energy and the built environmentche.utexas.edu/course/che359&384/lecture_notes/topic_10...energy...
TRANSCRIPT
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Energy and the Built Environment
Atila Novoselac
Wesley Cole
Energy Technology & Policy
10/23/12
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Lecture Objectives
• How much energy is consumed in buildings
• How the energy is consumed
• How to make them better
– energy efficiency
– thermal comfort
– indoor air quality
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Total Primary Energy Consumption in U.S. by Sectors
• Total primary energy: 97.3 x 1015 Btu (for 2011)
• Building energy costs $350 billion/year $0.031/kWh
Source: EIA (2008)
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Energy Principles: Site Energy vs. Primary Energy
Site (End-use) energy is the energy directly consumed by end users
Primary energy is site energy plus the energy consumed in the production and delivery of energy products
Site energy (End use)
Primary Energy
Primary Energy
HVAC System
HVAC – Heating, Ventilation and Air-Conditioning
Generation
Storage
Distribution
Site Energy
Light
Thermal
Fresh
air
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Energy Consumption Monthly Profile for 100,000 sf Commercial Building in Austin
~12%
~96 MWh
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Comparison of Energy for Heating and Cooling
How to compare heating energy from gas and electric energy for cooling ?
1) Convert all to primary energy
2) Convert end use energy from gas to electric energy you would get from this gas
You will need: - Conversion factors: 1000 BTU = 0.293 KWh, 1,000,000J=0.278 KWh
- Average efficiency of electric generation systems: ≈33%
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Same Building in Minneapolis, Minnesota
~150%
~845 MWh
NOTE: We would never build the same buildings in Austin and Minneapolis
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An Average Commercial Building in US
HVAC ~ 35%
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Analysis of Energy Consumption in Residential Buildings
• We are considering a model building used in Austin Energy analyses
Model house: - Location in Austin -2300sf -R13 walls -R30 attic -4 occupants -Surface absorptivity to Solar rad.: 0.7 -Typical (average) internal loads -Infiltration/Ventilation 0.5 ACH - Double glazed widows
- Glazing are 20% south, 25 north, 5% east and west - SHGC=0.54 (reflective – bronze - glass)
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Energy Consumption in Newer Residential House in Austin
2000
(15,600 kWh)
Including gas
CoolingMiscellaneous
Range
Dryer
Heating
Lighting
Hot water
Refrigerator
Washer
End use energy where
energy from gas is converted to equivalent electric energy
~45%
Year:
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Energy Consumption and Improvements in Code Requirements
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
2000 2006 2010 target (2015)
Miscellaneous
Washers
Range
Refrigerator
Lighting
Dryer
Hot water
Heating
Cooling
15620 kWh
12862 kWh
11304 kWh
7086 kWh
Desired
Value !
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Energy Consumption: kWh/year (to get approximate cost multiply by ~0.1)
Units are in kW/h per year Example question: A window company is offering you a better windows (SHGC=0.27) and that cost $10,000.
Is it worth while ?
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What Drives Energy Consumption?
• Consider 2300 ft2 home in Austin • 30% cooling, 14% heating, 12% hot water, and
44% lighting, appliances, and other devices
Cooling Energy Total Energy Year-Round Energy
Internal Loads 36% 11% 2.3%
Radiation (windows) 23% 7% 19%
Radiation (ext. surfaces)
11% 3.5% Combined Radiation
Infiltration 7% 2.2% 5.5%
Conduction 23% 7% 17%
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Lighting in Buildings Type of lamps
• Incandescent
• Fluorescent and HID
• LED
• …. Type Relative comparison power consumption
for the same light output
Lifetime
Incandescent 40 W 2 – 8 months
Fluorescent and HID 10 – 25 W 1 – 2 years
LED 3-10 W (or not ?) 10+ years
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Appliances
Contribute significantly to energy consumption (especially in residential buildings)
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Washer Comparison
470 kWh/yr ($50/yr)
Cost: $349
144 kWh/yr ($15/yr)
Cost: $403
Source: Home Depot (2012)
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Building Envelope
HVAC
Major question:
How much ventilation, how much heating, and how much cooling we need to have
to provide satisfactory air quality and thermal comfort in the building?
