System Studies of Open-Cycle OTEC Components

A system model of open Rankine cycle ocean thermal energy conversion (OC-QTEC) was used to examine the effects of component performance and design on plant cost. Three components are examined in detail: an optional seawater deaeration subsystem, the flash evaporator, and a two-stage direct contact condenser. Preliminary data quantifying noncondensable gas release in upcomers and a debubblerchamber were used to evaluate the effect of predeaeration (removing the dissolved gases in deaeration chambers before the seawater enters the heat exchangers) on system cost and performance. Little data on the interactions between geometry and performance of vertical spout flash evaporators operating under OTEC conditions are available; therefore, we performed independent parametric variations.For the direct-contact condenser previous numerical studies provide the basis for coupling geometry and performance. Results of these studies are useful in setting research priorities, in defining operating conditions for further seawater experiments, and in updating plant cost estimates.