Energy from the deep
Ocean thermal energy conversion (OTEC) is one of four MRE being actively developed as part of the Group’s ambitious MRE growth strategy. OTEC plants use the temperature gradient between sea surface water at around 25°C and deep cold water at around 5°C (- 1,000 metres). This temperature difference exists only in tropical seas, where OTEC can be used to produce 24/7 power.
Promising applications
DCNS aims to demonstrate the technology’s feasibility and its promising for tropical zone communities that are typically highly dependent on fossil fuels. In April 2009, DCNS and the Reunion Island regional council signed an initial R&D agreement to study the feasibility of installing a 1.5-MW OTEC demonstrator on this Indian Ocean island. In February 2010, the local government of French Polynesia, the national government, Pacific OTEC and DCNS signed an agreement to conduct a feasibility study of an OTEC plant for Tahiti. This year, the Martinique regional authority in the Caribbean responded to the European Commission’s NER 300 call for tenders with a proposal for a 10-MW OTEC pilot plant. As a result, DCNS and the Martinique authority signed a preliminary sizing agreement for a plant that could come on stream as early as 2015.
The “PAT ETM”, a land based test bench
In October 2009, DCNS, the Reunion Island regional council and La Réunion University signed a second agreement, (this time under the French government’s ”future investment” framework program) to further investigate technological challenges and OTEC funding. This agreement calls for the construction of the “PAT ETM” land-based test bench of the energy production system. This fully-autonomous prototype will use seawater at artificially controlled temperatures to test the thermodynamic cycle and key energy conversion components including heat exchangers while training DCNS teams in OTEC control systems.
Following its construction at DCNS’s Nantes-Indret centre, the PAT ETM test bench is now undergoing qualification tests. When these have been completed, the facility will be shipped to Reunion Island and installed in La Réunion university at Saint-Pierre. It will then be used for further testing by local research students and DCNS teams.
This second agreement also calls for environmental studies and numerical modelling to develop cold water pumping procedures. The challenge is to design, fabricate, install and operate, for at least 20 years, a 1,000-metre-long pipe several metres in diameter.
An OTEC pilot plant for Martinique
In parallel with these developments, DCNS and the Martinique regional authority signed an agreement in November 2010 for a feasibility and exploratory installation study for a 10-MW OTEC pilot plant in Martinique. This pilot plant could come on stream as early as 2015, down the French tropical waters. In addition to producing usable power, this pilot plant would serve as a precursor for a series of OTEC plants that DCNS hopes to install in the whole intertropical belt.