Archie the Screw has arrived, but we are almost screwed by the Georgians!!!
November has seen a major milestone with the delivery of the Archimedes Screw but also November produced some unforeseen ground conditions that have set us back by a few weeks.
After a long journey across the North Sea Archie landed at Killingholme Port on the South bank of the Humber and wound its way to Congleton via the M62.With a total vehicle length of 16.950M and a height of 3.85M, it was not judged to be an “abnormal load” and the journey was, according to the driver, uneventful. The trailer was equipped with a rear wheel steering system and the skilled driver only held up the Macclesfield Road traffic for about 1-minute as he reversed onto our access track.
A crane had been pre-ordered, and it took about two hours to separate the “Screw System” into its three core parts and lift off the transport (Top Cage, The Helix and The Trough). Separated to reduce the lifting weight and to ease its onward journey down the slippery slope onto its foundations.
The hydro’s ‘Beating Heart’ The Helix
The easiest way to install the Archimedes Screw into position on its foundations would be to use a crawler crane. However, the crane won’t be able to transport the screw to the hydro site itself, so the plan is to use a pair of diggers working in tandem—-watch out the JCB dancing diggers exhibition team, you have some emerging competition. We will do our best to capture some decent photographs of this daunting exercise.
That is the good news, now for information on a little bit of a setback that will give a programme delay of a few weeks.
Not only do we have obstacles like the unexpected rock levels to contend with on the site (as discussed in our previous newsletter), but we have also now uncovered some long forgotten Georgian masonry. While excavating the channel for the screw our contractors found a largely intact and fairly massive stone wall which “of course” runs diagonally across the screw channel outfall.
Now we know why those 2 piles in the photo below stick up like sore thumbs. The wall can be partially removed but a section supporting the riverbank will have to be left in place. This will inevitably mean that the alignment of the outfall from the base of the piles to the river will have to be re orientated at ~30degrees to the screw channel. With a profile like an Olympic Bob Sleigh Run the output flow will be undiminished.
When we overlaid the 1873 & 1899 OS maps over our site block plan it was clear that the masonry wall (black dashed line on sketch below) was actually the original bank of the river and in fact extends all of the way up to the ancient stone and brick archway. Furthermore, behind the wall we found hardcore cutting in from the bank about 2.5m. If you study the Estate Map from the early 1800s (below) it appears that this could be the remains of a road connecting Havannah Lane to the old archway
Finally, we’ve often speculated on the purpose of the archway and thought that, just perhaps, it was built as a means for diverting the river flow during the construction of Havannah weir in the late 1700’s. Lo and behold some support for this theory was discovered in the form of a stone spillway lurking beneath the silt extending out from the archway into the river.
Next month do not be surprised to read about Roman mosaics under the control shed…….
The Boardwalk gets under way!
Construction of the Boardwalk has now started. The work is being carried out by Redfox Countryside services. Approximately 80metres in length, it winds it way from Havannah Lane, through the woods and ends in a viewing platform overlooking the Archimedes Screw. There will be several Interpretation Boards located on the boardwalk to provide information on various aspects of the project and the habitats of the immediate environment and the River Dane itself. Sometimes it pays not to be “green”! The main posts that support the framework of the boardwalk are sunk about 1/2M into the very marshy, sodden ground. So, what a good idea to use 6” x 6” posts made from recycled composites—rot proof (sort of) and “green”. Unfortunately, we have quickly discovered that because of the nature of the manufacturing process internal blow holes are quite frequent. According to the supplier, these blow holes do not affect the structural strength, but sods law dictates that a blow hole will sometimes be present just where a fixing needs to go. We have a lot to learn from our Victorian forbears whose creosoted rail sleepers and telegraph poles have withstood the ravages of the last century or so!!
Recycled “Composites” post with Blow Hole.
Weather dependent of course but is hoped that the Boardwalk will be substantially complete by Christmas.
Also, by Christmas, Dutton Contractors will have installed the final 80 metres of cable from Havannah Lane to the Powerhouse itself. The final run of cable is slightly thinner (95mm) to enable some flexibility to get it more easily terminated into the Power Control Cubicle. The cable will run on hangers under the boardwalk.
The control system development and testing is progressing well. The system is based around a Programmable Logic Controller; devices of this type are widely used to control complex industrial processes. A sequencer function is needed to ensure that the system can start up and stop with the correct sequence of events. This involves controlling the compressor and associated valves which operate the sluice gate, the hydraulically operated disc brake on the generator / screw, and the setting of the speed control for the variable speed generator. The start-up sequence involves opening the sluice gate to allow the forebay tank to fill, then releasing the brake and simultaneously starting the variable speed control of the generator. The stopping sequence requires the running down of the generator to minimum speed then closing the sluice gate, stopping the generator, and applying the brake.
