did you read my post ? i said you fill a header tank , a big household tank is around 50 gallons , put in some corrosion inhibitor and that water will last years in a sealed system
im not about to bust out the figures as i dont know all the values , but since its the same principle used in cars boilers radiators around your home and instant water heaters then suffice to say they are very efficent of tranferring heat to water , and removing that water is achieved by the pump and pipework to wherever you have another heat exchanger for best results
but i done a similar but much smaller scale system years ago to watercooler my pc's cpu using a central heating pump in the loft and 4 coils of 10mm copper coiled up in the cold water storage tank , my temps were always below my rooms ambient temp this caused some condensation problems and i had to go to alot of effort to insulate my cpu and motherboard so as not to cause a short
that thing u saw way back ? yeh thats a heat exchanger ! , if you go the chiller route as i said it will get more expensive obviously
as for numbers e.g. prices , go check yourself on a tank plumbing and a pump , then find a suitable heat exchanger to do it , little research will answerthe finer points
i know myself what i would do and it would take a fair bit of research if i do decide to go down this route i will post it up
but i have decided to run a 6 inch soil pipe from my growroom upstairs down through the walk in cupboard in my bedroom and into the center of under my house, from there the exhausted air can disperse around under the floors