Should low carbon energy technologies be envisaged in the context of sustainable energy systems?

Grigorios L. Kyriakopoulos , in Low Carbon Energy Technologies in Sustainable Energy Systems, 2021

3.1.4 Offshore wind farms using GIS-based multi-criteria decision analysis and analytical hierarchy process

Offshore wind farms globally dispose today a total cumulative capacity representing 4.5% of total cumulative capacity and only 0.3% of global electricity generation. However, the wind technology sustains the potential to become a certainly supportive RES technology to meet the global power supply. A 15-times increase of today capacity of offshore energy production is forecasting within the next two decades, making it a protagonistic RES technology to the electrification of Europe. From a social viewpoint offshore wind has the advantages to prevent either social conflicts from competitive land uses, or social unrest issues, which other RES technologies are confronting. From an environmental viewpoint the wind farm technology is prone to future development within the next two decades, reaching at 5–7 Gtonnes of carbon dioxide emissions prevention from the power sector worldwide [19]. It is noteworthy that offshore wind farms can certainly play a decisive role to meet a future scaling-up of installed infrastructure for renewables-based era of the future. In this respect, proper regulatory framework should consider the site selection and, consequently, and the rules of operation for these wind energy-driven projects [19].

At the study of Gkeka-Serpetsidaki and Tsoutsos [19] the authors provided a fundamental basis on which the most sustainable scenarios, concerning the installation of offshore wind farms (OWFs) should be adapted. The selected methodology and evaluation was based on the surrounding marine areas of the island of Crete (Greece), being shown as the most sustainable scenarios' running regarding the installation of OWFs [19]. Different types and evaluation criteria, such as environmental, techno-economical and socio-political, they were jointly addressed while the methodology included questionnaires. These questionnaires were fully consisted of pairwise comparisons among the aforementioned criteria, being gathered from eight different groups of stakeholders/experts and then the relative importance of the selected criteria was measured with the aim of the Analytical Hierarchy Process (AHP). The proposed analysis utilized Geographic Information Systems (GIS) to deploy a site spatial assessment of the area studied. Additionally, the relative weights had been derived from the responses given by different stakeholders who participated in the survey [19].

Such a developed methodology can be adopted by all stakeholders and competent authorities, as a decision-making tool, since municipal authorities are responsible for the legislative planning of OWFs at a regional level of analysis [19]. Among others, specific consideration can be taken to the protection of areas of environmental interest and the accommodated sensitive ecosystems, fostering the sustainable development of the offshore wind farms' installed. Such an installation of wind farms it is anticipated to offer incomparable benefits for island contexts, including: unlimited usage of wind-RES, usage reduction of fossil fuels, energy supply security, reduction of electricity cost, environmental conditions' improvement for wildlife and natural ecosystems, autonomous electricity at high demanding periods, especially at tourism seasons, and summer times, savings of energy and resources, supportiveness to achieve national and/or European energy goals' related to climate crisis, as well as employment opportunities for the local citizens [19].

On the other hand, the sustainable prospects of wind-farms siting imply certain complexities and contradictions among numerous factors, including regulatory and techno-economic constraints. Therefore, the suitable site selection of OWF by energy policy makers should co-evaluate various environmental and socio-political criteria, toward minimization of the OWF impacts and maximization of the techno-economic benefits [19]. The reliability and verification of the adopted method are mainly based on the criteria selected, while planning considerations refer also to the successful integration/synthesis of different perceptions and judgments among all experts involved. These characteristics are proving that the followed methodology should be considered as a dynamic decision-making tool, where all stakeholders are responsible for the regulatory preparedness and the legislative planning of OWFs at a regional, and wider national, level of analysis [19].

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Wind Energy

Georgios Nikitas , ... Nathan Vimalan , in Future Energy (Third Edition), 2020

16.3.3 Offshore wind farm

As offshore wind farm can be defined as a power plant that contains all the facilities needed to capture the wind power, transform it into electricity and supply it to the main electricity network. An actual offshore wind farm is shown in Fig. 16.11, which provides an aerial view of the Dudgeon wind farm, located in the United Kingdom.

