GHG emissions and energy performance of offshore wind power

This paper presents specific life cycle GHG emissions from wind power generation from six different 5 MW offshore wind turbine conceptual designs. In addition, the energy performance, expressed by the energy indicators Energy Payback Ratio (EPR) Energy Payback Time (EPT), is calculated for each of the concepts.There are currently few LCA studies in existence which analyse offshore wind turbines with rated power as great as 5 MW. The results, therefore, give valuable additional environmental information concerning large offshore wind power. The resulting GHG emissions vary between 18 and 31.4 g CO₂-equivalents per kWh while the energy performance, assessed as EPR and EPT, varies between 7.5 and 12.9, and 1.6 and 2.7 years, respectively. The relatively large ranges in GHG emissions and energy performance are chiefly the result of the differing steel masses required for the analysed platforms. One major conclusion from this study is that specific platform/foundation steel masses are important for the overall GHG emissions relating to offshore wind power. Other parameters of importance when comparing the environmental performance of offshore wind concepts are the lifetime of the turbines, wind conditions, distance to shore, and installation and decommissioning activities.Even though the GHG emissions from wind power vary to a relatively large degree, wind power can fully compete with other low GHG emission electricity technologies, such as nuclear, photovoltaic and hydro power.     

A macro-level decision analysis of wind power as a solution for sustainable energy in the USA

This study aims to quantify the socio-economic and environmental impacts of producing electricity by wind power plants for the US electricity mix. To accomplish this goal, all direct and supply chain-related impacts of different onshore and offshore wind turbines are quantified using a hybrid economic input-output-based triple bottom line (TBL) life cycle assessment model. Furthermore, considering TBL sustainability implications of each onshore and offshore wind energy technology, a multi-criteria decision-making tool which is coupled with Monte Carlo simulation is utilised to find the optimal choice of onshore and offshore wind energy. The analysis results indicate that V90-3.0 MW wind turbines have lower impacts than V80-3.0 MW for both socio-economic and environmental indicators. The Monte Carlo simulation results reveal that when environmental issues are more important than socio-economic impacts, V90-3.0 MW offshore is selected among the alternatives.     

Greenhouse gas emissions from electricity generated by offshore wind farms

For wind power generation offshore sites offer significantly better wind conditions compared to onshore. At the same time, the demand for raw materials and therefore the related environmental impacts increase due to technically more demanding wind energy converters and additional components (e.g. substructure) for the balance of plant. Additionally, due to environmental concerns offshore wind farms will be sited farshore (i.e. in deep water) in the future having a significant impact on the operation and maintenance efforts (O&M). Against this background the goal of this analysis is an assessment of the specific GHG (greenhouse gas) emissions as a function of the site conditions, the wind mill technology and the O&M necessities. Therefore, a representative offshore wind farm is defined and subjected to a detailed LCA (life cycle assessment). Based on parameter variations and modifications within the technical and logistical system, promising configurations regarding GHG emissions are determined for different site conditions. Results show, that all parameters related to the energy yield have a distinctive impact on the specific GHG emissions, whereas the distance to shore and the water depth affect the results marginally. By utilizing the given improvement potentials GHG emissions of electricity from offshore wind farms are comparable to those achieved onshore.     

Life cycle assessment of the offshore wind farm alpha ventus

Due to better wind conditions at sea, offshore wind farms have the advantage of higher electricity production compared to onshore and inland wind farms. In contrast, a greater material input, leading to increased energy consumptions and emissions during the production phase, is required to build offshore wind farms. These contrary effects are investigated for the first German offshore wind farm alpha ventus in the North Sea. In a life cycle assessment its environmental influence is compared to that of Germany’s electricity mix.In comparison to the mix, alpha ventus had better indicators in nearly every investigated impact category. One kilowatt-hour electricity, generated by the wind farm, was burdened with 0.137 kWh Primary Energy-Equivalent and 32 g CO₂-Equivalent, which represented only a small proportion of the accordant values for the mix. Furthermore, the offshore foundations as well as the submarine cable were the main energy intensive components. The energetic and greenhouse gas payback period was less than one year.Therefore, offshore wind power, even in deep water, is compatible with the switch to sustainable electricity production relying on renewable energies. Additional research, taking backup power plants as well as increasingly required energy storage systems into account, will allow further calculation.     

