Extracting fatigue damage parts from the stress–time history of horizontal axis wind turbine blades

Horizontal axis wind turbine (HAWT) blades are a critical component of wind turbines. Full-scale blade fatigue testing is required to verify that the blades possess the strength and service life specified in the design. Unfortunately, fatigue tests must be run for a long time period, which has led blade testing laboratories to seek ways of accelerating fatigue testing time and reducing the costs of tests. The objective of this article is to propose a concept of applying accumulative power spectral density (AccPSD) to identify fatigue damage events contained in the stress–time history of HAWT blades. Based on short-time Fourier transform (STFT), a novel method called STFT-based fatigue damage part extracting method has been developed to extract fatigue damage parts from the stress–time history and to generate the edited stress–time history. It has been found that a STFT window size of 256 and an AccPSD level of 9800 Energy/Hz (cutoff level) provides the edited stress–time history having reduction of 15.38% in length with respect to the original length, whilst fatigue damage per repetition can be retained almost the same level as the original fatigue damage. In addition, an existing method, time correlated fatigue damage (TCFD), is used to validate the effectiveness of STFT-based fatigue damage part extracting method. The results suggest that not only does the STFT improve the accuracy of fatigue damage retained, but also it provides a shorter length of the edited stress–time history. To conclude, STFT is suggested as an alternative technique in fatigue durability study, especially for the field of wind turbine engineering.     

Austria's wind energy potential – A participatory modeling approach to assess socio-political and market acceptance

Techno-economic assessments confirm the potential of wind energy to contribute to a low carbon bioeconomy. The increasing diffusion of wind energy, however, has turned wind energy acceptance into a significant barrier with respect to the deployment of wind turbines. This article assesses whether, and at what cost, Austrian renewable energy targets can be met under different expansion scenarios considering the socio-political and market acceptance of wind energy. Land-use scenarios have been defined in a participatory modeling approach with stakeholders from various interest groups. We calculated the levelized cost of electricity (LCOE) for all of the potential wind turbine sites, which we used to generate wind energy supply curves. The results show that wind energy production could be expanded to 20% of the final end energy demand in three out of four scenarios. However, more restrictive criteria increase LCOE by up to 20%. In contrast to common views that see local opposition against wind projects as the main barrier for wind power expansion, our participatory modeling approach indicates that even on the level of key stakeholders, the future possible contribution of wind energy to Austrian renewable energy targets reaches from almost no further expansion to very high shares of wind energy.     

A twin unidirectional impulse turbine topology for OWC based wave energy plants – Experimental validation and scaling

The twin unidirectional turbine topology was recently proposed with the promise of very significant improvements in the energy capture in Oscillating Water Column (OWC) based wave energy plants. Here, we present the initial results of the experimental validation of the twin unidirectional impulse turbine topology. A scale model of the concept was built and tested using simulated bidirectional flow. The model consists of two 165 mm impulse turbines each individually coupled to 375 W grid connected induction machines. An oscillatory flow test rig was used to simulate bidirectional flow to test the model. The results of the experiments validate the concept of the twin turbine configuration. The proposed topology utilizes no moving parts and achieves more than 50% efficiency over a broad range of flow coefficients. A comparison with other competing turbines (viz, a twin Wells’ turbine, a linked guide vane impulse turbine and a fixed guide vane impulse turbine) is done, based on actual measurements in the Indian wave energy plant. The results from the experiments are scaled to evaluate the design features of a 50 GWh wave energy plant.     

Modeling technological change in energy systems – From optimization to agent-based modeling

Operational optimization models are one of the main streams in modeling energy systems. Agent-based modeling and simulation seem to be another approach getting popular in this field. In either optimization or agent-based modeling practices, technological change in energy systems is a very important and inevitable factor that researchers need to deal with. By introducing three stylized models, namely, a traditional optimization model, an optimization model with endogenous technological change, and an agent-based model, all of which were developed based on the same deliberately simplified energy system, this paper compares how technological change is treated differently in different modeling practices for energy systems, the different philosophies underlying them, and the advantages/disadvantages of each modeling practice. Finally, this paper identifies the different contexts suitable for applying optimization models and agent-based models in decision support regarding energy systems.     

