Energy and the Built Environment

Atila Novoselac

Wesley Cole

Energy Technology & Policy

10/23/12

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

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)

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

Energy Consumption Monthly Profile for 100,000 sf Commercial Building in Austin

~12%

~96 MWh

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%

Same Building in Minneapolis, Minnesota

~150%

~845 MWh

NOTE: We would never build the same buildings in Austin and Minneapolis

An Average Commercial Building in US

HVAC ~ 35%

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)

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:

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 !

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 ?

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%

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

Appliances

Contribute significantly to energy consumption (especially in residential buildings)

Washer Comparison

470 kWh/yr ($50/yr)

Cost: $349

144 kWh/yr ($15/yr)

Cost: $403

Source: Home Depot (2012)

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?

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

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

Thermal Comfort

• Combination of

- Indoor environmental factors

- Personal factors

• Human body

- in thermal equilibrium with the environment

Thermal Comfort Equation

Metabolic Heat - Work = Energy that body release

Energy balance for human body

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

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.

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

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.)

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

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

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”

LEED Affects:

• Sustainable Sites

• Water Efficiency

• Energy & Atmosphere

• Materials & Resources

• Indoor Environmental Quality

• Locations & Linkages

• Awareness & Education

• Innovation in Design

• Regional Priority

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

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

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

Net-Zero Building (RSF)

http://www.nrel.gov/sustainable_nrel/rsf_int

eractive.html