Scotland's Orbital Marine Power (formerly Scotrenewables) has completed the build on what it claims will be the world's most powerful operational tidal turbine. It's now on its way to the Orkney Islands, where it'll have a chance to prove its worth connected to the grid.

Solar energy is a key part of the energy mix that'll push us towards zero carbon emissions – but lunar energy might have a role to play too. As the moon's gravity pulls at the Earth's surface, it heaves vast quantities of ocean water around the globe in predictable patterns. Where this water is forced through narrow gaps or around headlands, it speeds up, and it's possible to harvest the kinetic energy of that mass of water using turbines under the ocean's surface. This is called tidal power.

It's not new; people across Europe and the Middle East were sticking water wheels on the outflow of pools that fill up with the tides to grind corn as far back as the middle ages.

Today's biggest tidal energy projects, Korea's Sihwa Lake Tidal Power Plant and the Rance Tidal Power Station in France, have both been built using enormous and extremely expensive undersea walls, or barrages. These barrage systems close sluice gates at low tide, then open them up at high tide to take advantage of the height differential to run turbines. They work well, but the installation cost is stratospheric and the stifling of natural water flow has had some negative environmental consequences.

Orbital's approach is targeted to keeping costs as low as possible. It uses floating turbines, installed in channels that accelerate tidal flows. These turbine platforms are moored to the ocean floor at four points using extremely strong chains, meaning the undersea work to install them is quick, cheap and minimal.

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