Emerging Trends
The in-stream and tidal energy industries are moving from demonstrations toward larger arrays and commercial projects. Ocean Energy Europe reports a growing pipeline of pre-commercial farms as the industry works to reduce costs, improve reliability and expand deployment. However, widespread commercial adoption remains limited.
Key challenges
This is because many in-stream and tidal technologies require specific combinations of current velocity, depth, site geometry and environmental conditions. The Pacific Northwest National Laboratory (PNNL) also identifies cost, installation, maintenance, environmental effects and limited suitable locations as barriers to broader deployment. Together, these challenges can limit widespread adoption. One path toward wider adoption may be greater adaptability. Standardizing energy converters around planned flow ranges and, where required and appropriate, engineering repeatable flow conditions to match them could address several of these barriers. Technologies capable of operating near the surface in natural, slower-moving waterways could further simplify deployment, access and maintenance.
Brisbane Lagoon: A Measured Example
Field measurements at Brisbane Lagoon on San Francisco Bay provide a useful example. During a tidal change of only about 3.5 feet, two parallel constructed channels, each approximately 10 by 10 feet and 150 feet long, carried incoming water at approximately 6 to 9 ft/sec for more than four hours.
These data demonstrate that a modest tidal change can produce sustained higher-velocity flow when a large exchange volume is concentrated through constructed passages.
The relationship should also scale with larger tidal exchanges. A preliminary model based on the measured Brisbane flow profile found that a 15-foot tidal range with two 20-by-20-foot channels could remain above 6 ft/sec for about four hours and above 5 ft/sec for about six hours of an eight-hour exchange.
The potential value of developing these flows can also be seen in measured drag forces. Independent instrumented testing of a six-foot Fiorentino para-anchor recorded approximately 950–1,000 pounds of drag at 4.7 ft/sec and 1,750–1,850 pounds at 6.4 ft/sec. Preliminary HydroChute testing further indicates that a moving collector can retain substantial force while traveling through the water, suggesting that channelized flows in this velocity range warrant further investigation for useful energy extraction.
Engineering Flow Rather Than Head
Unlike conventional tidal barrages, which generally favor tidal ranges of roughly 16 to 33 feet and primarily extract energy from water-level differences, a Managed Tidal-Exchange DER would manage flow in locations with much smaller tidal exchanges. With a standardized converter's preferred flow range and the available tidal resource known, lagoon and channel geometry could be designed to maintain that operating range for as much of the tidal cycle as practical.
Lagoon area determines exchange volume, tidal range and timing provide the driving potential, open-channel dimensions establish the flow regime and standardized converters are selected and spaced for those conditions. A barrage primarily engineers head. A Managed Tidal-Exchange DER would engineer and manage flow.
Multiple channels could provide operating control. More could remain open during strong exchange, as flow declines, fewer could remain open, reducing total flow area and potentially maintaining useful velocity longer to improve capture of the available tidal energy throughout the cycle.
Long channels could support spaced groups of modular converters. Their number and spacing would require hydraulic modeling and field testing, as each device would extract a portion of the available flow energy.
Distributed Energy Resources
Managed Tidal-Exchange DERs could operate individually or as distributed networks. Because tidal timing varies geographically, coastal projects would peak at different times, providing staggered, predictable renewable generation.
Dedicated energy lagoons are one implementation. Another is integrating generating channels into coastal infrastructure for flood protection, sea-level-rise adaptation, habitat restoration, parks or waterfront redevelopment. Renewable generation could then become one benefit of multipurpose coastal infrastructure rather than requiring energy production alone to justify the full construction cost.
Brisbane provides a real-world example. Beginning in 2025, its man-made lagoon became the focus of ongoing planning for habitat restoration, recreation, water management and sea-level-rise adaptation, demonstrating how future tidal DER infrastructure could potentially serve multiple purposes and distribute costs beyond energy generation alone.
Brisbane's tidal exchange supports a productive marine ecosystem. For long-term sustainability, future systems should extract energy without unnecessarily compromising the biological exchange and natural processes that make these waterways productive.
A Global Opportunity
Standardized converters and planned, repeatable flow environments could improve both adaptability and adoptability by simplifying manufacturing, installation, maintenance and replication while reducing dependence on a limited number of naturally ideal sites.
Shallow and surface deployments could expand opportunities in naturally occurring flows such as rivers, canals and tidal or open-ocean currents. In coastal areas, a better understanding of tidal range, timing, exchange volume, channel geometry and converter requirements could also make intentionally managed flows practical.
If technically, environmentally and economically validated, these natural and engineered approaches could make in-stream energy practical in more locations—and easier to replicate and adopt worldwide.
