Dynamic tidal power

Co-inventor Kees Hulsbergen presenting the principles of DTP at Tsinghua University in Beijing, in February 2010.

Dynamic tidal power or DTP is a new and untested method of tidal power generation. It would involve creating large dam-like structure extending from the coast straight to the ocean, with a perpendicular barrier at the far end, forming a large 'T' shape.

This long T-dam would interfere with coast-parallel oscillating tidal waves which run along the coasts of continental shelves, containing powerful hydraulic currents (common in e.g. China, Korea, and the UK).^[1][2][3][4]

The concept was invented and patented in 1997 by Dutch coastal engineers Kees Hulsbergen and Rob Steijn.^[5]

Description

Top-down view of a DTP dam. Blue and dark red colors indicate low and high tides, respectively.

A DTP dam is a long dam of 30 to 60 km which is built perpendicular to the coast, running straight out into the ocean, without enclosing an area. The horizontal acceleration of the tides is blocked by the dam. In many coastal areas the main tidal movement runs parallel to the coast: 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.

Benefits

A single dam can accommodate over 8 GW (8000 MW) of installed capacity, with a capacity factor of about 30%, for an estimated annual power production of each dam of about 23 billion kWh (83 PJ/yr).^[6] 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 3.4 million Europeans.^[7] If two dams are installed at the right distance from one another (about 200 km apart), they can complement one another to level the output (one dam is at full output when the other is not generating power). Dynamic tidal power doesn't require a very high natural tidal range, so more sites are available and the total availability of power is very high in countries with suitable conditions, such as Korea, China, and the UK (the total amount of available power in China is estimated at 80 - 150 GW).

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' 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 and the Afsluitdijk in the Netherlands. The interaction of tidal currents with natural peninsulas is also well-known, and such data is used to calibrate numerical models of tides. Formulas for the calculation of added mass were applied to develop an analytical model of DTP. Observed water level differentials closely match current analytical and numerical models.^[1] 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.

Challenges

A major challenge is that a demonstration project would yield almost no power, even at a dam length of 1 km or so, because the power generation capacity increases as the square of the dam length (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 30 km.

Other concerns include: shipping routes, marine ecology, sediments, and storm surges.

See also

• Marine energy

References

1. ^ ^{a b} K. Hulsbergen, R. Steijn, G. van Banning, G. Klopman (2008). "Dynamic Tidal Power – A new approach to exploit tides". 2nd International Conference on Ocean Energy. Brest, France. 
2. ^ Marieke Aarden (28 November 1998). "Getijdenkracht lift mee naar Schiphol in zee [Tidal power gets a free ride to Schiphol in the sea]" (in Dutch). Volkskrant. http://www.volkskrant.nl/archief_gratis/article782897.ece/Getijdenkracht_lift_mee_naar_Schiphol_in_zee. Retrieved 2010-04-15. 
3. ^ Rijkert Knoppers (16 January 1999). "Dertig kilometer electriciteit [Thirty kilometers of electricity]" (in Dutch). NRC Handelsblad. http://archief.nrc.nl/index.php/1999/Januari/16/Overig/57/Dertig+kilometer+electriciteit. Retrieved 2010-04-15. 
4. ^ Bas Keijts (1998). "Meer vermogen met eb en vloed [More power from low and high tides]" (in Dutch). Land en Water 12. 
5. ^ WO 9801670 
6. ^ "Ocean Energy EC Contractors Meeting". Bremerhaven, Germany. October 25, 2006. http://ec.europa.eu/research/energy/pdf/gp/gp_events/ocean_energy/0940_co-ordinated_action_on_ocean_energy_en.pdf. Retrieved 11 November 2010. 
7. ^ "Nuclear Power in France". http://www.world-nuclear.org/info/inf40.html.