普陀山-葫芦岛水道潮流能资源评估

针对潮流能资源丰富的舟山普陀山-葫芦岛水道,在利用FVCOM数值模式对该海域潮流场进行准确模拟分析的基础上,运用Flux法和Garret法对该海域的潮流能资源可开发量进行了评估及对比分析。结果表明:全区有效流时大于4 000 h的区域面积为310×10~4m~2,有效流时大于5 000 h的区域面积为87×10~4m~2;该水道潮流能理论功率由南向北呈递增趋势,北口代表断面最大,瞬时理论功率可达92 MW,中间断面次之,最大瞬时理论功率约为61.6 MW,南口代表断面的功率最小,最大瞬时理论功率约为24.9 MW。利用Flux方法计算该水道的资源可开发量为1.98~3.23 MW,Garret方法估算该水道的资源总量为5.33~6.08 MW,研究成果可为该海域即将开展的潮流能测试区泊位选址和示范工程规模设计提供科学依据。     

The role of tidal asymmetry in characterizing the tidal energy resource of Orkney

When selecting sites for marine renewable energy projects, there are a wide range of economical and practical constraints to be considered, from the magnitude of the resource through to proximity of grid connections. One factor that is not routinely considered in tidal energy site selection, yet which has an important role in quantifying the resource, is tidal asymmetry, i.e. variations between the flood and ebb phases of the tidal cycle. Here, we present theory and develop a high-resolution three-dimensional ROMS tidal model of Orkney to examine net power output for a range of sites along an energetic channel with varying degrees of tidal asymmetry. Since power output is related to velocity cubed, even small asymmetries in velocity lead to substantial asymmetries in power output. We also use the 3D model to assess how tidal asymmetry changes with height above the bed, i.e. representing different device hub heights, how asymmetry affects turbulence properties, and how asymmetry is influenced by wind-driven currents. Finally, although there is minimal potential for tidal phasing over our study site, we demonstrate that regions of opposing flood- versus ebb-dominant asymmetry occurring over short spatial scales can be aggregated to provide balanced power generation over the tidal cycle.     

潮流能开发技术研究进展

储量丰富、清洁无污染的潮流能近年成为人类研究开发的热点。西方发达国家在潮流能利用技术方面处于领先地位,已经进入商业化运行前期阶段。文章综述了国内外潮流能技术开发的进展和发电装置的研究现状、潮流能开发的相关技术难题,比较分析了不同潮流能水轮机的技术特点;通过对国内外潮流能利用技术的综合分析,对我国潮流能开发利用现状提出了建议。     

Effect of waves on the tidal energy resource at a planned tidal stream array

Wave–current interaction (WCI) processes can potentially alter tidal currents, and consequently affect the tidal stream resource at wave exposed sites. In this research, a high resolution coupled wave-tide model of a proposed tidal stream array has been developed. We investigated the effect of WCI processes on the tidal resource of the site for typical dominant wave scenarios of the region. We have implemented a simplified method to include the effect of waves on bottom friction. The results show that as a consequence of the combined effects of the wave radiation stresses and enhanced bottom friction, the tidal energy resource can be reduced by up to 20% and 15%, for extreme and mean winter wave scenarios, respectively. Whilst this study assessed the impact for a site relatively exposed to waves, the magnitude of this effect is variable depending on the wave climate of a region, and is expected to be different, particularly, in sites which are more exposed to waves. Such effects can be investigated in detail in future studies using a similar procedure to that presented here. It was also shown that the wind generated currents due to wind shear stress can alter the distribution of this effect.     

