Thermodynamic advantages of using solar energy in the regenerative Rankinepower plant

Use of solar energy is of great importance in reducing greenhouse gases emi ssion. Although there are some advances in solo solar power systems, the ef ficiencies and costs of these systems are not so attractive. This paper pre sents a new approach for solar power utilization, i.e, using solar heat to replace the extracted steam to heat the feedwater in the regenerative Ranki ne plant. The exergy merit index EMI (the ratio of the work generated by th e saved steam to the exergy supplied by the solar heat) of such solar-aided systems can be greater than 100% while the maximum exergy efficiencies of the solo solar power systems can never reach 100%. The analysis of a three- stage regenerative Rankine plant shows that, by using solar energy, the wor k generated can be increased up to 30% while the EMI reaches 101.28%. There fore low-grade heat and other waste heat can be utilized as a valuable sour ce of work in this way. The "aided" concept has special meaning for solar p ower utilization. In summer, both the solar radiation and the electrical lo ad demand reach their peaks. The increased solar radiation can generate inc reased power to meet the increased power demand. In addition, the solar aid ed system can also eliminate the variability in power output in solo solar power systems. (C) 1999 Elsevier Science Ltd. All rights reserved.