  This paper investigates the water network's potential ability to provide
demand response services to the power grid under the framework of a
distribution-level water-energy nexus (micro-WEN). In particular, the hidden
controllability of water loads, such as irrigation systems, was closely studied
to improve the flexibility of electrical grids. A optimization model is
developed for the demand-side management (DSM) of micro-WEN, and the simulation
results assert that grid flexibility indeed benefits from controllable water
loads. Although the proposed optimal DSM model is an intractable mixed-integer
nonlinear programming (MINLP) problem, quasi-convex hull techniques were
developed to relax the MINLP into a mixed-integer convex programming (MICP)
problem. The numerical study shows that the quasi-convex hull relaxation is
tight and that the resulting MICP problem is computationally efficient.
