Coordinating shared flexibility in renewable-rich power systems: A structured critical review from a sharing-economy perspective

Renewable-dominated power systems increasingly rely on flexible assets owned by households, fleets, energy communities, and firms. Installed capacity alone does not make these resources available to the system because their operating states, primary uses, and owners' willingness to participate change over time. In this review, shared flexibility refers to temporary access to the flexibility services of independently owned assets without transferring asset ownership. Such access may be coordinated through aggregators, energy communities, peer-to-peer platforms, or operator procurement. The asset owner, scheduling entity, service buyer, and settlement party may therefore be different actors. Shared flexibility here denotes temporary and conditional access to services provided by independently owned assets without transferring asset ownership. This review examines stationary and shared storage, electric vehicles, flexible demand, microgrids, and multi-energy resources across four connected dimensions: the capability that owners make available, the allocation of information and scheduling responsibility, the updating and dispatch of contracted flexibility across timescales, and the distribution of value, cost, and non-delivery risk. The literature shows that aggregation improves market access but does not by itself establish resource sharing. A workable arrangement must specify the service being offered, preserve network and resource feasibility, define the owner's participation and override conditions, and link payment to measured delivery. Existing studies address these requirements unevenly, and few follow shared flexibility from resource commitment through dispatch to settlement. The review identifies the need for service-specific capability contracts, coordination models that retain owner autonomy while assigning operational responsibility, and settlement mechanisms that account for delivery performance and the cause of deviations.