Guest Blog: The rise and fall (and rise again) of tidal power in the Severn Estuary – but still nothing built
08 Mar 2017
A tidal lagoon in Swansea Bay featured in a report by former energy minister Charles Hendry last year. Alexander Portch, University of Bristol, who has been studying the history of such projects, charts the ups and downs of enthusiasm for tidal energy.
The publication late last year of Charles Hendry’s report on tidal lagoons (particularly the proposed Swansea Bay tidal lagoon) marks, when looked at in historical terms, simply the latest instalment in a long line of reports and investigations on the topic of tidal barrages and lagoons around the UK coast. Due to its exceptional tidal range (the second highest in the world after the Bay of Fundy, Nova Scotia), the Severn Estuary has received most attention. With the exception of an experimental tidal stream turbine near Lynmouth, North Devon, however, nothing has actually been built.
Initially conceived in the 1840s to improve navigation to upper-estuary ports and function as an England-Wales transport link, by the first decade of the twentieth century a barrage across the Severn had been proposed to convert the Estuary’s tidal energy into electricity. This would supply growing demand in industry and for lighting.
Subsequently, barrage schemes were proposed by independent speculators, with occasional government reviews, most notably in 1933, 1945 and 1981. Official reports were generally favourable, but all called for further technical research and investigation into potential impacts.
Barrage promoters in the early twentieth century highlighted the potential to reduce reliance on polluting and finite supplies of coal, and later oil, and the prospect of stimulating the development of new industries and construction of ‘smokeless’ cities. Opponents countered with concerns over implications for estuarine navigation, commercial and recreational fisheries, and its high capital cost. In the late twentieth and early twenty-first centuries, opposition has centred on the potential loss of intertidal habitat for wild birds, threats to migratory fish, and the predicted loss of the world famous Severn Bore
Today, only a handful of tidal barrages exist around the world, and all have been built as prototypes with no large-scale schemes ever taken beyond the design stage. The output of La Rance tidal barrage in France, for example, is small (about 240 MW), while Sihwa Lake in South Korea is 254MW.
This brings up the alternative, but not always historically separate idea of a lagoon, whereby seawalls are used to artificially impound water within a defined area, from which it flows in and out with the tide through turbines.
Lagoons also have a history on the Severn, having been suggested as a smaller-scale alternative to full-size barrages since at least the late 1970s.
In many respects, lagoons closely reference the millponds of tidal mills, a technology present in the British Isles since the eighth century. Tidal mills in the UK were never particularly massive, but examples in the USA, and northern France were not insubstantial. Importantly, they were actually constructed and operated, particularly around the Atlantic coasts of Europe and North America, with some as far afield as Australia and South America.
Alexander Portch is a Postgraduate Researcher in the Department of History, University of Bristol, researching the history of tidal energy in the Severn Estuary. Alexander also directs your attention to the Power and Water project, funded by the Arts and Humanities Research Council.