Texas A&M University - ARPA-E · 2015-06-03 · ASHRAE Standard 62.1-2013 • For commercial...
Transcript of Texas A&M University - ARPA-E · 2015-06-03 · ASHRAE Standard 62.1-2013 • For commercial...
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HVAC Energy Flow in Buildings
Charles H. Culp, P.E., Ph.D., FASHRAE, LEED-APProfessor, Department of Architecture Associate Director, Energy Systems Lab
Texas A&M University
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Goals• View a building’s energy flow • Differences between commercial and residential buildings• Building HVAC equipment• Comfort considerations• Health considerations• Limits of building efficiency • Advances in new buildings• Advances in improving existing buildings
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Conduction
ConvectionEvaporation
if wet
Radiation
Infiltration
Ground Conduction
Exfiltration and Exhaust
Solar
QClimateSensitive = QSolar + QWeather + QOutsideAir+ QGround
The Climate Sensitive load is the sum of:
AC
WeatherTemperatureRH…
Outside AirVentilation
Building Energy Flow
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Conduction
ConvectionEvaporation
if wet
Infiltration
Ground Conduction
Exfiltration and Exhaust
QInternal = QPeople + QLights + QPlug
The Internal load is the sum of:
Solar
AC
WeatherTemperatureRH…
Outside AirVentilation
Building Energy Flow
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Conduction
ConvectionEvaporation
if wet
Infiltration
Ground Conduction
Exfiltration and Exhaust
QTotal = QClimateSensitive + QInternal
The Total load is the sum of:
Solar
AC
WeatherTemperatureRH…
Outside AirVentilation
Building Energy Flow
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Conduction
ConvectionEvaporation
if wet
Infiltration
Ground Conduction
Exfiltration and Exhaust
QTotal = QClimateSensitive + QInternal
The Total load is the sum of:
Solar
WeatherTemperatureRH…
Outside AirVentilation
Building Energy Flow
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Conduction
ConvectionEvaporation
if wet
Radiation
Ground Conduction
Exhale / Inhale
Solar
The Climate Sensitive heat load is the sum of:
QClimateSensitive = QSolar + QWeather + QOutsideAir+ QGround
WeatherTemperatureRH…
Outside AirVentilation
Personal Energy Flow
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Conduction
ConvectionEvaporation
if wet
Radiation
Ground Conduction
Exhale / Inhale
Solar
The Internal heat load is the sum of:
QInternal = QSensible + QLatent
Sensible
Latent
WeatherTemperatureRH…
Personal Energy Flow
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Conduction
ConvectionEvaporation
if wet
Radiation
Ground Conduction
Exhale / Inhale
Solar
The Total heat load is the sum of:
Sensible
Latent
QTotal = QClimateSensitive + QInternal
Personal Energy Flow
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Heat Flow• HVAC changes heat flows
• Move heat to outside in summer
Outdoor Unitbasc.pnnl.gov
Heat Pump – Summer Cooling
Indoor Unit Suction Line
Liquid Line
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Heat Flow• HVAC changes heat flows
• Move cold to outside in winter
Outdoor Unitbasc.pnnl.gov
Heat Pump – Winter Heating
Indoor Unit Suction Line
Liquid Line
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• A Residential Systems Contains• Recycles indoor air (where does fresh air come from?)• Cooling
• Compressor• Evaporator• Condenser• Expansion device• Fan• Ducts and registers• Filter(s)
• Heating• Above + • Burner• Heat exchanger
HVAC - Residential
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Psychrometric Chart• Variables of Interest
• Temperature• Impacts comfort• Influences condensation
• Relative Humidity• Can calculate dew point from relative humidity/temperature• Want inside temperature higher than dew point of outside air
• Humidity Ratio• Ratio of lbs of H2O to lbs of dry air
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Temperature
40 50 60 70 80 90 100 110 ºF
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Relative Humidity
40%
20%
60%80%
100%
50%
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Humidity Ratio
0.009
0.006
0.003
0.018
0.015
0.012
0.027
0.024
0.021
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TemperatureHumidity RatioRelative Humidity
0.009
0.006
0.003
0.018
0.015
0.012
0.027
0.024
0.021
40
20
6080
100
50
40 50 60 70 80 90 100 110 ºF
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Health Indoors - Residential• Asthma
• Incidence1,2
• 2008 – 2.8%• 1996 – 0.6%• 1980 – 0.25%• Other refs indicate growth from 2% of the population to
10.6%.
