Reliability and Tidal Power

Nov 2021

My first blog looked at reliability from a distribution network and customer perspective, this time I consider reliability in terms of generation, network control and customer interests.

The story goes that when investment decisions were made on which renewable energy technologies to back, that tidal generation worked out at £350/MWh and wind generation at £200/MWh, so wind won most of the investment.

This decision does not appear to have taken reliability into consideration. Wind is an unreliable source of energy, as we have discovered this year to date. Therefore to guarantee 1 MW you need to install 2 MWs at different locations and hope that when one is dormant the other is operating. This is the same as 1 MW of reliable capacity and it has cost £400/MWh.

If we had invested in tidal, which it utterly predictable month after month for years in advance, then 1 MW built means 1MW available and it cost £350, saving £50. I am dealing in installed capacities, not power extracted from each installation, and power extracted is always smaller than the capacity installed but this applies to all generation not just tidal.

Tidal also suits our natural load cycle the highest tides are in the winter to suit the period of maximum demand.

No other country in the world is surrounded by tidal generation opportunities, the UK is. This is a unique global advantage which we should be maximising. It is like leaving your best player on the bench because you don’t like the risk.

Tidal generation by Atlantis Energy and Nova Innovation are working towards proving the technologies.  Atlantis Energy is working on the Pentland Firth Meygen project which has now 4 years of operational experience in the extreme conditions of the Pentland Firth.  It  has   exported 24.7GWh to the national grid by the end of 2019 from 4 x 1.5MW tidal stream turbines and extended periods of uninterrupted generation.   There are plans for many more on the site.

Nova Innovation have 3 x 100kW turbines installed in the Bluemull Sound in Shetland operational since 2017. Their production costs have fallen by 15% with a further reduction to 40% expected by 2022.

So we have large scale and small scale examples running.

The detractors argue about the intermittency of tidal, but that is not the point, from an operational point of view, control engineers know in advance when it will be available and it is reliable and can confidently include it in their generation scheduling plans.

Wind power can halve in a few minutes even when it is windy making for very erratic power flows in the network.  We should be doubling down on tidal investment to push it over the tipping point to business as usual generation.  We should be installing large and small tidal stream generation installations around our coasts and islands.

Reliability has either been ignored in this business case or totally underestimated.  The shortfall in rain, affecting hydropower, and low wind speeds has cost the UK customers billions in increased energy prices this year because we have had to buy gas to replace the missing hydro and wind power.

Sublime to the ridiculous, my energy supplier went bust, but I have a default supplier all seamlessly provided and working well. I learnt this week that 1kWh  of electricity which was costing me around 14p /kWh, is now going to cost me 21p.

Lets say 25% of UKs 2.8m customers face this same dilemma, that is 700,000 customers each using 3000 kWh on average per year costing an extra 7p per unit = £147m.

Also, the tax payer’s money is being politically burnt on the energy cap and it has risen from £1136 to £1277 a rise of £141. Let us assume this is applied to 25% of UK customers, 700,000 x 141 =   £98.7m

A proper analysis of the tidal generation business case would therefore have saved this country around £250m, which would have been welcome indeed as an investment in tidal energy.

It is not too late, we face the same price volatility year on year into the future. The energy cap cannot politically be scrapped, until the cost of renewable energy, and UK energy independence, frees us from market price variations.

As soon as we reach the situation where the cost per KWh from all renewable sources drops, because we are past the escalation stage and into a running cost and incremental replacement phase,  then the UK will enjoy relatively cheap energy because we do not buy wind, sun, rain or tide we can freely use it. Then our industry product prices become internationally competitive and we sell more and our economy grows.

Derek Macfarlane

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