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What is... Wave and Tidal Energy?

Updated: Sep 15, 2020

Wave and Tidal Energy are two renewable energy sources that fall into the Ocean subcategory of Hydro Energy. Wave Energy is the energy carried by the swells on the surface of large bodies of water. Tidal Energy is the energy involved in the natural rise and fall of ocean tides and currents.

Why is Wave & Tidal Energy Important?

Currently, Wave & Tidal Energy isn’t the cheapest form of green energy and, as the technology is not widely used, the true implications on the environment are not yet fully understood. However, the waves and tides present huge potential for generating renewable energy and are accessible for much of the world - not just the oceans, but any large bodies of water. With 2/3 of the surface of the Earth covered in water, waves and tides represent a vast untapped natural resource with immense amounts of energy available to harness.

Water is about 800 times denser than air, this means that more power is available per square metre. In turn, this means that installations can be smaller (in area) than Wind or Solar developments. The largest installation of tidal power worldwide is Sihwa Lake Power Station in South Korea at 12.5km long, which was retrofitted to a pre-existent sea wall built to stop coastal flooding. The Sihwa Lake Power Station has a total power output capacity of 254MW. Compared with that of Wind Farms, Roscoe Wind farm in Texas is roughly 400km2 with an installed capacity of 781MW.

Another benefit is the predictability of the tides. Tides are the cyclic rise and fall of the water caused by the moon's (and other celestial bodies) orbit around the Earth. The motion of these celestial bodies is well recorded meaning we can predict tidal cycles, and therefore energy production, years in advance. This predictability also means that it is easier to design systems, as cyclical systems are far easier to engineer than random systems such as wind velocities or solar flux.

UK Potential

The UK has huge potential for development due to the fact it is an island. The best wave potential occurs in areas where winds have travelled a long distance (the fetch) meaning bigger waves can be formed. Waves can also be funnelled between islands which can increase the energy they can provide.

Currently, UK tidal resource estimates are sitting at around 10GW, one of the highest in the world, roughly 50% of Europe’s potential. The potential for Tidal energy is greatest where the largest tidal ranges occur - the UK has the 2nd largest tidal range in the world in the Severn Estuary (the largest is in the Bay of Fundy in Canada with a range of over 16m!). This again is due to funnelling and amplification of the tides by islands and estuaries.

Currently it is largely governments investing in Wave & Tidal however with demonstrator projects popping up all over the UK, there could be a soon increase in the number of organisations investing. The main barrier in Wave and Tidal power plants is cost of installation, however, marine energy has an extremely low operation and maintenance cost.

Investing in the Future

While the idea of harnessing the power of the waves and tides is not a new one, the levels of investment from governments and industry in developing these schemes has not matched the levels invested in other renewable energies such as wind or solar. As such, this technology is still in its infancy, with increasing research and development, it is expected that ever larger installations will become feasible and the cost of these schemes will reduce.

Graph showing levels of investment in renewable energies (BloombergNEF)

Next week we will look into the technologies used to generate Tidal Energy.
This article is part of a series explaining some of the key technologies that are enabling the energy transition. Click Here to see the full series.
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