As environmental targets become more stringent, the demand for heat pumps is growing. They offer improved performance due to their high efficiency and on-site energy generation. Heat pumps have the potential to provide a more efficient and cost-effective solution for both new and existing developments, using renewable energy from natural sources to provide heating and hot water.
They can also often be reversed to provide cooling, which is becoming increasingly important in the design of HVAC systems for all types of buildings due to the high risk of overheating.
Air Source Heat Pumps
Air source heat pumps use heat from the ambient air as their primary source of energy. They can operate at temperatures as low as -25°C, although they are most efficient at warmer outdoor temperatures.
Air-source heat pumps are often easier to install than ground-source or water-source alternatives, requiring only a connection to the main water supply, an electrical connection and, in some cases, a refrigerant connection. This type of heat pump is ideal where space is limited as there is usually no need to bury pipes or be near other energy sources such as boreholes, canals or large bodies of water. Air-source heat pumps can be used in residential and commercial applications of all sizes, including high-rise buildings where the units can be installed on the roof or at ground level.
Cold air is full of energy. Air is an inexhaustible source of energy and is available everywhere. The latest models of air-to-water heat pumps allow heating at outdoor temperatures as low as -25°C. Such low temperatures still mean energy savings of 50%. This is the cheapest type of heat pump with easy and affordable installation and maintenance.
Air-to-water heat pumps are usually designed to independently cover all the heat losses of a building at temperatures as low as -5°C. Below this threshold, the heat pump works in combination with a second heat source. In this way, the heat pump covers more than 98% of the building's heating requirements. In new buildings, the second heat source is usually an electric heater, but in existing buildings with a good conventional heating source, the latter can also be used. The electronic control system makes it easy to set the switching point from the 1st to the 2nd heat source.
Water Source Heat Pumps
The heat from the underground water is a very good source for the heat pump. Its advantage is a relatively constant temperature level, approximately between +7°C and +12°C. To use underground water, two boreholes must be drilled for pumping and returning the underground water. The first borehole is equipped with a hose and a submersible pump. During operation, the pump drives the water through the heat pump and uses its heat energy; it releases the water, which is a few degrees Celsius cooler (from 2 to 4 °C), into the other borehole, which is a few meters (15 - 20 m) away from the first one, and into the underground water. The amount of water in the suction hole must be sufficient for continuous operation when the heat demand is highest. To use underground water, you need a permit, the water must undergo chemical analysis before starting the work. Ground water is an ideal heat source because of its relatively high temperature, it can achieve a high COP. This means that water is the most energy efficient (on an annual average). Water-to-water heat pumps provide high heating capacity with very small external dimensions. This robust and innovative model is further enhanced by a special stainless steel plate heat exchanger.
Ground Source Heat Pumps
Brine/water heat pumps use the thermal energy stored in stone or earth. Here we can find a large amount of solar energy that can be used to heat the house and/or water. The amount of energy that can be extracted from the ground depends on the composition of the ground, the power of the heat pump and the type of use of the source. The heat is extracted by means of a fluid that circulates in a closed pipe system that is laid at a depth of 120-130 cm (horizontal collectors), or the pipe probes are inserted into boreholes at a depth of 60-140 cm (vertical probes). The circulating water transfers heat to the heat pump, which uses electricity to bring it to a higher temperature level (up to 63°C) and then returns cooler by about 3°C.
Due to the nature of ground source heat pump installations, ground work and existing infrastructure need to be considered early for this type of heat pump, which can be more costly to install depending on the building location.
Ground source heat pumps are used in commercial and residential buildings and often offer the best year-round efficiency due to the potentially higher and more consistent temperature of the ground from which they draw energy.