for ur guys info,im from malaysia and the climate here was hot and able to reach 40degree instanly.If i choose to use the aircond it will be more costly in term of billing.So i choose alternative way to make a simple project and able to works.Water pay here was not so high comparing with electricity.
hi Palin
I live in cambodia and have the same climate as that you have
it works better if you make from you're pipe work a grid system
use metal pipes (preferably copper or aluminium but steel would also do) and pump water throug it
metal are far superior of conducting heat/cold than any plastic
this grid system you will install under your roof plates and one side of the roof plates (underside inside your house) you put insulation with a reflective cover facing inside thehouse and so also your pipework grid
the storage tank (size should be calculated on the heat load of your room)
is preferably buried in the ground
that is the basic
you can go further by making a second system in the open air that you use in the night to pump water through to cool it further down in the night air
you will have to use solenoid valves if you want to have it all automatic and use temp sensors when you want to pump or not
how much is your budget to make this
i make these systems for heating up water (as a hobby) (also in my work i have to deal with it) but these systems are the same as that you want to cool down things
you can go prety far as it comes to the automation side of it
it's actualy a very nice project to do this kind of project micro controler based
Robert-Jan