It's getting warm: New wood chip heating system in operation at Kommunalservice Jena

With this project, Kommunalservice Jena was one step ahead of the times. Even before the calls to save energy became omnipresent last year due to the energy crisis and the demands to phase out fossil fuels as quickly as possible became more than loud, the municipal company had already started building a regenerative heating system that makes the use of gas almost superfluous.

"With this system, Kommunalservice is making optimum use of the available resources. It also underlines the fact that the city administration is not just talking about climate neutrality, but is setting a good example with very practical projects," emphasized Dr. Thomas Nitzsche, Lord Mayor of the City of Jena, at a press conference to mark the commissioning of the plant.

"We examined very thoroughly in advance which system was suitable for our specific requirements. Now that it has been in operation for the first few weeks - i.e. it has survived the test phase - we are more than satisfied," says KSJ plant manager Uwe Feige.

In the end, the choice fell on a 440 kW wood chip boiler. In addition, a 270 kW solar thermal system was installed on a vehicle hall as well as a 700 kW peak load gas boiler. The heat will be supplied to all existing buildings via a local heating network. In addition, a solar thermal system with buffer storage ensures the heat supply alone in the summer and transitional months. To ensure operational reliability, a gas boiler is available to cover high peak loads, for redundant supply or for maintenance or repair work. The system is fed with wood chips automatically. Two covered 30 m³ moving floor containers always supply the biomass boiler with sufficient fuel via the conveyor system. The new wood chip and solar thermal plant, which was built on the company premises at Löbstedter Straße 68, replaces three old gas heating systems via a newly built local heating network.

"Thanks to the system, KSJ will save more than 155 tons of CO2 per year. It will also replace around 900,000 kWh of gas per year. That's something to be proud of," says Christopher Helbig (KSJ), project manager of the wood chip system.

Background: The path from the idea to commissioning

The decisive factor for the implementation was the planned construction of a new administration building with a large sanitary wing for the commercial areas of the building depot. Historically, this site in the north of the city of Jena has developed into the central main site for the majority of the workforce, alongside a number of external sites. The approximately 44,000 m² site now houses two three-storey administration buildings, the workshop buildings for the vehicle fleet, four vehicle halls, a transshipment hall with sorting area and several building barracks with workshops, social areas and warehouses. Until the new administration building was constructed, these buildings were supplied with heat from three gas heating systems. With the additional new building, a fourth heating system would have had to be planned.

Another reason for the sustainable solution was not only the climate protection aspect, but also the landscaping material from the areas of tree and green space maintenance, as well as the recycling yards. At the time, this had to be transported to a recycling plant and disposed of for a fee. As part of the daily work, around 3,000 cubic meters (tree, shrub and branch cuttings) with an energy potential of ≈ 2.4 GWh are collected every year.

The preliminary planning phase then began with these basic considerations. First, the energy parameters were recorded, basic site considerations were made and a detailed market survey was started. As the material produced was to be utilized as it arrived, the wood chip boiler was designed with lower quality wood chips - high green and fine content - and for higher residual moisture. The system components were selected on the basis of these specifications. The plant went into operation on 23.01.2023 after a construction period of around 9 months and a planning period of around 3 years.