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Air Source Heat Pumps in Minnesota Low Cost Hybrid Heating in a Cold Climate
Jeff Haase
CERTS Conference | St. Cloud, MN
February 21, 2013
Agenda
• Overview of Air Source Heat Pump Technologies – History, General
• Comparison of Operating Costs to Other Space Heating Technologies – Electricity, Natural Gas and Delivered Fuels
• Cold Climate Performance – Do ASHP Technologies work in Minnesota?
• Electric system compatibility of ASHPs • Future Technology Developments
– Will the performance of ASHPs improve over time?
2
Great River Energy
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• Not for profit generation & transmission cooperative providing wholesale electricity to 28 distribution cooperatives in Minnesota and into Wisconsin.
• Second largest utility in Minnesota, our member cooperatives distribute electricity to families, farms and businesses servings almost 1.7 million people.
Successful Portfolio of EE Programs
• Residential & Commercial Lighting • Energy Efficient Appliances • Commercial & Industrial Efficiency Programs • Quality Installed Air Conditioning Systems • Quality Installed Air Source Heat Pump Systems • Ground Source Heat Pumps • Agricultural Programs • Heat Pump Water Heating • Electric Thermal Storage Water & Space Heating • Load Management Programs
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Heat Pumps Generate Significant Energy Savings
Program Energy Savings (kWh)
Percent of Total
Energy Savings
Residential Lighting
29,638,551 19.8%
Comm. Lighting
20,134,718 13.4%
GSHPs 17,724,829 11.8% Appliances 15,284,509 10.2% ASHPs 5,978,073 4.0% Air Conditioning
1,630,582 1.1%
Load Management
804,584 0.5%
Total 91,195,846 60.8%
• Heat Pump Technologies
account for nearly 15% of our annual energy savings achievements.
• These savings are largely based on energy savings over electric resistance heating.
5
How many of you have an air source heat pump?
• Air conditioners • Refrigerators • Freezers • Dehumidifiers
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How does an ASHP “Pump” Heat?
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32°F 68°F
Heat Pumps are Analogous to Pumps
• Pumps move fluids from one place to another, they do not create the fluid.
• Pumps are incredibly efficient at doing this, but we refer to their ability to do work in terms of capacity and efficiency.
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There is Heat in “Cold” Air
• At 0ºF one pound of dry air contains approximately 110 BTUs.
• At 100ºF one pound of dry air contains approximately 134 BTUs.
• At -460ºF one pound of dry air contains 0 BTUs
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100 ºF 134 BTU/lb
0 ºF 110 BTU/lb
Heat & Heat Pumps
• Heat flows naturally from higher to lower temperatures.
• A heat pump does not generate heating or cooling energy.
• Heat pumps move heat from lower to higher temperatures, using a small amount of high quality drive energy.
• This is enabled by the vapor compression cycle.
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Vapor Compression Cycle
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Low Pressure, Low-Temperature
Vapor
Low Pressure, Low-Temperature
Liquid
High Pressure, High-Temperature
Vapor
High Pressure, High-Temperature
Liquid
Compressor
Evaporator Condenser
Expansion Valve
Heat out to the home, BTU/hr
As long as the ΔT between the refrigerant and the exterior is positive, heat will flow from the ambient into the refrigerant liquid.
Bin Temperature Data
Duluth, MN Rochester, MN
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Bin Total Hours95|100 4.390|95 21.385|90 90.880|85 223.875|80 386.470|75 547.965|70 663.160|65 750.455|60 649.650|55 572.845|50 532.440|45 495.635|40 604.130|35 822.925|30 589.820|25 458.415|20 360.110|15 251.85|10 212.30|5 181.1-5|0 133.9
-10|-5 104.3-15|-10 54.5-20|-15 29.4-25|-20 15-30|-25 4.5-35|-30 0.2
81% of all heating hours occur when ambient conditions are above 15°F
Bin Total Hours90|95 6.785|90 28.680|85 86.675|80 237.770|75 317.365|70 494.460|65 71755|60 66050|55 709.445|50 612.540|45 531.335|40 628.330|35 783.125|30 635.520|25 568.315|20 411.610|15 351.35|10 279.60|5 216.1-5|0 172.3
-10|-5 136.5-15|-10 84.6-20|-15 55.5-25|-20 25.2-30|-25 9.6-35|-30 1.8-40|-35 0.1
79% of all heating hours occur when ambient conditions are above 15°F
0
20
40
60
80
100
120
140
160
180
200
104
