Common Heat Pumps
There are also different types of water-source heat pumps. A variety of products are available, for both residential and commercial applications; there are water-to-air heat pumps, water-to-water heat pumps and hybrids between the two. Some manufacturers are now producing a reversible heat pump for chillers also.
The water-to-air heat pumps are designed to replace a forced air furnace and possibly the central air conditioning system. The term water-to-air signifies that the heat pump is designed for forced air applications and indicates that water is the source of heat. The water-to-air system is a single central unit that is capable of producing heat during the winter and air conditioning during the summer months. There are variations of the water-to-air heat pumps that allow for split systems, high-velocity systems, and ductless systems.
A water-to-water heat pump is designed for a heating-system that utilizes hot water for heating the building. Systems such as radiant underfloor heating, baseboard radiators and conventional cast iron radiators would use a water-to-water heat pump. The water-to-water heat pump uses the warm water from the loop field to heat the water that is used for conditioning the structure. Just like a boiler, this heat pump is unable to provide air conditioning during the summer months.
A hybrid heat pump is capable of producing forced air heat and hot water simultaneously and individually. These systems are largely being used for houses that have a combination of under-floor and forced air heating. Both the water-to-water and hybrid heat pumps are capable of heating domestic water also. Almost all types of heat pumps are produced commercially and residentially for indoor and outdoor applications.
Geothermal Heat Pump in combination with cold/heat storage
Geothermal heat pumps in combination with cold/heat storage is used extensively for applications as the heating of greenhouses. In summer, the greenhouse is cooled with ground water, pumped from a aquifer, which is the cold source. This heats the water. the water is then stored by the system in a warm source. In winter, the relative warm water is again pumped up, which derives heat. The now cooled water is again stored in the cold source. The combination of cold and heat storage with heat pumps can be very interesting for greenhouses as it may be combined with water/humidity application. This obviously is a great advantage for greenhouses. In the (closed circuit) system, the water used as a storage medium for heat is done in a first aquifer, while the cold water is held in a second aquifer. The heat and cold stored in the water mass is when needed spread as hot or cold air through the use of fans. In the described system, everything can be automated.
While this article focuses on water-source systems in which the refrigerant exchanges its heat with a water loop that is placed in the ground, a direct exchange system (often known as DX geothermal) is one in which the refrigerant circulates through a copper pipe placed directly in the ground. This eliminates the need for a heat exchanger between the refrigerant loop and the water loop, as well as eliminating the water pump. These simpler systems are able to reach higher efficiencies while also requiring a shorter and smaller pipe to be placed in the ground, reducing installation cost. DX systems are a relatively newer technology than water-source. DX systems, like water-source systems, can also be used to heat water in the house for use in radiant heating applications and for domestic hot water, as well as for cooling applications. Though corrosion or cracking of the copper loop has sometimes been a concern, these can be eliminated through proper installation. Since copper is a naturally-occurring metal that survives in the ground for thousands of years in most soil conditions, the copper loops usually have a very long lifetime.