Heat pumps are the only heating systems that provide heat without a direct combustion process.
Their function according to the heat exchanger principle corresponds to that of a refrigerator with the reverse mode of action. Either geothermal energy (geothermal energy), hydrothermal energy (water heat) or aerothermal energy (air heat) serves as a heat source. A collector (evaporator) extracts energy from the respective medium by cooling it down through a physical process. The energy generated is then supplied as heat to the building's heating system. The functionality of the heat pump machine is always the same, only the type and design of the collector distinguishes the individual systems. The selection of the right system depends heavily on the local conditions. Heat pumps have been a proven technology for years, both in new buildings and in the renovation of buildings.
Heat pump technology is based on the same principle of operation as a refrigerator, only in reverse. Both make use of the Joule-Thomson effect. This describes the physical process of a gas changing its temperature by changing the pressure conditions without having to supply energy. By compressing a gas, its temperature rises, by decompression it sings. Accordingly, the heart of a heat pump is the so-called compressor, which increases the temperature of the gaseous working medium through compression. In addition to the actual heat pump, a collector is also necessary that can extract energy from another medium, such as air, water or soil. In the refrigerator, this is the wire coil on the back, the condenser, which supplies energy to the ambient air in the form of heat. To operate the heat pump and especially the compressor, the supply of energy is necessary, e.g. as electricity. The less energy is required for operation, the higher the so-called annual performance factor, i.e. the efficiency of a heat pump. The principle applies to all heat pumps: the higher the temperature of the medium, the higher the efficiency of the system.
In addition to electricity, natural gas can also be used as an energy source, but the topic of this bauwion knowledge page is exclusively electrically operated heat pumps.
Functionality in the scheme:
Seal of approval: Heat pumps can be awarded the EHPA seal of approval (formerly DACH seal of approval). This is awarded by the European Heat P ump Association if the audited plant meets uniformly introduced standards. During the tests, technical values such as minimum efficiency, operating limits or noise emissions are examined, as well as the manufacturer's specifications, service and spare parts safety and the quality of the planning documents. The basis of the tests is DIN EN 14511 in particular.
Installation location: Thanks to the use of so-called scroll compressors, modern brine and water heat pumps are very quiet, and the emission noise is comparable to that of a refrigerator. An electrically operated heat pump can therefore also be located in subordinate living areas, such as the washroom or storage room. A location in the immediate vicinity of bedrooms, on the other hand, is not advisable. On the other hand, air source heat pumps can reach a noise level that can be perceived as annoying, depending on their output. The choice of the right installation location, especially the collector in the form of the fan, therefore requires increased attention. Detailed research results, recommendations for action and a ►"sound calculator" are provided by the German Heat Pump Association.
Heating system: Heat pumps work most effectively when they need to generate low flow temperatures. The optimal flow temperatures are max. approx. 30° to 35°C. For this reason, heat pumps should primarily be combined with low-temperature heating systems such as underfloor or wall heating. Although modern heat pumps also provide higher flow temperatures for convectors, for example, they are then less effective and consume more electrical drive energy in relative terms.
Cooling: Heat pumps are also suitable for cooling the temperature of buildings in summer. In this process, the process process in the device is reversed and the heat is "pumped" out of the building into the surrounding area. The type of collector is decisive here. While an air-source heat pump is unsuitable due to the high ambient temperature at the same time, the groundwater heat pump can fall back on the always cool groundwater and cause a significant cooling effect for the interiors. The limiting factor is usually the type of transmission surfaces. If the "cold" is to be emitted via the floor heating, for example, a sensor must be used to ensure that condensation does not occur in the floor structure due to the low flow temperature. In this respect, heat pumps can never replace air conditioning systems or provide comparable performance. A distinction is made between active and passive cooling with heat pumps, see encyclopedia articles ► Heat pump, active cooling and ► Heat pump, passive cooling.
Renewable Energy Heat Act: The EEWärmeG stipulates that newly constructed buildings with > 50 m² of usable space must cover part of their total energy consumption (heating and cooling) with renewable energies. The aim is to increase the share of renewable energies in final energy consumption to 14% by 2020 in the sense of a climate-friendly energy industry. This Act shall be deemed to be fulfilled only if the share of the use of environmental and geothermal energy (heat pump technology) is at least 50%. In the case of fundamentally renovated public buildings, this proportion must be 15%. A replacement measure, such as an additional solar system, is therefore not necessary when heat pumps are used as heating systems, if the technical conditions according to the "Requirements for the Use of Renewable Energies" system of the EEWärmeG are also met.
funding: The installation of heat pumps can be subsidised by the BAFA (Federal Office of Economics and Export Control) for installation in existing buildings if the relevant funding requirements are met. In addition to this so-called basic subsidy, BAFA also offers innovation and additional funding for heat pump systems with a high annual performance factor or improved system efficiency according to the BAFA criteria. This additional funding can also be applied for for new buildings, provided that both criteria, a high annual performance factor and improved system efficiency according to the BAFA criteria, are met.
The exact requirements and funding rates of the individual systems can be found on the website of the ►BAFA.
KfW funding: The KfW development bank promotes the installation of heat pumps in existing buildings through low-interest loans, but also through investment grants. Funding is available to private individuals who renovate living space to make it more energy-efficient or buy renovated housing. For this purpose, various programs can be chosen with a wide variety of requirements and funding conditions. The common basis for all programmes is that only renovation and not new construction is funded and that a significant improvement from an environmental energy point of view is associated with the renewal. Further information on funding can be found on the website of the ► KfW Bank.
Electricity tariff and shut-off periods: Drive electricity is required to operate heat pumps, which is billed by most electrical supply companies (EVU) with a separate, significantly lower heating tariff, so that the systems can currently be operated very economically. The utility company provides its own electricity meter for this purpose. However, this is usually associated with a so-called blocking period, during which the utility temporarily does not supply the heat pumps with electricity in order to relieve consumption peaks, i.e. the system does not supply heat. This closing time may not exceed 3 times 2 hours per day. Since this failure has to be bridged, it should be possible to store at least the amount of heat required during this time in a buffer tank. The operation of underfloor heating systems also leads to a buffering of downtime due to the inertia and storage mass of the screed, so that no comfort restrictions are noticeable with appropriate dimensions. When planning a heat pump system, the individual closure times must therefore be taken into account. Otherwise, the electric heating element would bridge the missing power, which would significantly increase electricity consumption.
Maintenance: Heat pumps, like all technical systems, must be maintained regularly. However, since there is no combustion, the frequency and cost of maintenance work is rather low.
DIN EN 14511-1, Air Conditioners, Liquid Chillers and Heat Pumps with Electrically Driven Compressors for Space Heating and Cooling - Part 1: Terms and Classification
DIN EN 14511-4, Air Conditioners, Liquid Chillers and Heat Pumps with Electrically Driven Compressors for Space Heating and Cooling - Part 4: Operating Requirements, Marking and Guidance
VDI Guideline: VDI 4640 Part 1: Corrigendum Thermal Use of the Subsoil - Basics, Permits, Environmental Aspects, Corrigendum to the Guideline VDI 4640 Sheet 1:2010-06
► Guide to Geothermal Probes in Bavaria, Bundesverband WärmePumpe (BWP) e.V. (pdf)
► Guidelines for the geothermal use of near-surface subsoil, geothermal heat collectors – geothermal probes Recommendations for planners, engineers and building owners, State Office for Agriculture, Environment and Rural Areas, Schleswig-Holstein (pdf)
► EEWärmeG Renewable Energy Heat Act (pdf)
► JAZ calculator of the German Heat Pump Association.
Source: bauwion