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Building HVAC Systems (Primary and Secondary Building Systems)
AHU
Building
envelope
Cooling
(chiller)
(or Gas)
Electricity
Gas
Heating
(boilers)
Fresh air
For ventilation
Distribution
systems
Air transport
Secondary
systems
Primary
systems
AHU – Air Handling Unit
HVAC systems affect the energy efficiency of
the building as much as the building envelope
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How to make a zero energy house?
Turn off electric power and gas
Environmental parameters need to be defined by
- thermal comfort and
- indoor air quality
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Thermal Comfort
• Combination of
- Indoor environmental factors
- Personal factors
• Human body
- in thermal equilibrium with the environment
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Thermal Comfort Equation
Metabolic Heat - Work = Energy that body release
Energy balance for human body
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Thermal comfort
• Metabolism – health condition and activity
• Clothing level
• Air Temperature
• Mean Radiant Temperature
• Air Velocity
• Humidity
PPD – Predicted Percentage of Dissatisfied Scale 5-100%
P.O. Fanger
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Thermal Comfort Factors that we Control in Buildings
–Air Temperature
–Humidity
–Air velocity
– Surrounding Temperature
Air temperature, relative humidity and velocity are defined by
ASHRAE standard 55: Thermal Environmental Conditions for Human Occupancy.
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Indoor Air Quality (IAQ) Americans are Indoor Creatures
• Indoors 89%
• 2/3 of time in home
• Transit 6%
• Outdoors 5%
• 18 hours indoors for every 1 outdoors
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USEPA Risk Rankings
1. (tie) Worker exposure to chemicals
1. (tie) Indoor radon
3. Pesticide residue on foods
4. (tie) Indoor air pollutants (non-radon)
4. (tie) Consumer exposure to chemicals
(includes cleaning fluids, etc.)
6. Hazardous/toxic air pollutants
7. Depletion of stratospheric ozone
8. Hazardous waste sites (inactive)
9. Drinking water (radon and THMs)
10. Application of pesticides
16 others .. (including groundwater contamination at 21, criteria air pollutants at 22, etc.)
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Exposure in Buildings
• Chemicals
• Wall-to-wall carpet
• Cleaners
• Air fresheners
• Pesticides
• Personal care products
• Building materials
• Moisture related pollutants
• Outdoor pollutants (O3, PM 2.5,…)
• ….
Challenges:
Very difficult to detect/measure them
Even more difficult to quantify consequences
Global Production: Synthetic Organic Chemicals
0
50
100
150
200
250
300
350
1920 1940 1960 1980 2000
Year
Bil
lion k
g/y
ear
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Exposure Reduction • Prevention
– Remove sources • Use low emission materials
• Keep your house dry
• Many trivial measures such as: take off your shoes in homes
• ….
• Dilution
– Ventilation • Ventilation rate is defined by ASHRAE Standard 62: Ventilation for
Acceptable Indoor Air. Quality
• Don’t seal your homes!
• Filtration
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LEED - Leadership in Energy and Environmental Design
Effort to integrate sustainability into building industry
“It promotes sustainable building and development practices through a suite of rating systems that recognize projects that implement strategies for better environmental and health performance”
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LEED Affects:
• Sustainable Sites
• Water Efficiency
• Energy & Atmosphere
• Materials & Resources
• Indoor Environmental Quality
• Locations & Linkages
• Awareness & Education
• Innovation in Design
• Regional Priority
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LEED Certification is a Rating System that Evaluates:
• Sustainable Site
• Water Efficiency
• Energy & Atmosphere
• Materials & Resources
• Indoor Environmental Quality
• Locations & Linkages
• Awareness & Education
• Innovation in Design
• Regional Priority
USGBC established four levels of LEED
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Note that • Energy and Indoor Environmental Quality (IEQ) count
for 50 points out of 110. ( Silver Certification)
• However, how do we consider different quantities?
– ______ increases energy use but improves indoor air quality
• Ventilation , Air cleaning
– ______ reduces exposure to some compounds and increases exposure to other compounds • Low-VOC paint, Ventilation
– ______ improves exterior environment and degrades indoor environment • Fly-ash concrete, Green roofs
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LEED is far from perfect!
• It has many positive sides, but negative too
• Current problem with LEED: – An average LEED building is
more efficient, but 28–35%
of LEED buildings use more
energy than their conventional
counterparts
• LEED is still developing
Every version gets better
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Net-Zero Building (RSF)
http://www.nrel.gov/sustainable_nrel/rsf_int
eractive.html