Residential Water Heating Dehumidifier (WHD) With Devoted Dehumidification

Abstract

A new a dual-service dehumidifier water heater (WHD) appliance is being researched and developed by the authors. Prior research on a similar appliance, a heat pump water heater (HPWH), has demonstrated the unit’s increased performance and energy saving, and through collaboration, significant progress has been made toward developing the WHD into a potentially marketable product. The primary energy use in residential households is space conditioning (49%), and the second major energy use is hot water consumption. In DOE’s 2004 Buildings Data Book, 15.5 percent of residential energy utilization is consumed by water heating (DOE 2004, Table 1.2.3). The two major types of residential water heaters are direct gas fired (~55%) and electric resistance (~45%) (DOE 2004, Appliance Magazine 2005). The maximum efficiency of a standard electric resistance water heater is 1 (100%), and progress has been made to increase the efficiency of the current standard heaters to approximately 95 percent (DOE 2004, Table 5.10.6), which is roughly the maximum available with today’s technology. However, if the standard system is replaced by a Heat Pump Water Heater (HPWH), the performance can be increased by 140 percent (Zogg and Murphy 2004). The WHD operates as a HPWH while heating water and as a dedicated dehumidifier when water heating is not necessary. This paper presents the general design and laboratory testing results of a WHD. Preliminary performance data reveal coefficient of performances (COP) of approximately 2.2 during water heating. Further, market analysis has revealed that a potential need for this new technology is in regions with high humidity (Ashdown et al. 2004). These regions are primarily in the Northeast, Southeast and some coastal areas of the U.S. Current HPWH units do not have dedicated dehumidification and have a very small share of the residential water heat market. Of the 9.55 million residential water heaters sold in 2003 only about 2,000 of them were HPWHs (DOE 2004, Table 5.10.15).