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Tidal Stream Energy in China

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Jinhai Zheng
Jinhai Zheng
Jinhai Zheng
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Peng Dai at Hohai University
Peng Dai
Jisheng Zhang at Hohai University
Jisheng Zhang
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In the recent decades, many efforts have been made by the coastal scientists and engineers for the explosion of tidal stream energy in China, as tidal stream energy is considered as one of most promising resources of marine renewable energy. Meanwhile, tidal stream energy is easy for predication and its utilization has less harm to the environment. The tidal stream energy in China could theoretically supply more than 8.2 GW, and most of them come from Zhoushan Islands, Zhejiang Province. The government of China largely invests the explosion of tidal stream energy in these years, and a significant progress has been achieved in this area. Tidal stream turbines are especially designed to improve the utilization efficiency of tidal stream energy with low impact on marine environment, and some demonstration projects of tidal stream energy are currently under plan along the coast. This study is to provide a comprehensive overview of tidal stream energy in China, including the potential assessment of energy resource, development history (achievement and difficulties) of tidal stream turbines, progress and challenges of the undergoing demonstration project, and future plan and suggestions for developing tidal stream farm in China.
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Procedia Engineering 116 ( 2015 ) 880 – 887
1877-7058 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer- Review under responsibility of organizing committee , IIT Madras , and International Steering Committee of APAC 2015
doi: 10.1016/j.proeng.2015.08.377
ScienceDirect
Available online at www.sciencedirect.com
8th International Conference on Asian and Pacific Coasts(APAC 2015)
Department of Ocean Engineering, IIT Madras, India.
Tidal stream energy in China
Jinhai Zheng
a,b
, Peng Dai
b
, Jisheng Zhang
a,b,
*
a
State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing 210098, China
b
College of Harbour, Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China
Abstract
In the recent decades, many efforts have been made by the coastal scientists and engineers for the explosion of
tidal stream energy in China, as tidal stream energy is considered as one of most promising resources of marine
renewable energy. Meanwhile, tidal stream energy is easy for predication and its utilization has less harm to the
environment. The tidal stream energy in China could theoretically supply more than 8.2 GW, and most of them
come from Zhoushan Islands, Zhejiang Province. The government of China largely invests the explosion of tidal
stream energy in these years, and a significant progress has been achieved in this area. Tidal stream turbines are
especially designed to improve the utilization efficiency of tidal stream energy with low impact on marine
environment, and some demonstration projects of tidal stream energy are currently under plan along the coast. This
study is to provide a comprehensive overview of tidal stream energy in China, including the potential assessment
of energy resource, development history (achievement and difficulties) of tidal stream turbines, progress and
challenges of the undergoing demonstration project, and future plan and suggestions for developing tidal stream
farm in China.
© 2014 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of organizing committee of APAC 2015, Department of Ocean Engineering, IIT Madras.
Keyword:tidal stream energy; overview; energy resource; converter
* Corresponding author. Tel: +86-25-8378-6619.
E-mail address: jszhang@hhu.edu.cn
© 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/).
Peer- Review under responsibility of organizing committee , IIT Madras , and International Steering Committee of APAC 2015
881
Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
1. Introduction
Marine energy is one of the most promising renewable (Bahaj, 2011; Charliew, 2008; Johnstone, 2006), among
which Tidal energy gains its population by its regularity and predictability. Tidal energy can be predicted with high
accuracy in both short and long terms, and therefore the power output of a certain tidal plant at a given location can
also be accurately forecasted. There are two different ways to harness the tidal energy, a tidal barrage system so as
to impound water and then use its potential energy (Xia, 2010a,b) and by using the tidal stream itself to drive the
tidal energy converters (Carballo, 2009; Blunden, 2006; Bahaj, 2004). The tidal stream energy has two advantages
over the tidal barrage system, i.e. lower environmental cost and lower capital investment, which are both due to the
non-utilization of the barrage. Relative to the wind energy, the power density available for marine current energy
converters will generally be much higher than that for wind energy converters at appropriately rated speeds for both
technologies –a result of the much higher density of water (Bahaj, 2003). The challenge for the tidal stream energy
is in terms of enhancing the reliability and stability of the energy converters.
