The importance of buffer tanks

The importance of accumulation tanks in heating in boilers with manual fuel supply - lump wood and wood briquettes

Until recently, before the use of accumulation tanks was common in the case of hot water boilers for wood and wood briquettes for central heating, the boilers were operated at a significantly lower output than their nominal output for the majority of the heating season. Such operation results in a number of negative phenomena such as a decrease in heating efficiency, tarring of the boiler, the release of a large amount of harmful emissions into the air, etc. All this then leads to an unnecessary increase in heating costs, deterioration of the environment, more laborious cleaning of the boiler, as well as a shortening of its service life. The main reason for such boiler operation is that, with a properly designed and installed nominal boiler output, in a period when the external temperature is higher than that corresponding to the thermal zone in which the heated object is located, in order to prevent overheating /excess heat generation/ of the object, the user most often reduces the output heating temperature of the water in the boiler below the optimal limit on the regulator or control valve. Considering the chemical composition of the fuel, the optimal operating temperature of the water in the boiler at the outlet is 75-85ºC, the return water temperature is min. 60-65ºC and the optimal fuel combustion temperature is 1000-1200ºC. Operating the boiler below these temperatures achieves the desired effect of reducing excess heat and not heating the household in the short term, but at the same time all the negative phenomena mentioned above occur. It is important to remember that during the heating season there are only a few days, or weeks when the outside temperatures are at the border of the given thermal zone, i.e. when all the heat produced during the operation of the boiler at its nominal output is actually used and consumed. Under these conditions, it is very common in practice that the boiler is operated in a temperature regime of 50-60ºC at the outlet and 30-40ºC at the return water, which is very inefficient and significantly harmful to the environment. When calculating the nominal output of the boiler, the design standards mainly take into account the thermal zone in which the heated object is located, its size, the degree of insulation, the nature of the object's use, etc. According to these criteria, the required installed nominal output of the boiler is then calculated. It should be such that the object can be reliably heated at the lowest outside temperatures of the given thermal zone. Most often, this temperature in our Central European climatic conditions ranges from -11 to -18ºC. In reality, however, such an outdoor temperature is only approximately 1/3 of the heating season, despite the fact that outdoor temperatures can drop to -20 or even -30ºC for a short time.

The ideal solution to eliminate this problem with different outdoor temperatures during the heating season is to install storage tanks in the heating system. During boiler operation, the excess heat generated is stored and accumulated in them, which is then used for heating. The boiler can thus be operated during the heating season at its rated output regardless of the outdoor temperature. This modern solution for heating comfort, depending on the installed boiler output and the volume of the storage tank, will ensure ecological heating, significantly save heating costs and, what is also important, will allow you to achieve thermal comfort not only for the whole night, but also during the day, if no one is at home. The minimum recommended volume of the storage tank is 55 liters/kW. However, to increase comfort, it is advisable to install an accumulation tank of 100 liters/kW, or even more, if the spatial conditions of the boiler room allow it. The purchase costs for larger accumulation tanks are negligible compared to the comfort and heating efficiency obtained. In such a case, it is also possible to choose a boiler with a reserve of nominal power, which shortens the time for charging-accumulating hot water into the accumulation tanks and at the same time the user avoids the risk of the household cooling down if he forgets to add fuel to the boiler, or is out of the household during the day. Depending on the volume of the accumulation tanks, it is possible to achieve heat accumulation for 10 or more hours.

In a heating system with a gasification boiler with a lambda probe and a sufficient accumulation volume, heating with wood and wood briquettes becomes not only an extremely effective form of heating, but also sufficiently comfortable. Our company offers such a solution with PYROGAS gasification boilers, which are equipped with a lambda probe, primary and secondary air servomotors, a robust refractory concrete combustion chamber ensuring the combustion process at temperatures of 1200ºC with an intelligent fully automatic electronic control system.

More information about these boilers and storage tanks can be found on our website under PRODUCTS. PYROGAS boilers, thanks to the optimization of the flue gas flow rate /ORS system/ and the optimization of the heat exchange surface with convectors, achieve an efficiency of over 91%. For example, the PYROGAS 26 boiler can also be operated at a power of 32kW, which ensures thermal comfort and storage comfort in frosts even if the user does not add fuel all day.

Including a storage tank in the heating system optimizes boiler operation, extends the boiler's service life, increases combustion efficiency and reduces fuel consumption.

During the boiler's service life, the investment costs for the storage tank will not only be returned, but will also allow significant savings in fuel and boiler maintenance costs.