The purpose of a greenhouse is to provide a controlled environment that promotes the optimal growth of high-value crops such as salad tomatoes, cucumbers, peppers, or flowers. With optimal conditions, the output per unit area can be increased by 10 to 20 times that of growing plants outside. Saltwater-cooled greenhouses provide suitable growing conditions that enable year-round cultivation of high-value vegetable crops even in desert conditions that can be very hot and cool, and humid, particularly at night and in the winter. They provide the climate and crop control typical of very high productivity commercial greenhouses while avoiding traditional cooling methods’ high environmental and economic costs.
Using seawater to provide evaporative cooling and humidification minimizes the crops’ water requirements and maximizes yields with a minimal carbon footprint. The basic principle is that the incoming air is conditioned through pads and pushed with fans into the growing environment using inflatable ducts under the crops. This ensures that the air is well distributed through the greenhouse. Therefore, the greenhouse is under positive pressure to prevent untreated air from entering the space. The air is pushed out through openings at a high level.
When it is hot outside, incoming air is pulled over evaporative pads with saltwater running over them. The hot air is cooled by evaporation to produce cool and humid conditions in the greenhouse.
When it is cool and humid outside, the greenhouse can be heated in a conventional way using heating pipes on the ground. In addition, waste heat from other processes in the SFP system can be used to evaporate water and create hot, humid air that is circulated through the roof cavity. As it cools, the moisture condenses to form fresh water and provide heat at night to the greenhouse. In this way, we can produce enough water to grow crops.
The most water-efficient cultivation and irrigation methods will be used to maximize the benefits of hard-won water resources in the SFP system. Standard in the commercial greenhouse industry, hydroponic growing methods will be utilized, which reduce water requirements by up to 50% compared to soil-based methods. A fertigation (fertilization + irrigation) system will deliver each plant with precisely the water and nutrients it needs, tailored to its stage of growth. The high-humidity environment of the greenhouse will improve water performance even further by significantly reducing the thermal and water stress on the plants. In effect, the evaporatively cooled greenhouse shifts the cooling mechanism by which plants regulate their temperature outside the plant and into the greenhouse infrastructure. Overall water requirements for evaporative cooling are not reduced – but because the cooling takes place outside the plant, seawater can be used instead of precious freshwater. Under these conditions, the plant can devote its internal resources to grow more fully, leading to higher yields and water efficiencies.