A physics based economic model starts with a physical definition of wealth.
Wealth is the product of applying intelligence to base matter. This process raises base matter to a level of functionality that satisfies a need. Clay becomes brick, bricks build cities. Iron oxide becomes steel, the steel becomes machines. Our civilisation is based on trillions of transformations of this type.
We cannot measure intelligence as a physical effect, but we can measure the amount of intelligently directed energy employed to embed intelligence in base matter.
We can therefore define wealth in physical terms using