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Water-Heating Dehumidifier

Oak Ridge National Laboratory

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Technology Marketing SummaryA small appliance developed at ORNL dehumidifies air and then recycles heat to warm water in a water heater. The device circulates cool, dry air in summer and warm air in winter. In addition, the invention can cut the energy required to run a conventional water heater by an estimated 50 per cent. DescriptionConventional electric water heater designs have reached the limit of efficiency. The ORNL technology provides an innovative and highly cost efficient way to channel heat from warm, moist air to a hot water tank. The small appliance is ideal for the mobile homes market, where electric water tanks often stand against an outside wall. Additional ducting could allow a dehumidifier-water heater in one mode to circulate cool, dehumidified air in summer, while heating water in the tank.

In winter, in a second mode, the system could bypass the water tank and circulate the warm, dehumidified air. In this device, a fan draws air across an evaporator to produce cooled and dehumidified air. Heat taken from the air is absorbed by a refrigerant at the evaporator and then pumped to a condenser, where it is used to heat water. When the tank of the water heater is full of hot water, the device switches back to dehumidifier mode.
  • Qualifies for the EnergyStar rating as a dehumidifier
  • Adding the invention to an electric water heater could cut the energy needed for heating water by an estimated 50%
Applications and Industries
  • Dehumidifier and electric water heater applications
  • Mobile homes
More InformationInventor"
John J. Tomlinson
Energy and Transportation Science Division
Oak Ridge National Laboratory
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Patent 7,028,490
Water-heating dehumidifier
A water-heating dehumidifier includes a refrigerant loop including a compressor, at least one condenser, an expansion device and an evaporator including an evaporator fan. The condenser includes a water inlet and a water outlet for flowing water therethrough or proximate thereto, or is affixed to the tank or immersed into the tank to effect water heating without flowing water. The immersed condenser design includes a self-insulated capillary tube expansion device for simplicity and high efficiency. In a water heating mode air is drawn by the evaporator fan across the evaporator to produce cooled and dehumidified air and heat taken from the air is absorbed by the refrigerant at the evaporator and is pumped to the condenser, where water is heated. When the tank of water heater is full of hot water or a humidistat set point is reached, the water-heating dehumidifier can switch to run as a dehumidifier.
Oak Ridge National Laboratory 04/18/2006
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
UT-B ID 200201096DevelopmentAvailable10/20/201012/08/2010

Contact ORNL About This Technology

To: David L. Sims<>