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.     

Preliminary study of the offshore wind and temperature profiles at the North of the Yucatán Peninsula

The stability conditions in the atmospheric boundary layer, the intensity of the wind speeds and consequently the energy potential available in offshore conditions are highly influenced by the distance from the coastline and the differences between the air and sea temperatures. This paper presents a preliminary research undertook to study the offshore wind and temperature vertical profiles at the North-West of the Yucatán Peninsula coast. Ten minute averages were recorded over approximately 2 years from sensors installed at two different heights on a communication tower located at 6.65 km from the coastline. The results have shown that the offshore wind is thermally driven by differential heating of land and sea producing breeze patterns which veer to blow parallel to the coast under the action of the Coriolis force. To investigate further, a dataset of hourly sea surface temperatures derived from GEOS Satellite thermal maps was combined with the onsite measured data to study its effect on the vertical temperature profile. The results suggested largely unstable conditions and the potentially development of a shallow Stable Internal Boundary Layer which occurs when warm air from the land advects over the cold sea.     

Low carbon society scenario analysis of transport sector of an emerging economy—The AIM/Enduse modelling approach

The transport sector of a country is the backbone driving the economy forward. Thailand’s land transport sector is modelled using the AIM/Enduse, which is a recursive dynamic optimization model, based on bottom-up modelling principle. The travel demand is divided into two major categories which are passenger travel and freight travel. The objective of this paper is to analyse the mitigation possible through low carbon society (LCS) measures and emission tax (ET). Two scenario clusters are devised along with the BAU case. The LCS scenario cluster has three designed scenarios which are LCS-L, LCS-M and LCS-H. The emission tax (ET) cluster has four scenarios, where the taxes of 50, 100, 200 and 500 USD/t-CO₂ are implemented. Along with this the marginal abatement costs (MAC) of the counter-measures (CMs) and the co-benefits in terms of energy security, productivity and air pollutant mitigation are also assessed. Results show that LCS scenarios are possible of mitigating up to 1230 Mt-CO₂ cumulatively, from 2010 to 2050. In terms of MACs, new vehicles play a pivotal role, along with hybrid vehicles. The Average Abatement Cost (AAC) assessment shows that the AAC of LCS-H scenario is in the order of 100 USD/t-CO₂. All the LCS and ET scenarios show an enhancement in energy security and also a threefold increase in productivity. There is distinct mitigation in terms of air pollutants from the transport sector as well.     

Provision of enhanced ancillary services from wind power plants – Examples and challenges

Emphasis in this article is on the power system impact of wind power plants capability to provide enhanced ancillary services, i.e. temporary frequency response (TFR) and power oscillation damping (POD). The main objective of the article is to analyze and justify the challenges in the use of TFR and POD from wind power plants (WPPs). The study is conducted with an aggregated wind power plant model which is integrated into a generic power system model, specifically designed to assess the targeted ancillary services in a relatively simple, but still relevant environment. Various case studies with different wind power penetration levels are considered.The study shows that WPPs can provide additional control features such as TFR and POD to enhance the stability of power systems with large share of wind power. Nevertheless, the results illustrate that the power system stability can be potentially degraded without careful coordination between WPPs, simultaneously providing TFR or POD in power systems with large displacement of conventional power plants by WPPs. The article provides to TSO new insights into the need for service coordination between WPPs into future power systems.     

Levelling the playing field? The influence of national wind power planning instruments on conflicts of interests in a Swedish county

Slow and complicated wind power planning and permitting procedures have been a large obstacle for wind power diffusion in Sweden and other countries. This paper complements previous siting-oriented literature with a planning perspective on these problems. The focus is two national planning instruments implemented in Sweden in the early 2000s: a national planning target and an appointment of areas of national interest for wind power. The paper identifies different types of conflicts of interest related to wind power – in addition to the conflict between wind power as a national public interest and various local private interests – and analyses the impact of the national planning instruments on the handling of these conflicts in the land-use planning process in the County of Östergötland. The analysis shows that the planning target actually made local planning officials even more inclined to treat wind power as a private rather than a public interest and that the method used to identify areas of national interest of wind power forced wind power to compete with the combined strengths of all other public interest. The planning instruments thus left wind power to fight an uphill battle rather than to meet other interests face-to-face on a level playing field.     

The effect of tartrate on the morphological and structural characteristics of lead–tin electrodeposit from an alkaline bath

The electrodeposition of Pb–Sn alloys from a tartrate-alkaline plating bath can lead to a deposition of pure lead or a normal codeposition of lead–tin depending on the deposition potential. The percentage of tin in the Pb–Sn deposit obtained at ∼−1.15 V increases from 4.08 wt.% to 20.7 wt.% as the charge density rises from 2.5 C cm⁻² to 5.0 C cm⁻² and then decreases from 12.07 wt.% to 7.52 wt.% as the charge density rises from 7.5 C cm⁻² to 10.0 C cm⁻². SEM images show that the Pb and Pb–Sn deposits obtained from a tartrate-alkaline bath did not, in general, show dendritic growth.     

