replace modules and then put them back in. we've also, over the years, removed more and more components from the system and fit them onshore instead. the less old components you have that could become damaged, it's easier to access it and it's much cheaper also. it's the gravitational pull of the moon and, to some extent, the sun, which gives the tides their rhythm. and unlike wind, solar or hydro, tidal power isn't reliant on weather. while tidal barrages have been around for decades, their cost and the ecological impact has been a barrier. now, from the scottish islands through to canada, a new generation of tech firms have introduced tidal stream turbines. 0cean energy is still largely untapped, so what are the barriers that have prevented it from taking off? it's a relatively small and new industry, so very few machines in the water, and then you have to compete with wind farms and solar pv, etc. we're now addressing a resource