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High capacity heat pumps: a game changer for decarbonising the heating sector

In the course of the energy transition, heat pumps are becoming the standard for heat supply in private homes and especially in new buildings. They are installed as a decentralised supply solution in the consumer's own front garden or basement. 
High capacity heat pumps are a lesser-known variant. They are used for economical and emission-free heating and cooling in municipal infrastructure, industry and large residential, commercial and business buildings and are installed centrally.

 

In this blog post you will learn more about 

Definition of high capacity heat pumps:
Heat pumps with outputs greater than around 50 kW are often referred to as high-capacity heat pumps (industrial heat pumps). They can also achieve outputs of well over 100 kW and, with the usual series connection, can reach the MW range.

Distribution and chances

High capacity heat pumps for providing heat for industrial plants and buildings are still a rarity in Germany - and the trend is rising. This is because they can play a decisive role in the decarbonisation of the heating sector and in achieving climate targets. A Fraunhofer study commissioned by Agora Energiewende even states: "The entire German demand for heat up to 200 degrees Celsius can technically be met entirely by heat pumps. High capacity heat pumps with an output of 500 kW or more play a particularly important role in this." This could save three quarters of Germany's natural gas consumption - and, in purely mathematical terms, cover the entire demand for building heating and hot water as well as a good third of industrial process heat.

However, only 100 MW are currently installed in Germany, with a further 600 MW under construction or in planning[1]. In order to become climate-neutral by 2045, an annual thermal capacity of four GW would have to be added.

 


[1]https://www.heise.de/hintergrund/Studie-Grosswaermepumpen-koennen-drei-Viertel-des-deutschen-Gasverbrauchs-sparen-9187670.html

 

Requirements for and possible applications of high capacity heat pumps

To operate a high-capacity heat pump, an abundant heat source is required. The heat can come from air, earth, river or lake water, industrial waste heat or waste water. In contrast to a network with decentralised, normal heat pumps, for example in a neighbourhood of detached houses, the corresponding distribution network runs at a higher temperature level. This is because very large heat pumps (HPs) in the MW range are always located at the source: as a result, the network itself has a higher temperature, which may already be able to cover a large part of the heat demand. A booster HP can then be placed there for certain processes, which reduces heat losses in the distribution network and thus increases the overall efficiency of the network. In contrast, networks with small, decentralised heat pumps, which are located in every house, generally have the temperature level of the heat source - i.e. it is cold. 

High-capacity heat pumps are particularly useful where there is a need for both heating and cooling, because like its little brother, the large heat pump can do both. They are ideally suited for combination with district heating networks, horticulture and agriculture, swimming pools, office buildings, hotels, hospitals, supermarkets and catering.

These applications usually have a high demand for heating and cooling and can benefit in particular from lower energy costs for heating and cooling. A business case can be made if there is a year-round demand for low-temperature heating and cooling, which is controlled fully automatically and monitored by smart meters. Then the investment costs in a large heat pump solution will soon have been amortised.

How does a high capacity heat pump work?

A high-capacity heat pump works in exactly the same way as its smaller brother: heat is extracted from a renewable source and transferred to a refrigerant, which transfers the heat to a carrier medium at a higher temperature level via a heat exchanger. This can be water, for example, which is used to provide heat. The temperature transfer causes the refrigerant to liquefy again and is expanded before the process starts again. For cooling, the cycle is simply reversed and heat is extracted from the building, transferred to the refrigerant and then returned to the original heat source using the heat exchanger. 
In this cycle, additional energy in the form of electricity (ideally from renewable sources such as photovoltaics) is largely only required for compression and expansion; the remaining energy is obtained from the respective heat sources (e.g. ground or aquathermal). There are also more and more direct evaporator systems, especially for high-capacity heat pumps, which are complicated to control but can save a lot of additional electricity and thus increase efficiency.
We have described in this blog post how the efficiency of a heat pump is represented by the seasonal performance factor and coefficient of performance (COP). However, the COP tends to be higher if the temperature difference between the source and consumer is lower.
High-capacity heat pumps often consist of several cascaded heat pumps in order to minimise the necessary heat loss.

Increasing efficiency by combining a high-capacity heat pump with a heat storage tank

As the heat pump output is more expensive than a gas boiler, for example, it is generally worth installing larger heat buffer storage tanks. The stored heat allows load peaks and fluctuations in source availability to be (partially) absorbed cost-effectively. The same also applies to self-generated electricity, for example from PV or wind. The aim here is always to consume the self-generated electricity as much as possible in order to operate as cost-effectively as possible and not to have to purchase the electricity at high cost and feed it into the grid at minimum prices. 
In addition to the advantages of a more efficient energy concept (the combination of heating and cooling by means of heat recovery as a heat pump source in combination with self-generated renewable electricity and storage reduces the dependency on external producers as well as the overall energy requirement and thus saves operating costs.

