Geothermal heat pump

A heat pump system extracts the environment (ambient air, ground water, or soil ) heat and raises it to a heat pump to a usable higher temperature level to thereby heat buildings or other facilities can.

  • 3.1 Coefficient of performance and grade
  • 3.2 seasonal performance factor ( SPF)
  • 5.1 heat pump types after heat sources 5.1.1 Air Source Heat Pump
  • 5.1.2 geothermal probes 5.1.2.1 geothermal probes with geothermal collectors
  • 5.1.2.2 geothermal probes with wells as a heat exchanger
  • 5.1.2.3 borehole heat exchangers with spiral collector or geothermal baskets as a heat exchanger in great depth
  • 5.3.1 3 -circuit system
  • 5.3.2 2-circuit system
  • 5.3.3 1-circuit system
  • 6.1 Germany
  • 6.2 Austria
  • 6.3 Switzerland
  • 7.1 Direct investment
  • 7.2 Operating costs 7.2.1 fuel oil
  • 7.2.2 natural Gas
  • 7.2.3 Off-peak electricity

General

The heat pump extracts a reservoir ( air, groundwater, soil ) heat and thus cools the heat source. As long as the absolute temperature of the source is above the absolute zero at -273.15 ° C, can theoretically be removed from the heat source, but only along a temperature gradient. The efficiency of the heat pump - in terms of the coefficient of performance - but decreases the more, the lower the temperature of the source.

The heat pump is technically as a refrigerator constructed, except that in the heat pump, the hot side is used ( the condenser of the heat pump ) for heating. The insert is more efficient the lower the desired temperature difference between the heat reservoir (for example, groundwater from 7 ° C) and the " flow temperature " is ( = " heating flow " = the temperature at which fed the water in the heating circuit is ). With increasing temperature lift the performance of the heat pump decreases. Most heat pumps are designed for flow temperatures up to 60 ° C maximum.

Heat sources for heat pumps are water, moist soil or moist air. If the evaporation temperature is below 0 ° C, ice forms on the heat exchanger surfaces. Ice is an insulating layer and deteriorates the heat transfer significantly. Through newer technologies (gas cooling) heat pumps which extract the outside air, the heat can currently be used down to -25 ° C outside temperature effectively. A heat pump, a water tank at 10 m depth (about 5 ° C global temperature ) extracts the heat, can be operated independent of the outside temperature (below the freezing point of water because ice is lighter than water and therefore floats on the surface ).

For the heat output power must be applied ( "Input" ). The ratio of income ( "Output" ) to the input is called the coefficient of performance. A performance number greater than 4 is considered economically.

The energy can be supplied by electricity or fuels. Combustion of fuels can operate an absorption or adsorption, or may be used in internal combustion engines, driving a compression refrigeration machine, such as the electric motor.

Technical details

For heating of buildings electrical compression heat pumps are the lower power range usually used at higher power and gas engine heat pump. Also used are absorption and adsorption heat pumps. Heat pumps using the Vuilleumier cycle are not yet ready for the market.

The principle of operation can be compared well with a refrigerator that cools the inside and outside heated. Many of these systems can be used in reverse mode for cooling. Partly because heat pumps have significant start-up currents on system reactions ( voltage drops ) can cause the connection must be approved by the power company. The permit is issued as a rule, subject to certain conditions ( starting current limitation, starts / hour limited ).

The compressed refrigerant is condensed in the condenser. This is a heat exchanger, which is on the opposite side with a heat transfer medium, usually water or water- brine mixture (antifreeze), acted upon. The energy released in the condensation of refrigerant, heat is absorbed by the heat carrier and transferred to the radiator or heating surfaces. The heat output, which can be used based on the amount of electric power the engine compressor to the condenser, increases with decreasing difference between the evaporation and the condensation temperature in the refrigeration cycle of the heat pump.

The ratio of the heat output ( "Output" ) for electrical power ( "input" ) is called the coefficient of performance of a heat pump (English Coefficient of Performance, abbreviated COP).

A low heat carrier temperature ( flow temperature) can be implemented in particular with underfloor heating because the heat transfer surface is very large. In addition, a very good thermal insulation for the building to be heated must be sought in order to drive a low flow temperature of the heat carrier with low heat demand.