China is one of the most active economy across the world. The rapid growth of the industry and people’s
increasing demand for environment protection has laid pressure on China. China borders four marginal seas of the
Pacific, i.e. the Bohai sea, the Yellow sea, the East China Sea and the South China Sea. These areas are rich in islands
and channels where the maximum tidal current velocity could exceed 2 m/s which are thought to be the acceptable
electricity-generating speed for tidal current turbines. This provides great probability to harness the tidal stream
energy. Actions are taken from both the government and the academy side. The Renewable Energy Law went into
effect on 1st January, followed by the middle and long term development program of the renewable energy which
was published in 2007. The Harbin Engineering University has started the research on the vertical axis tidal turbine
device since 1980s. Scholars from the Zhengjiang University, Ocean University of China, the NorthEast Normal
Univerisity and Hohai University also show their dedicated enthusiasm to the development of tidal current energy.
The purpose of this study is to give an overview of the distribution and assessment of tidal current as well as the
present stage of development of tidal current turbine technology in China.
2. Tidal energy resources
Tidal energy is the energy dissipated by tidal movements, which derives directly from the gravitational and
centrifugal forces between the earth, moon and sun (Owen, 2008). Most of the tides occur twice one lunar day due
to the gravitational attraction exerted by the moon upon the earth and the centrifugal force of the rotation of the
moon-earth system. This is called the semi-diurnal tide. The moon orbits the earth every 29.5 days, known as the
lunar cycle, causing the tides vary in size between spring tides and neap tides. Spring tides occur when the sun and
moon line up with the earth, whether pulling on the same side of the earth or on opposite side, resulting in very high
spring tides. Neap tides occur when the sun and moon are at 90 degrees to each other, resulting in low neap tides
(Rourke, 2010; Charliew, 2003; Clark, 2007). In parallel with the water level rising and falling, the tidal current
moves in and out as flood and ebb currents, which is the tidal stream energy harnessing aims at.
The evaluation of the tidal energy resource is the first step to harvest the tidal energy. Four national surveys of
the tidal currents energy have been conducted since the middle of the last century. It was due to 1958 that the first
exploitation of tidal energy was carried out, followed by numerous small tidal barrage power plants. Unfortunately
most of the plants failed due to the inappropriate design and operation (Wang, 2009). The second survey started in
1978 organized by State Oceanic Administration and Ministry of Resources and Electric Power. The investigation
and design institutes in nine coastal provinces are involved in this survey. 156 bays and 33 estuaries were investigated
in terms of its tidal energy (Wang, 1989). The third survey, which was accounted for tidal stream energy, tidal
potential energy and wave energy, was performed in 1986. In 2004, the Investigation and Assessment of China
Offshore Resources, namely 908 Special, was organized by the State Oceanic Administration of China. This survey
was featured by the comprehensiveness in terms of ocean renewable energy resources.
882 Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
Fig. 1 Depth-averaged current velocity in Bohai Sea and East China Sea.
Fig. 2Depth-averaged current velocity in South China Sea.
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Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
It is reported that when the maximum velocity exceeds 2 m/s, 20000 kWh can be generated per unit square meters
(Black & Veatch Consulting, 2004). Based on the earlier survey, the theoretical value of mean power for China tidal
stream energy is 8.2 GW, among which the East China Sea, the Yellow Sea, the South China Sea accounts for 6.45
GW, 1.35 GW and 0.4GW, or 78.6%, 16.5% and 4.9% of the total output power, respectively. Liaoning province,
Shandong province, Zhejiang province, Fujian province, Taiwan are all rich in tidal stream energy resources, where
the energy flux density varies from 10 kW/m2to 30 kW/m2, extremely large Jintan channel, Guishan channel, Xihou
channel in the Zhoushan archipelago.
The field data was used to calculate the energy resource around Zhoushan, which yielded a value of 64300 kW.
Wang (2009) used the Farm method and the Flux method to evaluate the tidal stream energy in Gaoting channel and
Guanmen channel. According to different method, the results vary from 4.67 MW to 5.31 MW for Gaoting channel,
from 7.92 MW to 9.73 MW for Guanmen channel.
