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Different Types of Heat Pumps, Understanding and Choosing the Best One for You

Find out all about the different types of heat pumps, how it works, their brief history, and even where to find efficient alternatives to traditional heating and cooling.

In recent years, heat pumps have become a popular and cost-effective way for people to keep their homes warm and reduce the cost of central heating. If you’re interested in buying a heat pump, you may wonder what type is best for you.

There are several different kinds of heat pumps available on the market today, with each one coming with its own pros and cons. When it comes to picking the right one for your home, there are a few things you need to consider before making a final decision. Let’s take a look at some of the most common types of heat pumps, as well as some examples of where and how they can be used most effectively.

The impact of burning fossil fuels for heating is becoming a huge problem that threatens the existence of humanity, which is why the alternative heating and cooling industry is booming. Heating based on cold synthesis is still a dream of the future, but heat pumps are already a promising present, replacing traditional heating and cooling.

What Are Heat Pumps?

air source heat pump outside the house

The most expensive energy is the energy needed to heat or cool the air in the house. Suppose it’s 30 degrees Celsius hot outside. In that case, we have to spend energy to lower the air temperature inside to get a cool room. Everything should be the other way around for the winter season and its temperatures.

A great option for reducing energy costs related to this energy process is to connect to a nearby place that remains warmer in winter and cooler in summer. The temperature change can be only 5-10 degrees instead of a large 15-20 degrees. Heat pumps can achieve this goal by using the temperature difference between different environments.

Consider the case – of heating in winter. The high temperature deep underground can be harnessed by a heat pump and moved into the house above ground from this source.

Electricity is still required as an external power source for the system. This is a great saving on the electricity needed to heat the air, as the temperature underground undergoes little change as it does outdoors.

How Do Heat Pumps Work?

Diagram how does a heat pump works
How does a heat pump work

Heat pumps use different kinds of energy from air, ground, or water sources to generate hot water and heating for your home. These are the main processes taking place:

Evaporation –low-temperature heat is taken from the air, ground, or water and is transferred into the circulating refrigerant. The refrigerant is boiled and vaporized. Heat can be extracted even in freezing temperatures through the concentration gradient of the refrigerant.

Compression – the low-temperature, low-pressure gas is compressed into a high-pressure gas, which causes the gas to increase in temperature.

Condensation – the high-temperature gas gives up its heat into the water or air circulating the heating system, and turns into a liquid as it condenses. This is the reverse action of stage 1.

Expansion – the high-pressure refrigerant liquid from the condenser travels through the expansion valve, which acts as a pressure differential valve (meaning high pressure and low pressure on differing sides).

This allows the refrigerant’s pressure and temperature to drop. It is now cool enough to absorb heat from the source once more.

So the system condenses the refrigerant in the pipes, which is the process of releasing heat into the first environment. The refrigerant then moves into the second environment, where it evaporates, absorbing the heat of this environment. The steam is compressed, which provides further heating due to an increase in internal pressure. The refrigerant moves back to the first environment to start the process again.

This process is commonly used in refrigerators and air conditioners.

Heat pumps are devices that are designed to absorb heat from a warmer environment and then transfer and release it to a cooler environment. These can be cooling and heating systems, and they can also be used for heating and water purification, and even sterilization.

For cooling, heat pumps can be used to harness heat from the air inside your home. This is possible by drawing cool air from outside and transferring it inside your home. This will make your home more comfortable and save you money on cooling.

Heating systems, in turn, will receive heat from the environment and transfer it inside. Therefore, heat pumps are very efficient for both heating your home in the winter and cooling it in the summer.

History (when it was invented?)

Heat pumps originated from the refrigeration process. in 1748, the first cooling process created by William Cullen was registered. In 1857, Peter von Rittinger transferred this technology to heat pumps. Then, a century later, the first large-scale reversible heat pump appeared in London, created by the Royal Festival Hall.

Due to concern for the environment and the desire for global environmental sustainability, the use of heat pumps has recently increased.

Where To Buy Heat Pumps

Heat pumps are no longer any new equipment. They can be purchased where heating and cooling systems for houses and premises are sold.

