What is the Heat Pump Water Heater units(HPWHs)?

Heat pump units are a well established technology for space heating. Today air source heat pump or water source heat pump is widely applied around the world.  The same principal of transferring heat is at work in heat pump water heaters (HPWHs) except that they extract heat from air (indoor, exhaust or outdoor air) and deliver it to water. Some models come as a complete package including tank and back-up resistance heating elements while others work as an adjunct to a conventional water heater. Because it extracts heat from air, the HPWH delivers about twice or more the heat for the same electricity cost as a conventional electric resistance water heater.
The simplest HPWH is the ambient air-source unit, which removes heat from surrounding air, providing the additional benefit of space cooling. Exhaust air units extract heat from a continuously exhausted air stream and work better in heating dominated climates because they do not cool ambient air. Some units can even be converted between the two modes of operation for optimum operation in either summer or winter. In mild climates you can locate units in unheated but protected spaces such as garages, essentially using outdoor air as a heat source. A variation of the stand-alone heat pump water heater is the de-superheater feature available on some central air conditioners. It provides economical supplemental water heating as a byproduct of air conditioning. De-superheater water heating can be part of an integrated package with a heat pump or air conditioner system. In most such systems, the heat pump water heating only occurs
during normal demand for space conditioning, with resistance electric coils providing
water heating the rest of the time. During the cooling season, the de-superheater actually improves the efficiency of the air conditioning system while heating water at no direct cost. In an average climate, a de-superheater might meet 20% to 40% of annual water heating demand.

How does it work?

In a Air Source Heat Pump Water Heater, air is cooled as it passed through the evaporator’s fins(with the help of a fan to improve efficiency), while at the same time, water is heated as it passed through the condenser’s heat-exchange surfaces.

Commercial Tank Systems
Commercial-Size HPWHs are tank systems, where the heat pump apparatus stands alone. Heat is transferred from the condenser to the water condenser via a heat exchanger and a small pump, using the tank’s water as a thermo-storage medium.

Within several hours running, the heated water is the storage for the peak demand. The advantage of this system is the small size unit selected via a large tank to cut down the original investments.

Application

As the high efficiency heating equipment, HPWHS can be applied in most buildings with large, steady requirements for hot water, such as residences occupied by larger families instead of electric heater or gas heater.

 

For those who enjoy swimming regardless of the weather, a Heat Pump is the recommended method. It is also the preferred method for therapy or athletic trainers, and also when a home is not "solar feasible" (i.e. solar will not fit on roof.) A heat Pump, when properly sized, can maintain any desired pool temperature between 80 and 90 degrees, regardless of outside weather conditions. A Heat Pump will work when the outside air temperature is above 45 degrees. Due to their high efficiency, heat pumps have a low cost of operation.

Also HPWHs is ideal for facilities where heavy volume of hot water is used on aconstant base such as Hotel, school, Restaurants and so on.

Economically Analyze
Traditional water heater mainly consumes electricity, gas, fuel etc., all high-level energy resources. The everyday 55℃ hot water is of low-level energy. Even if the heating up process could be of 100% efficiency, which looks like none of the energy is lost, but is actually with great entropy changing lost. This causes a lot of unreasonable energy been wasted. For the air-source heat pump water heater, operational cost is rather low, with 80% lower than electrical water heater, 72% lower than natural gas water heater, 64% lower than diesel oil water heater, even lower than solar water heater. Furthermore it doesn’t generate any poisonous object, and have longer life than traditional water heaters.

Comparison among different water heaters.
Table 1: Cost-effectiveness of a residential-size HPWH versus an electric resistance water heater Heat pump water heaters produce significant energy savings can yield short payback periods for the incremental retail cost in some cases.

 
Table 2: Cost-effectiveness of a residential –size HPWH versus a natural gas tank water heater When natural gas prices are high and electricity prices are low, HPWHs can make economic sense when compared to gas water heaters.

Products

Residential product

 
Comercial product

Pool heater

 

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