High-capacity heat pumps in practice: application examples

Unlike in Germany, high-capacity heat pumps are already widespread in Scandinavia. On the west coast of Denmark, the Esbjerg project, one of the world's largest heat pumps, will soon be supplying around 100,000 people. And Austria is also attracting attention with a special project in Vienna: the high-capacity heat pump currently under construction at the Ebswien wastewater treatment plant uses the wastewater and is set to become the most powerful high-capacity heat pump in Europe - and will supply up to 112,000 Viennese households with district heating from 2027.

Example: Use of large-scale HP in an office building

Due to the warmer summers, the cooling of office buildings is also becoming increasingly necessary here. In new buildings, this is often done using concrete core activation or cooling ceilings. Water-led surface systems have the advantage that they manage with low heating and cooling temperatures and therefore enable very efficient use of heat pumps. Geothermal energy, groundwater or waste water can then be used as a source for passive air conditioning in summer and for heating in winter. In summer, the heat from the building is fed back into the ground and serves to regenerate the geothermal storage probes or as seasonal geothermal energy storage. The more balanced the energy extraction balance between winter and summer operation, the more sustainable the natural energy source is available. This is because the source regenerates more quickly by releasing the waste heat from the cooling phase.
The dual use of the underground also leads to high utilisation of the industrial heat pump and therefore to lower overall production costs and a better CO2 balance.

Example: Use of large heat pumps in district heating networks

High-capacity heat pumps are also increasingly being used in projects to create and transform district heating networks. 
goodmen energy has already been able to advise a number of local authorities on this and has, for example, planned the decarbonisation of a network that is fed from wastewater and river water and activated by a high-capacity heat pump. Waste heat from process exhaust air and process water can also be recovered on a large scale in industry using high-capacity heat pumps. The high temperatures ensure that the heat pumps are highly efficient. Due to the resulting reduction in heat demand (to a COP 3-4), funding opportunities and, in some cases, possible operating subsidies and the rising price of CO2, the investments are already amortising within a reasonable time frame in many cases.

Example: Use in outdoor and indoor swimming pools - Stuttgart

Indoor swimming pools generate large amounts of waste heat, which is often released unused into the environment. With an exhaust air high-capacity heat pump, it is possible to recover this waste heat in a targeted manner, recycle it and thus reduce the overall heat requirement. A fan integrated into the exhaust air heat pump draws in the heated air from the indoor pool, uses it as a heat source for the heat pump unit and discharges the cooled air to the outside. By utilising this waste heat, both primary energy consumption and CO2 emissions can be reduced. 
In our feasibility studies for Stuttgart's swimming pools (indoor, outdoor, thermal and river pools), we have also designed with corresponding high-capacity heat pumps and the utilisation of waste heat, hot water, thermal springs and river water.

Example: Floating energy centre with large-scale HP in Prague

The launch of another remarkable project took place in Prague at the beginning of December 2023: As a partner of the Czech project developer JN infra AS, goodmen energy is planning floating energy centres, known as ComPons, as well as the associated heating networks on land. The pontoons are equipped inside with high-capacity heat pumps fed by river water, which are attached to the shore. They are designed to supply heat energy to urban neighbourhoods near navigable rivers (read press release in German here).

Financing and promotion of high-capacity heat pump systems in Germany

Under certain circumstances and provided that the connected heating network system is used to supply more than 16 buildings or more than 100 residential units, high-capacity heat pumps can be subsidised in modules 1-4 via the federal subsidy for efficient heating networks (BEW). The operating cost subsidy in module 4, i.e. the subsidisation of the heat pump electricity, is particularly attractive for operators. The requirements and conditions for this are extensive and must be assessed separately for each case. Individual subsidy counselling is essential here.

There is also the option of funding via the KfW "Renewable Energies - Premium" programme. This programme

Heating and cooling networks that are fed from renewable energies
large heat storage tanks in heating or cooling networks
large efficient heat pumps in heating or cooling networks
are subsidised with loans of up to 25 million euros from 0.58% effective annual interest.

 

Conclusion

By utilising renewable energy sources such as air, water or geothermal energy, high-capacity heat pumps enable a sustainable heat supply in industrial, commercial and municipal facilities. Their scalability, high performance and ability to effectively utilise even low-temperature heat sources make them a sustainable choice for reducing CO2 emissions and promoting environmentally friendly heat generation on a large scale.