Offshore wind: Comprehensive initial study is critical

Posted on November 17, 2009
Topic: Wind
Utilities have begun considering offshore wind as a source of new energy. Delmarva Power recently agreed to a long-term offshore wind power purchase contract, and organizations such as Long Island Power Authority and Public Service Enterprise Group are exploring the development and operation of offshore wind farms. The energy industry often focuses on the real-time data and operating challenges of wind, but it is also important to consider the upfront data and information challenges of planning wind resources -- particularly offshore wind.

Offshore vs. onshore

Wind energy has been harnessed on land for centuries. Moving the technology offshore brings advantages and challenges. The advantages are proximity to population centers, stronger winds that are in phase with peak demands, and the potential to develop larger farms. In addition, the capture and conveyance of offshore wind and onshore wind -- in terms of IT -- are similar.

However, transmission of the energy from a remote offshore facility presents challenges. It is expensive to convey energy to shore. About 20 percent of the project cost for the up to 1,000-MW London Array, the world's largest offshore wind farm, will go toward developing a grid connection.

One lesson learned during the initial offshore project in Europe is that insufficient initial study can lead to construction delays and increased project cost. A savings in terms of time and cost could have been achieved if the physical conditions underlying the site had been better understood earlier.

Site assessment

Wind turbine structure design, similar to the design of wave and current energy capture devices, requires information on the environment where the energy harnessing equipment will operate, as well as information specific to the particular energy source they seek to harness. Right from the feasibility stage of an offshore wind energy project, information on the region's seismicity, water depth, climatology, and a review of the existing wind, wave, current and tide level data for the site can provide early screening for suitable areas and structure types. Data regarding the region's geology and subsurface conditions will provide an indication of foundation and transmission line design requirements.

As the project takes shape, more detailed data will be required for designing the structures. Questions to be answered include:

  • What are the 100-year extreme values for wave heights or wind speeds?
  • What is the best time of year for installation?
  • What is the forecasted power output from the installation?
  • What foundation system will be used?
Cost-effective answers to these questions can be had through statistical analyses using a combination of carefully tailored measurement campaigns, site investigations and modeled data. Real-time data on parameters such as wave conditions, tidal height and weather conditions will help with the planning of the installations.

While it is often sufficient to use existing data sources and models for feasibility studies, it is usually essential to make at least a few months of site-specific measurements to fully validate wind, wave or current criteria used for engineering purposes.

In particular, measurements during the winter months are essential for validating statistics toward the extremes of likely conditions. Site assessment and other engineering aspects of designing and installing the necessary infrastructure were discussed at the Marine Technology Society for Offshore Wind Power Workshop held earlier this year.

What does offshore wind mean for utilities?

U.S. offshore wind development requirements will be defined by offshore wind experience in Europe and offshore oil and gas experience in the United States. Project success will require firms that have such experience.

With the American Recovery and Reinvestment Act of 2009, provisions of interest to wind energy -- such as the authorization of additional clean renewable energy bonds to finance facilities that generate electricity from renewable sources such as wind -- could mean that utilities attain their renewable energy portfolio goals more quickly.

Owning and building

Construction and finance would be the responsibility of developers looking to build the farms -- likely in federal or state waters. Firms with open-ocean experience should be retained during each phase of the project, from survey to investigation, through to design and fabrication.

Subscribe to Intelligent Utility magazine today.
Intelligent Utility magazine is the new, thought-leading publication on how to successfully deliver information-enabled energy. This article originally appeared in the May/June 2009 issue.

Authored By:
Mr. Pollard has 6 years of experience coordinating and executing geotechnical engineering investigations for a variety of projects in southern California, Virginia, and most recently the Middle East. He grew up near the windmills of San Gorgonio pass in southern California and looks forward to seeing them turning offshore the US. When not working, he enjoys the outdoors and tossing the Frisbee to his labradoodle.

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November, 17 2009

Harry Valentine says

Large bodies of water have less of a boudary layer effect on wind. Much data has already been collected in water parts of the world that attest to this. Unpopulated offshore islands can often be ideal locations for windfarms, as powerful winds will blow over such islands. There is the danger of public objection to windfarms on populated offshore islands, is the case with the Wolfe Island windfarm at the northeastern corner of Lake Ontario where powerful winds to blow. Some of the residents of Wolfe Island do object to wind turbines in their midst.

