PRIMRE/Telesto/Metrics

From Open Energy Information

< PRIMRE‎ | Telesto

Metrics

Marine Energy Performance Metrics

Feedback

Explore Marine Energy Performance Metrics

To adequately analyze Marine Energy (ME) applications and advance ME technologies toward commercialization, relevant performance metrics must be properly assessed. These metrics are a necessary input for evaluating the economic and technical potential of ME technologies, tracking the evolution and growth of ME technologies, and guiding ME research and development and programs. These metrics can provide invaluable insights for developers and energy professionals, however if they are applied with unwarranted optimism or excessive conservatism, they will give misleading and erroneous results. These metrics must be applied objectively without bias to be useful.

This page provides information about commonly used metrics to evaluate ME systems. The metrics guidance serves as a reference for relevant information concerning ME systems.

Search the Metrics


Filter Results By:
Technology
Application
Technology Readiness Level
Codes and Standards


Anchor Footprint Area

Anchor footprint area is defined as the area on the horizontal plane occupied by a polygon whose vertices are the anchor locations.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Anchor coordinates
  • Undisplaced floating device coordinates


Units: m2


Codes and Standards: N/A

Annual Absorbed Energy per Characteristic Mass

Annual absorbed energy per characteristic mass is a cost-performance metric. Characteristic mass is a cost indicator for the capital costs of the energy converter structure. Annual absorbed energy per characteristic mass can be considered a proxy for LCOE at low TRLs when LCOE data are not available.

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Absorbed energy: total energy (in kilowatt-hours) absorbed in a year
  • Characteristic mass: total mass (in kilograms) of the energy absorber (see assumptions)


Units: kWh/kg


Codes and Standards: IEC

Annual Absorbed Energy per Unit of Characteristic Power Take-Off Force

Annual absorbed energy per unit of characteristic power take-off (PTO) force is a cost-performance metric. It is a benefit-to-cost proxy ratio. The higher the PTO forces, the more expensive the PTO system will be, and therefore this is a cost indicator of the PTO.

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Annual absorbed energy: total energy absorbed in a year (in kilowatt-hours);
  • Characteristic PTO force, options: RMS or peak PTO force value over a year (in newtons).


Units: kWh/N or kWh/N∙m


Codes and Standards: N/A

Annual Absorbed Energy per Wetted Surface Area

Annual absorbed energy per wetted surface area is a cost-performance metric introduced. It is a proxy for benefit-to-cost ratio. Wetted surface area is the surface area of the device below the waterline and is a cost indicator of the structure and of its operations and maintenance (O&M).

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Annual absorbed energy: total energy absorbed in a year (in kilowatt-hours)
  • Wetted surface area: surface area (in square meters) of the device below the waterline.


Units: kWh/m2


Codes and Standards: IEC

Annual Energy Production

Annual energy production (AEP) is the total energy generated by an asset or farm over the course of one year. The quantity can be estimated a priori or measured a posteriori in a wave tank test of a subscale model device.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: N/A


Units: kWh or MWh


Codes and Standards: IEC

Availability

Availability is a measure of the time a device is technically capable of delivering energy over a period. It is represented as a percentage. Factors that impact availability include device failure rates, device repair durations, and curtailment periods. Availability can be specific to a generating device or can include balance of plant and interconnection as well.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Laboratory, Field




Units: %


Codes and Standards: IEC, IEEE Std

Average Climate Capture Width to Characteristic Capital Expenditure

The ratio of average climate capture width (ACCW) to characteristic capital expenditure (CCE) metric, otherwise known as ACE, was developed specifically for the 2016 DOE Wave Energy Prize as a low-TRL proxy for the levelized cost of energy. ACE was intended to be used with the hydrodynamic performance quality (HPQ) metric.

Technology: Wave


Application: Device


Technology Readiness Level: 1-3


Relevant Scale: Laboratory, Field


Required Inputs:
  • Average climate capture width
  • Characteristic capital expenditure
  • Manufactured material cost per unit mass
  • Representative structural thickness of material


Units: m/$1,000,000


Codes and Standards: N/A

Capacity Factor

Capacity factor (CF) is a measure of the energy produced by a generating unit in a given period relative to its maximum generation as defined by its maximum (rated) capacity times the duration of the period. Capacity factor can be gross or net capacity factor depending on the gross or net basis used for unit capacity.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Actual generation
  • Hours in the period
  • Maximum capacity (net or gross)


Units: %


Codes and Standards: IEC, IEEE Std

Capture Width

Capture width (CW), also known as capture length, is the ratio of the power absorbed by a device to the wave energy flux.