Heating surface and median temperature (temperature differences) over a radiator or underfloor heating relate to each other indirectly proportional. This is to be compared with the change in power output of the primary storage at increasing temperatures. This problem also caused that a heat pump the tank temperature can be raised only to a certain temperature. The maximum hot water temperature can be generated from the maximum compressor high-pressure dependent.

When heating means of storing ground probes must be taken to ensure that the ground probe not more than 100 W (thermal ) / m probe is loaded to avoid excessive icing of the probe. Since ice is a poor conductor of heat, the probe temperature drops too far, and the coefficient of performance is within the range below 2.5 uneconomic.

Choice of refrigerant

Crucial for the efficiency of heat pumps is above all the choice of refrigerant. Today in the European market available heat pumps for both domestic and industrial applications almost exclusively with HFCs ( hydrofluorocarbons ) are operated. Systems with less environmentally problematic refrigerants such as CO2 or propane have so far not been widely distributed. With CO2 can produce high flow temperatures and achieve higher seasonal performance factors than with traditional systems, according to studies. Moreover, it is non-flammable and less toxic. In Japan since 2001 CO2 air-water heat pumps are available in the market; For some time they are also occasionally offered in Europe. With the use of CO2 is required components which can be operated at higher pressures. For this run research projects, for example, at the Technical University of Braunschweig (Chair of Thermodynamics ) and the Technical University of Dresden. CO2 air-water heat pumps can displace in niche applications, some very expensive competition systems ( geothermal probes, Eissonden, brine heat pumps, etc.). Due to the high reproducible flow temperatures ( ≥ 90 ° C) CO2 air - water heat pumps suitable (without significant increase of the heating surfaces ) with a suitable design for the renovation of heating systems in buildings.

Blocking times

When using a low Heizstromtarifs, the electric utilities, the heat pump at times high power consumption, such as in the morning and in the early evening, after the technical connection requirements ( TAB) off up to three times a day for two hours (even remotely). However, many power supply companies (utilities ) may differ from this opportunity down, as they control the blocking times in relation by means of the ripple control receiver on the actual load. The blackout dates are then relatively short, so that an increased technical effort ( for example, buffer memory ) is not essential for a blocking time bridging usually.

Buffers are also of limited use for bridging blocking times as for the shutdown of the heat pump from the RU no distant signal is given. Therefore, the temperature sensor in the buffer could be "on" signal to the start-up of the WP in entrance of the blocking time just that. If this occurs, is located in the buffer memory no or little usable temperature gradient. The probability that a building is cooled by a closed period is relatively low, but to a limited extent possible ( cooling 1-2 K).

  • A building with very little thermal mass cools more quickly than one with large thermal masses;
  • A poorly insulated building cools down faster than a well-insulated;
  • A large building cools more slowly than a small ( better ratio of building surface to enclosed space ).

Heizstabsteuerung

In the event that the performance of the heat pump at low ambient temperatures, while high heat demand is insufficient, the most heat pump systems have to complete a simple electric heater ( heating element ) in the hot water circuit or memory.

The technical connection requirements (TAB 2007) stipulate in section 10.2.4 that the compressor and the immersion heater can be switched on only six times per hour. Manufacturers implement this provision by a ten-minute break is inserted after the disconnection. In the planning and interpretation of these facts must be taken into account.

The temperature change of the heating rod is determined by the mass flow rate, the specific heat capacity of the fluid and the heating rod.

With water as the fluid is the temperature change per kW heating rod element and the mass flow.

With a small hysteresis and large temperature lift the heater only a few minutes and at least ten minutes off. The supposedly high power input of the heating element can not unfold. By rearranging the above formula by the time the following applies:

If the hysteresis 1 K, the heating rod element 1 kW and the water is 1 kg, the heater is switched off after 4,176 s.

Indicators

Coefficient of performance and grade

For the assessment of heat pumps is the Coefficient of performance ε - also called Coefficient of Performance (COP ) - used. It is the ratio of actual output power to the heating applied electrical drive power of the compressor ( and compressor ). The achievable performance coefficient is a function of the temperatures used in accordance with the second law of thermodynamics is limited to the reciprocal value of the Carnot efficiency for a lossless labor force heat engine, the Carnot coefficient of performance:

The ratio of actual to Carnot coefficient of performance is the grade. Thus, the figure of merit is calculated

Electric compression heat pumps for heating buildings achieve continuous operation under specified standard operating conditions grades of around 50 %. This value is mainly used to assess the quality of the heat pump itself, he does not consider the rest of the heating system.

