法国目前潮汐电站的设计

一、前言本文旨在说明法国电力部和法国设计师对潮汐电站设计的一些想法。选用的研究方法是通过一个尽可能完整的设计项目,以论证其技术的可行性。在站址选择和工程布置上,重点放在考虑对环境的影响。二、站址选择潮汐电站可发出的电能和平均潮差的平方成正比。     

海洋潮流能资源的数值估算——以胶州湾口为例

在回顾国际上现有的潮流能资源估算方案基础上,提出利用三维潮流数值模式估算潮流能的思路,并在胶州湾进行了应用。基于普林斯顿海洋模式,建立了胶州湾潮汐潮流三维数值预报模型,对研究海区的潮汐和潮流做出了较为准确的模拟。数值模拟得到的胶州湾口最大可能潮流速度为2m/s,具有一定的潮流能开发潜力;湾口水道上多年平均潮流能蕴藏量为16MW,大潮期间的瞬时值和大潮周日平均值可分别达135和49MW.潮流资料时间序列的长度对潮流能储量的计算结果有较大影响。由于潮流现象具有强烈的时变性和多种周期,估算潮流能的平均储量应积累一年以上的资料为宜。研究表明,潮流数值模式能够提供高时空分辨率的三维潮流数据,有效弥补潮流实测资料稀缺的不足,因而可作为潮流能资源评价的有力工具。     

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。     

水平轴潮流能水轮机尾流特性研究

文章以水平轴潮流能水轮机为研究对象,采用CFD方法对水轮机的尾流特性进行分析。通过网格无关性验证与已发表文献的比对,验证了CFD方法的精度。通过不同叶尖速比下的水轮机性能曲线,进一步分析了水轮机的尾流场速度分布特征。通过分析尾流场中轴向、径向和切向速度的分布特点,研究了水平轴潮流能水轮机尾流的微观结构特征及其演化规律。研究结果表明:尾流横向影响范围在以中心轴线为中心的1D范围内;在近尾流处,尾流速度具有周期性,轴向速度随着尾流下移而逐渐减小;在尾流旋转过程中,径向速度向外扩散并逐渐衰减,切向速度分量沿轴向逐渐衰减。     

长江口盐差能发电站的选址

对盐差能发电技术在长江口的应用选址进行了探讨。详细分析了长江口各个主要汊道的盐度分布特点及在长江口建立盐差能发电站的可能性。分析表明,无论是洪季还是枯季,北港的盐度在所有汊道中最低,北支最高,而圆陀角附近汊道的盐度在北支中又是最高。因此,将发电站的位置选在圆陀角与北港之间的崇明岛区域上,发电后排出的微咸水排至接近口外的河底。此发电技术的应用既减小了河域生态系统受高含量氯化物盐水的影响,还减小了北支、南支及北港汊道沿岸水库的取水制约以及河域两岸居民用水限制。     

海水盐差能发电技术的试验研究

介绍了利用海水盐差能发电的三种主要方法：渗透压法、蒸汽压法和反电渗析电池法,建立了一套反电渗析电池试验装置,并对这种电池的电动势、电池内阻和海淡水隔室进行了理论研究和分析,设计了5种浓差电池试验槽,并取得了初步的试验结果和研究结论,为今后我国长江口和珠江口的海水盐差能发电应用提供了理论依据。     

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。     

阻塞比对潮流能水轮机尾流特性影响数值模拟研究

首先通过对比分析数值模拟结果与水槽实验尾流场速度数据,验证数值模拟的准确性。通过在软件STAR-CCM+中改变水槽宽度的模型,使水轮机阻塞比分别在9.8%、14.7%和29.5%的情况下进行模拟计算,分析潮流能水轮机尾流特性的变化。结果显示,阻塞比的变化不仅会改变水轮机扫略区域外流体速度,影响远尾流恢复速度,还会对尾流的旋转和湍动能分布造成影响;但随着槽宽增加阻塞比减小,其对尾流特性影响逐渐减弱。     

