![]() ![]() ![]() There are two methods of generating electricity from the tides: However, energy availability during neap tides is significantly less than that during spring tides, regardless of location. ![]() Since the tides are out of phase around the coast, power is likely to be available at one tidal installation while there is slack water and no tidal power available in another part of the country (Fraenkel 2002). As a marine renewable, tidal power deployments can be located in under-utilised locations (Fraenkel 2006), and so positioned out of sight and out of mind much more readily than large onshore devices, overcoming the so-called not in my backyard (NIMBY) problem that particularly affects wind power (Premalatha et al. Of the many varieties of renewable energy, tidal power is one of the few that is almost perfectly predictable over long timescales (Denny 2009). To achieve these targets, it is predicted that 30 % of UK electricity will need to be generated from renewable sources by 2020 (HM Government 2009), while the sector will need to be almost entirely carbon free by 2050 (HM Government 2011). Meanwhile, the UK Government has committed to legally binding targets to reduce carbon emissions by 34 % by 2020 and 80 % by 2050, as set out in the 2008 Climate Change Act (HM Government 2008). ![]() In Europe, the 2009 Renewables Directive set binding targets for all EU member states so that 20 % of EU energy will come from renewable sources by 2020 (European Parliament and Council 2009). Nations across the globe are turning towards renewables-low-carbon energy sources that can be replenished on human timescales-to meet their energy and electricity needs. Oscillating hydrofoils would also be appropriate, provided comparable levels of efficiency can be achieved. Cross-flow turbines appear to be the most suitable technology, as they have high power densities and a maximum size that is not constrained by water depth. The discussion suggests that tidal kites and range devices are not well suited toward small-scale shallow water applications due to depth and size requirements, respectively. This is achieved by discussing the power density, scalability, durability, maintainability, economic potential and environmental impacts of each concept. This article reviews tidal barrages and lagoons, tidal turbines, oscillating hydrofoils and tidal kites to assess their suitability for smaller scale electricity generation in the shallower waters of coastal areas at the design stage. If such generation is feasible, it could have the potential to provide sustainable electricity for coastal homes and communities as part of a distributed generation strategy, and would benefit from easier installation and maintenance, lower cabling and infrastructure requirements and reduced capital costs when compared with larger scale projects. This work is naturally focussed on maximising power generation from the most promising sites, and a review of the literature suggests that the potential for smaller scale, local tidal power generation from shallow near-shore sites has not yet been investigated. A considerable body of research is currently being performed to quantify available tidal energy resources and to develop efficient devices with which to harness them. ![]()
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