101 98 95 92 89 86 83 80 77 74 71 68 65 62 59 56 53 50 47 44 41 38 35 32 29 26 23 20 17 14 11 8 5 2 -1 -4 -7 -10
-13
-16
-19
-22
-25
-28
-31
-34
-37
-40
International Falls, MN
Bemidji, MN
Minneapolis - St. Paul, MN
Duluth, MN
Rochester, MN
COP | 1.0
System Performance will Decrease with the Outdoor Temperature
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Price Variability of Delivered Fuels
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$5.00
$10.00
$15.00
$20.00
$25.00
$30.00
Oct 01, 1990 Oct 01, 1995 Oct 01, 2000 Oct 01, 2005 Oct 01, 2010
Minnesota Fuel Oil & Propane Residential Price ($/Million BTUs)
Weekly Minnesota No. 2 Heating Oil Residential Price (Dollars per MMBTU) Weekly Minnesota Propane Residential Price (Dollars per MMBTU)
Price Variability of Natural Gas
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$0.00
$2.00
$4.00
$6.00
$8.00
$10.00
$12.00
$14.00
$16.00
$18.00
$20.00
Jan-1990 Jan-1995 Jan-2000 Jan-2005 Jan-2010
Minnesota Price of Natural Gas Delivered to Residential Consumers ($/Million BTUs)
Price Variability of Electricity
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4.00
5.00
6.00
7.00
8.00
9.00
10.00
11.00
12.00
1990 1995 2000 2005 2010
Residential Price (Cents per kilowatthour)
Fuel Price Comparison
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$5.00
$10.00
$15.00
$20.00
$25.00
$30.00
$35.00
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Fuel Price Comparison ($/MMBTU)
Average Residential Propane Price Average Residential No. 2 Heating Oil Price
Average Residential Natural Gas Price Average Electricity Price @ COP of 1.0
Average Electricity Price @ COP of 2.0 Average Electricity Price @ COP of 3.0
Dual Fuel Electric Rates
• Dual Fuel Rates are Offered by many utilities.
• Example | Mille Lacs Electric Cooperative – Dual Fuel rate of 5.5¢ per kWh (3412 BTU/kWh) – Comparable to:
• $1.48 per gallon of propane (91,500 BTU/Gallon) • $1.61 per therm of natural gas (100,000 BTU/therm) • $2.24 per gallon of fuel oil (138,700 BTU/Gallon) • These prices reflect 100% efficiency
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Comparing Fuel Options using an “Assumed” Home
• 3,000 Square Foot • 3 ton heat load | -30°F • Generalized heat loss
R 8.3 | U 0.12 • Temperature Bin Data
Duluth, MN • Setpoint | 70°F
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Heating Cost Profile
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$-
$50.00
$100.00
$150.00
$200.00
$250.00
$300.00
50 45 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30
Duluth, MN Temperature Bins 70°F Set Point Temperature
ASHP | Dual Fuel Rate ($0.055/kWh) ASHP | General Service Rate ($0.10/kWh)
90% Efficient Natural Gas ($0.8/Therm) 90% Efficient Propane ($1.98/gallon)
90% Efficient Fuel Oil ($3.05/gallon)
COP | 3.0 COP | 2.0 COP | 1.0
Annual Heating Costs
• ASHP
– Dual Fuel Rate ($0.055/kWh) - $950 – General Service Rate ($0.10/kWh) - $1,725
• 90% Efficient Natural Gas ($0.80/therm) | $821 • 90% Efficient Propane ($2.07/gallon) | $2,225 • 90% Efficient Fuel Oil ($3.58/gallon) | $2,255
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System Compatibility of ASHPs Wind output compared to load
55
75
95
115
135
155
175
400
600
800
1,000
1,200
1,400
1,600
1,800
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Avg.
Mon
thly
Win
d O
utpu
t (M
W)
GR
E Sy
stem
Low
Sid
e Av
g. M
onth
ly L
oad
(MW
)
Average GRE LoadLowSide (MW) Average Wind Load
Monthly Load Profile
Monthly Wind Profile
ASHP COP Improves Total System Efficiency
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Other ASHP Applications
• Ductless Mini-Splits – High SEER Values, retrofit applications
• Variable Refrigerant Flow Systems – Emerging in the US, efficient heating in
cold climates, ambient conditions, very efficient commercial retrofit application
• ASHP tied to supplemental ETS Heating – Minnesota Division of Energy Resources
http://mn.gov/commerce/energy/images/CIP-AirSource-Pump-Report.pdf
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The Future is Bright for ASHPs
• Technologies will continue to develop that improve the cold climate performance of ASHPs – Multi-stage compression, variable refrigerant flows,
new refrigerants (CO2) will all improve the overall performance and efficiency of ASHPs.
• ASHPs are complementary to our changing energy systems that include more renewables
• Improvements in Heat Pump Water Heater technologies are naturally transferable to ASHPs
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