  We demonstrate a mapping between the problem of charge ordering in a
triangular array of quantum dots and a frustrated Ising spin model. Charge
correlation in the low temperature state is characterized by an intrinsic
height field order parameter. Different ground states are possible in the
system, with a rich phase diagram. We show that electronic hopping transport is
sensitive to the properties of the ground state, and describe the singularities
of hopping conductivity at the freezing into an ordered state.