Characterization of the unsteady aerodynamics of offshore floating wind turbines

Large‐scale offshore floating wind turbines were first proposed in 1972 by Prof. William E. Heronemus at the University of Massachusetts. Since then, very little progress has been made in the deployment of these systems despite the significant advantages afforded by floating wind turbines, namely access to superior wind resources and increased placement flexibility. Aside from the large capital costs associated with construction, one of the most significant challenges facing offshore floating wind turbines is a limited simulation and load estimation capability. Many wind turbine aerodynamic analysis methods rely on assumptions that may not be applicable to the highly dynamic environment in which floating wind turbines are expected to operate. This study characterizes the unique operating conditions that make aerodynamic analysis of offshore floating wind turbines a challenge. Conditions that may result in unsteady flow are identified, and a method to identify aerodynamically relevant platform modes is presented. Operating conditions that may result in a breakdown of the momentum balance equations are also identified for different platform configurations. It is shown that offshore floating wind turbines are subjected to significant aerodynamic unsteadiness fixed‐bottom offshore turbines. Aerodynamic analysis of offshore floating wind turbines may require the use of higher‐fidelity ‘engineering‐level’ models than commonly in use today. Copyright © 2012 John Wiley & Sons, Ltd.     

Assessing the life cycle environmental impacts of wind power: A review of present knowledge and research needs

We critically review present knowledge of the life cycle environmental impacts of wind power. We find that the current body of life cycle assessments (LCA) of wind power provides a fairly good overall understanding of fossil energy use and associated pollution; our survey of results that appear in existing literature give mean values (± standard deviation) of, e.g., 0.060 (±0.058) kW h energy used and 19 (±13) g CO₂e emitted per kW h electricity, suggesting good environmental performance vis-à-vis fossil-based power. Total emissions of onshore and offshore wind farms are comparable. The bulk of emissions generally occur in the production of components; onshore, the wind turbine dominates, while offshore, the substructure becomes relatively more important. Strong positive effects of scale are present in the lower end of the turbine size spectrum, but there is no clear evidence for such effects for MW-sized units. We identify weaknesses and gaps in knowledge that future research may address. This includes poorly understood impacts in categories of toxicity and resource depletion, lack of empirical basis for assumptions about replacement of parts, and apparent lack of detailed considerations of offshore operations for wind farms in ocean waters. We argue that applications of the avoided burden method to model recycling benefits generally lack transparency and may be inconsistent. Assumed capacity factor values are generally higher than current mean realized values. Finally, we discuss the need for LCA research to move beyond unit-based assessments in order to address temporal aspects and the scale of impacts.     

Evaluating the environmental impacts of recycling wind turbines

Wind power is one of the fastest growing renewable energy sources. The wind turbines have an expected design lifetime in the range of 20 to 25 years after which decommissioning is expected. The trend in the wind turbine industry is that the turbines increase in size—especially when considering offshore wind turbines in the 7 to 8 MW size range. Life cycle assessments show that the materials used for manufacturing the turbines accounts for 70 to 80% of the environmental impact, so ensuring optimal recycling at the end‐of‐service‐life is of economic and environmental interest and in line with the principles of transitioning towards a circular economy. The decommissioning and recycling process is analysed in this paper, with special considerations given to the environmental aspects of a theoretical 100% recyclability scenario. This includes cradle‐to‐gate life‐cycle inventory analysis of the materials, embedded energy, and CO₂‐equivalent emissions. The findings show that established recycling methods are present for most of the materials and that recycling of a 60 MW wind park at end‐of‐service‐life provides environmental benefits as well as lowering the natural resource use and securing resources for use in the future. The saved energy is estimated to approximately 81 TJ. The reduction in emissions related to the recycling of wind turbine material totals approximately 7351 ton CO₂.     