Underground or underwater systems of heat pumps are very efficient, although they need large installation work as they need to be placed underground. It also requires additional pipelines to move the refrigerant at a longer distance. Air-air systems are usually cheaper and simpler in installation, but they have less efficiency.

Types of Heat Pumps

There are several types of heat pumps, which can be conventionally divided into three groups:

  • Air source heat pumps
    • Air/Water source heat pumps
    • Air/Air source heat pumps
  • Exhaust air source heat pumps (reversible)
  • Ground source heat pumps
    • Ground Source Heat Pumps with Bore holes
    • Ground Source Heat Pumps with ground loops
    • Ground Source Heat Pumps underwater
  • Water source heat pumps
  • Hybrid
  • Other types

For a better explanation of the topic of heat pumps, we need to consider the following.

Air Source Heat Pumps

Air/Water Source Heat Pumps

Modern heat pumps outside a home in summer

Have you ever wondered how you can use air to heat your home? An air source heat pump can concentrate heat energy in the outdoor air to the extent that it can be used to heat water in showers and radiators.

Outdoor air is drawn into the heat pump and meets in a closed system. The system contains a refrigerant that turns into a gas at very low temperatures. The temperature of the gaseous refrigerant is greatly increased by the high-pressure compressor. The condenser supplies heat to the property’s heating system, while the refrigerant liquefies at the same time – ready to turn back into a gas and collect more heat energy.

Air heat pumps technology is based on a simple, famous principle – the same one used in a conventional refrigerator. Extracting thermal energy from the outside air even at low temperatures, an air source heat pump can provide your home with heating and hot water. Operating range for modern air source heat pumps could be up to 75 °C supply temperature and 65 °C at –25 °C outdoor temperature.

how air source heat pump works diagram
Image Credit NIBE

The process can also be reversed for cooling mode during the summer months.

There are systems of air heat pumps consisting of external and internal modules. They work together to create a complete climate system that is easy to install, use and maintain. Modernized Air Heat Pump systems are compatible with other energy sources, allowing the use of additional functions, such as ventilation and pool heating.

An intelligent inverter-controlled air/water heat pump could become a natural part of your connected smart home. The smart technology automatically adjusts the indoor climate and gives you full control of the system from your smartphone or tablet.

Air/Air Source Heat Pumps

Air-to-air heat pumps transfer heat from outside air to inside air in a room. They are also available as reversible systems that heat and cool the air in the room, read more about Exhaust Air Source Heat Pump. The most common systems use steam compression or hot water for radiators.

A compressor that uses vapor compression is similar to one that works in a refrigerator or an air conditioner. These include an indoor installation and connecting pipes to an outdoor above-ground installation. Reverse-cycle chillers work similarly to other air-to-air pumps, except that they circulate water instead of another evaporating refrigerant. After heating, water can pass through internal radiator systems.

Air-to-air systems and radiant systems have a higher level of energy efficiency than other heating systems. They cost less to purchase and keep running than other forms of heat pump systems because they run above ground. Air-to-air source heat pumps are more environmentally friendly and safer for health, as they do not burn carbon fuel, which can emit carbon dioxide or nitrogen oxide during combustion.

These systems are ideal for rooms in a temperate climate. They provide sufficient warmth in all but very cold weather, approaching freezing temperatures. 

The disadvantages of these systems are as follows:
  • They do not work well in climates with extreme conditions. At low temperatures, the thermal power drops below the permissible level. Most systems include oil emergency heating or some form of resistance. However, it is not economically viable and is not designed for permanent use.
  • Leaves, grass, snow, and ice can affect airflow and internal moving parts because the systems are above ground. Sometimes they need filters and defrosters.
  • Require more initial costs than other space heating solutions. Before installation, it is better to calculate how long it takes to recover the previous costs, which depend on local electricity and fuel prices. However, these systems are long-term, can last twenty years or more, and ultimately save money in the long run.