Figure 16.11. Drone view of the Dudgeon wind farm.

 Photo courtesy: Jan Arne Wold; Equinor.

The main parts of an offshore wind farm are the wind turbines, the cables, and the substations [13]. The turbines are the most important part. Wind turbines are nothing more than generators that convert the wind power into electric power. For economic reasons, such as reducing planning, construction, and maintenance costs, many wind turbines are installed at the same time in one location. The electric power produced by the turbines is then transferred through cable arrangements to an offshore substation. There the voltage of the electric power is stabilized and maximized and then exported to shore. Through an onshore substation, the offshore electric power is added to the main electricity grid. Fig. 16.12 schematically presents a typical layout of an offshore wind farm, with all of its key components annotated. For further details on offshore wind farms and wind turbines, the readers are referred to Chapter 1 of Bhattacharya, 2019 [14].

Figure 16.12. Layout of a typical offshore wind farm.

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Wind Energy

M. Kapsali , J.K. Kaldellis , in Comprehensive Renewable Energy, 2012

2.14.6.1 Noise Impacts

Offshore wind farms are located far away from human populations. Therefore, it is most likely that people are not affected by the noise generated by the offshore wind turbines. However, marine animals could be affected by the underwater noise generated during the construction of the wind farm and operation of the wind turbines. For example, during the installation of the foundations, the perceived noise can have lethal effects or cause permanent damage to their hearing and thus disturb sea life. Any effects of the noise, however, will depend on the acoustic sensitivity of the species and their ability to adjust to it.

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Offshore wind energy

Martin Junginger , ... Michael Taylor , in Technological Learning in the Transition to a Low-Carbon Energy System, 2020

Abstract

Offshore wind farms have been deployed since 1991, mainly in the North sea and Baltic sea but in recent years also in the United States and East Asia. Learning effects in offshore wind parks have been masked by various other developments over the past two decades, leading first to an increase in capital expenditures (Capex) and average levelized cost of electricity (LCOE) between 2003 and 2012, followed by a steep decline between 2015 and 2018. Based on changes in Capex, capacity factor, weighted average cost of capital (WACC), and operational expenditures (Opex), the LCOE increased from 120€/MWh in 2000 to 190€/MWh in 2015 and then decreased to about 100€/MWh at the end of 2018, with average projections for 2021 reaching 70€/MWh. Especially the increase in capacity factor has been a major driver in reducing the LCOE. Given the strong fluctuations in the past and many factors influencing the LCOE of offshore wind projects, it was not possible to derive meaningful one-factor experience curves and learning rates that would allow extrapolation for the future cost projections. Multifactor learning curves approach taking into account raw material costs, location-specific properties, and soft factors such as developments in WACC show more promise, but more deployment of offshore wind is needed to demonstrate whether such models can provide more accurate cost trend forecasts for the coming years.

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Integration of power from offshore wind turbines into onshore grids

O.D. Adeuyi , J. Liang , in Offshore Wind Farms, 2016

14.6 Conclusions

The installed capacity of offshore wind farms in Europe is expected to increase from 8  GW in 2014 to about 23.5   GW in 2020. This chapter described the key technologies required for wind power collection and grid connection of offshore wind farms to onshore grids. Offshore wind farms will use both HVAC and VSC-HVDC submarine power transmission technologies to transfer the electricity generated from offshore wind farms to onshore grids. There is a need to further develop low-frequency AC transmission systems, DC circuit breakers for DC grids and the scheme comprising diode rectifiers and VSC inverters for grid connection of offshore wind farms.

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What Is an Offshore Wind Farm?

