Glad you enjoyed the read.  "Energy" is not a metaphor when it comes to economic activity;  all economic activity involves using energy and intelligence on matter to make things or provide services.  Sometimes the energy is human (food calories).  The big explosion in economic productivity came when we learned how to use antique solar income (fossil fuels) to move matter.  Intelligence is sometimes present in the form of an adaptable worker, following the algoriths of a trade or profession, and sometimes as design intelligence built into technologies that we use.  

When energy is being used, the laws of thermodynamics apply--not as metaphor, but literally.  

Industrial society is not sustainable. Unsustainable systems change--or disappear.