AHP Operation Principles

Heat pump is a device, which is quite unusual for domestic understanding as it generates more heat than consumes electric energy.

The delusion arises that the efficiency is bigger than 1. As a matter of fact, heat efficiency rate (COP) is really much bigger than 1. It occurs because the energy (consumed by the heat pump) is expended on a heat transfer from a source of low-grade heat energy (with low temperature / enthalpy) to a consumer with higher temperature instead of direct heating (as, for example, in tubular electric heaters or other heat boilers). The heat pump “pumps” heat to a consumer (that is why it is called a “pump”) in such a way that energy consumed by the pump is expended directly on pumping and conventional efficiency (ratio of energy transfer effective work to energy consumed by the pump) is less than 1 as befits.

All heat pumps and climate control systems manufactured today by hi-tech global companies can be divided under the following principle – “source of low-grade energy – energy consumer”. For example, “ground-to-water”, “water-to-water”, “water-to-air”, “air-to-air”, etc. They can also be divided under the type of working medium on which the heat transfer thermodynamic cycle is based.

Nowadays, domestic heat pumps (“warm house”) are widely distributed in Europe for well heat-insulated premises and mild winters. They use low-grade geothermal heat of ground water “water-to-air” or heat of ground itself “ground-to-water”. These solutions are very capital-intensive and inefficient in our climate zones. Air-to-air heat pumps, which efficiently use dump energy from the industrial cooling systems, are usually used for the industrial premises (workshops). Usually freon acts as a working medium in these systems, some up-to-date systems use other more eco-friendly refrigerants (for example, they use CO2 at present).

Almost all modern air-conditioners (including industrial air-conditioners) at the same time belong to “air-to-air” heat pumps, which operate on freon cycle.

As a matter of fact, a thermodynamic heat pump is a conversed refrigerating machine (by the way, in the professional scientific and technical literature it is vice-versa stated that the refrigerating machine is a converted heat pump which extracts heat from the enclosed volume into the environment. Both variants are correct). But the efficiency of freon heat pumps drops sharply during the decrease of ambient temperature below zero, especially below -70…-120°C when it generates heat with efficiency (COP) below 1.

ATT air-cycle heat pump developed by UPEC on the contrary has a maximum of efficiency (COP) at ambient temperature of -200…-300°C and operates successfully till -450°C. At the maximum point its COP is greater than 4, i.e. machine which consumes 20…25 kW of electric energy can generate about 100 kW of heat (!).