Geothermal heating system for Jordanian greenhouses

Abstract

Protective cultivation is widely used nowadays in order to increase crop yield by creating the optimum conditions such as temperature, humidity and CO2 content, irrespective of outside conditions. Since plant production doubles for every 10 degrees increase in temperature to a certain limit, this makes temperature a very important factor for optimum plant growth. In order to keep the greenhouse temperature constant during changes in outside conditions, heating and often cooling are required. Heating of a greenhouse can be done using different systems and design procedures. In this report two methods were used for calculating the heating load required, the first method (static method) includes calculations of heat losses due to infiltration and conduction through the greenhouse cover at a single design point, which is the minimum outside temperature. It also assumes the greenhouse to be empty with no plants in it. This method also disregards moisture transfer and assumes air to be dry. The second method is rather complicated and requires computer simulation but it incorporates all energy and mass transfer to the greenhouse and gives results based on true outside conditions. A comparison between the results of the two methods was made. It was clear that the simple method in greenhouse heating design with a 10% safety factor can be used with sufficient accuracy and, thus, the use of complex relations are not needed.