Planning a Bankable Metocean Current Measurement Campaign for Offshore Wind

Executive Summary

A six-month project delay caused by insufficient current data can cost a wind farm developer tens of millions in re-design, re-consenting, and lost revenue. A properly designed ADCP measurement campaign, by contrast, represents less than 0.1% of total project capital expenditure.¹

The arithmetic is straightforward. The execution is not.

This white paper provides a structured framework for planning an offshore wind current measurement campaign that satisfies financiers, insurers, and engineering teams alike. It covers:

1. Where to measure — spatial coverage logic and deployment density recommendations
2. How long to measure — minimum and best-practice durations by project phase
3. What to measure — vertical profiling requirements and frequency selection
4. How to ensure reliability — redundancy strategies and risk mitigation
5. Instrument selection — a decision framework for ADCP frequency, deployment mode, and mooring configuration
6. A 22-step campaign planning checklist — from desktop study to final data delivery

The guidance in this paper draws on lessons from metocean campaigns across North Sea, Irish Sea, and Asia-Pacific offshore wind projects, and reflects alignment with the IMarEST Metocean Procedures Guide (2024), DNV-ST-0437, and IEC 61400-3.

Oceantek provides ADCP and DVL instruments deployed in offshore wind measurement campaigns globally. This paper reflects practical experience from those deployments — it is not a sales document. Where Oceantek products are referenced, they appear because they match the technical requirements described, not the other way around.

1. Why Current Data Fails — And What It Costs

1.1 The Cost Asymmetry

Every offshore wind project measures wind. Not every project measures current with the rigour it deserves. When current data is absent, inadequate, or misinterpreted, the consequences propagate through design, construction, and operations — often silently until a failure occurs.

¹ Industry estimate based on typical North Sea project data; foundation re-design costs vary widely depending on project scale and whether fabrication has already commenced.

² Average export cable repair cost: $24 million (US/European data); average cable repair generally: €5 million per repair (2016 benchmark). Sources: GCube Insurance, international offshore engineering cost databases.

³ Industry estimate based on typical North Sea project data; individual incident costs vary significantly by vessel type and project phase.

1.2 The Regulatory Floor Is Not the Ceiling

Standards such as IEC 61400-3 (Design requirements for offshore wind turbines) and DNV-ST-0437 (Loads and site conditions for wind turbines) specify minimum metocean data requirements. These minima are designed to provide a baseline of safety and are periodically updated by technical committees.

They are not designed to satisfy project financiers or insurers.

Regulators specify what you must do. Financiers and insurers care about what you should do.

In practice, lender’s technical advisors (LTAs) and insurance underwriters increasingly expect current measurement campaigns that exceed regulatory minima:

The gap between these two columns represents project risk. A campaign designed to the regulatory minimum leaves the developer exposed to LTA objections during due diligence, potentially delaying financial close by months.

1.3 The Insurance Perspective

GCube Insurance, the leading underwriter for renewable energy projects globally, published its decade-long analysis of offshore wind claims in the report “Uncharted Waters: Navigating Emerging Risks and Rising Claims in Global Offshore Wind” (covering 2010–2020). Key findings relevant to current measurement include:

• Subsea cables accounted for over 50% of total claims spend across the decade, with an average cable claim settlement of approximately £9 million.²
• 44% of cable claims spend was attributed to contractor error during transit and laying — much of which relates to operation in currents exceeding installation design assumptions.
• Total market losses from offshore wind claims reached £500 million by 2020, with average claim values nearly doubling from £1.67M (2010–2015) to £3.08M (by 2020).
• By 2021, GCube’s “Vertical Limit” report documented that average offshore wind losses had escalated further to over £7 million per claim.³

Not all cable claims are current-related. But current is a direct contributor to cable installation risk (cross-current during laying), burial adequacy (sediment mobility driven by near-bed currents), and long-term exposure (scour at cable crossings). An ADCP measurement campaign that properly characterises these currents is, in insurance terms, a risk mitigation measure — and is increasingly factored into underwriting decisions.

