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Verdant Power’s Free Flow System (FFS)* is a turnkey water-to-wire system utilizing horizontal-axis turbines to convert the kinetic
energy of fast-moving (> 1.8 m/s) water currents into clean renewable electricity.    Multiple turbines are deployed on TriFrame™
mounts in a field array fully underwater and not visible from the surface.

Free FlowSystem Turbine

The central component of the Verdant Power Free Flow System is a
three-bladed horizontal-axis turbine.    The turbine is equipped with a
composite rotor with three fixed-pitch blades that rotate at a slow and
regular rate (approx. 32 rpm), well below normal water vessel propeller
speeds and conventional hydropower turbine blade speeds.


The drivetrain and generator are enclosed within the nacelle, including a
special integrated long-life planetary gearbox and bearing housing with
mechanical shaft seals for the main shaft. The sealed nacelle is supported on
a pylon that attaches to a seafloor mount, which can vary depending on site
and project specifications.


Simple and Scalable: 
A key advantage of the FFS turbine is its simplicity -- the unit is ‘ready for
operation’ almost as soon as it is deployed. The turbines include no
hydraulic systems and rotate to generate energy as long as there is
adequate water speed (> 1.8 m/s). The turbines operate continually and
automatically, and are remotely monitored by a proprietary control system,

TriFrame™ Mount

Verdant Power's TriFrame™ is a steel, triangular frame mount that
supports three Free Flow System turbines.    An array of multiple turbines
on TriFrames is arranged at a project site based on water velocity,
hydrodynamics, and accessibility.


Array Maintenence - Retrieve and Replace (R&R)
: A key advantage of the TriFrame™ is that multiple turbines can be
accessed through one on-water operation.   To minimize outage time and
high costs of on-water work, the evolving TriFrame™ maintenance
strategy is a retrieve and replace (R&R) cycle, meaning the retrieval and
immediate replacement of turbines with ready spares. The retrieved
turbines are then refurbished at a local land-based facility for subsequent

TriFrame™ Mount

Other Advantages

  • TriFrame™ allows for installation and R&R access to multiple turbines in single on-water operations, minimizing related
time and high costs.

  • R&R cycle strategy allows for regularly scheduled on-water operations and maintenance work, lowering the levelized
cost of energy (LCOE) and reducing risks for unplanned outages.

  • Coupled with the simple design of the Free Flow System turbine, use of local facilities for refurbishment can return
turbines to readiness and into a spare fleet within days.

  • Refurbishment work can usually be accomplished in the community surrounding the project, creating local
economic benefits.


The fundamental technology development of Verdant Power’s Free Flow System has focused on concurrent advancements in the following four areas around and bearing on the company’s projects and work in partnership with government, NGO, and other research partners:

  • Technology Advancement

  • Manufacturing and Levelized Cost of Energy (LCOE) Reduction

  • Environmental Compatibility

  • Regulatory Acceptance

Key milestones achieved during this technology development period are as follows:

  • Advancing the Free Flow System through five generations of RD&D, taking the technology to the current 5th generation (Gen5) 

  • Undertaking first-of-a-kind regulatory and environmental compatibility efforts, achieving acceptability of the Free Flow System design in marine environments and resulting in the first commercial license for tidal power in the United States

  • Progression of US-based manufacturing and supply chain efforts focused on logical reductions in product costs and LCOE

Generation 5 Free Flow System
Development of the 5th Generation (Gen5) Free Flow System is advancing based on prior generation operations. The Gen5 system represents a commercially economical design for reliability, resilience, and environmental compatibility.  The design cycle has focused on minimizing maintenance requirements by maximizing service intervals and achieving economic volume manufacturing and assembly.


Key design enhancements to the Gen5 turbine include the following:

  • Composite (fiber-reinforced plastic) blades

  • Ductile iron hub casting

  • Casting for pylon/nacelle connection

  • Integrated gearbox unit incorporating shaft housing/bearings/seals

  • Redundant dynamic (shaft) and static sealing to retain lubricant and exclude seawater

  • Novel long service life main shaft seal arrangement

  • Failsafe brake

  • Non-toxic fouling-release coating system

  • Improved commercial quality control and assurance manufacturing process

TriFrame™ Advancement and IO&M Cost Reductions

Key to the commercialization of a marine energy technology is to make significant reductions to the costs of system installation, operations & maintenance (IO&M). Towards this end, Verdant Power is in the final phases of a three-phase project with support from the US Department of Energy (DOE) and the New York State Energy Research & Development Authority (NYSERDA) that will conduct an integrated design process to develop, operate, and execute a cost-effective maintenance cycle at full-scale in open water, on a TriFrame™ equipped with three Gen5 turbines at the RITE Project site.  Installation of the Gen5 system on the TriFrame™ mount is planned for Fall 2020.  Learn More >


TriFrame™ with Gen5 Turbines           Planned for Installation at RITE (2020)


Advancement of Gen5 Turbine Rotor Blades

Verdant Power completed a project supported by the US DOE to design and test the larger, higher-power Gen5 composite turbine rotor.  In addition to the DOE, the effort was conducted in partnership with the National Renewable Energy Laboratory, Sandia National Laboratories,  and the University of Minnesota's St. Anthony Falls Laboratory and used evolving turbine modeling techniques along with computational fluid dynamics and finite element analysis to design, assess, and optimize the new rotor.  The composite blades were also designed for cost-effective volume production. 

The effort culminated in the successful full-scale (5m diameter) in-water dynamometry and loads testing of the full Gen5 turbine rotor assembly at Verdant Power's RITE Project site.  This updated rotor design is planned for use on Gen5 turbines to be installed at the RITE Project and future commercial installations, including at larger scales.

In-Water Gen5 Rotor Test

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