by John Greeves
Guest Contributor
Past generations may not have coined the term “sustainable energy,” but the idea that it is a modern phenomenon can be misleading. Human societies have long relied on water, wind, and tidal energy to service their needs. The history of sustainable energy is a surprisingly long one. In Roman times, the River Fleet was a major river flowing into present-day London, and its estuary is said to have contained the oldest known tidal mill in Britain. The Domesday book (a survey of English land and property values compiled in 1086) lists 5,624 watermills in England, one for every 350 or 400 people. By the end of the 11th century water and wind power had become essential for many industrial processes including milling grain, processing cloth, tanning leather, sawing wood, and crushing ore. In many ways this period can be viewed as a pre-industrial revolution powered largely by sustainable energy.
One form of watermill was the tidal mill. Tide mills were usually situated along shallow creeks a few miles from the coast. An adjacent large pond was constructed to hold the water of the incoming tide. Tide mills were once a familiar sight around Britain, but now only two working mills remain: the Woodbridge Tide Mill and the Eling Tide Mill in Southampton.
I first became interested in Woodbridge Tide Mill when I came across it after visiting Suffolk on a family holiday with my wife and son. I believe the mill is not only historically important, but it provides a working example of how sustainable energy can be produced with minimal impact to the environment. In a hundred years the Woodbridge Tide Mill may not exist due to rising sea levels. Nevertheless, the mill offers an insight for the future. There’s no reason why small communities shouldn’t take charge and produce their own electricity from tidal energy in the same way many mills harnessed it in the past. Considering the extensive coastline of Great Britain and its many surrounding smaller islands, as well as the many coastal communities around the world, this line of reasoning would make complete sense in a period where global warming continues to threaten.My account will tell the story of this surviving tidal mill in Suffolk. I will explain how tidal mills work and how this particular mill, ironically, is likely to be threatened as climate change continues.
History of Woodbridge Mill
The first recorded reference to a tide mill at Woodbridge occurs in 1170. It’s believed three mills had been standing on the Deben estuary at Woodbridge for nearly 850 years when the medieval mill was first recorded.
The recorded history of mills at Woodbridge begins with a mill first owned by a local Augustinian priory for about 350 years, then acquired by Henry VIII during the Dissolution of the Monasteries. The mill remained under royal ownership until Elizabeth I sold it to Thomas Seckford, whose family owned it for over 100 years. A series of private owners came and went. In 1793, the present mill was built on the site of earlier ones. By the 1950s it had become the last working mill in the country. A hammer mill was introduced in around 1953, run by a diesel engine from a tractor. The old millstones were seldom used. Milling was mainly for animal feed then, but the place was set up so millers could turn their hand to anything. In 1957 the shaft broke but the mill continued until 1968 when Mrs. R. T. Gardiner, a local woman, purchased the mill and launched a restoration programme to save this Grade I listed property (indicating its historical interest).
Restoration was a major undertaking. To give just a few examples, rats had gnawed a pattern of runs in (formerly solid) 9 by 9 inch posts. The foundation brickwork was cracked and unsound. Many timbers were rotten, with the timber frame in a state of poor decay. The mill opened to the public in 1973 but it wasn’t until 1983 that a new mill pond was constructed on half an acre of nearby ground so flour could once more be milled on location.
Today, the mill stands proud, clad in glistening white Suffolk boarding. The majestic three storey wooden building has a Gambrei roof with an eye-catching lucam overhang. It belies the less illustrious days when rotten timbers were clad entirely in rusting corrugated iron for over sixty years. Ironically, it was this sheeting that saved the mill, binding together the decaying timbers within the metal skin.
Dan Tarrant-Willis (mill manager and tidal miller) tells me, “Woodbridge Tide Mill is not a government project, but rather a very good example how renewable energy can be controlled by the community.” He’s one of 40 volunteers at the mill, and he believes in thinking beyond the remit of government to encouraging community cooperation as an important way to address local energy needs. “In terms of the future, people are born into the idea, almost religiously, of having a government that provides for us and tells us what to do,” he says. Dan thinks the Woodbridge Tide Mill is a model that can be copied in order to produce tidal energy in other communities. He sees this as a real possibility, rather than science fiction.
The present tidal mill runs without national government financial support. 30% of its revenue comes from the sale of Wholemeal stoneground flour (with no additives), which is sold to numerous local and county outlets. Revenue is supplemented with visitors who view this working mill, including many educational groups. Merchandising items such as bags and aprons are sold in the small shop. A small contribution comes from the local city council.
How it works
The only difference between this and an ordinary watermill is the mill pond. Modern tidal lagoon energy works on the same principle. When the tide comes in the mill pond fills with the tide water. The pressure of the incoming tide opens the sluice gates in the bank and fills the pond. As the tide falls, the out flowing water closes the gates, which are held in position by the trapped water. When the tide has fallen sufficiently, the miller opens the sluice gate and the released water turns the undershot wheel.