The in-stream and tidal energy industries are moving from demonstrations toward larger arrays and commercial projects. Ocean Energy Europe reports a growing pipeline of pre-commercial farms as the industry works to reduce costs, improve reliability and expand deployment. However, widespread commercial adoption remains limited.
Key challenges
This is because many in-stream and tidal technologies require specific combinations of current velocity, depth, site geometry and environmental conditions. The Pacific Northwest National Laboratory (PNNL) also identifies cost, installation, maintenance, environmental effects and limited suitable locations as barriers to broader deployment. Together, these challenges can limit widespread adoption. One path toward wider adoption may be greater adaptability. Standardizing energy converters around planned flow ranges and, where required and appropriate, engineering repeatable flow conditions to match them could address several of these barriers. Technologies capable of operating near the surface in natural, slower-moving waterways could further simplify deployment, access and maintenance.
Brisbane Lagoon: A Measured Example
Field measurements at Brisbane Lagoon on San Francisco Bay provide a useful example. During a tidal change of only about 3.5 feet, two parallel constructed channels, each approximately 10 by 10 feet and 150 feet long, carried incoming water at approximately 6 to 9 ft/sec for more than four hours.
These data demonstrate that a modest tidal change can produce sustained higher-velocity flow when a large exchange volume is concentrated through constructed passages.
The relationship should also scale with larger tidal exchanges. A preliminary model based on the measured Brisbane flow profile found that a 15-foot tidal range with two 20-by-20-foot channels could remain above 6 ft/sec for about four hours and above 5 ft/sec for about six hours of an eight-hour exchange.
The potential value of developing these flows can also be seen in measured drag forces. Independent instrumented testing of a six-foot Fiorentino para-anchor recorded approximately 950–1,000 pounds of drag at 4.7 ft/sec and 1,750–1,850 pounds at 6.4 ft/sec. Preliminary HydroChute testing further indicates that a moving collector can retain substantial force while traveling through the water, suggesting that channelized flows in this velocity range warrant further investigation for useful energy extraction.
Engineering Flow Rather Than Head
Unlike conventional tidal barrages, which generally favor tidal ranges of roughly 16 to 33 feet and primarily extract energy from water-level differences, a Managed Tidal-Exchange DER would manage flow in locations with much smaller tidal exchanges. With a standardized converter's preferred flow range and the available tidal resource known, lagoon and channel geometry could be designed to maintain that operating range for as much of the tidal cycle as practical.
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A barrage primarily engineers head. A Managed Tidal-Exchange DER would engineer and manage flow.
Lagoon area determines exchange volume, tidal range and timing provide the driving potential, open-channel dimensions establish the flow regime and standardized converters are selected and spaced for those conditions. A barrage primarily engineers head. A Managed Tidal-Exchange DER would engineer and manage flow.
Multiple channels could provide operating control. More could remain open during strong exchange, as flow declines, fewer could remain open, reducing total flow area and potentially maintaining useful velocity longer to improve capture of the available tidal energy throughout the cycle.
Long channels could support spaced groups of modular converters. Their number and spacing would require hydraulic modeling and field testing, as each device would extract a portion of the available flow energy.
Distributed Energy Resources
Managed Tidal-Exchange DERs could operate individually or as distributed networks. Because tidal timing varies geographically, coastal projects would peak at different times, providing staggered, predictable renewable generation.
Dedicated energy lagoons are one implementation. Another is integrating generating channels into coastal infrastructure for flood protection, sea-level-rise adaptation, habitat restoration, parks or waterfront redevelopment. Renewable generation could then become one benefit of multipurpose coastal infrastructure rather than requiring energy production alone to justify the full construction cost.
Brisbane provides a real-world example. Beginning in 2025, its man-made lagoon became the focus of ongoing planning for habitat restoration, recreation, water management and sea-level-rise adaptation, demonstrating how future tidal DER infrastructure could potentially serve multiple purposes and distribute costs beyond energy generation alone.
Brisbane's tidal exchange supports a productive marine ecosystem. For long-term sustainability, future systems should extract energy without unnecessarily compromising the biological exchange and natural processes that make these waterways productive.
A Global Opportunity
Standardized converters and planned, repeatable flow environments could improve both adaptability and adoptability by simplifying manufacturing, installation, maintenance and replication while reducing dependence on a limited number of naturally ideal sites.
Shallow and surface deployments could expand opportunities in naturally occurring flows such as rivers, canals and tidal or open-ocean currents. In coastal areas, a better understanding of tidal range, timing, exchange volume, channel geometry and converter requirements could also make intentionally managed flows practical.
If technically, environmentally and economically validated, these natural and engineered approaches could make in-stream energy practical in more locations—and easier to replicate and adopt worldwide.
