The first scheme to exploit the tidal energy of the Severn Estuary was dreamt up more than a century ago. With the second highest tidal range in the world, the Severn could provide - according to estimates - around 5% of the UK's electricity needs. The government is currently holding a wide-ranging consultation into the feasibility of a tidal energy scheme, with expert opinion roughly divided between a estuary-spanning barrage fitted with turbines and a series of man-made lagoons.
This is an area in which technological innovation is now fast and furious. Marine Current Turbines of Bristol has been working for years on SeaGen, the world's first commercial scale tidal stream turbine, reaching an important milestone at the end of 2008, when the installation at Strangford Lough in Northern Ireland generated at its maximum capacity of 1.2MW.
Electricity generated by SeaGen is now being bought by a local energy company, ESB Independent, as MCT launches its next initiative - a joint project with nPower Renewables to install seven SeaGen turbines, with a 10.5MW total capacity, off Anglesey.
Also in Bristol, Tidal Generation Limited is working on a prototype for a fully submerged tidal turbine, which will be installed at the European Marine Energy Centre in Orkney. Having been assisted by the city council's BETS scheme, TGL aims to contribute to the UK's energy needs by 2010, offering low carbon, cost-effective technology.
The restoration of the 19th century Clifton Lido is good news not only for local swimmers but also for solar supporters. Installed by Bristol company Solarsense, the Lido's solar hot water system is one of the largest in the UK. Solarsense has already installed over a thousand solar heating systems since it was founded in 1994, with major installations at places as diverse as Sidcot Quaker School, Somerset, and the Iona Community in Scotland.