An interval full-infinite mixed-integer programming method for planning municipal energy systems – A case study of Beijing

In this study, an interval full-infinite mixed-integer municipal-scale energy model (IFMI-MEM) is developed for planning energy systems of Beijing. IFMI-MEM is based on an integration of existing interval-parameter programming (IPP), mixed-integer linear programming (MILP) and full-infinite programming (FIP) techniques. IFMI-MEM allows uncertainties expressed as determinates, crisp interval values and functional intervals to be incorporated within a general optimization framework. It can also facilitate capacity-expansion planning for energy-production facilities within a multi-period and multi-option context. Then, IFMI-MEM is applied to a real case study of energy systems planning in Beijing. The results indicate that reasonable solutions have been generated. They are helpful for supporting (a) adjustment of the existing demand and supply patterns of energy resources, (b) facilitation of dynamic analysis for decisions of capacity expansion and/or development planning, and (c) coordination of the conflict interactions among economic cost, system efficiency, pollutant mitigation and energy-supply security.     

A network analysis using metadata to investigate innovation in clean-tech – Implications for energy policy

Clean-technology (clean-tech) is a large and increasing sector. Research and development (R&D) is the lifeline of the industry and innovation is fostered by a plethora of high-tech start-ups and small and medium-sized enterprises (SMEs). Any empirical-based attempt to detect the pattern of technological innovation in the industry is challenging. This paper proposes an investigation of innovation in clean-tech using metadata provided by CrunchBase. Metadata reveal information on markets, products, services and technologies driving innovation in the clean-tech industry worldwide and for San Francisco, the leader in clean-tech innovation with more than two hundred specialised companies. A network analysis using metadata is the employed methodology and the main metrics of the resulting networks are discussed from an economic point of view. The purpose of the paper is to understand specifically specializations and technological complementarities underlying innovative companies, detect emerging industrial clusters at the global and local/metropolitan level and, finally, suggest a way to realize whether observed start-ups, SMEs and clusters follow a technological path of complementary innovation and market opportunity or, instead, present a risk of lock-in. The discussion of the results of the network analysis shows interesting implications for energy policy, particularly useful from an operational point of view.     

The MIND method: A decision support for optimization of industrial energy systems – Principles and case studies

Changes in complex industrial energy systems require adequate tools to be evaluated satisfactorily. The MIND method (Method for analysis of INDustrial energy systems) is a flexible method constructed as decision support for different types of analyses of industrial energy systems. It is based on Mixed Integer Linear Programming (MILP) and developed at Linköping University in Sweden. Several industries, ranging from the food industry to the pulp and paper industry, have hitherto been modelled and analyzed using the MIND method. In this paper the principles regarding the use of the method and the creation of constraints of the modelled system are presented. Two case studies are also included, a dairy and a pulp and paper mill, that focus some measures that can be evaluated using the MIND method, e.g. load shaping, fuel conversion and introduction of energy efficiency measures. The case studies illustrate the use of the method and its strengths and weaknesses. The results from the case studies are related to the main issues stated by the European Commission, such as reduction of greenhouse gas emissions, improvements regarding security of supply and increased use of renewable energy, and show great potential as regards both cost reductions and possible load shifting.     

High-temperature electrolysis for large-scale hydrogen production from nuclear energy – Experimental investigations

The Idaho National Laboratory (INL) is currently assessing the feasibility of using solid-oxide based electrolysis cell technology for high temperature electrolysis of steam for large-scale hydrogen production. In parallel, the INL is studying the simultaneous electrolysis of steam and carbon dioxide for syngas (hydrogen/carbon monoxide mixture) production. When linked to a nuclear power source, this technology provides a carbon neutral means of producing syngas while consuming CO₂. The scope of experimental investigations at the INL includes single button cell tests, multi-cell stacks, and multi-stack systems. Multi-cell stack testing used 10 cm × 10 cm (8 cm × 8 cm active area) or 20 cm × 20 cm (18 cm × 18 cm active area) planar cells supplied by Ceramatec, Inc (Salt Lake City, Utah, USA). Multi-stack testing encompassed up to 720 10 cm × 10 cm cells and was conducted in a newly developed 15 kW Integrated Laboratory Scale (ILS) test facility. Gas composition, operating voltage, and operating temperature were varied during testing. The tests were heavily instrumented, and outlet gas compositions were monitored with a gas chromatograph. Results to date show the process to be a promising technique for large-scale hydrogen and syngas production.     

