Chapter 22. Other Marine-Based Energy Industries Contributors: Amardeep Dhanju and Lars Golmen, Peyman Eghtesadi Araghi (Co Lead member), Peter Harris (Co-Lead member) 1. Marine Renewable Energy Resources: Background This chapter concerns ocean processes that are viable sources of renewable energ in various forms, such as offshore wind, waves, tides, ocean currents, marin biomass, and energy from ocean thermal differences among different layers (Appiot et al., 2014). Most of these energy forms are maintained by the incoming heat fro the sun, so they represent indirect solar energy. Tidal energy is an exception, drive by the varying gravitational forces that the moon and sun exert on both the eart and its oceans (Butikov 2002). Marine renewable energy offers the potential to mee the increasing global energy demand, while reducing long-term carbon emissions Although some marine renewable energy resources are still in a conceptual stage other sources have been operational with varying degrees of technical an commercial success. The following section briefly discusses various forms of marin renewable energy sources that are currently in operation or in a demonstratio phase. 1.1 Offshore Wind Power: Background Offshore wind power relates to the installation of wind turbines in large wate bodies. On average, winds blow faster and more uniformly at sea than on land, and faster and steadier wind means less wear on the turbine components and mor electricity generated per turbine (Musial et al., 2006). The potential energy produce from wind is proportional to roughly the cube of the wind speed. As a result, marginal increase in wind speed results in a significantly larger amount of energ generation. For instance, a turbine at a site with an average wind speed of 25 km/ would provide roughly 50 per cent more electricity than the same turbine at a sit with average wind speeds of 22 km/h. Offshore wind power is also the most developed form of marine renewable energy i terms of technology development, policy frameworks, and installed capacity Turbine design and other project elements for offshore wind have benefite significantly from research on and experience with land-based wind energy project and offshore oil and gas development (Steen and Hansen, 2014). It is already a viabl source of renewable energy in many regions and is attracting global attentio because of its large-scale resource potential, also often close to major electrical loa centers in coastal areas. In light of these factors, offshore wind energy appears t have the greatest immediate potential for energy production, grid integration, an climate change mitigation. © 2016 United Nations 1.2 Ocean Wave Energy: Background As the wind flows over the ocean, air-sea interface processes transfer some of th wind energy to the water, forming waves which store this energy as potential energ and kinetic energy (Special Report on Renewable Energy Sources and Climat Change, 2011). The immense power of waves can be observed at the coast, wher this energy can have considerable impacts on coastal landscapes, shorelin topography, and infrastructure. Efforts are now underway to tap this resource fo electric generation using wave energy conversion (WEC) devices. WECs transfor mechanical energy from the surface motion of ocean waves or from velocit fluctuations below the surface into electrical current. 1.3 Tidal Power: Background Tides are regular and predictable changes in the height of the ocean, driven b gravitational and rotational forces between the Earth, Moon, and Sun, combine with centrifugal and inertial forces. Many coastal areas experience roughly two hig tides and two low tides per day (called “semi-diurnal” tides); however in som locations there is only one tidal cycle per day (these are “diurnal” tides Specia Report on Renewable Energy Sources and Climate Change, 2011). Tidal power can b harnessed either through a barrage or through submerged tidal turbines in straits o sounds. Tidal barrages involve the use of a dam across an inlet. Sluice gates on th barrage allow the tidal basin to fill on the incoming high tides and to empty throug the turbine system on the outgoing tide (U.S. EIA, 2013). Energy extraction using tidal barrages is derived from the potential energy create when elevation differences develop between two water bodies separated by a da or barrage, which is analogous to the way a turbine operates in a hydroelectric plan on a dammed river. Conversely, submerged tidal turbines that operate without barrage only rely on the kinetic energy of the freely moving water. Because water i about 800 times denser than air and is more corrosive, tidal turbines must be muc sturdier than wind turbines (U.S. EIA, 2013). 