Kurt E. Thomsen , in Offshore Wind, 2012

Publisher Summary

Offshore wind farms are made up of a number of wind turbines. The wind farm is situated in an area with relatively shallow water that is not too far from the coastline and where the mean wind speed is favorable. A wind turbine consists of three main components: the tower, a nacelle or the generator house, and the rotor. The rotor consists of three blades connected to a central hub on the nacelle. The four most commonly used offshore wind turbine foundations include monopile, gravity base, tripod, and jacket. A monopile is a steel tube of a large diameter that is driven into the seabed by using a large hydraulic hammer. A gravity-based foundation is a very heavy displacement structure usually made of concrete, which applies vertical pressure to the area below, and stands on the seabed. The size and weight of the foundations make their transport and installation cumbersome, and the seabed has to be prepared by dredging and backfilling material in order to install the foundation. A tripod is a steel tube that protrudes out of the ocean surface where an anchor pile is driven into the seabed to hold the foundation in place. It provides enormous stability against bending moments and has the ability to resist very strong vertical forces as well as bending moments induced by the turbine and the waves. A jacket foundation is a lattice-type steel structure, usually square in footprint and constructed of thin tubes, which is exclusively used for large water depths.

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Environmental and Other Issues

Kurt E. Thomsen , in Offshore Wind (Second Edition), 2014

Pollution Issues

Offshore wind farm installation environmental issues are, however, more than just waste management. We wish to establish the offshore wind industry as one where we discharge nothing harmful into the surrounding environment. This goes for all aspects of the work carried out. We make sure that oil spills are not happening, and we take the MARPOL convention very seriously. We make sure that all components are fabricated in the most effective and environmentally friendly way. But there is one area where this is not the case. When we construct the installation vessels, we tend to seek out the least expensive supplier possible, sometimes sacrificing environmental standards.

It should be clear that nothing is wrong with the work carried out in Third World countries; the workmanship is fine and adequate to the point at which we can be satisfied. But in some cases, the HSE (health and safety or environmental) standards applied are not exemplary. The issue is, of course, that when we solve the environmental problem at home by means of installing offshore—and onshore wind—in a safe, efficient, and environmentally friendly manner, we participate in an ongoing environmental disaster in the yards in Asia. Note in Fig. 18.2 the lack of any kind of pollution barrier on the ground. Also notice the very unsafe access ways—provided these can even be called access ways. This is where the standards for HS and certainly E are much lower, if they exist at all. This cannot be right.

Figure 18.2. Jack-up barge construction in Asia.

Of what use are health and safety regulations at home if people elsewhere risk their lives to build the jack-ups (see Fig. 18.3 ) we use for the installation of offshore wind farms? This, of course, saves money, but we should not allow these cost-cutting procedures. If we want to hold the HSE banner high, we should do so all the way through the process. We cannot solve our problems by contributing to the same problems where we buy products and services.

Figure 18.3. This rigging of the A-frame crane for the European fleet of jack-up barges demonstrates that people are working without any regard for safety.

This can affect quality as well. The result of rigging the exorbitantly expensive rope in dirt and rain water is a substandard product. The risk of quickly damaging rope, drum, and sheaves is extremely high. Dragging the rope over a wet dirty concrete yard will cause rust to collect in the strings immediately, and the rope on which the life of the crane operator and surrounding personnel depends will no longer function correctly (see Fig. 18.4).

Figure 18.4. Although this is an inexpensive way to rig the crane, it contradicts everything the author has learned in more than 27 years of crane rigging and operation.

As an industry, it is vitally important that we apply the same rules and regulations throughout the entire supply chain. Otherwise, we become exactly what we accuse less respected markets and suppliers of being. For example, are they wrecking the vessel in Fig. 18.5 or building it? The photo of course begs the question of whether the wind farm developer has done any subcontractor evaluation in the yard. Probably not. If this yard had been evaluated by a reputable developer, the contract would never have been signed.

Figure 18.5. This shows the construction of a jack-up for the European wind industry.

As the preceding figures show, the supply chain stops at home—for the moment. We would not be able to turn the clock back to the days when our construction sites looked like this, and therefore, the only way to prevent competing against manufacturers who have low HSE standards is to turn their clock forward and require the same obligations of them. This is not unreasonable. At some point, pollution, lack of respect for the environment, and lack of concern for health and safety will come back to haunt us as will the inability to deliver a cleaner, safer place.