Numerical results showed that the maximum flow exceeded 2.5 m/s in spring tide and more than 2.3 m/s in neap
tide for Chenshantou Shandong province. It yielded an average energy density of 0.7 Kw/m2. The tidal energy in
Jiaozhou bay was also studied by POM model, the maximum velocity was around 2m/s with a great potential to
harness the tidal stream energy. The extractable energy is expected to be 3.2MW.
There are many islands and channels in Bohai Bay, such as the Laotieshan channel, Qinshan channel, where the
maximum current speed ranges from 3.6 m/s to 4.2 m/s. The channels here are featured by its wideness and
shallowness, which is favored by the turbine installation and operation. It is reported that the average energy density
is more than 500 W/m2.
In Xiamen bay,the Jinmen northeast channel has the largest tidal current with the maximum velocity of 2.2 m/s
and average velocity of 1.6m/s.
3. Tidal energy converters
Harbin Engineering University (HEU) triggered their research on vertical tidal turbine in 1980s.Numerous
laboratory experiments has been carried out, these experiments aim at 1) analyze the relation between the power
coefficient and several parameters including the tip speed ratio, chord length, diameter of the turbine etc. 2) provide
reference for the prototype design. Following these experiments, “WanXiang I”, “WangXiang II” and “Hai Neng I”
were installed and tested around Daishan waters Zhejiang province (see Figure 3). “WanXiang I” is a floating tidal
stream power station based on the cycloid type controllable-pitch vertical axis turbine with a rated power of 70 kW.
“WangXiang II” is a seabed-mounted tidal power station with a rated power of 40 kW. “Hai Neng I” has a rated
power of 300 kW (Jing, 2014).
Zhejiang University (ZJU) investigated a horizontal axis turbine, a sea trial of 5 kW horizontal-axis turbine which
was tested in April 2006, followed by a 25kW device tested in May 2009. The latter one generated a peak power of
30 kW at a water speed of 2.4m/s (Li, 2008). It has good self-starting characteristics and can start rotating at 1.37m/s
(see Figure 4). The results suggest that the total system efficiency is around 25% (Ma, 2010; Liu, 2011).
Ocean University of China (OUC) started studies of tidal current energy with a grant from the “863” Programme
in 2006. They also focused on the vertical-axis turbine, which is featured by the flexible vanes. This novel design
has some advantages such as light weighted, simple structure and easy maintaining. The laboratory experiments
indicated that the flexible vanes have some elegant performance. In 2008, the first demonstration system, a floating,
moored platform that holds a fexible vane turbine with a rated power of 5kW was tested around Zhaitang Island
Channel Shandong province (see Figure 5). The test gives out the expected results.
Northeast Normal University (NENU) developed a horizontal-axis turbine supported by National High
Technology Research and Development Program (“863” Program). A 2 kW device was tested in the coastal area of
Qingdao (Zhu, 2012), as shown in Fig. 6.
884 Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
Fig. 3 a) “WangXiang I” tidal power station b) “WangXiang II” tidal power station
Fig 4ZJU horizontal-axis turbine
Fig 5 OUC flexible van turbine
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Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
Fig. 6 NENU horizontal-axis turbine.
4. Tidal energy demonstration project
Anumber of demonstration projects are under plan. Two tidal stream devices are installed in parallel with the
Daishan Wind Farm project in 2011. The two devices are horizontal-axis turbines with the rated power of 60kW and
100kW. Another two tidal stream energy converters are installed with Pingtan Daliandao Wind Farm project. The
devices are horizontal-axis turbines with rated power of 100kW. While these two cases are stand-alone projects, the
national tidal stream energy test center is also on its coming path, at the stage of preliminary design and investment.
The preliminary site was selected between Putou Island and Hulu Island of Zhengjiang province. The water depth of
this tidal channel is around 30~70 m. The installed capacity will be more than 1MW from an array of tidal stream
turbines.
