Use cisterns. The standard cistern can be 20m deep by 10m by 10m. Two tanks, one 20m deep, the other above it at 10m. Pump water from the lower one into the upper one at night when power is cheap, recover the energy during the day and sell it back to the utility. Each of these has 98Mj of potential energy when 'charged'.
The technology to build and operate these is trivial. They could be put under public and private buildings, and generate cash flow for private investors, like vending machines or laundromats, only without the vandalism. They also serve as an emergency water source of a million litres in times of disaster.
Sometimes the simplest solution is best.