This site is currently under development.
Skip to content
--- cover-image: https://raw.githubusercontent.com/GTIF-Austria/public-assets/refs/heads/main/assets/thumbnails/klien_data/Waste%20heat.jpg
domain: Energy Transition tags: KLIEN,renewable energy,energy potential,energy technology,excess heat,ambient heat provider: AEE INTEC,AIT Center for Energy,
Excess Heat Potential – Study on Renewable Energy Potentials
Background
Industrial processes as well as municipal wastewater treatment plants constitute significant sources of excess heat that have thus far been only partially exploited. This heat is available at different temperature levels and (depending on the source temperature) can be fed into heating networks either directly or via heat pumps. While the direct use of excess heat is already technically established, the substantial potential of low-temperature excess heat (<50°C) from industry, commerce, and wastewater remains largely unused.Methodology
The following sections provide only a condensed overview of the methodological concept used for calculating shallow geothermal energy and groundwater potentials. A comprehensive and fully detailed description of all methodological steps, assumptions, and data sources can be found in the full report.Definition and Scope
The methodological approach consists of two main steps. First, technical potentials were assessed using either bottom up or top down methods, depending on the characteristics of the industrial segment. Second, temperature levels were classified into two categories: heat at or above 50°C, which can be used directly (e.g., via heat exchangers), and heat below 50°C, which requires upgrading through large scale heat pumps. The temperature differentiated results also apply to anergy networks, as a temperature lift is generally needed at some point in any such system, regardless of its specific design. The conversion of excess heat energy into thermal capacity is based on an assumed 4,000 full-load hours (FLH) per year.Limitation and Constraints
Technical suitability of excess heat utilisation is further restricted by spatial criteria. Only those areas located within an allowable routing distance are considered. The identification of feasible routing corridors was based solely on spatial proximity to existing or planned district heating networks. Legal, topographical, or environmental protection constraints (e.g., Natura 2000 sites, water protection zones, pipeline crossings) were not considered in the modelling. Furthermore, only district heating demands within the same municipality were taken into account. Potentials that could be realised through inter-municipal utilisation of surplus excess heat are therefore not included in the present assessment. The potentials reported here thus represent conservative estimates, which could be increased in cases where coordinated infrastructure solutions are implemented. The dynamic development of new heat sinks and district heating networks was incorporated using the heat demand scenarios of the Austrian Heat Map.Industrial excess heat
The utilisation of industrial excess heat above 50°C for direct integration into district heating systems is technically well established. According to NEA 2023 [2], 9,2% of district heating already originated from industrial excess heat in 2020 [3]. In contrast, the use of low-temperature excess heat via heat pumps is still at an early stage of development.Methodology and Data Basis
The data basis is derived from the project INXS – Industrial Excess Heat (2021–2023) [3], supplemented by the sector scenario Pathway of Industry (NEFI) [4], which provides projections for 2030 and 2040. Depending on the industrial segment, the following methodological approaches were applied in line with [5]:
- Bottom-up for energy-intensive facilities (data from environmental reports, EMAS, etc.)
- Top-down for energy-extensive sectors (derived from statistical data and standardised energy indicators)
Theoretical Potential
The theoretical potential corresponds to the total site-specific excess heat available, derived from the energy consumption of industrial processes using the following steps:Compilation of industrial energy consumption (by energy carrier),
Identification of waste-heat-relevant processes (including cooling systems, flue gases, mechanical losses),
Application of typical loss and recovery factors,
Allocation to temperature levels and source types.
- Direct use (≥50°C): Injection of excess heat into the district heating network without additional temperature lifting, e.g., via heat exchangers.
- Heat pump utilisation (<50°C): Raising the temperature level using central large-scale compression heat pumps prior to injection into the district heating network.
Technical Potential
To calculate the technical potential, the theoretical potential is limited by two constraints:Maximum distance to the next district heating network: Spatial modelling of excess heat is supplemented by a GIS-based calculation of a maximum routing distance to the next district heating network.
Maximum coverage shares: To represent the Low–Medium–High ranges of possible expansion pathways for 2030 and 2040, maximum coverage shares of district heating demand are defined for each utilisation pathway (Table 1).