Mini Split (Ductless)

mini ductless heat pumps outside the houses

A split heat pump is an air efficient energy-saving heating and cooling system that reduces carbon dioxide emissions and is designed for small houses that do not have air ducts. They’re usually installed whenever building owners want to upgrade their heating system from one that uses gas, radiators, water heaters to one that uses air.

Ductless mini-splits use small holes cut into the side walls, while traditional air source heat pumps connect an outdoor unit to a duct system. The indoor unit can be wall, ceiling or floor mounted up to 15 meters or 50 feet from the outdoor unit.

System consist of an external module that obtain heat from the outside air which refrigerant transfers it from to indoor module. This eliminates the need for drilling coils and bore holes in the ground. Up to 4 internal units could be connected to outdoor ductless mini-split. So you will have an opportunity to control each one independently, as well as distribute heat or cool across premises as you want.

HVAC Air Conditioner Compressor and a Mini-split system side by side outside a brick home.

Modern mini-splits have a number of features:

  • Optimum annual heating coefficient thanks to the inverter controlled compressor.
  • Circulation pump with adjustable speed.
  • Built-in clock for extra hot water scheduling and supply line temperature decrease/increase.
  • Prepared to control two climate systems.
  • Built-in water heater coil.
  • Built-in active cooling function.
  • Ability to connect external heat sources.
  • Optimized operating costs. Compressor speed regulated according to demand.
  • Compact dimensions of the external unit.

Мini-splits tend to be energy-efficient and budget heat pump along others.

Exhaust Air Source heat Pumps

Exhaust air heat pumps first work to ventilate your home and then recover the thermal energy of the vented air to heat water and the heating system. Reversible heat pump reuse energy from the old used air of the whole house. Types of houses

To put it simply, exhaust air heat pumps remove air from damp or cold spaces in your home. Slight negative pressure is then created to circulate air from other parts of the house where it is needed. At the same time, new outside air is drawn in through valves on the outside walls, providing full ventilation to all rooms in the house. Finally, the circulating air is drawn through the house’s duct system, and the heated room air is directed to the heat pump, where energy from the air is recovered. This process allows the heat pump to provide the entire house with hot water and heat.

how is working an exhaust air heat pump diagram
Image Credit NIBE

Exhaust air heat pumps are a compact and efficient solution for new build flats, apartments, and smaller properties. By using renewable energy sources, you reduce your energy costs and protect the environment.

Modern exhaust air heat pumps have these advantages:
  • high seasonal performance
  • low operating costs for both new builds and replacement
  • low noise level
  • stylish design
  • compact size make it easy to put in place and install
  • integrated wireless connection with energy-saving smart technology for a high level of comfort.

Ground Source Heat Pumps

The heat from the soil is pure solar energy stored in the ground and at the bottom of lakes. It starts on the surface when the sun shines stronger in the spring and then persists deeper in the ground when the weather gets warmer. With the help of a ground-source heating system, you can create a pleasant indoor climate and provide your home with both heating and hot water, as well as cooling on hot summer days.

The use of renewable energy sources reduces energy costs and at the same time protects the environment from CO2 emissions. A ground source heat pump type extracts heat from solar energy stored in the ground using either buried collectors or holes drilled deep into the ground. With the help of a mixture of water and environmentally friendly antifreeze, which circulates in a sealed circuit, thermal energy is extracted from the ground and transferred to the heat pump.

This category of pumps is more efficient than an air system because the temperature deep underground and underwater does not differ as much as in the open air. A geothermal heat pump can save you up to 75 percent of the energy you buy. The only energy you pay for is the electricity that runs it.

Liquid-filled loop, also known as a collector, can collect solar heat stored deep in the ground, at the bottom of a lake, or a few meters beneath your lawn. The type of ground source heat pump that suits your needs will depend on the energy needs of your home, your heating system, and the nature of your property.

Ground Source Heat Pumps Bore holes

To access energy in the bedrock or deep underground, if you have a small piece of land, you need to drill a borehole, which is usually between 90 and 200 meters deep. The further north you go, the deeper you have to drill. A collector hose with liquid is lowered into the borehole, which is heated by the rock or ground and then pumped into the house.

