Marine Energy

“Marine energy will become an essential part of the renewable energy mix”

The march of renewable energy is unstoppable. At present, we already produce energy by harnessing the power of the wind and the sun. In addition, using the power of the sea would be another promising field. FQF talked to Britta Schaffmeister, Director of the Dutch Marine Energy Center, The Netherlands, about the current situation of marine energy.

Ms Schaffmeister, the Dutch Marine Energy Center is a not-for-profit network and consulting organization for the marine energy sector. What is your mission?

DMEC ‘s vision is that marine energy becomes an intrinsic part of the renewable energy mix, next to solar and wind energy. To achieve this, we stimulate marine energy developments, both in the Netherlands and abroad, in order to:

  • Accelerate technology development, innovation and commercialisation
  • Shorten the time to market for marine energy devices
  • Promote their export to global markets

To this end, we build strategic collaborations between technology developers, research institutes, and offshore companies in the Netherlands and internationally to realise the development of joint projects and business cases. Based on these collaborations, we offer a suite of services covering the entire product development life cycle; from initial product design towards the realization of national and international commercial projects.

Using the power of the sea, different technologies come into play. Could you give us an overview?

Different organisations use different definitions, but when we are talking about “marine energy”, we mean all energy that is generated from the sea. Offshore wind energy, for instance, would not be included in that. The technology areas we consider are wave energy, tidal energy, ocean thermal energy conversion (OTEC), and salinity gradient energy.

A growing field is the production of biomass, suitable for the production of sustainable liquid fuels like bioethanol and biodiesel, from aquatic sources like seaweed or algae. We aren’t involved in this development, but we watch it with interest.

What are the operating principles of these technologies?

Each technology area has a different operating principle:

Tidal energy is used to denote either the generation of renewable electricity from tidal head (the water level differences between high and low tide), or from tidal stream, which is the flow of water that originates from the tidal cycles. Tidal head technologies usually focus on impounding a large natural reservoir, like estuaries, and using the potential energy difference between low and high tides to generate electricity with turbines inside the dam. A well-known example that has been operational for decades is the La Rance tidal power station in France.

Tidal stream technology is often compared to wind energy, because it has more or less the same operating principle. Tidal flows originating from the tidal cycle can be used to turn a turbine and generate electricity. There are a variety of systems that are in development now, but most common designs focus on three-bladed horizontal axis turbines – much like underwater wind mills! Vertical axis turbines are also in development, as are tidal “kites”.

Wave energy devices make use of the kinetic energy stored in ocean waves. There is no dominant design yet, so it is difficult to assign just one operating principle. The gist of it is that waves essentially consist of moving water particles, that each move up and down in the water column. The kinetic energy of these molecules can be used to make a device move based on pressure differences within the water column.

Ocean thermal energy conversion uses the differences in temperature in the water column. Especially in equatorial regions, the temperature difference between the top layers of the ocean and the deeper layers can be quite significant, reaching up to ~25 degrees Centigrade. The hotter water can be used to evaporate a working fluid with a low boiling point, which drives a gas turbine. The cold water is subsequently used to cool down the gas and turn it into a fluid again, ready for another round of energy generation. As such, OTEC is a form of renewable energy that can generate electricity 24/7, all year round.

Salinity gradient power makes use of the difference in salt concentrations in bodies of water. There are two main categories of this type of technology in development at the moment. First, in pressure retarded osmosis (PRO), salt and fresh water are separated by a membrane that can let water through. As salt water has a higher concentration of charged particles (or ions), osmosis moves water from the reservoir with fresh water to the one with salt water. The larger volume inside this reservoir will increase the pressure inside, which can be used to generate energy with a pressure turbine.

Reverse electrodialysis (RED), uses a slightly different mechanism. Rather than using a membrane that’s water permeable, two reservoirs of salt and fresh water are separated by a membrane that is ion-selective – it only let’s through certain ions with a particular charge. The result is that negative ions move from the salt water reservoir to the fresh water reservoir. This leads to an electrical potential over the membrane, which can be used to generate electricity.

What are the advantages of marine energy systems in comparison with other renewable sources?

There are several, but the main advantage is the fact that marine energy can either generate electricity continuously (salinity gradient and OTEC), or is highly predictable (wave and tidal). This is a big selling point over wind and solar energy, which are highly intermittent. As such, marine energy will become an essential part of the renewable energy mix as it can level out some of the electricity generation peaks and limit the storage capacity needed to run future electricity grids.

In addition, marine energy is always available – the ocean is a non-exhaustive source of energy, unlike fossil fuels or nuclear energy. Furthermore, technologies are environmentally friendly: They produce none to limited by-products, waste, and greenhouses gases during operation. Because the energy density of water is a lot higher than wind or solar energy, devices can be made smaller so they can be integrated in wet infrastructures like dams, bridges, and dikes. Other interesting applications lie in offshore and subsea operations, where they can be used to generate electricity on site for offshore structures.

A last important advantage of marine energy is a mimimal impact on the land and shoreline. Most devices are operated on the surface of the ocean, or below the surface, eliminating the NIMBY debate and stimulating public acceptance of this new form of renewable energy.

To this day, the marine energy technology did not make the commercial breakthrough. Which challenges will you have to meet to make marine energy successful in the future?

Lots has been written about sector challenges. You can find them in every industry report and policy document (for instance, the Ocean Energy Forum has published several good sector overviews, e.g. Ocean Energy Forum Strategic Roadmap 2016). In general, they can be divided into different categories, amongst which 1) financial, economic and market barriers, 2) political and governance challenges, 3) consenting & environmental challenges, and 4) societal obstacles.

Overall, it is important to acknowledge that marine energy technologies have not nearly had as much development time as solar and wind energy technologies, but are expected to operate on the same level (and for the same price) as them. The sector is still very much dependent on public funding. To attract more private investments, the technologies need to be demonstrated and showcased around the world to work their way through the respective learning curves and lower the levelized cost of electricity (LCOE). Additionally, much like the concerns regarding birds for wind turbines, the sector needs to prove that the impact of marine energy devices on aquatic ecosystems is limited.

At DMEC, we address the above mentioned challenges by creating multi-stakeholder partnerships and developing projects that have positive effects for all parties involved. We stimulate the implementation of marine energy technologies in the extensive Dutch wet infrastructure by using Dutch expertise in water management, offshore and maritime operations. An example would be the integration of tidal turbines in openings in a dam. This has been done at several locations in the Netherlands, including the Eastern storm surge barrier (“Oosterscheldekering”), where five turbines produce 1.2 MW of electricity – enough to supply 1000 local households with electricity.

The integration of technologies in these so-called “marine energy concepts” leads to lower CAPEX requirements, and provides a good showcase integrating Dutch water management and renewable energy generation. Furthermore, integration in infrastructures enables developers to test and demonstrate their technologies, and helps to attract investors.

Interview: Sebastian Kaiser

Further information

http://www.dutchmarineenergy.com

ABOUT BRITTA SCHAFFMEISTER

With a biological background and more than 13 years of practical experience, Britta has supported a wide variety of innovation-driven public-private partnerships within the fields of global health, food safety & security, and sustainable marine energy. Over the years she gained experience in steering the process of strategy and organisational development as well as strategic innovation management and financing within complex multi-stakeholder and multi-cultural environments. As the director of DMEC, she is responsible for the strategic positioning of DMEC and the initiation and implementation of strategic partnerships.

“My passion lies in science-based business, aligning excellent research with market needs and societal challenges. Through an energetic and pragmatic approach combined with strong analytical- and people skills, I challenge people to join efforts and deliver hands-on solutions.”

 

 

 

 

 

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