Thermoeconomic operation optimization of a coal-fired power plant

Thermoeconomic models, which combine the concept of cost in the field of economics and the concept of exergy in the field of thermodynamics, provide a possibility of optimizing complex energy-generating systems to achieve a best balance between thermodynamic efficiency and economic cost (including investment cost and operation cost). For the first time, operation optimization on a 300 MW coal-fired power plant located in Yiyang (Hunan Province, China) is accomplished based on the structure theory of thermoeconomic. Two optimization strategies, global optimization and local optimization, are successively realized on the power plant. Both strategies aim to minimize the total annual cost of the plant, and a 2.5% reduction in the total annual cost and a 3.5% reduction in the total investment cost are achieved. In addition, the costs of products of almost all units after optimization processes decrease obviously. It is worth noting that local optimization proposed in this paper attains almost the same performance as global optimization but with faster speed. Furthermore, sensitivities of optimal operation parameters with respect to external environmental parameters and the sensitivity of the objective function (the total annual cost) with respect to decision variables (e.g., the equipment efficiency) are presented. An optimization work could be briefly defined as the process of finding the values of variables that minimize (or maximize) objective functions. For different optimization objects, an optimization work of an energy-generating system can be considered at three levels: synthesis optimization, design optimization as well as operation optimization [1]. In this paper. the optimization is at the operation level. In this sense, the synthesis and design of a system are known and fixed. The conventional thermodynamic optimization process of an energy-generating system usually focuses on the energy saving or exergy saving. This kind of optimization has many drawbacks: (1) an increase of the efficiency or a decrease of the irreversibility of the system will lead to a decrease of fuel consumption. However, this is generally achieved with a corresponding increase of the investment cost. Thus it is difficult to reach a balance between thermodynamics and economics; (2) such optimization is usually based on the first and second laws of thermodynamics [2] (Le .. the conversation law of energy and the irreversibility of exergy). As known, the same amount of energy in different thermal devices may have quite different amounts of exergy and therefore quite different economic values. Thermodynamic optimization is thus unable to differentiate the …