In June 2019, the UK became the first major economy in the world to pass laws to end its contribution to global warming by 2050.
New targets will require the UK to bring all greenhouse gas emissions to net zero by 2050. Achieving the target of zero carbon will not be easy; Government, supply chains and manufacturers will have to come together in a consistent way over the coming decades. Consumers will also have to learn to embrace new technologies, such as heat pumps.
How does a heat pump work? In essence, a heat pump is like a fridge working in reverse. It absorbs naturally-occurring heat from the air, earth or water outside to heat your environment and water. Since it transfers heat rather than generates it, heat pumps are one of the most efficient means of space and water heating.
Heat naturally moves from a hotter area to a colder one. A heat pump works by reversing this process, using a small amount of electricity to do so. It does this using the vapour-compression cycle common to most refrigeration systems.
There are four stages to the vapour-compression cycle of a heat pump, through which a refrigerant is circulated. This refrigerant acts as a medium, which transfers the heat from one stage to another.
Heat is brought into a heat exchanger – known as the evaporator – from outside. Depending on the type of heat pump, this low-grade heat can come from any number of sources. For instance, ground-source heat pumps absorb heat from the earth, air-source from the air, and water-source from a nearby lake or pond. This heat causes the refrigerant to evaporate. Within the evaporator, the low-pressure, low-temperature refrigerant can absorb heat even in very cold conditions (down to -20°C).
The evaporated refrigerant is compressed, which drives the temperature up. In more technical terms, the low-grade heat is upgraded into a useably high temperature.
The refrigerant gas transfers heat into the central heating system. This causes the refrigerant to condense back into a liquid. This happens in the condenser, a second heat exchanger, where the cooler water from the central heating system absorbs the heat. This heat is then either circulated around an emitter system (radiators or underfloor heating) or it is used to heat water.
4: Expansion valve
The cooled refrigerant passes through the expansion valve, which decreases the pressure. This further decreases the temperature, before the refrigerant goes back to the evaporator so the cycle can start again.
There are two main types of heat pump: air-source and ground-source. Whilst they both use the same method of heat transfer as mentioned above, the way they bring low-grade heat into the evaporation-compression cycle is slightly different.
An air source heat pump is the most popular type of system. Sitting outside your building, the heat pump looks quite similar to a standard air conditioner. In fact, the method of heat transfer for air conditioners is very similar to the one above, only in reverse.
Heat from the sun warms the air around us, which is then drawn into the heat pump unit by the fan. This heat is extracted from the air into the heat exchanger coil – the evaporator – and so the cycle begins. The fan is there to keep a constant flow of warm air coming into contact with the heat exchanger.
A ground source heat pump uses the solar energy stored in the earth as the source of heat for the evaporator. It collects the heat through pipes laid underground known as a ground loop or ground array. A mixture of water and a special type of anti-freeze is then pumped through this network of pipes underground, absorbing the naturally-occurring heat below the frost line. The antifreeze-water mix then delivers the heat to the evaporator within the heat pump, and the same evaporation-compression process begins.
The most popular setup for a ground source heat pump is to lay the heat-absorbing pipes horizontally. You’ll need a large surface area outside to lay the pipes in this way, or if you don’t have that much space you could opt for a vertical loop system, which involves drilling deep boreholes underground.
Heat pumps are actually the most efficient alternative to fuel, oil, and electrical systems, when it comes to the process of heating and cooling. They supply a larger capacity of heating and cooling than the amount of electrical energy that is used to run it. In fact, the efficiency rate is able to go up as high as 300%.
In summary here are some of the most significant advantages of heat pumps:
- Heat pumps are much safer than systems that are based on combustion.
- They are cheaper to run than oil and gas boilers.
- Heat pumps will reduce your carbon emissions, and they will provide an efficient conversion rate of energy to heat.
- Heat pumps require less maintenance than combustion heating systems.
- They have a very long lifespan of up to 50 years. As a result, they are extremely reliable and a steady source of heat.
- You may be eligible for payment under the Renewable Heat Incentive (RHI) scheme.
Please contact our experts at Dancold Ltd. to discuss the suitability of a heat pump for your requirements. If a heat pump is a viable solution for your project, then we would provide you with some design options to assist you in reaching a decision. Alternatively, if you have an existing heat pump system and you require technical assistance, we can arrange for one of our fully trained technicians to visit your site.