The Seawater Greenhouse design is not a conventional greenhouse. It cools rather than heats a crop, it is an open design, rather than a conventional "closed" design.
The system, as designed by Charlie Paton, uses evaporative cooling in the greenhouse. Essentially they have a cardboard wall, sort of like a thick honey comb with holes through it, over which they pour seawater. The air is pulled through the wall by large relatively slow fans. When the air moves through the "honey comb" wall, the air changes direction (30 degree angle channels). Particles and insects in the air essentially get stuck in the seawater. Seawater is particularly bad for insects and other small pests as the salt clogs up the exoskeleton and the breathing channels when the water evaporates.
Even though the greenhouse was standing in an area of vegetation with a significant insect population outside, we hardly saw any insects on the inside. But you could often find quite a few insects in the seawater tanks used to hold the water for the evaporators. The stable climate created in the greenhouse and the seawater "barrier" created by the evaporators means the pest insect pressure is lie and you can easily control it with natural enemies (bio control). (There where poisonous spiders in the canopy of the crop but they don't affect the crop, but act as biocontrol. Just don't let them bite you.)
Plants grow much better in a cooler and high humidity environment. The plants don't have to put so much effort into transpiration to keep an acceptable temperature for photosynthesis. The evaporators with seawater handles both of those things.
The temperature during my visit peaked on Christmas Day at 43 C, but inside the greenhouse it was a much more acceptable 35 C. (We had our Xmas dinner just behind the evaporators, the most pleasant place in Port Augusta at that point.) The energy used for this cooling primarily comes out of the water and the surrounding air. Some energy is used for pumping water. Without the evaporative cooling the temperature in the greenhouse would have been at a level which would have killed the plants. During my visit the plants and crop grew so fast that we had to help harvesting to keep up.
The evaporators are also covered by sea salt, which is hydroscopic (absorbs water) which means that when the temperature drops at the end of the day you don't get water (dew) collecting on the plants. This is important as dew on the plants and produce allows botrytis (mold) to grow and potentially destroy the produce. This also avoids having to burn sulphur in the greenhouse to kill the mold.
[1] pictures from my wife during the visit https://www.flickr.com/photos/ankertje/7044271777/in/album-7...