An investigation into the potential barriers facing the development of offshore wind energy in Scotland: Case study – Firth of Forth offshore wind farm

The Scottish Executive has set ambitious targets of achieving 100% of electricity from renewable sources by 2020. As Scotland has the best offshore wind resources in Europe, the development of this energy source is crucial for reaching these targets. However, the development of offshore wind raises a number of issues related to economic viability, grid connection and public acceptability. This paper investigates these areas in greater depth, using a case study of the Firth of Forth offshore wind farm, in order to determine if these barriers can be overcome in time to make a valuable contribution to 2020 targets. Through interviews with relevant stakeholders, it emerged that there are various obstacles which are impeding progress in offshore wind development in Scotland. It became evident that stakeholder opposition, an inadequate renewable energy support mechanism, and the insufficient grid infrastructure off the Scottish coast are posing barriers, and hindering development. It became apparent that in order to overcome these barriers, a number of changes need to take place. A more inclusive approach to stakeholder engagement is required, which facilitates the sharing of knowledge. In order to improve the economic viability of offshore wind in Scotland, adopting a new mechanism which reduces risk and provides developers and investors with more certainty, would be more effective in encouraging offshore wind development. Finally, in order to overcome the most significant barrier, the grid, a more integrated and collaborative approach is required, which will share the burden of responsibility between the developer, Ofgem, and the National Grid.     

Estimating the offshore wind resources of the State of Ceará in Brazil

The onshore wind power is consolidated; the challenge is to reach the same level of maturity for offshore exploitation. Brazil has no offshore wind power plants and there are few studies in this direction. This paper aims to estimate the offshore wind resources in the State of Ceará, in Brazil. The investigation uses a mesoscale atmospheric computer model, the Regional Atmospheric Modeling System (RAMS), with horizontal resolution of 2 km, which estimates the offshore average wind speed, average wind direction, power density and turbulence taking into account the bathymetry data and navigation routes along the coast of Ceará. The wind potential was evaluated in three representative periods, La Niña, El Niño and Neutral year, analyzing the dry and rainy season for each period. The results indicate an average wind speed above 8 m/s and power density above 720 W/m² no matter the period evaluated, in the dry season. The predominant wind direction in the observed dry periods was from East to West and the turbulence intensity is smaller during dry season of El Niño. Besides, the bathymetry of the State of Ceará is shallow and the large ships route is far beyond the coast, offering no danger to future endeavors.     

Effect of downwind swells on offshore wind energy harvesting – A large-eddy simulation study

The effect of ocean downwind swells on the harvesting of offshore wind energy is studied using large-eddy simulation of fully developed wind turbine array boundary layers, which is dynamically coupled with high-order spectral simulation of sea-surface wave field with and without the presence of a downwind swell. For the two moderate wind speeds of 7 m/s and 10 m/s considered in this study, the swell is found to induce a temporal oscillation in the extracted wind power at the swell frequency, with a magnitude of 6.7% and 4.0% of the mean wind power output, respectively. Furthermore, the averaged wind power extraction is found to be increased by as much as 18.8% and 13.6%, respectively. Statistical analysis of the wind field indicates that the wind speed in the lower portion of the boundary layer oscillates periodically with fast wind above the swell trough and slow wind above the swell crest, resulting in the observed wind power oscillation. The wind above the swell accelerates due to the strong wave forcing, causes a net upward flux of kinetic energy into the wind turbine layer, and thus acts to increase the extracted wind power of the turbines. For a high wind speed of 17 m/s, the wave-induced motion becomes relatively weak and the swell effect on the wind turbine performance diminishes.     

Influence of local wind speed and direction on wind power dynamics – Application to offshore very short-term forecasting

Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some of these effects by means of statistical models. To this end, a benchmarking between two different families of varying-coefficient models (regime-switching and conditional parametric models) is carried out. The case of the offshore wind farm of Horns Rev in Denmark has been considered. The analysis is focused on one-step ahead forecasting and a time series resolution of 10 min. It has been found that the local wind direction contributes to model some features of the prevailing winds, such as the impact of the wind direction on the wind variability, whereas the non-linearities related to the power transformation process can be introduced by considering the local wind speed. In both cases, conditional parametric models showed a better performance than the one achieved by the regime-switching strategy. The results attained reinforce the idea that each explanatory variable allows the modelling of different underlying effects in the dynamics of wind power time series.     

Focus on the development of offshore wind power in China: Has the golden period come?