2. The Four Pillars of Campaign Design

Any metocean current measurement campaign for offshore wind can be evaluated against four dimensions. Weakness in any one pillar compromises the entire dataset — and, by extension, the engineering and financing decisions that depend on it.

Pillar 1: Spatial Coverage — How Many Locations and Where?

1a. The Logic of Spatial Sampling

You do not need an ADCP at every turbine location. But you do need enough spatial coverage to answer two fundamental questions:

1. Is the current regime spatially uniform across the site, or does it vary significantly?
2. If it varies, can the variability be characterised from a limited set of measurement points?

1b. Recommended Deployment Density

¹ Recommended ADCP locations are indicative. Final spatial layout should be informed by a site-specific hydrodynamic desktop study and, ideally, a preliminary model sensitivity analysis. Industry estimate based on typical North Sea project data.

1c. Placement Strategy

• Upstream/downstream pairs: Deploying two ADCPs along the dominant current axis captures how the current evolves as it crosses the site — invaluable for cable route characterisation.
• At proposed met mast / floating LiDAR locations: Co-locating current measurement with wind measurement de-risks two datasets simultaneously.
• Along the export cable route: At minimum, one ADCP should be positioned along the cable route at landfall, seabed transition zones, and cable crossing points.
• Avoid: placing the only ADCP in the lee of a sandbank, behind a headland, or in a known eddy zone — unless characterising that specific feature is the objective.

Pillar 2: Temporal Coverage — How Long to Measure?

2a. The Annual Cycle Problem

Currents in temperate shelf seas vary seasonally. Summer stratification can produce a two-layer flow regime that disappears in winter when the water column mixes. Storm-driven currents in winter can be two to three times stronger than mean summer currents.

If your measurement campaign only covers one season, you are not measuring the current regime — you are measuring one quarter of it.

At a North Sea site in ~45m water depth, a 3-month summer ADCP deployment recorded a mean near-surface current speed of 0.32 m/s, with a maximum recorded speed of 0.81 m/s. When the deployment was extended through winter (at the insistence of the LTA), the mean near-surface current rose to 0.68 m/s, and a storm event in January recorded a sustained current of 1.42 m/s at 10m depth — a value that would have been entirely missed by a summer-only campaign. The winter data changed the 50-year return period current estimate by approximately 35%, which in turn altered the foundation ultimate limit state design load and the scour protection specification.

Industry estimate based on typical North Sea project data; specific project data is confidential.

2b. Recommended Durations by Project Phase

The IMarEST Metocean Procedures Guide (2024) notes that the primary driver of campaign duration is no longer technical feasibility but financier confidence. A single year of measured data, when combined with a validated multi-decadal hindcast model, is generally accepted as the minimum for financial close on projects in well-characterised regions such as the North Sea.⁶ For less-characterised regions (e.g., emerging Asian markets, US East Coast), 18–24 months is increasingly expected.

2c. Sampling Strategy Within the Deployment

Pillar 3: Vertical Coverage — What Part of the Water Column?

3a. Why a Full Profile Matters

Current is a vector that varies with depth. Current speed typically decreases toward the seabed (following a logarithmic or power-law shear profile), but stratification, internal waves, and bathymetric steering can produce complex profiles that a single-point measurement cannot capture.

A single-point current measurement at 5m depth, when used as a proxy for the full water column in a foundation bending moment calculation, can produce errors in the range of 15–30% compared to using a measured current profile.¹

3b. What Matters at Each Depth Layer

For fixed-bottom turbines in 30–60m water depth — the majority of installed offshore wind capacity globally — a 300kHz ADCP provides full water-column profiling with 1–2m vertical resolution, capturing all three depth layers in a single instrument.

3c. ADCP Frequency and Vertical Coverage

¹ Typical range figures assume clear water and standard backscatter conditions. Actual range varies with water clarity, suspended sediment concentration, and instrument settings. For planning, use 70–80% of the stated maximum range as a conservative deployment envelope.

Pillar 4: Reliability — What Happens When an Instrument Fails?