A review of the potential water quality impacts of tidal renewable energy systems

The continued increase in the demand for energy, growing recognition of climate change impacts, high oil and gas prices and the rapid depletion of fossil fuel reserves have led to an increased interest in the mass generation of electricity from renewable sources. Traditionally, this has been pursed through riverine hydropower plants, with onshore wind systems growing steadily in popularity and importance over the years. Other renewable energy resources, which were previously not economically attractive or technically feasible for large scale exploitation, are now being considered to form a significant part of the energy mix. Amongst these, marine and in particular, tidal energy resource has become a serious candidate for undergoing mass exploitation in the near future, particularly in places with a tidal range of 4 m or more. Tidal renewable energy systems are designed to extract the kinetic or potential energy flow and convert it into electricity. This can be achieved by placing tidal stream turbines in the path of high speed tidal currents or through tidal range schemes, where low head turbines are encapsulated in impoundment structures, much like in low head riverine hydropower schemes. It is thought that these systems, when implemented at scales required to generate substantial amounts of electricity, have the potential to significantly alter the tidal flow characteristics, which could have knock-on impacts on the hydro-environment. This review gathers together knowledge from different research areas to facilitate an evaluation of the potential hydro-environmental impacts of tidal renewable energy systems, with a particular focus on water quality. It highlights the relevance of hydro-environmental modelling in assessing potential impacts of proposed schemes and identifies areas where further research is needed. A case study is presented of recent modelling studies undertaken for the Severn Estuary.     

Vietnam's energy sector: A review of current energy policies and strategies

Since the introduction of market-oriented economy in 1986, Vietnam has made noticeable socio-economic progress. In this progress, the energy sector has played a vital role. This role is likely to deepen in the years to come as Vietnam strives to achieve even higher levels in economic progress. Such deepening in the role of energy, this paper argues, will heighten concerns about the security of energy supply, and economic, environmental, social and political consequences. In order to address these issues, Vietnam has over the last decade, developed a suite of energy policies. A deeper review of these policies suggests that they are typified by economic-growth orientation, exclusive focus on a single-sector or single issue, and largely neglect the significance of cross-sectoral and cross-thematic issues arising from the interdependencies between energy, economy, and the polity at large. The existing energy policy settings are, therefore, unlikely to be able to provide a satisfactory redress to the challenges noted above. This paper provides an overview of the current energy policies with a view to identify areas where further policy effort is needed in order to facilitate a sustainable development of the Vietnamese energy sector.     

A comprehensive review on biodiesel as an alternative energy resource and its characteristics

As the fossil fuels are depleting day by day, there is a need to find out an alternative fuel to fulfill the energy demand of the world. Biodiesel is one of the best available resources that have come to the forefront recently. In this paper, a detailed review has been conducted to highlight different related aspects to biodiesel industry. These aspects include, biodiesel feedstocks, extraction and production methods, properties and qualities of biodiesel, problems and potential solutions of using vegetable oil, advantages and disadvantages of biodiesel, the economical viability and finally the future of biodiesel. The literature reviewed was selective and critical. Highly rated journals in scientific indexes were the preferred choice, although other non-indexed publications, such as Scientific Research and Essays or some internal reports from highly reputed organizations such as International Energy Agency (IEA), Energy Information Administration (EIA) and British Petroleum (BP) have also been cited. Based on the overview presented, it is clear that the search for beneficial biodiesel sources should focus on feedstocks that do not compete with food crops, do not lead to land-clearing and provide greenhouse-gas reductions. These feedstocks include non-edible oils such as Jatropha curcas and Calophyllum inophyllum, and more recently microalgae and genetically engineered plants such as poplar and switchgrass have emerged to be very promising feedstocks for biodiesel production.It has been found that feedstock alone represents more than 75% of the overall biodiesel production cost. Therefore, selecting the best feedstock is vital to ensure low production cost. It has also been found that the continuity in transesterification process is another choice to minimize the production cost. Biodiesel is currently not economically feasible, and more research and technological development are needed. Thus supporting policies are important to promote biodiesel research and make their prices competitive with other conventional sources of energy. Currently, biodiesel can be more effective if used as a complement to other energy sources.     

How much energy can be extracted from moving water with a free surface: A question of importance in the field of tidal current energy?

This short technical note addresses the extraction of energy from a simplified channel in which flow is driven by a head difference between inlet and outlet. This model is used to indicate that there is a maximum rate at which energy can be artificially extracted from the flowing water and that this rate is related to the kinetic energy flux in the unexploited channel but with a multiplying factor which is related to the channel physical properties. Counter intuitively, this multiplier can exceed unity in some circumstances. The simple channel has some similarities to tidal channels but is here presented as an abstraction to allow appreciation of the relationships between energy extraction, flow speed and channel properties.     