In recent years, Chinese Government paid more attention to the exploitation of offshore wind power, and it became an important trend in the development of wind power industry. However, the development of offshore wind power in China was still in the initial stage. Compared with land-based wind power, the development of off-shore wind power had not only weaknesses and uncertainties, but also strengths and opportunities. In order to research the development of offshore wind power, this paper summarized the aspects on policy, market, technology and development planning of offshore wind power in China, and then adopted SWOT method to analyze the influencing factors, which impact on the development of China's offshore wind power. At last, this article analyzed the internal and external factors that affect the golden period of offshore wind power development, and drew a conclusion that the golden period of offshore wind power in China will come in the future, and most likely around 2020.     

The economics of visual disamenity reductions of offshore wind farms—Review and suggestions from an emerging field

The offshore wind power generation market is currently experiencing large growth rates on a global scale and investments exceeding several billion euro are being made. From a welfare economic point of view there is a non-trivial economic trade-off between offshore wind generation costs and the visual impacts from offshore wind farms. Offshore wind farms close to the shore generate cheaper electricity, but also cause higher levels of visual impacts compared to locations at larger distances. In the present paper we carry out a review of the stated preference studies that have elicited the demand for visual disamenity reduction from offshore wind farms. The review has three objectives: (a) to present the results of the different surveys; (b) to explore the more technical parts of the different surveys; and (c) to present the frontiers in the assessment of the demand for visual disamenity reductions associated with offshore wind farm locations. The paper is based on the results from five different studies. The review indicates that locations of offshore wind farms which are close to the shore generate significant welfare losses and that these can be reduced by locating the wind farms at more distant locations. The results also show that the welfare economic costs vary in terms of a range of socio demographic characteristics, experience with wind turbines and recreational activities. Finally, the review suggests that the welfare impacts related to the spatial distribution of the wind farms, intergenerational effects and experience with wind turbines are potential areas that would be beneficial to explore in future studies.     

Effects of air psychrometrics on the exergetic efficiency of a wind farm at a coastal mountainous site – An experimental study

In this paper, the most important energy and exergy characteristics of wind energy were examined. Atmospheric variables as air temperature, humidity and pressure and their effects on the wind turbine output were investigated toward wind energy exploitation. It was shown that these usually disregarded meteorological parameters while planning new WFs (Wind Farms), in fact, do play an important role in the farm’s overall exergetic efficiency. The wind potential around a coastal mountainous area was studied based on field measurements. Understanding atmospheric parameters variation appears to be of great importance for estimating energy yield in rough terrain and in this paper special focus was given to that.     

Political and institutional analysis of the successes and failures of China’s wind power policy

This paper identifies and explains how political and institutional factors have determined the relative successes and failures of China’s wind power policy over the period 2005–2011. It finds that China has made significant progress in pursuing its wind power policy in terms of cumulative installed capacity, wind turbine manufacturing industry development and wind turbine cost, and argues that these achievements can be attributed to the political motives and institutional arrangements of the Chinese government as well as to institutional changes. On the other hand, the paper finds that there are two prominent policy failures, namely the low proportion of grid-connected capacity and the rising trend of wind turbine incidents. These have undermined the efficiency and effectiveness of China’s wind power program. The paper holds that the institutional sources for the first policy failure lies in the preference for setting wind power development targets in terms of installed capacity rather than generation and in coordination problems while the second policy failure lies in the lack of state technical codes for wind power integration and the unfair competition from the large state-owned power companies. The paper contributes to the academic literature on the political and institutional roles in China’s wind power policy.     

Experimental study of the influence of λ and intake temperature on combustion characteristics in an HCCI engine fueled with n-heptane

Combustion characteristics fueled with n-heptane were investigated experimentally in a retrofitted engine to realize homogeneous charge compression ignition (HCCI) combustion mode. The influence of intake temperature and λ on chemical reactions was analyzed. In-cylinder pressure, temperature, heat release rate and ignition timing profiles were obtained with variations of the intake temperature and λ. The oxidation process was divided into three phases and the main reactions were analyzed. The results show that the combustion of n-heptane is more sensitive to intake temperature than to λ. The reason is that the intake temperature has a more profound effect on the oxidation process than the effect of λ. Moreover, the increase of intake temperature can extend the range of λ, and an optimal intake temperature exists corresponding to the value of λ.     

