Cross System Service (CSS) is more an innovative concept than a solution. The idea is, to combine existing and new partial solutions into comprehensive services that serve across the district heating system. Such solutions where defined in the vision of the HEAT 4.0 project, including services accross the physical component and the temporal domain, where long-term and short-term planning is merged with services on the operational level.
The most promient CSS is the [Cross System Optimization (CSO)] that aims at an optimization for the whole district heating system.
Across the temperal domain, the methodology behind FRIGG concept proposes ways to bridge models between different time horizons, e.g. between short term operation and long term planning.