Tidal Power: The pros and cons

  In bygone times, the United Kingdom was industrious and found solutions to problems from its own resources. For power there was bounteous amounts of coal, then there was North Sea oil (and gas). This country has overwhelming natural resources. We do use some of these, we could exploit a lot more.   

  To give just one example, we could exploit other natural resources. At least a quarter of the world’s Tungsten reserves are to be found here. Lead, zinc and silver deposits are in mines all over the Northern Pennines. Large quantities of rare earths such as Neodymium and Thorium are found in the Monazite sands that are abundant throughout mid-Wales. Some of Marie Curie's radium came from Cornwall, where the uranium mines were all closed in 1937. Yet almost no  metals are mined today despite these vast and well catalogued deposits.

They are, in fact, ignored.  

We have a tradition now of ignoring our own capabilities and looking to others.  

  So it is with tidal power. This resource is also ignored, despite the way forward having been revealed by the Victorians. This was the development of dry docks – big holes in the riverside banks into which ships were manoeuvred and grounded as the tide went out. Once on the bottom the outer gates were closed, remaining water pumped out and work could begin on the hull or propellers or the rudder. A dry dock is 200 year old technology and is almost indestructible. 

  The amount of water flowing in and out as the tide rises and falls is substantial. Allowing a space like a dry dock just to fill and empty through a turbine could generate a lot of electricity. Basically, letting a hole in the ground fill and empty as the tide comes and goes.    

  Not just dry docks. There are similar sites all around the UK; industrial settling ponds and the sites of former salt panning operations as well. Former chemical works and loading stations for ships. Substantial areas of brownfield land.        

  The pros are ease of use and economy, that there is plenty of potential land available and it is usually near centres of population. This means that the cost of sending the electricity from the point where it is made, to the point where it is used, is negligible. The cost of decommissioning is negligible as well. The unit could just be sold to a fish farm. Operation can be arranged to operate continuously, the only environmental energy source that can do so. All day, every day. There are other uses the turnover of cold water could be put to.  Dry docks are simple and have around a 200 year lifetime.

  There are many gigawatts available.

  The cons are that tidal power on its own is only marginally viable unless carried out on a large scale, although this statement is made looking at buy-in prices for electricity at around £50 per MWh, and without any subsidy involved. As the buy-in price increases the viability improves. And there are "other things" we can do on these sites, valuable things, that in fact make the generation of electricity a by-product. 

  Another "con" is the well known reluctance to embrace new ideas in the UK. There are suitable turbines but they are expensive and only work in one direction, so better ones need to be developed. We have a plan to do this. Some of the output will be modest, maybe as low as 20 - 30 megawatts, but it is continuous. There will be an issue with silt, which will build up and will need to be periodically cleared out.

  It is cheaper in the short term to simply build houses on the land. Cheapest options are almost always selected. Tidal basins are a strategic development, but a lot of the cost of construction can be recovered by dual use applications  in which the site construction costs are fully recovered by another application and, as mentioned above, the electricity produced becomes just a by-product.