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• Absorber
  A component which can absorb environmental thermal energy and radiation and pass them on to a heat transfer fluid. The absorber is also the key part of a solar collector used for hot water production.
• Air-to-water heat pump
  A heat pump which draws energy from the surrounding air (inside or outside a house) and transfers it to water for heating or hot water.
• Annual coefficient of performance
  The annual coefficient of performance is a key criterion in assessing heat pump efficiency. It specifies the ratio between the annual heat used to heat rooms and water in kWh and the electrical power required to produce this in kWh. It would be more useful to know the annual coefficient of performance than the energy efficiency ratio (EER) that is given in brochures, but the annual COP can only be determined during operation.
• Annual heating costs
  The total amount of all costs of a heating system that arise during the course of a year. These include fuel costs, costs for electricity, chimney sweeps, maintenance, utilities, as well as proportional investment costs for upkeep, interest payments and amortisation.

B  (back) 

• Brine
  Brine or solar fluid is a water and antifreeze solution, which is used as a heat transfer fluid in heat pump or solar heat systems.
• Buffer store
  Stores heating water in heating systems. It is used to improve efficiency and combustion, to cover electricity off-times in heat pumps and to store accumulated heat temporarily. Buffer stores can be run without pressure or with heating system primary pressure.

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• Circulating pump
  An electrically powered pump used to transport heating water, brine or solar fluid. The electrical energy consumed by a circulating pump must not be underestimated, particularly because pumps are often oversized (connected load). A hydraulic comparison is needed to determine the ideal pump.
• CO2
  The chemical symbol for carbon dioxide.
• CO2 ground probe
  A probe which draws energy from the ground in a self-circulating cycle.
• CO2 heat exchanger
  Transfers energy from a CO2 carrier medium to a working fluid.
• Coefficient of performance (beta)
  The COP of a heat pump changes constantly when the pump is running. To valuate a heat pump system, an entire heating period can be looked at and the heat output compared to the electrical energy input. If the COP is calculated for a period of one year, it is referred to as the annual coefficient of performance.
  Coefficient of performance = heat output in kWh/electrical energy input in kWh.
• Compressor
  Part of a heat pump or a machine that compresses gas. In heat pumps, the working fluid is compressed to raise the temperature. An air pump is a simple compressor which produces a noticeable increase in temperature by compression.
• COP (coefficient of performance)
  The ratio between the heat output and the power input. This changes constantly when a pump is running.
  
  COP of a heat pump= QH/(Pel + Pdv)
  
  QH: heat output of a heat pump
  Pel: electrical power used by the compressor
  Pdv: energy needed to overcome the theoretical hydraulic resistance of the heat exchangers, calculated from the volume flow * difference in pressure between the inflow/outflow of the heat exchanger

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• D-A-CH Gütesiegel (seal of quality)
  On 3 May 1999, the heat pump seal of quality came into force in Germany, Austria and Switzerland. This is a joint project by the three countries and a union of the following organisations: Fördergemeinschaft Wärmepumpen Schweiz (FWS), Initiativkreis Wärmepumpe e.V. Deutschland (IWP) and Leistungsgemeinschaft Wärmepumpen Österreich (LGW). Our heat pumps all have the seal of quality, unless they are property-specific systems or custom products.
• Direct evaporation
  A process of absorbing environmental energy for use in heat pumps. A refrigerant with a very low boiling point circulates in the absorber and evaporates when heat is absorbed. When the heat is output in the heat pump, the refrigerant condenses back to liquid again.
• DSI electronic working fluid regulation
  DSI technology (electronically controlled expansion valve) is used to regulate the refrigerant cycle in the best possible way.

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• Efficiency
  In heating technology: the efficiency of a heat pump with which energy sources are converted into useable heat. 
• Evaporator
  The heat exchanger of a heat pump (or fridge). This is where the heat from the source (e.g. ground) is extracted from the brine by evaporating the working fluid. In systems with direct evaporation, this process occurs in the ground itself.

