Techno-economic feasibility of a solar assisted coal power plant

• Main Author: Govender, Anthony
• Other Authors: Bennett, Kevin
• Format: Dissertation
• Language: English
• Published: University of Cape Town 2015
• Subjects: Mechanical Engineering
• Online Access: http://hdl.handle.net/11427/13125

Includes bibliographical references. === The use of solar heat in conventional coal-fired power plants has been demonstrated to reduce the coal consumption of the plant. A reduction in the amount of coal that is burnt by the power plant, means that less greenhouse gases are emitted by the power plant. Hence, the plant has a smaller impact on global warming. Countries such as Australia and the USA have implemented this concept of adding solar heat to a coal-fired power plant. This study investigates if solar heat addition to Duvha Power Station in Mpumalanga, South Africa, is technically and economically feasible. Duvha Power Station is one of the largest coal-fired power stations in Eskom. Two solar heat integration options were examined in this study i.e. the use of solar heat to heat feed water or to produce superheated steam. A market assessment of concentrated solar power (CSP) technologies was performed to establish the maximum water/steam conditions (temperature and pressure) that can be produced by each CSP technology. The CSP technologies assessed were the parabolic trough collector (PTC), the linear Fresnel reflector (LFR) and the central receiver (CR).By using the results of the market assessment, a suitable CSP technology was selected for each integration option. The technical capabilities of each plant area of Duvha Power Station, such as the boiler, turbines, feed water pump etc., was also assessed by reviewing original equipment manufacturer (OEM) data sheets. The solar field size of each integration option was determined through an iterative method, such that none of the technical capabilities of the power station were exceeded once solar heat was added. The annual hourly heat output of each solar field was thereafter predicted by using the System Advisor Model (SAM).The annual hourly heat output of each solar field was then used with a thermodynamic model of Duvha Power Station(referred to as the Duvha Virtual Plant TM model),to calculate the hourly project benefits. The hourly benefits are coal savings, greenhouse gas emission reduction, solar electricity etc. The capital expenditure (CAPEX) and operating expenditure (OPEX) of each integration option was calculated by using cost models provided in SAM. The benefits and costs of each integration option were used in an economic life-cycle assessment (LCA) model, to determine the most economically feasible integration option. It was found that the integration options that produced high-temperature steam have the highest integration effectiveness, such as the steam supply to the high-pressure turbine etc. The LCA revealed that the supply of steam, by using the LFR,to the highest pressure feedwater heater (HPH6), is the most economical option.This is because the LFR technology has the lowest CAPEX and fixed OPEX cost amongst the 3 CSP technologies.This integration option has a discounted payback period of 14,6years and a real Levelised cost of electricity (LCOE) of R1.64/kWhe.