• Costs2
• About $3,300 per person per year
1Asthma incidence: data from the Nat. Health Interview Survey, http://www.ncbi.nlm.nih.gov/pubmed/17365207
2American Academy of Allergy Asthma and Immunology, http://www.aaaai.org/about-the-aaaai/newsroom/asthma-statistics.aspx
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Health Indoors - Residential
SA (Supply Air)IA (Inside Air) CC
Filter
Attic ducts leak
Negative pressure
inside
Inside75°F50% RH
Summer95°F59% RH~78°F Dew Point
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Health Indoors - Residential
Summer95°F59% RH~78°F Dew Point
SA (Supply Air)IA (Inside Air) CC
Filter
Attic ducts leak
Negative pressure
inside
Inside75°F50% RH 95°F
85°F
78°F
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Health Indoors - Residential• Negative Pressure • Positive Pressure
Inside75°F
Inside75°F
Outside95°F
59% RH
Outside95°F
59% RH
Inside75°F50% RH
85°F
85°FInside75°F50% RH
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Bad
Inside75°F
Inside75°F50% RH
85°F
Outside95°F
50% RH
95°F
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Good
Inside75°F
Outside95°F
50% RH
85°FInside75°F50% RH
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Health Indoors - Residential
SA (Supply Air)IA (Inside Air) CC
Filter
Attic ducts leak
Adjustablepressure
inside
Inside75°F50% RH
Summer95°F59% RH~78°F Dew Point
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Health Indoors - Commercial• Generally positively pressurized• Maintenance is an issue
AHU – Air Handler Unit
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ASHRAE Standard 90.1-2013
• For commercial buildings• Specifies efficiency
requirements for:• Insulation• HVAC• Lighting• Power
• Title: Thermal Environmental Conditions for Human Occupancy
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ASHRAE Standard 62.1-2013
• For commercial buildings• Specifies minimum outside
air • Ventilation Rate Procedure
• People contamination• Building materials
contamination• OA is the Outside Air
required
• Title: Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
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ASHRAE Standard 62.1-2013
• For commercial buildings• Specifies minimum outside
air
• Title: Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
#
2 2
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ASHRAE Standard 55-2013• Title: Thermal Environmental Conditions for
Human Occupancy• Specifies commercial
building comfort requirements
• Provides an evaluation procedure for existing buildings
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Personal Comfort• Balance temperature / moisture
• Keep body core temperature at a comfortable level• Sedentary comfort
• Sensible: ~250 Btu/hr• Latent: ~200 Btu/hr
• Active comfort• Sensible: Ranges from 300 to 800+ Btu/hr• Latent: ~250 to 700+ Btu/hr
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Personal Comfort• From “Thermal Comfort under Transient
Metabolic and Dynamic Localized Airflow Conditions”• A. Ugursal, PhD Thesis
• Background• Occupant productivity
Seppanen et al. (2004)
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Personal Comfort• Three groups of body parts based on
contribution to overall thermal sensation1:• Highest: back, chest, pelvis• Moderately: face, neck, breathing, head, arms, legs• Least: hands, feet
• Measurements
1Zhang (2003)
1: Forehead 2: Cheek 3: Neck 4: Chest 5: Abdomen 6: Upper Back 7: Lower Back 8: Upper Arm
9: Lower Arm 10: Hand 11: Anterior Thigh 12: Anterio-medial
Thigh 13: Anterior Calf 14: Posterior Calf15: Instep
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Personal Comfort• Results
• People demand more air even when they feel cool• Pulsed air increased perception of thermal comfort• Draught rating of our test (5%) was significantly lower than the
Standard 55 prediction (16%)
Experimental Chamber
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Limits of Building Efficiency• Study done by Claridge and Tanskyi at the ESL • Assumptions
• Comply with ASHRAE energy efficiency, comfort and ventilation standards
• Calibrated building energy use to actual use
ESL Building – 25 kft2 Bullitt Cascadia Center – 52 kft2
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Limits of Building Efficiency• Use – kBtu/ft2-yr
