Harnessing the Oceans

Is energy from the oceans even feasible?

By Hans Buitelaar

If saving the planet is not enough reward for harvesting the enormous energy potential of the oceans, high profits on renewable energy installations might be the incentive that makes investors open their wallets.

Following decades of technology development and efficiency improvements, today the cost of energy production from renewable sources could drop below the price of energy from oil, coal or gas if done on a large enough scale. Even conservative industry experts herald the end of fossil fuels and the dawn of an era of renewable energy. The only dispute now is the pace of the changeover.

Vast Potential

Offering strong currents, big temperature differences, ongoing wave motion on the surface and lots of open area over which winds can develop, the world’s oceans offer a variety of energy sources and the potential for extensive involvement by the maritime industry. Offshore installations of wind turbines, underwater turbines in tidal currents, offshore thermal energy platforms and surface installations harnessing the kinetic energy of waves all require large and specialized vessels.

Next come the converter stations and underwater cables for connection to onshore electricity grids. Following commissioning and initial operation, maintenance is needed, and that too requires vessels suitable for getting workers to and from offshore power plants safely. Big advances in vessel design and boat-to-platform facilities have already been made in the last decade. If indeed the number of offshore energy installations booms during the next ten years, additional shipbuilding and vessel innovations may be expected to efficiently facilitate the production of green offshore energy.

1 in 75 Light Bulbs

Given the forecasts of futurologists predicting a total energy transition during the coming decades, the actual numbers presented by the renewable energy industry associations are quite modest. Over the whole of the European Union, 11 gigawatts of offshore wind power have been installed to date, representing 1.3 to 1.5 percent of total electricity consumption in the 27 member countries. These figures come from the European Wind Energy Association (EWEA).

The continent is committed to reaching a level of 20 percent renewable energy production by 2020. Offshore wind, of course, is only one of the sources. Onshore wind, solar and hydropower are the others.

The point is that just one out of every 75 light bulbs in the E.U. is powered by offshore wind. This follows “a record year in terms of installed capacity and money invested,” according to EWEA spokesman Oliver Joy. “Three GWs was connected last year. This record is the result of a lot of projects reaching their final phase in 2015 and being connected to the grid. We will see a decline in the growth of installed capacity in 2016 and 2017 due to project time lines. 2015 happened to be a year with lots of project finished while new ones under construction today will only get connected around 2018.”

Ninety percent of the world's offshore turbines are along the northern European coasts, close to large population centers. “This technology is not so easy to learn,” says Communications Director Luaha Fried of the Global Wind Energy Council. “You need the underwater network, the converter stations, the grid connection and all the vessels to install and maintain everything. Secondly, regulations at sea are different from those on land. At the installation of a wind park off the Chinese coast, two different government bodies had to grant permission, and there were issues with a military zone nearby. All of this makes it less favorable for countries outside Europe to choose offshore wind.”

Still, large-scale offshore wind parks are installed or under construction all along the coast of Asia, led by China. With 1,000 MWs of capacity installed by the end of 2015, China ranked fourth in global offshore wind, following the U.K., Germany and Denmark. Total global capacity currently stands at 12,105 MWs.

Meanwhile, turbine capacity is increasing in this most developed branch of ocean renewables. Manufacturer Siemens is now testing a single offshore turbine that produces 7 MWs on its own. 

Managing Expectations

In view of the E.U. target of generating 20 percent of total energy in a sustainable way by 2020, the EWEA has scaled back overheated expectations of providing 43 GWs of offshore wind power as hoped for by politicians to a more realistic 23 GWs, still about doubling today’s total world capacity in Europe alone.

Totally different is the optimistic approach of Ocean Energy Europe (OEE), an industry association that promotes building large installations to generate electricity from wave energy, tidal rise and fall, currents, ocean thermal energy and osmotic power (salinity). OEE estimates that the total contribution of ocean energy from these sources can be ten percent by 2050. At this moment there is a combined capacity of 260 MWs in wave and tidal energy installations. The goal is therefore a 4,000 percent growth in 34 years. Futurology is fluid.

“Around 20,000 MWs of wave and tidal stream energy installations are expected by the early 2030s,” states OEE’s Policy and Operations Director Jacopo Moccia. To achieve the goal of providing ten percent of Europe's energy demand, capacity should grow to 100,000 MWs by 2050.

Moccia is confident about a price drop with upscaling the number of ocean energy projects: “Prototypes may have a cost of energy oscillating between €0.20/KWh and €0.50/KWh today. As the sector industrializes, the objective is to rapidly reach the ten cent per kilowatt hour mark.”

As for offshore wind, the EWEA’s Joy says the goal is to make it price-competitive: “Goals set by various large companies in this industry are to reach a price level of €100 ($111) per megawatt hour by 2020. We are getting close to this goal. This year, the power provided by a quite large wind park off the Danish coast was offered at €103 ($115). We are already quite near competitive pricing.” The €13.3 billion ($14.8 billion) invested in new projects last year is a sign of renewed belief in the economic viability of offshore wind.

While the end goal of totally replacing fossil fuels with renewable energy appears merely a dot on the horizon, the transition is gaining momentum. Recently, the island of El Hierro, part of the Spanish archipelago of the Canaries, achieved total self-sufficiency in power generation, all by renewable means. This sets an inspiring example. As the renewables industry scales up, energy prices will eventually drop below fossil fuel-generated electricity. With profits as the incentive, transitions may accelerate beyond imagination. – MarEx

Hans Buitelaar writes from the Netherlands.

Types of Ocean Energy:

According o the International Energy Agency’s 2015 report, “Ocean Potential,” the energy potential of the oceans is calculated to be 20,000–80,000 terawatt-hours (TWhs) of electricity, generated by changes in ocean temperatures, salt content, and the movements of tides, currents, waves and swells.

The methods of transforming the ocean's perpetual motion into electricity include:

• Wave energy: Floating objects pull a cable when they are lifted by a wave. With every pull, a generator spins. These are called Point Absorbers. Linear Absorbers are large floating structures that tilt over the waves. When the connection points of tubes twist, hydraulic ram joints propel a generator. There is also the Wave Dragon, a floating platform that fills with overtopping waves that then enter an enclosed area that is higher than the water surface. The elevated water can flow back to the ocean level through a hole with a turbine.
• Tidal energy. Placing a turbine in a spot where strong tidal currents occur is one way of generating electricity. This is called Tidal Current Energy. A second way to capture the energy of rising and declining water levels is by building a dam that encloses a lagoon, which fills with the tide through a small opening in which a turbine is placed. As the tide goes down, the turbine will be propelled the other way. This is called Tidal Range Energy.
• Ocean current energy: Placing turbines on the ocean floor in places where strong currents exist.
• Ocean thermal energy conversion (OTEC). Warm surface water is used to vaporize a liquid with a low boiling point, such as ammonia. The gas propels a turbine to generate electricity. The gas is then cooled by colder water that is pumped up from deeper in the ocean to condense again and create an ongoing cycle of electricity generation.
• Osmotic power or salinity gradient: Still in its development phase as a technology. Using the differences in water density and pressure between fresh water coming from a river and flowing into the salt water of the sea, electricity is generated by leading the lighter fresh water through a turbine as it wells up from under a membrane that separates the incoming river water from the sea.

Offshore wind is not considered a marine energy source as it comes from wind over the water instead of from the water itself. – MarEx