1.4 Ocean Current Energy: Background Ocean currents are the continuous flow of ocean waters in certain directions, drive or controlled by wind flows, salinity, temperature gradients, gravity, and the Earth’ rotation or coriolis; (U.S DOE, 2013). Although surface ocean currents are generall wind driven, most deep ocean currents are a result of thermohaline circulation — process driven by density differences in water due to temperature (thermo) an salinity (haline) in different parts of the ocean. Currents driven by thermohalin circulation move much slower than surface currents (NOAA, 2007). Many large an powerful ocean currents, such as the Gulf Stream off the east coast of the Unite States and the Kuroshio Current off the east coast of Japan, represent an enormou source of untapped energy that can be harnessed through large underwate turbines. © 2016 United Nations 1.5 Ocean Thermal Energy Conversion (OTEC): Background The OTEC system produces electricity from the natural thermal gradient of the ocea between the surface and subsurface ocean waters in tropical and subtropica regions. Heat stored in warm surface water is used to create vapor to drive a turbin and generator, and cold, deep water pumped to the surface recondenses the vapo (Avery and Wu, 1994). The OTEC heat engine is usually configured to operate as thermodynamic Rankine vapor cycle in which a low-boiling-point working fluid (suc as ammonia) is evaporated by heat transfer from the surface seawater and produce electricity by expanding through a turbine connected to a generator. The vapo exiting the turbine is condensed with the cold deep water. This is the Closed-Cycl process. The Open-Cycle process uses expendable water/seawater as the drivin fluid, under low (<0.1 Atmosphere) pressure. After the flash evaporation of the fluid fresh, potable water may be collected on the condensers, while new seawater i being evaporated upstream. Additional freshwater may be collected in a secon exchanger utilizing the remaining Delta-T after the first stage. Thus, the Open-Cycl process generates both electricity and potable water. The OTEC systems have been demonstrated to work successfully, but no large-scal plant has been built yet. A benefit of OTEC is that it produces constant base-loa electricity, in contrast to other forms of ocean energy sources that fluctuat according to varying winds and currents. 1.6 Osmotic Power: Background Salinity gradient energy is an often-overlooked potential source of renewable energ from the ocean. The mixing of freshwater and seawater that occurs where rivers an streams flow into the salty ocean releases large amounts of energy. Various concept on how to make use of this salinity gradient have existed for over twenty years. On such concept is Pressure-Retarded Osmosis (PRO), in which seawater is pumped int a pressure chamber where the pressure is less than the osmotic pressure differenc between fresh river water (low salinity water) and seawater (higher salinity water) Freshwater then flows through a semi-permeable membrane and increases th volume (or pressure) within the chamber; a turbine is spun as the pressure i relieved. Early technologies were not considered to be promising, primarily becaus they relied on expensive membranes. Membrane technologies have advanced, bu they remain the main technical barrier to economical osmotic energy productio (Appiott et al., 2014). Also, water on both sides must be low in particulates and othe solids, eliminating many rivers from being a potential freshwater source. 1.7. Marine Biomass Energy: Background Some researchers are looking towards marine biomass, including seaweeds an marine algae as a viable source of biofuel. Interest in marine biomass is driven bot by the potential productivity of microalgae, which is tenfold greater than that o agricultural crops, and because, unlike first-generation biofuels, microalgae do no require arable land or freshwater, nor do they compete with food production (NERC 2014). Marine ecosystems are highly productive because they cycle energy and © 2016 United Nations nutrients much more rapidly and efficiently than terrestrial ecosystems. Marin algae are photosynthetic aquatic plants that use light as the energy source an seawater as a growth medium. Algae can be harvested and processed into biofuels including biodiesel and bioethanol. Biodiesel is a non-toxic and biodegradable fuel that is being used in existing diese engines without requiring significant modification. Bioethanol can also be used a fuel when mixed with gasoline. Algae grown for biofuels can also provide a sink fo carbon dioxide, thereby contributing to climate change mitigation (replacing fossi CO, with biogenic CO2 emissions). Algae are an economical choice for biodiese production because of their wide availability and low cost. Despite these advantages however, offshore production of algae is still developing and most algae productio takes place onshore. 