BES Computation for Periodical Energy Load of Greenhouse with Geothermal Heating System

Greenhouse requires a lot of energy cost to maintain internal environmental conditions suitable for crops. The applications of renewable energies in the greenhouse have been concerned to reduce energy cost comparing to the fossil fuel consumption. For the optimum operation of heating system combining renewable energy and fossil fuel, heating and cooling load should be quantitatively investigated according system characteristics. Building energy simulation (BES) is a promising simulation tool to calculate real-time energy load considering time-dependently changed external weather conditions. The objective of this research is to calculate real-time energy load of an experimental greenhouse located in Namwon, Jeollabuk-do, Korea installing geothermal heating system. The greenhouse was a seventeen multi-span Venlo-type with 6.4 m width and 93 m length growing paprika, the heating and cooling loads were computed by TRNSYS (version 16, Wisconsin, USA) software at the same configuration and operating conditions. To validate the developed BES model, the energy load of the greenhouse computed by BES was additionally compared with diesel consumption resulting in a good agreement. Then the energy load was computed by the BES model when the greenhouse system was upgraded with the geothermal heating system with 240 RT (refrigeration-ton) heat pumps. The results showed a decrease of operating cost including electricity and diesel by 80% comparing to the greenhouse without geothermal system. Computational fluid dynamics (CFD) was also used to analyze internal thermal condition in the greenhouse using geothermal energy through various types of heating systems and circulation fans. The thermal uniformity could be improved by 42.4% using heating pipe and by 81% using both heating pipe and circulation fans.