Fluid flow and heat transfer in plasma reactors—I. Calculation of velocities,temperature profiles and mixing

A mathematical representation has been developed to describe the velocity field and the associated temperature and concentration fields in a plasma jet system, which involves the injection of additional gas streams. In the statement of the problem, allowance was made for the swirl of the plasma jet, and one important objective of the work was to explore the effect of this swirl on the principal process variables. It was found that swirl plays an important role in providing mixing between the plasma jet and a reactant or diluent gas stream introduced through an annular port. It was shown, furthermore, that the model may be used for representing the quenching of the system by an axi-symmetrically introduced gas stream, having a direction perpendicular to the axis of the jet.     

Stability of combustion waves in the Zeldovich–Liñán model

In this paper we investigate the stability of the premixed combustion waves in the Zeldovich–Liñán model in the adiabatic limit in two spatial dimensions. It is shown that either wave or cellular instabilities emerge for the Lewis number for fuel greater or smaller than one respectively. On the Lewis number for fuel vs activation energy parameter plane, the critical parameter curve for wave (cellular) instability is a monotonically decaying (increasing) function, which tends to one for large values of activation energies and grows infinitely (vanishes) as the activation energy is decreased to some critical value (zero). Decreasing the recombination parameter, which corresponds to the relation between the characteristic times of the branching and recombination reactions, makes the combustion waves more stable by increasing the region of parameter values for stable traveling wave solutions. Increasing the ambient temperature is demonstrated to have similar stabilizing effect on combustion waves. The effect of the varying the Lewis number for radicals is shown to be more complex and depends on the regime of recombination. It is demonstrated that as the critical parameter values for the onset of instability are crossed, either pulsating or cellular two-dimensional solutions emerge. The properties of these solutions are studied. A comparison of the results of this paper with known data from the literature for deflagration of hydrogen–oxygen mixtures is made.     

Comparative study of the break in process of post doped and sol–gel high temperature proton exchange membrane fuel cells

In this paper six High Temperature PEM (HTPEM) MEAs from two manufacturers have been tested. The MEAs are three Dapozol 77 from Danish Power Systems (DPS) with varying electrode composition and two Celtec P2100 and one Celtec P1000 from BASF. The break in process of the MEAs has been monitored using voltage measurements and impedance spectroscopy. The purpose of this study is twofold. One aim is to try and interpret the processes happening during break in. The other aim is to investigate whether the impedance spectra or the voltage profiles contain information that can be used to determine when an MEA has been broken in. To aid in the interpretation of the impedance spectra, equivalent circuit models are used. Three models are evaluated. The most detailed models produce the best fits but the most simple model is chosen, since it produces the most consistent results. The processes happening during break in cannot be determined with certainty but for the Celtec P MEAs the main changes seem to be related to improved electrode kinetics. Judging from the voltage and the fitted resistances, the Celtec P MEAs seem to have been broken in after 30 h. The Dapozol MEAs only undergo minor changes in impedance and voltage during the break in period. This may indicate that this MEA type can be used directly without the need for break in.     

Effect of composition and temperature on the burning velocity of the nitric oxide—hydrogen flame

The burning velocity of the nitric oxide-hydrogen flame has been measured at 1 atm, over the composition range 35–70% NO, for two initial temperatures, 298°K and 1023°K. In addition, the burning velocity of the 50% NO mixture was determined as a function of initial temperature over the temperature range 300 to 1000°K. A free radical mechanism is proposed in which the principal nitro-oxide destruction reaction is: H + NO = OH + N.     

Boosting solid oxide electrolyzer performance by fine tuning the microstructure of electrodes – Preliminary study

This paper addresses the concept of adjusting the microstructure of the supports of solid oxide electrolyzers in order to boost performance. While several earlier studies focused on maximizing performance, reducing degradation, adjusting operating conditions and introducing new materials or designs of electrolysis stack, the current study addresses potential improvement of the cell by fine tuning the microstructure without any major redesign of existing cells. In the proposed approach, the study combined numerical simulations with definition of the model, which can aid in predicting the performance of a cell with adjusted porosity of the electrode support, and preparation of modified cells with alternative pore forming agents and two alternative sintering temperature levels. Supports of solid oxide cells were sintered at 1350 and 1400 °C with pore former content of 25–35%. This resulted in the porosity of supports being in the range of 47–54%. Cells with 10Sc1CeSZ and 8YSZ electrolytes were investigated in operando.The proposed approach makes it possible to quantitatively and qualitatively assess the potential gain when the reference cell is slightly modified, according to guidelines obtained from the model. It was found that the proposed method to fine tune the microstructure can result in improved performance, with a clear indication that adjusting the sintering temperature has a stronger effect on the microstructure of the support than increasing the pore forming agent.     

