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Brine, air, water: Heat pump technology explained

Differences and functions of heat pumps

Patricia Rieth

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Heat pump typesAll heat pumps work in a similar way, using electricity to harness free ambient energy. Bosch offers a wide range of heat pumps that are particularly efficient depending on the application.

These include
a) air- to-water heat pumps,
b) split air conditioners
(air-to-air heat pumps),
c) brine-to-water heat pumps and
d) water-to-water heat pumps.
Use as hybrid systems
Many Bosch heat pumps can be combined with another heat generator such as a gas condensing boiler if required. These hybrid heat pumps are particularly suitable for existing buildings and are particularly efficient thanks to intelligent control that ensures the most appropriate heat generator is used at all times.

Absorption, compression, release, decompression
The operating principle of heat pumps*

Energy absorptionThe ambient air contained in the energy sources air, water, and earth is used to heat a refrigerant. The refrigerant absorbs the ambient air and gradually evaporates.
Compression
The heated refrigerant is compressed by an electrically powered compressor, which heats up further, increasing the pressure.
Release
When the desired temperature is reached, a heat exchanger transfers it to the heating water.
Decompression
After the heat is released, the refrigerant is still under high pressure. The refrigerant is passed through an expansion valve and the process is repeated.

*The operating principle applies to all heat pumps except air-to-air heat pumps (air conditioners). The latter distribute the heat to the rooms via the air rather than via a hot water circuit.

Air-to-water heat pumps

Using ambient air with little effort Air-to-water heat pumps from Bosch extract heat from the ambient air. They are suitable for both new and existing buildings and reliably meet the heating and/or hot water requirements of single or multi-family houses.
The refrigerator principleAn air-to-water heat pump works according on the same principle as a refrigerator – only in reverse. In the air-to-water heat pump, the outside air is drawn in by an integrated fan and meets a refrigerant that evaporates. The air-to-water heat pump uses one kilowatt hour of electricity to produce many times that amount of thermal energy. In this way, new and renovated buildings can be fully heated all year round and hot water can be reliably provided without the need for an additional heating system.
Split and monobloc heat pumpsIn monobloc heat pumps the technical components for heat generation are located within one unit. In split heat pumps the process takes place in two separate units. Both systems work on the same principle, only the construction is different. Air-to-water heat pumps can not only provide heat, but also provide efficient cooling in summer.

Split air conditioners (air-to-air heat pumps)

Using the ambient air as an energy sourceA split air conditioner uses energy from the ambient air, i.e. that it cools and heats a building without radiators.
Operating principle of split air conditionersSplit air conditioners extract energy from the environment and transport it to the place where it is needed, e.g. the living room. The term air source heat pump covers both split air conditioners (air-to-air heat pumps) and air-to-water heat pumps. Both extract heat from the surrounding air.
Especially efficient when combined with heat recovery ventilationUnlike air-to-water heat pumps, air-to-air heat pumps do not transfer the heat to the rooms via a hot water circuit, but via the air. Heating systems with air-to-air heat pumps are therefore also called ventilation heating systems; they do not require radiators or heating surfaces. Air-to-air heat pumps can be part of a heat recovery ventilation system. In this case, the hot exhaust air is used as an energy source. In reverse mode, some air-to-air heat pumps can also cool.

Brine-to-water heat pumps

Extracting heat from the groundThese heat pumps are called brine-to-water heat pumps because a heat transfer fluid (brine) taps the earth as an energy source. As the heat is extracted from inside the earth, these systems are also known as geothermal heat pumps or geothermal heating systems. The visual advantage is that there is no need for external heat generating equipment.
Heat from a probe borehole a or a surface collectorIn brine-to-water heat pumps, the brine circuit extracts the heat from the ground. This requires probe boreholes or surface collectors in which the brine circulates. The water/salt mixture is a good heat transfer medium and is environmentally harmless. At the heat pump's evaporator, the energy from the brine is transferred to the refrigerant circuit. A compressor compresses the refrigerant, causing its temperature to rise.
Efficient and economical cooling possible in summerA major advantage of brine-to-water heat pumps is that they can be used for cooling in the summer. In ‘reverse mode’ the system dissipates heat into the cool ground. The temperature gradient eliminates the need for compression. The result is efficient and economical air conditioning that regenerates the ground through heat dissipation.

Water-to-water heat pumps

Efficient thermal energy from the groundwater A water-to-water heat pump – or groundwater heat pump – extracts thermal energy from groundwater by means of two wells. The thermal energy can then be used for heating or hot water generation. Water-to-water heat pumps are very efficient.
Using the underground groundwater reservoir
High heat output thanks to constant groundwater temperature
While air source heat pumps draw in the ambient air via fans, and geothermal heat pumps use the earth’s heat via probes or surface collectors, water-to-water heat pumps make use of the underground groundwater reservoir. The temperature of the groundwater is largely constant throughout the year, so the heat pump provides high heating output in both summer and winter. Water-to-water heat pumps can achieve efficiencies of around 500%, which corresponds to a seasonal coefficient of performance (SCOP) of 5.
Using two wells In a water-to-water heat pump, the suction well sucks in the groundwater to extract heat, while the injection well returns the used cold water to the ground.

Press kit Bosch Heat pumps

About Bosch

The Bosch Group is a leading global supplier of technology and services. It employs roughly 429,000 associates worldwide (as of December 31, 2023). The company generated sales of 91.6 billion euros in 2023. Its operations are divided into four business sectors: Mobility, Industrial Technology, Consumer Goods, and Energy and Building Technology. With its business activities, the company aims to use technology to help shape universal trends such as automation, electrification, digitalization, connectivity, and an orientation to sustainability. In this context, Bosch’s broad diversification across regions and industries strengthens its innovativeness and robustness. Bosch uses its proven expertise in sensor technology, software, and services to offer customers cross-domain solutions from a single source. It also applies its expertise in connectivity and artificial intelligence in order to develop and manufacture user-friendly, sustainable products. With technology that is “Invented for life,” Bosch wants to help improve quality of life and conserve natural resources. The Bosch Group comprises Robert Bosch GmbH and its roughly 470 subsidiary and regional companies in over 60 countries. Including sales and service partners, Bosch’s global manufacturing, engineering, and sales network covers nearly every country in the world. Bosch’s innovative strength is key to the company’s further development. At 136 locations across the globe, Bosch employs some 90,000 associates in research and development, of which nearly 48,000 are software engineers.

The company was set up in Stuttgart in 1886 by Robert Bosch (1861–1942) as “Workshop for Precision Mechanics and Electrical Engineering.” The special ownership structure of Robert Bosch GmbH guarantees the entrepreneurial freedom of the Bosch Group, making it possible for the company to plan over the long term and to undertake significant upfront investments in the safeguarding of its future. Ninety-four percent of the share capital of Robert Bosch GmbH is held by Robert Bosch Stiftung GmbH, a charitable foundation. The remaining shares are held by Robert Bosch GmbH and by a corporation owned by the Bosch family. The majority of voting rights are held by Robert Bosch Industrietreuhand KG. It is entrusted with the task of safeguarding the company’s long-term existence and in particular its financial independence – in line with the mission handed down in the will of the company’s founder, Robert Bosch.

Additional information is available online at www.bosch.com, www.iot.bosch.com, www.bosch-press.com.

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