4a. The Single-Point-of-Failure Problem

Consider this scenario: a developer deploys a single ADCP at a single location for a 12-month metocean campaign. At month 4, trawl damage severs the mooring. The ADCP is lost. The dataset — and the project’s current characterisation — is 33% complete.

The developer now faces:

• A 6–8 month gap before a replacement can be procured, permitted, and deployed
• An incomplete dataset that does not capture the full seasonal cycle
• A lender’s technical advisor who flags the data gap in the due diligence report
• Potential delay to financial close

The cost of in-water intervention — vessel mobilisation, ADCP procurement or rental, re-deployment — is in the range of $50k–$200k¹ depending on location and instrument type. But the consequential cost of delayed FID dwarfs the intervention cost.

4b. Redundancy Strategies

¹ Cost multipliers are indicative. Industry estimate based on typical North Sea project data. Actual costs vary with water depth, distance from port, and instrument configuration.

4c. The Insurance and Financing Implication

Lender’s technical advisors are increasingly asking two specific questions during due diligence:

1. “What was your redundancy strategy for the current measurement campaign?”
2. “What data gaps occurred, and how were they addressed?”

A documented redundancy plan — even a modest one such as staggered deployments — provides a defensible answer. In the current insurance market, where premiums for offshore wind construction have hardened considerably (GCube reports total market losses of £500 million by 2020, with average claims nearly doubling in five years²), demonstrating robust risk management in the measurement campaign can positively influence underwriting terms.

3. Instrument Selection Logic

3.1 Decision Framework

The following decision table provides a structured path from site characteristics to instrument recommendation.

The 300kHz ADCP is the workhorse for offshore wind metocean campaigns. Its profiling range (100–150m) covers the full water column at the 30–60m depths where most fixed-bottom turbines are installed.

3.2 Frequency Comparison: 600 kHz vs. 300 kHz vs. 75 kHz

¹ Ping-level precision. Ensemble-averaged precision improves with the square root of the number of pings per ensemble.

3.3 Direct-Reading vs. Self-Contained: The Real Trade-offs

3.4 Mounting and Mooring Configurations

Three configurations cover most offshore wind ADCP deployment scenarios.

Configuration A: Bottom-Mounted Frame (Shallow Water, Upward-Looking)

Best for: Water depths ≤50m; self-contained deployments of 3–12 months.
Key considerations: Frame must resist current drag and trawl snag loads. Gimbal mount maintains ADCP within pitch/roll tolerance (±15°). Acoustic release on the frame enables recovery without diver intervention.

Configuration B: Sub-Surface Taut-Line Mooring (Mid-Depth)

Best for: Water depths 30–80m; deployments where surface expression is undesirable.
Key considerations: Sub-surface buoy must be deep enough to avoid vessel interaction (5–10m below surface in North Sea). Taut-line minimises instrument motion but motion correction should still be applied in post-processing.

Configuration C: Seabed Frame with Surface Telemetry Buoy (Real-Time)

Best for: Any depth where real-time data is required; construction support; critical single-point deployments.
Key considerations: The cable is the single most vulnerable component — must be armoured and, in high-traffic areas, buried. Buoy requires periodic maintenance (solar panel cleaning, navigation light checks). Highest-cost configuration.

4. Data Management and Deliverables

4.1 What the End User Actually Needs

The developer and their engineering team do not need raw beam velocities in proprietary binary format. They need actionable, quality-controlled data products:

4.2 QA/QC Protocol

4.3 Deliverable Formats

5. Budget and Value

5.1 Order-of-Magnitude Campaign Costs

¹ Industry estimate based on typical North Sea project data. Cost components include: ADCP instrument (procurement or rental), mooring/frame hardware, vessel days for deployment and recovery (CTV day rates in the range €5,500–€8,000 as of 2024–2025; source: Clarksons offshore vessel index and publicly disclosed Baltic tender data⁴), data processing and reporting, and contingency. Actual costs vary significantly with water depth, distance from port, and local vessel market conditions.

