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Taking the hot air out of drying
Gregory P. Thiel, Ph.D.
ARPA-E Fellow
The clothes dryer
2
66TWhe/yr
30Mt CO2/yr
5-10%avg. house
elec. bill$
Data adapted from EIA (2018, 2015) and Energy Star (2011). Natural gas use
reported in exergetic equivalents.
CO2
0
1
2
3
Standard Electric Heat Pump Ultrasonic
But we’ve made some progress
3
kilo
watt
-ho
urs
per
cycle
In Widespread Use Best Available Technology In R&D
Image sources
Heat pump: https://storage.beko.co.uk/bekoupload/Beko2015/heat-pump-condenser.gif
Ultrasonic: https://www.ornl.gov/sites/default/files/Ultrasonic_Drying.jpg
So how low can we go?
4Image source: https://www.sophie-world.com/sites/default/files/styles/main_hero_responsive/public/22031556.png
5
Image adapted from: https://commons.wikimedia.org/wiki/File:Hygrometer-thermometer_hg.jpg, CC BY 3.0
Vapor Pressure of Water in Air
Saturation Vapor Pressure of Water in AirRH = ≤ 100%
Drying clothes is thermodynamically free
7
-10
0
10
20
30
40
50
60
70
CurrentEnergy Use
TheoreticalMinimum
Energ
y C
onsum
ption (
TW
h/y
r)
Figure Adapted from: https://nationalmap.gov/small_scale/printable/images/pdf/climate/humidity_3.pdf
removal of water and
organic compounds
1.2quads/yr
On the industrial
scale, the opportunity
for savings is even
bigger.
Ref: DOE Quadrennial Technology Review, 2016.
Image adapted from: https://commons.wikimedia.org/wiki/File:Rotary_Dryer_-_Allgaier.jpg, CC BY-SA 3.0
Here, too, we’ve seen progress
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• Process changes
• Low- or zero-carbon energy
• Enhanced heating technologies
• Ultrasonics
• Electrically-driven methods
References: https://www.wardsauto.com/industry/ford-expand-use-3-wet-paint-technology-2-wet-process-debut-cvs
https://www.chemicalprocessing.com/articles/2018/drying-research-heats-up/
… but it’s not enough
10
0
500
1000
1500
2000
2500
GH
G E
mis
sio
ns
(mill
ion
me
tric
to
ns C
O2e
/yr)
Total Industrial Sector
Emissions
Direct
Emissions
Emissions from
Electricity Use
Data source: EPA Inventory of Greenhouse Gas Sources and Sinks, 1990-2017
vaporization is one tool in a
toolbox for drying by moving water
Build out the non-evaporative drying portfolio
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• Process changes
• Low- or zero-carbon energy
• Enhanced heating technologies
• Ultrasonics
• … ?
Please send me your thoughts, ideas, and white papers:
My ask
‣ If you’re interested in…
– Saving our homes and industries money
– Advancing our drying technology toolbox
– Making dryers low energy and low carbon
– Rethinking thermal energy use in our industries
13
