Utilizing Skimmer or Curtain Walls to Reduce Entrainment at Cooling Water Intake Structures

In general there are only a few options available for power plants to reduce entrainment. Skimmer or curtain walls can be used to selectively withdraw from deeper water where densities of ichthyoplankton may be lower. Existing data suggests that these structures can substantially reduce entrainment, especially in cases where dissolved oxygen or temperature stratification exists or where ichthyoplankton densities are not evenly distributed and greater densities occur near the surface.

At present, there is little information available on the performance of these technologies for reducing entrainment. Therefore, the Electric Power Research Institute (EPRI) is embarking on a three phase approach to investigate if these technologies can achieve quantifiable reductions in entrainment: 1) literature review; 2) study design and rationale; and 3) field and/or laboratory demonstration studies. In a separate but related study, Duke Energy is collecting data at a facility that utilizes a deep skimmer wall (60 feet). This structure was originally designed to withdraw cooler water and improve condenser cooling efficiency. Preliminary data from the 1970s indicated that this structure substantially reduced densities of ichthyoplankton downstream of the wall. The current study is designed to better quantify the benefit of the skimmer wall in reducing entrainment.