Water-source heat pumps provide zone heating and cooling at the highest rated levels of efficiency.
The water loop inherently recovers much of the energy needed for heating the building, minimizing boiler use. Water-loop heat pump systems operate efficiently under partial occupancy and at part-load conditions.
They also eliminate the double energy waste of zone reheat (cooling with subsequent reheating), which is common in many HVAC systems. This all translates into reduced energy consumption and lower operating costs.
|Fan Coil, Chiller/Boiler 4-Pipe||1.40|
|Variable Air Volume||.94|
|Geothermal Heat Pump||.62|
|Water Loop Heat Pump||.94|
|Per square foot of building space|
The Efficiency Advantages of Using Water
Water is the most efficient way to move thermal energy. For example, a 2 inch [51 mm] water pipe can carry the same amount of cooling as a 24 inch [610 mm] air duct, requiring up to 90% less transport energy in the process and taking up far less space.
The mass of the water loop also provides thermal storage, allowing a substantial amount of heat to be carried from occupied periods into morning warm-up. There is no storage benefit in most HVAC systems.
Water-source heat pump heat exchangers are more compact and efficient than air-cooled heat exchangers because of the much higher mass and thermal conductivity of water, providing closer approach temperatures and higher heat pump efficiencies.
Water-source heat pumps also operate at lower condensing temperatures because they are linked to the outdoor wet bulb temperature (using a cooling tower) or the deep earth temperature (using a ground heat exchanger) instead of the higher outdoor dry bulb temperature, again leading to higher efficiencies and longer service life.
Buildings contain year-round sources of thermal energy (internal heat gains). Read more about how water-source heat pump systems recover and recycle a building’s thermal energy.
Recent Improvements Mean Even Higher Efficiencies
In the mid-1990s, EER (Energy Efficiency Ratio) was 12 to 14. Now, the best water-source heat pumps are 18 to 20 EER, with two-stage units operating at a remarkable 27 EER.