For a heat pump with borehole heat exchanger ( evaporator temperature about 0 ° C) and under floor heating ( about 35 ° C inlet temperature) is calculated as:

If at the same heat pump cycle to radiator heating at 55 ° C () flow temperature ( evaporation temperature -0 ° C) is connected, there is a significantly lower figure of merit:

The use of a borehole heat exchanger as a heat source, the evaporation temperature is independent of the ambient temperature.

A heat pump used as a heat source, the ambient air has a much lower evaporation temperature than the plant with a geothermal probe. With increasing heat demand the ambient temperature, and thus the figure of merit decreases. In addition, the heat transfer coefficient of air to the evaporator surfaces is low. Therefore find the largest possible area, ribbed tubes in the evaporator application. There is a fan or a fan is necessary, which forces the air through the evaporator surfaces.

If the evaporator is often the dew point not reached, so the forming condensate (water) must be dissipated. If in the evaporator of freezing of the condensate below, the yield factor decreases due to the insulating effect of the ice shell to zero. De-icing energy is meaningless, it will be supplied with the same amount of energy that has been previously extracted from the frozen condensate.

In the following calculation of the figure of merit an outer temperature of about 7 ° C is placed under a temperature difference of 12 ° C between the inlet air temperature and the evaporation temperature of the refrigerant, so that cold side ( such as -5 ° C) is applied:

It is clear that the coefficient of performance of a heat pump is strongly influenced by the design of the heat exchanger, condenser and evaporator. Not Seek is the icing of the evaporator. The system of Example calculation C is only useful when the outside temperature is greater than 12 ° can be used.

With the geothermal probe is independent of the prevailing outside temperature, a heat source with a relatively high temperature, respectively, while the outside air is a poor heat source. On the side of the heat sink a small temperature difference between the room temperature and the heat carrier flow temperature should be sought with the largest possible area. In the examples shown, the coefficient of performance varies by a factor of 1.8 between the borehole heat exchanger / heat pump underfloor heating and the outside air / radiator heat pump.

Seasonal performance factor ( SPF)

To evaluate the energy efficiency of a heat pump heating system is called the seasonal performance factor ( SPF), also known as Seasonal Performance Factor ( SPF) used. It indicates the ratio of the votes over the year to the heat absorbed electrical energy and is not to be confused with the determined under standardized laboratory conditions merit. To ensure comparability, it is important to be aware of the system boundary in the clear. The annual coefficient may contain the additional energy required for the auxiliary drives (brine pumps, groundwater pumps and air blowers, etc. ), which make up a considerable part in the wrong interpretation.

The seasonal performance factor calculated by the following formula:

Many factors influence the seasonal performance factor. Manufacturers provide example hardware and software of different quality. The same applies to the work of installation operations. Furthermore, change in the course of the temperatures at which the heat pump has to work. On the drain side usually dominates, for example, in the winter to heat the building with a comparatively low temperature, in the summer, however, the domestic hot water with relatively high temperatures. The entire design of a heat pump heating system, such as the depth of the geothermal probe, the choice of saving or heat distribution system, has an impact on its efficiency. On the source side temperature fluctuations are also observed, but this depends greatly on the source. Thus, the air temperature hardly varies greatly in daily and seasonal course, the soil and groundwater temperature. The location and the climate is also relevant.

The JAZ is located in Germany on the order of 3 to 4.5, in groundwater systems also about 5 outliers in both directions are possible.

Ecological balance

The environmental impact of an electric compression heat pump is influenced by several factors:

  • Type of power generation ( CO2 balance, emission of pollutants )
  • Losses in the conduction of electricity,
  • Seasonal performance factor of the heat pump,
  • GWP of the refrigerant.

When considering greenhouse gas abatement costs remain the

  • Direct and
  • Indirect investments

Relevant to the overall system heat pump.

