What does co-generation refer to?

Co-generation refers to the simultaneous generation of electricity and thermal energy from a single fuel source. This process maximizes the efficiency of energy production by utilizing the heat that is created during the generation of electricity, which would otherwise be wasted. In co-generation systems, the heat produced during electricity generation is captured and used for heating purposes, such as providing hot water or steam for industrial processes, or for space heating in buildings. This dual production capability allows for a more efficient overall energy system, reducing fuel consumption and lowering greenhouse gas emissions compared to separate generation methods.

The other options do not accurately capture the essence of co-generation: while some of them touch on aspects of energy production, they fail to address the specific combination of electricity and thermal energy generation that defines co-generation.