Technical and economic investigations of a low-temperature Rankine-cycle heat engine

Aa low-temperature Rankine-cycle heat engine is examined using a systems analysis perspective and two analysis approaches - one based on maximizing thermodynamic performance, the other based on minimizing levelized energy costs. In the analyzed system, the engine draws its energy from a salt-gradient solar pond that has an average temperature of 86/sup 0/C. A computer code developed for the analysis included models for the solar pond, the piping systems, the economic analysis, and the heat engine. The effects of varying system parameters (including the working fluid) on thermodynamic performance and plant costs are presented, and predictions of cycle efficiency and system cost are given for several system designs. A comparison of the two analysis approaches is made, and the results demonstrate that the approach based on minimizing the plant levelized energy cost can select system parameters to produce the most economical plant, identifying subtle but important tradeoffs between thermodynamic performance and economics.