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• Flat-plate collector
  A simply designed solar collector in a glass-covered, thermally insulated box with absorber plates through which water flows and heat is absorbed. The absorber plates have a selective coating (TiNOx). Flat-plate collectors are excellent value for money, which is why they are popularly used today. 
• Flow temperature
  The temperature of heating water as it flows to a radiator. Depending on the outdoor temperature, it is between 35°C and 70°C for outdoor temperature-controlled heating regulation. In systems with just panel heating (underfloor or wall heating), it is between 25°C and 40°C. In heating systems without a heating mixer, the flow temperature is the same as the temperature of the water in the tank.
• Fresh water technology
  A hygienic way of heating water. Water is heated up as it flows and is not stored. A flow heat exchanger only heats the quantity of water that is currently required. A buffer store is generally needed. 

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• Geothermal energy
  Geothermal energy is often thought of in conjunction with heat pumps for heating, which draw heat from the ground via pipes buried in the ground. This image of geothermal energy use is not precisely correct since the potential heat is primarily environmental energy: ground heated by sunshine and precipitation. To use the heat inside the earth, boreholes or probes have to be drilled to get close to the liquid magma. At depths of 500 metres or more, geothermal energy (hot water) can be used directly in some regions.
• Ground collector
  A high-quality copper refrigerant pipe coated with polyethylene through which a working fluid flows. 
• Ground probe
  A probe that extracts free energy from the ground. 
• Groundwater pump
  Transports groundwater from a supply well to a heat pump.

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• Heating costs
  For a heating system these include capital costs, operating costs and overhead costs.
• Heat exchanger
  A device that can transfer heat from one medium to a different or the same medium without the media becoming mixed in the process. Heat exchangers are found in hot water storage systems as wrapped pipes or bundles of pipes, which transfer heat from the heating water to drinking water. In airing and de-airing systems with heat recovery, channel heat exchangers are used to take heat from the ventilation, for instance, and transfer it to the colder incoming air. 
• Heat output
  The useable heat energy released by a heat generator over a specific time (e.g. one hour). It is specified in kW (kilowatts). The heat output must be at least as high as the building heating load.
• Heat pump
  A heating device that absorbs energy with a low temperature on the inbound side and releases energy with a higher temperature on the heating side. The environmental energy (air, ground, water) is absorbed, causing a working fluid to evaporate. The slightly heated gaseous working fluid is compressed by a compressor, which raises the temperature further. The then much hotter working fluid can transfer the heat to the heating water. During the process it cools off and returns to the cycle.
• Heat pump system
  A heat pump system for heating consists of a heat pump motor and heat source system (e.g. ground collectors, ground probes or similar), as well as regulation technology, a heating circulation pump and, if necessary, a buffer store to cover the off-times and a hot water storage tank.

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• Modulating operating system
  In a modulating heat pump system, the released heat output adapts to current requirements in a wide range, without the heating device switching itself on or off. A modulating system is more efficient, has lower emissions and less wastage than one or two-level operating systems.

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O  (back) 

• Operating costs
  Costs for central heating, for instance, which arise on top of overhead costs and capital costs. . These include expenditure on operation, inspection (e.g. chimney cleaning charges), maintenance, cleaning, servicing and insurance.

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• Panel heating
  Pipes laid under the floor (underfloor heating), in walls (wall heating) or the ceiling (ceiling heating) through which heating water flows. Because of the large surface area, only low heating water temperatures are required, which is good on fuel. Full panel heating is needed in order for heat pumps or solar heating systems to run efficiently. 
• Performance
  Comparisons must be based on identical operating conditions. The following codes are defined by EN 255:
  • W = water
  • B = brine
  • A = air
  
  Energy efficiency ratio for the ideal comparison process (Carnot cycle)
  Energy efficiency ratio (Carnot) = T/(T-T0)
  
  T: surrounding temperature to which heat is released, in K
  T0: surrounding temperature from which heat is extracted, in K

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• Refrigerant
  A substance with a low boiling point which runs through a cycle, evaporating when heat is absorbed and condensing back to liquid when heat is output.

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• Supply well
  A well that supplies groundwater.

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U  (back) 

• Underfloor heating
  Low-temperature panel heating used to heat habitable and functional rooms.

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