With combined power and heat generation (cogeneration) the waste heat incurred during engine operation is recovered and utilized to satisfy thermal system process requirements for low- grade steam and/or hot water. In many cases this utilization of waste heat results in overall systems of efficiencies of up to 90+% (thermal + electrical). This efficient form of energy conversion is able to achieve primary energy savings of about 40% using gas engine cogeneration systems, compared with conventional separate power and heat generation. Figure 10 represents a typical Sankey diagram illustrating the Electrical/Thermal energy utilization from a typical Jenbacher gas reciprocating engine. In addition, the Sankey diagram also identifies the various heat sources from.
