Water-source heat pump systems provide highly efficient zone-controlled heating and cooling throughout a building by using water circulating in a closed piping loop as a thermal energy transport and exchange medium.
Individual heat pumps add or remove heat from the air within each zone as required to meet its unique heating or cooling load. During zone heating, they extract needed heat (thermal energy) from the common water loop. During zone cooling, heat is rejected into the water loop where it can then be shared with all other heat pumps throughout the building. Thus rejected heat, which is wasted to the outdoors in most HVAC systems, is completely utilized before any new energy source is used for heating the building.
Buildings contain year-round sources of thermal energy (internal heat gains) that are recovered and recycled by a water-source heat pump system, such as:
The electrical energy used for lighting in most structures varies from 1 to 4 Watts per square foot [11 to 13 Watts per square meter].
Humans emit thermal energy ranging from 300 to 500 Btu per hour [88 to 147 Watts] depending upon their activity.
The energy consumed by equipment such as computers, printers, copiers, and motors is emitted as heat if they are located within the conditioned space.
Perimeter zones with large glazed areas may require daytime cooling even during cold weather.
The thermal energy recovered in the water loop of a water-source heat pump system can be used for most purposes that require heat, such as:
Water-source heat pumps in zones that require heating extract thermal energy from the water loop.
Special “water-to-water” heat pumps extract thermal energy from the water loop to heat service hot water, swimming pools and spas, or to serve hydronic loads such as snow-melt systems.
Dedicated “outside air” heat pumps extract thermal energy from the water loop to heat outside air used for ventilation.