New research supports the huge potential of tidal power
January 18, 2013
Artist’s impression of a tidal turbine array (credit: Phil. Trans. R. Soc)
A global group of scientists and engineers, including from the University of Southampton, has published in a special issue journal of the Royal Society in support of tidal power, which has the potential to provide more than 20 per cent of the UK’s electricity demand, they calculate.
While the predictable nature of tides makes them an ideal renewable energy source, more so than wind, the ability to effectively harness energy from the tides has proved elusive.
“The energy present in marine currents can be converted using technologies not too dissimilar to those used in wind energy. While technologies harnessing energy from the tides and currents have been discussed for many years, it is evident from recent deployment of single devices at megawatt scale that real progress has been achieved in a very short period of time, said AbuBakr Bahaj, Professor of Sustainable Energy at the University of Southampton and editor and contributor to the special issue.
“In essence, experience with single machines at such a power capacity will make progress to deployment of multiple machines to convert the marine energy resource much faster than that achieved at the start of the wind energy industry.”
However, the technology is presently still in a commercial prototype phase and only a handful of devices have so far been tested at full scale in the ocean. Unlike wind energy, there are currently various designs being promoted, with no single device design emerging as a winner so far.
How to tap tides
TGL 500-kW tidal flow turbine (credit: MeyGen)
Engineers try to tap tides in two ways: one involves building barrages across tidal estuaries that use tidal differences in sea surface elevation, so that the flowing waters turn turbines in a similar fashion as hydropower installations.
The other method involves placing turbines underwater in areas of the sea where fast flowing tidal streams, such as those found in coastal waters around the Channel Islands and Scotland.
The technology could be similar to the three bladed turbines used in wind energy with the flowing waters replacing air. Developing power from offshore tidal streams is fraught with difficulty, but according to the authors of the latest research, 2013 could see a big breakthrough in tidal stream power.
There are several companies planning to deploy arrays of tidal turbines in UK waters. For example MeyGen is planning to deploy tidal stream technology in Scotland’s Pentland Firth that will initially generate up to 40MW of electricity, enough to power about 38,000 homes.
“This is a crucial milestone for technology development and deployment. Currently, it appears this will be the first deployment of an array of tidal stream turbines,” says Professor Bahaj. “Such deployment will give a boost to the industry as it will also provide the needed data of operation in one of the most energetic areas of the sea. Overall, tidal power will also give us another component in the energy mix that’s more energetic and reliable than wind.”
In the journal, researchers say they are “extremely optimistic” that tidal stream technology can be realized relatively soon. However, while the articles paint a positive future for tidal power, a critical element is the availability of funds to undertake such deployment.
In the past month, the EU has announced funding in the region of £30m for two UK tidal projects. Investors in tidal technology are currently rewarded with a payment of five Renewable Obligation Certificates (ROCs) which are market variable. Each ROC is approximately £40 per megawatt hour of energy generated from such a resource, but this scheme will be reviewed in 2017.
According to Professor Bahaj, this could have serious implications for the emerging industry: “The rollout of the technology in its current state will depend on the subsidies. At this stage, it wouldn’t stack up financially, until wide experience gained from large-scale deployment is achieved.”
References:
- AbuBakr S. Bahaj, Marine current energy conversion: the dawn of a new era in electricity production, Philosophical Transactions of the Royal Society A, 2013, DOI: 10.1098/rsta.2012.0500
- W. M. J. Batten, M. E. Harrison, and A. S. Bahaj, Accuracy of the actuator disc-RANS approach for predicting the performance and wake of tidal turbines, Philosophical Transactions of the Royal Society A, 2013, DOI: 10.1098/rsta.2012.0293
- T Daly, L. E Myers, and A. S Bahaj, Modelling of the flow field surrounding tidal turbine arrays for varying positions in a channel, Philosophical Transactions of the Royal Society A, 2013, DOI: 10.1098/rsta.2012.0246
Comments (10)
by Vladimir Markovic
Dear Sir,
days ago I visited more home pages referring TIDAL projects. As I was previously following similar VERDANT program from USA, after studying all VOITH – Siemens and ALSTOM designs, I found out that all that projects are carrying similar disadvantages which are coursing 12 to 20 times larger investing and operational costs for each received MWh which instead of 35 to 40 € per MWh has price which overcomes 500 € per MWh and by my calculations could be never smaller than 300 € for MWh.
Since more years I am http://www.izumi.si involved also to problem of exploring energy from slowly moving water streams. Up to last year I used to work on only smaller units (SP 1) with Power up to 80 kW. Today I am involved in new designs (SP 2) which are 10 times stronger.
SP 2 units are incomparably cheaper, technically extremely simple and their life time can realistically be longer than 50 years. They are maximally 3 m high but their horizontal diameter is very large because SP2 are not axially operating (like other TIDAL turbines) but on radial way. Therefore, I made plans and calculations for two types of SP 2 units – 22 and 32 meters of diameter – very convenient to be used as TIDAL units:
SP 22 m with 300 kW of Power, complete price of 1,5 Million € and price for each MWh of 45 €
SP 32 m with 500 kW of Power, complete price of 1,9 Million € and price for each MWh of 40 €
In deeper water with high of nearly 6 m, capacity of each can be multiplied but not with doubled producing price what means that price for electricity can be lowered to 30 to 35 € for each MWh.
Please, answer me what are the reasons that all those companies are insisting in production of 20 times more expensive and technically wrong solutions regarding which we shall never get electric power based on expectable price ? I tried to ask them but I remained without any kind of answer.
