Heat pump clothes dryers
Published: February 6, 2014
- BENEFITS & BARRIERS
- CASE STUDIES
European clothes dryers an efficient alternative
While heat pump clothes dryers (HPCD) are not yet available in the U.S., they are a proven technology for energy efficiency in Europe and are set to be commercially available in the U.S. sometime in 2014.
Heat pump clothes dryers can be 40-50% more efficient than conventional electric resistance clothes dryers. Instead of using heated air and agitation to remove moisture from clothes as do conventional clothes dryers, the HPCD employs a technology that works like a reverse air conditioner. It is a mechanical system that uses a refrigeration loop with a refrigerant vapor compressor, an evaporator, a condenser and an expansion device.
To dry clothes in a HPCD, hot dry air is pulled into the drum with the wet clothes. The hot dry air pulls the moisture out of the clothes. This moist air then moves out of the drum and through an evaporator which removes a large amount of moisture from the air. Finally, the air moves through a condenser, extracting more moisture, and the drier air is returned to the drum. A small amount of heat needs to be rejected and that can be done either through vents or through a condensing technology that does not need vents.
HPCDs are expected to come on the market in the near future, but comparisons to the products currently sold in Europe suggest that the upfront cost may be a barrier to large-scale market penetration.
Typical clothes dryer drum
This clothes dryer looks like any other clothes dryer. The technology that's different is primarily in the back end of the system, so the user won't notice too much of a difference. While the clothes may take a little longer to dry, that may be the only difference in a heat pump versus a conventional system.
Heat pump technology
The heat pump moves the moist air out of the dryer drum through an evaporator. This air is then moved through a condenser which extracts further moisture from the clothes. The air is circulated through this cycle until the clothes are dry.
Potential energy savings
50% electricity savings compared to electric dryers
Heat pump clothes dryers (HPCD) are most appropriate in residential applications, although there may be limited use in commercial buildings. At this time, the HPCD on the market in Europe and those coming to the US are sized for residential applications.
Lower operating costs: studies have shown up to 50% electricity savings when replacing an electric clothes dryer with a HPCD, which translates into lower operating costs. Actual annual savings will depend on usage patterns of individual households.
Challenges and market barriers
Not available in US: heat pump technology is available in Europe and there is much momentum to bring the technology to the United States. Recent market estimates suggest we can expect to see heat pump clothes dryers enter the market in 2014.
Greatest savings when replacing electric clothes dryers: while HPCDs do have some savings potential when used to replace natural gas clothes dryers, the absolute energy savings are greatest when replacing an electric dryer with a heat pump dryer. Studies have shown that HPCDs can save up to 50% when changing from an electric resistance dryer to a HPCD.
Statewide energy savings
We took a high-level look at the potential energy savings in Wisconsin from heat pump clothes dryers. The estimate is meant to provide a sense of scale showing the impact this technology might have on Wisconsin energy customers. Since heat pump clothes dryers are not officially available in the US, current saturation of this technology is zero.
This technology will likely penetrate the market primarily as a replace-on-burnout technology. However, for purposes of estimating statewide impacts, we assume that all homes that currently have electric dryers replace them with heat pump dryers. We applied a technical savings rate of 50% to the residential electric load attributed to electric dryers. Using data from the Residential Energy Consumption Survey, we assumed 80% of homes have electric clothes dryers that could be replaced.
All data used for these estimates are from the Wisconsin Energy Statistics (2012) and Department of Energy's Residential Energy Consumption Survey data (2010).
There are not currently financial incentives available through the Wisconsin Focus on Energy program for heat pump clothes dryers.
As of June 2014, Heat Pump Clothes Dryers (HPCDs) were not available in the US and there were no case studies of their use in the US. The following research and applied studies examine the potential of HPCDs to save energy.
Analysis of Potential Energy Savings from Heat Pump Clothes Dryers in North America
This 2013 research study used standardized test procedures to measure and compare efficiency performance of four European dryer models and three North American models. Researchers subjected each dryer to the same performance tests (the study also proposed a revised testing standard that was ultimately adopted by the DOE). Compared to conventional models, the heat pump dryers:
- used 40-50% less energy
- took twice as long to dry the same amount of laundry
- had 5 times less peak power consumption
The report concludes that heat pump clothes dryers are a mature technology and have significant energy saving potential.
Results from CLASP study
Do Heat Pump Clothes Dryers Make Sense for the U.S. Market?
This 2010 study assessed life-cycle costs of HPCDs in American homes. Researchers developed a national impact analysis for different market share scenarios, using a an energy use calculation methodology that incorporated recent data on clothes washer cycles, clothes dryer usage frequency, remaining moisture content, and load weigh per cycle.
The study concludes that HPCDs have "positive economic benefits only for households with high clothes dryer usage or for households with high electricity prices and moderately high utilization." The significant incremental cost difference between conventional dryers and heat pump dryers may not be recouped during normal dryer use and are only cost-effective for a small share of US households.
Clothes Dryer Heat Pump Technology Offers Substantial Cost and Energy Savings for North America
summary This report presents result of tests of four European heat pump clothes dryers and three conventional North American clothes dryers.
citation Clothes Dryer Heat Pump Technology Offers Substantial Cost and Energy Savings for North America, Super Efficient Dryer Initiative, Clasp and Ecova, 2013.
Do Heat Pump Clothes Dryers Make Sense for the U.S. Market?
summary This paper presented at the 2010 ACEEE Summer Study on Energy Efficiency in Buildings presents the results of a life-cycle cost analysis of the adoption of HPCDs in a representative sample of American homes.
citation "Do Heat Pump Clothes Dryers Make Sense for the U.S. Market?," Meyers, et. al., Lawrence Berkeley National Laboratory. 2010 ACEEE Summer Study on Energy Efficiency in Buildings.
ENERGY STAR Emerging Technology Award: Technology Award: Heat Pump Clothes Dryers
summary Presentation to the 2011 ENERGY STAR Partner Meeting on the emerging technology award for HPCDs.
citation "ENERGY STAR Emerging Technology Award: Technology Award: Heat Pump Clothes Dryers," ENERGY STAR Partner Meeting, Charlotte, NC, 2011.
LG's new dryer saves energy and mone
summary Consumer Reports assessment of the LG heat pump dryer.
citation "LG's new dryer saves energy and mone," Consumer Reports, January 14, 2014.
LG Innovation Takes Laundry on a Revolutionary Spin
summary Description of the LG heat pump dryer posted by the LG Home Appliance Team.
citation "LG Innovation Takes Laundry on a Revolutionary Spin." LG News, January 7, 2014.
LG Dryers Feature Heat Pumps, NFC, and Trick Doors at CES
summary Reviewed.com previews the LG heat pump dryer.
citation "LG is the first manufacturer to bring some cutting-edge dryer tech to the US," Reviewed.com, January 4, 2014.