Case Study: Zero Ascend Omnispecies (ZAO) Modular Fish Passage System
Client: U.S. Department of Energy (DOE), Water Power Technologies Office
Prime Contractor: Littoral Power Systems, Inc. (LPS)
Project Partners: Whooshh Innovations, Oak Ridge National Laboratory (ORNL), U.S. Geological Survey (USGS), GZA GeoEnvironmental, Kelson Marine
Location: S.O. Conte Research Laboratory, Turners Falls, Massachusetts
Timeline: March 2021 – March 2024
Project Summary
The ZAO project reimagines upstream fish passage at hydropower sites by integrating advanced hydrodynamics, prefabricated modular design, and proven volitional fish transport systems. Led by Littoral Power Systems, the Zero Ascend Omnispecies (ZAO) Attractor is a floating, scalable solution aimed at transforming disruptive turbine outflows into productive fish attraction flows—offering a cost-effective, site-adaptable alternative to traditional concrete fish ladders.
The Challenge
Most U.S. hydropower facilities face increasing pressure to retrofit for fish passage—yet traditional solutions are often bulky, immovable, and expensive, especially for low-head or non-powered dams. For weak-swimming species like American shad and river herring, turbine discharge can overwhelm attraction flows, limiting migration success. There is a pressing need for low-cost, modular solutions that enhance ecological compliance without sacrificing generation potential.
LPS’s Role
As prime contractor, LPS led the engineering design, hydrodynamic modeling, fabrication, and techno-economic evaluation of the ZAO system. Our team oversaw every technical phase, from CFD modeling of turbine outflows to structural stability analysis, modular hardware integration, and live fish behavior testing in lab-scale environments.
Engineering Highlights / Technical Solution
Modular Design Integration
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Designed a floating, containerized structure (20’/40′) to house fish passage components.
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Engineered to align with LPS’s own Standard Modular Hydropower (SMH) platform.
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Integrated Whooshh Innovations’ volitional entry system, including scanner, false weir, and Migrator™ tubes.
Hydrodynamic Modeling (CFD)
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LPS ran extensive CFD simulations to optimize fin geometry and module positioning.
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A V-back structure was found to create a low-turbulence “attraction lane” downstream—ideal for guiding fish toward entry.
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Simulations also evaluated placement strategies to harness turbine discharge zones with natural velocity profiles near 8 ft/s.
Buoyancy and Structural Engineering
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Custom steel framework with hybrid ballast floor (steel-concrete) for center-of-gravity control.
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Designed to maintain surface-level alignment for the false weir entrance, even under variable tailwater elevations.
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Naval and geotechnical assessments conducted with Kelson Marine and GZA GeoEnvironmental.
Advanced Manufacturing and Cost Analysis
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ORNL and LPS collaborated on design-for-manufacturing assessments.
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LPS developed a hierarchical cost breakdown and collaborated on LCOE comparisons to traditional fishways.
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Results showed significant CapEx savings and scalability advantages.
Results & Outcomes
Numerical Modeling Achievements
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CFD demonstrated that V-back structures at optimal tailrace positions can create shear-layer-defined attraction zones.
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Model-informed fin designs generated stable downstream cues while minimizing turbulence—a critical factor for surface-oriented species like shad.
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Simulations confirmed that auxiliary flow channels could fine-tune velocity profiles within the biologically preferred 3–4 ft/s range.
Experimental Testing Milestones
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LPS fabricated and installed a scaled ZAO prototype in a 10-ft flume at S.O. Conte Research Laboratory.
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Eight live-fish trials with American shad assessed behavioral responses to hydraulic conditions.
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Two trials clearly demonstrated effective attraction: fish entered the V-box zone and aligned with the module’s false weir entrance.
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ADV and ADCP surveys mapped velocity vectors across 28-point grids, validating modeled flow behavior.
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The module maintained stable alignment with water surface under varying flow conditions, validating structural design.
Impact
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Ecological: ZAO offers a pathway to safer, volitional passage for American shad, river herring, and other weak-swimming species.
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Economic: Modular design and advanced manufacturing reduce CapEx by avoiding concrete-heavy infrastructure.
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Regulatory: Supports fish passage compliance for relicensing and new development under FERC and USFWS guidelines.
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Scalable: Can be deployed at non-powered dams and integrated with LPS’s SMH systems, unlocking new hydropower potential.
Next Steps
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Full-scale pilot deployments are under consideration in collaboration with DOE, state agencies, and private hydropower operators.
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Additional field studies are being scoped to validate ZAO performance in dynamic river environments and inform commercialization strategy.