Technology: Wave


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: N/A


Units: m


Codes and Standards: IEC

Capture Width Ratio

Capture width ratio (CWR) is the ratio of the capture width (CW) to the characteristic dimension of the device. It’s commonly expressed as a percentage and referred to as relative capture width and hydrodynamic efficiency in literature.

Technology: Wave


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:


Units: %


Codes and Standards: IEC

Characteristic Dimension

The characteristic dimension, also known as the characteristic width, characteristic length, or characteristic diameter, is used to describe the size of the wave energy converter.

Technology: Wave


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: This metric requires physical measurements of the device


Units: m


Codes and Standards: N/A

Coefficient of Drag or Thrust

Coefficient of drag or thrust (CD/T) is a nondimensional parameter that represents the ratio of force parallel to the apparent or relative direction of flow acting on an object or feature to the nominal fluid force that may act over its projected area facing the flow.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Drag or thrust force on a body
  • Fluid density
  • Projected area aligned with relative or apparent flow direction
  • Relative or apparent flow speed


Units: Nondimensional


Codes and Standards: N/A

Coefficient of Lift

Coefficient of lift (CL) is a nondimensional parameter that represents the ratio of force perpendicular to the apparent or relative direction of flow acting on an object or feature to the nominal fluid force that may act over its projected area facing the flow. This force is referred to as the lift force if the force tends toward opposing gravity.

Technology: Wave, Tidal, Ocean, River


Application: Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Lift or downforce on a body
  • Fluid density
  • Projected area aligned with relative or apparent flow direction
  • Relative or apparent flow speed


Units: Nondimensional


Codes and Standards: N/A

Coefficient of Performance

Coefficient of performance, also known as coefficient of power, is a nondimensional parameter representing the kinetic energy conversion efficiency of a current energy conversion device. It is derived and defined identically for hydrokinetic and wind systems. It is defined as the ratio of mechanical power generated by a turbine or similar device to the available power of the flow.

Technology: Tidal, Ocean, River


Application: Array, Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Drag or thrust force on a body
  • Fluid density
  • Projected area aligned with relative or apparent flow direction
  • Relative or apparent flow speed


Units: Nondimensional


Codes and Standards: IEC

Coefficient of Torque

Coefficient of torque is a nondimensional parameter that represents the torque of a current energy turbine or similar device as a fraction of the maximum torque that may exist at the same radial distance as a result of fluid forcing through an area.

Technology: Tidal, Ocean, River


Application: Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Turbine hydrokinetic torque
  • Turbine radius
  • Fluid density
  • Turbine projected area
  • Undisturbed upstream flow speed


Units: Nondimensional


Codes and Standards: N/A

Levelized Avoided Cost of Energy

Avoided cost is the cost for the grid to meet energy demand from technologies that would otherwise be replaced by a new technology. The calculation of the levelized avoided cost of energy (LACE) requires tools to simulate the operation of the project being evaluated within its particular regional power system.

Technology: Wave, Tidal, Ocean, River


Application: Array


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs: The simplest required inputs are data on the annual cost change for each member of the generation fleet that will be affected by new generation technology.


Units: $/kWh or $/MWh


Codes and Standards: N/A

Levelized Cost of Data

Levelized Cost of Data (LCOD) is defined as the annual average total system cost per unit data stored over the lifetime of the asset or plant, accounting for financing assumptions. It is similar to other levelized cost of commodity estimates, such as the levelized cost of water.

Technology: Wave, Tidal, Ocean, River


Application: Array


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Initial cost per installed data transmission
  • Fixed charge rate
  • Operations and maintenance
  • Annual total data transmitted


Units: $/B


Codes and Standards: N/A

Levelized Cost of Energy

Levelized cost of energy (LCOE) is the total system cost per unit of electricity generated based on annual average values, assumed project economic life, and financing—or the rate that one must sell electricity over a given time period in order to break even on an investment. It’s a standardized cost and performance metric used to evaluate energy generation technologies.

