Heat Pumps are set to replace gas boilers in the coming years, but what are they and how do they work?
Over the last few years, heat pumps have been in the headlines numerous times, sometimes for good reasons and sometimes for their perceived downfalls.
Unlike gas boilers, heat pumps themselves do not release any carbon emissions and so, like hydrogen boilers are going to have a huge part to play in the country escaping its reliance on fossil fuels over the coming decades.
But what is a heat pump? And how does it work? In this guide, we'll explain everything in simple terms.
Ready to make your home more energy-efficient and cut down on your heating bills? Get a heat pump quote today from our trusted partners at Heat Geek here.
How does a heat pump work?
The environment contains thermal or heat energy, which has a natural tendency to move from a warmer to a colder area.
However, in order for us to heat our cold homes, we need the heat to move in the opposite direction, but how?
The answer is in the nature of gases - when the pressure of a gas increases, the temperature also increases and the opposite is true when the pressure of a gas decreases i.e. the temperature decreases.
This dynamic between gas pressure and temperature is fundamental to how heat pumps function.
Heat pumps work just like refrigerators, in reverse.
The gas heat pumps used aren't the same gas used in boilers but are refrigerant gas, similar to what is used in refrigerators.
Using electricity, the heat pump is able to compress this refrigerant gas, increasing its pressure and as a result its temperature.
The heat produced from the refrigerant is then transferred to the home via the heat exchanger, resulting in the refrigerant gradually cooling down.
It is then able to expand and cool down so that it can be re-used to absorb more heat from outside and start the cycle again.
The heat produced from this process can be used to heat the inside of the home in two main ways, either by a traditional "wet" central heating system or by circulating warm air.
Interested to learn how heat pumps compare to gas boilers? Check out our complete heat pump vs gas boiler guide.
How efficient are heat pumps?
Heat pumps are incredibly efficient and much more so than traditional heating systems like gas boilers.
For example, air-source heat pumps have an efficiency rating of around 300%, while ground-source heat pumps can have efficiency ratings above 400%.
This means for every 1kWh of electricity used, it will generate 3 to 4 times more heat.
This all comes down to the fact that they produce more heat than the amount of electricity they use. The amount of heat produced per unit of electricity used is referred to as the Coefficient of Performance (CoP).
For example, a COP of 3 means that for every 1kW of electricity, 3kW of heat is produced.
Every heat pump model will have its own unique COP score, allowing you to easily identify how efficient it is.
Check out our review of the best heat pump brands of the year to find out which models are most reliable.
Watch Our Air Source Heat Pump UK Case Study in the video below:
Will a heat pump help you save money on heating?
Many people choose to install a heat pump for their green merits i.e. the fact that they release zero carbon emissions. However, this does not always correlate with having cheaper heating and energy bills, so it's important to bear this in mind.
In fact, the Energy Saving Trust highlights that currently running a heat pump is likely to cost more than a gas boiler, however, they do also make the important point that this is likely to change in the future.
The exact costs can vary, but the amount of electricity required depends on the source and input temperatures, so it can vary a lot over a 12 month period.
In addition, the effectiveness and running costs depend on the efficiency of your home, what type of radiators you use and your current electricity tariff.
Therefore, your home's current thermal efficiency and the design of your system are all important considerations, which no doubt creates a barrier to the widescale adoption of heat pumps.
Read our complete guide to the advantages and disadvantages of heat pumps here.
Different types of heat pumps
There are three major types of heat pumps in the UK, all of which work on the same principle of moving heat through evaporation and condensation.
Let’s take a closer look at how each of them and their applications….
Air-Source Heat Pumps (ASHP)
Air Source Heat Pumps are considered the most likely candidate for the majority of residential properties in the UK, since their installation is less laborious and they do not require as much space to house. Being fully electrified they also align perfectly with the carbon neutral goals.
In terms of installation, they require a free external wall to house the unit, where the absorbed heat is fed into the property with a fan.
How do air source heat pumps work?
Air Source Heat Pumps, similar to a refrigerator, work on the principle of condensation and evaporation to extract heat from the outside air of your home.
Essentially, this means that they reverse the normal state of thermal energy, moving it in the opposite direction of normal heat flow by extracting the heat from a cold location and releasing it to a warmer one.
There are two major types of air source heat pumps: air-to-water and air-to-air systems:
Air-to-water systems
Heat the water in your wet central heating system e.g. through your radiators, underfloor heating and hot water storage cylinders.Air-to-air systems
Heat the property with fans that can also provide cooling – like air conditioning, ideal for the warmer months of the year. For this reason, heat pumps are usually described as air conditioners that can work in reverse.
Ground Source Heat Pumps (GSHP)
As their name suggests, ground source heat pumps extract air from the ground instead of the air.
Since the ground has an ambient temperature it is able to provide a much more consistent heat than the air, which can be relatively volatile. THis is one of the major advantages of GSHP.
However, in terms of installation GSHP are much more complex, requiring properties with large plots. The installation process can also be incredibly disruptive, labour intensive and expensive.
Reside in the UK and wondering if a heat pump is right for you? Check out our complete analysis where we asked - are heat pumps worth it?
How do ground source heat pumps work?
The ground surrounding the property must be trenched and a network of pipes containing refrigerant laid, this liquid then absorbs the heat which remains at a constant temperature of between 10°C and 15°C.
Once heated, the refrigerant travels to a heat exchanger within the property where it’s used to generate heating water and hot water on demand.
Hybrid Heat Pumps (HHP)
Hybrid heat pumps are seen as a more practical option in a seasonal climate like the UK, where the temperature can swing within a single day within a range of 20°C.
They are usually seen as a better option for older homes that are poorly insulated and/or have a poor thermal efficiency. In these homes, it is increasingly likely that a fully electric heat pump would struggle to meet the heating demands consistently throughout the year.
With regards to installation, a hybrid heat pump is simply the installation of both an air-source heat pump, which is an external wall hung unit and a traditional gas combi boiler.
How do hybrid heat pumps work?
The hybrid heat pump system is composed of a heat pump that works in combination with a traditional gas boiler.
The majority of heat pumps within these systems will operate at a temperature of 40 degrees C, which will provide sufficient heat for most of the year. The heat pump operates around 85% of the time and switches to the gas boiler when the external temperature plummets and the heat pump would struggle to meet the heating demands.
We believe, just like our cars, that hybrids will be the best option the start the transition to greener heating in the UK
Hybrid heat pumps are not seen as a priority over full electrification systems, especially for properties off-grid where the required gas infrastructure would be far too expensive to install.
This is also true for modern, well-insulated properties, where regular heat pumps should provide adequate heat so that a hybrid option is not required.
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