Dynamic tidal power or DTP is an untried but promising technology for

tidal power Tidal power or tidal energy is harnessed by converting energy from tides into useful forms of power, mainly electricity using various methods. Although not yet widely used, tidal energy has the potential for future electricity generation. T ...

generation. It would involve creating a long

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

-like structure perpendicular to the coast, with the option for a coast-parallel barrier at the far end, forming a large 'T' shape. This long T-dam would interfere with coast-parallel tidal wave hydrodynamics, creating water level differences on opposite sides of the barrier which drive a series of bi-directional

turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical ...

s installed in the dam. Oscillating tidal waves which run along the coasts of continental shelves, containing powerful

hydraulic Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...

currents, are common in ''e.g.''

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

Korea Korea is a peninsular region in East Asia consisting of the Korean Peninsula, Jeju Island, and smaller islands. Since the end of World War II in 1945, it has been politically Division of Korea, divided at or near the 38th parallel north, 3 ...

, and the UK. The concept was invented and patented in 1997 by Dutch coastal engineers Kees Hulsbergen and Rob Steijn. A short video explaining the concept was completed in October 2013 and made available in English on YouTube and in Chinese on Youku.

Description

A DTP dam is a long barrier of 30 km or more which is built perpendicular to the coast, running straight out into the sea, without enclosing an area. Along many coasts of the world, the main tidal movement runs parallel to the coastline: the entire mass of the ocean water accelerates in one direction, and later in the day back the other way. A DTP dam is long enough to exert an influence on the horizontal tidal movement, which generates a water level differential (head) over both sides of the dam. The head can be converted into power, using a long series of conventional low-head turbines installed in the dam.

Maximum head difference

Estimates of the maximum head difference that can be obtained from a variety of dam configurations are based on numerical and analytical models. Field information from measured water level differences across natural barriers confirms the creation of significant head. The (maximum) head difference is more than what would be expected in stationary flow situations (such as rivers). The maximum head difference reaches values up to a few meters, which can be attributed to the non-permanent character of the tidal flow (acceleration).

Benefits

High power output

It is estimated that some of the largest dams could accommodate over 15 GW (15,000 MW) of installed capacity. A DTP dam with 8 GW installed capacity and a capacity factor of about 30%, could generate about 21 TWh annually. To put this number in perspective, an average European person consumes about 6800 kWh per year, so one DTP dam could supply energy for about 3 million Europeans.

Stable power

The generation of tidal power is highly predictable due to the deterministic nature of tides, and independent of weather conditions or climate change. Power output varies with the tidal phase (ebb & flow, neap & spring) but the shorter terms effects can be avoided by combining two dams, placed at certain distance from each other (in the order of 150–250 km), each generating maximum electricity output when the other is generating minimal output. This provides a predictable and fairly stable base generation to the energy grid.

High availability

Dynamic tidal power does not require a very high natural

tidal range Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's prog ...

, but instead an open coast where the tidal propagation is alongshore. Such tidal conditions can be found in many places around the world, which means that the theoretical potential of DTP is very high. Along the Chinese coast for example, the total amount of available power is estimated at 80–150 GW.

Potential for combined functions

The long dam can be combined with various other functions, such as coastal protection, deep sea – and LNG ports, aquaculture facilities, controlled land reclamation and connections between islands and the mainland. These additional functions can share the investment costs, thus helping to lower the price per kWh.

Challenges

A major challenge is that the proof of DTP functioning can only be demonstrated by putting it in practice. Testing the concept of DTP at a small scale within a demonstration project, would not be effective, since almost no power would be yielded. Not even at a dam length of or so, because the DTP principle is such that the power generation capacity increases as the square of the dam length increases (both head and volume increase in a more or less linear manner for increased dam length, resulting in a quadratic increase in power generation). Economic viability is estimated to be reached for dam lengths of about .

Demonstration project

A demonstration project under consideration in China would not involve construction of a dam, but instead feature a newly cut channel through a long peninsula with a narrow

isthmus An isthmus (; : isthmuses or isthmi) is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea count ...

