FREE* wheel an environmentally benign energy source

FREE* wheel an environmentally benign energy source
© FREE* wheel an environmentally benign energy source * Flow reversal energy extraction

Extraction of horizontal flow energy
from rivers and tidal flow channels

Present proposals for tidal flow generation
the presently proposed tidal flow generators have their working parts installed entirely underwater their rotor blades are very vulnerable they harness a very small cross-section of the current they extract energy from only one direction of current flow maintenance will be difficult © Marine Current Turbines Ltd.

which can also be used in large rivers
Flow Reversal Energy Extraction Wheel an alternative method of extracting significant energy from two-way tidal flow which can also be used in large rivers

Proposed tidal flow generating scheme
these alternative tidal flow generators have all of their working parts installed above the water level they harness all of the cross-section of the current they extract energy from both directions of current flow maintenance can easily be carried out

each of these six-rotor barrier sections will generate 150 Megawatts
Plan view of a practical and effective alternative tidal flow energy extraction system 230 metres each single rotor unit will generate 25 Megawatts for around 23 hours per day each of these six-rotor barrier sections will generate 150 Megawatts this group of four sections will provide 600 Megawatts Scotland’s total electricity demand is around 6,000 Megawatts ten of these four-unit barrier groups installed in tidal channels around the country will provide all of this demand with no adverse impact on the environment overlapping generating periods will provide continuous power excess “off-peak” and spring tide capacity can be used to produce hydrogen gas apart from capital and maintenance costs, the electricity is free © clf anderson diagram only not to scale

this group of barrier sections will produce 900 Megawatts
Island of Stroma Skerry Duncansby Head St Johns Point Gills Bay Ness of Hunna Caithness Pentland Firth Inner Sound of Stroma Swilkie Point Scarton Langaton Red Head the island forms part of the barrier 900 mw capacity barrier 1 kilometre the Inner Sound of Stroma with six tidal barrier sections in 30 metres depth of water this group of barrier sections will produce 900 Megawatts shipping can pass freely around or between the barrier sections

Proposed tidal flow generating scheme
Following presentation of the paper which described these proposed tidal flow turbines to the Institute of Mechanical Engineers in April 1990, the President of the Institute, Mr. M J Neale, wrote on the 20th. of December, 1990: “This is certainly a very interesting idea and a novel method of extracting tidal energy, with what appears to be a lower level of capital expenditure per kW compared with more conventional proposed barrage schemes”.

each unit consists of two main parts:
a vertical axis multi-mode rotor and a guide chamber plan view the guide chamber is symmetrical to allow energy to be extracted from both directions of tidal current Note: large river installations use a similar guide chamber which is designed for one way flow only © clf anderson diagram only not to scale

Each individual rotor blade operates in three distinct modes:
reaction mode, hydrodynamic mode and displacement mode water flow reaction mode (also called “Pelton wheel” mode) entry flow exit flow energy is extracted from the water flow as it is forced to change direction this applies torque to the rotor exit flow entry flow the vanes in the guide chamber are shaped so as to give optimum flow direction against the rotor blades © clf anderson diagram only not to scale

each rotor blade operates in three distinct modes
reaction mode, hydrodynamic mode and displacement mode this distance hydrodynamic mode is greater than this distance higher flow velocity causes lower pressure linear thrust is applied to each blade by the difference in pressure between its two sides which causes torque to be applied to the rotor thicker blades provide more torque slow water speeds allow very thick blades without any cavitation problems © clf anderson diagram only not to scale

each rotor blade operates in three distinct modes
reaction mode, hydrodynamic mode and displacement mode guide chamber wall displacement mode each pocket in between the blades of a typical rotor contains 200 tonnes of water travelling at around 8 miles per hour this rotor contains 3,600 tonnes of water within the ring of blades deep water shallow water each blade acts as a piston within the tunnel sections of each guide chamber unit the rotor extracts energy from 2,000 tonnes of water per second a wind generator processes around 4 tonnes of air per second © clf anderson diagram only not to scale

plan view of the tidal flow reversal energy extraction unit
long cut waters are not shown up stream part of the prefabricated guide chamber notional “north” notional “north” part of the next unit negative torque is applied to one blade only reactive and hydrodynamic modes in this quadrant additional flow from upstream bypass channel vent flow to downstream level in each tunnel part of the next unit this rotor runs clockwise internal guide vanes positive displacement mode reactive and hydrodynamic modes in this quadrant a gate may be used to close this bypass channel to improve the displacement flow in the “south east” tunnel down stream plan view of the tidal flow reversal energy extraction unit © clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale

plan view of the flow at the “north-west” corner of the rotor
© clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale the rotor runs clockwise downstream pressure negative torque on this blade only upstream pressure positive displacement flow in this tunnel section notional “north” no torque is applied to this rotor blade the rotor is inherently self regulating - it cannot seriously overspeed even if there is complete loss of electrical load plan view of the flow at the “north-west” corner of the rotor

plan view of the flow at the “north-west” corner of the rotor
© clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale upstream pressure negative torque on this blade only downstream pressure notional “north” each blade leaves the exit tunnel immediately after the following blade has entered it negative torque is applied only to the one blade which is within the exit tunnel

diagram only not to scale
Tidal flow generator unit notional “north” tidal flow each unit is used to form part of a free standing tidal channel barrier an “end unit” may be fitted with a closing wall to form a vent channel this lowers the water level at the “north west” corner of the rotor below the level of the water at the entrance to the “north west” tunnel this ensures effective positive displacement flow in the tunnel downstream water level vent channel flow improves the flow in the “south west” quadrant a single “free-standing” unit would have two closing walls plan view © clf anderson diagram only not to scale

venturi gaps between units may be used to improve the rotor
closing wall plan view closing wall venturi gaps between units may be used to improve the rotor performance in displacement mode © clf anderson diagram only not to scale

Tidal flow generator unit each unit is floated to its final position using buoyancy chambers and airbags seabed preparation might involve rubble deposition or dredging to give a level base buoyancy chambers are filled with sand ballast when each unit is finally installed on site “offshore platform” type equipment may be used to secure the unit to the seabed rotor bearing levelling adjustment can be carried out during final commissioning “end of life” decommissioning involves suction dredging sand and water from the buoyancy chambers, closing and sealing the isolation gates, installing airbags, removal of any seabed fixings and towing each unit to its final disposal site plan view © clf anderson diagram only not to scale

the wide bearing surface gives very rigid rotor support
support bogies blades FREE wheel rotor these support bogies mimic a conventional taper roller bearing superelevated concentric rail tracks the wide bearing surface gives very rigid rotor support cutwater prefabricated rotor guide chamber the angled support bogies accommodate side thrust on the rotor sea bed level side elevation © clf anderson diagrammatic only not to scale

Note: power take off can be by gears or hydraulic or
bogies may be overlapped to provide more support blades FREE wheel rotor the sea level piles up on the upstream side sea level falls down stream Note: power take off can be by gears or hydraulic or the generators may be mounted directly on each bogie all engineering and electricals are above the water surface conventional low speed rail technology is simple, economic and very reliable © clf anderson diagrammatic only not to scale

diagrammatic only not to scale
Tidal flow pattern sea levels at the end of a tidal flow period sea levels at the start of a tidal flow period FREE wheel rotor each unit extracts energy from the difference in levels between upstream and downstream of the barrier, caused by the presence of the barrier in the current, rather than from the absolute difference in sea levels at high and low tide sea levels may actually continue to rise (or to fall) despite reversal of the current flow © clf anderson diagrammatic only not to scale

Rotor bearing adjustment
FREE wheel rotor rotor bedplate top deck the top deck of the guide chamber is built with a segmented circular recess the rotor bearing bedplate is cast in situ with a separating membrane and seals if the rotor needs to be adjusted when the unit is landed into its final position high pressure liquid (cement) can be pumped into the interface to float the bedplate the bedplate can be raised at whichever side is required so as to level it the bedplate would then be fixed in place using cement grout or adhesives minor adjustments can be made by packing up the rail track supports © clf anderson diagram only not to scale the rotor will, however, run successfully even if it is out of plumb

Generator installation
weather shield rotating power house generators FREE wheel rotor the power house rotates at half rotor speed typically around 1 ¼ revs per minute slip rings take power from the rotating power house to the fixed structure power may be exported below sea bed level, overhead or as hydrogen the power house may instead be installed on top of the rotor disk to increase the weight, and hence the driving friction, on the support bogie wheels reducing the width of each unit would increase its power extraction potential the bogie wheels use conventional railway practice and may be metal on metal, rubber on metal or rubber on concrete as appropriate © clf anderson diagrammatic only not to scale