5. Challenges and advices
China’s energy consumption is increasing quickly in the last decade. Statistics shows that the total commercial
primary energy consumption was 2247 Million ton of coal equivalent (Mtce) in 2005, about 62% above 2000 levels,
or an average of 10.15% per year (China National Development and Reform Commission, 2007). The fossil fuel
accounts for the majority of the energy supply. Unfortunately the fossil fuel is non-renewable and emits greenhouse
gases which is the primary cause of climate change. To meet the energy demand and reduce the heavy dependence
on fossil fuel, the tidal stream energy providesone of the solutions. But to be honest, the present status of tidal stream
energy is far from extracting in a large scale in China. Research and development on tidal current energy is urgently
needed in terms of:
Assessment of the tidal energy should be updated. The previous assessment missed some of the ideal
locations such as the Zhaitang island where the OUC device was tested. These sites may have a large amount
of energy in potential. The renewed evaluation of the national tidal stream energy resource should cover all
the coastal and remote bays, channels and islands using the more accurate assessing methodology.
The extractable tidal stream energy is remote from land. The environment in these areasis harsh, and the
reliability of the tidal stream device is of great concern.
Novel tidal current turbines should be developed. Since the first prototype turbine was tested in 2002, the
rated power of the devices is of the order of 100 kW, which is far from commercial utilization.
International cooperation could enhance the development of tidal turbine device in China. The Europe starts
a base, i.e. the European Marine Energy Centre, for worldwide institutes and universities to test and develop
their ocean renewable devices including tidal stream energy.
886 Jinhai Zheng et al. / Procedia Engineering 116 ( 2015 ) 880 – 887
Support from the government should be emphasized regarding the funding, policy and regulations. Tidal
stream energy is present at its infant stage. It is not economically competitive with the traditional fossil fuel.
But accounts for its various attractive features, viz. high power density, predictability, abundant energy in
potential, it will certainly play a significant role in future energy consumption.
Besides the above mentioned items, there are certainly other issues including the cost effectiveness, environmental
impact that should be addressed before any definite conclusion can be drawn.
6. Conclusions
More and more people have recognized the importance of the renewable energy, the vast coastal and offshore
areas contributes one of renewable resources, i.e. the tidal stream energy, to the entire energy consumption. This
paper presents the distribution of China tidal resource, the status of the tidal turbines and the tidal stream
demonstration project. China has an excellent tidal current energy resource with a capacity of approximate 8.2 GW.
As the number of institution and researchers involved in the tidal stream energy increased, people can expect that the
vast amount of energy could be utilized in the future.
Acknowledgments
The authors are grateful to financial supports from the marine renewable energy research project of State Oceanic
Administration (GHME2013GC03),the National Natural Science Foundation of China (51479053,51137002,
51306103)and the Fundamental Research Funds for the Central University, China (2014B05114),
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  • Jul 2010
  • RENEW ENERG
The Severn Estuary has a spring tidal range approaching 14 m, which is among the highest tides in the world. Various proposals have been made regarding the construction of a tidal barrage across the estuary to enable tidal energy to be generated. The aim of the current study is to investigate the impact of constructing a tidal barrage on the hydrodynamic processes in the Severn Estuary using a numerical model. A two-dimensional hydrodynamic model based on an unstructured triangular mesh has been used in this study. The model employs a TVD finite volume method to solve the 2D shallow water equations, with the numerical scheme being second-order accurate in both time and space. The model has been calibrated by comparing model predictions with observed tidal levels and currents at different sites, for typical spring and neap tides, and it has also been verified using tidal level time series at four tide gauging stations measured in 2003. In order to predict the hydrodynamic processes with a barrage, the model domain was divided into two subdomains: one each side of the barrage. Details were given of the method used for representing the various hydraulic structures, including the sluices and turbines, along the proposed Cardiff-Weston barrage. The impact of constructing the barrage on the water levels and velocities was then investigated using this model. Model-predicted hydrodynamic parameters, without and with the barrage, were analysed in detail. Model predictions indicated that with the barrage the mean power output could reach 2.0 GW with up to 25 GWh units of electricity being generated over a typical mean spring tidal cycle. At some cross-sections, the maximum discharges were predicted to decrease by 30–50%, as compared with the corresponding discharges predicted without the barrage. The model also predicted that with the barrage, the maximum water levels upstream of the barrage would decrease by 0.5–1.5 m, and with the peak tidal currents also being reduced considerably. For different operating modes, complex velocity fields were predicted to occur in the vicinity of the barrage.
