First the Queen did it, on the River Thames near Windsor Castle. Now the operators of a public stately home and park in London are doing it and, like Her Majesty, have headed to a river bank to pull off the deed.
The owners of Morden Hall Park have installed an ancient piece of machinery, called an Archimedes screw, to power their visitor center. Following the Queen's example, they've essentially turned the idea of the screw upside down. Greek philosopher and mathematician Archimedes of Syracuse invented the contraption over 2,000 years ago as a way to lift water from a river to irrigate crops. In his application, turn a hand crank and water rises up the threads (see videos below).
But as "green" engineers have discovered, if you let water run over one in a tumbling river weir, the screw spins enough to drive an electricity generator. As an environmental bonus, proponents say the screw is gentle on wildlife - ie, it does not mangle fish the way larger hydro machines can.
Morden Hall's website estimates that the screw will generate "59,000 kWh a year - about 12 times as much electricity as an average household uses." The Guardian newspaper, which observed engineers maneuver the screw into place this week, reports its capacity at a modest 8.5 kilowatts, "enough power for 18 average-sized houses in the UK."
Either way, the screw is part of a movement toward local electricity generation through small scale, renewable energy projects.
The two Archimedes screws that the Queen installed on the Thames are to power Windsor Castle, her little suburban retreat outside of London.
Both Morden Hall Park and the Queen bought their screws from Holland.
Morden Hall is a former snuff mill where water wheels once turned millstones that crushed tobacco into powder, so when the screws start operating in September, they'll mark a full circle back to river power. It's owned by The National Trust, a non-profit conservation group that buys and protects heritage and beauty sites.
Here's Flickr video of an Archimedes screw in action at River Dart Country Park in Devon, Southwest England:
Here's a commercial YouTube video from Dutch company Spaans Babcock advertising its Archimedes screw and explaining how it works:
I couldn't find any 2,000-year-old footage of an original Archimedes screw irrigating ancient Greek fields. But here are a couple of YouTube videos that give you a flavor. Disclaimer: the first involves children that some readers might consider annoying ("after we made our hovercraft, we decided to make an Archimedes screw," screeches one); the second is in a language you might not understand. Nevertheless, they are visual and informative:
Shouldn't they be playing baseball? -
You'll at least make out the phrase "Archimedes screw" -
Photos and Videos: River Dart from Adrian Midgley via Flickr. Spaan Babcock screw from Vivid Photo Visual via YouTube. Kids from Meemer115 via YouTube. Second demo from Pratham Science Group via YouTube.
Note: Story updated July 21, 3:25 a.m. Pacific to elevate Queen to loftier "Majesty", above original, lowlier, "Highness." Thanks to the reader who wrote in pointing out the unwitting egregious error. Apologies - no snub intended.
Mores screws and hydropower on SmartPlanet: