Transcript Residential Heat Pump Water Heaters: HVAC Interaction Study RTF HPWH Subcommittee May 14, 2015

Residential Heat Pump Water Heaters:
HVAC Interaction Study
RTF HPWH Subcommittee
May 14, 2015
2
Today’s Agenda
• Brief recap and context for today’s meeting
• Present and discuss key questions
• Work towards subcommittee
recommendation on both
questions
3
Introduction
• November 2014, RTF directed staff to develop a research
plan to study the HVAC interaction effect induced by heat
pump water heaters (HPWHs)
• April 2015, RTF accepted a research strategy for studying
the HVAC interaction (or thermal coupling) parameter
• NEEA has agreed to sponsor and fund (or co-fund) this
research, but has asked the RTF subcommittee to weigh
in on some of the final technical details of the PNNL Lab
Homes study
4
Sensitivity of Total HPWH Savings to
HVAC Interaction Factor
Total Energy Savings (Hot Water + Heating), kWh
1,600
Tier 1, Interior
1,400
+/- ~20%
1,200
Interaction
Factor
1,000
50%
800
75%
600
100%
400
200
HZ1
HZ2
HZ3
Zonal Electric Resistance
HZ1
HZ2
HZ3
Electric Furnace
HZ1
HZ2
Heat Pump
HZ3
Research Strategy: PNNL Lab Homes
(from April 2015 RTF meeting)
• Research Goal
– Observe the space conditioning energy interaction that results from the
installation of a HPWH in interior spaces
• Data Collection
– PNNL Lab Home Study: Test four install locations throughout home
• Use 1kW space heaters and operate on a schedule similar to HPWHs
• 5-10 days per location
• Analysis
– Compute change in space heating requirement and HVAC interaction factor
for each location
– Observe range of results; depending on range, results may be combined
(averaged) if within a narrow band, or results could point to needing
additional measure identifiers
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Key Questions for Today
1. What equipment should be used to
induce the localized temperature
change in the experiment home?
2. What locations and conditions should
be tested in the experimental home?
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Question 1
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Equipment to Induce Temp Effect
What equipment should be used to induce the localized temperature
change in the experiment home?
Equipment Used to Test HVAC Interaction / Thermal Coupling Effect
Equipment Characteristic
Space Heater
Portable A/C Unit
HPWH
Uncertainty of Equipment Output/Performance
Low
High
High
Cost to Setup and Run Experiment
Low
Medium
High
Ability to Add Cooling Gain to Space (i.e. similar to that of a HPWH)
No
Somewhat
Yes
Yes*
Yes
Yes
Ability to Simulate the Magnitude of a HPWH's HVAC Interaction Effect
* If we can show experimental setup where heating gain produces symmetric HVAC interaction (i.e. as compared to cooling gain)
Definition: Thermal Utility
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•
Thermal Utility
– Tells you if “waste heat” is useful or not
– The ratio of useful internal heat gains to total gains that offset a heating requirement
– Example:
• Heating is required in a house for 6 months of the year
• Internal gains are 2,000 kWh/yr
 Useful gains are 1,000 kWh/yr. Thermal utility is 0.5.
Heating
Energy
Required
Energy from
Internal
Gains
Gains that just
make you hot
Useful gains
J
F
M
A
M
J
J
A
Useful
S
O
N
D
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Definition: Interaction Factor
• Interaction Factor = Thermal Coupling
• HPWHs are a negative internal gain
• HCƒ – heating and cooling interaction factor (0% - 100%)
– What fraction of the maximum possible interaction is “seen” by the
HVAC system?
– Primary hypothesis for the value being less than 100%:
• HPWH is located in a space that’s somewhat coupled to the outside
• HPWH extracts heat and sometimes that heat comes directly from outside
• How much of the heat removed by the HPWH is realized as an
internal gain/loss?
• Note: HCƒ differs from thermal utility which remains nearly
unchanged regardless of a HPWHs thermal coupling
House Heating Loads and Gains
QLoad
QLoad = UAΔT – QIntGains – Qsolar
QIntGains = QHeatGains + QHPWH
QHeatGains = QRefrig + QTV + QWii + QLights + …
UAΔT
Qsolar
QHeatGains
0
2
4
6
8
10
12
Hour of Day
14
16
18
20
22 24
Symmetry in Positive and Negative Gains
QLoad = UAΔT – QIntGains – Qsolar
QIntGains = QHeatGains + QHPWH
QHeatGains = QRefrig + QTV + QWii + QLights + …
QIntGain,i(+) = Decreased thermal
load on HVAC from increased
internal gains [kWh/day]
QIntGain,i(-) = Increased thermal load
on HVAC from decreased internal
gains [kWh/day]
QIntGain,+ = (-1) * QIntGain,-
QLoad
𝐐IntGain,i(+) = 𝐐IntGain,i(-)
UAΔT
Qsolar
+1kW
QHeatGains
-1kW
0
2
4
6
8
10
12
Hour of Day
14
16
18
20
22 24
Thermal Utility Complications in Measuring Thermal Coupling
If thermal utility is not constant:
• thermal coupling can’t be measured
• positive and negative gains are not
symmetric.
