Base-load power, 24/7
A continuous, weather-independent output from the thermal gradient, a rare profile among renewables.
Expertise · 04 / 04
Energy from the ocean’s thermal gradient. Day and night.
Ocean Thermal Energy Conversion turns the temperature difference between warm surface water and cold deep water into a constant, carbon-free source of energy, cooling, and, in open-cycle configurations, drinking water. We study its viability full-scale through the OTEC Lab, the heart of the MAEVA programme.
≥ 20°C
thermal gradient between surface and deep water is enough to produce energy
24/7
a constant resource, unlike solar or wind power
6 steps
OTEC Lab methodology, from site data to feasibility study
The principle
A natural heat engine between two ocean layers.
In tropical zones, surface water stays around 25°C while water pumped from 1000 m sits near 5°C. This permanent gradient can vaporise and then condense a working fluid to drive a turbine, and the same cold water can directly cool buildings (SWAC). OTEC is the only marine renewable available 24/7, independent of sun, wind or tide.
In the open cycle, warm seawater is flash-evaporated in a low-pressure chamber: about 5% turns to vapour, leaving its salt behind. That vapour drives the turbine, then condenses against the cold deep water, yielding pure desalinated drinking water as a by-product. The same plant can therefore deliver electricity, cooling and fresh water at once.
Seawater itself is the working fluid → also produces fresh water.
Warm seawaterCold seawaterWater vapourDesalinated fresh waterElectricity
Co-products
One resource, several useful outputs.
Beyond electricity, an OTEC plant turns the same pumped water into resources that are often scarce on island sites, which is precisely what makes the economic model add up.
Desalinated drinking water
Open-cycle condensation yields pure water: a 2 MW unit can deliver on the order of 4,000 m³ per day, around 2,000-2,300 m³ per MW.
Cold water for SWAC & more
The cold deep water also feeds air conditioning (SWAC), aquaculture and nutrient-rich applications.
Our approach · OTEC Lab
Simulate before building, on a full-scale test bench.
The OTEC Lab is our full-scale simulator, designed to model and optimise system productivity across different real-world site configurations. A six-step method, from site data to a usable feasibility study.
01
Site data collection
Environmental characteristics, depths, currents, temperatures, available energy resources.
02
Environmental modelling
Integration of oceanographic and meteorological data specific to the site.
03
Simulator configuration
Setup of the OTEC Lab to represent the real conditions of the target site.
04
Full-scale tests
Iterative tests in our laboratory to evaluate several configurations.
05
Productivity optimisation
Searching for the best configuration to maximise OTEC system efficiency.
06
Customised feasibility study
Delivery of results that can support a dedicated feasibility study for the project.
Deliverables
What we hand over at the end of the study.
Technical documents, measurable data, a feasibility dossier ready to support your decision.
Ocean resource study
Thermal profiles, depths, currents and energy potential of the target site.
OTEC Lab modelling
Full-scale simulation of the candidate configurations under real conditions.
Productivity optimisation
Search for the configuration that maximises the system’s energy yield.
System sizing
Heat exchangers, cold-water pipe, thermodynamic cycle and co-products.
Site integration
Coupling with a SWAC loop or cooling plant, valorisation of by-products.
Feasibility dossier
A results report usable to support financing and authorisation processes.
Use cases
Where OTEC makes sense
Tropical island territories
Réunion, French West Indies, Polynesia, Pacific: an ideal gradient all year round.
Base-load generation
Island grids dependent on imported fossil fuels seeking a stable renewable energy source.
Combined cold & power
Cooling and electricity drawn from the same deep-sea-water resource.
Coastal facilities
Process heat or cold plus on-site generation for port-side industries.
Aquaculture & desalination
Valorisation of nutrient-rich deep water and fresh-water co-production.
Demonstrators & studies
Academic and institutional partners testing OTEC under real conditions.
Technologies & scope
OTEC technical scope
ResourceThermal gradient ≥ 20°C between surface (~25°C) and deep water (~5°C)
DepthsCold-water pumping between 800 m and 1000+ m
CycleClosed Rankine (ammonia, R1234) or open cycle; low-pressure turbine
ExchangersLarge-surface evaporator/condenser, sea-water resistant
By-productsFresh water (up to ~4,000 m³/day for a 2 MW unit, open cycle), cooling (SWAC), nutrients (aquaculture)
FrameworkMAEVA programme, funded by the ANR, supported by Capénergies
FAQ
Frequently asked questions
What is OTEC (ocean thermal energy)?
OTEC (Ocean Thermal Energy Conversion) harnesses the temperature difference between warm surface water (~25°C) and cold deep water (~5°C) to produce energy. In tropical zones this gradient is permanent, making it a renewable source available around the clock.
What is the difference between the open and closed cycle?
In the closed cycle, a low-boiling working fluid (ammonia, R1234) circulates in a sealed loop to drive a turbine. In the open cycle, the seawater itself is flash-evaporated under vacuum, and this cycle additionally produces desalinated fresh water as a by-product.
Does OTEC really produce fresh water?
Yes, in the open cycle. The seawater vapour, once condensed against the cold deep water, yields desalinated, drinkable fresh water. A 2 MW unit can deliver on the order of 4,000 m³ of fresh water per day, on top of electricity, a major asset for island sites.
Where is OTEC relevant?
Wherever the surface/depth temperature gap reaches at least 20°C, mainly tropical and island zones (Réunion, French West Indies, Polynesia, the Pacific) with access to deep water. These territories often seek an alternative to imported fossil fuels.
What are the OTEC Lab and the MAEVA programme?
The OTEC Lab is Value Park’s full-scale simulator, at the heart of the MAEVA R&D programme (funded by the French National Research Agency, supported by Capénergies). It models and optimises the productivity of an OTEC system under a site’s real conditions before any deployment.
Is OTEC available continuously?
Yes. Unlike solar or wind, the ocean thermal gradient is stable day and night: OTEC is the only marine renewable able to deliver 24/7 base-load generation, independent of the weather.
How mature is OTEC?
OTEC is an emerging technology, at the R&D and demonstrator stage. Value Park develops it through the OTEC Lab to assess, site by site, the real feasibility and productivity, an essential step before considering a full-scale project.
A tropical or insular site in mind?
We can assess the OTEC potential of your site within the OTEC Lab. Let’s talk.
Our solutions