² Based on total development CAPEX for a typical 500MW–1GW offshore wind project. Full metocean data & monitoring is estimated at approximately 0.5% of CAPEX (source: Atkins, 2018⁵); the ADCP current measurement component is a subset of this.

Cost drivers in descending order of impact:

1. Number of deployment locations and instruments
2. Vessel day rates (highly region-dependent; North Sea higher than SE Asia)
3. Direct-reading vs. self-contained (real-time telemetry adds approximately 40–80% to per-location cost)
4. Deployment duration (incremental cost per additional month is primarily data processing)
5. Redundancy strategy (staggered deployments: ~+20%; co-located pairs: ~+80%)

5.2 The Value Equation

The value of a properly designed ADCP campaign is not in the data — it is in the avoided cost of decisions made on the basis of inadequate data:

¹ Industry estimate based on typical North Sea project data.

² Source: GCube Insurance, “Uncharted Waters” (2020). Headline statistics publicly reported via Windpower Engineering, EnergyPeople, and Modern Power Systems.

The ratio is 5:1 to 50:1 in favour of the measurement campaign. The cost of the ADCP campaign, when expressed as a percentage of total project CAPEX, rounds to zero. When viewed against the cost of getting the current regime wrong, it is one of the highest-return risk-mitigation investments available in the pre-FID phase.

6. Campaign Planning Checklist

The following 22-step checklist is designed as a standalone planning tool.

Pre-Deployment (Steps 1–10)

1. [ ] Define data requirements. Document which current parameters are required, at what depths, to what accuracy, and which engineering decisions they feed into.
2. [ ] Complete a hydrodynamic desktop study. Review existing current data: regional tidal models, nearby measurement campaigns, tidal atlases, satellite altimetry.
3. [ ] Run a preliminary model sensitivity analysis (if available) to identify areas of greatest current uncertainty — these are your priority measurement locations.
4. [ ] Determine the number of ADCP locations using the complexity framework in Section 2, Pillar 1.
5. [ ] Determine deployment duration per location using the phase-based recommendations in Section 2, Pillar 2.
6. [ ] Select ADCP frequency and configuration per location using the decision framework in Section 3.
7. [ ] Design moorings/frames for each deployment location. Ensure adequate ballast for the expected current regime.
8. [ ] Prepare a redundancy plan. Document the chosen strategy, the contingency budget, and the trigger criteria for invoking contingency.
9. [ ] Bench-test all instruments: ping test, pressure test, clock sync, battery voltage, data download test, configuration file backup.
10. [ ] Obtain all required permits: marine licence, Notice to Mariners, navigation marking approval, fisheries liaison.

Deployment (Steps 11–14)

11. [ ] Record deployment metadata: exact position (DGPS), orientation (heading), water depth, time of first ping, instrument serial number, configuration file, battery voltage at deployment.
12. [ ] Verify data return: For real-time systems, confirm data receipt and quality within 48 hours. For self-contained, conduct diver/ROV visual inspection within the first week if possible.
13. [ ] Photograph everything: frame on deck, instrument in frame, deployment over the side, surface buoy (if used), DGPS display with coordinates.
14. [ ] File a deployment report within one week: all metadata, photographs, and any deviations from the deployment plan.

During Campaign (Steps 15–18)

15. [ ] Daily QC check (real-time systems): review for correlation drop, velocity spikes, pitch/roll excursions, echo intensity anomalies.
16. [ ] Mid-campaign service visit (for deployments ≥6 months): clean transducer face and buoy hull, check battery, download partial dataset, inspect mooring.
17. [ ] Monitor for external threats: fishing activity, storm track forecasts, AIS position (surface buoys) during storm season.
18. [ ] Maintain a campaign logbook: service visits, storm passages, anomalies, communications with fisheries or maritime authorities, configuration changes.

Recovery and Processing (Steps 19–21)

19. [ ] Recover instruments safely: confirm acoustic release function; download data immediately; photograph instrument condition before cleaning.
20. [ ] Run the full QC processing pipeline using the protocol in Section 4.2. Document all QC decisions. If data rejection exceeds 10–15% in any depth bin, investigate and document the cause.
21. [ ] Generate deliverables package: QC’d dataset in NetCDF-CF, statistical summary, current rose, extreme value analysis (1-year, 50-year), time series plots, QC report.

