Dynamic tidal power or DTP is an untried but promising technology for tidal power generation. It would involve creating a long dam-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 turbines installed in the dam. Oscillating tidal waves which run along the coasts of continental shelves, containing powerful hydraulic currents, are common in e.g. China, Korea, 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, 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 .