Geothermal Binary Plant Exergy Audit Checklist – ISO 50002 Compliant

Exergy analysis provides a rigorous thermodynamic framework for evaluating not just energy quantity but also quality—i.e., the maximum useful work potential of energy streams under defined environmental conditions. In binary geothermal plants, where geothermal brine heats an organic working fluid (e.g., isobutane or R-245fa) in a closed Rankine cycle, exergy losses predominantly occur across heat exchangers (especially the evaporator and condenser), turbines (due to isentropic inefficiency), pumps, and piping due to pressure drops and thermal mismatches. An ISO 50002-compliant audit integrates this exergy assessment into a formalized energy audit process, requiring documented scope definition, boundary delineation (system, subsystem, and component levels), measurement uncertainty evaluation, data traceability, stakeholder involvement, and evidence-based opportunity ranking—all aligned with Clause 6 (Audit Planning), Clause 7 (Audit Execution), and Clause 8 (Audit Reporting) of ISO 50002. The checklist operationalizes these clauses by prescribing mandatory data collection points (e.g., temperature/pressure at key nodes, mass flow rates, ambient reference state parameters), standardized exergy balance equations per component, and criteria for classifying exergy destruction as avoidable vs. unavoidable—thereby supporting continual improvement per ISO 50001. Furthermore, it bridges engineering thermodynamics with management system compliance, enabling auditors and plant engineers to jointly translate technical findings into actionable EnMS objectives, targets, and action plans.