Technology: Wave, Tidal, Ocean, River


Application: Array


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Levelized cost of energy
  • Capital expenditures or initial capital cost
  • Fixed charge rate
  • Operational expenditures or operations and maintenance
  • Annual energy production


Units: $/kWh or $/MWh


Codes and Standards: IEC

Levelized Cost of Water

The levelized cost of water (LCOW) is the total system cost per unit of water produced based on annual average values, assumed project economic life, and financing.

Technology: Wave, Tidal, Ocean, River


Application: Array


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Levelized cost of energy
  • Capital expenditures or initial capital cost
  • Fixed charge rate
  • Operational expenditures or operations and maintenance
  • Annual energy production


Units: $/m3


Codes and Standards: N/A

Manufacturing Readiness Level

Manufacturing readiness level (MRL) was introduced by the U.S. Department of Defense (DOD) to manage the risk in the acquisition of weapons technology in transition from development to full-scale production. This measure can be translated into the marine hydrokinetic (MHK) energy field to allow reviewers to uniformly analyze the manufacturing maturity of various MHK technologies.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Technology and the Industrial Base: Requires an analysis of the capability of the national technology and industrial base to support the design, development, production, operation, uninterrupted maintenance support of the system and eventual disposal (environmental impacts). Sub-threads:
    • Industrial Base
    • Manufacturing Technology Development.
  • Design: Requires an understanding of the maturity and stability of the evolving system design and any related impact on manufacturing readiness. Sub-threads:
    • Producibility Program
    • Design Maturity.
  • Cost and Funding: Requires an analysis of the adequacy of funding to achieve target manufacturing maturity levels. Examines the risk associated with reaching manufacturing cost targets. Sub-threads:
    • Production Cost Knowledge (Cost Modeling)
    • Cost Analysis
    • Manufacturing Investment Budget.
  • Materials: Requires an analysis of the risks associated with materials (including basic/raw materials, components, semifinished parts, and subassemblies). Sub-threads:
    • Maturity
    • Availability
    • Supply Chain Management
    • Special Handling.
  • Process Capability and Control: Requires an analysis of the risks that the manufacturing processes can reflect the design intent (repeatability and affordability) of key characteristics. Sub-threads:
    • Modeling and Simulation
    • Manufacturing Process Maturity
    • Process Yields and Rates.
  • Quality Management: Requires an analysis of the risks and management efforts to control quality and foster continuous improvement. Sub-threads:
    • Quality Management
    • Product Quality
    • Supplier Quality Management.
  • Manufacturing Workforce (Engineering and Production): Requires an assessment of the required skills, availability, and required number of personnel to support the manufacturing effort.
  • Facilities: Requires an analysis of the capabilities and capacity of key manufacturing facilities (prime, subcontractor, supplier, vendor, and maintenance/repair). Sub-threads:
    • Tooling Special Test and Inspection Equipment
    • Facilities.
  • Manufacturing Management: Requires an analysis of the orchestration of all elements needed to translate the design into an integrated and fielded system (meeting program goals for affordability and availability). Sub-threads:
    • Manufacturing Planning and Scheduling
    • Materials Planning


Units: Unitless


Codes and Standards: N/A

Mean Time to Failure

The mean time to failure (MTTF) is used to evaluate the reliability/ dependability of equipment. MTTF is defined as the probability of a system or system element performing its intended function under stated conditions without failure for a given time period. Failure Rate (probability of failure per unit time) is the inverse of MTTF.

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Number of units tested or number of failures observed
  • Time until failure occurs


Units: Time (e.g., hours, days, or months)


Codes and Standards: N/A

Mean Time to Install

The mean time to install (MTTI) measures the length of time that is required to install a piece of equipment. The duration of installation should begin at mobilization of equipment for the installation process and end when the system is functioning as intended. MTTI is calculated through actual in-field data by recording the duration of installation activities.

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Number of installations observed
  • Time duration of installation


Units: Time (e.g., hours, days, or months)


Codes and Standards: N/A

Mean Time to Repair

Mean time to repair (MTTR) is defined as the average time to repair a system between failure and redeployment. A failure is defined as any time when the system is not performing its intended function. A repair is complete once the system has been returned to the expected operating condition.

