Hydro Power: Large Scale
Although many people don't realise it a significant portion of the world's electricity comes from hydro-power technology. Several countries including China, Canada, the United States and Brazil utilize stores of water (held in reservoirs or flowing in large rivers) to generate green renewable energy. Industry too has realized the potential of hydroelectricity. Mining companies and smelts, for instance, often use hydro power as a way of balancing the negative and positive environmental impacts of their practices as well as providing a reliable source of electricity in what are often quite remote regions.
It is the ocean-based hydro technologies which are most exciting, however, as the potential for these techniques is endless: companies are now investigating the financial and technological practicalities of large wave and tidal farms and have begun to install prototypes in locations all over the world.
Dams and Reservoirs
Large-scale hydroelectricity schemes of the traditional variety are present in many nations internationally, including the United Kingdom. Reservoir and pumped-storage plants are popular particularly because they are easy to control - all that is needed initially is a large body or supply of water. Regions of Scotland and Wales are particularly suited for large-scale hydroelectric schemes: the Affric-Beauly, Breadalbane, Galloway, Ben Cruachan and Tummel hydroelectric plants in Scotland and the Llyn Celyn, Cwm Dyli, Rheidol, Dinorwig and Ffestiniog schemes in Wales already produce significant amounts of electricity. The majority of these plants have been around since the 1960s when the technology was first introduced on a wide scale.
Some commercial enterprises have made use of abandoned or decommissioned water mills, converting them into hydroelectricity plants and then selling the generated electricity back into the grid or to a utility company. Because the British Government has made it necessary for electricity utilities to obtain a portion of their supply from renewable sources the purchase of hydroelectricity from companies and private suppliers is becoming more common.
Tidal Stream Systems
The future, however, is not in reservoir-based hydroelectric schemes but in ocean-based hydro power. Tidal power in either of its incarnations (tidal-stream or tidal barrage) is ideal for nations with large swathes of coastline such as the United Kingdom. As the height and timing of tides is easily predictable tidal hydro-power is efficient and reliable; because it does not require the storage of fresh water there is no problem with decaying plant matter letting of methane gas (a harmful ozone-depleting gas).
At present the tidal stream system, which uses fast natural currents to power turbines, is being trialled in Devon and Scotland and a prototype system in Strangford Lough (Northern Ireland) has been particularly successful. The invention of the shrouded tidal stream turbine has furthered this experimentation as it reduces drag and pressure on the turbine, increasing its productivity.
Tidal Barrage Systems
The other tidal-reliant generation system, the tidal barrage, has been successfully implemented in a number of global locations including Swansea Bay (across the River Tawe). The barrage system involves forming a marina or lagoon with a series of sluice gates and then allowing the changing height of the tides on the outside of the gate to generate energy as it pushes in and out of the turbines. There are plans for further barrage systems on the Severn, the Mersey, and at Conwy.
The final ocean-based hydroelectric technology, wave power, is still largely experimental. There are several techniques for harnessing the power of the waves, usually involving a string of buoys attached to a turbine that can convert the mechanical power generated by their movement into electricity. A wave farm is planned for the Orkneys as well as off the coast of Hayle in north Cornwall.