2. Resource Assessment and Installed Capacity (Global and Regional Scales) 2.1 Offshore Wind Capacity An assessment of the world’s exploitable offshore wind resources has placed th estimates around 22 TWa’ (Arent et al., 2012) which is approximately nine time greater than the International Energy Agency’s (IEA) 2010 estimate of average globa electricity generation (IEA, 2012). According to a report by the United State National Renewable Energy Laboratory (NREL), offshore wind resource potential fo contiguous United States and Hawaii for annual average wind speeds greater tha 7.0 m/sec and at 90 m above the surface is 4,150 GWa (Schwartz et al., 2010) Similarly, a report by the European Environmental Agency (EEA) calculated th technical offshore wind power potential, based on the forecasted costs o developing and running wind power projects in 2020 at 2,850 GWa (EEA, 2009). Thi figure does not account for spatial use conflicts in developing the wind resourc offshore. As of 2012, large-scale commercial offshore wind projects and demonstration-scal or pilot projects are already operational in the Belgium, China, Denmark, Finland Germany, Ireland, Italy, Japan, Netherlands, Norway, Portugal, Republic of Korea Spain, Sweden, United Kingdom of Great Britain and Northern Ireland and Unite States of America (EWEA, 2008; RenewableUK, 2010; 4C Offshore, 2013; WWEA 2014). Currently, the North Sea region is considered to be the global leader i offshore wind, both in installed and planned capacity and in technical capability. B the end of 2013, the offshore wind industry has achieved a cumulative globa installed capacity of 7,357 MW (WWEA, 2014). Offshore wind turbines can be eithe bottom-mounted or floating. Currently, most offshore wind projects are bottom mounted; floating wind turbines are still in the demonstration phase. Moreover most installations are near the shore in relatively shallow waters due to the higher * TWa: The average number of terawatt-hours, not terawatts, over a specified time period. Fo example, over the course of one year, an average terawatt is equal to 8,760 terawatt-hours, or 2 hours x 365 days x 1 terawatt. © 2016 United Nations cost of transmission cabling further offshore, and due to the technical and economi challenges of installing turbines in deeper waters. Figure 1. Photo credit: Principle Power. The WindFloat Prototype (WF1) floating wind turbine deployed by Principle Power in 2011, 5km off the coast of Agucadoura, Portugal. The WF1 is outfitte with a Vestas v80 2.0 MW offshore wind turbine. As of December 2015, the system has produced i excess of 16 GWh of renewable energy delivered to the local grid. 2.2 Wave Energy Capacity The global exploitable wave energy resource is estimated at around 3,700 GW (M@grk et al., 2010), which is large enough to meet the average global electri generation (IEA, 2012). Wave energy can be harnessed using either floating or fixe conversion devices. Floating devices convert the wave energy by coupling it to hydraulic system as the device is lifted up and down by the movements of the waves Fixed devices generally use the oscillating water column generated by the wave t push air (or water) through a turbine. Other types of wave energy technology, suc as overtopping devices and attenuators, are also undergoing testing an demonstration. The world’s first grid-connected wave energy device, a 500 kW unit in Scotlan (United Kingdom) called the Islay Limpet, has been operating successfully since 200 (UKDTI, 2004). The Agugadoura Wave Farm, the world’s first utility-scale wav energy project, was launched off the coast of Portugal in September 2008. Thi installation, developed by PelamisWave Power, utilized three 750 kW devices with total capacity of 2.25 MW (RenewableUK, 2010). The project operated for tw months before technical problems forced the developers to abandon it. © 2016 United Nations Figure 2. Waves4power OWC plant in operation offshore Sweden (Reprinted with permission fro Waves4power AB). 