The mechanism is a triumph of technological simplicity and was developed over hundreds of years. Those who built the mill took full account of environmental constraints. “You have to be completely sympathetic to the environment that the machinery is going to be placed in,” Dan insists, if you are going to succeed. A tidal mill is not a “one fit for all” situation, but needs to take into account the specific site, the resources available locally to construct it, the contour of the land and waterway, and the tidal extremes.
Dan admits, “The Woodbridge Tide Mill may not be very efficient in terms of energy output, but it works every day. When it doesn’t work we can fix it with locally made parts without involvement from the outside.” He also factors in the notion of “sacrificial parts,” parts such as the wooden teeth of the pit wheel (see below) that can be replaced easily to ensure the continuation of the milling process with sustainable energy.
The machinery
The Waterwheel has a 16-foot, 4-inch diameter, weighs 4 tons, and has 56 floats, each one an inch thick and fifteen inches wide. It’s connected to a solid 22-inch thick oak shaft that runs into the mill building. On the end of the shaft there’s a vertical wheel in the same configuration as the waterwheel called the Pit Wheel. This turns at the same speed as the waterwheel. The pit wheel is metal but has wooden teeth. The opposition of iron to iron is always avoided. Moulded to the iron teeth, wooden cogs reduce noise and produce smoother motion. They can be easily replaced by an experienced miller. The teeth of the pit wheel engage with a cast iron wheel called a Wallower Gear, which is fixed solidily to a vertical shaft that runs to the top of the building. Above the wallower gear on the same shaft is the Spur Wheel (about 20 feet across) which engages with some small cogs called Stone Nuts. These are fixed to the upper millstones in the Tuns (wooden casing around the millstones), which grind the grain. The overall gearing system ensures the millstones are driven at 50 rpm. Originally, the four stone nuts were mounted on wrought iron axles. These could be disengaged if the miller did not want four pairs of stones working at the same time. Today, only two of the four pairs of stones are operational.
At the top of the vertical shaft, on the third floor (crown floor), is the Crown Wheel, where the final demands on energy are made. This originally drove two dressing machines (a mechanical device used in mills for “bolting,” separating finished flour from other grain components following milling), but today operates the sack hoist, where bags of grain are hoisted from the ground to the third floor. The grain is fed into one of the hoppers and dribbles its way down to the second floor (stone floor), where it enters another hopper. The grain is induced to flow into the centre (eye) of the running stone by a vibrating, sloping trough called a slipper or shoe. The process is aided by a rotating spindle called a damsel. Here the grain is crushed into flour by the mill stones and flows down a chute, where it is bagged on the ground floor.
Climate change: its impact on the mill
In a recent document commissioned by the UK government entitled Current and Future Impacts of Sea Level Rise on the UK (2017), attention is drawn to impending sea level rise. The report states:
Sea level rise projections for the 21st century are very uncertain, generally ranging from 25 cm to around 1 m (depending on greenhouse gas emissions and ranges of modelling uncertainties), with a few estimates consistent with 1.5–2.5 m.
By its very nature a tide mill exists in a precarious environment and is very susceptible to tidal forces. Many tidal mills in the past were built on marshy ground where foundation timbers rotted rapidly. Flooding was a constant hazard and the structure eventually fell into the sea. In recent years at the Woodbridge Mill, “We have a situation at very high tides when the water comes up within a few inches of soaking the floor,” Dan explains. So far, the mill has managed to still be there when the water recedes, but a damp mill is incompatible with making flour.
Dan has also observed a dramatic increase in the silting up of the river year by year, which also affects the flow of the tide up the river. A heavy spring tide or surge with the wind in the wrong direction could lead to a devastating outcome for the mill. “Woodbridge could be in a very precarious situation, like other mills in the past.”
Dan has a pragmatic view of the future: “If flour production ceases at Woodbridge, I would like to see a mill in a hundred years here producing electricity. This would be in keeping with the ethos of what came before.”
To the young children who visit the mill he says, “This is your future and your past.” He’s quick to describe the mill as a gravity machine and to broadcast the message to all generations concerning the application of gravity to produce sustainable power. “It’s an area that’s largely neglected in terms of supplying energy needs. It’s involved in everything. If we could harness the gravitational pull, which we do in the tide mill, the possibilities are mind blowing.” As to the volunteers who keep the mill going, Dan describes them—along with himself—as just ordinary people who put on their “gumboots” to do whatever the task requires, and to ensure the smooth running of the mill from day to day.
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Bio: John Greeves originally hails from Lincolnshire, UK. He gained a master’s degree at Cardiff University and a fellowship in 2010. Greeves taught for Continuing & Professional Education at Cardiff University part-time for twelve years. He believes in the power of poetry and writing to change people’s lives and the need for language to move and connect people to the modern world.
Since retiring from Cardiff University, Greeves works as a freelance journalist who is interested in an eclectic range of topics. He is also a published poet and runs a creative writing workshop in his local community.
