Marine energy is a renewable form of energy embodied in the motion of tides, currents and waves in oceans. The amount of energy within the oceans is huge, but it is not localised and requires large-scale infrastructure to harness. Marine renewable energy (MRE) offers the potential of a commercial-scale source of renewable energy. Waves, tides, ocean currents, salinity gradients, and temperature gradients are all viable energy sources for MRE technologies.
Tidal energy technology includes tidal stream generators and tidal barrages. Wave energy converters translate the oscillatory motion of waves into, first, mechanical motion and, then, into electrical energy. The five principal categories of wave energy devices are: surface attenuators; point absorbers; oscillating water columns; overtopping devices; and surge converters
Various tidal and wave energy converters were explored in relation to the viability of harnessing energy from tidal and wave resources at a study site in Tsim Sha Tsui, Hong Kong. The research focused on electricity generation from wave energy systems, and the practical constraints and energy efficiency of available systems. Two market-ready wave energy prototypes were identified for potential application at the study site in Hong Kong: a buoy system and an oscillating water column system.
Although estimates of the potential resource of renewable power within the oceans are typically of the order of petawatts per annum, in practice much of this power cannot be harvested.
Unlike diurnal tidal energy, wave energy can be produced throughout the day, albeit subject to weather conditions, and it does not require significant energy storage facilities.
The power that can be extracted from a wave using a wave energy conversion device is calculated as the power of the wave on entering the device minus its power on exiting the device.
A wave energy converter extracts the maximum possible power from a wave if it completely flattens the wave to still water (that is, zero wave height) without dissipating energy as turbulence.
Waterfront developments seeking prominent sustainability initiatives can benefit from the visibility and the practicality of marine renewable energy systems.
Applications include powering waterfront lighting and generating electricity to energise cathodic protection systems to combat corrosion of marine structures.
For remote locations, on-site generation of electricity eliminates the cost of electricity transmission to the site and transmission losses.
Site-specific aspects to be considered include vessel traffic, anchoring and the security of the cable connections between the wave device and the sea bed, and any local marine safety policies or constraints.
Better knowledge of marine renewable energy technologies supports growth of the industry and brings these technologies to market by improving efficiency of wave energy systems and by driving down costs.