Wind power planning: assessing long-term costs and benefits

In the following paper, a new and straightforward technique for estimating the social benefit of large-scale wind power production is presented. The social benefit is based upon wind power's energy and capacity services and the avoidance of environmental damages. The approach uses probabilistic load duration curves to account for the stochastic interaction between wind power availability, electricity demand, and conventional generator dispatch. The model is applied to potential offshore wind power development to the south of Long Island, NY. If natural gas combined cycle and integrated gasifier combined cycle (IGCC) are the alternative generation sources, wind power exhibits a negative social benefit due to its high capacity cost and the relatively low emissions of these advanced fossil-fuel technologies. Environmental benefits increase significantly if charges for CO₂ emissions are included. Results also reveal a diminishing social benefit as wind power penetration increases. The dependence of wind power benefits on CO₂ charges, and capital costs for wind turbines and IGCC plant is also discussed. The methodology is intended for use by energy planners in assessing the social benefit of future investments in wind power.     

Life cycle assessment of a wind farm and related externalities

This paper concentrates on the assessment of energy and emissions related to the production and manufacture of materials for an offshore wind farm as well as a wind farm on land based on a life cycle analysis (LCA) model. In Denmark a model has been developed for life cycle assessments of different materials. The model is able to assess the energy use related to the production, transportation and manufacture of 1 kg of material. The energy use is divided into fuels used in order to estimate the emissions through the life cycle. In the paper the model and the attached assumptions are described, and the model is demonstrated for two wind farms. The externalities for the wind farms are reported, showing the importance of life cycle assessment for renewable energy technologies.     

Levelised cost of energy for offshore floating wind turbines in a life cycle perspective

This report presents a comprehensive analysis and comparison of the levelised cost of energy (LCOE) for the following offshore floating wind turbine concepts: Spar-Buoy (Hywind II), Tension-Leg-Spar (SWAY), Semi-Submersible (WindFloat), Tension-Leg-Wind-Turbine (TLWT) and Tension-Leg-Buoy (TLB). The analysis features a generic commercial wind farm consisting of 100 five megawatt turbines, at a far offshore site in a Life Cycle Analysis (LCA) perspective. Data for existing bottom-fixed turbines, both jacket and monopile concepts are used as reference values for adaptation to the generic wind farm parameters. The results indicate that LCOE values are strongly dependent on depth and distance from shore, due to mooring costs and export cable length, respectively. Based on the findings, depth is the dominant parameter to determine the optimal concept for a site. Distance to shore, Load Factor and availability are amongst the significant factors affecting the LCOE. The findings also indicate that LCOE of floating turbines applied in large scale and in intermediate depths of 50–150 m is comparable to bottom-fixed turbines. Floating turbines for increasing depths generally experience increased LCOE at a lower rate than bottom-fixed turbines. An optimal site, situated 100 km offshore would give LCOE in the range of € 82.0–€ 236.7 per megawatt-hour for the conceptual designs in this paper.     

Design and model confirmation of the intermediate scale VolturnUS floating wind turbine subjected to its extreme design conditions offshore Maine

