The basic principles of heat pumps were first introduced by Nicolas Carnot in 1824. Essentially known as a type of refrigeration cycle, heat pumps underwent a significant transformation in 1850 when Lord Kelvin proposed that refrigeration machines could also be used for heating purposes. This marked the first deployment of heat pumps. Just before World War II, many engineers worked intensively on developing heat pumps. Although important advancements occurred after the 1950s, the relatively high installation costs led to a decline in their popularity.
The global energy crisis of 1973 renewed interest in heat pumps. Heat pumps efficiently utilize low-temperature heat obtained from nature. Technically, their operating principle is no different from a simple refrigerator used in homes today. These pumps can be used alone or with supplementary systems. Low-temperature heat extracted from air, water, or the ground is evaporated using refrigerants. The resulting vapor is then compressed to achieve high temperatures, which are subsequently transferred to the distribution system.
Heat pumps are used seamlessly for heating in winter and cooling in summer. Compared to fossil fuel-based systems, heat pumps offer significantly higher savings, often exceeding 50%. There are three main types of heat pumps: air-source, water-source, and ground-source.
Efficiency and Performance of Heat Pumps
A common question from prospective users is the efficiency of these pumps. Heat pumps significantly reduce carbon emissions and serve as an excellent alternative to traditional heating systems. The efficiency of heat pumps is measured by the COP (Coefficient of Performance), which represents the useful heating ratio. Cooling efficiency is similarly measured by the EER (Energy Efficiency Ratio). Despite their advantages, heat pumps are not yet widely known but are gradually gaining popularity. In the near future, central heating pumps are expected to see increased usage across various applications in Turkey due to their economic benefits.
Benefits of Heat Pumps
Central heating pumps are highly valued in heating systems. They transfer energy from one source to another, offering numerous benefits. They can achieve savings of 40–50%, are environmentally friendly, and reduce carbon emissions. These pumps can meet multiple needs simultaneously, eliminate the need for chimneys, and do not produce waste gases, making them a clean energy solution. With proper planning and installation, users can fully benefit from these advantages, gaining both environmental and financial benefits.
Operating Principle of Heat Pumps
Heat pumps primarily use air, water, or ground as the heat source. The choice of source depends on the region and intended use, with stability being a critical factor; ground sources are generally the most stable, although initial investment costs are higher. Advances in compressor technology have brought the performance of ground-source and air-source heat pumps in temperate regions closer together.
Closed-loop heat pumps use refrigerants (such as Freon). The cold refrigerant absorbs heat while passing through the evaporator and vaporizes. The vapor is then compressed by the compressor and sent to the condenser. The refrigerant exiting the condenser passes through an expansion valve, reducing its pressure and temperature back to the evaporator conditions, completing the cycle.
There are four main components in a heat pump: the expansion valve, compressor, evaporator, and condenser. Although refrigeration units and heat pumps operate on the same cycle, their purposes differ: refrigeration units aim to cool a space, while heat pumps aim to heat it.
- For optimal performance, certain conditions must be met:
- Source temperatures should remain relatively stable,
- Source temperatures should be sufficiently high,
- The source should be abundant and minimally affected by geographic conditions,
- The source should not cause corrosion,
- The source should be clean.
The efficiency and performance of heat pumps largely depend on the characteristics of the heat source.