2.3 Tidal Energy Capacity The global tidal energy resource is estimated to be 3,000 GWa by the World Offshor Renewable Energy Report 2004-2008 (UK DTI, 2004), however, less than 3 per cen of this energy is located in areas suitable for power generation. Tidal energy i feasible only where strong tidal flows are amplified by factors such as funneling i estuaries, making it highly site-specific (UK DTI, 2004). Traditionally, tidal energy ha been harnessed using large barrages in areas of high tidal ranges. Many countries such as Canada, China, France, Republic of Korea, Russian Federation and the Unite Kingdom have sites with large tidal ranges that are viable for tidal energy captur facilities. The Sihwa Lake Tidal Power Station in the Republic of Korea, which ha been operational since August 2011, is the world’s largest tidal power barrage with capacity of 254 MW, surpassing the 240 MW Rance Tidal Power Station in France which has been generating power since 1967. Numerous projects have also bee proposed in other areas, including in the Severn Estuary in the United Kingdom (Hall 2012). As part of its technology development initiative, the United States Department o Energy (US DOE) has funded research into several new types of technology, includin a turbine under development by Verdant Power Inc. Verdant Power was the firs company in the United States of America to be granted a license for a commercia tidal energy project, and looks to build upon an earlier demonstration project in Ne York’s East River with an installation of up to 30 turbines along the strait tha connects Long Island Sound and the Atlantic Ocean in the New York harbour. © 2016 United Nations 2.4 Ocean Current Energy Capacity There are no commercial grid-connected turbines currently operating, although number of prototypes and demonstration units are under development. In 2014 the United States Bureau of Ocean Energy Management (BOEM) issued a lease t Florida Atlantic University (FAU) for testing ocean current turbines. FAU’s Southeas National Marine Renewable Energy Center (SNMREC) plans to deploy experimenta demonstration devices in areas located 10 to 12 nautical miles offshore Florid (Bureau of Ocean Energy Management, 2014). 2.5 Ocean Thermal Energy Conversion (OTEC) Capacity OTEC technologies have been tested as early as the 1930s. However, OTEC has bee limited to small-scale pilot projects, and has yet to encourage much investment an commercial development (US DOE, 2008). Research initiatives in the France, India Japan and United States of America and elsewhere are currently examining an testing different types of OTEC technologies (Lockheed Martin Corporation, 2012). modern-type, but very small OTEC plant was constructed in Hawaii, United States, i 1979 (Kullenberg et al., 2008), and similar demonstration projects have bee proposed by other nations (IOES, 2015). Most experience is derived from land-base plants. For floating installations, reference material is mostly derived from desig studies, but with successful demonstrations in Hawaii (MiniOTEC, OTEC-1) an Okinawa, Japan (OTEC Okinawa, 2014). 2.6 Osmotic Power Capacity The world’s first complete prototype osmotic power plant was launched in Norwa in 2009 by Statkraft. This plant is located in Tofte, southwest of Oslo. According t the company’s assessment, osmotic-power technologies remain several years awa from commercial viability (Kho, 2010). Statkraft recently (2014) decided to shelv development plans. 2.7 Marine Biomass Energy Capacity Research into algae production has largely been guided down three tracks: open an covered ponds, photobioreactors, and fermenters; the first two are the most widel pursued. Siting algae farms in ocean areas has also been investigated (Lane, 2010). I the United States, the National Aeronautics and Space Administration (NASA) i investigating the feasibility of growing algae in floating photobioreactors on th outer (geomorphic) continental shelf or in the open ocean. The Offshore Membran Enclosures for Growing Algae (OMEGA) system would use freshwater algae an wastewater in the photobioreactors to produce biofuel while also cleanin wastewater, creating oxygen, and providing a sink for carbon dioxide (NASA, 2012) As the technology is developed further and States with favourable growin conditions begin to look towards marine renewable energy, this option may becom commercially viable in the future. © 2016 United Nations 3. Environmental Benefits and Impacts from Offshore Renewable Energ Development Marine renewable energy installation and generation invariably has environmenta impacts, both positive and negative. These impacts depend on the installation siz and footprint, location, and the use of specific technology. A major positive impact o ocean renewable energy is the provision of low-carbon electricity. Analysis suggest that the carbon intensity of offshore wind and marine hydrokinetic resources, suc as wave and tidal power, is more than an order of magnitude lower than fossil fue generation. In a life cycle analysis, greenhouse gas emissions from wave energ projects average between 13-50 gCO2eq/kWh?, tidal current projects emi approximately 15 gCO,eq/kWh, and offshore wind projects between 4- gCO2eq/kWh (Raventos et al., 2010); these are to be compared