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Energy from the sea
Energy systems play an important role in the transformation towards sustainable development. While the report ‘A Social Contract for Sustainability’ (WBGU, 2011) focused mainly on terrestrial aspects of energy generation, the present report takes a closer look at the potential for generating energy from and on the sea. In the extraction of oil and gas there is already a clear trend towards offshore exploration. This development seems to be continuing in the field of renewable energy; the use of offshore wind energy, for example, is growing much faster than onshore use in European countries. Technologies for generating electricity are playing an important role in the offshore expansion of renewable energy because they enable considerable increases in technical efficiency for all downstream processes of energy use. The improvement in efficiency along energyconversion chains makes it attractive to use more electrical energy. Important examples include electromobility and the increased use of electric heat pumps for heating or air-conditioning buildings. In this context electricity from renewable energy displaces fossil fuels such as petrol, diesel, heating oil and gas. These developments then make a massive contribution to the decarbonization of the energy systems. Another possible method of low-CO2 energy generation is to use fossil fuels, but to separate and store the resulting CO2 (CCS) – if the CO2 can be stored safely over geological timescales. The oceans can make a decisive contribution to both alternatives in the future. In general, wind and solar energy could make the most important contribution towards power generation using renewable energy. Both technologies produce electricity without heat losses. The biggest wind-energy potential is seen in offshore use, because it allows a relatively balanced energy supply and could be a good option for supplying near-coastal metropolitan areas (WBGU, 2011). CCS is a necessary climate-protection option for countries that do not wish to stop using fossil fuels. From a safety and acceptability viewpoint, the best options for storing the CO2 separated from fossil combustion processes are to be found beneath the seabed (WBGU, 2006). In the long run another use of the seas might be
added in which the high productivity of aquacultures is used for bioenergy production. If the CO2 generated in the process is deposited beneath the seabed, CO2 is actively removed from the atmosphere. The oceans themselves are becoming increasingly interesting for energy storage, too. Marine pumpedstorage power plants open up new possibilities for a cost-effective and environment-friendly short-term storage of electrical energy. Further possible uses of the seas include the production of hydrogen or methane from wind power or from aquaculture-based biomass for the long-term storage of energy and the provision of chemical raw materials. In addition, the oceans are increasingly being used for energy infrastructures and transporting electricity and energy gases. The seas can therefore develop into an indispensable component of future sustainable energy systems. Global agreements on the governance of the oceans and the seabed must therefore be developed and put into place in good time to avoid foreseeable conflicts involving this type of use (Chapter 3).
5.1 Fossil energy carriers from the sea The following section gives a brief overview of current estimates of global deposits of fossil energy resources, the technologies and costs of mining them at sea, and the interactions with sustainability goals that can arise as a result of their extraction. This appraisal lays the foundation for a description of the future role of fossil energy carriers in a visionary form of marine, sustainable energy generation (Section 5.3). The following analysis distinguishes between conventional and unconventional fossil energy sources (oil, gas, marine methane hydrates). The expansion of mineral-oil and natural-gas production into the sea has already taken place, so that a wealth of experience is available in this field. This does not apply to the extraction of marine methane hydrates, which are not yet commercially mined.
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