Improving appraisal of sustainability of energy options – A view from Slovenia

The new Slovenian approach to systematic, transparent, and reproducible appraisal of sustainability as related to electricity production is presented. The common sustainability components, i.e. economy, environment, and society, are integrated into evaluation of the feasibility, rationality, and uncertainty of the energy mix alternatives. A three stage model has been applied for this sustainability appraisal. The first level deals with alternative technologies for electricity production, the second with alternative mixtures of technologies for meeting electricity needs by 2050, and the third takes into account the expected timing of shutting-down existing old power plants and constructing the new ones. Technology alternatives cover both conventional and renewable energy sources: coal fired, gas fired, biomass fired, oil fired, nuclear, hydro, wind, and photovoltaic. The results show that only mixtures of nuclear, hydro, and gas fired technologies are reliable and rational in the context of meeting expected energy needs. The expected share of energy produced by wind and photovoltaic technology is between 8% and 15%, which makes them less sustainable than other technologies. Eventually, they do not meet sustainability goals from the economic and social points of view.     

A new method of energy degradation on-line analysis for coal-fired unit—expansion line approximating method

An energy degradation analysis process of unit and thermal system for coal-fired power plant under condition at discretion is discussed when load has been changed greatly in this paper. A new method of expansion line approximating method, which can rationally calculate the quantity of every component of energy degradation and identify the places where energy degradations arise, is put forward. In addition, the quality of every component of energy degradation is also discussed.     

Thermoeconomic modeling and parametric study of hybrid SOFC–gas turbine–steam turbine power plants ranging from 1.5 to 10 MWe

Detailed thermodynamic, kinetic, geometric, and cost models are developed, implemented, and validated for the synthesis/design and operational analysis of hybrid SOFC–gas turbine–steam turbine systems ranging in size from 1.5 to 10 MWe. The fuel cell model used in this research work is based on a tubular Siemens-Westinghouse-type SOFC, which is integrated with a gas turbine and a heat recovery steam generator (HRSG) integrated in turn with a steam turbine cycle. The current work considers the possible benefits of using the exhaust gases in a HRSG in order to produce steam which drives a steam turbine for additional power output. Four different steam turbine cycles are considered in this research work: a single-pressure, a dual-pressure, a triple pressure, and a triple pressure with reheat. The models have been developed to function both at design (full load) and off-design (partial load) conditions. In addition, different solid oxide fuel cell sizes are examined to assure a proper selection of SOFC size based on efficiency or cost. The thermoeconomic analysis includes cost functions developed specifically for the different system and component sizes (capacities) analyzed. A parametric study is used to determine the most viable system/component syntheses/designs based on maximizing total system efficiency or minimizing total system life cycle cost.     

Wind turbine availability: Should it be time or energy based? – A case study in Ireland

This paper describes a method for quantifying wind farm availability using two different approaches and comparing the results. Wind turbine suppliers regularly guarantee turbine availability in terms of time. A typical value of 97% is generally taken as the industry standard. This paper shows that this guarantee can potentially under-compensate the wind farm operator for losses sustained depending on when the period of non-availability occurs. Here we present an alternative method to quantify wind farm availability based on energy, which relates the energy losses in an Irish wind farm in 2007 to periods of turbine non-availability. It is shown in this analysis completed at this operational wind farm that while the technical non-availability as a percentage of time is 3%, the percentage of energy lost during downtimes is actually 11%. Based on the financial analysis above, the financial losses are significant. To answer the question should wind turbine availability be time or energy based, this paper shows that it can be advantageous for wind turbine owners to have energy-based calculations as long as the developers have sufficient monitoring of not only wind speed but also SCADA data.     