Best regards,
Vladimir Markovic Ljubljana, 2013-03-31
by Serhii Honcharenko
Attempt to use the well-known technologists conversion of the kinetic energy of the flow of the wind or the potential of water energy for conversion of the kinetic energy of the water flow into electric energy are not effective.
The construction of dams and use of water turbines in the coastal zone is economically unprofitable, ecologically dangerous and socially dangerous (the accumulation of a large amount of water in densely populated coastal areas).
The use of wind turbines in the water also has a lot of significant shortcomings: 1. Coefficient of efficiency of the wind turbines is 12-14 % (14 % of the useful work, 86 % – losses to the formation of vortices). Due to the technical procedures (the attempt to use the energy of the unaccounted for in the calculations of side wind flows, reducing the loss of the flow on the formation of vortices for working blades, etc.) the coefficient of efficiency for wind can be raised up to 22 to 26 % in a very narrow range of speeds. However, for the water flow of these technologies cannot be applied because of the low water speed and the high density of water (in 1000 times higher than the density of the air). 2. However, any device the propeller type creates a sharp drop in pressure in the interaction with the flow of the fluid. If use of the wind turbines to the Strait between the Islands or to place such installations along the coast to work with the tidal currents, then we obtain the usual dam. The dam can break at any moment. Given the high density of the population living in the coastal zone, the breakthrough of the dam may have the most unpredictable consequences comparable with the tsunami. 3. Therefore, or we are ready to take the project to the theoretically maximum of 14 % efficiency and huge risk to the life of the population living next to such facilities, or we agree that the project should be relatively safe, but with a probability of practical use not more than 3-5 % of the kinetic energy of the considered flow of water.
Conclusion. The use of well-known technologies of the conversion of kinetic energy of the air flow for the conversion of the kinetic energy of the water flow energy into electricity environmentally and economically not profitable. For the conversion of the kinetic energy of the water flow into electric energy is necessary to use new sources of renewable energy. One of such renewable energy sources are non-stationary aerodynamic or hydrodynamic forces and moments (Unsteady Aerodynamic Influences – UAI), arising from the interaction of the working items with any flow of a fluid medium (water or air). The technology is simple, reliable, environmentally absolutely safe. Installation is equally efficient in the flow of any fluid medium (liquid or gaseous). Coefficient of efficiency, obtained in the testing of the experimental industrial plant in the flow of water is equal to 20 %. Coefficient of efficiency, obtained in the testing of the experimental laboratory installed in the flow of air is equal to 36 %. There is no overturning moment. There is no critical speed of the flow. Increase the capacity of the plant is due to the increase in the number of work items in length, width or depth of the flow. In carrying out of mooring trials, related to the replacement of a conventional propeller on a similar device, received 20 % saving of diesel fuel. Examples of tests of an experimental industrial installation in the flow of air from the low-pressure fan, in a stream of water, and when the vehicle is moving are presented below: http://youtu.be/c19by0iu1yA; http://youtu.be/pwCguY6Nboo; http://youtu.be/YMZeaeFAfY4.
by Katherine MacLean (old science fiction writer and research fan
Just subsidize the research in anything, and provide money prizes and student loan payoff for proposed improvements in any technopogy and the planned industry outlook will get more and more profitable on paper until it attracts investment even from its competators. Big oil will invest its ludicrous cash surplus into stocks in tidal and solar. New ideas from students outside the pield will not be warped to support the old propeller technology when a piston pump effect can elaborate from early steam engines with tides replacing expanding steam. Or canals experiance with water locks in steps raising and lowering hhugely heavy ships without sound or effort or wasted heat and smoke. In the threat. Water tanks. Compression of air generates heat and cold air in separate flows for air conditioning and cooking in a desert home, and the source of the compression is a trickle of water, clean water from the hill.s, distilled water from rain. salt water from the tides filling the compressor siide of a piston. Or llifting and lowering a float on the end of a lever and the lever motion pumping some useful work. Machinery of wood driven by water powerstarted long before metal+ .
by g. Hartwell
The density of water means that very small motion has huge amounts of momentum. Standing in a rushing river is much more difficult that in a high wind. Currents are constant wind is not. Many companies have developed and deployed designs for this use. Some links: http://inhabitat.com/worlds-first-tidal-farm-successfully-installs-100-foot-subsea-turbine/, http://peswiki.com/index.php/Directory:Blue_Energy, http://www.bbc.co.uk/news/uk-scotland-highlands-islands-10942856, http://www.technologyreview.com/view/411561/tidal-power-system-hits-record-output/, http://tidalenergy.net.au/, http://uekus.com/. Excellent direction to go for naturally derived energy.
by Snake Oil Baron
The government will push the technology to market before it is ready, using subsidies, sweetheart loans and guaranteed prices, only to see it fail and waste money. Then they will become discredited and no one will invest in them for years. If they would just let these technologies develop under market forces they would progress faster in the long-run. Instead we will see tidal power gererating plants join the derelict wind turbines and bankrupt solar farms as monuments to central planning impatience.
by Cog
All thanks to the sort of people who look feverishly for public failures as proof that only markets can build things and then discredit an entire industry to support their political views.
This is why Europe has high speed trains and the U.S. doesn’t.
by Will
How much more power could be generated if we pulled the moon closer to the earth? Goal for 2050.
by Atmic
Yeah, screw the massive biological chaos and ecological apocalypse that follows! :\
by CB
Why not incorporate evaporation tanks for fresh water, as well?
by Boristabby
Power in the oceans? Duh. When those Brits visited the much coveted Santa Monica, California, they should have tried body surfing.
And a review of methods in 2017? Well do not rush into anything, your retirements are still a ways away.