people i know that what i ask here is a bit strange maybe because many of you dont need it but i need very much to know if there is any chemical material to drop it in the water and keep it cold with the ice method i have to change the ice every one hour please if someone can help me..
No. Such a chemical doesn't exist. Such a substance would re-write the laws of chemistry and physics. Often, someone thinks their need makes things possible, and that is never true.
You will have to limit the amount of heat that gets in. You can whitewash the greenhouse windows to let less sun in. You can ventilate, moving more air. You can mist the air, so the water carries away the heat with it as its ventilated away. All of this uses energy, which costs money, because the energy isn't available to do something else. No chemical exists that does work for us by mixing it with water.