In which energy generation method is steam a primary byproduct?

In cogeneration, steam is indeed a primary byproduct because this method involves the simultaneous production of electricity and useful heat from the same energy source. In cogeneration systems, fuels like natural gas or biomass are burned to produce electricity, generating excess heat in the process. This heat can be captured and utilized for various purposes, such as heating water or providing space heating, which distinguishes cogeneration from other methods.

While geothermal energy also involves steam, particularly in the process of harnessing heat from the Earth, its primary focus is on the direct conversion of geothermal heat into energy, rather than as a byproduct. Similarly, coal energy involves steam in the context of electricity generation through steam turbines, but does not highlight steam as a byproduct in the same way cogeneration does. Wind energy, on the other hand, does not involve steam at all, as it relies on mechanical energy from wind to generate electricity. Therefore, cogeneration is the most accurate choice in this context, as it directly positions steam as a byproduct of the energy generation process.