Technology: Wave, Tidal, Ocean, River


Application: Device


Technology Readiness Level: 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Number of repairs
  • Time duration of repair


Units: Time (e.g., hours, days, or months)


Codes and Standards: N/A

Mooring Footprint Area

Mooring footprint area (MFA) is defined as the area on the horizontal plane that the mooring lines sweep across under the full expected system range of motion. This range of motion is defined by the system’s watch circle. The metric serves as a measure of how much horizontal area is directly blocked by the device, excluding area between mooring lines.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Anchor coordinates
  • Undisplaced floating device coordinates
  • System watch circles


Units: m2


Codes and Standards: N/A

Mooring Peak Tension Ratio

Mooring peak tension ratio (MPTR) is the ratio of the largest instantaneous tension expected within a mooring system to the steady tension at that point in the system under unloaded conditions. It is a measure of how dynamic a mooring system is, or the range of tension the system will experience.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs:
  • Computation of the largest peak tension in the mooring system under worst-case intact conditions, likely from a suite of coupled dynamics analyses
  • Computation of the tension at the same location in the mooring system under unloaded conditions


Units: Unitless


Codes and Standards: API-RP

Mooring Strength-Length Product

Mooring strength-length product (MSLP) is defined as the summation of the minimum breaking strength and length of each mooring line. It indicates the combined strength and length demands on the mooring lines and can serve as a rough proxy for the total mooring line material cost.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs: N/A


Units: N∙m


Codes and Standards: ABS, API-RP, DNV

Normalized Breaking Strength

Normalized breaking strength (NBS) is defined as the breaking strength normalized by the squared diameter. This breaking strength per nominal diameter squared can be used for comparative review of mooring material characteristics for conditions where it is likely to perform optimally.

Technology: Wave, Tidal, Ocean, River


Application: Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs: N/A


Units: N/mm2


Codes and Standards: N/A

Normalized Submerged Weight

Normalized submerged weight (NSW) is a mooring line’s submerged weight per unit length normalized by the diameter squared. Normalized submerged weight can be used to compare the wet weight of different mooring line materials.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Field


Required Inputs: N/A


Units: N/m/mm2


Codes and Standards: N/A

Peak-to-Average Power Ratio

Peak-to-root-mean-square power ratio is a single term describing how many times greater the instantaneous peak power output is relative to the root-mean-square (RMS) power. This is a unitless ratio based on statistics of the power time series. The ratio can refer to any point within the electrical power take-off and power conditioning.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Peak power (maximum power)
  • Average power (root-mean-square power)


Units: Unitless


Codes and Standards: IEC

Power Capture

Power capture defines the generated power (i.e., useful power to user) of an energy converter device. Power absorption is the measured quantity and can be calculated for theoretical devices using analytical formulations or via numerical simulation. It is a main performance metric of energy converter devices and is typically a component of the numerator in performance per cost metrics.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Power: electrical power output, either immediately from the PTO (not necessarily grid-compliant) or at the point of grid connection (including conditioning)


Units: W


Codes and Standards: IEC

Power Conversion Efficiency

The power conversion efficiency (also known as power take-off efficiency) is the ratio of electrical power output to mechanical power into the power take-off. It can be measured either directly at the output of the PTO, or as grid-compliant (including conditioning).

Technology: Wave, Tidal, Ocean, River


Application: Array, Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:
  • Pelectrical: electrical power output, in kilowatts, either immediately from the PTO (not necessarily grid-compliant) or at the point of grid connection (including conditioning)
  • Pmechanical: mechanical power input, in kilowatts, to the PTO system. This is typically from kinetic sources and measured in terms of force times velocity (P=F∙v) or torque times angular velocity (P=τ∙ω)


Units: Unitless


Codes and Standards: IEC

Power-to-Weight Ratio

The power-to-weight ratio (PWR) is a measurement of the mechanical or electrical power output normalized by the mass of the system. PWR provides a proxy metric for benefit-to-cost assessments for low-TRL technologies by comparing the power output (benefit) to the mass of the system (cost).

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs:


Units: kW/kg


Codes and Standards: N/A

Rated Power

Rated power (or rated capacity, nameplate capacity, installed capacity, nominal capacity, maximum rated output) is the maximum output of electricity for a component, subsystem, device, or plant adjusted for ambient conditions. This is a manufacturer- and/or developer-provided number, often determined by a limiting component or process within a given system.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device, Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: N/A


Units: kW


Codes and Standards: IEC

Robustness (Control System)

Robustness refers to the ability of a control system to maintain closed-loop stability and desired closed-loop performance despite the presence of uncertainties such as modeling errors and external disturbances. Robustness as a metric for MHK control consists of multiple sub-metrics that describe how a control system performs with respect to different types of uncertainties.

