Benchmark thermodynamic modelling comparison of a novel modular air-cooled condenser with current dry-cooling methodologies

Economic constraints and environmental concerns have curtailed the use of water as a cooling medium for condensers in Rankine cycle thermoelectric power plants. As an alternative, air-cooling is frequently employed. However, current Air-Cooled Condensers (ACCs) haven been found to be highly inefficient. In an attempt to alleviate certain deficiencies, a Modular Air-Cooled Condenser (MACC) has been developed. A systematic campaign of experimental tests has been carried-out to analyse and establish the performance of this condenser. This paper builds upon previous work by presenting a thermodynamic analysis, in an attempt to establish the qualitative and quantitative plant performance with a MACC system installed. The analysis is carried-out for a small-medium Concentrated Solar Power (CSP) plant size of ∼20 MW. Variables investigated in the analysis were the number of MACC modules (condenser size), ambient temperature, and speed of the cooling fans. Steam turbine inlet conditions were not considered, insofar that they remained constant at the specified nominal conditions. Results from the analysis are presented in terms of plant efficiency loss, which showcase the advantages of the MACC design - in particular the variablespeed cooling fans. In response to variations in ambient temperature, the fan speed increases/decreases to achieve an optimum operating point. Hence, regardless of ambient temperature, plant losses are minimised. The resulting thermodynamic performance was benchmarked by comparison with a similarly-sized conventional A-frame ACC, and cooling-tower. Performance data for the traditional cooling solutions was generated through thermodynamic modelling in the commercial software package Thermoflow. It was found that a ∼20 MW CSP plant cooled by a MACC system consistently out-performs that with a similarly-sized conventional A-frame ACC installed. Relative to the ACC, increases in net plant output of between 2% - 4.5% were calculated to occur, across the range of ambient temperatures considered herein, with the MACC installed. Similar observations are made when compared to a cooling tower, with increases in net plant output ranging from approximately 1% - 3.5%, up to ambient temperatures of ∼35 °C. At temperatures greater than this the cooling tower out-performs the MACC system unless condenser size is increased.