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Hydropower

Obstacles to tidal energy in the UK.

Why haven't the forecasts for tidal energy been realised?

By Angela Robotham on 23rd Feb 2017

Tidal power or tidal energy is energy (potential or kinetic) obtained from sea tides which are converted into a useful form of power, mainly electricity. Whilst tidal energy at first glance has huge potential in future for electricity generation, it has unfortunately failed so far in obtaining a foothold into the energy mix supplied into the UK national grid. It is self-evident that the behaviour of tides is definitely predictable for many hundreds of years into the future but that of wind energy, when supplied by offshore wind farms, has a reasonable degree of consistency to the extent that it can be considered as base load capacity.  

Tidal turbines and wave energy converters have been under development for decades and have received considerable investment over that time. So why hasn’t the technology been rolled out to the extent predicted 10 years ago? Some forecasts made at the time predicted there might be hundreds of devices deployed by the end of 2019. No one, no matter how optimistic they are, would make that prediction now.

So, what happened – why didn’t these predictions materialise? Some will inevitably blame a lack of investment. To some extend this is true, but we need to ask ourselves why has the investment not been there? The answer is that investors, including governments, have realised that it’s just too difficult and that the number of sites suitable in terms of depth, tidal speeds, proximity to the grid and seabed conditions, and unencumbered by onerous SSSI conditions, is nowhere as great as claimed by the protagonists.

So why is it too difficult to be economically viable? Firstly, it must be remembered that the tides never stop. Every six hours or so there is a flood or an ebb tide. These can run at up to 10knots at some sites, although on average the majority of identified sites rarely exceed 5knots. The weather conditions on these sites is considerably more unpredictable than the majority of sites where wind farms have been deployed. Pinning a tidal turbine down to the sea bed, which at the majority of sites is hard and rocky, is extremely difficult. Drilling holes at the necessary diameters requires specialised equipment which has also to be held stationary during operation even when the tide is running and a storm is blowing. Gravity base systems need to be positioned accurately onto ground which is stable and level enough to receive them.

The practicality of the engineering is within our grasp, we know how to design them. We have built and operated devices which technically have been very successful. But the installation and deployment remains extremely challenging.

You can learn more about tidal energy and KGAL's capabilities here.

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