Simulation model development of the controlled environment greenhouse using TRNSYS program

Abstract

The goal of this research is to develop a computer model using TRNSYS for predicting the energy consumption and operating costs of strawberry plantations inside plant factories located in tropical climate regions. Experiments were carried out in a 25 m3 controlled environment room in Chiang Mai, Thailand. First, the experiments (cooling and non-cooling conditions) were carried out in the insulated room (wall composition: 4-mm SCG SmartboardTM, and 10-mm AERO-ROOFTM) which is located in an isolated outdoor area. To provide cooling, cold water flowed through copper pipes. The copper pipes with a diameter of 12.7 mm were used in the room. Since the cooling system could supply a small amount of cooling in the room, further experiments were performed in another fully insulated room, which is located on the ground floor inside of a building. There are 180 strawberry trees inside the room The strawberry trees are placed on four vertical shelves, each of which has three stacks. As a substitute for natural sunlight, a light-emitting diode (LED) grow light is introduced. There are 72 light-emitting diodes (LED) light bulbs (2 LEDs for 5 strawberry trees). An air conditioner was used to regulate the indoor air condition. The opaque polystyrene (PS) insulation panel with a 127 mm thickness was used as an insulation wall for the controlled environment room. A computer model was developed using TRNSYS (TRaNsient SYStem simulation tool) to match the physical conditions of the experiment room. It was then validated using the collected data. There are three main components of the room heat load: transmission, lighting. and evapotranspiration. The key finding is that the lighting heat load shares more than 96% of the total heat load. The evapotranspiration load increases when the LED is active. However, the lighting consumes only about 36% of total electricity consumption, while the air conditioner consumes 64%. More electricity adds to the air conditioner since the heat produced from the LEDs must be removed. During the strawberry runner stage, electrical energy consumption is the largest. Growing strawberry runners outside of the plant factory can save 40% on electricity consumption. The simulations were also performed in Southeast Asia countries (Thailand. Malaysia, Myanmar, Vietnam, and Laos). Growing strawberry trees in the plant factory located in Laos has indicated the cheapest operating costs owing to low ambient temperature and low electricity tariff.