The industrial waste heat (WH) potential within a given industrial sector is quantitatively assessed using a methodology that correlates waste heat generation with specific industrial activities and employment figures. This approach initially utilizes coefficients (MWh/year/employee) that are uniquely defined for each NACE code (More information in: Sectors Classification), reflecting the typical waste heat intensity of different industrial processes. 


The total waste heat potential is primarily estimated by multiplying these activity-specific coefficients by the corresponding number of employees. This calculation method is adopted from the framework started by Huang et al. (2015), which provides aggregated data for a wide array of industrial sectors, and later completed by Aalborg University in the context of the Danish Heat Plan 2021. In particular, Huang et al. (2015) provides a WH estimate for Denmark by industrial sector and by process1. These data were later enhanced by Aalborg University in combination with Danish statistics on single companies, including ranges with the number of employees for each site. Results were reported at the SDEWES conference 20212 and provided the basis to build an online map for the Danish Heat Plan for 20213. Combining all these data, Aalborg University was able to identify specific coefficients estimating the yearly WH amount per employee (e.g., MWh/(y⋅employee)) by industrial sector. These data are now freely available online within the aforementioned map. Knowing these WH coefficient, the mapping work consists in locating companies in the considered area and retrieving their industrial sector and number of employees. These data are not particularly sensitive and in most countries can be obtained (possibly purchased) by the local chamber of commerce. In HeatMineDH, this was the main adopted approach, combined with company data already available to case study partners.


While this employee-based coefficient method provides a valuable macro-level estimation – useful for an initial screening and a broad potential identification across a diverse range of industries where detailed thermal energy balances are not readily available – it is acknowledged that this approach only offers a generalized approximation rather than a precise, facility-specific quantification of heat potential. Its primary utility lies in enabling a first-order assessment of potential without requiring extensive site-specific energy audits at this project stage.


To further define industrial waste heat and its specific heat generation profiles, and as emphasized by Huang et al. (2015), the characteristics of waste heat are highly dependent on the type of industry and its specific processes. Waste heat can originate from various sources, including exhaust gases, cooling water, hot products, and flue gases, with distinct temperature and flow profiles. For instance, high-temperature processes in the iron and steel or cement industries generate different waste heat streams compared to lower-temperature processes prevalent in food and beverage or textile industries.


The categorization of industrial waste heat into distinct temperature ranges is crucial for determining appropriate recovery technologies and assessing economic viability. Industrial waste heat is often categorized into broad ranges, also relevant for cogeneration applications. These ranges typically distinguish among low-temperature WH, medium-temperature WH, and high-temperature WH.

  • Low-temperature WH typically includes waste heat from cooling water, exhaust air from drying processes, and heat rejected from refrigeration systems. It is often suitable for preheating applications, space heating, domestic hot water production, or upgrading via heat pumps to higher temperatures for other uses. 
  • Medium-temperature WH often originates from flue gases, steam condensates, and process fluids. Technologies like absorption chillers or Organic Rankine Cycle (ORC) systems for power generation can already be applied in this range, though with limited economic profitability. 
  • High-temperature WH includes waste heat from high-temperature furnaces, kilns, and smelters and is in principle ideal for direct use in other processes, preheating combustion air, or high-pressure steam generation for power production.


Precise information regarding the temperature of the waste heat is important, as it directly dictates the selection of appropriate heat recovery technologies, influences capital and operational costs, and critically impacts the financial viability of heat recovery projects. Huang et al. (2015) offers a rather detailed temperature categorization, guided by technological considerations, ensuring a more robust and actionable assessment of industrial waste heat potential.


Temperature categories are critical for technology selection and financial viability. For low-temperature waste heat, heat pumps with a coefficient of performance (COP) of 3.5–4.5 are suitable, with capital costs of €500–800/kW. Medium-temperature heat supports ORC systems (€1,000–1,500/kW), while high-temperature heat enables steam turbines (€800–1,200/kW), see ReUseHeat (2018), IEA DHC (2020). These cost estimates, based on sources like the Danish Energy Agency catalogue and industry benchmarks, are indicative and will be refined in HeatMineDH WP4’s financial analyses, also including more recent cost estimates, or rescaling to present values according to inflation, or adaptation to different countries.


In order to build industrial Waste Heat maps, the WH sectorial coefficients need to be combined with local company data. The required information consists in the company address or position, the company NACE code (industrial sector), and the number of employees. These data can be typically bought from local chambers of commerce. Within HeatMineDH, a mixed approach was used: chamber of commerce data was purchased for the Italian case, while data collected from local partners and utilities was used for other countries. For further information on category grouping for industrial sector, visit Sectors Classification section. 


The adopted approach is acceptable to estimate orders of magnitude of the available WH and to quickly identify most interesting opportunities, but its accuracy is not sufficient to plan heat recovery measures in detail. A similar approach, though based on a more restricted set of WH coefficients developed by AIT using Austrian industrial data, was partially validated in the previous project "MEMPHIS2.0" (funded by IEA-DHC Annex XIII) by comparing WH estimates with data provided by four companies (printing, dairy, steel, and automotive sectors).


Footnotes

[1] See Table 3 of Huang et al. (2015) for Danish WH values by sector and process. Fig. 4 in the same report also provides temperature ranges for the different considered processes. 


[2] D. Moreno et al., “A Sectorial and Process-Based GIS Methodology for Mapping Denmark’s Industrial Excess Heat Potential for 3DH and 4DH Systems“, SDEWES Conference 2021, Dubrovnik. 


[3] Varmeplan Danmark 2021 (in Danish). Available at https://energymaps.plan.aau.dk (map) and https://danskfjernvarme.dk/media/0uqkycor/varmeplan_danmark_2021_baggrundsrapport_oktober-2021.pdf (report). Visited May 2026. 


References

Huang, B., Bühler, F., & Holm, F. M. 2015. Industrial Energy Mapping: THERMCYC WP6. Technical University of Denmark 


ReUseHeat (2018). Urban Waste Heat Recovery for District Heating – Handbook. European Union H2020 Project, https://www.euroheat.org/dhc/eu-projects/re-use-heat


International Energy Agency District Heating and Cooling (IEA DHC) (2020). Annex TS2: Low Temperature District Heating Implementation. https://www.iea-dhc.org/the-research/annexes