Mike4 wrote:Tidal power unlike wind, never stops. I'm unclear why we have not gone hell-for-leather for tidal from the get-go. High and low tides even happen at different times around the coastline!
Well most forms of tidal energy do come to a complete stop, every 6 hours - and although distributing it around the coastline helps, the good spots are not evenly distributed. I see a lot of demand for seabed 3-hours-tide away from the huge resource in the Pentland Firth though.
The short answer is that tidal is just A Lot More Difficult than wind, and so it's a lot more expensive. The wind guys could work out the kinks on dry land, with easy, 24/7 access by LandRover and no need to marinise the kit. Then moving offshore, although they needed foundations in the sea, all the delicate bits were at least out of the water (most of the time). Whereas tidal power has to be actually in the sea, which has implications for everything from maintenance (you can only access it for 40-60 minutes of slack water as the tide turns) to how robust even the "delicate bits" have to be - the higher density of water makes it a lot more destructive than air.
So it's expensive, and there's not been much experience elsewhere in the world that we could lean on here, whereas our offshore wind has benefited from technology proven in Denmark etc. And so when tidal came to compete with offshore wind for subsidy, it just couldn't really. But now that wind has gone through the subsidy system and no longer needs them, tidal has a better chance of attracting subsidies. Specifically, industry was told that there would be subsidy for 100MW of tidal guaranteed in the bidding rounds between 2015-20, with an initial price set at £305/MWh although nobody was ready then, but the success of offshore wind meant that the budget was overspent and so Greg Clark pulled the tidal guarantee. But to give you an idea, Atlantis (SAE.L) are probably the furthest along and they have just won rights to 28MW of tidal at £178.54/MWh (which won't go live until 2027), with 3 other projects accounting for 12.82MW. Current target is 1 GW tidal deployed by 2035.