The development and application practice of wind–solar energy hybrid generation systems in China

China is the largest developing country in the world. At present, more and more energy demand gives immense pressure to Chinese government. The inappropriate energy structure must be improved by Chinese government in order to achieve the sustainable development of economy and society. Development and application of renewable energy, such as wind energy, solar energy, biomass energy, etc., have been regarded by the government and the local people in the past 10 years, and more and more actual examples have been established, which are supported by government and plants in China. It is well known that there are abundant wind and solar resources in China. This paper presents the distribution zone and development and application practice status in China. However, a common drawback is existing in the stand-alone wind energy and solar energy generating power system, which is the unpredictable output electric power, and the output power depends on the unpredictable weather and climatic changes. Fortunately, the wind–solar hybrid generation system can partially overcome the problems. The conventional structure and key technology of stand-alone wind–solar hybrid generating system, the current status and outlook of wind–solar hybrid energy system are presented in the paper, for example, the city road lighting system, distributed generation, photovoltaic (PV) water pumping for irrigation, etc. At the end, the policies and laws of China central government and local governments are described, and the development barriers and recommendations are introduced.     

The influence of feedstock drying on the performance and economics of a biomass gasifier–engine CHP system

The need to dry biomass feedstocks before they can be gasified can place a large energy and capital cost burden on small-to-medium scale biomass gasification plants for the production of heat and power. Drying may not always be unavoidable, but as biomass moisture content to the gasifier increases, the quality of the product gas deteriorates along with the overall performance of the whole system. This system modelling study addresses the influence of feedstock moisture content both before and after drying on the performance and cost of a biomass gasifier–engine system for combined heat and power at a given scale and feedstock cost. The scale range considered 0.5–$\text{3.0}\text{MW}{}_{\mathrm{<mtext>e</mtext>}}$. The system comprises an updraft gasifier with external thermal and catalytic tar cracking reactors, gas clean-up and a spark-ignition gas engine. A spreadsheet-based system model is constructed, with individual worksheets corresponding to sub-models of system components, and a number of drying technology options and modes of operation are examined. Wherever possible, data supplied by manufacturers or taken from real systems is used in the construction of the sub-models, particularly in the derivation of cost functions.     

The value of domestic building energy efficiency — evidence from Ireland

Following the transposition of the EU Energy Performance of Buildings Directive into Irish law, all properties offered for sale or to let in Ireland are obliged to have an energy efficiency rating. This paper analyses the effect of energy efficiency ratings on the sale and rental prices of properties in the Republic of Ireland. Using the Heckman selection technique we model the decision to advertise the energy efficiency rating of a property and the effect of energy efficiency ratings on property values. Our results show that energy efficiency has a positive effect on both the sales and rental prices of properties, and that the effect is significantly stronger in the sales segment of the property market. We also analyse the effect of energy efficiency across different market conditions and we find that the effect of the energy rating is generally stronger where market conditions are worse.     

How certain are greenhouse gas reductions from bioenergy? Life cycle assessment and uncertainty analysis of wood pellet-to-electricity supply chains from forest residues

Climate change and energy policies often encourage bioenergy as a sustainable greenhouse gas (GHG) reduction option. Recent research has raised concerns about the climate change impacts of bioenergy as heterogeneous pathways of producing and converting biomass, indirect impacts, uncertainties within the bioenergy supply chains and evaluation methods generate large variation in emission profiles. This research examines the combustion of wood pellets from forest residues to generate electricity and considers uncertainties related to GHG emissions arising at different points within the supply chain. Different supply chain pathways were investigated by using life cycle assessment (LCA) to analyse the emissions and sensitivity analysis was used to identify the most significant factors influencing the overall GHG balance. The calculations showed in the best case results in GHG reductions of 83% compared to coal-fired electricity generation. When parameters such as different drying fuels, storage emission, dry matter losses and feedstock market changes were included the bioenergy emission profiles showed strong variation with up to 73% higher GHG emissions compared to coal. The impact of methane emissions during storage has shown to be particularly significant regarding uncertainty and increases in emissions. Investigation and management of losses and emissions during storage is therefore key to ensuring significant GHG reductions from biomass.     

