The Turks and Caicos Islands, like other carbonate islands, have a unique characteristic in terms of their groundwater temperature profiles. Carbonate islands are porous and essentially allow the surrounding ocean water to flow through the island underground. Specifically, we know that Grand Turk’s groundwater is saline and is not useful for drinking or agriculture. Groundwater temperature decreases with depth, following the ocean temperature-depth profile. This is unlike groundwater in continental regions where ground temperature increases with depth.
A key feature of our water-producing greenhouse design is that natural coolant, in the form of saline groundwater, pumped from four wells with depths of up to 500 m, where the water temperature is about 15 °C, has a temperature lower than the dew-point temperature of the tropical air. The coolant flows at a rate of 256 L/s through cupronickel tubing (known as water-chilled coils in the air-conditioning industry) causing atmospheric water vapour to condense on the tubing exterior. Because of the large surface area of the coils, about 200,000 L of fresh water per day condenses from the air drawn by fans through the greenhouse system. Using this natural coolant contributes to the sustainability of our design because energy is not consumed in cooling the air to cause dehumidification. The only energy cost associated with using the natural coolant is from electrical water pumps.
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