AEE Certified Energy Manager (CEM) flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ASHRAE 90.1

ASHRAE Standard 90.1 sets minimum energy efficiency requirements for commercial and high-rise residential buildings, excluding low-rise residential. It covers envelope, HVAC, lighting, power, and service water heating.

IECC scope

The International Energy Conservation Code establishes minimum energy efficiency provisions for residential and commercial buildings. Jurisdictions adopt it into law and may amend it locally.

ASHRAE 62.1

ASHRAE Standard 62.1 specifies minimum ventilation rates and indoor air quality requirements for commercial buildings to protect occupant health and comfort.

Power factor formula

Power factor equals real power in kW divided by apparent power in kVA. It ranges from 0 to 1 for sinusoidal loads and indicates how effectively current does useful work.

Three-phase power equation

For a balanced three-phase load, real power in kW equals the square root of three times line-to-line voltage times current times power factor, divided by 1,000.

Motor efficiency

Motor efficiency is shaft output power divided by electrical input power, expressed as a percentage. It varies with load and typically peaks near 75 to 100 percent of rated load.

Affinity laws for fans

For centrifugal fans, flow varies directly with speed, pressure varies with speed squared, and power varies with speed cubed, assuming constant system and air density.

Commissioning definition

Commissioning is a documented quality-assurance process that verifies building systems are designed, installed, functionally tested, and capable of operating according to the owner's project requirements.

Retrocommissioning

Retrocommissioning applies the commissioning process to existing buildings not previously commissioned, focusing on identifying and correcting operational problems and low-cost energy-saving opportunities.

Preventive maintenance

Preventive maintenance is scheduled, time-based or usage-based servicing of equipment to reduce failures and maintain efficiency, such as filter changes, belt inspection, and lubrication.

ASHRAE Level 1 audit

A Level 1 energy audit is a walk-through survey that identifies obvious energy-saving opportunities, provides a rough estimate of costs and savings, and helps scope further analysis.

Energy use index

Energy use index divides annual building energy consumption by conditioned floor area, commonly expressed as kBtu per square foot per year or kWh per square meter per year.

Heating degree days

Heating degree days quantify how much average daily temperature falls below a base temperature, typically 65 degrees Fahrenheit, and are used to normalize heating energy use to weather.

IPMVP Option C

IPMVP Option C measures savings for an entire facility using whole-building utility meter data, with adjustments for weather and other changes, and is suited to multifaceted retrofits.

CHP total efficiency

Combined heat and power total efficiency equals useful electrical output plus recovered useful thermal output, divided by fuel energy input, often reaching 60 to 80 percent.

CHP prime movers

Common CHP prime movers include reciprocating engines, gas turbines, microturbines, steam turbines, and fuel cells. Each differs in capacity, electric efficiency, and usable heat grade.

Solar PV yield

Estimated annual PV energy equals system direct-current capacity times peak sun hours times performance ratio. Performance ratio accounts for inverter, wiring, soiling, and temperature losses.

Sensible heat equation

In inch-pound units, sensible cooling load in Btu per hour approximately equals 1.08 times airflow in cubic feet per minute times the dry-bulb temperature difference.

Chiller kW per ton

Chiller efficiency in kW per ton equals 12 divided by EER, or 3.517 divided by COP. Lower values indicate better full-load efficiency.

Air-side economizer

An air-side economizer uses cool outdoor air instead of mechanical cooling when outdoor air enthalpy or temperature is below the return air condition, reducing compressor energy.

Fan affinity laws

For a centrifugal fan, airflow is proportional to speed, static pressure to speed squared, and shaft power to speed cubed, so modest speed reductions yield large energy savings.

PID control

PID control combines proportional, integral, and derivative actions. Proportional responds to current error, integral eliminates offset, and derivative damps response to changing error.

Demand-controlled ventilation

Demand-controlled ventilation modulates outdoor air intake based on measured occupancy indicators such as carbon dioxide concentration, reducing ventilation energy when spaces are lightly occupied.

BACnet protocol

BACnet is an open building automation and control communications protocol that enables interoperable data exchange among HVAC, lighting, and other building systems from different manufacturers.

Thermal energy storage

Thermal energy storage shifts heating or cooling production to off-peak periods by storing chilled water, ice, or phase-change material for later discharge, reducing demand charges and chiller size.

Ice storage latent heat

Ice thermal storage uses the latent heat of fusion, about 144 British thermal units per pound, to store cooling energy with a smaller tank volume than chilled-water storage.

Full versus partial storage

Full storage meets the entire peak cooling load from storage; partial storage uses storage plus operating chillers. Partial storage typically lowers first cost and chiller capacity.

Luminous efficacy

Luminous efficacy is visible light output in lumens divided by electrical input power in watts, expressed as lumens per watt. Higher efficacy means more light per unit energy.

Lighting power density

Lighting power density equals installed lighting watts divided by floor area, typically watts per square foot. Energy codes set maximum allowances by space type.

Daylighting photosensor control

A daylighting photosensor control dims or switches electric lighting in response to available daylight, reducing lighting energy while maintaining target illuminance in the space.

Energy savings performance contract

An energy savings performance contract is an agreement in which an energy service company implements efficiency measures and guarantees savings that repay project costs over the contract term.

M&V savings equation

Verified savings equal baseline energy use minus reporting-period energy use, adjusted for changes in weather, occupancy, or other agreed conditions that affect energy use.