A heat pump with a seasonal performance factor ( SPF) generated by 3 - related to the consumption of electric energy - three times the heat. Crucial for the ecological balance of the heat pumps is the way how the necessary for the operation of electricity was produced. Originates mainly from the current conventional energy sources, as currently only little primary energy is saved with a heat pump. The average efficiency of electricity generation in Germany is 42.1 % (as of 02 /2011). In addition there are line losses, which average at a magnitude of about 7 %. This results in an overall efficiency of power generation of about 39 % and, therefore, it takes approximately 2.55 units of primary energy to produce one unit of electricity. Heat pumps with smaller JAZ 2.55 therefore consume more primary energy per unit of heat as a direct heating using a furnace. If it is considered that heating oil or gas heating boiler not use the whole energy of the fuel, a heat pump can also be correspondingly lower JAZ have better primary energy efficiency than this. However, to be considered is the type of fuel used in power plants and home heating, so even with the same primary energy demand, emissions can fail ( due to high nuclear share, for example ) in electricity generation is higher ( eg, focusing on coal-fired electricity ) or lower.

A study by Ulrich Wagner of the Munich Technical University came to the conclusion that already can save primary energy in the energy mix of the year 2008, between 25% and 50 %.

To reduced carbon dioxide emissions compared with the reference system condensing boiler occurs in the electricity mix by 2008 even with a SPF of 2.0.

According to the primary energy-related figure of merit, that is, the ratio of the recovered heat to chemical energy inserted into gas, coal, oil or nuclear energy, as follows:

Regardless of the primary energy consideration heat pumps can also reduce emissions of certain pollutants (carbon dioxide, nitrogen oxides, particulate matter, sulfur compounds, etc.) contribute, as in use of fuel in power plants, a highly effective flue gas cleaning (at least with the same fuel ) usually specifically lower emissions than causing local combustion.

Heat pumps can environmentally harmful refrigerants such as R134a ( 1,1,1,2- tetrafluoroethane), R404A ( refrigerant substitutes for R502 and R22 ( chlorodifluoromethane ) ) containing R407C (replacement of the refrigerant R22) or R410A. One kilogram of refrigerant developed the same global warming potential as 1.3 to 3.3 tonnes of CO2. If handled improperly, recycling, it may lead to the release of these substances and corresponding greenhouse gas emissions. However, there are also climate-friendly alternatives such as R744, R290, R600a or R1270.

System types and sources of heat

If heat pumps are categorized according to their heat source, so usually divided into three categories:

  • Air source heat pump (more precisely, outside air)
  • Geothermal heat pump (eg via probes or collectors, see below)
  • Water heat pump ( eg, groundwater, lakes, rivers )
  • Solar brine storage (solar heated salt water storage )

This classic tripartite division is reflected inter alia in the logo of the European Heat Pump Association oppose ( Light Blue, Dark Blue, Brown for air, water and earth). Indeed, other low-temperature - sources can be used for heat pump systems. Thus, it is state of the art, air ( eg ventilation compact units in passive houses ), waste water, ( commercial / industrial ) process heat or solar energy to tap as a source. Regarding literature and standards, but especially with respect to the annual installation numbers, all those options are more niche products today. To be noted is the fact that in a heat pump system, multiple sources can be combined, for example via a common source-side brine circuit.

Heat Pumps types after heat sources

Air source heat pump

An air heat pump uses air heated by the sun outside air for heating and preparation of hot water. In particularly low outside temperatures, the efficiency decreases significantly. By bivalent - parallel operation of heat pumps with certain combi-systems can increase the efficiency by an alternative heating system is switched on in these cases to provide the peak load required. The term air heat pump is used for various systems. Therefore, it is usually divided in a more differentiated:

  • Air-water heat pumps extract the ambient air through a heat exchanger heat and give it to the existing heating and / or hot water circuits from ( underfloor heating, radiators, etc.).
  • Air to air heat pumps extract heat from the air and put it at the air - heating system or air conditioning.
  • In the direct heat pump, the air is removed from heat, which is without additional heat exchanger losses by direct condensation is introduced into the heating screed laid in the floor heating pipes. Unlike other air heat pumps refrigerant flows directly through the copper pipe of underfloor heating. The direct heat pump has neither circulation pumps and no secondary heat exchanger. A direct heat pump is only suitable for new construction. The disadvantage is that the control of individual heating circuits is almost impossible.

