M – Offshore


This topic has been touched on in other pages, but warrants a focus that is provided here, largely because offshore wind is seriously being considered in a few jurisdictions. To provide much-needed context, Tables 1 to 3 show the recent past and current situation for offshore wind.

Table 1 – World-wide Implementations to 2007

Wind Plant Type



94,122 MW


1,165 MW

Per Cent Offshore/Total


Table 2 – Where Offshore Wind is Implemented


Cumulative Installed Capacity in Megawatts (MW)



United Kingdom


















World Total


Table 3 History of Offshore Wind Power Capacity 2000-2007


Cumulative Installed Capacity (MW)

Net Annual Addition (MW)

























The following comments can be made:

As to the future plans, there are a few politically-oriented initiatives for offshore wind plants.


In an article published on the Country Guardian website, “Wind Power in Denmark”, Dr. V. C. Mason provides the following insight about the future of wind power in Denmark.

”In 2007, the Administrative Director of DONG Energy (Denmark’s biggest player in the wind turbine market) commented that: ‘In the foreseeable future, wind power cannot solve the energy problem because it is too unstable and perhaps too expensive’. In the same year, Vattenfall’s Head of Information [Vattenfall controls approximately 25 per cent of the Danish power generation capacity] suggested that it is unrealistic to imagine that wind power can overtake other forms of energy within the next ten years. Recently, an energy policy spokesman for Venstre (one of Denmark’s bigger governing parties) has even suggested that the burning of wood chippings and straw is a far cheaper option than wind power for the production of renewable energy. The government aim of 30 percent renewables by 2025 may therefore rest with the provision of more biomass.”

What does this say about the realistic outlook for wind power, onshore and offshore, in Denmark?

United Kingdom

As are all member countries, Britain is legally committed by the EU to meet tough renewable energy targets by 2020 or face financial penalties. See the “Denmark” page for more information on the EU energy policies. This means that wind power, which presently contributes about 4 per cent of UK electricity, must expand substantially within 12 years. No country has tried to switch its electricity supply so quickly on this scale. To achieve this, it is reported that the industry will need to build nearly 15,000 turbines, generating 35 gigawatts (GW) roughly evenly split between onshore and offshore wind plants.

The Carbon Trust, a government agency, warned that the steep rise in the price of building offshore farms could undermine the whole project. It claims that “Currently the risk/return balance for offshore wind is not sufficiently attractive, and regulatory barriers would delay delivery well beyond 2020.”

Indications that UK offshore farms may not be profitable came in June 2008 when Shell pulled out of the consortium planning to build Britain’s biggest offshore farm, the London Array in the Thames Estuary, in favour of developing more profitable wind projects elsewhere. The government of Abu Dhabi stepped in to replace Shell.

Current experience with offshore wind plants in the UK is that capacity factors experienced are less than 30 per cent, a level which is often projected, but never achieved in extensive, mature onshore implementations.

There is considerable doubt from informed sources that the UK government is embarking on a sound strategy.


Germany has not yet followed Denmark’s lead in implementing offshore wind plants. Current plans include doubling wind plant capacity by 2020 to 48,000 MW, which will depend largely on offshore development. See the page “Germany, a Case Study” for a realistic assessment of such plans. Further, a spokesman for the German Wind Energy Association, Ulf Gerard, is quoted as saying, “Germany is the world leader in onshore wind technology but it’s still charting unknown waters with its offshore plans.”


The Ontario Power Authority (OPA) has received three studies from Hélimax Energy Inc. on the subject of wind power potential in Ontario. The first, dated November 2005, was in connection with the OPA Supply Mix Advice report and covered both onshore and offshore, the second dated March 2006 was part of the Integrated Power Supply Plan, and the third, dated April 2008, at the request of the provincial government, specifically addressed the offshore potential. The following are excerpts from the last two reports.

