Exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC desalination

Abstract

In this paper exergy analysis and thermoeconomic cost accounting of a CHP steam cycle integrated with MED-TVC plant is performed; the purpose is to show how this methodology provides a rational criterion to allocate production costs on electricity and freshwater. After a brief overview on methodology and a description of reference plant, exergy analysis is carried out in order to calculate exergy flows and plant exergetic performance. A detailed description of the adopted thermoeconomic model is given. Cost accounting is performed considering two scenarios: in the first, the concentrated brine is disposed back to sea, thus being its exergy content definitively wasted; in the second, conversely, part of brine exergy is used in a reverse electrodialysis unit to produce further electricity. In both cases results show that high unit costs characterize products which involve major exergy destruction, particularly freshwater in the first case and RED electric power in the second.