A rXXXX American Chemical Society pubs.acs.org/EF Energy Fuels XXXX, XXX, 000–000 : DOI:10.1021/ef9012906 Multi-point and Multi-level Solar Integration into a Conventional Coal-Fired Power Plant † Qin Yan, ‡,§ Yongping Yang, ‡ Akira Nishimura, ) Abbas Kouzani, ^ and Eric Hu* ,§ ‡ School of Energy and Power Engineering, North China Electric Power University, Beijing 102206, China, § School of Mechanical Engineering, The University of Adelaide, Adelaide, South Australia 5005, Australia, ) Division of Mechanical Engineering, Graduate School of Engineering, Mie University, Tsu 514-8507, Japan, and ^ School of Engineering, Deakin University, Geelong, Victoria 3217, Australia Received November 3, 2009. Revised Manuscript Received January 12, 2010 Solar-aided power generation (SAPG) is capable of integrating solar thermal energy into a conventional thermal power plant, at multi-points and multi-levels, to replace parts of steam extractions in the regenerative Rankine cycle. The integration assists the power plant to reduce coal (gas) consumption and pollution emission or to increase power output. The overall efficiencies of the SAPG plants with different solar replacements of extraction steam have been studied in this paper. The results indicate that the solar thermal to electricity conversion efficiencies of the SAPG system are higher than those of a solar- alone power plant with the same temperature level of solar input. The efficiency with solar input at 330 °C can be as high as 45% theoretically in a SAPG plant. Even the low-temperature solar heat at about 85 °C can be used in the SAPG system to heat the lower temperature feedwater, and the solar to electricity efficiency is nearly 10%. However, the low-temperature heat resource is very hard to be used for power generation in other types of solar power plants. Therefore, the SAPG plant is one of the most efficient ways for solar thermal power generation. 1. Introduction Generally, solar (thermal) collectors can be divided into a high- and intermediate-temperature range (150-350 °C or higher) and low-temperature range (50-150 °C). The typical forms of the high and intermediate range collectors are parabolic trough, dish, and solar tower. They are all concen- trating-type collectors by converting solar energy into high- temperature heat using various mirrors. 1,2 The highest tem- perature that the parabolic trough can generate is in the range of 400-500 °C. 3,4 The typical low-temperature collectors are flat plate and vacuum tube collectors that are less expensive and easier to maintain than the other concentrating systems mentioned above. The collected solar thermal energy in the high-temperature range is usually used for power generation purposes. If the tracking linear parabolic concentrators are used in a typical solar-alone power station, the peak thermal electricity efficiency is lower than 21%. 3,5 The first commer- cial solar (alone) power plant is located in California and has operated since the 1980s. Some solar power generation systems are equipped with thermal energy storage compo- nents to ensure stability. 6 The vacuum tube solar collector is a type of nonfocusing collector. In comparison to concentrat- ing-type collectors, its cost is lower and is almost mainte- nance-free, because the sun track system is not required. A typical vacuum tube collector with the selective coating can generate heat at a maximum temperature of 200-300 °C. At present, a conventional coal- or gas-fired power plant is a major/dominant way to generate base-load electricity in the world. However, the problems of polluntion emissions, greenhouse gas emissions, etc. have drawn more and more attention. 7 Although the new designed and developed 600 or 1000 MW ultra-supercritical units have improved efficiencies, coal consumption rate, and emissions, it still cannot generate “green” electricity. The conventional power industry is under huge pressure with the renewable energy targets and carbon taxes set by various governments. A real technical revolution is needed to change the power industry into an environmen- tally friendly industry. Integrating solar thermal energy into a conventional power plant using solar-aided power generation (SAPG) to replace part of the extraction steam can not only reduce coal con- sumption and emission but also efficiently use solar energy for power generation. 8 Several workes have been performed in this field. You and Hu presented the SAPG system and calculated the thermodynamic benefits of a three-stage regen- erative Rankine hybrid system. 8 You and Hu presented the solar energy to replace part of the heat demands in the boiler, and the thermal efficiency and exergetic efficiency of the aided system are 17.9 and 25.12%, respectively. 9 Gupta et al. † This paper has been designated for the Asia Pacific Conference on Sustainable Energy and Environmental Technologies (APCSEET) special section. *To whom correspondence should be addressed. E-mail: eric.hu@ adelaide.edu.au. (1) Stoddard, L.; Abiecunas, J.; O’Connell, R. National Renewable Energy Laboratory (NREL), Golden, CO, 2006; p 2. (2) Fadar, A. E.; Minmet, A.; Azzabakh, A.; Perez-Garcia, M.; Gastaing, J. Appl. Therm. Eng. 2009, 29 (5-6), 1267. (3) Tyner, C. E.; Kolb, G. J.; Geyer, M.; Romero, M. SolarPACES, 2001; pp 5-8. (4) Qu, H.; Zhao, J.; Yu, X.; Cui, J. Renewable Sustainable Energy Rev. 2008, 12 (9), 2505. (5) AI-Soud, M. S.; Hrayshat, E. S. J. Cleaner Prod. 2009, 17 (6), 625. (6) Vaivudh, S.; Rakwichian, W.; Chindaruksa, S. Energy Convers. Manage. 2008, 49 (11), 3311. (7) Yang, H.; Pollitt, M. Eur. J. Oper. Res. 2009, 197 (3), 1095. (8) You, Y.; Hu, E. Appl. Therm. Eng. 1999, 19 (11), 1173. (9) You, Y.; Hu, E. Appl. Therm. Eng. 2002, 22 (4), 359.