Heat Pump

How Does a Heat Pump Work?

By March 29, 2021April 24th, 2021No Comments
how does a heat pump work?

How Does a Heat Pump Work?

Everyone is familiar with air conditioning or furnaces, but did you know you have another option to cool and heat your home? A heat pump is a great alterative that cuts down on your home energy consumption. So, how does a heat pump work? How much energy does it help you save and what are the pros and cons of installing one? Read on to find out.

What is a Heat Pump?

Simply put, a heat pump is a system that transfers heat from outside to inside a building or vice versa. A heat pump essentially does all the work that the traditional air conditioning can. It can keep your house cool in summer, warm in winter, and on top of that supply hot water. Heat pumps also have an added bonus of not using any fossil fuels. In this way, they do not contribute any carbon to the environment.

How Does a Heat Pump Work?

Before we get into how heat pumps work, we need to understand what parts they are made of. The majority of heat pumps consist of a compressor, indoor and outdoor heat exchangers and expansion valves.

Let’s have a look at how the heat pump works in heating mode (Air to Air):

  1. The compressor heats up the liquid refrigerant by compressing it to high pressure, creating superheated vapour.
  2. The vapour travels to the indoor heat exchanger where it reacts with the cooler air around it.
  3. This causes the vapour to cool and condense while transferring its heat to the surrounding area. It turns into liquid. The condensed and cooler liquid is still at high pressure at this point.
  4. The liquid passes through the expansion valve to expand it to create low-pressure, low-temperature liquid. (Expand = make colder, compress = heat up)
  5. The low-pressure, low-temperature liquid travels to the outside heat exchanger where it reacts with cold air. The cold air heats up the low temperature liquid. What? You might be thinking to yourself. It is important to note that liquid refrigerants or coolants have extremely low boiling points at around -26˚C (-15˚F) or even at -49˚C (-56˚F). The cold temperature outside is still enough to turn the liquid into vapour.
  6. The low-pressure vapour travels back to the compressor to be turned into high-pressure, high-temperature vapour and the whole cycle is repeated again.
schematic diagram of how heat pumps work

Schematic diagram of how heat pumps work.

When the heat pump is in cooling mode, it works exactly the same but vice versa. This means the high-pressure, high-temperature vapour travels to the outside heat exchanger first before it gets cooled and expanded by the expansion valve.

(Note: Air to Water heat pumps work on the same principle. However, instead of heating up air, there are equipped with plate heat exchangers to heat up hot water tanks or cylinders.)

The compressor unit of the heat pump system is typically fitted outside the house. It is useful to have a sunny spot for this unit so that the pump does not have to work as hard. However, it is worth noting that the unit can absorb heat from air even at sub-zero temperatures – so it will work even if it is placed in a shade.

Uses of Heat Pumps

Since heat pumps can operate in both cooling and heating modes, there are a number of applications of these systems. Heat pumps are used for various HVAC (Heat, Ventilation, Air Conditioning) applications. In much colder countries, they can absorb heat from the air even on freezing winter days. This heat is then used to regulate temperature in a home. The reverse process happens in the summer season where the same heat pump is used to humidify and cool an indoor space.

Another use of heat pumps is to heat water in residential and commercial buildings. This hot water can meet all of the obvious requirements (hot taps, showering, bathing etc.). Heat pumps are also used to heat swimming pool water.

Advantages and Drawbacks

There are a number of key advantages of installing a heat pump but there are also some drawbacks.

Following are the key advantages of heat pumps:

  • Eco-Friendly: Heat pumps are more environmentally friendly as compared to traditional gas boilers as they contribute less CO2 to the environment.
  • Simple Installation: As opposed to other green heating solutions, heat pumps are much easier to install. Because of this, they have relatively lower installation costs.
  • Good Return on Investment: Heat pumps are eligible for renewable energy heating incentives. So, you can be sure that you will get a good return on your investment.
  • Lower Running Costs: Heat pumps cost less to run as compared with traditional gas boilers so, the energy bills are lower.

Following are some drawbacks of heat pumps:

  • Noise: Heat pump condensers are generally very noisy and they also blow out cold air. This can be annoying if you are close to the heat pump’s outside unit.
  • Electricity: Since heat pumps use electricity to run, they are not completely zero-carbon unless the electricity used to run them is generated from a renewable source, e.g. solar panels.
  • Upfront Cost: Upfront cost is arguably the biggest drawback for most individuals when buying a heat pump.

Also Read: What is LiFePo4 Battery?

Types of Heat Pumps Available on the Market

Now that you know the answer to “how does a heat pump work?” You might be interested in learning about what types are out there. There are a number of different types of heat pumps available on the market. The biggest difference between all these varieties is the look of the indoor unit or the location where they can be placed. In residential buildings, there are four types of heat pumps:

  • Air to Air Heat Pump: This is the most common type of heat pumps. It absorbs heat from outdoor air and transfers warm air through your house. This type of heat pump can be used as both a heater or air conditioner.
  • Air to Water Heat Pump: As the name suggests, this type of heat pump transfers heat into hot water tanks or hot water cylinders. Hot water can then be used around the house in taps or as central heating.
  • Geothermal Heat Pump: Geothermal heat pumps extract heat from the ground rather than air and then transfer it to your house via radiant heat flooring or forced air. This type of heat pump can also work as an air conditioner by extracting heat from your indoor air and transferring it underground or to your hot water tank.
  • Combination/Hybrid Heat Pump: As the name suggests, hybrid heat pumps use a combination of both technologies to cool or heat spaces.

Like other types of HVAC systems (Heat, Ventilation, Air Conditioning), heat pumps are available in a number of different models. These include:

  • Window Heat Pumps
  • Package Heat Pumps
  • Ductless Mini-Split Heat Pumps
  • Split System Heat Pumps

Does a Heat Pump Help Save Money?

Yes. If you heat with electricity, a heat pump can cut the amount of energy used for heating your home by up to 50%. Not to mention, the latest heat pump models also dehumidify better as compared to central HVAC systems, hence providing better cooling comfort and using less energy during summertime. However, system efficiency varies depending on the installation and models used. Furthermore, the energy efficiency of your property is also a key factor to consider when calculating the potential energy savings of a heat pump.

All heat pumps nowadays come with energy labels on them, offering information about efficiency. These labels are color coded. Red is the least efficient and dark green is the most efficient type.

Are Heat Pumps Worth the Investment?

Yes. If you currently use solid fuels, liquid gas, electricity, or oil to heat your home, then a heat pump (air or ground source) may be a great way to save money on energy bills as well as reduce your carbon footprint. Before buying a heat pump system, we highly recommend you making sure that your home is well-insulated and that you have researched your desired unit’s suitability to a large extent.