Waste Heat – Problem or Solution?
Faculty of mechanical engineering UL
Date of publication:
Waste heat could become one of the key sources of clean energy in the future. A new breakthrough study by researchers from the Faculty of Mechanical Engineering at the University of Ljubljana shows that advanced high-temperature heat pumps can significantly reduce energy consumption, greenhouse gas emissions, and thermal environmental impact—particularly in industry and the energy sector.
The research was carried out by scientists from the Laboratory for Refrigeration and District Energy Systems (LAHDE), together with an international team of experts. In the study, they provided the first comprehensive assessment of the potential of alternative high-temperature heat pump technologies that could replace inefficient fossil fuel combustion and direct electric heating in high-temperature industrial processes.
Why is this important? Heating and cooling today account for roughly half of final energy consumption, while at the same time nearly half of all energy used is lost as waste heat, which is typically simply released into the environment. The study shows that this heat can be captured, reused, and upgraded to temperature levels suitable even for the most demanding industrial processes using advanced heat pump technologies.
Current commercial high-temperature heat pumps typically reach temperatures of up to around 250 °C, whereas industry often requires significantly higher temperatures—up to 1000 °C or more. The authors therefore systematically present and compare alternative technologies, such as caloric, thermoelectric, and thermoacoustic systems, as well as mechanical processes based on Stirling and Brayton cycles, which could enable such a breakthrough.
“Solutions we are presenting enable the development of new products and services while at the same time significantly reducing energy use, emissions, and the thermal impact on the environment. Now is the time to transfer these solutions into practice and fundamentally transform our energy systems and industry,” emphasizes Prof. Dr. Andrej Kitanovski, the lead author of the study.
Co-author Assist. Prof. Dr. Katja Klinar adds: “Our research opens up entirely new fields of application for heat pumps. While they are currently mainly used in buildings, the question arises: why not also use them in industry—for heating from 250 °C up to 1200 °C?”
A key advantage of high-temperature heat pumps is their exceptional energy efficiency. Instead of producing heat through direct fuel combustion or inefficient electric heating, industry can reuse existing waste heat. The authors estimate that in high-temperature processes, energy consumption and emissions could be reduced by at least half. The greatest potential for application is seen in the processing industry (metallurgy, chemical industry, refineries, production of non-metallic materials) as well as in the energy sector.
The research involved experts from China, Spain, Croatia, and the United Kingdom, confirming the global importance of the topic and strengthening Slovenia’s role in the international scientific space. The study also highlights a broader societal challenge: waste heat is still treated as a problem rather than an opportunity. Yet this is precisely where opportunities arise for the development of new technologies, industrial solutions, and high-value jobs.
The study was published in the journal Nature Energy and represents an important milestone for Slovenian science and industry. With it, the authors lay new foundations for the development of high-temperature heating processes and heat pumps, while sending a clear message: without a comprehensive transformation of energy systems and close cooperation between science, industry, and policy, we will not be able to fully exploit the enormous potential of waste heat.