Air heat pumps are usually less expensive compared to other heat pumps to buy. Air-water heat pumps can depending on the make and set up outside inside buildings. The efficiency of air source heat pump sinks deeper so the outside temperatures. Air HP can be installed in older buildings, renovations and new buildings and in both monovalent and bivalent operation in good use (see above section refrigerant). Also relevant is the noise pollution on the environment that makes a statement near the building often problematic. A typical sound pressure level at one meter distance of, for example 51 to 62 dB ( A) ( Sheet Viessmann Vitocal 300 -A) is perceived as very disturbing. The Court accepted in quiet residential areas, at the property line, at night only up to 35 dB ( A) (judgment of the District Court of Munich: AZ 123 C 3000 /03).

The annual coefficient of modern LW -WP is improved by the use of inverter technology and enables over previous air - water heat pumps according to the manufacturer now equivalent performance (COP, coefficient of performance) as the geothermal heat pumps. The values ​​according to VDI 4650 can differ.

From the environmental perspective, the air heat pump, according to the Austrian label for geothermal recommended limited, as these are the specification of a seasonal performance factor ( SPF) greater than 4 do not meet, and thus no state subsidies are possible. However, this is contradicted by the promotion form the province of Upper Austria in the stands that air heat pumps with a ( JAZ ) will support 3.5. Unique statements are difficult and there are quite different viewpoints. BAFA in Germany are ahead of COP values ​​of 3.1.

The Local Agenda 21 in Lahr ( Black Forest) came after a two-year field test (2006-2008) to the conclusion that the state should not promote air source heat pumps for heating and domestic hot water in low energy houses and renovated buildings due to their energy inefficiency.

Guide values:

  • Underfloor heating flow temperature 30 to 35 ° C
  • Heaters / radiators flow temperature 50 to 55 ° C

Geothermal probes

Geothermal probes utilize the sensible heat of a terrestrial body as an energy source. The withdrawn sensible heat is the heat conduction at about the half

  • From the earth and
  • The heating of the earth from the solar radiation

Refilled.

In Germany, the calculations usually assume a temperature of 0 ° C for geothermal collectors or geothermal probes and 8 ° C for groundwater.

Borehole heat with geothermal collectors

The extraction rate depends very much on superficial factors, such as sunlight, rain, frost, etc. Near-surface collectors should be planned so that's the bottom Sensible heat for the supply sufficient. Icing the area then represents a "reserve " that can provide the additional substantial amounts of heat ( latent heat ), but with a falling brine temperature ( with any degree less brine temperature increases the power consumption by about 2.5 %)

Geothermal probes with wells as a heat exchanger
Borehole heat exchangers with spiral collector or geothermal baskets as a heat exchanger in great depth

Geothermal energy extraction from tunnels

Tunnel are increasingly being used for the extraction of geothermal energy. Either outflowing water directly or heat pumps. The tunnel walls are used to collect geothermal energy. According to a study by the Swiss Federal Office of Energy from 1995 could be gained heat from 130 of the 600 tunnels and tunnels of Switzerland around 30 MW.

Groundwater heat pump ( water to water heat pumps)

Here, groundwater is extracted from an extraction well and returned through a so-called injection wells. Here, the water quality is of decisive importance to the reliability of the system. There are systems that directly through the evaporator heat exchanger can lead (stainless steel) of the heat pump ground water, and systems that manage the groundwater only by an upstream heat exchanger (stainless steel) before the power to the evaporator heat exchanger (often copper ) cast. Before installing a water sample should be taken and evaluated against the requirements of the manufacturer of the heat pump. By adventitious slightly higher groundwater temperatures throughout the year (about 9-11 ° C) groundwater heat pumps work so with annual coefficients to about 5, but with increased demands on the heat exchanger against clogging or oxidation with iron and manganese content of water. Furthermore, it usually requires a water license ( Water Authority ), since the operation means an intervention in the groundwater balance.

Sometimes geothermal energy is used in swimming pools, so-called " power pools " as a heat source or from salt water filled " solar ponds ".

Waste water heat pump

A waste water heat pump is installed in the sewer system and uses the heat from waste water. For use mainly larger sewage pipes are, these can then be but also achieve high performance. In the sewers, the temperatures during the year are largely uniformly 12 to 20 degrees Celsius, also insulates the soil around the tubes causing load spikes can be buffered. Especially larger systems, management centers, hospitals, schools, housing estates or indoor swimming pools with a relatively constant heat demand are considered economically heat. Perspective is scheduled to cache in the sewer waste heat from industrial processes or power plants targeted and retrieve it back by the heat pump if necessary.