Floating offshore wind turbines are gaining considerable interest in the renewable energy sector. Design standards for floating offshore wind turbines such as the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbine Installations are relatively new and few if any floating wind turbines have yet experienced the prescribed design extreme environmental conditions. Only a few pilot floating turbines have been deployed in Europe and Japan. These turbines have been designed for long return period storm events and are not likely to see their extreme design conditions during early deployment periods because of the low probability of occurrence. This paper presents data collected for an intermediate scale floating semi‐submersible turbine intentionally placed offshore Maine in a carefully selected site that subjects the prototype to scale extreme conditions on a frequent basis. This prototype, called VolturnUS 1:8, was the first grid‐connected offshore wind turbine in the Americas, and is a 1:8 scale model of a 6 MW prototype. The test site produces with a high probability 1:8 scale wave environments, and a commercial turbine has been selected so that the wind environment/rotor combination produces 1:8‐scale aerodynamic loads appropriate for the site wave environment. In the winter of 2013–2014, this prototype has seen the equivalent of 50 year to 500 year return period storms exercising it to the limits prescribed by design standards, offering a unique look at the behavior of a floating turbine subjected to extreme design conditions. Performance data are provided and compared to full‐scale predicted values from numerical models. There are two objectives in presenting this data and associated analysis: (i) validate numerical aeroelastic hydrodynamic coupled models and (ii) investigate the performance of a near full‐scale floating wind turbine in a real offshore environment that closely matches the prescribed design conditions from the ABS Guide. Copyright © 2015 John Wiley & Sons, Ltd.     

Life-cycle assessment in the renewable energy sector

The Polish energy industry is facing challenges regarding energetic safety, competitiveness, improvement of domestic companies and environmental protection. Ecological guidelines concern the elimination of detrimental solutions, and effective energy management, which will form the basis for sustainable development. The Polish power industry is required to systematically increase the share of energy taken from renewable sources in the total energy sold to customers. Besides the economic issues, particular importance is assigned to environmental factors associated with the choice of energy source. That is where life-cycle assessment (LCA) is important. The main purpose of LCA is to identify the environmental impacts of goods and services during the whole life cycle of the product or service. Therefore LCA can be applied to assess the impact on the environment of electricity generation and will allow producers to make better decisions pertaining to environmental protection. The renewable energy sources analysed in this paper include the energy from photovoltaics, wind turbines and hydroelectric power. The goal and scope of the analysis comprise the assessment of environmental impacts of production of 1 GJ of energy from the sources mentioned above. The study will cover the construction, operation and waste disposal at each power plant. Analysis will cover the impact categories, where the environmental influence is the most significant, i.e. resource depletion, global warmth potential, acidification and eutrophication. The LCA results will be shown on the basis of European and Australian research. This analysis will be extended with a comparison between environmental impacts of energy from renewable and conventional sources. This report will conclude with an analysis of possibilities of application of the existing research results and LCA rules in the Polish energy industry with a focus on Poland's future accession to the European Union. Definitions of LCA fundamental concepts, its methodology and application are described in the ISO 14040-14049 series of standards. These standards have already been introduced in some countries, but in Poland they are still at the stage of translation into Polish. Nevertheless some companies in Poland try to assess how their products influence the environment and what are the possibilities of technology improvement in the existing production process reduce their environmental impact.     

10 MW大型单桩式海上风机桩土作用研究

[目的]世界范围内已经建成的海上风场大部分位于浅水区域（水深<30 m）,主要以单桩等固定式基础为主。随着风电技术的不断成熟,海上风电逐渐走向机组大型化趋势,而单桩海上风机的基础直径也将随着机组大型化而增加。其所受到的环境载荷和土质条件要求也愈加严苛,对于大直径单桩式海上风机的桩土相互作用的研究成为海上风电技术的关键技术问题之一。[方法]拟对浅水水域10 MW大型海上风机,研究不同桩土模型对大型单桩海上风机的动力响应的影响。[结果]结果表明,宏单元法考虑了非线性的刚度与塑性,在特征频率附近的功率谱密度总和大,对比其他传统桩土模型时有很大的优势。[结论]所做研究对风机的整体安全运行具有深远的理论价值与工程应用前景。     

Life cycle environmental impact comparison of solid oxide fuel cells fueled by natural gas,hydrogen, ammonia and methanol for combined heat and power generation