Quebec does have access to incredible offshore wind energy along the eastern sides of Hudson Bay and James Bay, with some 1600 uninhabited offshore islands. Quebec would have to negotiate with a neighbouring jurisdiction to place wind power technology on thise islands. There are many other parts of the world where powerful ocean winds blow over unihabited islands and where there is potential to install both tower-mounted wind turbines and airborne wind power technologies.

November, 24 2009

bill payne says

We continue to be suspicious of altenergy claims because of BTU IN vs BTU OUT concerns.

We suspect that the laws of thermodyunamics apply to wind and solar.

PNM stated on foil 6 that the laws of thermodynamics do not apply [N/A] to solar or wind electricity generation. Google 'pnm steve martin alternate report' to search for 'foil 6'.

Illinois Smart Energy Assistant Design Center posted

Wind 75 Btu per hour per square foot of wind turbine swept area in 22 mile per hour wind.

We emailed

From: To: "Donald Frederick Fournier" Cc: "Ben Joseph Sliwinski" Sent: Tuesday, November 24, 2009 8:40:46 AM GMT -07:00 US/Canada Mountain Subject: fast neutron on solar and wind electric output

Hello Don,

In view of the SEDAC published 200 BTU per hour per square foot for sunlight and 75 BTU ... for wind, what would SEDAC say about the accuracy of

fast neutron Santa Fe, NM January 12, 2009

From actual experience, wind farms produce 1.2 watts per square meter. Solar Thermal and Photovoltaic methods capture 5 to 6 watts per square meter. There is no economy of size in either technology. Dividing the watts you need by those values gives the land area in square meters needed to produce the juice. The numbers are astronomical

regards bill

in response to

----- Original Message ----- From: "Donald Frederick Fournier" To: Cc: "Ben Joseph Sliwinski" Sent: Monday, November 23, 2009 8:59:53 AM GMT -07:00 US/Canada Mountain Subject: RE: btu/pound of uranium

It gets a little complex, but on the issue of 900,000,000 vs 35,000,000,000. The larger number is just for U235. A typical power reactor is mostly U238. The U235 is about 2.5% of the original fuel load. This may explain the difference in the numbers. Also, all reactors breed a bit so some of the U238 is changed to plutonium (Pu239) and some of that fissions to provide a significant percentage of the energy from a typical power reactor.

Hope this helps.


Donald Fournier Chair, Building Research Council Program Manager, SEDAC University of Illinois at Urbana-Champaign (217) 265-0681 (800) 214-7954 WWW.SEDAC.ORG

November, 24 2009

bill payne says

Several minutes after I posted wind BTU information I received:

From: "Donald Frederick Fournier" To: Cc: "Ben Joseph Sliwinski" Sent: Tuesday, November 24, 2009 2:58:00 PM GMT -07:00 US/Canada Mountain Subject: RE: fast neutron on solar and wind electric output

Bill, the numbers I like to use are from Vaclav Smil in his 21st Century Energy article.

He says solar PV is 20 W per square meter of peak power. He says wind and water power are below 10 W/m2. Biomass is well below 1 W/m2.


Donald Fournier Chair, Building Research Council Program Manager, SEDAC University of Illinois at Urbana-Champaign (217) 265-0681 (800) 214-7954 WWW.SEDAC.ORG

I hope to resume my efforts to obtain solar electric output information from pnm.

Google 'PNM Algodones, NM Solar Array and Work Proposal'

November, 25 2009

Chavdar Azarov says

Power industry – Energy Equivalent Return

How much energy costs the provision of power industry*? How much energy it may provide the power industry?

* Estimation shall concern: - Lifetime of facilities - Conventional and alternative energy sources

November, 30 2009

Len Gould says

Bill: It is absolutely guaranteed that "at some point" wind and especially solar WILL outperform fossil and fission energy generation on all performance measurements. The only item of debate is how soon...

November, 30 2009

Don Hirschberg says

Len, a guaranty isn’t a guaranty unless there is recourse. Faith doesn’t count.

Almost 60 years ago an OCS classmate always got great laughter in the barracks when he gave his personal guaranty. The basis for the laughter was that an extraordinary claim calls for extraordinary proof or argument. (Candidate James Dooley was a used car salesman from Mankato, Mn, a great guy and a good soldier.)

It would be wonderful if your prediction were to come true. But your “at some time” gives you lots of wiggle room.

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