April 10-14, 2016
Cogeneration systems that produce both heat and power are being promoted as a means of improving the overall energy efficiency around the world, especially in the industrial and power sectors. Claims are often made regarding dramatic improvements in efficiency for such systems. For example, a cogeneration system is advertised as being 85% efficient, while, for example, the U.S. grid is only 31% efficient. However, comparing such efficiency figures directly can be misleading. An 85% efficient cogeneration system is being evaluated at full load and on a first law of thermodynamics basis (i.e., input = output at steady state). The average grid efficiency figure considers all loads (including start up, shut down, part load, spinning reserve, etc.), all fuels, all types of equipment, and on a second law of thermodynamics basis (converting heat into work). There are additional considerations of economies of scale, cost, and operations that must be evaluated for a successful cogeneration facility. This presentation will examine some of these considerations in order to gain a better understanding of the potential and limitations of CO2 mitigation through the application of congeneration.
Carl Bozzuto, "Factors that impact the CO2 mitigation potential of cogeneration" in "CO2 Summit II: Technologies and Opportunities", Holly Krutka, Tri-State Generation & Transmission Association Inc. Frank Zhu, UOP/Honeywell Eds, ECI Symposium Series, (2016). http://dc.engconfintl.org/co2_summit2/20