Heat is the energy, not the flow. That flow is flux or power. A temperature difference is how we perceive or measure a difference in thermal energy density between two places, and is the potential that drives heat flux. A thermoelectric barrier between those two wells can extract energy from that flow, within thermodynamic limits.
Yes, I was a bit sloppy. It's the flowing energy, not the flow of energy. The point of my comment was to distinguish heat from stored thermal energy so the distinction isn't so important in that context.