During normal operation, a speed control function ensures that the level of water at the weir head is constant by controlling the speed of the screw (and thereby the volume of water being diverted around the weir). If the water level at the weir head goes up, the screw can speed up (thus generating more power) and if it goes down the generator slows down so that the level can pick up again. If there is insufficient in-feed (during the increasingly rare “dry-spells”), the system stops, and the sluice gate closes, but automatically re-starts when the water level picks up again.
The system uses a range of measuring devices and sensors including water level detection, infra-red sluice gate position sensors, rotation speed sensors, generator and gearbox temperature sensors, vibration sensors, etc. A comprehensive range of conditions are checked to ensure that everything is operating correctly, and warnings / alarms are raised should something malfunction. One critical function is the measurement of the electrical energy generated, to allow billing to OFGEM (for FIT payments) and to the factory using the electricity. The vibration sensors are used to give early warning of potential bearing failures in the drive train. One little niggle during configuration has been some difficulty to interface with the Modbus meter reading system. This has now been sorted and the plc can now read volts, amps, power, frequency, and kWh from the electricity meter.
In principle the range of monitoring and control functions are similar to those required in a modern car’s engine management system.
Finally, the operating status of the system is continuously monitored by a wireless link to a “cloud based” data logging and control system (a system called Mindsphere provided by Siemens). This allows the operational staff to keep an eye on the condition of the system from their home computer or mobile phone and to take corrective action if required. Text messages are automatically generated in the event of a malfunction to alert them to the problem.
This wireless link will be via 3/4G. We have yet to do a survey to decide the best place to put the antenna but in general there is good 3/4G coverage on this part of the site.
All of this work will hopefully pay dividends by minimising the actual on-site commissioning that will need to be done during the forthcoming wintery months.
A major associated piece of work also comes to fruition this month and this is our new website. The link is still the same, but the site has been completely refreshed
The interest in the project from the community has been fantastic and we wanted an easy to use website that will share as much information about Congleton Hydro as we can with a clean, modern look. We have used the WordPress platform, which is a popular open source blogging software, it’s mobile responsive and in the future, we will look to add a members area.
The site details the build of the project organised into the following sections: Technology, Education, Share Raise, Site History and Gallery. We will be adding more information over the following months as the project progresses. Once the build of the project is completed the website will be featuring our education events, green champions and the grants awarded to the community groups who we hope to help.
Please look, we would love to get your feedback!
So, progress continues albeit with some annoying and unwanted interference from our Georgian forebears! During the next weeks, work will continue to finish the “screw channel” complete with its “bob run” curved and banked outlet run into the river. The construction of the top and bottom foundation blocks will also take place with the screw securing “bolts” cast precisely into the concrete foundations. The forebay tank- which connects the inlet pipe system to the Archimedes Screw inlet has yet to be started. Once this is complete the final bends of the Weholite inlet pipework can be inserted and the whole Weholite pipe run “welded” to produce a secure leak free feed (this should provide some interesting photographs, as the welding is done from inside the pipe -even though it is 1.5M diameter, still not easy!)
The Power House can then be constructed and the Control System cubicle installed.
Finally, we will have the “dancing diggers” install the Screw on hopefully their perfectly aligned securing bolts! Once the screw is in position the gearbox and generator can be delivered to site (currently in store) and coupled to the screw shaft.
Obviously still a lot to do and with the Georgians having “screwed” us up a bit, our programme has now slipped a few weeks and it will be February before we have a trial start. Still not bad for a bunch of first time Hydro Volunteers!!!
Our “technical feature” this month is non-technical but its contents underpin the whole viability of the Project, from its inception, design, planning approvals, construction, ongoing operation and maintenance, repayment of monies to The Investors (capital and interest) and of course our whole project rationale — To raise substantial funds for worthy Community projects.
It’s titled The Balance Sheet – Flow v £’s, download below:
It really does illustrate that it does not matter how good your product/ idea etc is, unless it is based on sound financials, doom and gloom will be just around the corner.
It also perhaps illustrates how well rounded Engineers need to be—it is a great profession even though our Georgian Engineer forebears almost screwed us up, but then that is probably our own fault for not checking their drawings, that like all good Engineers, they had carefully prepared!!
We do hope you find the contents of this newsletter to be of interest, as always, we welcome your feedback on errors, omissions, suggestions for improvement and future features and articles. Please contact us via info@congletonhydro.co.uk
Finally, thank you all for supporting Congleton Hydro using this unprecedented year of doom, gloom and outright fear. Just like the Hydro Project the prognosis for 2021 is somewhat brighter with hopefully this bloody virus transmission rate reducing and the prospect of a vaccine in the near future.
From all of us in the Congleton Hydro Team, we wish you…
Dane Valley Community Energy Ltd (FCA Registration 7142)
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