This annex was originally suggested in 2008. Annex XV Task 1 was finalized in the spring 2015. From September 2016 to August 2018 Task 2 was successfully completed. Nevertheless, a number of further questions were identified which are to be tackled within the framework of this Annex-Task 3 (01.11. 2019 to 31.10. 2021). The Annex takes on a multi-disciplinary approach to the concept of excess heat recovery integrated in industrial complexes, aiming at the optimization of energy efficiency in global terms. The approach is based on industry needs and application, combining the knowledge of industrial technologies with energy efficiency and cost-effectiveness.