中山翠亨新区潮汐能资源评估研究

针对中山市翠亨新区构建绿色智能电网、积极推进新能源应用的电力工程专项规划,对辖区内的潮汐能资源进行评估研究。选取部分水域属于辖区的横门水道作为数据样本采集点,以横门站的潮位为参考依据来分析辖区内的潮汐资源。通过对2 a的潮位数据统计,获取年最大潮差和年平均潮差;采用傅里叶谱分析方法对潮位数据进行调和分析,确定潮汐类型;并采用理论公式分析横门水道潮汐能年理论储量;通过调节计算,得出翠亨新区拟建电站的潮汐能技术可开发资源量。     

海浪条件下水平轴叶片式潮流能水轮机流动特性的数值模拟

为了研究自由海浪条件下的高潮汐流速对水平轴潮流能水轮机的动态特性影响，基于STAR-CCM+建立了海浪条件下潮流能水轮机水动力特性的数值模拟方法，得到了海浪对潮流能水轮机转动影响规律及转动过程中产生的尾流特征。结果表明，潮流能水轮机角加速度的幅度与频率受海浪影响，但波动幅度小于海浪波动幅度、变化频率高于海浪波动频率；水轮机转动产生的尾流会使下一个水轮机的周围流场更紊乱，对叶片转动的影响、水轮机轴负载和能量利用率等方面会产生影响；压力脉动变化趋势分析认为，尾流对水轮机疲劳损伤并无太大影响。     

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 energy leasing and tidal phasing

In addition to technical and economic constraints, tidal energy leasing is generally governed by demand for sites which contain the highest tidal streams, and does not take into account the phase relationship (i.e. the time lag) between sites. Here, the outputs of a three-dimensional tidal model are analysed to demonstrate that there is minimal phase diversity among the high tidal stream regions of the NW European shelf seas. It is therefore possible, under the current leasing system, that the electricity produced by the first generation of tidal stream arrays will similarly be in phase. Extending the analysis to lower tidal stream regions, we demonstrate that these lower energy sites offer more potential for phase diversity, with a mean phase difference of 1.25 h, compared to the phase of high energy sites, and hence more scope for supplying firm power to the electricity grid. We therefore suggest that a state-led leasing strategy, favouring the development of sites which are complementary in phase, and not simply sites which experience the highest current speeds, would encourage a sustainable tidal energy industry.     

A techno-economic analysis of tidal energy technology

The choice of which type of electrical power generation technology to adopt is driven by a number of factors including: cost of generated electricity; responsiveness of generating plant to demand; security of supply/resource availability; environmental impact; and execution risk. Within these, tidal energy is unique as a renewable technology since it has the capability of providing predictable, firm power contributing to security of supply. This predictability gives tidal energy additional value in a future electricity market. Especially one where stochastic renewable technologies contribute to a sizable component of the power supplied; and where reserve capacity is required to maintain supply during periods of non-availability. In the shorter term, in order for tidal energy to gain commercial acceptance, tidal technologies under development need to produce electricity at a competitive price. This paper examines the drivers influencing electricity pricing; current tidal energy developments, aimed at reducing capital costs; and bench-mark these against offshore wind.     

潮流能的利用及研究状况

介绍了潮流能机组发电技术原理,详述了国内外潮流能发电技术的研究状况及应用情况。     

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.     

The energy gains realisable through pumping for tidal range energy schemes

Some previous work has made optimistic claims about the potential energy gains that could be made by using pumping with tidal range structures (barrages, lagoons and offshore tidal impoundments). This paper explores the factors influencing whether such gains can be realised for positive head pumping (pumping once water levels have equalised), using 0-D modelling concepts.     

Laboratory-scale simulation of energy extraction from tidal currents

The energy available from tidal currents is substantial and considerable work has been conducted into determining the size of the resource and what the large-scale consequences of extraction might be. This paper describes the work conducted to establish a laboratory-scale model, by using the commercial computational fluid dynamics (CFD) code FLUENT™, in order to predict local-flow consequences resulting from the extraction of energy in two and three dimensions from within the water column in a tidal flow. As might be expected, a wake is formed but there is considerable localized flow acceleration around and, most especially, under an extraction zone. The wake behind the device is shown to be associated with a drop in the free surface which, in turn, is associated with the decline in the wake itself.     

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.