Investigation of the Performance of a Steam Power Plant at Off-Design Condition based on exergy analysis

A 320 MW steam power plant is studied and the energy and exergy analysis for the components as well as for the whole cycle of the plant is based on real data. Studies show that due to exergy dependence on ambient temperature, overall exergy efficiency increases by 5.93% with decreasing ambient temperature. Exergy degradation due to condenser temperature also leads to a 2.8% reduction in nominal load exergy degradation and 1.4% energy efficiency reduction in condenser temperature reduction. Also, the total exergy losses of the power plant cycle are about nominal output power, which however decreases by approximately 5% at nominal loads relative to the half load. The highest exergy losses were related to boilers and about 80% of total losses and the lowest exergy losses were for pumps and about 0.3%. Increasing the steam temperature of the boiler will also result in a 1.39% increase in energy efficiency and a 1.64% increase in the overall exergy efficiency of the plant. Therefore, the most cost efficient way of operating the power plant is at high and rated load conditions.