CEA flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Level 2 energy audit
- An energy survey that breaks facility use into end uses, establishes an energy balance, and identifies and costs energy conservation measures with savings estimates and payback.
- Audit baseline period
- The reference period of typically 12 consecutive months used to characterize normal energy use, adjusted for occupancy, weather, and major facility changes.
- IPMVP Option C
- A measurement and verification approach using whole-facility utility meter data with routine and non-routine adjustments to determine savings from a multi-measure retrofit.
- Energy use intensity
- Annual site energy consumption divided by conditioned floor area, usually expressed in kBtu per square foot, used to benchmark a building against peers.
- Balance-point temperature
- The outdoor temperature at which internal gains offset envelope losses so no heating is needed, often 55 to 65 degrees Fahrenheit rather than the standard 65.
- Load factor
- Average load divided by peak load over a period; a low value indicates demand charges may dominate the bill and demand management is worthwhile.
- Weather normalization regression
- A regression of monthly energy against heating or cooling degree days whose slope gives weather sensitivity and whose intercept gives weather-independent baseload.
- Three-phase power formula
- Real power in watts equals the square root of three times line voltage times line current times power factor for a balanced three-phase load.
- Pitot tube velocity
- Duct air velocity in feet per minute equals 1,096 times the square root of velocity pressure measured in inches of water column.
- Interval data logging
- Recording measurements at fixed short intervals, typically 15 minutes, to capture load profiles, duty cycles, and peak demand rather than single spot readings.
- Simple payback period
- Initial measure cost divided by annual energy cost savings, expressed in years; it ignores time value of money and measure life.
- Levelized cost of conserved energy
- Annualized capital cost of an efficiency measure divided by its annual energy savings, compared against the marginal cost of purchased energy.
- Demand charge
- A utility billing component based on the highest kilowatt demand in a billing period, often with a ratchet that sets a floor for future months.
- Internal rate of return
- The discount rate at which a project's net present value equals zero; projects are accepted when it exceeds the owner's hurdle rate.
- Lumen method
- Illuminance equals lamp lumens times fixture count times coefficient of utilization times light loss factor, divided by the area served.
- Lighting power density
- Connected lighting watts divided by floor area in watts per square foot, compared against code allowances for the space type.
- Ballast factor
- The ratio of lamp light output with a given ballast to rated output with a reference ballast; it also scales input wattage.
- Chiller efficiency in kW per ton
- Chiller input power divided by cooling output in tons; COP equals 3.517 divided by kW per ton.
- Affinity laws
- For centrifugal fans and pumps, flow varies with speed, pressure with speed squared, and shaft power with speed cubed.
- Economizer
- A control strategy that uses cool outdoor air for free cooling when outdoor air enthalpy or dry-bulb conditions are favorable compared with return air.
- Demand-controlled ventilation
- Modulating outdoor air intake based on measured occupancy, typically carbon dioxide concentration, to reduce conditioning of excess ventilation air.
- Domestic hot water energy
- Energy in Btu equals gallons times 8.33 pounds per gallon times the temperature rise in Fahrenheit degrees, divided by system efficiency.
- Heat pump water heater
- A water heater using a vapor compression cycle with a coefficient of performance of roughly two to three, requiring conditioned air and condensate drainage.
- Legionella temperature control
- Storing hot water at 140 degrees Fahrenheit with a mixing valve, or at 120 degrees, to avoid the 68 to 122 degree range where bacteria thrive.
- Compressed air rule of thumb
- About one horsepower of compressor power produces four to five cubic feet per minute of air at 100 psig in a typical system.
- Compressed air leak load
- The compressor output consumed by leaks, often 20 to 30 percent of total output, quantified by measuring run time during non-production hours.
- Motor input power
- Kilowatts equal horsepower times 0.746 divided by motor efficiency at the actual load point, not nameplate rating.
- Envelope heat transfer
- Heat flow in Btu per hour equals the assembly U-value times area times the indoor-outdoor temperature difference, plus infiltration losses.
- Blower door test
- A diagnostic that pressurizes a building to measure leakage at 50 pascals, used to estimate natural infiltration and target air sealing.
- BAS trend review
- Analysis of logged building automation data, typically at 15-minute intervals, to find scheduling overrides, stuck valves, and simultaneous heating and cooling.
- BACnet protocol
- A standard data communication protocol for building automation and control networks that allows devices from different vendors to interoperate.
- Battery round-trip efficiency
- The ratio of energy discharged to energy charged, typically 85 to 95 percent for lithium-ion systems, affecting storage economics.