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Remote sensing technologies for measuring offshore wind

M.S. Courtney , C.B. Hasager , in Offshore Wind Farms, 2016

4.1 Introduction

4.1.1 The need for data

Offshore wind farm development is to high degree dependent upon reliable information on wind conditions. The revenue of a wind farm is proportional to the annual energy production (AEP). All other issues around a wind farm reduce the revenue, such as capital expenses (CAPEX), operational expenses (OPEX), installation cost, feasibility and decommissioning. The AEP is proportional to the square of the wind speed. Thus, even relatively small uncertainty on the wind speed increases considerably the uncertainty on the AEP. Wind farm development offshore typically is planned at a large scale with hundreds of MW to GW installed capacity in one wind farm, or clusters of large wind farms. The wind resource at a site is key information for wind farm planning. Also, the wind variability at a daily, seasonal and interannual timescale and extreme winds such the 50-year return values of 10-min values and 3-s gusts are important. At shorter timescales, wind variability from seconds to minutes for control and operation of the wind turbines and wind farm operation (ie, clusters operation) for the balancing of power, needs to be assessed.

Ideally, winds near wind turbine hub-height observed over several years and resolved at 10-min resolution are ideal for wind resource estimation. Unfortunately, the cost of meteorological wind observations offshore is very high and therefore there is scarcity of data. In addition, the measurements performed by private companies are not shared publically as the competitive benefit of detailed knowledge on offshore atmospheric conditions is valuable for further wind farm development. The key parameters of relevance include 10-min wind speed and direction; wind resource; extreme winds 10-min and 3-s gusts maximum values during 50   years (ie, the design wind speed); daily, seasonal and interannual variability; and the 'quality of the wind', ie, the short-term variability and its predictability. Finally, the atmospheric turbulence is part of design criteria and also needs to be considered for selection of the wind turbine for a given wind climate. Wind turbine wake effects are of utmost importance when deciding on the layout of a wind farm. The added turbulence from operating wind turbines increases the load on wind turbines located further downstream, thus not only is it necessary to consider the potential wake loss, ie, the reduced AEP due to wind turbine wake effects, but also to evaluate the potential load and additional cost if turbines need more service and repair when located in conditions of higher turbulence.

Atmospheric modelling of offshore wind conditions is advanced. Mesoscale modelling provides the state of the art in offshore wind resource mapping but all model results need verification to be trusted because there is an immense selection of choices in the modelling regarding input data, planetary boundary-layer schemes, among other issues (Hahmann et al., 2014). As mentioned above, the cost of measuring is high, yet the cost of not measuring will result in high uncertainty on AEP, which will typically increase the cost of financial capital and also limit the possibility of optimal planning of, for example, layout.

4.1.2 The offshore reality

When the world's first offshore wind farm at Vindeby in Denmark was taken into operation, many said that 'it isn't really offshore'! At the time, to us doing the measurements there, it felt rather offshore, but in retrospect and after visits to modern wind farms such as Horns Rev I and II, there is both offshore and really offshore! Our point here is that from both wind modelling and measurement perspective, there is a range of offshore site types that we need to address.

Many wind turbines have been built on or very close to docks and harbours, often with a fetch that is predominantly open water. Resource measurements will clearly have been performed from dry land. Whilst it is usually possible to enter the turbine 'with dry feet', reference wind measurements (eg, for the power performance verification) will need to measure the wind speed some hundreds of metres out in the water. Already this requires 'offshore' methods and equipment.

Vindeby was actually between 1.5 and 3   km from the Lolland, Denmark coast, and with water depths between 2 and 6   m. Even at these modest distances, the wind resource is significantly different to the adjacent coast wind resource and, due to the quite strong land–sea gradients, quite difficult to model accurately. Wind turbine measurements required a local reference which was provided by two free-standing (ie, non-guyed) met masts mounted on monopoles driven into the sea bed. We were soon aware that the mast erection and operation represented an order of magnitude increase in both cost and logistical difficulties compared to onshore operations. In particular, we experienced (ie, at Vindeby and other early offshore masts) severe problems with mast access, salt-induced corrosion, failing autonomous power supplies and seabird fouling. Whilst much more professional solutions to all these issues are now common practice, all remain as serious challenges to robust offshore measurements.

