The goal for Power Generation does not show the step to create a loose storage for the coal. After the research is complete two steps are shown: (1) "Build Boiler (0/1) and connect it to Ground Water Pump (1/1)." (2) "Drag the left / green slider in the Loose storage to the right to make it actively request coal".
Building a loose storage and sliding the green slider reveals and completes the step to build a loose storage for coal.
Yeah, it's a real tiny thing.