A cooperation with customer-side cogeneration systems for power flow congestion relief and its environmental impact

Dispersed generation technologies (e.g. gas-engines) have greatly advanced in recent years. Gas engines are often operated as the main component of a cogeneration system (CGS). By using exhaust heat, the total efficiency of CGSs reach from 70% to 80%, and from a customers´ point of view is useful for reductions of CO₂ emission. Therefore CGSs have been given preferential treatment by the Japanese government and their installation and use is expected to become widespread in the future. When customers introduce CGSs, these systems have an influence on the demand profile for electric utilities. On the other hand CGS operational patterns depend on customers´ economic requirements; thus it is difficult to flexibly change those patterns so that they meaningfully contribute to the electric utility. As a demand response program, the authors proposed a method whereby CGSs at the customer-side are used for congestion relief in transmission networks. In the proposed method, the optimal configuration of energy systems including CGSs at the customer-side is determined. As well, the optimal operation of the electric utility´s generators is also determined taking into account the CGS operation patterns. This paper evaluates both costs to the electric utility and the customers´ cost for congestion relief in transmission networks. Further, we evaluate the influence on CO₂ emission and primary energy consumption from the view point of a unified energy system with CGSs providing input on a flexible operation pattern