What hinder the further development of wind power in China?—A socio-technical barrier study

Promoting wind power is a long-term strategy of China to respond to both energy shortage and environmental pollution. Stimulated by various incentive policies, wind power generation in China has achieved tremendous growth, with the cumulative installed capacity being the largest worldwide for five consecutive years since 2010. However, obstructed by various barriers, wind power provides only 2.6% of national electricity generation in China, despite the strong support from the government. From a socio-technical transition perspective, this paper aims to systematically analyze the barriers hindering the further development of China's wind power. A wind power niche model is established to illustrate the complex interactions among actors in the wind power industry and electricity supply regime. Then, qualitative content analysis is adopted to process the related evidence and data, and four categories of socio-technical barriers are identified, including technology, governance, infrastructure and culture barriers. The study shows that various interrelated barriers form a blocking mechanism which prohibits the further development of wind power in China. Policy suggestions are proposed to eliminate the barriers and further empower the wind power niche. The lesson learned from China can offer useful references for other economies to promote wind power industries of their own.     

An experimental study on the development of a β-type Stirling engine for low and moderate temperature heat sources

In this study, a β-type Stirling engine was designed and manufactured which works at relatively lower temperatures. To increase the heat transfer area, the inner surface of the displacer cylinder was augmented by means of growing spanwise slots. To perform a better approach to the theoretical Stirling cycle, the motion of displacer was governed by a lever. The engine block was used as pressurized working fluid reservoir. The escape of working fluid, through the end-pin bearing of crankshaft, was prevented by means of adapting an oil pool around the end-pin. Experimental results presented in this paper were obtained by testing the engine with air as working fluid. The hot end of the displacer cylinder was heated with a LPG flame and kept about 200 °C constant temperature throughout the testing period. The other end of the displacer cylinder was cooled with a water circulation having 27 °C temperature. Starting from ambient pressure, the engine was tested at several charge pressures up to 4.6 bars. Maximum power output was obtained at 2.8 bars charge pressure as 51.93 W at 453 rpm engine speed. The maximum torque was obtained as 1.17 Nm at 2.8 bars charge pressure. By comparing experimental work with theoretical work calculated by nodal analysis, the convective heat transfer coefficient at working fluid side of the displacer cylinder was predicted as 447 W/m² K for air. At maximum shaft power, the internal thermal efficiency of the engine was predicted as 15%.     

Light and stable LinB14(n=1–5) clusters for high capacity hydrogen storage at room temperature: A DFT study

In this article, we have explored the hydrogen (H₂) storage capacity of the Li doped B clusters Li_nB₁₄(n = 1–5) using density functional theory (DFT). The geometrical and Bader's topological parameters indicate that the clusters adsorb H₂ in the molecular form. The Li atom polarises the H₂ molecules for their effective adsorption on the clusters. The Li_nB₁₄ (n = 1–5) clusters are found to be stable even after H₂ adsorption at room temperature. The average adsorption energy is found to be in the range of 0.12–0.14 eV/H₂. Among the various clusters, the Li₅B₁₄ shows maximum H₂ storage capacity (13.89 wt%) at room temperature. The ADMP simulation reveals that within few femtoseconds (fs), the H₂ molecules begin to move away from the clusters and within 400 fs most of the H₂ molecules moved away from the clusters.     

Study of the NaBH4–NaBr system and the behaviour of its low temperature phase transition

A mechano-chemical method was used to synthesize solid solution Na(BH₄)_1-xBr_x with 0 ≤ x ≤ 1. Samples with compositions of x ≤ 0.333 were annealed, in order to form a single phase material. Bromide substitution leads to smaller unit cell size and lower temperature and enthalpy of the order-disorder phase transition of NaBH₄. There is a linear relation between the amount of substitution, the temperature, the enthalpy and the kinetics of the phase transition. This linear relation between enthalpy and amount of substitution can be expressed by the function ΔH = ?6.268x + 1.206 where x is the amount of substitution and ΔH is the enthalpy.     

A kinetic study on the structural and functional roles of lanthana in iron-based high temperature water–gas shift catalysts

The structural and functional roles of varying amounts of lanthana in co-precipitated high temperature Fe₂O₃/Cr₂O₃/CuO water–gas shift catalysts were studied at 1 atm and 350–425 °C temperature range.