Modern offshore wind farms are orders of magnitude larger than Vindeby, often 20–30  km from the coast and in water depths up to 20–40   m. Here conventional (ie, mast-mounted) measuring methods are at their limit since mast costs are very high (ie, in millions of Euro).

Remote sensing of wind speed comes in two very different forms – surface (ie, buoy or wind turbine)-based measurements utilising the backscatter from wind-borne aerosols and space-borne (ie, satellite) measurements utilising the backscatter from capillary waves. We will present the theoretical basis for each type in Sections 4.3 and 4.4, respectively. To set this in perspective, however, we will start out with a brief introduction to conventional measurement techniques in Section 4.2.

At all offshore sites, surface-based remote sensing methods can play a major role in reducing the uncertainty of wind resource estimates as well as providing a traceable reference wind speed measurement for power performance verification once the wind farm is operational. At distances of a few kilometres from the coast, space-borne remote sensing can be used for resource estimation although with somewhat higher uncertainty than surface-based methods. As a case study in Section 4.5, we will describe how the development, construction and verification of a hypothetical, so-called 'near-coastal' wind farm (ie, 8–12   km from the coast) can be aided by both remote sensing technologies. At this distance from the coast, all conceivable techniques can actually be used. The chapter will close with some ideas about future trends within the field of offshore resource assessment and some useful sources of additional information.

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Assembly, transportation, installation and commissioning of offshore wind farms

M. Asgarpour , in Offshore Wind Farms, 2016

17.1 Introduction

Installation of offshore wind farms is the last step before commissioning of an offshore wind farm, which contributes to approximately 20–30% of development costs or 15–20% of the price of energy. It is projected that the trend of offshore wind installation will grow rapidly in coming years. In Europe alone, by the end of 2014, about 2500 offshore wind turbines were installed, making a cumulative total capacity of 8  GW in 74 offshore wind farms (Corbetta and Mbistrova, 2015). Moreover, there are governmental plans to install another 32   GW of offshore wind energy in Europe by 2020 (European Commission, 2013). This means that the required effort for future distant and large offshore wind farms will be enormous in coming years.

During the development of an offshore wind farm the installation step is typically overlooked, resulting in project delays and noticeable risks and financial consequences. Therefore, it is essential to have a better look into the installation steps and optimise them when possible to reduce the installation costs, risks and delays.

Before the actual offshore installation takes place, the components should be designed and manufactured, be delivered to the onshore assembly site at the harbour, be assembled based on the installation strategy, and then, be transported to the location of the offshore wind farm. The design of the turbine components, such as the tower, the nacelle and blades, is done by the wind turbine manufacturer. In the following sections of this chapter, these steps are briefly described for a typical three-bladed horizontal axis wind turbine.

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Growth Trends and the Future of Wind Energy

Lauha Fried , ... Steve Sawyer , in Wind Energy Engineering, 2017

26.2.5 France Gearing up to Deliver

Six offshore wind farms totaling 3  GW are currently under construction. The Round 1 projects include: Courseulles (500   MW), Fécamp (500   MW), Saint-Nazaire (500   MW), Saint-Brieuc (500   MW); and the Round 2 projects include: Dieppe-Le Tréport (500   MW) and Iles d'Yeu et de Noirmoutier (500   MW). The industry expects the third tender for offshore wind power to be launched by the end of 2016.

The key challenges faced by the sector are the need for cost reductions; integration of offshore farms within the maritime areas; and increased competition in the market. A public debate focusing on offshore wind power development in France is planned during the summer of 2016. The French wind industry has set ambitious goals to reach 12   GW of bottom-fixed and 6   GW of floating offshore wind capacity by 2030.

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