**Emerging Tools for Energy System Design Increasing Economic and Environmental Sustainability**

**Yee Van Fan 1, Zorka Novak Pintariˇc <sup>2</sup> and Jiˇrí Jaromír Klemeš 1,\***


Received: 12 June 2020; Accepted: 30 July 2020; Published: 5 August 2020

**Abstract:** Energy is a fundamental element supporting societal development, particularly with the increasing dependency on the Internet of Things. It is also the main contributor to environmental impacts and subsequently, a potential sector for mitigation. Sustainable energy system design considers energy savings and energy efficiency, waste and consumption reduction, process efficiency enhancement, waste heat recovery, and integration of renewable energy. Emerging tools range from advanced Process Integration, modelling, simulation, and optimisation, to system analysis and assessment. This review covers selected emerging studies promoting sustainable system design, including the recent developments reported in the Special Issue (SI) of the 22nd Conference on Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction (PRES'19). The primary emphasis was to enhance the economic and environmental performance. However, social factors were also highlighted as essential for future sustainable development. The discussion and analysis in this review focus on the most recent developments of (a) heat integration and heat transfer; (b) integrated and newly developed heat exchangers, (c) integration of renewables, and (d) roles in economic and environmental sustainability. The key results are highlighted, and future research ideas are suggested according to their links to a broader context.

**Keywords:** energy system; environmental sustainability; heat integration; economic sustainability; optimisation and modelling tools
