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Volume 7 Issue 1
September 2012

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Environmental Measurements for
Marine Renewable Energy Projects

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There is growing optimism for utilizing renewable energy from the ocean, particularly related to offshore wind and hydrokinetic energy sources. Winds are generally unimpeded over the water, and present tremendous potential energy generation capacity. Given the density of water compared to air, waves and currents can be even more powerful energy generators. Capturing energy from prevailing winds over the ocean is proven using wind turbines (Figure 1) in protected and shallow coastal waters. There also are growing opportunities for wind energy projects along the open continental shelf, and into deeper water as technology advances and grid connections are made possible. Hydrokinetic energy projects harness the power of waves and currents utilizing a range of turbine, piston, hydrofoil, and other developing technologies.

Collection of high quality environmental data is essential for successful planning, design, permitting, construction and operation of marine renewable energy projects. At the planning stage, data are required for site selection to ensure a proven source of potential energy exists. For engineering design purposes, site-specific data are required to optimize unit design and layout, and to provide design criteria to ensure a stable and lasting structure in the harsh marine environment. Design parameters may include a 50-, or 100-year water level and wave height for structural integrity, current persistence statistics for structural fatigue analysis, or the anticipated scour depth around a piling. Design criteria studies require sound understanding of oceanographic processes, hinged on high quality data. Measurements also are required to identify and minimize potential environmental impacts so regulatory approvals can be secured. Construction in the ocean requires accurate knowledge of site conditions, and long-term operation of energy generating facilities depends upon ongoing information related to the prevailing environmental conditions.

Types and methods of data collection and measurement technologies are diverse. Wind measurements can be collected using traditional mechanical or ultrasonic sensors mounted at different levels on buoys and towers (Figure 2). There also are new technologies for wind speed and direction data collection using acoustic methods that can profile wind at various levels from one fixed level near the sea surface, thereby saving on tower construction. Current and wave measurements can be collected with single point meters and/or with acoustic Doppler current profiling (ADCP) equipment, which can be deployed on the seafloor (Figure 3), in-line on a mooring chain or float, and/or on a surface buoy (Figure 4). Current measurements also can be collected from a vessel traversing the ocean. Other types of complementary measurements include meteorological parameters such as air temperature, humidity, and solar radiation, oceanographic parameters related to salinity, water temperature, and water quality (e.g., dissolved oxygen, nutrients, pH, etc.), and other marine environmental parameters such as acoustic recordings for identifying marine mammal activity.

Data transmission methods depend upon user requirements. Data may be archived internally by the instrument suite, or data may be telemetered in near real-time for proprietary or public viewing and use. Data telemetry technologies include direct cables, radio modems, and cell phone or satellite communications. Software packages also must be carefully applied to receive, buffer, quality control, display, network, and archive live streaming data. The first requirement for successful environmental monitoring in support of a marine renewable energy projects is a clear definition of measurement requirements and purposes. Measurement parameters required to locate an appropriate site can be different from those required to design a marine structure, which also differ from data required to assess potential environmental impacts or plan an efficient construction operation. They key is to clearly define data objectives, and properly design a system and analysis protocol to meet the requirements. Selection of mounting platforms and hardware, a specific instrument suite, measurement protocols (e.g., Number of measurements over a period of time, averaging scheme, etc.), and data quality standards are project-specific. Proper instrument deployment is required to ensure operation and recovery, and regular maintenance schedules are essential to maintain data flow and quality.

Woods Hole Group has collected measurements and performed environmental impact and engineering design criteria studies for offshore wind and hydrokinetic energy projects in the US and overseas (Figure 5). The company has a broad base of expertise to design, deploy, and recover data collection systems, utilize data for modeling and calculation of engineering design parameters, and develop environmental impact assessment reports to the satisfaction of local, state and federal regulatory agencies, including supporting NEPA documentation for BOEM and other agency review.

For more information about Woods Hole Group’s services in support of marine renewable energy projects, please contact Vice President and Coastal Engineer, Bob Hamilton at (508) 540-8080.


Submitted By:
Bob Hamilton
V.P. and Coastal Engineer

Contact Information:
Woods Hole Group – Falmouth
81 Technology Park Drive
East falmouth, MA 02536
P: 508-540-8080

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