A review on optimization of district energy systems

The scientific state-of-the-art indicates that solutions for integrating renewable energy in the energy sector have primarily been sought within the limits of individual energy sub-sectors, focusing on concepts such as 'Smart Grid', 'Zero Energy Buildings', and 'Power-to-Heat', while the heating and cooling sectors have largely been overlooked so far. The heating and cooling sector should undergo a transformation in response to sustainability concerns and greenhouse gas emissions. District energy systems (DES) are expected to play an essential role in the development of climate-neutral societies. However, due to its large scale and its potential integration to a number of other energy systems, DES introduces complexity in design and operation, necessitating optimization studies to achieve key objectives such as reducing operational and infrastructure costs, minimizing emissions, and enhancing efficiency. This review addresses a gap in current research on DES optimization by exploring the technical aspects behind DES optimization and their practical applications. The review begins by outlining the state-of-the-art of DES and their evolution. Following this, the review examines the technical foundations of DES optimization studies in the literature. Moreover, the review outlines the critical components of DES optimization, including problem formulation and algorithms used to find efficient solutions. Additionally, key areas for future research and development in DES optimization are identified.