(neck). The channel would feature a head of about , and be fitted with low-head bi-directional turbines, similar to the type which would be used for full-scale DTP.

Status of technological development

No DTP dam has ever been built, although all of the technologies required to build a DTP dam are available. Various mathematical and physical models have been conducted to model and predict the '

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple ani ...

' or water level differential over a dynamic tidal power dam. The interaction between tides and long dams has been observed and recorded in large engineering projects, such as the

Delta Works The Delta Works () is a series of construction projects in the southwest of the Netherlands to protect a large area of land around the Rhine–Meuse–Scheldt delta from the sea. Constructed between 1954 and 1997, the works consist of dams, slu ...

and the

Afsluitdijk The Afsluitdijk (; ; "closure dyke") is a major dam and causeway in the Netherlands. It was constructed between 1927 and 1932 and runs from Den Oever in North Holland province to the village of Zurich, Friesland, Zurich in Friesland province, o ...

in the

Netherlands , Terminology of the Low Countries, informally Holland, is a country in Northwestern Europe, with Caribbean Netherlands, overseas territories in the Caribbean. It is the largest of the four constituent countries of the Kingdom of the Nether ...

. The interaction of tidal currents with natural

peninsula A peninsula is a landform that extends from a mainland and is only connected to land on one side. Peninsulas exist on each continent. The largest peninsula in the world is the Arabian Peninsula. Etymology The word ''peninsula'' derives , . T ...

s is also well-known, and such data is used to calibrate numerical models of tides. Formulas for the calculation of

added mass In fluid mechanics, added mass or virtual mass is the inertia added to a system because an accelerating or decelerating body must move (or deflect) some volume of surrounding fluid as it moves through it. Added mass is a common issue because the ob ...

were applied to develop an analytical model of DTP. Observed water level differentials closely match current analytical and numerical models. Water level differential generated over a DTP dam can now be predicted with a useful degree of accuracy. Some of the key elements required include: * Bi-directional turbines (capable of generating power in both directions) for low head, high-volume environments. Operational units exist for seawater applications, reaching an efficiency of over 75%. * Dam construction methods. This could be achieved by modular floating caissons (concrete building blocks). These caissons would be manufactured on shore and subsequently floated to the dam location. * Suitable sites to demonstrate DTP. A pilot project of DTP could be integrated with a planned coastal development project, such as a sea bridge, island connection, deep sea port, land reclamation, offshore wind farm, etc., built in a suitable environment for DTP.

Recent progress

In December 2011 the Dutch Ministry of Economy, Agriculture and Innovation (EL&I) awarded a grant funding subsidy to the POWER consortium, led by Strukton and managed by ARCADIS. The maximum grant is about 930.000 euro, which is matched by a similar amount of co-financing from the consortium partners. The POWER group conducts a detailed feasibility study on the development of Dynamic Tidal Power (DTP) in China in a three-year programme jointly conducted with Chinese government institutes. The commitments of the programme to achieve by 2015, registered under the UN Sustainable Energy for All initiative include: * Determine most suitable sites for DTP implementation in China, Korea, and the UK * Complete detailed feasibility studies for two DTP pilot power plants in China * Complete pre-feasibility study for one full-scale DTP power plant in China * Worldwide dissemination of technical information regarding DTP among relevant target groups In August 2012, China's National Energy Administration formed a consortium of companies and research institutes, led by the Hydropower and Water Resources Planning and Design General Institute (also known as China Renewable Energy Engineering Institute), to investigate DTP. A bilateral agreement on DTP cooperation was signed between China and the Netherlands on September 27, 2012. Following technical exchange to verify the principles, a modelling study was conducted to select sites. In October 2013, a more in-depth economic analysis study was started to better understand the economic costs and benefits of DTP. A short video explaining the concept was completed in October 2013 and made available in English on YouTube and in Chinese on Youku.

References

{{Reflist, 2

External links

Benefits of Tidal Power
Tidal power