Economic and Environmental Feasibility Study of Greenhouse Heating and Cooling Using Geothermal Heat Pump in Northwest Iran

Abstract

High energy consumption rate, reduce of product's quality and increase of the production risks, costs and emissions of fossil fuel consumption which are using in greenhouses heating systems, requires more attention to renewable and alternative energy systems such as geothermal heat pump. Geothermal ground source heat pump systems are one of the most energy efficient, environmentally clean, and cost-effective space conditioning systems available. Nevertheless, this can be attained by accurate design, competitive initial costs compared with conventional systems and proper climate and geological conditions. The main goal of this study is to examine the feasibility of Pashak greenhouse heating with geothermal heat pump (GHP) systems in Northwest Iran. Pashak greenhouse is located in East Azerbaijan (37 ° 58 'N, 46 ° 02' E), 1327 m above the sea level with 6120 m2 area. In this greenhouse crops are produced under hydroponic system. The monthly average fuel consumption of this greenhouse is 3,000 liters diesel per 1000 m2. In this study by investigations conducted and regarding the selected sample greenhouse, the best geothermal heat pump system is chosen and finally complete designing of system is presented as well and finally the economic and environmental application analysis of this system is covered. The input data includes different parameters such as: monthly average of greenhouse heat load, heat pump capacity (70kW), pipe type (11SDR), turbulent flow regime in the pipe, ground layers propertise and their heat transfer characteristics, ethylene glycol 20% with freezing temperature of -10 °C as a fluid for Horizontal and propylene 25% with the freezing temperature of - 10 °C as a fluid for vertical system. As a result, the designed geothermal heat pumps system can reduce 8123 kg of CO2 emissions, 255 kg NOx and 251 kg SO2 annually. The calculation shows that because of very low subsidized fossil fuel price in Iran particularly in agricultural and industrial sector the payback time is more than 20 years. By assuming the same subsiding value for geothermal heat pump the payback time reduces to less than 10 years.