What is unused?

Answer 1

The term "unused" is difficult to define in this contest.

• May forms of energy such as potential energy and chemical energy can be stored against use
  
• We do not have the technical knowledge to tap some energy
  
• Some energy fro large sources like the sun radiates away from us and cannot be tapped
  
• In industry there is some energy that is produced but wasted due to equipment inefficiency. As an example a car uses only about 30% of the energy provided.
  
• Some energy is of too low a value to collect and use