• Normal Building: 82 kBtu/ft2-yr • ESL Building: 50 kBtu/ft2-yr • Bullitt Cascadia Center: 16 kBtu/ft2-yr (planned) • “Carnot Limit” Building: 0.73 kBtu/ft2-yr
ESL Building – 25 kft2 Bullitt Cascadia Center – 52 kft2
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Limits of Building Efficiency• Demand – kBtu/ft2-yr
• ESL Building: 138 kW summer178 kW winter
• “Carnot Limit” Building: 2.2 kW summer1.6 kW winter
ESL Building – 25 kft2
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Improving Residential• Today’s residential buildings
• Get outside air through envelope leakage • Stick built, poor sealing• Lack control
• Typically control on/off to temperature only
• Tomorrow’s residential buildings • Tighter and better insulated
• Sprayed foam is becoming more common• Still 2-times the cost of fiberglass
• Tightness REQUIRES outside air be provided
• Higher performance HVAC • Enthalpy recovery ventilators (ERVs, HRVs) available• New very-high efficiency AC in the lab today
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Improving Residential• Enthalpy recovery ventilators (ERVs, HRVs)
available• Existing commercial HRVs deliver 69% or so
effectiveness• HRV in lab delivers 90% effectiveness, ~85%
efficiency
Straight Airfoils Airfoils AvailableChannel Hgt. 0.25” 0.4” 0.5” -Effectiveness 91% ±5% 95% ±5% 81% ±5% 69% ±5%∆P (in-H2O) 0.16 ±0.01 0.11 ±0.01 0.09 ±.01 0.40 ±.01
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Improving Residential - Summer• Application of HRVs – 90% Effective
• At 90% effectiveness
• At 69% effectiveness
Fresh air to space
Stale air to outsideOutside air
Exhaust air
Stale Air Out Outside Air Fresh Air Exhaust AirWinter 72°F 42°F 69°F 45°FSummer 78°F 98°F 80°F 96°F
Stale Air Out Outside Air Fresh Air Exhaust AirWinter 72°F 42°F 63°F 51°FSummer 78°F 98°F 84°F 92°F
78°F
96°F
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Improving Residential - Winter• Application of HRVs – 90% Effective
• At 90% effectiveness
• At 69% effectiveness
Fresh air to space
Stale air to outsideOutside air
Exhaust air
Stale Air Out Outside Air Fresh Air Exhaust AirWinter 72°F 42°F 69°F 45°FSummer 78°F 98°F 80°F 96°F
Stale Air Out Outside Air Fresh Air Exhaust AirWinter 72°F 42°F 63°F 51°FSummer 78°F 98°F 84°F 92°F
72°F
45°F
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Improving Residential• Higher performance HVAC – ARPA-E, Navy
• New very-high efficiency AC in the lab today
• Benefits• Theoretical 60+ SEER with 40+ practical• No refrigerants• Generates clean H2O• Healthier • Also works with commercial buildings• Lab unit is working
Type System COP
First Cost3 Ton Unit
Comfort Operating Cost
Refrigerant ~ 3 to 5 $5K to $8K Med High
Desiccant ~ 4 to 5 $7K to $14K High Very High
Membrane-Evaporative
~ 5 to 18 Initial: $9K to $16KMature: $4K to 8K
High Low
Tech
nolo
gy
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Improving Commercial• Today’s commercial buildings
• Typically built to minimum standards• Energy use ranges 40 to 120 kBtu/ft2-yr• Poorly trained operators
• Tomorrow’s commercial buildings • Codes are increasingly stringent
• Will drive better materials, less “all-glass”
• Higher performance HVAC • Enthalpy recovery ventilators (ERVs, HRVs) will be required• Several HVAC improvements moving to marketplace
• Energy and enthalpy wheels, refrigerant compressors, variable flow refrigerant systems, etc.
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Improving Commercial• Major opportunity in new and existing
buildings – Controls and Tuning• Existing building commissioning can achieve
• 10% to 20% reduction in total energy use• Translates to a 20% to 40% reduction in HVAC energy use
• 2 to 3 year payback• Healthier building since the controls will work correctly
-$400,000
-$200,000
$0
$200,000
$400,000
$600,000
$800,000
$1,000,000
Nov
-08
Feb-
09
May
-09
Aug
-09
Nov
-09
Feb-
10
May
-10
Aug
-10
Nov
-10
Feb-
11
May
-11
Aug
-11
Nov
-11
Feb-
12Project Timeline
Net Cumulative Savings Cumulative Savings Cumulative Costs
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Summary• Residential buildings
• Need to bring in outside air• Commercial buildings
• Need to be operated well• Improve implementation of controls
• Understand • Temperature• Moisture• Pressurization