are described and then two cogeneration units are designed for producing 466 kW electricity and 556 kW heat.. Costs of installations and total capital investment required for this power plant is calculated about 270,000$, which can be returned in 4 years through sales of electricity and other by-products. Also using wastewater for producing biogas reduces greenhouse emission such as methane and carbon dioxide.

In this study, the performance of a solar greenhouse heating system equipped with a linear parabolic concentrator and a dual-purpose flat plate solar collector‏ was investigated using the Artificial Neural Network (ANN) method. The heat required for the greenhouse at night hours was supplied by the heat stored in the storage tank by the solar system during the sunshine time and  an auxiliary heater. A water pump was used to make a forced-flow through the concentrator assembly. While, a natural water flow occurred in the flat plate collector. ANN method was used to predict  the tank temperature and energy consumption from the heat storage tank and by the auxiliary heater. Network inputs were solar radiation intensity, ambient temperature, wind speed, collector surface temperature, greenhouse temperature, flow rate and time. About 80% of total data were used for training, 10% for testing and 10% for validation. The results indicated that the network topology of 7-15-1 with R² and MSE of respectively 0.98 and 0.00017 presented the best results for prediction of energy consumption from the tank. While the most suitable description for variations of energy consumption by the auxiliary heater and from storage tank was given by the network topologies‏ of 7-10-10-1 (with R² of 0.99 and MSE of 0.00014) and 7-5-15-1 (with R² 0.98 of MSE  of 0.00011), respectively.

In modern and big greenhouses, it is necessary to measure several climate parameters to automate and control the greenhouse properly. Monitoring and transmitting by cable may lead to an expensive and stiff measurement system. Since, Wireless Sensor Network (WSN) is a distributed system that consists of small-size wireless sensor nodes equipped with radio and one or several sensors; it is a low cost option to build the required monitoring system. In this paper, we introduce and implement an intelligent monitoring system based on WSN by using Xbee modules. The Xbee Series 2 hardware uses a microchip from Ember Networks that enables several different flavors of standards-based ZigBee mesh networking. All gathered information by sensors, are sent to a remote center in form of GPRS packets through a GSM network and viewed by monitoring software. The proposed system has low power consumption, low cost and simple driver circuits. Furthermore, it can support various types of digital and analog sensors