State-of-the-art review on evaluation indicators of integrated intelligent energy from different perspectives

Integrated intelligent energy (IIE) plays a key role in promoting the utilization of renewable energy, improving energy efficiency and reducing energy costs. A reasonable indicator-based evaluation system and its associated indicators are essential for the entire project life of IIE, including top-level design, system planning, optimal scheduling and project acceptance phases. Therefore, in this study, a review on state-of-the-art evaluation indicators of IIE from multiple perspectives is conducted, i.e., the energy level, energy trilemma, typical projects and index attributes. Specifically, the energy source flowing into IIE system is divided into carbon-based fuels, electric energy, thermal fluid energy and zero-carbon-based fuels. Meanwhile, the indicators including energy utilization benefits, eco-friendly benefits, economic and social benefits, as well as integrated and intelligent benefits are summarized. The indicators are then corresponding with four representative topologies of IIE and their demonstration projects are discussed accordingly, i.e., the distributed combined cooling, heating and power system, multi-energy complementary integrated optimization system, new energy microgrid, and Energy Internet respectively. Furthermore, the relevant indicators are classified into five types according to the attributes of comparative, interconnected, interactive, self-sufficient and common. Finally, several insights based on theoretical research, standard formulation, and project acceptance have been proposed to further develop the evaluation indicators of IIE.