with emissions close to 800-1000 gCO2eq/kWh for coal power plants and 400-600 gCO2eq/kWh fo natural gas power plants (POST, 2006 and 2011). Other environmental benefits include no emissions of toxic air or water pollutant (such as NO, [Nitrogen dioxide], SO, [sulfur dioxide], mercury, particulate matter and thermal pollution from cooling water discharge) and minimal land-us disturbance with the exception of land-use changes related to assembly, equipmen loading/offloading and cable landfalls along the coast. In addition, there ar potential biodiversity benefits from the installation of offshore turbines or marin energy conversion devices. Offshore renewable energy (ORE) structures increase th amount of hard substrate for colonization and provide marine organisms wit artificial reefs. Such structures also create increased heterogeneity in the area: this i important for maintaining species diversity and density (Langhamer, 2012) Investigations have found greater fish abundance in the vicinity of offshore turbine compared to the surrounding areas (Wilhelmsson et al., 2006). One negative impac is that invasive species can find new habitats in these artificial reefs and possibl adversely influence the native habitats and associated environment (Langhamer 2012). The broader environmental impacts from marine renewable energy can b understood in the context of an ecological risk assessment framework developed b the United States Environmental Protection Agency (EPA). This approach provides conceptual model for developing a systematic view of possible ecological effect (McMurray, 2008). The terminology needed for this model requires definin stressors and receptors. Stressors are features of the environment that may chang due to installation, operation, or decommissioning of the facilities, and receptors ar ecosystem elements with a potential for some form of response to the stressor(s (Boehlert and Gill, 2010). Stressors can be considered in terms of different stages o development (survey, construction, operation, and decommissioning) as well as th duration, frequency, and intensity of the disturbance. Project size and scale are also 2 gCO2eq/kWh : grams of CO, equivalent per kilowatt hour of generation. © 2016 United Nations determining factors in the magnitude of stressors and receptors. Within thi framework, we discuss various ecological impacts in the following sections. Potential negative impacts on flora and fauna including marine mammals, birds, an benthic organisms, as well as impacts on the larger ecosystem may occur fro offshore renewable energy (OREI) development. Some of these impacts are limite to the construction phase, while other impacts span operation and decommissionin phases (Linley et. al., 2009). Potential impacts include habitat loss or degradation a various stages of a project life cycle; injurious noise and displacement of marin mammals from pile driving of wind and tidal-stream generators. Tide powe turbines may also induce local seabed scouring and/or changes to the curren regime, with unintended consequences for biota. Turbine construction may induc mortality due to physical collision with the ORE! structures; effects of operationa noise; and electromagnetic field (EMF) impacts from submerged cables (U.S Department of Interior, 2011). Noise created during pile-driving operations involves sound pressure levels that ar high enough to impair hearing in marine mammals and disrupt their behaviour at considerable distance from the construction site (Thomsen et. al., 2006). During pil driving for the Horns Rev II offshore wind project in Denmark, a negative effect wa detected out to a distance of 17.8 km (Brandt et. al, 2011). Although it has bee observed that marine mammals temporarily abandon the construction area, the tend to return once pile driving operations cease. Acoustic impact on marin mammals is a major concern and an important topic of assessment and mitigatio strategies in many States. More information is required almost everywhere t understand impacts on and responses by marine organisms to such stresses. Fixed and moving parts of Ocean Renewable Energy (ORE) devices can lead to fata strikes or collisions with birds and aquatic fauna. Blades used in marine turbines such as those in ocean current or tidal energy devices, are relatively slow-movin and therefore not considered to pose a significant threat to wildlife (Scott an Downie, 2003). However the speed of the tip of some horizontal axis rotors could b an issue for cetaceans, fish, or diving strike birds (Boehlert and Gill, 2010). Operatio of the SeaGen tidal energy device in Strangford Lough, United Kingdom, considere the presence of seals and porpoises and the potential threat of blade strikes; t