Solar Hot Water Systems Glossary

Collector Efficiency - The ratio of usable heat energy extracted from a collector to the solar energy striking the cover.

Cylinder - Water storage tank inside the building where the transfer of heat between the glycol fluid and the water to be used takes place. Specialist cylinders are required for use with solar water heating systems.

Flat Plate Collector - A solar collection device in which sunlight is converted into heat on a plane surface without the aid of reflecting surfaces to concentrate the rays.

Heat Exchanger - A device, such as a coiled copper tube immersed in a tank of water that is used to transfer heat from one fluid to another through a separating wall.

Heating Season - The period from early autumn to late spring during which additional heat is needed to keep a house comfortable for its occupants.

Indirect System - A solar hot water heating or cooling system in which the solar heat is collected exterior to the building and transferred inside using ducts or piping and, usually fans or ducts.

Open System - Some part of the system is open to the atmosphere, or system contains fresh or changeable water.

Passive System - A solar heating or cooling system that uses no external mechanical power to move the collected solar heat.

Percentage of Possible Sunshine - The percentage of daytime hours during which there is enough direct solar radiation to cast a shadow.

Thermal Capacity - The quantity of heat needed to warm a collector up to its operating temperature.