Hélimax March 2006 Report

“Only the onshore resource was considered in this report. Though Hélimax’s previous report to the OPA confirmed a significant offshore resource, particularly in Lake Erie and Lake Huron, it is generally thought that, due to additional challenges faced by offshore wind farms, this resource would only be exploited after the majority of the most viable onshore sites have been developed. One of the difficulties today for offshore development is the various environmental and social interests in the marine sites. Another issue is the greater amount of risk in developing, financing and operating wind farms.”

Hélimax April 2008 Report

“While the study does provide an overview of the development potential in the study area [offshore], it is important to note that a number of critical factors were not evaluated or were examined in only a preliminary (non site-specific) manner. Such factors include most notably seabed properties and icing conditions of the Great Lakes, as well as non-technical aspects such as visual impact, social acceptability and economic viability.”

As is the case with any report, these have to be read carefully and critically to extract their true significance.

Hélimax goes on to say

“While European projects provide an approximate indication of the scale of investment which might be expected for offshore development in the Great Lakes, certain adjustments will be required to account for market and environmental differences. In particular, the costs of offshore wind in Ontario will deviate from those in Europe due to differences in the transmission network, access to large port facilities, ice accumulation and movement on the Great Lakes, position on the learning curve, turbine supply, and offshore engineering experience.”

Extreme Spiking

The frequent, random variations, sometimes with large fluctuations over short periods of time, in wind plant output, are a major problem for the host electricity system. This is more accentuated with higher wind speeds, which occur in the months of highest production, or in an area of higher average wind speeds. This is particularly the case with offshore wind plants, which have stronger wind regimes than that found onshore. This is further described in the “Germany, a Case Study” page under Capacity Credit.

An emerging strategy to deal with this problem is curtailment (shutting down) of the wind output during periods of high production, which ironically negates the rationale used to justify offshore wind plant implementations in the first place. The following chart shows production from a Danish offshore wind plant with a total capacity of 160 MW that illustrates this. This extreme spiking is not a unique occurrence.

Figure 1 – Representative Wind Fluctuation for a Danish Offshore Wind Plant

(5 minute intervals for 48 hours versus % of wind plant capacity)


Source: Incoteco (Denmark) ApS

The production of a “carpet” of such wind plants has been described as like that of a single, virtual “out of control” power station.


Apart from the extreme spiking issue described above, there are other problems. This section provides more general information on other experience to date.

· In August 2007, Business Week/Spiegel Online in “The Dangers of Windpower” reports that Germany plans offshore wind farms to produce a total of 25,000 megawatts by 2030. It is suggested that perhaps by then, the lessons learned on land will ward off disaster at sea.

· The Danish company, and world market leader Vestas, had to remove the turbines from an entire wind plant along Denmark’s western coast in 2004 because the turbines were not sufficiently resilient to withstand the local sea and weather conditions. Similar problems were encountered off the British coast in 2005.

· The German wind turbine giant Enercon, considers the risks associated with offshore wind power generation too great, according to a spokesman, Andreas Düser.

· As mentioned above, Shell pulled out of the consortium planning to build Britain’s biggest offshore farm, the London Array in the Thames Estuary, in favour of developing more profitable wind projects elsewhere.


According to Hélimax and the UK Royal Academy of Engineering, the capital costs for offshore are about twice that for onshore. There is a greater range for operations and maintenance costs, which are reported to be from two to three times, as expensive. Shadowing backup costs will be approximately the same.


The general issue that stronger wind regimes are more problematic, because of more severe wind output fluctuations, works substantially against the viability of offshore wind plants in particular. In addition to this, the considerably higher cost and operations and maintenance problems put into serious question any arguments for offshore expansion.

The claim that an abundance of wind automatically means that we must have wind plants is the same logic as saying that an availability of coal means that we should have more coal generation plants. There are other larger issues involved.

There is a reason for the relatively low progress in the development of offshore wind world-wide. Any country, state or province seriously considering such wind plants would be well advised to proceed with caution, if at all.

Last updated November 27, 2008

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