Consulting-Specifying Engineer, Nov. 2016, by Cynthia A. Callaway.
http://www.csemag.com/single-article/optimizing-facility-operations-with-cogeneration-systems/24f783746b2e9d47202376525bd3d1f4.html

"A cogeneration system is not a single technology, but an integrated energy system that can be modified depending upon the needs of the energy end user. This type of system burns natural gas to simultaneously produce electricity and heat (see Figure 2). The heat is recovered from the combustion system's exhaust stream and converted into useful thermal energy, in the form of steam or hot water, which is either used directly or fed into an absorption chiller to provide cooling."