House floats off set point and the +1kW internal
QLoad
gains are no longer useful – their thermal utility
changed. Moreover, the change in areas between the
dashed March line and the red and blue lines is now
different – the gains don’t have a symmetric utility
January
Doh!
UAΔT
March
Qsolar
+1kW
QHeatGains
-1kW
0
2
4
6
8
10
12
Hour of Day
14
16
18
20
22 24
Complications: A More Nuanced View
?
≈
Tin
QLoad
• House floats off set point. Load changes. Heat loss increases over that
time period. Drywall stores heat. Sun goes away. Some, but not all heat
returned to house as it “coasts” back to set point.
TSet Point
March
UAΔT
Qsolar
+1kW
QHeatGains
-1kW
0
2
4
6
8
10
12
Hour of Day
14
16
18
20
22 24
Controlling for Thermal Utility Complications
Via Experimental Design
QIntGain,i(+) = Decreased thermal
load on HVAC from increased
internal gains [kWh/day]
QLoad
QLoad = UAΔT – QIntGains – Qsolar
QIntGains = QHeatGains + QHPWH
QHeatGains = QRefrig + QTV + QWii + QLights + …
QHPWH = QUAtank + Qcompressor (Qcompressor is negative)
QIntGain,i(-) = Increased thermal load
on HVAC from decreased internal
gains [kWh/day]
𝐐IntGain,i(+) = 𝐐IntGain,i(-)
Test when the load is high
UAΔT
Qsolar
+1kW
QHeatGains
-1kW
0
2
4
6
8
10
12
Hour of Day
14
16
18
20
22 24
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Equipment to Induce Temp Effect
What equipment should be used to induce the localized
temperature change in the experiment home?
CAT Proposal: space heater
• Least uncertainty in thermal output
• Easiest and cheapest to implement
• Produces symmetric HVAC effect if studied under the proper
conditions
• A generic load that can represent other
measures that interact with HVAC equipment
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Question 2
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Locations/Conditions of Test Cases
What locations and conditions should be tested in the experiment home?
• Example Locations: BDRM-2, Master bath closet, near thermostat
• Example Conditions: door open or closed (if applicable), central/zonal heat
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Locations/Conditions of Test Cases (cont’d)
• Each test case will be run for a period of 5-10 days
• A minimum outdoor air temperature during test period should be
required in order to ensure symmetry effect
• Test cases should represent a wide range of a space’s
“connectedness” to the thermostat
– E.g. space near thermostat should be highly connected
– Spaces far away and/or highly buffered from thermostat will likely be less connected
• Test cases should be generic and test the expected range of HVAC
interaction factors to the extent possible
– E.g. a test case in the living room near the thermostat does not suggest HPWHs being installed in
a living room, but rather attempts to place a “book end” on the factor of interest
– Not all cases can be directly tested, e.g. a heated basement
• CAT proposes a phased approach to the research
– First phase serves as proof of concept and may be sufficient on its own
– Additional phases could be added to study additional scenarios
– Additional reasons to phase research: peak season is only so long, other
competing projects for PNNL Lab Homes
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Test Case Proposal
A
B
C
D
Test Case Description
Water Heater Closet
Utility Closet
Living Room
Master Bath, Door Open
Master Bath, Door Closed
Test Location
(on Floorplan)
A
B
C
D
D
Door Open
or Closed?
N/A
N/A
N/A
Open
Closed
Purpose of / Reason to Include Test Case
May be most disconnected area from the thermostat
Most connected to the return duct
Probably the most connected area to the thermostat
Highly buffered/disconnected from the thermostat
Even more buffered from the thermostat
CAT recommends all test cases use the same HVAC system (central) for first phase of research.
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Test Case Proposal
• Thoughts from the subcommittee?
• Does the subcommittee support this
proposal?
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Subcommittee Recommendation
1. What equipment should be used to induce the
localized temperature change in the experiment
home?
Subcommittee recommendation:
2. What locations and conditions should be tested in
the experimental home?
Subcommittee recommendation: