local conditions. Only offshore wind and to a lesser extent tidal range technologies have been developed to commercial scale, primarily in Europe where policy and investment frameworks are favourable. Many technologies that harness energy from waves, currents and temperature differentials have been developed at pilot stage, but without convergence on a single design type, and very few have been developed to a commercial scale.
Marine-based renewable energy can provide alternative employment opportunities particularly for maritime communities who were formerly reliant on fisheries or oil and gas production. Compared with thermal power generation, renewable energy has a higher labour intensity. The types and scale of opportunities will vary by national context and energy source. Lack of skilled labour is one of the potential barriers to deployment of renewable energy.
Marine-based renewable energy can provide an alternative electricity supply for oil-
Ocean energy potential Terawatt-hour per year
Wave 80 000 10 000
18 000 37 000
Present global electric production
Offshore wind (max)
300
Thermal gradient
4 000 2 000 Salinity Gradient 800 Marine current Tidal
Tidal, stream Tidal, barrage
Solar
Energy production costs Euro cent per Kilowatt-hour
Coal Nuclear
Biomass, heat
Wind, onshore
Geothermal, heat
Wind, offshore
Gas Ethanol
Biomass, electric Solar, thermic
Wave Hydro small
Hydroelectric, large
Geothermal, electric
12 11 10 9
8 7
4 5 6
3 2 1 0
Consistent long-term policies and targeted financial support from governments are needed if technical barriers and cost reductions are to be overcome. Governments need to lead the way by establishing consistent renewable energy policies, including specific targets for marine-based renewable energy where possible. To implement this, incentives such as grants, subsidies and tax credits are required to encourage private investments in the large, expensive infrastructure that is required to move from small prototypes to pilot plants.
Governments need to proactively guide developments to reduce potential for social, environmental and legal conflicts and promote synergies with other sectors. Governments may play a key role in proactive strategic marine planning to offer concessions in areas with lower risk to ecosystems and biodiversity and to promote synergies with other marine users.
13
Offshore wind (min)
importing
countries. Developing countries
that spend large amounts of their export revenues on oil imports can benefit from an alternative electricity supply to improve national and regional energy security, as well as water and food security when used directly for desalination.
Without accounting for negative
externalities, marine-based renewable energy is not yet cost competitive; only offshore wind is close to being cost competitive with fossil
fuel and nuclear sources. There
are many challenges to be overcome before marine-based renewable energy technologies can reach large-scale commercialisation; these include high capital costs and the logistics around storage and transmission.
Global environment benefits of reduced greenhouse gas emissions need to be balanced against local environmental risks and opportunities. For most marine-based renewable energy types, the greatest negative impacts on biodiversity
occur most likely
during construction and decommissioning due to noise and habitat disturbance. During operation, moving parts can affect birds, fish and sea mammals. However, if ecologically sensitive sites are avoided and best practice employed, there could be positive benefits for the marine environment, such as through the creation of appropriate artificial habitat and the reduction of other adverse activities in the area. As relatively little is known about more recent technologies, new developments need to be accompanied by appropriate monitoring and evaluation as part of environmental impact assessment procedures.