Efficiency measures for energy supply and use aiming for a clean circular economy

Energy use minimisation and sufficient energy supply at minimal footprints are crucial for sustainable development. This article considers the key issues and developments in energy optimisation of industrial and urban systems for achieving a clean Circular Economy. The overall system perspective is presented in the form of the Circular Economy Hierarchy, within which the general developments and the contributions of the current Virtual Special Issue from the PRES’20 conference are overviewed and analysed. The review and discussion reveal the need for integrated modelling and optimisation of business and urban processes to minimise energy demands and to satisfy them with minimal environmental impacts efficiently. Several vital directions for future research and development are outlined – the synergy of Process Integration and Process Intensification, the development of novel concepts and tools for unified modelling and optimisation of diverse industrial, business and urban processes, and the need to develop methods for efficient recycling of renewables harvesting equipment disposed of at end-of-life.