Post-Campaign (Step 22)

22. [ ] Archive everything: raw binary data, processed NetCDF files, configuration files, logbook, deployment/recovery reports, QC report, photographs. Store in at least two physically separate locations.

7. Conclusion

Current data quality determines design certainty. Design certainty determines financial close. The relationship is direct: the more confidence you have in your understanding of the current regime, the less contingency — in steel tonnage, in insurance premiums, in financing margins — you carry through the project lifecycle.

A well-planned ADCP measurement campaign is the cheapest insurance a wind farm developer can buy. Its cost is a rounding error in the project CAPEX. The cost of not doing it properly can be measured in tens of millions.

The framework in this paper — four pillars of campaign design, a structured instrument selection logic, a documented QC protocol, and a 22-step checklist — is designed to be applied directly. It reflects lessons from metocean campaigns in the North Sea, the Irish Sea, the Taiwan Strait, and beyond. Follow it, and your current dataset will withstand scrutiny from engineers, lenders, insurers, and regulators alike.

Next Steps

• Discuss your campaign with our engineers: Contact Oceantek
• View the ADCP Product lines: ADCP Products

Appendix A: Glossary

Appendix B: Key References

• IEC 61400-3 — Wind energy generation systems — Part 3: Design requirements for offshore wind turbines
• DNV-ST-0437 — Loads and site conditions for wind turbines (Det Norske Veritas)
• IMarEST — Metocean Procedures Guide for Offshore Wind (2024 edition). Institute of Marine Engineering, Science & Technology.
• Carbon Trust — Offshore Wind Accelerator (OWA): Floating LiDAR Recommended Practice
• GCube Insurance — Uncharted Waters (2020), and Vertical Limit (2023)
• OceanSITES — Data format and quality control reference manual for time-series oceanographic data

Appendix C: About Oceantek

Oceantek designs and manufactures acoustic Doppler current profilers (ADCPs) and Doppler velocity logs (DVLs) for oceanographic, hydrographic, and underwater navigation applications. Our product range spans 75kHz to 600kHz, in self-contained, direct-reading, and vessel-mounted configurations, deployed in metocean campaigns, offshore wind site assessments, port monitoring networks, and AUV/ROV navigation systems globally.

Contact: Oceantek Engineer Team

Footnotes

¹ Industry estimate based on typical North Sea project data. Values are indicative and intended for campaign scoping purposes. Actual costs vary with site-specific conditions, vessel market rates, and regulatory requirements.

² Source: GCube Insurance, “Uncharted Waters: Navigating Emerging Risks and Rising Claims in Global Offshore Wind” (2020). Headline statistics publicly reported via Windpower Engineering, EnergyPeople, and Modern Power Systems. Full proprietary dataset available to GCube insured clients and brokers.

³ Source: GCube Insurance, “Vertical Limit: When is bigger not better in offshore wind’s race to scale?” (2023). Publicly reported via industry media.

⁴ Source: Clarksons offshore vessel index, 2024–2025; Baltic Sea CTV contract data publicly disclosed by Polenergia/Equinor (October 2024) for the Bałtyk 2 and Bałtyk 3 offshore wind projects.

⁵ Source: Atkins, 2018 — “Friends of Floating: The Future’s Floating” cost breakdown analysis, cited in Carbon Trust / ORE Catapult Floating Wind Cost Reduction pathways.

⁶ Source: IMarEST Metocean Procedures Guide for Offshore Wind (2024). Available via IMarEST at imarest.org.

⁷ ADCP instrument pricing referenced from US EPA technical procurement documentation (2017) and industry market reports. Current manufacturer pricing available on request. Contact oceanadcp.com for current specifications and quotation.

Disclaimer: This white paper is provided for informational purposes. Project-specific engineering decisions should be supported by site-specific data and qualified professional judgement.