Ebbing and flowing

Tweet Yesterday's announcement, effectively confirming that the largest scheme for harnessing the tidal power of the Severn estuary is still the front runner, was disappointing, to say the least. Sometimes, there seems to be something of an obsession in government with having dramatic single big 'solutions' to problems, rather than an acceptance that a range of smaller schemes might actually be a better approach.

Clearly, the tidal range of the Severn estuary makes it a prime candidate for harnessing the power which is available there, but I remain unconvinced that a dam across the whole estuary is the best way of doing that, not least because of the environmental damage that such a barrage would itself cause.

One of the problems for those of us who advocate more use of renewable energy is the potential variability in the supply. The advantage of tidal power, of course, is that it is almost entirely predictable – tides ebb and flow in a regular cycle. But that predictable cycle includes two high tides and two low tides every day, and that means that, for any scheme harnessing tidal power, there will be, to a greater or lesser extent, peaks and troughs in the flow of water (and therefore the power generated) each day.

However, around the coast of Wales, there is a 5-hour range in the time of high tide. A series of smaller tidal schemes around the coast would produce less electricity in total, but there would be a more constant supply. Of course, the flow of the tide is not as powerful in every location, which makes the Severn estuary a good place to start implementing tidal technology. But if we want to use renewable sources of energy as a replacement for base load, isn't maximising the use of that tidal range a better option than a single large scheme, which means that we would still need other sources to meet base load when the tidal flow is at its lowest?