Exergy analysis of ammonia-based solar thermochemical power systems

The reversible dissociation of ammonia is one of the candidate reactions fo r use in closed loop solar thermochemical energy storage systems. The major determinant of achievable performance for such a system is the degree of t hermodynamic irreversibility associated with the heat recovery process. Exe rgy analysis of a semi realistic 30 MPa isobaric system has revealed that t he major irreversibilities occur within the exothermic reactor and the coun terflow heat exchanger between ingoing and outgoing reactants. In this stud y, optimum reactor control yielded exergetic efficiencies up to 71%, which should translate to overall solar to electric conversion efficiencies of ar ound 20%. (C) 1999 Elsevier Science Ltd All rights reserved.