The heat is extracted using advanced compressor technology and channeled into the home’s heating and hot water system before the fluid is pumped back into the bedrock or ground to absorb new heat.

Ground Source Heat Pumps Bore holes
Image Credit NIBE

The installation of this system will be a more expensive initially but can give you an energy saving of up to 75%. There are numerous advantages of geothermal energy heating:

  • Low energy consumption. You can reduce your energy consumption by up to 75% if, for example, you have direct-acting electricity today.
  • Low operating costs. A geothermal heat pump provides 4 times as much energy as it consumes. That is, it uses 1 part of energy to extract 4 parts of energy from the groundwater.
  • Long lifespan. Its heat pump normally has a lifespan of approx. 15-20 years and the borehole approx. 50 years.
  • Profitable investment. It pays off after just a few years for most people. The greater the energy consumption, the more profitable.
  • Environmentally friendly energy source. Large proportion of renewable energy used and produces a very small CO2 footprint.
  • Stable form of heating. The effect of geothermal heating is relatively constant regardless of the season.
  • Predictable heating costs. Less risk of large invoices during cold winters and less exposure to electricity price fluctuations.
  • High operational reliability. ROT deduction You may make a tax deduction for 30% of the labor cost.
  • Cooling. With a simple accessory, could also produce coolness in the summer in a very cost-effective way.
  • Easy maintenance when it was properly installed.

Ground Source Heat Pumps ground loops

Ground heating within loops under lawn uses the same principle for extracting the heat; the only difference is that you lay a collector hose at a depth of 1 meter instead of drilling a hole at a depth of approx. 90-200 meters. Like Underwater heat pumps, they often use water as a refrigerant and generally do not require a condensation/evaporation process, although such options also exist.

Ground Source Heat Pumps ground loops
Image Credit NIBE

Water refrigerant is used in a network of pipes deep underground. Closed water in the pipes absorbs the temperature of the environment and then gives it to the upper structure to absorb or release heat into it.

Underground pipes have several configurations. Pipes can be laid in vertical loops, where horizontal space is limited, and a number of deep holes are drilled in the ground. The pipes form a chain of deep vertical U-shaped shapes. The holes can be filled with groundwater or another medium for better temperature exchange.

For places with a larger area, pipes are arranged in a horizontal U-shaped network. It is laid in one plane below the freezing point, with the soil excavated and then replaced or backfilled to cover the pipes.

Advantages of Ground Source Heat Pumps ground loops:
  • Cheaper installation than geothermal heating with boreholes
  • Environmentally friendly and maintenance-free
  • Provides great financial savings

Disadvantages – burying ground hose can mean a major intervention that requires the garden to be restored. The length of the ground hose is normally approx. 90-200 meters.

Ground Source Heat Pumps Underwater

Underwater ground source heat pumps use solar energy stored at the bottom of a lake that you can use to heat your house. It is an alternative to ground heat, the difference is that you place a collector hose on the bottom of the lake instead of under the lawn or deep in the rock or ground.

Ground Source Heat Pumps underwater
Image Credit NIBE

Submersible heat pumps can be used for structures located close enough to deep water sources. Water-based heat pumps work on a similar principle to air-based heat pumps but use water as a medium for heat exchange. They absorb heat and release it into the water to cool.

Because the temperature deep underwater is relatively stable throughout the year, this system is perfect for use in more extreme climates. This is an advantage over aerial systems serving only temperate climates, but requires higher initial costs than aerial mechanisms and, at the same time, less than underground ones.

  • Cheaper installation than geothermal heating with boreholes
  • Comfortable, environmentally friendly, and maintenance-free
  • Provides great financial savings

The biggest disadvantage of submersible heat pumps is the requirement to be very close to a water source. Although outdoor wells can work, however larger reservoirs of free-flowing water will be more effective.

In open systems of deepwater heat pumps, ordinary water collects from the environment into the system and moves through the internal structure, so there is an additional risk of mineral deposits forming within the line. This can impede the flow of water and reduce the efficiency of the system.

