The maintenance of greenery, trimming trees or cutting down a forest produces large amounts of waste. However, branches can be pulverized into the so called chips. This material can be used for heating in the boiler, but because it contains a lot of water, its drying consumes large amounts of energy. Thus, the efficiency is very small, the combustion efficiency in a conventional boiler reaches barely 40 %.

The university team has found a way to heat with wet chips with significantly higher efficiency of almost 100 %. They put together a model of the boiler, whose essential part is the condensing heat exchanger. The boiler uses the condensation heat of the steam contained in the flue gas and at the same time, it meets the required legislative limits. The total size of the boiler is not much larger than that of standard boilers of a similar performance, its design allows for variable installation. The device is also suitable for use in two-circuit heating systems, e.g. floor and radiator heating.

However, wet chips are not very suitable quality fuel, it does not have a high calorific value. The price of fuel biomass is still growing and it can be expected that the pressure on the use of waste biomass, i.e. also wet chips, will increase. Especially in large agricultural operations, gardening companies, or in technical services of cities this type of combustion is worthwhile. Chips can be obtained from many different types of biological waste. Therefore, piles of leaves from beets do not have to lie waste, and at the start of the heating period, they may be used as fuel in the fresh state. Although the acquisition price of the boiler is about a third higher than the price of a standard boiler, the operating costs will soon return by using fuel “for free”. Moreover, places with the animal breeding and production are heated all year round. We do not need to wait for the winter.

The university team had the new boiler patented and they are currently cooperating with a network of manufacturers of heating equipment. Because it is unique in the European context, they are considering the sale of licenses abroad.

Energy Research Centre, VŠB-TUO