An alternative to traditional energy. See how a heat pump works

Heat pumps have become very popular today due to the increasing interest in green energy.

Renewable energy sources are an excellent alternative to traditional coal energy, which is why an increasing number of countries decide to change their energy economy to a greener one. Despite the popularity of heat pumps, few people actually know how they work.

The history of heat pump: where did this groundbreaking invention come from?

It might seem that the heat pump was invented and constructed within the last two decades. It turns out that the history of the heat pump dates back to the 19th century. In 1824 Frenchman Nicolas Carnot published the first principles of heat pump operation. At that time, it was just a theory supported by a few experiments, so it took more than 100 years to create a fully operational heat pump. The first big heat pump systems were put into operation in Zurich to heat the congress building, the town hall, offices and an indoor swimming pool.

The first ground source heat pump was activated in the United States in 1945. It is worth noting that this pump was installed in the house of its designer, Robert C. Webber, in Indianapolis. The device was equipped with a compressor having a nominal power of 2 kW.

Heat pump technology has been developed over decades, which is why modern technological solutions make current heat pumps incredibly efficient and effective.

Main types of heat pumps

Heat pumps are classified according to the so-called lower heat source. Hence, we divide them into ground, water and air source devices. Often, we can also see heat pumps classified as air-water, water-water and glycol/brine-water pumps. Air-to-water heat pumps are the most popular type at this time. They do not require additional expenditure on the collection of heat from the lower source.

Heat pump operation depending on the type of lower source

At this point, we should point out that the heat pump operation is determined by the type of the lower heat source. Modern heat pumps come with three basic types of the so-called lower source: air, water and ground, meaning that heat pumps are divided into:

• An air source heat pump uses a fan that allows air to flow through the heat exchanger. As we already mentioned, the heat is then received through the refrigerant. Remember that there are two types of air source heat pump – monobloc and split pumps.
  
  In a monobloc pump, the refrigerant is condensed in the outdoor unit. It then transfers the heat to the heating water or glycol. Then water or glycol is pumped to the hydraulic module in the house and further distributed in the system. In the case of a monobloc pump, the entire refrigeration system is enclosed in a unit outside the building. KOSPEL offers a monobloc heat pump set. The other type – split air source heat pump – differs from the monobloc, as its outdoor unit is connected to the internal hydraulic module through tubes with a refrigerant.
• A ground source heat pump is characterised by the most stable source of heat. It is worth mentioning that it is also the most expensive investment option. A vertical borehole or a serpentine-shaped heat exchanger placed in the ground below the freezing level is filled with glycol. The ground is heated by sun rays, allowing the heat to be used for operating the pump, while boreholes utilise geothermal heat. This type of heat pumps is limited only to the indoor unit containing the entire cooling circuit, which consists of the primary exchanger receiving heat from an external source and the secondary exchanger for transferring the heat to the heating system.
• A water source heat pump operates very similarly to a ground source pump. The difference lies in the source of heat, which is water from a reservoir (lake or river) or from groundwater. We should emphasize, however, that water source heat pumps are the least common type of pumps because of the specific heat source conditions. A water source heat pump requires a body of water, such as a lake, near the house.

Air source heat pumps remain the most popular type due to their simple installation and the great availability of air as the heat source.

Heat pump operation and design

We know the history of heat pump, so now let’s find out how it works. Surprisingly, heat pumps are based on the same principle of operation as refrigerators. As strange as it sounds, a refrigerator and a heat pump work in a similar way – refrigerators take heat from inside them and transfer them outside (which is why the back of the refrigerator is always warm). Heat pumps extract heat from the outdoor air, ground or water and transfer it into our house.

The key to the heat pump operation is the refrigerant. Liquid is evaporated at a specific temperature, which can be clearly seen in water, for example: water for tea must reach 100°C to boil in the kettle. It is then easy to get burned by the vapour produced by boiling water. It happens to everyone, and the cause is the fact that water gives off heat when condensing as vapour.

It is worth noting that we just need to find a refrigerant that evaporates at a temperature lower than 100°C to achieve the same effect of heat absorption. Some refrigerants are able to evaporate at sub-zero temperatures, so we can gain heat even from air that is close to zero temperature (or even below).

Why use a heat pump – advantages

A heat pump is a great alternative to traditional heating of house and domestic hot water. It should be pointed out that heat pumps are perfect in combination with a photovoltaic system. The combination of photovoltaics with a heat pump provides environmentally-friendly and economical heating at home, which is why this solution is so popular today.

The main advantage of heat pump is very comfortable and convenient use. It is worth noting that the heat pump is a renewable energy source, so it gives you self-sufficiency when combined with PV. Exchangers with a large coil surface are especially recommended for heat pumps. Your heat pump will also need a buffer tank for smooth, safe and cost-effective operation.

There are many benefits of using heat pumps. These devices have a large impact on reducing energy bills, they do not emit pollutants and are completely safe to use. Due to their design and technology, heat pumps are practically maintenance-free.

Thanks to quiet and clean operation, a heat pump can usually be installed at any desired location. Heat pumps perfectly play their role in houses as well as in commercial/public utility buildings.