The economics of tidal energy

Concern over global climate change has led policy makers to accept the importance of reducing greenhouse gas emissions. This in turn has led to a large growth in clean renewable generation for electricity production. Much emphasis has been on wind generation as it is among the most advanced forms of renewable generation, however, its variable and relatively unpredictable nature result in increased challenges for electricity system operators. Tidal generation on the other hand is almost perfectly forecastable and as such may be a viable alternative to wind generation. This paper calculates the break-even capital cost for tidal generation on a real electricity system. An electricity market model is used to determine the impact of tidal generation on the operating schedules of the conventional units on the system and on the resulting cycling costs, emissions and fuel savings. It is found that for tidal generation to produce positive net benefits for the case study, the capital costs would have to be less than €510,000 per MW installed which is currently an unrealistically low capital cost. Thus, it is concluded that tidal generation is not a viable option for the case system at the present time.     

Tidal current energy resource assessment in Ireland: Current status and future update

Interest in renewable energy in Ireland has increased continually over the past decade. This interest is due primarily to security of supply issues and the effects of climate change. Ireland imports over 90% of its primary energy consumption, mostly in the form of fossil fuels. The exploitation of Ireland's vast indigenous renewable energy resources is required in order to reduce this over-dependence on fossil fuel imports to meet energy demand. Various targets have been set by the Irish government to incorporate renewable energy technologies into Ireland's energy market. As a result of these targets, the development in wind energy has increased substantially over the past decade; however this method of energy extraction is intermittent and unpredictable. Ireland has an excellent tidal current energy resource and the use of this resource will assist in the development of a sustainable energy future. Energy extraction using tidal current energy technologies offers a vast and predictable energy resource. This paper reviews the currently accepted tidal current energy resource assessment for Ireland. This assessment was compiled by Sustainable Energy Ireland in a report in 2004. The assessment employed a 2-dimensional numerical model of the tidal current velocities around Ireland, and from this numerical model the theoretical tidal current energy resource was identified. With the introduction of constraints and limitations, the technical, practical, accessible and viable tidal current energy resources were obtained. The paper discusses why the assessment needs updating including the effect on the assessment of the current stage of development of tidal current turbines and their deployment technology.     

江苏沿海潮差能和潮流能区域分布研究

文章采用东中国海二维潮波模型,基于2006年夏季大潮潮流数值的计算结果对江苏沿海潮差能和潮流能开展了区域分布研究。就潮差能而言,通过对比分析《江苏沿海功能区划》所拟定的3个潮汐电站站址(灌河口、射阳河口和长江口北支)所处的地理位置及相应的潮汐要素,发现灌河口站址自然条件相对较优,推荐采用单坝单向水库在该区域进行潮差能的开发。就潮流能而言,通过分析区域内潮流平均流速和椭圆图的分布特征,发现江苏沿海南部的小洋口地区和长江口南支的北港、南槽地区具有较好的潮流能开发利用潜力。     

National geodatabase of tidal stream power resource in USA

A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500 W/m² (corresponding to a current speed of ～1 m/s), total surface area larger than 0.5 km² and depth greater than 5 m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL).     

Water: A key resource in energy production

Water and energy are the key resources required for both economic and population growth, and yet both are increasingly scarce. The distribution of water takes large amounts of energy, while the production of energy requires large amounts of water in processes such as thermal plant cooling systems or raw materials extraction. This study analyzes the water needs for energy production in Spain according to the energy source sector (electricity, transportation or domestic) and process type (extraction and refining of raw materials or thermal plant use). Current and future water needs are quantified according to energy demand and technology mix evolution. Hypothetical scenarios that simulate the risks of promoting specific energy policies are also analyzed. Results show that the combination of energy resources used in Spain is projected to be more than 25% more water consumptive in 2030 than in 2005 under ceteris paribus conditions. Renewable energies are mixed in terms of their consequences on the water supply; wind power can reduce water withdrawal, while the biofuels production is a water-intensive process.     

