Scrutinize thermal-load data before you plan for cogeneration

To evaluate the feasibility of a cogeneration project, it is necessary to compare the potential savings in operating costs with any capital costs that might be required. The operating costs have two major components: energy and equipment operation and maintenance. The former is the dominant factor affecting overall profitability. Calculations of energy cost are based on two factors: system/equipment performance characteristics and plant thermal load. The correct method for determining energy cost involves taking into consideration plant performance characteristics relative to anticipated plant load; the better the estimate of thermal load, the more accurate the estimate of energy cost will be. Normally, it is not economical to design a cogeneration plant to produce all of the required thermal and electrical energy. Peak-energy supply is better obtained from sources such as supplementary firing of on-site boilers for steam, and electric-power purchases from your utility. But if an agreement can be reached with your electric company, based on the Public Utility Regulatory Policies Act (Purpa), it may be more economical to produce excess electric power and sell it.