Backpressure Steam Cogeneration: A History and Review of the "Cheapest Power You'll Never Buy"

Abstract

The use of backpressure steam turbines to make low-cost electricity is a well established technology with a long and illustrious history and a value that became lost as industry switched from home-grown power generation to centralized utility power in the 30's and 40's. Cogeneration, once the normal and very efficient way of making power for most industries, cities, and even small towns, was left behind as utilities gradually moved toward large central station plants located far from city centers or industries that could serve as thermal loads. As a result, the average efficiency of electricity production dropped from 85% to 35% from 1935 to 1975. Now, however, the utility paradigm is changing again as deregulation spreads from state to state with its promise of more competition and better pricing for electricity users, and its accompanying proliferation of new rules and new players. In this environment, the value of a technology that allows industries and institutions to make cheap power as a function of their thermal load is re-emerging. This paper will review the history of backpressure steam cogeneration; the particular market niche of small systems -those under 10 MW; the advent of packaged systems and the advantages these bring to the under 10 MW market; and why this technology is particularly beneficial in a deregulated environment. We will also review the required circumstances for a successful project, and review first-pass financial evaluation techniques. Finally we will describe a few systems currently in use.