10157199FORTRESS ( Flexibility and Optimisation for Resilience in Energy Systems)ClosedFeasibility StudiesInnovate UKIt is essential that Protected Sites (PSs), e.g. hospitals and military sites, have a resilient energy supply to meet critical requirements. Most protected sites currently use fossil-fuels for heat and backup solutions. For Distribution Network Operators (DNOs), supporting protected sites' transition to electrified heating will require providing additional capacity whilst maintaining the requisite level of resilience, involving major infrastructure investment. Utilising a coordinated, flexible approach to heat demand offers the opportunity to offset some of these costs . FORTRESS's hospitals use case demonstrates these diverse resilience needs, from critical-care to administrative buildings, analysing innovative heat flexibility strategies for DNOs.