Generator installation
generators FREE wheel rotor wheel spindle bearing loading is greatly increased if conventional bogies are used bogie spindle speed is increased but the power house must rotate at rotor speed the power house may be made separate and held stationary if a hydrostatic transmission system is used with the displaced hydraulic fluid being taken to the centre of the rotor and transferred using a rotating sleeve pressure tight coupling hydrostatic generator drives are presently used to convert reciprocating hydraulic flow into rotational generation in experimental wave energy extraction devices pressurised hydraulic oil can, if preferred, be piped to an onshore power station vegetable based hydraulic oil is biodegradable if spilt into the sea © clf anderson diagrammatic only not to scale

rotor units are built onshore and are towed to site
plan view tidal flow shipping is able to pass on either side of the barrier(s) rotor units are built onshore and are towed to site they are stacked together across part of the tidal channel each unit can start generating revenue as soon as it has been installed © clf anderson diagram only not to scale energy is extracted from both directions of tidal current

greater energy extraction potential
tidal flow plan view greater energy extraction potential can be obtained by packing the units closer together narrower guide chambers allow more rotors to be installed in the same width of channel diagram only not to scale © clf anderson

tidal flow on the ebb plan view closing walls may be installed on each unit in this configuration tidal flow on the flood when packed this way the rotors can overlap one another so as to fill the whole width and depth of the constructed barrier © clf anderson diagrammatic only not to scale

Tidal flow power extraction potential
tidal current flows for around six hours in each direction tidal flow reverses direction in less than half an hour this means that power can be generated for around 11½ hours out of each 12 hour, 25 minute tidal cycle different parts of the country have different flow reversal times true base load power generation is possible if units are installed at two or more complementary sites whenever one barrier is either idling or stopped, the complementary one is generating at full capacity electricity from these units is entirely predictable and thus will be much more acceptable to the national supply grid than the electricity produced by wind or wave generators diagram only not to scale © clf anderson plan view

standard “squirrel cage” electric motors can be used as
the geometry of the guide chamber ensures that the rotors always start and rotate in the same direction regardless of the direction of tidal flow standard “squirrel cage” electric motors can be used as induction generators when directly connected to the grid the generators will run ahead as motors (consuming only 2% of installed power) when the rotor stops this avoids the need for synchronisation of national grid phase and alternating current frequency because there is no switching, no mechanical, thermal or magnetic shock is applied to the motors because of this they can be rated considerably higher as generators than their nominal rating as motors if their generator rating is doubled, their power consumption when motoring will be halved to 1% roller clutches (ratchets) will pick up the drive to restart generation when the rotor restarts diagram only not to scale © clf anderson plan view

* as used on typical wind turbine generator drives
plan view Typical tidal flow extraction installation this guide chamber is 45 metres wide x 110 metres long the rotor is 34 metres diameter x 34 metres depth it rotates at around 2½ revolutions per minute it is supported on 100 bogies which rotate at 55 r/min, each bogie drives a standard squirrel cage motor (or motors) which operate as induction generators multi-pole winding could accommodate speed changes each generator is driven by a step-up ratio * gearbox or a hydrostatic positive displacement hydraulic drive each generator provides 250 kilowatts (330 bhp) † when running on a 2 metres head difference between the water levels upstream and downstream the rotor will provide 25 megawatts to the national grid for approximately 23 hours per day every day of the year * as used on typical wind turbine generator drives diagram only not to scale © clf anderson † helicopter roller clutches can handle 3,000 bhp

Calculations Performance of a typical single rotor tidal flow extraction installation Assuming a two metre difference in water level across the diameter of the rotor: Two metres head (2gH) equals 6.26 metres per second flow through the rotor 34 metre diameter wheel, 10.6 m chamber entrance throat width, 34 m deep Flow equals 10.6 x 34 x 6.2 equals 2,256 cubic metres (tonnes) of water per second 2,256 m3 x 0.02 MPa equals 45.1 liquid megawatts (59,300 liquid horsepower) x 70% rotor blade efficiency equals 31.5 megawatts shaft power (41,000 bhp) x 80% transmission/generator efficiency equals 25.2 megawatts to the national grid Wheel peripheral velocity equals 6.26 x 0.7 equals 4.38 m/sec (8 mph) 34 metres diameter wheel is metres circumference divided by 4.38 m/s equals 24.3 sec, ie 2.47 revolutions per minute of waterwheel.