Solar ice - storage heat pump

On the Solar Ice memory of the memory is in a large water tank which makes it available for use of heat during freezing to 0 ° C by a cooling means ( eg, a water -glycol mixture ) the so-called heat of crystallization.

The resulting in further heat removal icing process is intentional, because the phase change from water to ice brings another energy gain. Here, the temperature remains constant while at 0 ° C., but it is more 93 Wh / (kg K) crystallization energy which can be used by the heat pump. That's the same amount of energy that is released when water is cooled from 80 to 0 ° C.

The system largely corresponds to the water - water heat pump. However, the cooled water is not flowing here as groundwater simply, but in the summer serves directly as a cooling medium that without renewed energy costly heat exchange process in reverse mode ( air cooling system) can be used easily through a circulating pump in the house heating and so partly regenerates the memory.

Regeneration is constant through all the energy sources that are warmer than 0 degrees.

The enthalpy - ie the "Heat " Contents of the " ice storage " is 333.5 kJ / kg or 85 kWh / m³ ice. These are good 8 liters of heating oil per cubic meter, therefore the system has to keep out the cold snakes around which lays a mantle of ice over time hinders the further removal of energy, are oversized.

Common models with a solar ice - storage of about 12 m³ and 5 solar air collectors (á 2 m²) on the roof, provide the monovalent operation about 1800 full load hours per year for heating with a maximum heat load of 7.5 kW.

This is theoeretisch a water - water heat pump for year-round heating including domestic water heating is still the first choice, but in summer the energy required for cooling presumably with the ice storage system lucrative. The systems therefore compete for the overall energy efficiency.

Seasonal underground storage tank plus heat pump

When underground storage tanks, it is possible for them to use as long-term energy storage. This consists of an insulated underground storage tank, which is crossed by a defined system of plastic pipes. There are buffered surpluses from other heat sources such as solar thermal. Thus an increase in the source temperature for the heat pump an average of 10 ° C results in comparison to Erdflächenkollektoren. In this case, the underground storage tank can also be supplied heat sources with relatively low temperatures can not be used directly for heating. The heat carrier comes next (brine) or a water -glycol mixture, pure water in question.

Operation without antifreeze allows for use in drinking water protection areas. This is based on the controlled temperature level in the underground tank, which is above the seasonal change approximately between 5 ° C and 23 ° C.

The system is largely the brine - water heat pump with special control technology, as can heat and cool comparable systems. As heat sources come in first Line surplus from solar systems or process heat in question.

An underground storage tank of 100-120 m³, a coordinated heat pump and approx.12 -14 m² solar thermal flat plate collectors, cover in heating from a heat load of about 10 kW.

The underground storage system is for new buildings i.d.R. installed under the floor slab to exploit synergies with already have work as foundation, ice wall, foundations, insulation of the floor plate, etc.. The problem appears when the use of existing buildings, as well as in urban areas, since the necessary land could not be available there. The area in which the underground storage tank is installed should be possible flows not from groundwater, otherwise increased demands are placed on the seal.

Long term energy storage are only notifiable against the lower water authorities since usually the installation takes place only 1,20-1,50 m below the floor slab and the soil is not used as a heat source. Due to the low installation depth no aquifers are usually encounter.

Air / water brine / water heat pump ( hybrid heat pump)

The air / water brine / water heat pump is a hybrid heat pump that uses only renewable energy sources in their execution. It combines air and geothermal heat in one compact device. Thus, this hybrid system differs from other systems that also use at least two heat sources. These usually form a mix of conventional heating (gas condensing technology ) and renewable energy sources.

The air / water brine / water heat pump ( hybrid heat pump) is equipped with two evaporators ( an outside air evaporator and a brine evaporator), both of which are connected to the heat pump cycle. This allows, in comparison with the external conditions (eg air temperature) to use the current time to the most economical heating source priority. The hybrid system automatically selects the most efficient operating mode ( air or geothermal heat ). Depending on the mode of operation of the air and geothermal energy sources can be used simultaneously or alternatively.