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Elements of tidal-electric engineering
Book
  • Jan 2007
As interest in tidal-electric power generation continues to grow in response to demands for renewable sources of energy, readers can now turn to Elements of Tidal-Electric Engineering for the first comprehensive treatment of the subject. The author, Robert H. Clark, a leader in the field for almost fifty years, has spearheaded several important research projects and consulted with governments and private industries around the world on tidal-electric issues. The focus of this text is the feasibility study. Power engineers gain both the knowledge and the skills needed to accurately determine the feasibility of a proposed tidal power development plan, including: • Major factors to consider in selecting a site for preliminary assessment • Tidal power schemes and mode • Hydraulic and mathematical models of estuaries to predict the estuary’s response to physical changes and the effects caused by operation of the proposed plant • Civil works required for tidal power development and the associated tidal generating equipment • Procedures to optimize plant output • Economic evaluation and risk assessment • Environmental impact of proposed construction and operation The book ends with an examination of commercially operating plants and a brief review of sites that have been the subject of investigation in the last half century. References and bibliographies direct readers to primary source material for further study. Until publication of this text, power engineers have had to rely on random journal articles and anecdotal information to perform a feasibility investigation. With the publication of Elements of Tidal-Electric Engineering these engineers have a single, integrated source that methodically covers all the issues. © 2007 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved.
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Rotor simulation research of horizontal axis marine current turbine
Article
  • Aug 2016
To reduce the test cost of horizontal axis marine current turbines(HAMCT) in ocean or water channel, a HAMCT rotor simulator was studied in laboratory. The output characteristics of the rotor were analyzed using blade element momentum(BEM) theory, the Bladed model of scale prototype turbine was established, and the output characteristics of the rotor of turbine model were obtained by simulation. A rotor simulation method was proposed based on asynchronous machine torque and q-axis current double closed-loop control of PLC controller. The test platform in laboratory was built to verify the feasibility of the rotor simulator of turbine model. The test results show that the rotor simulator can track the target torque well when the current speed is lower or higher than the rated speed, which provides convenience for rotor simulation of HATCT in laboratory. © 2016, Editorial Board of Acta Energiae Solaris Sinica. All right reserved.
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A 25 kW stand-alone horizontal axis tidal current turbine
Article
  • Jul 2010
Based on the analysis of the tidal current turbine's characteristics, a 25 kW stand-alone horizontal axis tidal current turbine is designed. The prototype consists of an optimally designed energy capture device, a split-power mechanical driving unit, and an electrical control system with a battery bank. Digital simulations are conducted to predict the system's working performance, based on the theoretical prediction of the turbine performance and the model analysis of the electro-mechanical system. The sea trial results show that the prototype system runs stably in the actual sea conditions and the maximum power generation reaches the designed power rating. The results clearly verify the effectiveness of the system. The prototype system can be used as a stand-alone power generation device to supply electricity for the users in island area.
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Study on the key technologies of horizontal axis surface tidal current generating
Article
  • Jun 2012
Utilization tidal current energy of sea surface to generate power is a hot topic of exploitation and utilization of marine energy. The characteristics, existing problems and state quo of tidal current energy exploitation in China were analyzed and the key of tidal current generator was proposed. Based on experiment method of cistern scale modeling, a set of 2 kW horizontal-axis direct-drive tidal current generator was designed to verified the feasibility of using the device to solve the key technical program. The test data and results show that horizontal-axis direct-drive surface tidal current generator is relative high efficiency and reliable. It provides technological foundation for the large-scale promotion and application of tidal current energy in the future.
