Numerical modeling and economic analysis of a ground source heat pump for supplying energy for a greenhouse in Alborz province, Iran

In this study, a 1000 m(2) greenhouse in Karaj, close to the capital of Iran, is considered and heat transfer between the greenhouse and its ambient as well as the heat gained from the sun are modeled. A ground source heat pump (GSHP) system is examined to meet the heating and cooling loads of the greenhouse over a year. To determine the capacity of the GSHP system in the heating and cooling mode, the governing equations of heat transfer between soil and water in pipes are numerically solved by the Crank-Nicolson method, and the simulation is carried out by developing new codes in MATLAB. The solution indicates that the longer the ground heat exchanger is, the higher the capacity of GSHPs will be. Based on this result, three diverse scenarios are defined for meeting the greenhouse energy demand. Afterward, a gas burning heating system and an evaporative cooling system, which are considered to supply the energy needs of the greenhouse, are economically compared with the GSHP system. The outcomes demonstrate that, due to the high price of electricity and heat pump units, and also low price of natural gas, using GSHPs for greenhouses in Iran is not cost-effective. (C) 2016 Elsevier Ltd. All rights reserved.