How buffer storage tank works

The principle of operation of a buffer storage tank is based on the use of the high heat capacity of water. For example, 1 liter of water that has cooled by 1°C can heat 1 m³ of air by 4°C.

Let's consider the principle of operation of a buffer storage tank using the example of the simplest design without a built-in heat exchanger, an additional tank for heating water, or other devices. Such a buffer storage tank consists of a container with four pipes, two of which are located in the upper and two in the lower part of the tank. The heat source will be a solid fuel boiler, and the consumer will be the heating system.

The supply pipeline from the solid fuel boiler is connected to the upper nozzle, and the return pipeline is connected to the lower nozzle of the buffer storage tank. A circulation pump is installed in the return pipeline of the heating system, which draws water from the tank. After turning on the circulation pump and igniting the boiler, the pump takes cold water from the bottom of the buffer storage tank and directs it to the boiler, while the hot water coming out of the boiler goes to the upper part of the tank. Hot water is lighter than cold water, so there is no intense mixing of water in the tank, and the pump takes cold water from the bottom of the tank until the entire tank is filled with hot water. In the case of a solid fuel boiler, the volume of the buffer storage tank is calculated so that it is sufficient to accumulate the heat generated by the combustion of a single fuel load.

After the fuel has burned, the storage tank is filled with hot water. The thermal insulation of the tank allows the water to be kept hot for several hours or even a day, so the heat obtained in the evening can be used throughout the night or only in the morning. At the time of heat consumption, we have a full tank of hot water.

The second upper nozzle is connected to the supply pipeline, and the second lower nozzle is connected to the return pipeline of the heating system. A pump installed in the return pipeline of the heating system supplies water to the tank and forms a second circulation loop. The supply of cooled water from the lower part of the heating system displaces hot water from the upper part of the buffer storage tank into the supply pipeline. Since cold water is heavier than hot water, there is no intense mixing of water in the tank, and the cold water remains in the lower part of the tank. Therefore, until the cold water fills the entire volume of the buffer storage tank, the heating system will receive hot water.

The operating time of the heating system on accumulated heat depends on the power of the system and the volume of the tank. Therefore, when choosing a buffer storage tank, it is necessary to determine which of the conditions is more important: to provide heating to the system of a certain power for a certain time or to provide accumulation of heat from a source of a certain power for a certain time.