Modes

It is usually distinguished between three modes of operation:

  • The mono-mode = heat pump only
  • The dual-mode = Heat pump and boiler fuel or additional solar panels and the like
  • The mono-energetic operation = Heat pump and immersion heater (mostly with inexpensive models)

Construction of circuits

The system types can be distinguished by the number of fluid circuits. The decoupling of the circles by indirect supply of heat of vaporization from the environment and the removal of the liquefaction energy over a hot water heating system are advantageous for the control (but energetically lossy ), the amount of refrigerant and the chances of leaks are small.

3 -circuit system

Long the heat pump heating system took advantage of this form. Brine is used in the form of a deep hole or surface collector. In this case, as a transfer medium circulates in a closed loop brine and absorbs the heat of the soil on in order to leave in the heat pump to the refrigerant circuit. In the third circle, space heating, water that is heated via a heat exchanger by the heat pump circulates. In this type of system, a CO2 probe can come in a deep drilling as the collector used. The advantage ( as seen on the efficiency ) with respect to the brine in a deep hole is not necessary energy to circulate the medium in the collector.

2-circuit system

They are also called direct systems because they dispense with the separate brine circuit. It eliminates the heat transfer from the collector circuit (brine ) to the Working Group of the heat pump. The refrigerant absorbs the heat directly on ( direct expansion ). This brings an energy advantage of at least 5 degrees. The elimination of the brine circulation pump reduces power consumption. When using ground spikes as a heat source, the direct evaporation is not possible; it must be used a brine circuit.

1 circle system

In this case, the refrigerant circulates in the tubes of space heating, the heat pump and the collector in the garden in a common closed circuit. Thus, the heat transfer to water as the heating medium in the house is not necessary. This system has advantages of energy, as the circulation pump and the temperature drop attributable to the heat exchanger for heating. The refrigerant is usually done as a hot gas to the collectors of the underfloor heating and condensed in the condenser system. The problem with this arrangement are:

  • Significantly higher refrigerant charges,
  • The elaborate piping related higher probabilities of leaks,
  • Problematic oil return from the floor panel,
  • Load-dependent refrigerant distribution in the overall system,
  • Difficult control and mutual influence of the floor collector.

In 2007 dared to realize this type of system approach only a few ( two to three ) producer because it was difficult to control system technology (pressure and temperature of the refrigerant and heat pump runtime ).

Heating water distribution / warehousing

If the heat supplied by the heat pump can not be temporarily removed enough / used, so the hot water can be stored; this happens in a large insulated tank, a buffer memory. This tank holds i.d.R. several hundred gallons of water. To heat now circulates the water flow between the tank and the radiator or underfloor heating. The heat pump heats the water in the tank.

Dissemination

Germany

The market share of heat pump heating systems in new buildings is very country-specific and in 2005 was nationwide average of 10%, then the ground-coupled heat pump with a share of about 40 % was the most successful. 2010, the proportion of heat pump heating systems in new buildings in Germany 23.4%. With newer techniques and more efficient methods of construction and operating principles Heat pumps are seen as alternatives to conventional systems based on fossil fuels heavily in growth. Especially the market share of air - water heat pumps has risen sharply since government grants, a firm and favored heat pump price of electricity and not least the lower investment costs, these systems make it attractive. 2012 reached the air - water heat pumps with a market share of 62.7 percent of all electrically driven compression heat pumps only cooling units with additional building heating function. Especially for new buildings and renovations, these systems are the conventional boilers preferably more often.

Austria

A total of 190 200 Heat pump systems were built in Austria from 1975 to 2005. Most heat pumps annually in the years 1986 and 1987 ( with over 13,000 pumps per year) installed.

Switzerland

In Switzerland, the market share of new buildings is around 75%. The spec. Cost of heating with a geothermal heat -using heat pump be 3.9 cents / kWh. ( about 3.2 cents / kWh), while a conventional oil heating with spec. Cost of 7.9 ct. / KWh ( about 6.6 cents / kWh) can be estimated. State support is unnecessary.

Costs

Direct investments

The initial investment in heat pump systems are higher than in conventional boilers, where gas or oil is burned. But in the new building additional accounts like a chimney installation. There is also a storage room for the fuel in oil, pellets or wood omitted.

