A Combined Water Heater, Dehumidifier, and Cooler (WHDC)

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Lead Performer: University of Florida, Gainesville, Florida
-- Oak Ridge National Laboratory - Oak Ridge, TN
-- Stony Brook University - Stony Brook, NY
DOE Funding: $1,000,000
Cost Share: $111,111
Project Term: October 1, 2014 to September 30, 2016
Funding Opportunity: Building Energy Efficiency Frontiers and Incubator Technologies (BENEFIT) ‐ 2014 (FOA DE‐FOA‐0001027)

Project Objective

The project goal is to develop a technology for compact, low-cost combined water heating, dehumidification, and space cooling (WHDC). The proposed system dehumidifies the air and uses its energy for water heating. The condensed water can subsequently be given back to the dried air in an evaporative cooling process; or, when only dehumidification is desired, it can be simply drained from the system. This technology can utilize the A/C latent load for domestic hot water heating, resulting in significant energy savings for water heating and A/C. The system can control humidity in residential buildings, resulting in comfort and significant health benefits.

At the core of the system is an extremely compact open absorption cycle in which the water vapor releases its latent heat into the absorber. The released heat is subsequently transferred into the process water that cools the absorbent. The solution is regenerated in the desorber where it is heated by a heating fluid. The water vapor generated in the desorber is condensed and its heat of phase change is also transferred to the process water. The technology is enabled by the advance absorption and desorption surface structures developed at the University of Florida. The proposed technology also benefits from a newly developed noncorrosive and nontoxic ionic liquid (IL) that does not crystallize. These properties are critical to development of a robust cycle and its widespread adoption.

A demonstration unit will be fabricated and its performance will be evaluated for all suitable climates in an environmental testing chamber at Oak Ridge National Lab.

Project Impact

The technology being developed is applicable to three of the five climatic zones in the continental U.S.: the mixed-humid, hot-humid, and marine zones which encompass 54% of the U.S. homes. Under typical operating conditions, the system model predicts to deliver 1.63 units of heat to hot water for each unit of heat supply, while reducing the A/C load by 0.63 units. Considering all forms of losses and back up burner scenarios (if humidity is not available), the primary energy factor (EF) of the proposed system is expected to be around 1.14.

Using the 2030 market size, the technical primary energy savings potential based on residential water heating benefit alone in the target zones is 346 TBtu/yr. Assuming half square footage of commercial gas water heating market in the target zones, 134 TBtu/yr primary energy saving potential is expected.

Additional savings arise from the latent heat load reduction on the cooling system through dehumidification. Using a target SEER of 14.6 at 2030 and a primary energy factor of 3.1, we arrive at a primary energy saving of 135 TBtu/yr due to removal of air-conditioning latent load.

Another application of the cycle is basement dehumidification (19% of the U.S. households have at least one basement dehumidifier). This gives a potential market of 10.4 million homes in the three climatic zones of interest.


DOE Technology Manager: Tony Bouza
Lead Performer: Prof Saeed Moghaddam, University of Florida

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