minimize strike risk, the turbine was shut down when the presence of seals wa observed within 30 meters (Copping et al., 2013). Similarly, investigation of long tailed geese and ducks in and around the Nysted offshore wind project in Denmar suggests that flocks employ an avoidance strategy. Research suggests that th percentage of flocks entering the wind project area decreased significantly from pre construction to initial operation. Overall, less than 1 per cent of ducks and gees migrated close enough to be at any risk of collision (Desholm and Kahlert, 2005). Thi avoidance strategy or adjustment of flight paths, a form of receptor, has also bee observed in other projects, such as Horns Rev (NERI, 2006). It is important t highlight that the additional distances travelled by migratory birds to avoid thes wind farms were relatively trivial (around 500 m) compared to their total migrator trajectory of 1,400 km. However, construction of further utility-scale projects coul have a cumulative impact on the population, especially when considered i combination with other human actions (Masden et. al., 2009). © 2016 United Nations Submerged cables carrying electricity from ORE devices to onshore substations emi low-frequency Electric and Magnetic Fields (EMF). Marine and avian species ar sensitive and responsive to naturally occurring magnetic fields; these are commonl used for direction-finding using the Earth’s geomagnetic field. Anthropogeni sources of EMFs are an overlay to naturally occurring sources, and as these source become increasingly common, there are potential impacts on marine organisms Industry standards for the design of submarine cables require shielding, whic restricts directly emitted electric fields, but cannot shield the magnetic fiel component of EMFs (Boehlert and Gill, 2010). Moreover, an alternating current (AC magnetic field has a rotational component that induces an additional electric field i the surrounding environment. There is evidence that EMF’s from wind farms ca cause disturbance to air traffic control radar systems (De la Vega et al., 2013). Magnetic fields are strongest over the cables, decreasing rapidly with vertical an horizontal distance from the cables. In projects where the electric current i delivered along two sets of cables that were separated by at least several meters the magnetic field appeared as a bimodal peak (Normandeau et al., 2011). Studie suggest that behavioural effects of EMF on species occur, although the impacts var significantly among species. Thermal aspects of electricity-transmission cables should also be considered. Whe electric energy is transported, a certain amount is lost as heat, leading to a increased temperature in the cable surface and subsequent warming of th surrounding marine environment (Merck and Wasserthal, 2009). Temperatur changes can affect benthic organisms, although data on measureable impacts ar sparse. Increased temperatures can also attract marine organisms, exposing them t a higher amount of EMF radiation. In addition, there are other potential impacts such as chemical effects from potentia spills or leaching of anti-fouling paints from ocean renewable energy device (Boehlert and Gill, 2010), or impacts on benthic creatures and certain fish specie which have not yet been fully investigated and assessed. Many such effects ar localized, depend on marine and avian biodiversity in a region and can b understood only through comprehensive site-specific environmental impac assessment. Substantial work is proceeding to gather and disseminate availabl information and data on ecological impacts of ocean energy devices. Th International Energy Agency-Implementing Agreement on Ocean Energy System (OES) Annex IV? is maintaining the Tethys database, an important reference for bot developers and policy makers (http://tethys.pnnl.gov/). 4. Socioeconomic Benefits and Impacts from Offshore Renewable Energ Deployment 3 Annex IV. Assessment of Environmental Effects and Monitoring Efforts for Ocean Wave, Tidal an Current Energy Systems, Tethys.pnnl.gov. © 2016 United Nations 1 Socioeconomic impacts cover a range of issues, including access to the ocean, visua impacts amenity, impact on coastal and offshore cultural heritage sites, and othe uses of the ocean, including recreational tourism and fisheries, related to offshor renewable energy sites. In many regions, these issues have been examined withi the context of comprehensive marine spatial planning. Marine spatial plannin provides an understanding of the extent to which certain activities take place in a area identified for offshore renewable energy development and provides a baselin assessment of critical ecological and cultural sites. Sociological surveys of