High Temperature Heat Pump Guide
Market potential of high temperature heat pumps
The coefficient of performance of the heat pump usually increases with the lower the required output temperature: therefore, the designer’s goal is to use a lower temperature cooling system, such as floor heating, where 40°C is sufficient to provide a comfortable room temperature. However, if the heat pump is used in an existing building with a heat radiator (such as a standard radiator) with a limited heat load, it is appropriate to specify a high-temperature heat pump to avoid interruption of the entire building's heat dissipation system due to renovation.
There are high-temperature heat pumps that can provide an output temperature of 80°C, which is sufficient to meet the hot water demand and use standard-sized radiators to heat the building. Although the COP will decrease if the output temperature rises to 80°C, the well-designed inverter-driven high-temperature heat pump has a good control system, including weather compensation, and will only provide 80°C when needed: otherwise it will adjust the temperature. When the heat load is lower than the peak demand, the heat pump provides a lower temperature with higher efficiency.
Our existing heating system
Most households have installed gas or oil boilers and high-temperature radiators. For older non-condensing boilers, the temperature from the boiler to the radiator is 80 degrees.
For modern condensing boilers, the heating temperature should be lower in order for the boiler to operate with higher efficiency, although this rarely happens in practice. However, the 65 degree temperature of the boiler can definitely run a heating system based on a standard radiator.
Obstacles to low-temperature heat pumps
All air source heat pumps are viable alternatives to our gas and oil boilers. Their standard capacity is between 3-16kW, and it is possible to heat most British homes; on very cold days, the average heat demand is only 6-8kW.
However, when the heating system temperature is between 35-45 degrees, the low-temperature heat pump has the highest efficiency. Our houses can still use this lower temperature for heating, but our radiators need to be much larger to emit more heat. Therefore, unless we significantly increase the level of insulation, the new low-temperature heat pump will also mean a new radiator.
High temperature heat pump
The HT heat pump is designed to operate at 80 degrees, so it can heat standard radiators. Other advanced heat pumps operate at temperatures up to 65 degrees and are also ideal for existing heating systems. (See the table below.)
The disadvantage is that the installation cost of high-temperature heat pumps is higher and the efficiency is lower than that of low-temperature heat pumps. The external unit is also much larger, so a garden is needed. Nevertheless, they may be the only choice for some families.
When is a high temperature heat pump suitable for me?
There is no doubt that the next decade will promote the insulation of our houses so that we can adapt to low-carbon technologies, especially low-temperature heat pumps.
However, certain properties may not achieve significant insulation levels, such as the listed and older properties. If your heating system is unlikely to operate at 45 degrees, then a high-temperature heat pump is a good choice. It can be installed now and you can immediately partially decarbonize your house.
High temperature efficiency
With the correct settings, the homeowner can expect the SCOP to be approximately 2-2.5. This means that for every unit of electricity, the unit will generate 2-2.5 units of free energy from the air.
SCOP is the annual efficiency of the heat pump. In winter, when the heat pump will operate at a higher temperature, the efficiency will be significantly reduced, and in the spring and autumn months, when it can operate at a lower temperature, the efficiency will be significantly reduced.
Although high-temperature heat pumps can heat 65 or 80 degrees, this does not mean that they should be operated at this temperature. The higher the temperature, the lower the efficiency. The heating system should be designed as low as possible and only rely on the highest temperature when absolutely necessary.