Constant Power Method Applied To The Economy Analysis Of A Solar Aided Coal-fired Unit

Under the double burden of environmental pollution and energy crisis, the development of clean energy is valued. As a kind of clean energy, the solar energy is used more and more widely. The combination between solar energy and power industry is imperative in that the power industry provides motivation for society developing.Solar aide coal-fired units have a variety of collecting programs. The mathematic model for system economy analysis is constructed at constant power output based on method of conversion coefficients of heat rates and free path rule. The condition at constant power output meets the realistic operation better. Mathematic model includes the analysis indicators for thermal economy of system, the analysis indicators for economy of oil heat exchanger and the analysis indicators for economy of collector. Thermal economic indicators include the decline of coal consumption rate, heat rate and steam rate comparison between the solar aide coal-fired unit and traditional power generation. The economic indicators of oil heat exchanger include heat exchanger’s area, exergy efficiency and the exergy profit of per unit area. The economic indicators of collector include collecting area, collecting cost, collecting efficiency and the collecting cost of per unit area.Take the 300MW unit for instance, the performance of system is analyzed. The result shows that the decline rate of coal consumption rate, heat rate and steam rate, the area of heat exchanger and collector are all linear with external heat when the extraction location which is replaced partially by solar energy is certain. The decline rate of coal consumption rate, heat rate and steam rate present decreasing trend, and the heat exchanger’s area increases gradually while its exergy efficiency decreases gradually, and the collector cost increases then decreases while its collection efficiency shows an opposite tendency, and the profit of per unit area shows decreasing trend, the ratio between collector cost and the decline rate of coal consumption rate increases then decreases then increases with decline in the quality of the extraction steam replaced by solar energy when the external heat is constant. Take the system, oil heat exchanger and collector into consideration, the thermal economy of power unit is best when the first class extraction of high pressure heater is replaced partially.