coastal residents, ocean users and other stakeholders hav been widely used to assess perceived and experienced impacts from offshor renewable energy facilities. Survey results from two operational offshore win projects in Denmark, Hons Rev and Nysted, indicate a generally positive attitud among coastal residents (Ladenburg et al, 2006). Relative open access to the project for marine resource extraction could be a reason for high levels of public approval o the projects. Also, the visual impact of the installations may not have affected thos people who were surveyed, since wind farms have caused a loss of amenity in othe areas (see below). Both the projects provide access to sailing and fishing within thei waters. The Nysted offshore wind project provides access for fishing with net an line, Horns Rev allows only line fishing, and bottom-trawling fishing is prohibited i both projects. Fishing can be further restricted as setting of lobster traps may b limited near cables and turbines. Wave, tidal power, and ocean current energ sources have not yet been commercially deployed at a large enough scale to enabl an assessment of potential socio-economic impacts. The effect of impaired visual amenity from ORE deployment can affect propert prices, result in loss of recreational value, and reduce demand for tourism in coasta areas. It can also affect historic and culturally significant resources. These impact are expected to be more prominent for an offshore wind project than for a wave tidal, or ocean current installation, as the latter will be underwater and of smalle scale, for similar capacity. Research in the United Kingdom, England and Wales which have extensive offshore wind capacity, concludes that offshore wind project have a measureable impact on property prices. The impact is more pronounced i areas which are closest to the wind projects. On the other hand, a small increase i housing value is also seen in areas where wind projects are not visible, indicating potential economic benefit to landowners near non-visible wind project operation due to an increased rental rate (Gibbons, 2014). This latest assessment is consisten with earlier published studies, which strongly suggest that, given a choice consumers prefer offshore wind projects sited away from the coast and, in som cases, completely out of sight (Ladenburg and Lutzeyer, 2012). Utility-scale offshore renewable energy projects can use significant ocean space an impose restrictions for navigational purposes. A large project, if placed along a existing navigational route, can increase the distance that ships and boats would b required to travel. The extent of transit through offshore renewable energy project depends on safety issues and ease of access. In Denmark, transit through offshor wind energy projects is possible via certain routes; in Germany, navigation is allowe as close as 500 meters (Albrecht et al., 2013). The International Association o Marine Aids to Navigation and Lighthouse Authorities has promulgated © 2016 United Nations 1 recommendations on how to mark different types of offshore renewable energ installations so that they are conspicuous under different meteorological conditions This, along with proper charting of installations and associated cables, can limi navigational risks (Detweiler, 2011). Planning, construction, and maintenance of offshore renewable energy operation have the potential to create direct and indirect employment in various sector including manufacturing, construction, operation, and maintenance. In 2013 offshore wind represented 3.6 per cent of the United Kingdom’s electricity supply contributed close to 1 billion United Kingdom pounds to the economy and supporte 20,000 jobs, including 5,000 direct jobs (Offshore Renewable Energy Catapult, 2014) As the industry continues to grow, it has the potential to add thousands of new jobs not just in the United Kingdom, but around Europe and other parts of the world tha form a critical link to the supply chain. In Europe, offshore wind energy and ocea energy create 7-9 job-years/MW‘ during construction and installation. In addition offshore wind projects can generate up to 11 job-years/MW in manufacturing, an 0.2 jobs/MW for operation and maintenance during the operational years of project. These figures are comparable to those for conventional sources like coal although offshore wind and other marine renewable sources have no job-creatio potential related to fuel extraction, processing, and transportation for the life of project (Energy [rJevolution, 2012). Above and beyond the employment generation factor, offshore renewable energ also offers other intrinsic economic and electrical system integration benefits. Fo instance, many offshore renewable energy projects are sited, or proposed, close t densely populated coastal areas. Proximity to major electrical load centres ca significantly reduce the cost of transmission and offset transmission congestion Moreover, ocean renewable sources, particularly offshore wind power, offers th additional value proposition of load coincidence in many regions (Bailey and Wilson 2014). 