The patent road of power battery unicorn——Analysis of CATL patent application and layout

本文从专利申请与布局角度出发,分析了宁德时代新能源科技股份有限公司的历年申请趋势、申请地域布局、申请技术布局、重点技术分支及研发路径等方面的基本情况,并将上述专利信息与企业自身发展及行业特点综合分析,总结出其成长为动力电池独角兽企业的深层原因,主要为专利申请与企业发展并行、兼顾海内外专利布局、工艺流程的持续改善、在优势领域提升研发专注度、在核心领域坚持自主创新,上述成功经验值得国内外同行或初创企业学习借鉴。     

The Connectedness of Some Varieties and the Deligne—Simpson Problem

The Deligne—Simpson problem (DSP) (respectively, the weak DSP) is formulated as follows: give necessary and sufficient conditions for the choice of the conjugacy classes C_j GL(n, ) or c_j gl(n, ) so that there exist irreducible (respectively, with trivial centralizer) (p + 1)-tuples of matrices M_j C_j or A_j c_j satisfying the equality M₁ ... M_p+1 = I or A₁ + ... + A_p+1 = 0. The matrices M_j and A_j are interpreted as monodromy operators of regular linear systems and as matrices-residua of Fuchsian ones on the Riemann sphere. For ((p + 1))-tuples of conjugacy classes one of which is with distinct eigenvalues we prove that the variety {(M₁, ..., M_p+1) | M_j C_j, M₁ ... M_p+1 = I} or {(A₁, ..., A_p+1) | A_j c_j, A₁ + ... + A_p+1 = 0| is connected if the DSP is positively solved for the given conjugacy classes and give necessary and sufficient conditions for the positive solvability of the weak DSP.2000 Mathematics Subject Classification. 15A30, 15A24, 20G05.     

Critical Heat Flux in Flow Boiling—Review of the Current Understanding and Experimental Approaches

ABSTRACT

A comprehensive review of current literature on subcooled flow boiling with a focus on the mechanistic modeling of the departure from nucleate boiling is presented. This review covers parametric trends, other reviews on the topic, previous modeling approaches, applicable measurement techniques for two-phase flow, and an extensive literature review on mechanistic models for the prediction of critical heat flux (CHF). The models have been carefully deconstructed to give an overview about differences and similarities in the respective modeling approaches. Drawing on previously successful application of measurement techniques for two-phase flow, recommendations for future experimental investigation regarding specific parameters of the respective models are given for the refinement of the current modeling approaches of CHF phenomena.     

Technical aspects of production and analysis of biodiesel from used cooking oil—A review

The increasing awareness of the depletion of fossil fuel resources and the environmental benefits of biodiesel fuel has made it more attractive in recent times. The cost of biodiesel, however, is the major hurdle to its commercialization in comparison to petroleum-based diesel fuel. The high cost is primarily due to the raw material, mostly neat vegetable oil. Used cooking oil is one of the economical sources for biodiesel production. However, the products formed during frying, can affect the transesterification reaction and the biodiesel properties. This paper attempts to review various technological methods of biodiesel production from used cooking oil. The analytical methods for high quality biodiesel fuel from used cooking oil like GC, TLC, HPLC, GPC and TGA have also been summarized in this paper. In addition, the specifications provided by different countries are presented. The fuel properties of biodiesel fuel from used cooking oil were also reviewed and compared with those of conventional diesel fuel.     

LEAPs and Bounds—an Energy Demand and Constraint Optimised Model of the Irish Energy System

This paper builds a model of energy demand and supply for Ireland with a focus on evaluating, and providing insights for, energy efficiency policies. The demand-side comprises sectoral sub-models, with a detailed bottom–up approach used for the transport and residential sectors and a top–down approach used for the industry and services sectors. The supply side uses the linear programming optimisation features of the Open Source Energy Modelling System applied to electricity generation to calculate the least-cost solution. This paper presents the first national level model developed within the Long Range Energy Alternatives Planning software to combine detailed end-use analysis on the demand side with a cost-minimising optimisation approach for modelling the electricity generation sector. Through three scenarios over the period 2009–2020, the model examines the aggregate impact on energy demand of a selection of current and proposed energy efficiency policies. In 2020, energy demand in the energy efficiency scenario is 8.6 % lower than the reference scenario and 11.1 % lower in the energy efficiency?+?scenario.     

