A hybrid fuel cell, solar thermal collector, and coal-fired power plant; energetic, exergetic, and emission analysis

Although the nonrenewable energy-driven power plants have major limitations, but at present, more than 80% of the energy needed all over the world is met through these power plants. Among them, almost one-third is supplied through coal-fired plants. However, the major limitation in the exploitation of coal fuel is the increase in environmental harms due to the increased greenhouse gas emissions. In this regard, it is necessary to adopt solutions and integrate these plants with other clean and green energy production cycles in order to reduce the emission of pollutants and improve their behavior. In this paper, the thermodynamic-conceptual evaluation of a new coal-fired plant driven by lignite is developed. Besides that, the plant is coupled with a solid oxide fuel cell and two independent solar units (both based on parabolic trough collector (PTC) arrays) in order to reduce the environmental harms of coal. Additionally, the introduced power plant consists of two power generation units based on a Rankine cycle and a gas turbine-based cycle. Therefore, the introduced plant can produce electric power and hot water. Further, the integration of cycles based on renewable technologies can reduce environmental pollution and improve plant's efficiency. Moreover, a comprehensive comparison is presented when changing power plant fuel from lignite to anthracite. The conceptual design of solar units based on the geographical characteristics of city of Karaj is also provided. The outcomes indicated that the gas released from the plant during the combustion process is approximately 94.1 kg per second. The considered plant can produce almost 270.2 MW of electric power and approximately 1572 kg of hot water per second. Additionally, the energetic efficiency was equal to 69.72% and exergetic efficiency was equal to 34.93%. The findings also indicated that the size of solar unit 1 under both types of anthracite and lignite coal is the same; while, by changing the type of coal from lignite to anthracite, the size of solar unit 2 can be reduced by almost 6.5 times.