A strategy for reducing CO2 emissions from buildings with the Kaya identity – A Swiss energy system analysis and a case study

Within the general context of Greenhouse Gas (GHG) emissions reduction, decomposition analysis allows the quantification of the contribution of different factors to changes in emissions as well as the assessment of the effectiveness of policy and technology measures. The Kaya identity has been widely used for that purpose in order to disaggregate carbon emissions into various driving forces. In this paper, it is applied for the analysis of emissions resulting from energy use at three different scales. First, a decomposition analysis of the carbon emissions for the complete Swiss energy system is presented using the future projections from the Swiss Energy Strategy 2050. The Kaya identity is then applied to the Swiss building sector after it is adapted with factors that are more relatable to building parameters, such as floor area instead of Gross Domestic Product (GDP). Finally, the last level of analysis is a small scale community energy system for a unique Swiss village that aims to significantly reduce its emissions. An energy strategy is developed and its effectiveness is assessed with the adapted Kaya identity and benchmarked against the Swiss average values. The presented method demonstrates how the performance of buildings under various retrofitting scenarios can be benchmarked against future emission targets.     

An energy efficient Swedish pulp and paper industry – exploring barriers to and driving forces for cost-effective energy efficiency investments

Despite the need for increased industrial energy efficiency, studies indicate that cost-effective energy efficiency measures are not always implemented, which is explained by the existence of barriers to energy efficiency. This paper investigates whether this holds for the Swedish pulp and paper industry, and if so, investigates the barriers inhibiting and the driving forces stressing cost-effective energy efficiency investments. By so, this case study covers about 2% of the EU-25 industrial end-use of energy. The overall results from a questionnaire show that there is an energy efficiency gap in the sector and that the largest barriers were technical risks such as risk of production disruptions, cost of production disruption/hassle/inconvenience, technology inappropriate at the mill, lack of time and other priorities, lack of access to capital, and slim organization. As regards the driving forces for energy efficiency, the highest ranked driving forces were cost reductions resulting from lower energy use, people with real ambition, long-term energy strategy, the threat of rising energy prices, the electricity certificate system, the PFE. The results show that many of the barriers and driving forces were not solely market-related, e.g., lack of time or other priorities, slim organization, other priorities for capital investments, lack of staff awareness, and long decision chains indicate that firm-specific barriers plays an important role. These barriers may not be overcome by market-related public policy instruments but is rather a consequence of how the energy issue is organized within the firms. The second and the third largest driving forces, people with real ambition and a long-term energy strategy further support this.

Is energy cropping in Europe compatible with biodiversity? – Opportunities and threats to biodiversity from land-based production of biomass for bioenergy purposes

Based on literature and six country studies (Belgium, Denmark, Finland, Netherlands, Sweden, Slovakia) this paper discusses the compatibility of the EU 2020 targets for renewable energy with conservation of biodiversity.We conclude that increased demand for biomass for bioenergy purposes may lead to a continued conversion of valuable habitats into productive lands and to intensification, which both have negative effects on biodiversity. On the other hand, increased demand for biomass also provides opportunities for biodiversity, both within existing productive lands and in abandoned or degraded lands. Perennial crops may lead to increased diversity in crop patterns, lower input uses, and higher landscape structural diversity which may all have positive effects on biodiversity.In production forest opportunities exist to harvest primary wood residues. Removal of these forest residues under strict sustainability conditions may become economically attractive with increased biomass demand.An additional biomass potential is represented by recreation areas, road-side verges, semi-natural and natural areas and lands which have no other use because they have been abandoned, polluted or degraded.Whether effects of cropping of biomass and/or removal of biomass has positive or negative impact on biodiversity depends strongly on specific regional circumstances, the type of land and land use shifts involved and the associated management practices in general. However, it is clear that in the six countries studied certain types of biomass crops are likely to be more sustainable than others.     

