Electric building heating
An electric building heater , colloquially called electric heater for short , is a technical device for heating buildings with the help of electric heat . A fundamental problem with all electrical building heating systems, with the exception of heat pump heating, is the low overall efficiency , which, when including the generation of electricity in conventional thermal power plants, turns out to be significantly worse than the direct combustion of fossil fuels . This also results in a poorer environmental balance for electrical heating systems based on the resistance principle compared to fossil-fueled building heating systems . In addition, with all systems, even when using cheaper night-time electricity, the energy costs are usually comparatively high, which, however, is less significant if the rooms are only used occasionally and can be compensated for by the low installation and maintenance costs.
Types of heating
Low tariff storage heating
- → Main article: Night storage heating
The night storage heater is an electrically operated heater in which a heat storage tank is heated up during the so-called low load times by means of cheap electricity from the electricity supplier. This type of electricity is also known colloquially as night electricity.
- → Main article: Fan heater
A fan blows over an electrical resistance wire, which is heated by the flow of electricity.
- Advantage: versatile, light, spontaneous
- Disadvantages: drafts, running noise, expensive to maintain
Partial storage heating
A heat accumulator, usually made of natural stone, is heated electrically to approx. 80 to 90 ° C. The heat accumulator emits more long-wave radiation in the infrared range . The design with inner or outer ribs is unusual; heat distribution via convection is therefore subordinate.
Partial storage heaters are available in various designs. In addition to the models with a storage core inside, which are very similar to a conventional radiator, there are also designs in which the natural stone storage body is used in the form of a plate with heating elements behind. The latter are often referred to as "marble heating" or " natural stone heater " marketed.
- Radiant heat similar to a tiled stove
- little need for space
- Depending on the provider and the number of radiators required, lower investments compared to a complete oil or gas central heating system
- Depending on the manufacturer, no follow-up costs for maintenance
- flexibly usable
- Consumption costs that are many times higher than with oil or gas central heating
- higher pollutant and CO 2 emissions, even compared to old gas and oil heating systems due to the low level of efficiency in generating electricity
- Due to the lack of heat distribution in water-carrying pipes, no switch to alternative forms of energy or other types of heating is possible
- Due to the lack of a central heating system, decentralized hot water preparation is necessary at all consumption points
- the surface temperature is 80 to 90 ° C, depending on the manufacturer, so there is a considerable risk of burns , especially for small children.
- quasi-optical heat transfer, objects in the radiation shadow can only be heated by convection with partial storage heating
- Low-tariff electricity is only available for a limited time in the course of a day from almost all electricity providers, if at all.
Oil is heated in a closed radiator
- Advantage: can be used variably, because - within limits - mobile, relatively inexpensive to buy
- Disadvantage: comparatively high operating costs.
In the GDR instead, porcelain radiators of different sizes and designs that had to be filled with water were common.
Additional heating in central heating systems
An electric heating rod is used in individual radiators ( or other radiators ) of a central heating system so that they can also be used as heating in transitional periods when the central heating has not yet been switched on or has already been switched off.
- → Main article: underfloor heating
A wall or other structure is heated and emits the heat into the room with an increased proportion of infrared radiation .
In the case of surface heating, a distinction is made between wall , ceiling and floor heating . All surface heating systems use the infrared principle ( thermal radiation ). Thermal radiation without convection is the energy balance between a warm and a cold object. Ceiling heating has the advantage that it heats the objects in the room from above. Wall heaters usually work with a higher temperature, as the radiation distances are greater. With wall heating, convection and thus dust turbulence is to be expected. With underfloor heating, the objects in the room (tables, chairs, beds, etc.) are heated to a greater extent by infrared radiation, as with other surface heating systems. Due to the design, this happens from below.
- Most electrical surface heating systems are cheaper to buy than hot water radiators because they do not have to be laid and the boiler is not installed.
- The liquids in a surface heating system have a maximum temperature of 35 to 40 degrees Celsius, which is much lower in other systems, since radiation is emitted over a large area. The lower temperatures also lead to lower heating costs because less energy is lost during transport due to the lower temperature difference to the ambient temperature.
- sluggish thermal behavior. Cold walls with a high heat capacity only heat up slowly.
- Electric fields distributed over a large area when operating electric surface heating systems.
- quasi-optical heat distribution, as with a lamp, objects further away become less warm, objects in the shade remain cold.
- higher energy costs than with non-electrically operated surface heating.
Heat pump heating
Heat pump heating systems are widespread today. A carrier liquid or gas takes energy from the outside air and / or geothermal energy via a pipe system. The high energy consumption or energy output during the phase transition of the carrier substance from liquid to gaseous and vice versa is used with the aid of throttling or compression of the carrier substance. To compress the carrier substance, electrical energy is then required, which is, however, much smaller than if the heating were operated electrically alone. The carrier substance takes a large part of the energy from the outside air or geothermal energy. This means that the cost of electricity is significantly lower.
Surface heating is usually used to radiate energy into the interior of the building.
Electric heaters (and electric heat pumps) for heating purposes contribute a relatively high proportion of their total output to the annual peak load , as they mainly use electricity in winter and especially on the coldest days (see e.g. cold spell in Europe at the beginning of 2012 ). They can be switched off at critical times via load management , but only for a few hours a day, as otherwise the electricity-heated buildings would be too cold.
- Cf. Matthias Günther, Energy Efficiency Through Renewable Energies. Opportunities, Potentials, Systems , Wiesbaden 2014, pp. 103–113, esp. 103.
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