BM Retrofit

Modernisation concepts for biomass-based district heating networks

© Salzburg AG

Biomass-based district heating networks and systems play a central role in sustainable heat supply and comprise about 2,400 systems in operation in Austria. Currently, there is an increased need for retrofitting and modernisation of many heating networks in operation in order to meet future technical, economic and regulatory challenges as well as a sustainable and targeted expansion.

In BM Retrofit, innovative technical concepts (e.g. flue gas condensation, heat pumps, storage technologies) are developed accordingly and optimised for efficient system integration. This ensures that innovative measures are further improved and integrated, leading to more sustainable and economical operation in conjunction with reduced resource consumption and emission savings.


The objective of the project is to, a) adapt and further develop existing heating networks to future requirements, b) to make a significant contribution to achieving the climate targets set and c) strengthen the economic benefits including local value creation.

System integration in combination with comprehensive involvement of relevant actors coupled with the expansion of services and business models is currently not applied in practice in the development of modernisation concepts. The existing potentials are therefore not fully exploited.

Approach and methodology

In order to achieve the goals set, a holistic methodological approach is pursued and measures are implemented at various levels. These include technical measures (e.g. optimisation of biomass boilers as well as the heating network, use of secondary and efficiency-enhancing technologies, integration of renewable energy sources and waste heat, etc.), systemic elements such as advancing digitalisation (e.g. intelligent sensor technology, new control concepts and deployment sequencing) or the strategic planning of grid expansion and densification with the help of energy space planning, as well as non-technical/organisational measures (e.g. actor involvement and stakeholder management, comprehensive innovative system evaluations and life cycle and value creation analyses) and subsequently economic aspects (e.g. business and billing models).

The BM Retrofit approach thus enables the realisation of a sustainable overall energy system. a) with increased overall efficiency and flexibility, b) with best possible use of renewable and local energy sources, c) with full exploitation of synergies of existing infrastructures and d) with the creation of a future-proof and resilient system. This results in a significant reduction in greenhouse gas emissions and resource consumption, as well as an increase in security of supply and economic efficiency.

Testing of the elements and solutions in a real environment

The developed elements and solutions will be implemented in different biomass-based district heating networks and analyzed with accompanying data evaluation and holistic system validations including life cycle and value chain analysis. The identified optimization potentials and experiences from the entire innovation process are summarized as best practices in a guide. The technical, economic and ecological advantages are shown quantitatively. Furthermore, scaling scenarios will be developed to generate and evaluate the market potential and impacts for the energy system.

In the first project phase, the Wald im Pinzgau heating network was identified as a suitable demonstrator. Modernization takes place in a two-stage process. The first phase, which started in the fall of 2023, includes measures to optimize summer operations by integrating local waste heat and to increase flexibilities. A combination of technologies is planned for this purpose, as well as sector coupling for waste heat utilization. Here, waste heat from the cooling circuit of the nearby hydropower plant is tapped for the heating network by means of an innovative heat pump concept with a thermal output of around 250 kW. A thermal storage tank with about 30m³ incl. appropriate storage management helps to increase flexibility. Renewable electricity generated directly on site from the hydropower plant is used to operate the heat pump.

In the second project phase, a bundle of measures for the modernization and optimization of the biomass boiler operation (retrofitting of flue gas recirculation, combustion air control, etc.) as well as a superordinate control strategy with an intelligent energy management system (model predictive control using yield and load forecasts) for the optimized operation of the heating network or for network control will be implemented and demonstrated. This means that the future heat supply will be provided by 100 percent renewable and local heat sources (biomass and waste heat) and the fossil oil boiler will only be used as a reserve and for emergencies. This direct substitution can achieve annual savings of around 100,000 kWh oil/a and a CO2 reduction of around 30 tons. In addition, the total biomass consumption can be reduced enormously by the optimized operation of the biomass boiler in combination with waste heat recovery.


Joachim Kelz
T: +43 (0)3112 5886-236

Project key facts

01.02.2023 - 31.01.2026

funding program
Flagship region Energy

Project type
Cooperation project experimental development

Project budget
2.011.803 €

Project management

AEE - Institut für Nachhaltige Technologien

The following model solutions are being developed in the BM Retrofit project:

Sample solution/s under development

Media reports on the project