Working fluid screening for ocean thermal energy conversion (OTEC) applications.

Ocean Thermal Energy Conversion (OTEC) is among the small number of renewable energy production systems that can provide base load capacity. Ammonia has long been proposed and tested as a working fluid for these systems. Are there any superior fluids from a purely thermodynamic standpoint? This question was probed based on the use of highly accurate thermodynamic equations of state, and a few other possible working fluids have been identified, but many candidates have disqualifying features: acute toxicity, high global warming potential, high ozone depletion potential, extreme flammability or very low condensing pressures. No identified fluids were obviously superior to ammonia, though CO2 and water deserve further study.