off shore wind technology trends and economics

Off-shore wind technology trends  and economics

In common with other clean, renewable, domestic sources of energy, off shore wind power can help to build a diversified and geographically distributed coastal countries energy mix offering security against many energy supplies whether natural or man-made. Wind power also emits no carbon dioxide (CO2) or other harmful emissions that contribute to climate change, ground level pollution or public health uses.

Off-shore wind energy resources can significantly increase the wind industry contribution to the coastal countries clean energy portfolio.

The U.S. ,Europe and Asian countries are fortunate to posses a large assessable off-shore wind energy resources. Wind speeds tend to increase significantly with distance from land, so off-shore wind resources can generate more electricity than wind resources at adjacent land based -sites.

Off-shore wind technology status

Although Europe now has a decade of experience with off-shore wind projects in shallow water, technology  essentially evolved from land based wind energy systems. Significant opportunities remain for tailoring the technology to better address key differences in the off shore environment. These opportunities are multiplied when deep water floating system technology is considered which is now in the early stages of development.

The opportunities for advancing off shore wind technologies are accompanied by significant challenges. Turbine blades can be much longer without land based transportation and construction constraints,  however  enabling technology is needed to allow construction of blade greater than 70 meters in length. The blades may also allowed to rotate faster off shore, as blades noise is less likely to disturb human habitations. Faster rotors operate at lower torque, which means lighter, less costly drive chain components. Challenges unique to the off shore environment include resistance to corrosive salt waters, resilience to tropical and extra tropical storms and waves, and  co existence with marine life and activities. Greater distances from shore create challenges from increased water depth, exposure to more extreme open ocean conditions, long distance transmission on high voltage submarine cables, turbine maintenance at sea and accommodation of  maintenance personnel.

A primary challenge for off shore wind energy is cost reduction. Developing the necessary support infrastructure implies one time costs for customized  vessels, ports and harbor upgrades, new manufacturing facilities and work force training. In general  capital costs are twice high as land based, but this may to be partially off set by potentially higher energy yields-as much as 30 percent or more. 

As experienced with land based wind systems over the past decades, off shore wind costs are expected to drop with greater experience, increased deployment and improved technology. To make off shore wind energy most cost effective, some manufacturers are designing larger wind turbines capable of generating more electricity per turbine. Several manufacturers are considering 10 MW turbine designs, and program  such as up wind in European union, are developing tools to allow these large machines to emerge.

In shallow water, the sub structure extends to sea floor , and includes monopoles, gravity basis and suction buckets. In transitional depth new technologies are being created or adopted from oil & gas industries, including jacket structures and multiple file  foundations which also extends sea floor. At same depth if no longer economically feasible to have rigid structure fixed to the sea floor, and floating  platform may be required. Three idealized concepts have risen for floating platform designs, including the semi submersible the spar buoy, and tension leg platform each which use different method for achieving static stability. Although it is not yet known which of these three designs will deliver the best system performance, designers seek plat form that are easy to install and minimize overall turbine loads. To determine the optimized design point advanced computer simulation models need to be developed and validated.


Economics off shore wind power

Off shore wind projects are analyzed in terms of initial  capital costs (ICC) as well as their life cycle costs, also known as the levelized cost of energy (LCOE)  . Cost profits of each type for U.S. market are difficult because of many regulatory and technical uncertainties and lack U.S. market experience . Although the European market is based a more developed supporting infrastructure and substantially different regulatory policy and physical environments, preliminary analysis of that experience provide some pluvial useful insight.

As in the case of land  based projects, the ICC for offshore wind power has been increasing over  time. Costs jumped approximately 55 percent between 2005 and 2007 leading to an estimated average capital investment of 4250 U.S. dollars per KW for an off shore wind project in 2010. The wind turbine it self contributes 44 percent of this total. In general capital costs are expected to increase with distance land and water depth and decreases as the size of project increases as result of economics of scale. As technology matures the prices expected to decline.

The LCOE calculations, or the cost of energy produced 20 year life of project, are based on average factors, many of which are currently unknown and must be projected. In addition ICC these include operations and maintenance(O&M) cost of the financing, amount of energy to be generated, long term system reliability and decommissioning costs.

O&M costs are higher for off shore wind turbines than land based turbines, primarily because of access issues. It is simply more difficult to perform work at sea. Although more research is needed to determine the range of these off shore O&M cost, some reports estimate they are two or three times higher than on land and can reach 20 percent to 30 percent of LCOE.

The LCOE for off shore wind is heavily influenced by the relatively high ICC and the cost of financing. A significant part of financing cost based on perception of financial risk and project uncertainties. These risk perceptions could potentially be lowered through research on virtually all of the factors that make up the LCOE for off shore wind, but larger impacts will come from confidence built on deployment experience.

Environmental socio economic risks

Risks associated with off shore wind energy are not as serious or potentially catastrophic compared with other energy technologies. Also wind turbines can be deployed relatively quickly to reduce green house gases, reduce other air emissions and help conserve water   resources. Potential risks in deploying off shore wind projects can typically be reduced through development and use of best management protection management principal. Although risks are site specific, research at European installed projects and U.S. base line studies are building knowledge base and helping to inform decision makers and public. 

Primary stake holder concern regarding off shore wind facilities include

Marine animal population : although European studies conducted to date suggest that the impact of off shore wind facilities on marine and animal populations are minimal.

Visual effects ;   coastal residents in view of an off shore wind farm may voice concern about visual impacts. More research is needed to better understand coastal communities and their ability to accept changes to the sea scrape.

Noise  : based on European studies and experience to date the most significant environmental impact stem from noise associated with pile driving during the construction phase. Mitigation strategies may be effective in reducing risk. Alternative technology can also implemented if appropriate to avoid some of pile driving activity.

Marine safety : the possibility of ship colliding with turbine poses a potentially significant risk to the marine environment from fuel leaks from disabled ship or human safety should turbine collapse. 

Finding and conclusions

Overall the opportunities for off shore wind are abundant, yet barriers and challenges are also significant. In the context greater energy, environmental and economic concern the nation faces, accelerating the deployment of off shore wind could have tremendous benefits for coastal based countries. Technological needs are generally focused on making off shore wind technology economically feasible and reliable and expanding the resource are to accommodate more regional diversity for future off shore projects. Prudent sitting strategies that involve stake holders at site would reduce potential risks. In short term reducing risk will stimulate economic growth accelerate permitting time frames and help address important aspect of  reducing global green house gases.