Luckily, most underwater systems are closed. Like the other, closed-loop circuits move the refrigerant through a closed pipeline.

Hybrid Heat Pumps

A House with Solar Panel on the Roof Hybrid Type Heat Pump

The most important task of a clean heat pump is to provide sufficient heating in very cold climates. If the air temperature is as low as freezing temperatures or below, the air-to-air pumps cannot operate consistently. This forces the system to use emergency heating for extreme cold, which is an expensive solution.

To reduce the impact on systems in extreme conditions, hybrid heat pumps can be used, which use a heat pump together with another heat source. Such a source can be modern solar panels or traditional fossil fuels.

With solar power, you become a micro-producer of green electricity from a sustainable energy source and contribute to improving the environment by making a good investment without worrying about rising electricity prices.

Solar energy and heat pumps are the best combinations that give you a high return on your energy system. In most cases, the heat pump’s energy consumption is halved or even neutralized. With an efficient heat pump control system and intelligent communication, the heat pump can adapt to the free solar electricity generated by your solar panels.

An intelligent inverter-controlled air/water heat pump becomes a natural part of your connected home. The smart technology can automatically adjust the indoor climate and gives you full control of the system from your smartphone or tablet.

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What temperatures do heat pumps produce?

Modern heat pumps could supply indoor temperature up to 75 °C (167 °F) , the maximum temperature become a bit lower 65 °C (149 °F) if it is very cold outside –25 °C (-13 °F).

What is the most efficient temperature for a heat pump?

Modern heat pumps do operate efficiently even if temperatures drops a lot. However, the optimal working phase is with an outdoor temperature above 5 C°C or 40 degrees Fahrenheit. Once the outdoor temperature drops below, heat pumps consume more electricity, which is why efficiency drops.

How does a heat pump work in heating mode?

The refrigerant flowing through the heat exchanger transfers a large amount of heat energy to the indoor air, i.e., the indoor air is heated. The temperature of the refrigerant decreases, and the state changes from a gas to a liquid as it flows through the heat exchanger.

Are heat pumps gas or electric?

Air/air heat pumps are most often installed as a supplementary heat source for houses with direct-acting electricity because it is a reasonable installation cost, and little intervention is required in the house for its installation.

How does a ground source heat pump work?

In the borehole, you lower a collector hose with liquid that is heated by the rock and then pumped up to the house. The geothermal heat pump extracts the heat with the help of advanced compressor technology and sends it out to the house’s heating and hot water system, then the liquid is pumped back into the bedrock for new heating.

What temperature does a heat pump work down to?

The colder it gets, the more energy and electricity the air source heat pump uses to heat the air. Most heat pumps operate down to -20 °C (-4 °F), newest ones – are down even to -25 °C (-13 °F), but at such low temperatures, the COP value will approach 1 – that is, the heat pump consumes as much energy as it generates. For the ground source heat pump, it almost doesn’t matter what the air temperature is outside as it draw energy from the bedrock, ground, and underwater where the temperature is more stable all year round.

How does the heat pump work in cooling mode?

Heat pumps transfer heat by moving a refrigerant through a cycle of heating and cooling. In the cooling mode, the refrigerant absorbs heat from the building and transfers it to the air or ground outside.

What is the average life expectancy of a heat pump?

Lifespan differs from the type of heat pump, normally it has a lifespan of approx. 15-20 years, and the borehole ground source heat pump approx. 50 years.

What temperature does a heat pump stop working at?

Air source heat pumps usually work down to a temperature of about 20 degrees below zero (-4 °F), although with lower efficiency. However, this may vary depending on the manufacturer and model, as flagman brands had till -25 °C working temperature (-13 °F).

Can you use heat pumps in cold climates?

Definitely. Ground source heat pumps were made for cold climates, as they are almost independent of outdoor temperature. Air source heat pumps usually work down to a temperature of about 20-25 degrees below zero (-4 and -13 °F), although with lower efficiency. However, there are many cases where they have worked very well in significantly colder temperatures, even down to -35 degrees in test environments (-31 °F).

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