Establishing perennial grass energy crops in the UK: A review of current propagation options for Miscanthus

A key UK government strategy is to expand the supply of home grown biomass and facilitate the development and competitiveness of a sustainable supply chain, while promoting low-carbon technology. Analysis of the potential supply chain suggests that this can, in part, be achieved by growing energy crops. Meeting expectations is, however, reliant on developing an economically viable biomass sector which incorporates efficient, sustainable and regional supply chains to increase biomass use.This review aims to present the knowledge by which plant propagules, for the biomass supply chain, can be produced at minimum cost. It specifically addresses the potential of biomass production from the perennial grass Miscanthus. This review is part of a project to identify the causes for the apparent limitations in the establishment of UK perennial energy crops. The work reported here focuses on the knowledge available regarding the potential routes by which Miscanthus material could be mass produced.The review concludes that high density plantings must be established to maximise yields. Vegetative clonal plant propagation is required to deliver uniform crops of selected germplasm. Commercial seed production in the UK is not possible and potentially undesirable for selected germplasm. Rhizome production and division is slow, but currently does not limit increases in production because the UK industry uptake is currently small. Uptake of new germplasm will be dependent on the use of rapid and cost effective plant propagation systems, particularly vegetative systems. The germplasm collection established provides an opportunity for genotypes to be propagated by a range of techniques to determine ease of propagation in terms of cost and multiplication rates. At present the establishment rate of Miscanthus is slow and this appears limited by economics; evidence suggests that the cost of plant propagules is one factor that constrains widespread planting. New techniques are required that simultaneously reduce unit costs of propagules and increase the speed of their availability to aid this developing industry.     

潮流水轮机的研究进展

概述了潮流水轮机的国内外发展情况,对3种不同结构的潮流水轮机的类型和特点作了比较分析,介绍了潮流水轮机的研究方法以及性能研究,指出了潮流水轮机的未来发展方向。     

A regional energy paradox—the case of Central Norway

Central Norway is expected to have a gap of 8 TWh in 2010 because of heavy investments in energy-intensive industries. The region has two landing sites for natural gas and a considerable potential for wind power to cover the gap. Small-scale hydropower and upgrading of existing hydropower plants also constitute a regional energy potential. Paradoxically, the most realistic investment prospect seems to be extensive investments in new transmission lines to cover the supply deficit. The aim of this paper is to present a problem of regional supply security and public intervention to illustrate and discuss the challenges of arriving at long-term capacity adequacy in deregulated electricity markets.     

A review of energy in Rwanda

During the last two decades, Rwanda has experienced an energy crisis mostly due to lack of investment in the energy sector. With the growing of the population and increasing industrialization in urban areas, energy provided by existing hydro and thermal power plants has been increasingly scarce with high energy costs, and energy instability. Furthermore, as wood fuel is the most important source of energy in Rwanda, the enduring dependence on it and fossil fuel consumption as well, will continue to impact on the process of environmental degradation. Rwanda is rich with abundant renewable energy resources such as methane gas in Lake Kivu, solar, biomass, geothermal; and wind energy resource is currently being explored. Recently, the Government has given priority to the extension of its national electrical grid through development of hydro power generation projects, and to rural energy through development of alternative energy projects for rural areas where access to national grid is still difficult. This paper presents a review of existing energy resources and energy applications in Rwanda. Recent developments on renewable energy are also presented.     

A decision model for energy resource selection in China

This paper evaluates coal, petroleum, natural gas, nuclear energy and renewable energy resources as energy alternatives for China through use of a hierarchical decision model. The results indicate that although coal is still the major preferred energy alternative, it is followed closely by renewable energy. The sensitivity analysis indicates that the most critical criterion for energy selection is the current energy infrastructure. A hierarchical decision model is used, and expert judgments are quantified, to evaluate the alternatives. Criteria used for the evaluations are availability, current energy infrastructure, price, safety, environmental impacts and social impacts.