5. Offshore Renewable Energy Assessment Capacity Gaps A capacity gap is a lack of information that, if available, would or could identif whether environmental effects [of a project] will have substantial negative impact (McMurray, 2012). In many regions, sufficient knowledge exists in the near-shor and offshore waters to provide an initial baseline assessment, although it is ofte insufficient to provide a site-specific impact assessment. Significant capacity gap exit in assessing environmental, social, and economic impacts from deployin devices in the marine environment. Most forms of ocean renewable energies hav still not reached commercial scale, although some are at a high Technologica Readiness Level (TRL). * Job-years per MW denote the total amount of labour needed to manufacture equipment o construct a power plant that will deliver a peak output of one megawatt of power (The Energy Polic Institute, 2013). © 2016 United Nations 1 Certain marine environments and species present additional challenges i addressing capacity gaps. For instance, it is technically difficult to obtain informatio on benthic biota, as compared to species in the pelagic zone. Due to the lack of high quality benthic information, resource managers and developers are often require to conduct time-consuming and resource-extensive surveys before siting decision can be finalized. In the pelagic zone, marine migratory species pose additiona challenges for site characterization. Further site-specific research is required t understand migratory species such as whales to ensure that project siting ha minimal impact on migratory routes or traditional foraging grounds. Similarly impacts on avian species in the offshore environment, particularly migratory bir species and bats, have not been fully understood and require further research an assessment. In the absence of operational utility-scale projects, it is often difficult to determin the socioeconomic impacts of an emerging renewable energy technology. One wa to address such capacity gaps is to make long-term monitoring an integral part of th construction and operation phase, though if long-term monitoring regimes are to costly developers may be dissuaded from pursuing commercial projects. Studies an surveys assessing impacts before and during the operation of a project can provid valuable information on impacts, and can suggest substantive mitigation measure to address those impacts. The knowledge and capacity gaps should be addressed within a comprehensiv framework that considers all ecological resources and human uses in an area. Thi framework, also referred to as marine spatial planning, provides a process fo analysing and allocating spatial and temporal distribution of human activities i marine areas to achieve ecological, economic, and social objectives that are usuall specified through a political process (UNESCO, 2014). States are increasingly usin marine spatial planning as the tool for identifying and siting offshore renewabl energy projects. More importantly, the collaborative processes at the heart o marine spatial planning foster relationships and linkages among ocean uses stakeholders and resources managers to enhance the quality of scientifi information and traditional knowledge available. This collaboration and informatio exchange can lead to better-informed siting decisions and can minimize social an environmental impacts. 6. Conclusion Offshore renewable energy is an immense resource awaiting efficient usage Technological progress to harness the resource is steadily increasing around th world. When fully developed and implemented, ocean renewable energy ca enhance the diversity of low-carbon energy options and provide viable alternative to fossil fuel sources. For developing countries and new growing economies installing renewable energy systems represents a viable path towards a low-carbo future. © 2016 United Nations 1 To achieve a commercial break-through such that ocean renewable energy become cost-competitive, many governments have funded Research and Development (R&D projects and provided financial support for technological developments an demonstrations within this sector. Traditional commercial funding sources are ofte insufficient to achieve this goal in the long-term, so innovative strategies ar required. 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