熱泵應用於植物工廠養液降溫與室內空調

Abstract

植物工廠作為解決全球暖化、可耕地縮減、糧食短缺、淡水資源與能源匱乏及食品安全等全球性問題之高潛力技術之一，近來頗受矚目。然而，在室內完全使用人工光源進行作物栽培時，維持植物生長所需光量與維持室內溫、溼度所需空調系統的能源負荷為操作成本之最大支出。降低此部分的光熱成本為首要研究課題與成功關鍵。 本研究旨在針對空調系統的能耗進行探討，期望能透過熱泵製冷系統的使用，在降低環控室內的空氣溫度與降低栽培所需的養液溫度之間，找到一個平衡點，使整體耗能為最小。本研究針對A-W與A-R兩型熱泵系統進行探討，前者透過板式熱交換器將水槽內的水與蒸發器內的冷媒做熱交換，後者則是直接將蒸發器置於水槽內對水體做降溫。熱泵製冷系統不論是哪一型，其性能係數 (COP) 若是比市售空調系統低，則沒有應用空間。研究中使用之A-W型設備的COP 遠高於A-R型。本研究應用熱泵製冷系統確立了可以同時用於養液與室內空氣的降溫。 本研究也針對單一的栽培層架進行小區域降溫，避免針對整間環控室作降溫，以節約能源消耗。溫控栽培層架的設計，配合水冷排、風扇、沉水馬達、水槽與養液槽的使用，將熱泵製冷系統所製造的冰水，用於空間內與養液的降溫，允許各層空間內可以有不同或相同的氣溫，提高應用於研究上的彈性。

Facing the global problems such as global warming, exploded population, reduction in cultivated land, food shortage, fresh water and energy crisis and food safety, plant factory is considered one of the promising methods to solve the problems, thus catching lots of attention recently. However, grow plants indoor takes lots of energy to provide light needed by the crop and to maintain proper temperature and humidity. The cost on artificial light plus the cost on air conditioning system is the major operating cost, thus reducing these light-heat related cost is the major task for the related research and successful business. This study aims at reducing air conditioning cost by applying heat pump system. The goal is to find a balance between reducing air temperature and nutrient temperature. Traditionally, only air temperature was controlled. This study tried to control the nutrient temperature and let the air temperature several degree higher and to compare the energy consumption throughout the entire growth period. Two types of heat pump cooling system were used. A-W type used a plate type exchanger to exchange energy between water in tank and refrigerant in evaporator. A-R type put the evaporator in water tank directly. No matter which type was used, the COP of the system is the major concern, if the COP is less than the commercially available Air conditioning system, there is making no sense to use it. In our experiment, the COP of A-W is much higher than A-R type. This study successfully set up a heat pump cooling system suitable or air cooling and nutrient solution cooling at the same time. A cooling system for multi-layer bench was established. The system consists of water cooled heat exchanger for each layer, fans attached to the heat-exchangers, submersible pump, nutrient tank and tap water tank which cooled with heat pump cooling system, and can be used to keep temperatures of the air within each layer and temperature of nutrient for the whole bench in different level, thus making it a flexible system for research.