Resources

November 11th, 2011 by scottgpeer


Definitions:

BTU: energy needed to raise 1 pound of water by 1 degree F (144 BTU to melt 1 pound of ice)

CFM: Cubic Feet per Minute, air flow for heating or cooling

EER: Energy Efficiency Ratio for air conditioner: BTU/hour per input watt

Footcandle (FC): the illumination from a standard candle at a distance of one foot

HVAC: Heating, Ventilating, and Air Conditioning

Lumen (luminous flux): the light from a standard candle at a distance of one foot over 1 square foot area

Lux (illumination): one lumen per square meter

MERV: Minimum Efficiency Reporting Value for filters (related to percentage of particulates captured)

SEER: Seasonal EER: BTU/Watt hour, averaged over cooling season (different conditions than EER)

Therm: unit of energy, equal to 100,000 BTU (heat produced by burning about 100 cubic feet of natural gas)

1 ton AC: 12,000 BTU/hour

 

Rules of Thumb (for Southern California unless otherwise noted) (can be used to catch simulation errors):

Buck A Watt: a 1 watt device costs $1 to power continuously for a year, given a utility rate of 11.4 cents per kilowatt hour (very cheap, most of California is 15 cents)

 

Typical AC uses 400 CFM/ton air flow

Fresh outside air: use 5 to 20 CFM per person; 10 to 20% of total HVAC air flow

Minimum AC SEER is 13

Energy expense savings for 1 SEER unit increase: 7%

EER = SEER * 0.9

SEER values for existing systems range from 13 (inefficient) to 26 (high efficiency)

Energy savings for each degree F increase in AC cooling setting: 2%

Energy savings for each degree F decrease in heater setting: 3%

Sources of heat gain: sun radiation through windows can be huge source (in Las Vegas, home orientation alone can change AC size by over a ton, e.g. putting windows on south side versus north side)

Windows account for 40% of heat loss/gain in a typical house

1 kW lighting or equipment = 3413 BTU/hour

1 person = 250 BTU/hour

1 HP motor = 2545 BTU/hour

office equipment = 0.85 to 8.5 BTU/hour per square foot

 

AC system sizing:

Building type: Square Feet/ton:

Conference rooms, arenas 150-200

Classrooms 200

Industrial 300

Office/retail 350-450

Residential (typical) 600-800

Residential (high efficiency) up to 1600

 

Insulation:

R-8 Best double pane windows, best duct insulation

R-11 3.5 inch fiberglass insulation

R-13 Poorly insulated wall

R-19 6 inch fiberglass insulation

 

Lighting Loads

.5-1.0 WATTS/SF      LOW – HALLWAYS, VERY EFFICIENT BUILDINGS

1.5-2.0 WATTS/SF    MEDIUM – TYPICAL OFFICE BUILDINGS

2.5-3.5 WATTS/SF    HIGH – LABS, TESTING, ETC.

A typical house uses 2000 kWh/year on lighting for all incandescent lamps; CFL/LED can reduce that by 60%

Lighting commonly accounts for 20% of residential energy use and 40% of commercial use

 

Plug-in electrical loads

.3-.5 WATTS/SF       LOW – OLDER OFFICE BUILDINGS – VERY FEW Personal Computers

.5-1.0 WATTS/SF     MEDIUM – TYPICAL OFFICE SPACE

1.0-1.5 WATTS/SF   HIGH – DENSELY OCCUPIED OFFICES – EVERYONE WITH A P.C.

Plug loads can be up to 80% of electrical use in well-insulated homes (65% is typical)

Consumer electronics use 15% to 20% of residential energy (typical household uses 1700 kWh/year for TV, computers, etc.)

 

Gas/water:

California average residential gas use: 50% water heating, 40% space heating, 10% other (cooking…)

Typical hot water loads: First occupant: 20 gal/day, Next occupant: 15 gal/day, All others: 10 gal/day

 

Miscellaneous:

Site-to-source multiplier: 3.4 units of energy at power plant are needed for 1 unit in the home

Energy inflation: historically 6-7% (EIA usually underestimates at around 3%)

Typical Household Consumption in kWh/yr/home

Texas 14000

Ontario 10000

California 6500

Netherlands 3000

 

Solar:

Solar water heater can provide 60-80% of residential use

PV costs: $6-8/DCW residential, commercial/utility scale as low as $4/DCW

Payback years for solar PV and solar hot water systems of all competitive varieties are 12-14 years

 

Acknowledgements: information on this page came from several sources, including:

Chris Calwell, ecova.com

Gary Gerber, CalSEIA

Southern California Edison Energy Education Center

James Waltz