Tidal energy and energy from temperature difference and blue energy

This concerns, for instance, getting a good picture of the speed and density of flows in rivers and the freshwater/salt water distribution. When applying certain techniques, such as salt gradient/blue energy, the latter listens closely. A technique such as tidal energy is interesting in places where the difference between high and low water is large or where there are strong currents.

Every technology has the potential to contribute to the energy transition. We follow developments closely and continue to conduct research to take them further.

Anton de Fockert, flow expert

Tidal energy

Tidal energy is a reliable and sustainable form of energy, which is always present and more predictable than wind energy or solar energy. As a result, tidal energy has the potential to make a significant contribution to the global renewable energy target. The greater the difference in ebb and flood, the more potential.

Deltares supports project developers, tidal energy turbine manufacturers, investors and governments in the design, construction, management and maintenance of tidal power plants. Our expertise and tools on currents, waves, morphology and ecological impact help optimise energy production and minimise costs and impacts on the environment. This makes tidal energy a competitive form of energy in the future.

From large-scale flow and impact on the environment to detailed flow around turbines

In the Swansea Tidal lagoon, the European Energising deltas programme and the tidal energy turbines in the Eastern Scheldt storm surge barrier, Deltares has gained experience in several projects. Here, the knowledge of large-scale effects such as currents, sediment and ecological changes was translated into the consequences for detailed flow around the turbine. This knowledge and experience are very important for exploiting the maximum yield of the turbines.

Together with the client, we map the effects on the environment. In order to achieve optimum inflow and outflow and increase the efficiency of the tidal power plant, it is crucial to involve the tidal energy turbine supplier in the study. We deploy our experience and knowledge to:

• Assessing and optimising local flow near the turbine with numerical and physical facilities
• Estimating the ecological and morphological effects for an EIA (Environmental Impact Assessment)
• Preventing scouring and erosion near the turbine constructions
• Preparing ecological impact studies for a fish-friendly design of the tidal turbines and marine life
• Employing operational predictive systems for controlling the turbines
• Testing new concepts

To optimise the output of the tidal power stations, we employ a combination of different numerical models like:

• Delft3D for large-scale effects of flow, sediment transport, morphology, waves, water quality and ecology
• WANDA for optimisation of the energy output
• StarCCM+ for detailed flows near the turbines
• RTC-Tools, for real-time control optimisation
• Delft-FEWS, for predictive system models

Energy from temperature difference: Ocean Energy Technologies

With Ocean Thermal Energy Conversion (OTEC), energy can be extracted 24 hours a day from the temperature difference between different layers in the ocean. In places with a significant temperature difference between the upper and deeper layers of the ocean, conditions are most favourable for the highest efficiency. This is especially the case in areas where it is warm, such as near the equator.

Deltares' knowledge of currents and their effects on the environment supports project developers, producers, investors and governments in the design, construction, management and maintenance of their OTEC plants.

Visualising density flows, plume dispersion and water quality

It is relevant for our clients, for example, to know how to set up an OTEC plant sustainably and efficiently. To this end, our studies map density flows, plume dispersion and the effects of hot water discharges on water quality and ecology. This is necessary because in OTEC systems you heat and cool water. This changes the temperature and density of the water, while the salinity remains the same. After discharging this water to a location with a different density, density flow occurs.

This can lead to unwanted ecological growth. at the plant's inlet and outlet. We also assist developers in the hydraulic and thermal design of the OTEC power plant. We do this by analysing energy losses in the power plant and looking at the heating and cooling process of the intake and discharge. We also carry out partial studies on specific problems. For example, we assessed the potential of different sites for Bluerise OTEC power plant in Curaçao.

Deltares has gained worldwide knowledge and experience with conventional power plants over the past decades. Combined with the expertise of our studies from related fields, Deltares can conduct integrated research and provide advice:

• For developers, we conduct research on the feasibility of OTEC power plants and how to minimise costs and risks.
• Governments and stakeholders can use our impact analyses and environmental studies to build support for OTEC power plants.
• Anyone otherwise involved in the development of OTEC plants can use our systems knowledge to build a sustainable and efficient plant.

For design, predicting effects and improving the efficiency of OTEC systems, we deploy the following software packages:

• Delft3D for flow, density flow and water quality modelling
• CORMIX for measuring plume dispersion at the discharge point. CORMIX and Delft3D can also be used in combination.
• WANDA for hydraulic and thermal design of the supply and discharge systems of the OTEC power plant.

Blue energy: energy from salt gradient

Blue energy has great potential for renewable energy generation. This energy is generated from the difference in concentration between salt and fresh water through osmosis. Like energy from temperature differences and tides, energy from salt gradient is not dependent on external influences such as wind or sun.
Deltares provides project developers, contractors, investors and policymakers with knowledge about flow, recirculation and the impact on the environment to make blue energy a sustainable form of energy. In the Blue Energy project on the Dutch Afsluitdijk, the world's first blue power plant, we are investigating with partners the ecological effects of large-scale blue energy projects and looking at possible upscaling.

With blue energy, you have to know very accurately what concentrations of fresh and salt water you are taking in and how the water flows. If the discharged water mixes with the water you take in then this can lead to energy loss very quickly. With our knowledge of this, we add value.

Anton de Fockert, flow expert

We have been doing studies for various forms of power plants for more than 40 years. For a sustainable and efficient blue power plant and minimal impact on ecology, our systems knowledge is essential. For instance, differences in freshwater-salt gradients have a direct impact on the amount of energy extracted. Discharging too much saltwater to freshwater, combined with the flow, can lead to salinisation and thus energy loss. The question is therefore: how can we prevent the discharged water from mixing with the water you want to take in?

Our research on recirculation and plume dispersion, which we also carry out at OTEC, is crucial to assess the fresh-salt gradients at the power plants' intake. And because several fields of expertise converge in blue energy, we assess studies of this kind both separately and, more importantly, integrally.

Our clients

Among other things, we make our knowledge available to project developers who want to prevent water hammer. We advise them on hydraulic design. We also analyse the internal mixing of the systems based on detailed hydrodynamics. This provides maximum energy generation. Project developers and investors can come to us to determine energy potential, feasibility and design implementation. Contractors use our research to save costs and minimise risks during construction and maintenance of blue energy plants. Policymakers and stakeholders can use our impact analyses and environmental studies to create public support.