Glossary
Below are definitions of some of the common terminology and abbreviations used on this website.

CHP - Combined heat and power; CHP systems are also known as cogeneration, trigeneration, or total energy systems
DG - Distributed generation; CHP typically is considered a DG system with recovery of thermal energy that otherwise would be wasted
IAQ - Indoor air quality
kW - Kilowatt

Absorption Chiller - Water chiller based on absorption of refrigerant vapor into a liquid solution, pumping of the solution to elevated pressure, and the release (desorption) of refrigerant vapor through addition of heat; absorption chillers require less energy because the pumping process involves a liquid; direct-fired chillers employ natural gas burners, indirect-fired chillers use steam or hot water from a separate process (such as the hot exhaust gases from electric generation); single-, double-, and triple-effect chillers employ multiple stages of desorption and internal use of waste heat to boost efficiency
Demand Charge - Charges for the use of electricity based on the maximum power requirement, electrical demand, during a specified period of time, typically a month ($/kW)
Desiccant - A solid or liquid material with an affinity for absorbing water molecules
Engine-Generator - Electrical generator using a reciprocating, Sterling , or rotary engine
Enthalpy Wheel - Heat exchanger rotating through building supply and exhaust air flows to transfer energy from one air stream to the other
Evaporative Cooling - Lowering the temperature of air through the evaporation from a water or wetted membrane; direct evaporative cooling adds water to the supply air while indirect evaporative cooling adds water to the exhaust air and incorporates a heat pipe or thermal wheel for indirect cooling of the supply air
Fuel Cell - Device for producing electricity from hydrogen using an electrochemical process rather than conventional combustion process to turn a traditional electric generator
Heat Wheel - Heat exchanger rotating through building supply and exhaust air flows to transfer heat from one air stream to another
Latent Cooling Load - Amount of cooling required to reduce humidity of air in conditioned space to specified level for comfort
Line Losses - Electric energy lost as heat in power transmission lines
Microturbine - Turbine-engine driven electrical generator with output power under 100 kw
Power Reliability - Percent or fraction of the time (hours) power is available in a year (8760 hours)
Real Time Pricing - Charges for electrical demand and consumption based on instantaneous cost of production and distribution as opposed to fixed rates or fixed time-of-day rates
Sensible Cooling Load - Amount of cooling required to reduce the temperature of air in the conditioned space to a specified level for comfort
Thermal Wheel - Heat exchanger rotating between two air flows to transfer heat from one to the other
Ton Or Refrigeration Ton - Quantity of cooling available from melting 2000 pounds of ice; 12,000 Btu/h or 3.1413 kW
Vapor Compression Air Conditioning - Cooling system based on compression of a gaseous refrigerant to a high pressure, and heat transfer with changes of state (i.e. Liquid and vapor) to produce useful heating or cooling
Waste Heat - Portion of the energy input to a mechanical process which is rejected to the environment