When it comes to hydropower in Britain, what's good enough for Her Majesty looks good enough for the city of Bristol.
As we reported here last September, the Queen was tapping an ancient piece of technology called the Archimedes' screw to power Windsor Castle, on the outskirts of London.
Greek philosopher and mathematician Archimedes of Syracuse invented the contraption over 2,000 years ago to haul water up from rivers to fields. Water would rise in spinning threads as someone turned a handle.
The idea also works as an eco-friendly form of hydropower. Rushing water spins the screw which in turn drives a turbine. Fish purportedly find their way safely into tubes that run alongside.
The Queen completed installation of two 40-ton screws in a weir along the River Thames near Windsor Castle in December, according to the Daily Mail. Once connected to Windsor, they'll provide 1.7 million kilowatt hours per year. That's enough to power the entire royal domicile (the equivalent of about 400 homes) for about 90 percent of the time, costing £700,000 ($1.1 million) for each 12-meter by 4-meter (39-foot by 13-foot) screw and about £1 million ($1.55 million) to install, the Mail says.
A £100,000 ($155,000) fish tube in theory permits mangle-free migration for salmon, trout, perch and eels. The fossil-fuel free generation is expected to cut 790,000 kilograms of CO2 per year.
Enough history and royalty. The common folk of Bristol, a city roughly a hundred miles west of Windsor, think the idea makes sense. Or at least Bristol City Council does. It's proposing to install "relatively small" screws in the River Avon, enough to power dozens of homes, according to the BBC.
"There'll be no changes to the river at all - it's simply using the flow of water that's already there," says councillor Neil Harrison. The Council aims to finalize its proposal this spring, and to install the screws by next year.
These things are popping up around the UK. Cardiff is building an Archimedes' project on the River Taff. I've seen one in action on several trips to Devon in southwest England, at a place called River Dart Country Park, where a neat bit of quiet engineering helps generate electricity along the serene river.
A turn of the screw in the fossil fuel coffin, or just a sweet shade of green that won't in the end make much difference? What do you think?