Efficient Cooling for Agricultural Greenhouses in Hot Climates: A Novel Water Light Filter Design

Abstract The use of agricultural greenhouses in hot climates requires transparent enclosures to enable cooling for optimal plant growth. However, the cooling process incurs high water and energy costs due to solar gain and heat trapping. To address this issue, a novel enclosure design featuring a layer of liquid or water solution between two commercial grade glass layers has been proposed. This water solution absorbs thermal radiation and can be circulated through an active heat dissipation system. Carefully selected dyes can also be added to enhance water filter performance, allowing sufficient photosynthetically active radiation (PAR) through to the plants while blocking more of the non-PAR radiation. To evaluate the efficiency of the proposed filter, a shading filter was used as a benchmarking scheme. The tests were conducted using clear water, mineral oil, and water with four commercially available pigments. Results indicated a reduction in the thermal load ranging from 31-62%, while the reduction in the photosynthetically active portion of the solar spectrum ranged from 32-79%. The clear water filter performed the best, blocking 45% of the thermal load while allowing 69% of weighted PAR radiation. This allowed for an additional 14% of PAR radiation compared to an equivalent 45% transparent shading device. This new liquid filter design is effective in reducing cooling costs for agricultural greenhouses in hot climates, while still allowing for optimal plant growth. The clear water filter was found to be the most effective in blocking non-PAR radiation while still allowing sufficient PAR for the plants. However, there is potential for future work to identify additives that could enhance the filter’s overall performance. Engineering and technoeconomic development should be pursued to implement this technology for practical use in the field.