Table 1 Maximum Coverage Shares of Excess Heat in District Heating Networks
Realisable Potential
The realizable potential could not be quantified in a generic manner for two reasons. First, although several installations are already in operation and others are under construction, their number is still too limited to apply a market penetration model based on an S curve. Second, heat recovery projects depend heavily on project specific boundary conditions, which must be assessed individually for each case.Excess Heat from Wastewater Treatment Plants
Wastewater treatment plants provide predictable, stationary, and continuously available heat sources that can be effectively utilised through heat pumps. However, current utilisation levels remain marginal.Methodology and Data Basis
For each wastewater treatment plant, annual wastewater volumes were obtained from the EEA database (Waterbase 2019) [7]. Projections for 2030 and 2040 were derived proportionally from population development according to the ÖROK population forecast at the NUTS-3 regional level. The calculation follows a bottom-up approach based on publicly available data. No validation with individual plant operators was conducted; consequently, the accuracy depends on the underlying data quality.Theoretical Potential
The theoretical potential corresponds to the total site-specific excess heat available. At this stage, neither spatial constraints (e.g., maximum pipeline distances) nor system-level limitations (e.g., maximum coverage shares) are considered. The theoretically maximum usable excess heat potential at the municipal level is capped by the local district heating demand. In addition, a theoretical potential not constrained by municipal-level heat demand is provided, which is relevant for regional or inter-municipal district heating systems.Technical Potential
The calculation of technical potential is based on the following assumptions:- Temperature profile: summer 20°C / winter 10°C
- Temperature drop: average 5 K (cooling)
- Reduction factor (e.g., due to stormwater dilution): 30%
Realisable Potential
The realizable potential could not be quantified in a generic manner for two reasons. First, although several installations are already in operation and others are under construction, their number is still too limited to apply a market penetration model based on an S curve. Second, heat recovery projects depend heavily on project specific boundary conditions, which must be assessed individually for each case.Results
The technical potential incorporates the upper coverage limits of district heating demand across three bands (low–medium–high) as well as maximum pipeline distances to district heating networks. The modelling also accounts for changes in district heating demand toward 2030 and 2040 according to the WEM (With Existing Measures) 2023 heat demand scenario, as well as expected reductions in high-temperature industrial excess heat due to energy efficiency measures.Direct Use of Industrial Excess Heat (≥50°C)
The direct utilization of industrial excess heat at higher temperatures (≥50°C) is technically established and comparatively well exploited in Austria. As early as 2020, approximately 1.75 TWh/a of industrial excess heat was fed into district heating networks with a combined connection capacity of roughly 580 MW [1]. Based on a regionally differentiated starting value derived from the model, the technical potential for directly utilized excess heat for feeding into district heating systems amounts to up to 3.4 TWh/a in 2030 and 3.6 TWh/a in 2040. The theoretical potentials listed in (7.2 GWh/a) represent the total industrial excess heat potential in 2040 at temperatures ≥50°C, without considering recoverability. When these excess heat potentials are restricted by municipal-level district heating demand, the value decreases to 4.6 GWh/a. However, this calculation does not account for the possibility of utilizing excess heat across municipal boundaries via district heating, provided that suitable heat sinks can be accessed.
Figure 1 Temporal Evolution of Technical Potentials for Industrial Excess Heat Utilized Directly
Figure 2 Identified Energy Potentials for Directly Utilized Industrial Excess Heat
Austria GTIF - Direct Utilization of Industrial Excess Heat (≥50°C) Potential
Low-Temperature Excess Heat (<50°C) from Industry, Commerce, and Wastewater Treatment Plants
At present, the direct utilization of industrial excess heat at higher temperatures (≥50°C) is technically well established and comparatively well exploited. In contrast, the potential associated with low-temperature excess heat (<50°C) remains largely untapped. Across Austria, the technical potential for low-temperature excess heat (<50°C) amounts to up to 5.0 TWh/a in 2030 and 5.7 TWh/a in 2040. The figures presented below encompass the identified low-temperature excess heat potentials from industry and commerce as well as from wastewater treatment plants. Wastewater treatment plants account for approximately 20% of this potential.
