Heat accumulators

How does the heat accumulator work?

The most common is the use of tanks-accumulators of heat with capacity of 300-2000 liters, used in systems with natural and forced circulation. In the simplest configuration, a heat accumulator – it is a vertical steel tank with height 3-5 times more than the diameter for provision of temperature stratification of water. Through the height of tank are placed fitting pipes for supply and drainage of water, as well as for mounting of electric heaters.

Water with the highest temperature accumulates in the upper part of the tank and can be discharged through the upper fitting pipes for heating by radiators; less heated water (central section of the tank) can be discharged by fitting pipes of central level for heating by underfloor heating. The inner surface of the tank does not need protection against corrosion, since in heating systems is constantly used the same water that eventually becomes “neutral”. To reduce heat loss through the walls of the tank, it must be isolated, for example, with heat-resistant foam with thickness up to 100 mm.

The accumulation tank may contain horizontal partitions, separating it into sections with different temperature levels in height. To some extent, this improves the efficiency of heat accumulation. It can also be equipped with inspection flange.

Steel heat exchanger is placed at the bottom of the tank to connect to the heat supply system of solar collectors. This location provides the opportunity of work of collector contour at the lowest possible temperatures with maximum efficiency.

A small tank (50-100 l) is placed in the upper part of the accumulation tank traditionally for preparation of hot drinking water. This reservoir is completely surrounded by hot water, which leads to rapid heat transfer to water. This raises the probability of reproduction of legionella, requiring additional costs for means of protection. An alternative is to use a heat exchanger, made of food-grade stainless steel. In this case the storage tank works as flow water heater. The heat exchanger contains the minimum amount of water, which reduces the likelihood of formation of legionella. Small capacity does not mean low efficiency. Large area of heating and heat supply in the accumulator allow to instantly heat the flow of cold water to the desired temperature.

Maximum temperature of heat accumulators does not exceed 95°C. Technical requirements for boilers also determine that the highest temperature is 95°C. The size and temperature conditions of heating elements, provided for use, is very important factor in placing in your house heat buffer storage system. Experience shows that the biggest effect of accumulators will be achieved in the system of low temperature. The system with heat accumulator will function better in a house heated with underfloor heating.

What are the advantages of buffer tank?

Firewood contain many different substances, including tar, acids, etc., which are released at incandescing of firewood. To ensure the qualitative burning of these substances, the boiler is required to operate at full capacity, and this can be achieved by the creation of the heat supply system with heat accumulators. Control mechanism of capacity of many solid fuel boilers is focused on incomplete combustion or smoldering of fuel. In conventional boilers this operation performs regulator of traction – air valve that is opened by a chain and at a certain temperature is closed. Thus, oxygen is not supplied to fuel, but it is incandescent and various volatile substances are released from it that would burn in other circumstances.

In Western Europe, the fixation of buffer tank with a wood boiler is required. Buffer tank is not only economical, but also due to complete combustion prevents clogging of chimney with tar sets.

Therefore, the installation of heat accumulator is recommended to plan at the stage of constructioning the house. Otherwise, the desire to mount it may not coincide with the technical capabilities of the fuel room due to lack of space.

What is a heat accumulator?

Heat accumulator – it is a vertical cylindrical steel tank, height of which is typically 3-5 times bigger than its diameter. Heat accumulators have insulation from heat-resistant foam to reduce heat loss. Heat accumulators are used to collect heat from different generators for use in heating and water supply systems if necessary.

The main function of heat accumulator is storing energy from various heat sources and further distribution in heating and water supply systems.

Heat accumulators have many different names – accumulating tank, buffer tank, buffer storage, storage tank of heat.

Advantages of heat accumulators

The main advantage of heat accumulator is that it prevents the loss of heat energy in heating and water supply systems, allowing to accumulate excess heat, to store it for some period of time (up to six days) and, if necessary, to use for the needs of consumers. The use of heat accumulator makes it possible to simultaneously give a large amount of previously accumulated thermal energy, which is difficult for boilers.

Heat accumulator allows to use the heat, the source of which is temporarily available, in the most efficient way. For example, the heat from solid fuel boilers is available until firewood are burning; sun heat can be used only on a sunny day, and the energy from heat pump or electric boiler should be used at night, when electricity tariff is reduced. Thus, a heat accumulator can correctly adjust the processes of generation and use of thermal energy by time, power and temperature.

The principle of work of heat accumulator

During its work, a heat generator gives energy to tank-heat accumulator (charging process) from which heat is used in heat supply system to maintain the required room temperature (discharge process).

Heat accumulator – is the heart of modern combined heat supply system, in which are used several heat sources. Thus, depending on the model of heat accumulator, it can simultaneously connect low-temperature (heat pumps, condensing boilers, solar collectors) and high-temperature (solid fuel, electric, traditional boilers) heat sources.

Capacity of heat accumulator

Heat power (W), which can be accumulated in heat accumulator of capacitive type, is determined by the formula:

Q = mc_p(T₂-T₁)

where m — mass of heat accumulating substance, kg;
c_p — specific isobar heat capacity of substance, W:(kg*K);
T₂ і T₁ — average value of initial and final temperature of substance, °C.