Heat Recovery Clothes Dryer
Residential Clothes Dryers: Heat Recovery vs. Conventional: Condensing vs. Conventional
A clothes dryer that uses an air-to-air heat exchanger to recover about 40% of the heat exhausted from a commercial or residential clothes dryer to pre-heat incoming supply air.
Item ID: 198
Process Loads & Appliances--Commercial and Residential Appliances
Technical Advisory Group: 2009 HVAC TAG (#2)
Technical Advisory Group: 2014 Residential Building TAG (#10)
Average TAG Rating: 2.37 out of 5
TAG Ranking Date: 04/10/2014
TAG Rating Commentary:
I like the HP Dryer idea better. High particulate exhaust could be a customer satisfaction issue. I doubt there is really that much benefit to using the dryer heat for space heat in our service area (or the northwest in general). Might benefit retirement homes or hospitals or hotels more.
I think that condensing clothes dryers are already a proven technology in Europe. The description does not explain the tie-in to DHW - which seems a little strange.
Need more data
This measure represents a rather complicated device that is bound to require fans, ducting, condensate handling, defrost controls, effective filtration--all while fitting into already cramped utility rooms. It's difficult to get people to clean the lint screen inside the dryer, let alone maintain an HRV that handles the most particulate-laden airstream associated with a residence.
Supporting a technology-neutral dryer efficiency standard would be more meaningful.
The energy savings is primarily from not having to condition outside air to make up the air that the dryer sucks out of the building, and, to use the heat generated by the dryer to heat the home. This concept can be applied to commercial applications also such as hotels, hospitals, dorms, etc. The savings would be dependent on climate conditions at the site, with colder climates seeing the most benefit.
The dryer exhaust air would go through a heat exchanger before being exhausted outside. Outside air will go through the other side of the heat exchanger to pick up heat (and moisture, depending on the heat exchanger type chosen) from the dryer exhaust and supply that heated air to the home.
The heat exchanger has two fans which consume electricity, and the dryer exhaust is high in particulate which can clog heat exchangers. Clogged heat exchangers reduce the efficiency of the dryer so a secondary filtration system is needed. This additional filtration also reduces the efficiency of the dryer.
Case studies found are for climates at -40 degree F, at which one would see a 3.2 kWh saving per dryer load at that outside air temperature. According to NEEA, Northwest consumers own 6 million electric clothes dryers and purchase about a quarter of a million clothes dryers each year. The average dryer runs for about 307 hours/year while processing 311 loads. Annual average energy use is about 761 kWh/year, which can be reduced by 15% through purchase of a dryer with condensing heat recovery.
Baseline Description: Electric residential clothes dryer
Baseline Energy Use: 761 kWh per year per unit
The 2014 NEEA "Residential Building Stock Assessment: Metering Study" involved conducting whole house energy end use metering. The average clothes dryer electrical energy use in the Northwest region was found to be about 761 kWh/year( Ecotope, 04/28/2014 Pg 73).
Manufacturer's Energy Savings Claims:
Currently no data available.
Energy Use of Emerging Technology:
646.9 kWh per unit 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:
Interestingly, the Residential Building Stock assessment is silent about what percentage of living units has either clothes washers or dryers. For single-family homes and manufactured homes, it is reasonable to assume that all units have a dryer, but here we estimate that 90% of multifamily units have in-unit dryers (Baylon, 2012). This gives a total retrofit potential in the Northwest of approximately 5,108,000 units.
Electric Clothes Dryers
Regional Technical Potential:
| Type || Units || % Electric || % units w/Dryer || Total |
| Singe Family || 4,023,937 || 95% ||100.0% || 3,822,740 |
| Mf'd. Homes || 543,730 || 95% ||100.0% || 516,544 |
| Multifamily || 863,104 || 99% || 90.0% || 769,026 |
| Total || 5,430,771 || || || 5,108,000 |
0.58 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.