Activated carbon from grass – A green alternative catalyst support for water electrolysis

Grass blades (turf grass) have been selected as a cheap biomass source of producing activated carbon for supporting Pt particles for utilizing as electrocatalyst for H₂ generation through electrolysis of water. Activation is done using ZnCl₂ followed by thermal processing at 250 °C. 1% Pt was supported over the grass derived activated biomass carbon (G-ABC) powder to result in Pt@G-ABC. After physical characterization, Pt@G-ABC sample has been tested for its catalytic activity in 1 M sulfuric acid solution for H₂ gas generation through Linear Sweep & Cyclic Voltammetry. Cost factor involved in the production of G-ABC has also been compared with the traditional commercially available carbon support. The studies suggest that grass may be considered not only as a potential alternative source for producing carbon supported catalyst for H₂ generation but also highlight the production of low-cost carbon for further applications like electrode materials, adsorbent for color, odor and hazardous pollutants.     

Realizing energy infrastructure projects – A qualitative empirical analysis of local practices to address social acceptance

The federal state of Upper Austria, at a crossing point for European energy grids, provides large-scale resources for storage of natural gas and is among the top infrastructures in this regard in Europe. Considering the ambitious plans for enhancements of energy infrastructures in this region, the issue of social acceptance of energy infrastructure is crucial. To foster an understanding of the challenges inherent in this issue we present an analysis concentrating on the social acceptance of energy infrastructure projects in Upper Austria. This paper addresses the issues with realizing energy infrastructure projects and analyzes the problems and benefits based on an empirical–qualitative study comprising expert interviews, discussions with stakeholders, and a round table workshop integrating the disparate viewpoints. The aim of the process was to integrate different attitudes, perspectives and positions of relevant stakeholders, members of citizens’ initiatives, environmental organizations and of the national government and local authorities. The results presented are based on both the analysis of the empirical–qualitative data and the existing studies and literature on social acceptance. The qualitative research compares experiences and current practices with social acceptance issues (like frameworks, participation, communication strategies) in a set of considered energy infrastructure projects.     

Urban lignocellulosic biomass can significantly contribute to energy production in municipal wastewater treatment plants – A GIS-based approach for a metropolitan area

The common fermentation of biogenic wastes and sewage sludge in digesters of municipal wastewater treatment plants is a technically feasible and economically viable approach. As the number of rural biogas production sites is steadily increasing, the question has been raised which biomass feedstocks are left available in sufficient quantities to be used for energy generation at wastewater treatment plant level. The contribution of lignocellulosic biomass collected from urban areas is generally neglected within this context. In the present study, 24 urban substrates have been analyzed for their theoretical methane potential, while 13 of them were tested in batch assays for the determination of their practical achievable methane yield. The theoretical evaluation of the methane potential yielded values ranging between 0.393 and 0.576 Nm³ kgVS⁻¹. The methane yields obtained by batch assays showed significantly lower yields, which depends on the individual composition of the substrates in terms of lignin, hemicellulose and cellulose. A GIS spatial analysis for the Rhine-Ruhr metropolitan area was performed to evaluate the feasible capacity of urban biomass as co-fermentation feedstock in digesters of municipal wastewater treatment plants. The analysis revealed that green urban areas provide a significant quantity of biomass of 377 t_FM d⁻¹ that could cover 67% of the annual energy demand of twelve typical wastewater treatment plants located in the metropolis.     

A new experimental simulation method for the development of non-renewable hydrogen energy—Oil and gas resources

At present, the proportion of tight oil in non-renewable hydrogen energy is increasing. According to an initial exploration and attemptable practice on the exploration of tight oil, it is found that the cost can be controlled effectively and positive effects are achieved. But this technique cannot make sure the proppants filled uniformly in the long fracture. Several researches on the proppants migration experiment devices and factors influencing on proppant setting are reviewed and a new set of experimental device to simulate the laws of proppants setting in long fracture is developed. This device can simulate the main factors influencing proppants setting performance. It analyzes several factors such as wall filtration, construction displacement, sand concentration, proppant size and density, viscosity of fracturing fluid is used to rank the influencing degree of every factor. Considering the effects of mutual interference between proppants, width of fracture, rough fracture surface and fracture surface filtration during the proppants setting progress, the mathematical model of proppant setting is modified by adding sand concentration correction factor, wall effect correction factor and filtration correction factor. The experimental data verify the accuracy of the settlement model is established using the data getting from experiment.