What is the potential for tidal power to supply carbon free energy to a world desperate to throw off the shackles of fossil fuels?

You would expect the potential to be huge because there are tides every where, right.

The answer may surprise you!

Tidal Power Turbine

This is a photo of the 1.2 megawatt tidal turbine installation at Strangford Lough, Northern Ireland, raised out of the water for maintenance. The world’s first commercial scale tidal turbine.

In service now since 2008, it supplies electricity to some 1000 homes.

At an installation cost of 8.5 million UK pounds ($12.75 at today’s rate), that’s a whopping $10.6 million per megawatt!

Compare this to the typical installation cost of a 2 megawatt onshore wind turbine of $3.5 million, that’s only $1.75 million per megawatt.

And the typical installation cost of an offshore wind turbine of $3 million per megawatt, although this will vary depending on the site.

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Now we have the relevant costs, let’s go back to the potential of tidal power.

The total global energy in the tides is estimated at 3.5 terawatts, which sounds like a huge number, and is. But even as large as it is, this is only 20 percent  of total global energy usage.

But much of this occurrs in open oceans and is unusable, because to generate power efficiently the tidal current must have a speed of at least 1.2 meters per second. That leaves us with only 20 suitable sites world wide.

We are now reduced to a global potential less than 100 gigawatts.

That’s because currents of this speed are only present in certain shallow coastal waters.  However, due to the variability of the tides and the alterations to the tidal flow caused by the presence of the turbines, the potential is further reduced to only 10s of gigawatts.

Objections to tidal turbines has been growing, as an array of turbines across an estuary or channel, would substantially alter the marine ecology both up and downstream of the array.

However, Dr Graham Savidge of Queens University, Belfast has been monitoring the effects of the single turbine at Strangford Lough. He says,

“There has been very little impact really, it seems quite benign. However, when it started running we noticed passing Porpoises stopped communicating, but numbers have remained stable at the entrance and top of the lough.”

Perhaps this study will alleviate many of the worries of the objectors?

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If you would allow a personal note, I have to admit to being a little sceptical as to the potential of tidal power. Is a return of 1000 homes equivalent electricity sufficient for an investment of £8.5 million?

I would think not in today’s financial climate.

The UK government’s energy minister Lord Hunt has just launched it’s ‘Marine Energy Action Plan’, when he suggested that the UK’s coastal waters had sufficient tidal and wave potential to supply 15 million homes.

He’s having a laugh! Does he expect us to believe him?

Taking the Strangford Lough example where the 1.2 megawatt turbine supplied 1000 homes, it would need 15,000 turbines to supply 15 million homes, at a cost of £12.75 million each!

Put another way, we would need 15,000 turbines at 1.2 megawatts, totaling 18,000 megawatts. That’s 55 gigawatts of tidal and wave power, which would exceed the global potential?

While we all should embrace clean technology as a replacement for fossil fuels, we have to be sensible with it. It is also advisable to keep political hype and falsehoods out of such a critical sector.

Sincerely,

P.S. Let me know what you think about tidal power and the clean energy debate in general, by leaving a comment or submitting a story through the link in the page menu.

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