A Guide to Heat pumps
Did you know that heat pumps are the newest and most efficient form of space and water heating systems? Partly because they use renewable heat sources available in our environment to extract warmth and partly due to advances in heating technology.
What are heat pumps?
Heat pumps provide both space and water heating, as well as cooling in one system. They work using a heat transfer process.
They do not generate heat or convert electricity into thermal energy like conventional resistance heaters. Instead, they extract natural heat from one place and transfer it to another. Heat pumps use electricity to apply a little more energy to raise the temperature to the level required.
Whilst a heat pump will use an external energy source like electricity for the transfer process, the heat transfer can be three or four times larger than the electrical power consumed. This means that they have better energy efficiency than conventional electrical resistance heaters. For example, if a heat pump products 2.5 kilowatts of thermal energy, they actually use less than 1 kilowatt of electricity!
This makes a heat pump system quite cheap to run and the most likely to reduce your carbon footprint.
How do heat pumps work?
The most common design of a heat pump involves four main components – a condenser, an expansion valve, an evaporator and a compressor. The heat transfer medium circulated through these components is called refrigerant.
During the heating cycle, a heat pump will:
- Extract heat from the external environment (air or ground) using an evaporator that contains a liquid or gas refrigerant and transfer it to a compressor.
- The vapours are compressed to increase their pressure and temperature.
- The warmed vapours are then liquefied in a condenser unit, which emits the condensation heat to the heating medium.
- The refrigerant then passes through an expansion valve where its pressure is lowered again and continues back to the evaporator where the cycle is repeated.
Are there different types of heat pumps?
Heat pumps tend to have two model types: one that extracts heat from a ground source and the other an air source.
Ground-source uses shallow underground heat exchangers as a heat source or sink, and water as the heat transfer medium. This is possible because below ground level, the temperature is relatively constant across the seasons, and the earth can provide or absorb a large amount of heat. Ground source heat pumps work in the same way as air-source heat pumps, but exchange heat with the ground via water pumped through pipes in the ground.
Air source, like the Rointe Dalis, extract heat from the air which is then is absorbed at low temperature into a fluid. This fluid passes through a compressor, increasing the temperature, and transfers that higher temperature heat to the heating and hot water circuits of the house.
There are two main types of air source heat pumps: air-to-water and air-to-air. Choosing an air-to-water or an air-to-air system will determine the type of heat distribution system you need.
- Air-to-water absorbs heat from the outside air and transfers the heat to water. The heated water can then be used for domestic use such as showering or bathing, or to heat radiators in a wet system which heats your room or home.
- Air-to-air require a warm air circulation system to move the warm air around your home. They will not provide you with hot water.
Some heat pumps only use a one-way direction i.e. transfer of energy to heat water or a room, whilst reversible heat pumps work in either direction to provide heating or cooling to the internal space.
Rointe Dalis heat pump installation diagram
How do you measure a heat pumps' efficiency?
When discussing heat pump efficiencies, the following terms are commonly used: coefficient of performance (COP), seasonal coefficient of performance (SCOP) and seasonal performance factor (SPF).
The higher the number, the more efficient a heat pump is, the less energy it consumes, and the more cost-effective it is to operate.
There are several factors that will affect the efficiency of a heat pump, such as auxiliary equipment, technology, size and control system, but also temperature and humidity conditions: the efficiency drops when the temperature difference increases or when freezing can occur.
The main advantages of heat pumps
With an A+ energy rating, the Rointe Dalis unvented electric heat pump and storage tank is an all-in-one system, designed for high-efficiency production of domestic hot water.