Heat pump heating on ground collector or geothermal probes base due to their installation (several holes to at least 50 meters, or large-scale excavation ) quite expensive and can economically be used only when a new building. Specially ground collectors require relatively large plots of land, which is to be realized in urban areas almost. For small pieces of land and for the existing building spiral collectors / geothermal baskets are an alternative, there, for example in the course of an energetic refurbishment of the old building.

Even with heat pumps that use groundwater as a source of energy, the investment costs and the demands on the land surface is high. As a rule, you must have a supply well and a return well ( at a distance of at least about 15 m approximately in the groundwater flow direction, depth to adequately water table ) as well as build the underground connecting line to the plant. The wells are drilled with a diameter of 15 to 30 cm or run at high ground to about 4 meters as well shaft. Instead of swallowing the fountain just a cheaper soakaway is also partly built, but the changed the land drainage and thus is usually not allowed. Furthermore, a somewhat greater pumping capacity of the pump is necessary, since the amount of energy of the pumped water is lost up. In some areas, however, is the simultaneous use of ground water for summer irrigation approvable. Costs vary greatly depending on the site requirements. In addition, subject to an additional cost of a soil report and the approval process.

Lower investment costs are applied to systems that are based on air - water or air -to-air, because the cost of acquisition and installation are significantly lower. However, it is to be expected at air -water or air -to-air systems with a significantly poorer performance numbers in winter, which the operating costs are higher than with Earth systems. Therefore, an air - water heat pump is well suited for dual-mode operation with an existing fossil heating system, covering the peak load and very low outdoor temperatures.

As a further investment to install a second power meter has to be considered when using the lower heating current, which can have an extension of the current box result in existing buildings.

Running costs

Fuel oil

One liter of fuel oil currently costs (as of 31 October 2011) by 87 cents and contains about 9 to 10 kWh thermal usable energy. This results in a price of about 8.7 to 9.6 cents / kWh for oil. Oil fired boilers, have in operation at average efficiencies of about 90%. This results in the generation of useful heat for a price from 9.6 to 10.6 cents / kWh heat. Not included is the energy requirement of the oil burner pump and associated compression of the blower that mixes the atomized oil with air.

Natural gas

The fuel price of natural gas was in February 2009 at 20,000 kWh / year required the equivalent of 7.6 cents per kWh. However, gas condensing boilers with need related to the heating value efficiencies of over 100 %, according to a Öko-Institut study still 1,114 kWh of primary energy per kWh of useful energy. Included is then also the current which is required in addition to the exhaust blower. They therefore cause a cost of about 9 cents / kWh useful heat.

Low tariff electricity

With a current gross electricity price of 22.51 cents / kWh (heat pump electricity tariff as of 04 /2013, including all taxes and duties) and a seasonal performance factor SPF of the heat pump heating of at best 4.0 costs the generation of useful heat by means of air - water heat pump at best 4.5 euro cents / kWh ( gross).

The cost of the chimney sweep omitted if no additional stove or similar is available.

The heat pump tariff offered by electricity suppliers is significantly cheaper than the household tariff used. In substance, the higher investment costs of the heat pump over an oil or gas burner, the offered price of electricity for the heat pump and its running time and the coefficient of performance of the heat pump must be considered as in any business case.

Economic Importance

Gas and oil heating systems bring in economic terms, greater dependence on foreign countries. In addition, these resources are finite and - affected price increases - partly drastic.

Alternatives offer the quoted various systems of heat pumps. Depending on the power number and power mix but CO2 emissions are attributable not, but move only from the domestic heating with fossil -fired thermal power plants. Even taking into account the combustion plant facilities in such power stations or low-quality fuels and despite innovative heat pump technologies and their increased efficiency can be achieved only when performance figures of more than 4, also in economic savings. Only then will the total efficiency -related generation and distribution losses of electricity than comparatively noble form of energy to be released and the CO2 emissions from combustion plant locally fossil fuels. As the share of renewable energy (share in 2012: 23%), however, this threshold decreases.

In addition, a study was commissioned by the Federal Ministry of Economic Affairs to the conclusion that heat pump systems can help to improve the grid integration of renewable energy, especially wind energy, as well as the load management in the electricity market.

Haloalkane 1,1,1,2-Tetrafluoroethane Low-energy house Wastewater Rappen Heat of combustion Heat of combustion#Lower heating value Wind power Furka Base Tunnel Stiftung Warentest
311641
de