Hot water storage tank

Under a buffer is understood in a heating system, a heat store, which is filled with water. It is used to compensate for differences between the generated and consumed heat output. In this way, the system components can be operated largely independently of the consumption for heat generation. This results in many heat generator a better performance and better efficiency.

A disadvantage of heat buffers is the continuous heat loss, which results from the temperature difference between the memory and surrounding area. This can be reduced by good thermal insulation and prevention of thermal bridges. As a rule of thumb for central heating (see below) is that about 60-70 liters of buffer storage volume per installed kilowatt heat output represent a meaningful relationship between large buffer stocks and low heat losses.

A special case of the heat buffer is the so-called water heater, wherein the heat generation is directly integrated. Most common forms are electric boiler or gas boiler.

The opposite approach to heating with heat buffer is a water heater. In this heat is "just in time ", that is simultaneously produced with the consumption. This operation is only economically possible if the heat source can be switched and very quickly is adjustable and also in part load a sufficiently good efficiency has (eg electric heaters or gas burners).

Application

Central heating systems, especially with solid fuel

Application finds the buffer frequently in central heating with solid fuel furnace that bring their optimum efficiency under full load, can be controlled to less poor heat output and show significant efficiency losses with frequent switching on and off.

Log wood furnaces heat about the same time for a heating circuit, as well as the buffer. If all the wood burned in the boiler, the heating system is fed from the buffer. Also pellet heating systems show the best efficiency under full load. As their power rating but is designed so that sufficient energy is provided at very low outside temperatures and high hot water demand, the actual power requirement to almost all times of the year is significantly less than the design capacity. It is therefore just in the transitional seasons ( fall, spring ), intermittent operation required: The buffer then stores the energy during the operational phase of the heating and then writes them off as needed. Engaged in the transition period with lower heat demand inevitably adjusting timing of the heating circuit pump ( on time / off ) would be without the use of a buffer lead to the firing control in the wood stove prevents a clean and efficient combustion of the particular fuel. The use of a buffer leads to the fact that the solid fuel stove / wood stove works always under ideal conditions and operating temperature. Excess heat is introduced into the memory and retrieved from a request through the heating circuit pump. For a buffer operation 2 water circuits are needed. This is also called circulations. Circuit 1 connects the solid fuel boiler or wood stove with hot water coil via a charge pump to the buffer memory. A so-called temperature differential controller controls the charge pump. This rule compares once the temperature in the solid fuel boiler and the temperature of the buffer. When the temperature of the solid fuel boiler is higher by a usually adjustable from 2 to 20 degrees, the control the charge pump turns on and the memory gets warm. On the second circulation of the heating circuit pump is usually controlled by a room thermostat, the heat required is pumped into the heating circuit. A third circuit is necessary if, in addition, a separate hot water tank is available. This is also fed via a regulating thermostat and a separate charge pump as needed with hot water. In the electrical control while a so-called priority circuit is used. This means that the electrical circuit is designed so that for the duration of the charging process, ie during operation of the charge pump for the hot water, the heating circuit pump is switched off. This ensures that there is always hot water in the budget. On the other hand falls a short-term shutdown of the heater circulation is not significant. It would also affect the thermal hydraulic particularly disadvantageous in a stratified storage tank, a double and simultaneous decrease of the hot water from the buffer memory.

For single normal-size ( well insulated ) buffer with 800-2000 l are sufficient.

Greenhouses

Greenhouses often have relatively large heat storage between 100 and 150 m3. In this case, the memory is in the daytime when the sun is heating the greenhouse is heated, which then transfers the heat in the interior at night of the greenhouse. Thus, during the day are used, the CO2 of the combustion for the growth of plants. The boiler power required is reduced by the buffer, as in extreme weather conditions (cold winter nights) provide buffer and boiler heat available.

These steel containers are usually designed as a layer storage systems. That is, cold water is drawn at the bottom of the buffer, and the heated water is then introduced in the upper region. In order not to mix the layers of water is designed as a pipe with many small holes over the entire length of the container, the forward and return run.

Heat pumps

For heat pumps, a buffer memory is not mandatory, but improves the seasonal performance factor. In particular buffer for heat pumps play a role in the question of load balancing potential of heat pumps in the power grid in the context of the energy transition.

Solar systems

Usual is a buffer for all-day use of solar energy. The warmth of the sun radiation is absorbed during the day is stored in buffer and at night given if required in the household by means of corresponding panels. Especially for low-energy houses the heating in the conventional sense is so unnecessary.

DHW heating

Buffer tank with integral DHW heating are also called combi storage (tank in tank solution). If the DHW heating in flow principle, one also speaks of a fresh water reservoir.