A review of micro hydro systems in urban areas: Opportunities and challenges

The modern layout and configuration of cities create power generation and storage possibilities through the urban water system. Surplus energy in water and wastewater networks has come to the researchers’ attention for exploitation as micro hydropower (MHP). Also, the gravitational potential energy of stored water on highrises makes them a sustainable option for distributed energy storage as micro pumped-storage (MPS). Many studies have investigated technical aspects and estimated capacity of urban micro hydro systems (UMHS) in urban infrastructures. However, there is no systematic review of relevant literature to signify challenges and opportunities of different urban infrastructures as UMHS, from economic, technical, and environmental viewpoints. Therefore, this article applied a reference-by-reference method to provide a systematic assessment and concept review of UMHS, including the characteristics, challenges, and drivers of potential sites for MHP and MPS development. Examining the challenges of real case studies worldwide identifies economic feasibility and energy generation reliability as obstacles in developing MPS and MHP, respectively. Nevertheless, overlooked opportunities are recognised that may accelerate UMHS proliferation. UMHS synergies, such as water saving and peak-load shaving, are introduced as influential factors in the economic feasibility of the UMHS that can be achieved through deploying sustainable stormwater management strategies and considering real-time analysis in the volatile energy market. Furthermore, simulation-optimisation tools are concisely presented for both the design and operation stages. Finally, some future research directions are offered to clarify the role of urban UMHS in addressing water and energy issues as individual systems or integrated into other decentralised energy sources.