Friday, February 15, 2013

New Old AC Technology

Old ideas combined with new material technologies may provide huge energy savings from a different type of air-conditioning system.

A typical air conditioner cools the air and dehumidifies it all at once, but not in a controlled way. The limit to how much drying can be achieved depends on how much water condenses on the evaporator coils as the air passes through. This so-called "wet-bulb limit" is the reason typical evaporative coolers either can't cool things down enough or can't create a truly comfortable space when there is a lot of heat and humidity in the air.

By contrast, DEVAP can provide cooling in any climate. The first stage wrings out all the moisture in the air. Doing so lowers the effective temperature limit the indirect evaporative cooler can achieve. It has a wet-bulb effectiveness of 125% — a huge boon compared to most current technology that has tried to get as close as it can to 100%.

DEVAP has several other advantages over conventional cooling, including:

  • There is no need for environmentally damaging working fluids such as the chlorofluorocarbons, hydrochlorofluorocarbons, or hydrofluorocarbons used in vapor compression systems.
  • The working fluids in DEVAP are environmentally benign: water and a strong salt solution for the desiccant.
  • DEVAP allows independent control of temperature and humidity, something that is not possible with conventional A/C unless an expensive overcooling and reheating process is employed.
  • There is no need for a compressor or large amounts of expensive copper coils.
  • DEVAP contains fewer moving parts in the form of simple low-pressure pumps and fans.
  • Vapor compression A/C has been incrementally improved for over 100 years, so there are few low-cost energy improvements left for that technology.
  • As efficient as DEVAP already is, there is lots of "thermodynamic room" for cost-effective efficiency improvements.