This study aims to provide a comprehensive environmental life cycle assessment of heat and power production through solid oxide fuel cells (SOFCs) fueled by various chemical feeds namely; natural gas, hydrogen, ammonia and methanol. The life cycle assessment (LCA) includes the complete phases from raw material extraction or chemical fuel synthesis to consumption in the electrochemical reaction as a cradle-to-grave approach. The LCA study is performed using GaBi software, where the selected impact assessment methodology is ReCiPe 1.08. The selected environmental impact categories are climate change, fossil depletion, human toxicity, water depletion, particulate matter formation, and photochemical oxidant formation. The production pathways of the feed gases are selected based on the mature technologies as well as emerging water electrolysis via wind electricity. Natural gas is extracted from the wells and processed in the processing plant to be fed to SOFC. Hydrogen is generated by steam methane reforming method using the natural gas in the plant. Methanol is also produced by steam methane reforming and methanol synthesis reaction. Ammonia is synthesized using the hydrogen obtained from steam methane reforming and combined with nitrogen from air in a Haber-Bosch plant. Both hydrogen and ammonia are also produced via wind energy-driven decentralized electrolysis in order to emphasize the cleaner fuel production. The results of this study show that feeding SOFC systems with carbon-free fuels eliminates the greenhouse gas emissions during operation, however additional steps required for natural gas to hydrogen, ammonia and methanol conversion, make the complete process more environmentally problematic. However, if hydrogen and ammonia are produced from renewable sources such as wind-based electricity, the environmental impacts reduce significantly, yielding about 0.05 and 0.16 kg CO₂ eq., respectively, per kWh electricity generation from SOFC.     

新型海上风力发电及其关键技术研究

回顾国外海上风力发电场的发展,针对随着海水深度增加导致海上风力机成本急剧上升的矛盾,引入海上漂浮式风力机概念,并详细介绍其结构和特点,通过系统介绍海上漂浮式风力机组成部分和设计制造中的关键技术,最后得出海上漂浮式风机是一种潜力巨大的新型风力发电技术,值得进一步深入研究。同时,针对我国陆、海资源的具体情况,较为系统地提出了海上漂浮式风力机研究的需要关注的关键问题,指出了该研究所具有的巨大社会经济价值。     

新型张力腿平台漂浮式风力机动态响应研究

未来海上风电场的建设需要大量动态响应低且相互干扰小的漂浮式风力机,为此研究一种尺寸更小,能减少或防止相互间干扰及安装费用更低的新型张力腿平台漂浮式风力机(TLP风力机),基于辐射/绕射理论并结合有限元方法,运用水动力学软件AQWA对其在不同海况下及不同系泊系统下的动态响应进行模拟研究,得到了频域和时域的动态响应数据。结果表明:频域分析中,新型张力腿平台漂浮式风力机的运动响应主要集中在低频区域,其中横荡、垂荡及纵摇的峰值频率分别为0.1、0.35和0.19 rad/s;TLP风力机垂荡和纵摇方向上的运动响应都小于Spar风力机运动响应;横荡、垂荡及纵摇方向上,TLP风力机附加质量均远大于辐射阻尼;时域分析中,4根张紧系泊设计优于单根张紧系泊设计,能有效降低横荡和纵摇运动响应和延长系泊绳的寿命;随着海况恶劣程度的加剧,TLP风力机的动态响应也随之增大。     

Life cycle energy,emissions and cost inventory of power generation technologies in Singapore

Singapore is one of the most industrialised and urbanised economies in South-East Asia. Power supply is an important sub-system in its economy and heavily reliant on imported oil and natural gas. Due to its geographical area, clean/renewable energy sources for power generation are limited. At the same time, in its deregulated electricity market, the adoption of clean/renewable based power generation technology may be hindered by a market pricing mechanism that does not reflect externality costs. For a sustainable power supply, there is a need to change the conventional appraisal techniques. Life cycle assessment (LCA) and life cycle cost analysis (LCCA) are good tools to quantify environmental impacts and economic implications. LCA and LCCA are performed for centralised and distributed power generation technologies in Singapore, namely, oil and Orimulsion-fired steam turbines, natural gas-fired combined cycle plant, solar PV and fuel cell systems. A life cycle energy, emission and cost inventory is established. The results are discussed from the perspectives of fuel security, environmental protection and cost effectiveness of future power generation strategies for Singapore.     