The Structure of Cool Flame Fronts of Pentane,Iso—Pentane and Their Mixture

IntroductionInvestigations of flame structure of stabilized coolflames are important to understand the processes of fuelconversion in both cool and hot flames [i'2].According to current understanding, the cool flameis considered to be a precursor of the hot flame, soprocesses occulting in the cool flame should affect thestfIJctllre of subsequent hot flame. Cool flames producea negative temperature coefficient in the rate ofhydrocarbon oxidation in the low temperature region ofthe flame front …     

Biofuels from microalgae—A review of technologies for production,processing, and extractions of biofuels and co-products

Sustainability is a key principle in natural resource management, and it involves operational efficiency, minimisation of environmental impact and socio-economic considerations; all of which are interdependent. It has become increasingly obvious that continued reliance on fossil fuel energy resources is unsustainable, owing to both depleting world reserves and the green house gas emissions associated with their use. Therefore, there are vigorous research initiatives aimed at developing alternative renewable and potentially carbon neutral solid, liquid and gaseous biofuels as alternative energy resources. However, alternate energy resources akin to first generation biofuels derived from terrestrial crops such as sugarcane, sugar beet, maize and rapeseed place an enormous strain on world food markets, contribute to water shortages and precipitate the destruction of the world's forests. Second generation biofuels derived from lignocellulosic agriculture and forest residues and from non-food crop feedstocks address some of the above problems; however there is concern over competing land use or required land use changes. Therefore, based on current knowledge and technology projections, third generation biofuels specifically derived from microalgae are considered to be a technically viable alternative energy resource that is devoid of the major drawbacks associated with first and second generation biofuels. Microalgae are photosynthetic microorganisms with simple growing requirements (light, sugars, CO₂, N, P, and K) that can produce lipids, proteins and carbohydrates in large amounts over short periods of time. These products can be processed into both biofuels and valuable co-products.This study reviewed the technologies underpinning microalgae-to-biofuels systems, focusing on the biomass production, harvesting, conversion technologies, and the extraction of useful co-products. It also reviewed the synergistic coupling of microalgae propagation with carbon sequestration and wastewater treatment potential for mitigation of environmental impacts associated with energy conversion and utilisation. It was found that, whereas there are outstanding issues related to photosynthetic efficiencies and biomass output, microalgae-derived biofuels could progressively substitute a significant proportion of the fossil fuels required to meet the growing energy demand.     

Creating a level playing field? The concentration and centralisation of emissions in the European Union Emissions Trading System

This article questions the assumption that carbon markets create a level playing field by exploring the relationship between the organisation of capital and the organisation of emissions in the European Union Emissions Trading System (EU ETS). It constructs a database by matching installations and owners to reveal that a relatively small number of large-scale coal-fired power stations, owned by a very small group of states and corporations, are responsible for a significant proportion of greenhouse gas emissions. The findings are analysed by considering how technological dependence on coal together with the corporate institutional form combine to support the socio-spatial concentration and centralisation of capital and emissions. Case studies of the consolidation of the seven largest polluting owners from Europe's coal-dependent electricity sector and the carbon trading strategies of the two largest polluters, RWE and E.ON, then assess the impacts of energy liberalisation and emissions trading policies. The article concludes that EU energy and climate policies are pulling in different directions by clustering responsibility for greenhouse gas emissions and diffusing responsibility to address climate change. The uneven distribution of emissions within the EU ETS makes an alternative policy approach that directly targets the biggest corporate and state polluters both feasible and necessary.     

The Mechanisms of Flame Stabilization and Low NO_x Emission in an Eccentric Jet Pulverized Coal Combustor

The mechanisms of flame stabilization and low NO_x emission features of an eccentric jet pulverized coal com-bustor were studied through numerical modelling and experimental investigation.The results show that theformation of the unique flowfield structure is closely related to the interaction among combustor configuration,the primary jet and the control jet;and that certain rules should be followed in order to obtain the optimumcondition for flame stabilization.The distributions of temperature and concentrations of NO,O_2,CO and CO_2inside the combustor were experimentally measured.The effects of structural and operational parameters oncombustion and NO formation were studied.It was found that reduction of primary air,suitable use of controljet and reasonable uptilt angle of the primary jet all contributed to the reduction of NO_x at the combustor exit.A new hypothesis,that reasonable separation of oxygen and fuel within the fuel-rich zone is beneficial to furtherreduction of NO_x emission,is given.The study showed that good compatibility existed between the capabilityof flame stabilization and low NO_x emission for this type of combustor.     

Concentration of Major and Trace Elements in the Miocene Lignite from the Çanakkale-Çan Coalfield

Abstract

This study focuses on major and trace element concentrations of three lignite samples, of which two are from the working lignite seam and one from a feed coal to Çan thermal power plant. The Çanakkale-Çan lignite deposit is currently being mined by open-cast mining methods despite its high sulfur content. The production lignites are mainly consumed by Çan fluidized-bed thermal power plant with 2 × 160 MW capacity and less domestic heating and industrial factories around Çan. Major oxide compositions of the coal ash samples imply that the more abundant oxides are SiO₂ and Al₂O₃ and less CaO and Fe₂O₃. Trace element concentrations in the samples on whole-coal basis show that three samples analyzed were enriched in V, and also concentrations of B, Sc, Sn, Th, Tl, and U in one sample that exceed the range values of most world coals.