CONTROL STRATEGY FOR THERMAL SCREENS IN GREENHOUSES: AN ALGORITHM BASED ON HEAT BALANCE
Thermal screens are known to reduce heating requirements of greenhouses and therefore are now becoming widely implemented. Previous studies have found that delaying the thermal screens opening after sunrise can increase energy savings. The objective of this paper is to develop an algorithm defining the optimal opening of thermal screens for minimizing heat losses. This control strategy is compared with a control strategy based on a fixed outside irradiance level. Different thermal screens properties are evaluated. Simulations are carried out for a south-facing attached greenhouse located in Montreal. Simulation results quantified the heating energy consumption and the potential energy that can be stored and utilized during the cold period of the year (October to April). A thermally massive north wall acts as a passive thermal storage and buried pipes in the ground are used for additional thermal storage. Results show that for closed greenhouses when excess energy is stored, a control scheme based on heat balance can increase slightly or significantly the total solar heat collected, depending on the type of blind used.
Bastien , D. and Athienitis, A.K. (2012). CONTROL STRATEGY FOR THERMAL SCREENS IN GREENHOUSES: AN ALGORITHM BASED ON HEAT BALANCE. Acta Hortic. 952, 501-507
greenhouse, control strategy, heat balance, thermal screens, emissivity, energy consumption