Posts Tagged ‘Mooring Design’
Advancing Mooring Technology for Long-Term Ocean Observation
Advances in oceanographic mooring technology are critical to sustaining long-term, high-quality observations in some of the planet’s harshest environments. Moorings must now operate reliably over extended deployments, support increasingly sophisticated instrumentation, and withstand the growing impacts of extreme weather. To better understand recent progress and ongoing challenges in this field, we spoke with Alex Franks, Research Engineer at Woods Hole Oceanographic Institution (WHOI) and a key contributor to the Ocean Observatories Initiative (OOI).
Over the past three years, Franks and his team have introduced significant upgrades to OOI infrastructure – most notably enhancements in satellite telemetry, power generation and management systems, and the structural resilience of both surface and subsurface moorings. These improvements aim not only to extend deployment lifetimes and reduce maintenance needs but also to expand the scientific capabilities of moorings by accommodating higher-bandwidth data streams and more energy-intensive instruments.
This Q&A offers a detailed look at the evolving strategies behind mooring system engineering and the practical steps being taken to meet both scientific demands and environmental challenges.
- In the last 3 years, what have been the most notable improvements in remotely diagnosing and fixing mooring issues?
The biggest upgrade we’ve implemented recently is a new satellite telemetry module called the “Stream +” (Stream Plus). This allows us to communicate with the buoys in a faster and more streamlined manner. I would compare the upgrade being the difference between dialup and high-speed internet. This unit was originally tested on the Irminger Sea Surface Mooring deployed in 2024 and has now been deployed at the Pioneer Array on the Central Surface Mooring and one of the Profiler Moorings. With this increased ability to troubleshoot and interact, we are able to support high bandwidth instrumentation like the Mclane IFCB (Imaging Flow Cytobot) which takes pictures of phytoplankton in real time. We are able to download a subset of the images and adjust camera focus remotely now. OOI can now also accommodate proposals for more high bandwidth instrumentation on the buoy systems.
- What new features are you currently developing to further improve mooring system reliability?
The OOI Electrical Engineering group is currently focusing on reducing power consumption and increasing reliability of power generation systems on the Surface Moorings. Several systems are being optimized including individual instrument power supplies and Surface Mooring seabed-located multifunction node (MFN) power transmission. We are also upgrading the solar panels to harvest even more energy from the sun during long deployments. Lastly, the wind turbines on the Surface Moorings have been further ruggedized to help withstand the 20-meter waves and hurricane force winds that we observe at our global sites. A test of that redesign is underway at the Pioneer Array. All of these optimizations and upgrades will result in a mooring that can accommodate new power-hungry instrumentation, exceed our current sampling scheme, and withstand doldrums or high latitude winter with little to no solar generation.
At OOI we are also starting to think about more onboard computing power, more data storage, and more expandability in terms of available ports for new instrumentation. We always have our eye on streamlining our current electronics.
- Looking ahead, what do you see as the next major breakthrough in mooring technology?
I’m looking forward to testing solid state batteries as they are developed for use on mooring systems. The benefits of lithium with less safety concerns are very interesting to me. Losing battery weight and gaining more usable energy storage is a very attractive prospect.
- Are there any upcoming field tests or deployments that you’re particularly excited about?
OOI is partnering with Sandia Labs and the Department of Energy to develop and deploy a prototype of a wave energy converter on the Central Surface Mooring in fall of 2025. This device will be situated inside the buoy and convert wave motion into mooring power as proof of concept. This project has been going on for a few years now and it’s very rewarding to see it coming to fruition.
Advancements in mooring technology are directly improving data quality, reliability, and access for long-term ocean observations.
To explore available datasets and learn more about current system capabilities, visit oceanobservatories.org.
[caption id="attachment_36486" align="alignnone" width="320"]
Compass characterization procedure at the LOSOS building. Pictured: Alex Franks, WHOI[/caption]
Read More New OOI Coastal Surface Mooring Design
The OOI Coastal Surface Moorings (CSMs) showcase a variety of innovative mooring technologies. Although the design concepts were initially developed as elements of other mooring systems, they were brought together for the first time on the OOI CSM. A recent paper by Peters et al. (2022) describes three areas where new design concepts were particularly impactful: (1) components at the interface between the surface buoy and mooring riser, (2) mooring riser components, and (3) an integrated seafloor anchor and instrument frame. These components work together to provide mechanical integrity for the mooring as well as mounting points for instrumentation and a reliable electrical pathway for the transmission of power from the surface to the seafloor and data from the seafloor to the buoy (Figure above).
Components comprising the buoy-to-riser interface include a universal joint, an electro-mechanical (EM) chain, and a Near Surface Instrument Frame (NSIF). The universal joint, at the buoy base, reduces the translation of buoy pitch and roll motion into bending moments at the top of the mooring riser. The EM chain, a conventional chain wrapped with helically-wound conductors and encapsulated in urethane, provides a flexible strength member between the buoy and the NSIF. The NSIF provides a mounting point for instruments and a mechanical transition from the EM chain to the EM cable.
Components along the mooring riser include the EM cable, EM stretch hoses, and distributed buoyancy elements between stretch hoses. The EM cable employs a wire rope strength member mechanically terminated with a swaged fitting. A molded urethane strain relief boot at the upper end of the cable interfaces with the NSIF bellmouth. The lower termination assembly provides strain relief and a cavity for integration of underwater connectors. The EM stretch hoses were initially developed in the 1990s by WHOI engineer Walter Paul. A novel, multi-layer construction technique was developed for OOI to enable a 24-conductor stretch hose. Hose lengths from 9 to 30 m are employed on OOI moorings. Each hose has a breaking strength of over 10,000 lb and stretches to over twice its original length to provide variable mooring scope and reduction of peak dynamic loads.
At the buoy base is an integrated anchor and instrument frame assembly called the Mult-Function Node (MFN). The MFN frame is a buoyant structure made of air-filled aluminum pipe, configured to allow the mounting of instruments, data loggers and batteries. The MFN is weighted to the seafloor with an anchor assembly that sits in the center of the frame, connected with dual acoustic releases. The anchor assembly consists of a flat-plate anchor below a foam buoyancy element that contains an internal spool with several hundred meters of synthetic line. The buoyancy element is connected to the anchor with dual acoustic releases. This system allows for mooring and anchor recovery in three stages: First, the MFN is separated from the anchor and the mooring riser is recovered. Next, the buoyancy element is released from the anchor allowing it to rise to the surface while offspooling line. Finally, the anchor is hauled using the synthetic line.
This unique combination of design elements creates a mooring system capable of housing and powering complex instrument systems, transmitting data in near real-time, and contributing to the long-term reliability of the OOI Coastal Surface Moorings in the challenging environment of the continental shelf.
Peters, D.B, J.N. Kemp and A.J. Plueddemann (2022). Coastal Surface Mooring Developments for the Ocean Observatories Initiative (OOI). Marine Technol. Soc. J., 56(6), 70-74. doi.org/10.4031/MTSJ.56.6.2.
Read More