Figure 3 Technical Potential of Low-Temperature Excess Heat (<50°C) from Industry, Commerce, and Wastewater Treatment Plants for 2030 and 2040
Austria GTIF - Low-Temperature Excess Heat (<50°C) Potential
Low-temperature excess heat from industry and wastewater treatment plants can play a significant role in the decarbonization of the heating sector, particularly when combined with network-based heat supply systems.Assessment of the Results
Excess heat represents a strategically significant heat source, particularly when combined with district heating networks and heat pumps. The technical potential of up to 8.4 TWh by 2030 and 9.4 TWh by 2040 underscores the high importance of this resource. The spatial distribution of these potentials is concentrated in industrial centres and urban areas with existing network-based infrastructure and high heat demand density. Table 2 presents the consolidated technical potentials by utilization pathway:Table 2 Summary of Technical Excess Heat Potentials for Various Utilization Pathways
Estimation of Realizable Potential (Expert Assessment)
Excess Heat from Wastewater Treatment Plants (Heat Pump Utilization)
Current implementations—for example in Gleisdorf (800 kW, operational since 2023), Vienna (55 MW, operational since 2023), and Graz (in the permitting process)—demonstrate that the technical potential associated with wastewater holds a high likelihood of realization. Contributing factors include the typically short distances to major heat demand centres, the favourable scaling between wastewater volumes and heat availability, and the already accounted-for spatial suitability embedded in the technical potential. Barriers primarily relate to comparatively small plant capacities, which must remain economically viable despite high investment shares for screens, filters, wastewater heat exchangers, heat pumps, and pipelines. Additional challenges arise from water law requirements and seasonal fluctuations, for instance in tourism regions. Overall, from today’s perspective, a realization rate of 60–80% of the technical potentials appears plausible.Industrial Excess Heat (Direct Utilization and Heat Pump Utilization)
Industrial excess heat exhibits strong spatial concentration—particularly in the Mur–Mürz corridor, the Inn and Rhine valleys, and the metropolitan regions of Linz, Graz, and Vienna—and is highly dependent on industrial and economic developments. The technical potential was therefore derived through spatial modelling that accounts for heat demand densities, distance limitations, and infrastructural factors. The assumed upper limit for transmission distances (e.g., approximately 12 km for 100 MW) is conservative, as current projects in the Aichfeld region and in Graz already illustrate. The underlying INXS study identifies a total technical excess heat potential of 34.3 TWh/a without applying spatial constraints. Under the methodology used here, this value decreases to 9.4 TWh/a by 2040, following the application of spatial (maximum pipeline distance) and systemic (coverage limit) restrictions. ##### Assessment of Utilization PathwaysDirect Utilization of Industrial Excess Heat (≥50°C)
Direct utilization demonstrates a high level of technological maturity, low system complexity, and strong spatial alignment with existing and planned district heating networks. At present, approximately 1.6 TWh/a are already in use, corresponding to roughly 43% of the technical potential. By 2040, a technical potential of 3.6 TWh/a is projected. Experts estimate that 70–90% of this potential is realizable. This corresponds to a realizable potential of approximately 2.2–3.3 TWh/a by 2040.Heat Pump Utilization of Low-Temperature Excess Heat (<50°C)
The technical potential for low-temperature excess heat amounts to 5.7 TWh/a by 2040, yet its exploitation is more challenging due to site-specific conditions. Contributing factors include dependence on suitable heat sinks, higher system complexity, and limited project experience and business models. For wastewater treatment plants, the realizability is estimated at 60–80%, substantially higher than for industrial low-temperature excess heat, which is assessed at 30–50% due to process constraints, spatial characteristics, and thermal interactions. In total, under current framework conditions, this corresponds to a realizable share of 35–55%, or 1.7–3.2 TWh/a by 2040. In the medium to long term, the expansion of anergy and low-temperature district heating networks could substantially enhance the feasibility of utilizing these potentials. Table 3 summarizes the realizable potentials (based on qualitative expert assessment) by utilization pathway.Table 3 Qualitative Classification of Realizable Excess Heat Potentials for Various Utilization Pathways
Summary
Excess heat is a key resource in the transformation of network-based heat supply systems. The technical potential amounts to up to 9.4 TWh/a by 2040, with varying degrees of realizability depending on the specific utilization pathway. Overall, a realizable potential of approximately 4.0–6.5 TWh/a can be derived. These values represent qualitative expert assessments and do not substitute for detailed project-level or site-specific analyses.References
[1] W. Gruber-Glatzl, „Abwärmekataster III Steiermark,“ 2021. [Online]. Available: https://tinyurl.com/ffyjs6pn. [Zugriff am 29 03 2024].
[2] Statistik Austria, Nutzenergieanalyse 2023, Wien, 2024.
[3] A. Hammer, E. Lachner, T. Kienberger, W. Gruber-Glatzl, J. Pfleger, A. Stöger, S. Reuter, R.-R. Schmidt, S. Moser und G. Jauschnik, „Industrial Excess Heat – INXS: Erhebung industrieller Abwärmepotenziale in Österreich,“ Klima- und Energiefonds der österreichischen Bundesregierung, Wien, 2023.
[4] V. Alton, P. Binderbauer, R. Cvetkovska, G. Drexler-Schmid, B. Gahleitner, R. Geyer, A. Hainoun, P. Nagovnak, T. Kienberger, M. Rahnama-Mobarakeh, C. Schützenhofer und S. Stortecky, „Pathway to industrial decarbonisation - Scenarios for the development of the industrial sector in Austria,“ NEFI - New Energy for Industry, Wien, 2022
[5] Hammer, A., Lachner, E., Kienberger, T., Gruber-Glatzl, W., Reuter, S., & Hummel, M., „Survey of Industrial Excess Heat Potentials in Austria,“ in International Sustainable Energy Conference - Proceedings, 1, 2024
[6] Austrian Heat Map,“ 2024. [Online]. Available: https://austrian-heatmap.gv.at/karte/. [Zugriff am 25 03 2024].
[7] Urban Waste Water Treatment Directive, Waterbase reported under UWWTD data call 2019, 2021 (Tabular data).