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Items  : 


Les potentiels exploitables des énergies marines,

Calculs, Hypothèses , Approximations et Données.

L’énergie de la houle


L’énergie thermique des mers : Research Proposal 
A Study of Impacts from the Seawater Intakes and Effluent Discharge Associated with Ocean Thermal Energy Conversion (OTEC)


OTEC : A neglected marine energy renewable resource  

L'utilisation de l'eau de mer profonde

Introducing Marine Energy Systems

The ocean is a huge reservoir of energy. In various forms this energy drives natural processes whose power has fascinated human beings for a long time. Since time immemorial they knew how to use Winds and Currents to power their boats, and the Tides to power their mills. At the dawn of the Industrial Age they invented machinery using the physical force of Waves and heat from the Ocean to serve their industry.
However, the relative abundance, and low cost of supply in financial terms, from burning coal, and later oil and natural gas, meant these other energy sources were not developed.

Today, because our «traditional» energy supplies appeared unable to satisfy the requirements for sustainable development, these renewable marine energies gain new interest, and an international consensus is being established which acknowleges that they could contribute to satisfying our needs for primary energy. 

The benchmark value for the needs is the present value of the world yearly consumption of primary energy, ie 10 billions of tonne oil equivalent (10 Gtoe) or 120 000 TWh/y.


Under the « Océan et Énergie » heading the Argonautes wish to spread knowledge on the basis and the state of the art of the technologies enabling conversion of marine natural processes to produce useful work, and give documented information on their advantages and drawbacks.

This note is an attempt to answer the question :  

«What share of the energy needs could Marine Energy sustainably supply? »

Marine energy 

Marine processes that can be used to produce energy are numerous. In this present inventory one considers only those having reached the stage of successful experiments at sea using already-developed technology at a scale showing extrapolation is feasible up to production plants of several MW, and with production costs consided economically acceptable in the (more or less) long term. 

The criteria for their economic acceptabilty one referred to in this paper are all the more imprecise in that the evolution of the energy costs 20 to 50 years in the future is very doubtful. It depends not only on fuel prices but also on changes in the cost structure itself with introduction of new taxes and costs which are presently « externalised » 

The natural phenomena and conversion processes considered here are :

  • Tide: associated with technology such as that developed for «La Rance » or that of tidal currents (similar to “underwater windmills” )

  • Offshore Wind: associated with Windmill technology

  •  Wave: associated with wave-energy-conversion systems

  • General Ocean Circulation: associated with Ocean Thermal Energy Conversion (OTEC) technology. 

Except for Tide, the energy from which derives via gravitational forces, all these phenomena result from energy and matter exchanges – mainly water in its 3 forms : liquid, vapour and ice – between ocean water masses, atmosphere and land.
The OTEC resource comes from the heat stored in the surface water of the Tropical and Sub-tropical Oceans. 
Windmills and Wave Energy Converters draw on the same flux of mechanical energy expressed in offshore winds whose primary energy is the same than that for OTEC :


 it is the solar thermal energy influx to Earth. 

Technologies developed to « harness » these phenomena are in essence non polluting since they introduce neither energy nor new chemicals in the biosphere; but they can cause perturbations of natural fluxes of energy and matter, occupation of marine areas, restriction to marine navigation, visual and even hearing nuisances. The knowledge of the impacts of these perturbations, constraints and nuisances is still insufficient to evaluate precisely the environmental and social limits acceptable for the exploitation of the resources. Hence those limits are incompletely accounted for in this note. 

Two sets of characteristics have been quantified for each form of Marine Energy. 

  • The mean power of the energy fluxes expressed in the whole of the seas and oceans by the natural phenomena considered here as the energy sources. Named Global Natural Resource - GNR –the fluxes magnitudes are those found in a recent scientific publication by Rui Xin Huang du WHOI from Woods Hole Oceanographic Institute (Ocean, Energy Flows in, Encyclopedia of Energy, Vol 4, Page 500, 2004, Elsevier Inc.), 

  • The share of these natural fluxes that could be exploited sustainably in the near future, say a few decades from now. It is named PTE for Potential Technicaly Exploitable. 
    For most of the marine renewable energy systems the lack of industrial experience in operation over long periods of time does not allow reliable estimation of these systems. The PTE values used for the purpose of this note are just orders of magnitude, or « best guesses », to be more precisely evaluated as the marine energy development progresses. 


This note aims to approach an answer to the question :

«What share of our needs for primary energy could Marine Energy sustainably supply? »

A first answer is given in Table below.


Marine energy forms

Potential Technicaly Exploitable

PTE en TWh/y

Potential shares

 en %


100 000





18 400





Total cumulé

120 000




Details on the hypothesis and calculations for Table  are available in page « Les potentiels exploitables des énergies marines, Calculs, Hypothèses , Approximations et Données » in French. 

These results show the exploitation of Marine Energy could supply about 120 000 TWh/y. That is the same order of magnitude as the present world primary energy consumption. 
These results also show the renewable Marine Energy resource is abundant, though it is probably not out of proportion to the future world demand for primary energy. It is important to be aware of this fact to ensure that people now do not claim future generations could draw on the marine tap without limit to satisfy their needs (although this remark does not account for the possibility to extract from the ocean the « fuel » for nuclear fusion power plants) . 

Table shows the sharing of Marine Energy contributions, varying in a range from less than 1% for Tide, to less than 20 % for Wind and Wave together, and to more than 8O% for OTEC. 
This should not conceal the interest in developing tide, wind and wave energy converters as they can be best adapted to some «niches» with special sites and local specific needs. But it highlights the importance of the OTEC resource potential; it reinforces the recommendation addressed by the « Club des Argonautes » to European Industry to carefully evaluate OTEC potential, which they seem to ignore presently. 


To read more (in French) :  


Les potentiels exploitables des énergies marines, 

Calculs, Hypothèses , Approximations et Données.
L’énergie de la houle

L’énergie thermique des mers                                       

L'utilisation de l'eau de mer profonde 


General sites about Marine energy :

IFREMER site,  papers on marine energy, espacially, wind and waves :

http://www.ifremer.fr/dtmsi/......,  (Compte-rendu de la journée d'études du Club ÉCRIN «Énergies alternatives»  du 20 octobre 2004). In french.  

Dedicated conference page of site IEA-Ocean Energy Systems  , in english.  



CLUB ECRIN site, in french: