Solid Fuel Boilers
The economic and political situation in the world has a direct impact on the formation of prices and conditions for the supply to Ukraine of energy carriers from other countries and, thus, on the energy safety of the country. Decreasing Ukraine’s dependence on natural gas imports and the eventual and total elimination of natural gas use are possible if alternative energy sources (AES) are actively used.
Natural gas for heating can be substituted with biomass (wood, peat, chips, pellets, etc.). There are some conditions that would enable the introduction of solid fuel boilers and fireplaces, should be addressed for obtaining maximum effect from transition to solid fuel not only nation-wide but also for every consumer.
Water Circuit Fireplace
Biomass is a locally-sourced fuel. Its cost depends directly on its accessibility for use because long-distance biomass transportation is not economically feasible.
Types of biomass as alternative fuels: wood, pellets, peat briquettes
Natural gas is usually replaced as a fuel if there is a less expensive alternative. But the presence of a heating system is equally important. There are only two options when it comes to switching to AES, namely, reconstructing the available heating system, and new construction.
Reconstruction of Available Heating System
The most common situation is that there is a heating system in place already with a gas boiler as a heat source. In this case, for maximum economic effect, one should consider as only solid fuel boilers using wood. Installing boilers with an automatic fuel feed is economically unfeasible because of the long payback period for this expensive equipment.
What to pay attention to before purchasing a solid fuel boiler:
1. Ability to build a separate chimney pipe with minimal expense and minimal destruction of the building load-bearing structures.
If a solid fuel boiler was not envisaged during construction of the house, usually there is no free ventilation shaft for the placement of the chimney pipe. If there is one, the condition of the shaft and its cross section must be inspected and a lining is mandatory (installation of a protective sleeve, for example, in the form of a stainless steel pipe). Another option for the chimney pipe would be to run it on the outside building wall. All the pipes located outside must be insulated (so called “sandwich pipes”), otherwise there will be no pull in the chimney pipe.
The steel grade and thickness have an impact on chimney pipe durability. It is recommended to use stainless steel of grades AISI 304, 321. The first 3-4 m of the chimney pipe must be 1 mm thick.
This phase is very important, and as such it requires a preliminary assessment of its cost and labor input.
2. Availability of free space in the boiler room for the installation of the solid fuel boiler and auxiliary equipment.
Solid fuel boilers have the highest efficiency rate (70-80%) when operated with a full load and with a heat carrier output temperature on the level of +70-85°С. Taking into account the uneven heat load of the buildings during the heating season, this operation mode can be ensured through installing a heat accumulator (buffer tank) of about 20-25 l per 1 kW of boiler capacity. Therefore, a 20 kW boiler will require about 400 l tank volume with the following size: height – 1,500 mm; diameter (without insulation) – 600 mm.
Solid fuel boiler with manual fuel feed
In order to prevent condensate from appearing and quickly slagging the boiler, the reverse line temperature must not be lower than +55-60 °С (with mechanical or electronic thermostat).
3. Ability to create a storage place for fuel and easy access to it both from outdoors and from the boiler room.
Solid fuel (for instance, wood) takes up a quite significant volume. Mmaking a storage place, it is necessary to find a place, and this may be a problem if your land plot size is small.
4. It is expedient to install a weather-based temperature control for the heat carrier supplied from the buffer tank to the building heating system, and to ensure correct that the boilers work in parallel, so that after wood burn out and tank cooling, the gas boiler turns on automatically and ensures the desired indoor air temperature.
Four-way weather-based control valve (shown without control mechanism) and heating system circulation pump
5. For the boiler to work safely, it is necessary to envisage measures for preventing boiler overheating.
Fulfilling all the above conditions will to save up to 30% of funds compared to gas heating. Electricity consumption is minimal, as it is required only for the operation of the circulation pumps. The key disadvantage of this boiler is the manual fuel feed.
New construction
In case of a new construction, all the above conditions can be ensured in the initial work phases. Converting from gas heating to a solid fuel boiler will create no difficulties for the consumers. In addition, one should analyze carefully the possibility of installing a pellet boiler which operates in an automatic fuel and air feed mode and has a weather-based control mode. With this, the optimum fuel-air mix is achieved.
In operating mode, the maximum electricity consumption by a household solid fuel boiler is about 300 W. Auto ignition is the exception, as a short-duration (couple of seconds) electricity consumption on the level of 1,000 W is possible. Thus, the solid fuel boiler creates no “burden” for the electric network. The efficiency rate of the boilers is on the level of 85-90%. Under the current natural gas tariffs and cost of fuel, operating expenses for heating with a pellet boiler are 5-7% lower than a gas boiler.
Pellet boiler with bunker (30 and 90 kW)
It should be concluded that heating without gas is absolutely possible, and that solid fuel boilers are one of realistic alternatives to gas boilers. Solid fuel boilers in private houses may ensure a comfortable indoor air temperature and heating of hot water for sanitary and hygienic needs. The more Ukrainians who switch from using predominantly imported natural gas in favor of local biomass, the higher the chances of the country becoming self-sustainable in the matters of energy supply, as well as becoming more independent in general.