Technology: Wave, Tidal, Ocean, River


Application: Subsystem


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: Actual performance of an MHK device, such as power output or tracking error, along with desired or expected performance of the device are the most common input quantities needed to compute robustness. When expressed as a sensitivity of the device output to changes in key parameters (examples include model uncertainty, sensor noise, variations in control gains, etc.), the inputs should consist of a table of output values obtained from the device (or model of the device) corresponding to the parameter value(s) for that particular output value.


Units: Dimensionless


Codes and Standards: IEC

Technology Performance Level

Technology Performance Level (TPL) is a weighted score from 0-9 that ranks a developer’s technology. A culminative approach of grading the technology, that isn’t exclusively based on mechanical or commercial readiness, is achieved using seven capability categories. Technology Performance Level is also a design tool used during the iterative development process and is an aid to investors making funding decisions.

Technology: Wave, Tidal, Ocean, River


Application: Array, Device


Technology Readiness Level: 1-3


Relevant Scale: Laboratory, Field


Required Inputs: First, the user must gather quantitative technical data regarding the system in eight categories:
  • 1. General: This section should provide the assessor with a high-level overview of the technology, its working principles, dimensions, range of configurations for different operating and survival states, major components, and layout in a farm.
    • Working principle
    • Operating configuration
    • Survival configuration
    • Power take-off
    • Stationkeeping
    • Array layout and balance of system (BOS)
  • 2. Design: The design philosophy, design basis including all assumptions, environmental conditions, etc., standards and guidelines used, tools used, etc. should be discussed.
  • 3 .Manufacture, Assembly, Installation, and Maintenance: This section should provide assessors with an understanding of steps needed to take a converter concept from raw materials and components to full operation and maintenance plans. This includes the associated costs resulting from the evolution of raw materials and components, to a fully operational WEC with resulting maintenance schedule.
  • 4. Performance: This section should provide the assessor with a quantitative measure of the ability of the WEC to capture and convert wave power, including power capture, conversion efficiency, and availability factor.
  • 5. Cost: While it is still too early to perform a comprehensive LCOE determination, estimates should be provided to help the assessor determine the associated estimates of CapEx and OpEx costs.
  • 6. Benefits to Society: Beyond the techno-economic feasibility, the development of the WEC and the farm for which it will be used should have both tangible and intangible benefits to (1) local communities, (2) the environment, and (3) society. This section requests information to help the assessor’s understanding of the broader impacts of the WEC and its use in a wave energy farm.
  • 7. Permitting, Environmental, and Conflict Issues: Information is needed to understand the potential for environmental, wildlife, and other user conflicts that can impact permitting and areas where the WEC can be used.
  • 8. Safety: Safety of people and property is a priority in any commercial activity. Provide information on the dangers from the installation and operation of the WEC farm to the people working there and others who may also use the same area. Provide information on how those dangers will be mitigated. The answers in this section should provide the assessor with an understanding of the risks posed by the WEC throughout its life cycle to personnel and equipment.
If the user is not able to calculate certain quantities for their technology, some references, examples, and guidance are provided to estimate them (lower level of fidelity). Next, this data is employed in conjunction with the scoring guidance for each question to determine the score (1–9, integers only) for each question. Finally, the user inputs both the question score and their level of confidence with that score into the assessment tool.


Units: Unitless


Codes and Standards: IEEE Std, ISO

Watch Circle Diameter

The watch circle of a moored, floating device is its horizontal motion envelope across all expected load cases. Watch circle diameter (WCD) is defined as the diameter for round watch circles or major axis length for elliptical watch circles. It is a measure of the station keeping capability of a floating system.

Technology: Wave


Application: Array, Device


Technology Readiness Level: 1-3, 4-6, 7-9


Relevant Scale: Laboratory, Field


Required Inputs: The watch circle diameter metric requires data on the device’s horizontal displacements under the range of expected load cases, including all loading directions. The watch circle can be measured while the device is deployed. For example, the watch circle can be computed from GPS-measured time series of the device coordinates. If measurements are not available, it can be estimated based on numerical modeling of the mooring system and the expected loads on the device.


Units: m


Codes and Standards: N/A