Desiccant Dehumidifiers for Grocery & Cold Storage
Cold Storage: Desiccant dehumidifier vs. Conventional
A solid desiccant dehumidifier integrated with the HVAC system that can maintain the humidity level inside a building in the range of 30% to 40%.
Item ID: 313
HVAC--Other HVAC Systems
Technical Advisory Group: 2010 HVAC TAG (#3)
The technology has been available for more than 10 years, but has not yet been widely adopted. A solid desiccant dehumidifier is integrated with the HVAC system to maintain the humidity level inside a building at approximately 30% to 40%. For grocery stores, this saves energy because reheaters are not needed on glass cooler doors and the frequency of defrost cycles is reduced. It may also reduce the energy needed for space cooling compared to conventional AC. For grocery and cold storage, desiccant dehumidifiers can reduce corrosive damage from frost buildup on chilling equipment.
The wet desiccant material is typically dried (“recharged”) using natural gas, although waste heat from chillers or solar heat are other options to recharge the desiccant. While electricity use and overall energy use are both reduced with this technology, it might be considered a type of fuel switching unless waste or solar heat is used to recharge the desiccant.
This technology is commonly applied to large industrial processes, although it is migrating to smaller commercial applications. This is most cost-effective in hot, humid climates, and is not yet proven for use in the marine or dry climates of the Pacific Northwest. It is probably most cost-effective for new construction, where the ductwork and other AC components can be downsized, versus renovation or retrofits, where the ducts have already been installed.
Baseline Description: Supermarket dehumidification with refrigerant
Baseline Energy Use: 12.3 kWh per year per square foot
The typical EUI for a supermarket, as found from ( ASHRAE, 2009-10-01) uses 179 kBTU/sf/yr (52.4 kWh/sf-year equivalent). For the "Grocery" sector in the Northwest, NEEA's 2009 Commercial Building Stock Assessment identifies an electrical EUI of 44.7 kWh/sf-year for electrically heated and cooled buildings (see Table D-EA5). Buildings with no electrical heating or cooling have an electrical EUI of 32.4 kWh/sf-year, implying that heating and cooling for grocery stores accounts for about 12.3 kWh/sf-year. Lighting and refrigeration accounts for much of the remainder of the electrical loads.
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 25%
Low and High Energy Savings: 20% to 30%
Energy Savings Reliability: 5 - Comprehensive Analysis
(Fricke, Sharma, 2011) The use of hybrid HVAC systems that incorporate desiccant dehumidification have been proposed for supermarket applications (GRI 1984) (Mitchell, et al. 1992) (Capozzoli, et al. 2006) (Lazzarin and Castellotti 2007).
Energy Use of Emerging Technology:
9.2 kWh per square foot per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
The Food Marketing Institute (in their Industry Overview 2013, Supermarket Facts sheet) indicates that there are 37,459 supermarkets in the U.S. with annual sales of $2 million or more. Prorating by population indicates that there may be 4% x 37,459 or 1,498 large supermarkets in the Northwest. The 2009 "Northwest Commercial Building Stock Assessment" lists "Grocery" stores as comprising 84.6 million sf of floor area (Table C-GB1). To obtain the desired savings, the dehumidifier might have to be installed in conjunction with other control or technologies such as Refrigeration System Controllers (ET #4) or Freezer Anti-Sweat Heater Controllers (ET #24).
Regional Technical Potential:
0.26 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Currently no data available.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.