accumulator		an opening; in solar collectors, the area through which solar radiation is admitted and directed to the absorber.
adiabatic		a component of a heat pump that stores liquid and keeps it from flooding the compressor.
albedo		to filter into or through; permeate.
amorphous		the fibrous material remaining after the extraction of juice from sugarcane; often burned by sugar mills as a source of energy.
azimuth		non-crystalline semiconductor material that has no long range order.
bagasse		capacity for producing a desired result or effect.
infiltration		the ratio of light reflected by a surface to the light falling on it.
efficacy		the angle between true south and the point on the horizon directly beneath the sun.
auxiliary		a system intended to back up another, such as a back up energy system.
aperture		an exchange in volume and pressure of a parcel of gas without an exchange of heat between the parcel and its surroundings.