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Ocean energy: Tide and tidal power
Book
  • Jan 2009
Engineers' dreams and fossil energy replacement schemes can come true. Man has been tapping the energy of the sea to provide power for his industries for centuries. Tidal energy combined with that of waves and marine winds rank among those most successfully put the work. Large scale plants are capital intensive but smaller ones, particularly built in China, have proven profitable. Since the initiation of the St Malo project in France, similar projects have gone into active service where methods have been devised to cut down on costs, new types of turbines developed and cost competitiveness considerably improved. Tidal power has enormous potential. The book reviews recent progress in extracting power from the ocean, surveys the history of tidal power harnessing and updates a prior publication by the author. © Springer-Verlag Berlin Heidelberg 2009. All rights are reserved.
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Tidal Current Energy. Origins and Challenges.
Article
  • Dec 2013
This chapter introduces the forces that drive the tidal currents, the external variables that modify their behaviour and outlines the challenges faced by engineers in exploiting this worldwide resource.With the transfer of corporate ownership of the leading UK devices in recent years it can no longer be argued that the position of the United Kingdom as the global leader in research and development in this field still holds. The race for the largest device instead of simple, reliable, robustness has failed the economic and business development test; tidal devices are too complex and, as yet, show no clear investment benefit.In addition, understanding of the potentially damaging coherent turbulence that exists within the flow is still very poor, and very few robust and cost-effective installation methodologies have been developed. Both of these issues are fundamental to the business case and should have been developed alongside the turbines, but have been treated as a design afterthought.This chapter discusses the range of factors that affect tidal current behaviour, the existence of unpredictability within a highly predictable system and the basic difficulties of cost-effective anchorage and fixing.
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Generating electricity from the oceans
Article
  • Sep 2011
  • RENEW SUST ENERG REV
Ocean energy has many forms, encompassing tides, surface waves, ocean circulation, salinity and thermal gradients. This paper will considers two of these, namely those found in the kinetic energy resource in tidal streams or marine currents, driven by gravitational effects, and the resources in wind-driven waves, derived ultimately from solar energy. There is growing interest around the world in the utilisation of wave energy and marine currents (tidal stream) for the generation of electrical power. Marine currents are predictable and could be utilised without the need for barrages and the impounding of water, whilst wave energy is inherently less predictable, being a consequence of wind energy. The conversion of these resources into sustainable electrical power offers immense opportunities to nations endowed with such resources and this work is partially aimed at addressing such prospects. The research presented conveys the current status of wave and marine current energy conversion technologies addressing issues related to their infancy (only a handful being at the commercial prototype stage) as compared to others such offshore wind. The work establishes a step-by-step approach that could be used in technology and project development, depicting results based on experimental and field observations on device fundamentals, modelling approaches, project development issues. It includes analysis of the various pathways and approaches needed for technology and device or converter deployment issues. As most technology developments are currently UK based, the paper also discusses the UK's financial mechanisms available to support this area of renewable energy, highlighting the needed economic approaches in technology development phases. Examination of future prospects for wave and marine current ocean energy technologies are also discussed
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Experimental research on tidal current vertical axis turbine with variable-pitch blades
Article
  • Sep 2014
  • OCEAN ENG
Due to the limited storage and ever-increasing dependence on fossil fuel, the world is in the phase of shifting toward renewable energy. Tidal current energy is one of the most predictable forms of renewable energy, which is harnessed by utilizing a tidal current turbine. To study the performance of the tidal current turbine relating to the ability of energy absorption and exchanging, experimental tests play an important role which can not only validate the numerical results but also provide a reference for the prototype design. In this study, a series of experiments related to vertical-axis turbines (VAT) were carried out at Harbin Engineering University and a large quantity of experimental data to study the hydrodynamic performance of turbines was presented. Based on the different techniques used to control the pitch mechanism, the experiments can be classified as the cycloid type controllable-pitch, spring-control pitch and passive variable-pitch VAT experiment. The influences of the different parameters on the hydrodynamic performance of turbines were discussed. Finally, some control strategies for the blade for different turbines were given.
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Sustainable co-generation from the tides: A review
Article
  • Jun 2003
  • RENEW SUST ENERG REV
The article discusses the sustainable co-generation from the tides. The tide-generating forces encompass the gravitational pull of principally sun and moon and the rotational force of the earth. The gravitational attraction exerted by the moon upon the earth and an inertial effect are the primary causes of the tides.
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