A comparison of methods for assessing power output in non‐uniform onshore wind farms

Wind resource assessments are used to estimate a wind farm's power production during the planning process. It is important that these estimates are accurate, as they can impact financing agreements, transmission planning, and environmental targets. Here, we analyze the challenges in wind power estimation for onshore farms. Turbine wake effects are a strong determinant of farm power production. With given input wind conditions, wake losses typically cause downstream turbines to produce significantly less power than upstream turbines. These losses have been modeled extensively and are well understood under certain conditions. Most notably, validation of different model types has favored offshore farms. Models that capture the dynamics of offshore wind conditions do not necessarily perform equally as well for onshore wind farms. We analyze the capabilities of several different methods for estimating wind farm power production in 2 onshore farms with non‐uniform layouts. We compare the Jensen model to a number of statistical models, to meteorological downscaling techniques, and to using no model at all. We show that the complexities of some onshore farms result in wind conditions that are not accurately modeled by the Jensen wake decay techniques and that statistical methods have some strong advantages in practice.     

A comparative study on dynamic responses of spar‐type floating horizontal and vertical axis wind turbines

Interest in the exploitation of offshore wind resources using floating wind turbines has increased. Commercial development of floating horizontal axis wind turbines (FHAWTs) is emerging because of their commercial success in onshore and near‐shore areas. Floating vertical axis wind turbines (FVAWTs) are also promising because of their low installation and maintenance costs. Therefore, a comparative study on the dynamic responses of FHAWTs and FVAWTs is of great interest. In the present study, a FHAWT employing the 5MW wind turbine developed by the National Renewable Energy Laboratory (NREL) and a FVAWT employing a Darrieus rotor, both mounted on the OC3 spar buoy, were considered. An improved control strategy was introduced for FVAWTs to achieve an approximately constant mean generator power for the above rated wind speeds. Fully coupled time domain simulations were carried out using identical, directional aligned and correlated wind and wave conditions. Because of different aerodynamic load characteristics and control strategies, the FVAWT results in larger mean tower base bending moments and mooring line tensions above the rated wind speed. Because significant two‐per‐revolution aerodynamic loads act on the FVAWT, the generator power, tower base bending moments and delta line tensions show prominent two‐per‐revolution variation. Consequently, the FVAWT suffers from severe fatigue damage at the tower bottom. However, the dynamic performance of the FVAWT could be improved by increasing the number of blades, using helical blades or employing a more advanced control strategy, which requires additional research. Copyright © 2016 John Wiley & Sons, Ltd.     

Technical aspects of status and expected future trends for wind power in Denmark

The power system of Denmark is characterized by significant incorporation of wind power. Presently, more than 20% of the annual electricity consumption is covered by electricity‐producing wind turbines. The largest increase in grid‐incorporated wind power is expected to come from large (offshore) wind farms operating as large wind power plants with ride‐through solutions, connected to the high‐voltage transmission system and providing ancillary services to the system. In Denmark there are presently two offshore wind farms connected to the transmission system: Horns Rev A (160MW rated power in the western part of the country) and Nysted (165MW rated power at Rødsand in Eastern Denmark). The construction of two more offshore wind farms, totalling 400MW by the years 2008–2010, has been announced. This article presents the status, perspectives and technical challenges for wind power in the power system from the point of view of Energinet.dk, Transmission System Operator of Denmark. Copyright © 2006 John Wiley &Sons, Ltd