  Electricity, water, and gas systems are critical infrastructures that are
sustaining our daily lives. This paper studies the joint operation of these
systems through a proposed optimization model and explores the advantage of
considering the system of systems. Individual and joint optimizations are
studied and compared. The numerical results show that the total electricity
cost for these three systems can be reduced by 9% via joint optimization.
Because the water system and gas system intrinsically include the storages in
their systems, the power system can use these storages as the regulation
capacity to shift load from peak hours to off-peak hours. Since the saving on
the power generation cost surpasses the incremental cost in the operation and
maintenance (O&M), the overall economic performance is improved by the joint
optimization.
