Thursday, October 2, 2008

Thinking About Radiant Cooling & De-humidification

It appears that geothermal technology is already being used in Thailand, and using radiant cooling through pipes in the floor/walls/ceiling is one way to complete the system. The water supply from geothermal pipes can also be connected into a more standard HVAC system. This Wikipedia article on heat pumps has a good summary.

A problem with radiant cooling is surface condensation. It is not clear if this has been addressed in the systems cited above. This house, which uses radiant floor heating and cooling, also closely regulates the floor temperature and uses "dry air delivered along its floors at ~68 degrees f all year-round (cf.: displacement ventilation). It uses a dehumidification coil and reheat coil in summer, and a heating coil in winter. In summer, the flow rate is sized for adequate dehumidification and fresh air" Are there less intensive ways to control condensation and humidity that would be viable in Thailand?

There are currently 2 ways to dehumidify air in buildings 1.)
condense the moisture onto a cold surface (the same process that presents a problem with radiant cooling!) This is how air conditioning systems and small free standing dehumidifiers work...and the collected water can be re-used on site. 2.) machines that use desiccants (solid or liquid) to remove water vapor from the air--these are the same substances found in those little packets you find in your shoebox.

This is a simplified explanation. The following links are helpful:

HPAC Engineering

World Changing
Culture Kitchen

1 comment:

David Gould said...

This is very helpful, Valerie. For CTS it would be good to think in terms of a lower storey where there in enclosure and a controlled environment, using geo-cooling; and an upper storey for teaching and other spaces where we rely on passive cooling using cross-ventilation. As you say condensation in the wrong place could be a major problem, particularly in the library. So I wonder if we should combine geo-cooling with an element of Air-con in that area only; the geo-cooling could reduce the surface temperature of the floor, and the air-con could be designed to remove the surplus condensate. Maybe other rooms on the lower storey (seminar rooms, offices etc) will also need some A/C to deal with the excessive heat in April and May, but the geo-cooling could still help to reduce the cooling load. The tricky thing will be to design this to accurately model performance.