Calculations Horizontal force applied to the tidal barrier generator unit: Assuming a two metre difference in water level across the width of the unit 45 metres width x 35 metres deep equals 1,575 square metres: 1,575 square metres x 2 metres head difference in water level across the barrier equals 3,150 tonnes horizontal force against the barrier unit

Calculations Mass of each barrier unit base plate is 45 x 110 x 3 x 1.6 equals 23,760 tonnes Mass of the barrier unit side walls is 110 x 40 x 10 x 1.6 equals 70,400 tonnes Mass of the generator machinery, equipment and housing at say 5,000 tonnes Mass of the deck and the rotor is 15,000 tonnes Total mass of each barrier unit is 114,000 tonnes Buoyancy force applied to the underwater concrete parts equals 1 tonne/M3 Subtract 52,250 tonnes buoyancy for the base plate and the submerged walls 114,000 minus 52,250 tonnes equals 61,750 tonnes weight on the seabed 3,150 tonnes side force divided by 61,750 tonnes weight of the unit on the seabed equals 0.05 co-efficient of friction required between the base plate and the seabed filling the buoyancy chambers with sand will significantly increase the weight ridges cast onto the base plate will help to grip the seabed venturi passages may be installed which apply a vacuum to the base plate bottom if necessary, each unit may be fixed in place using drilled or driven piles

plan view of a typical 150 megawatt partial barrier in a sea passage
there are six rotor units in this 150 MW barrier section rotors would be built in a range of standard diameters and the rotor blade length and the height of the guide chamber would be varied to suit the depth of water at the installation site 320 metres 230 metres © clf anderson diagram only not to scale plan view of a typical 150 megawatt partial barrier in a sea passage

plan view of a typical partial barrier in a tidal passage
clockwise rotors on this section anticlockwise rotors on this section shipping and escape passage between barrier sections flow guides may be added at each leading corner to suit the local geography Note: Coriolis forces may influence the performance of such large rotors © clf anderson diagram only not to scale

Plan view of a practical and effective alternative tidal flow energy extraction system 230 metres each single rotor unit will generate 25 Megawatts for around 23 hours per day each of these six-rotor barrier sections will generate 150 Megawatts this group of four sections will provide 600 Megawatts Scotland’s total electricity demand is around 6,000 Megawatts ten of these four-unit barrier groups installed in tidal channels around the country will provide all of this demand with no adverse impact on the environment overlapping generating periods will provide continuous power excess “off-peak” and spring tide capacity can be used to produce hydrogen apart from capital and maintenance costs, the electricity is free © clf anderson diagram only not to scale

each single rotor unit will generate 25 Megawatts for around 23 hours per day each of these six-rotor barrier sections will generate 150 Megawatts this group of four sections will provide 600 Megawatts Scotland’s total electricity demand is around 6,000 Megawatts ten of these four-unit barrier groups installed in tidal channels around the country will provide all of this demand with no adverse impact on the environment apart from capital and maintenance costs, the electricity is free overlapping generating periods will provide continuous power excess “off-peak” and spring tide capacity can be used to produce hydrogen © clf anderson diagram only not to scale 230 metres Plan view of a practical and effective alternative tidal flow energy extraction system

Island of Stroma Skerry Duncansby Head St Johns Point Gills Bay Ness of Hunna Caithness Pentland Firth Inner Sound of Stroma Swilkie Point Scarton Langaton Red Head the island forms part of the barrier 900 mw capacity barrier 1 kilometre the Inner Sound of Stroma with six tidal barrier sections in 30 metres depth of water this group of barrier sections will produce 900 Megawatts shipping can pass freely around or between the barrier sections

Island of Stroma Skerry Duncansby Head St Johns Point Gills Bay Ness of Hunna Caithness Pentland Firth Inner Sound of Stroma Swilkie Point Scarton Langaton Red Head 900 mw capacity barrier 1 kilometre the island forms part of the barrier the Inner Sound of Stroma with six tidal barrier sections in 30 metres depth of water this group of barrier sections will produce 900 Megawatts shipping can pass freely around or between the barrier sections

shipping can pass freely around or between the barrier sections
Island of Stroma Skerry Duncansby Head St Johns Point Gills Bay Ness of Hunna Caithness Pentland Firth Inner Sound of Stroma Swilkie Point Scarton Langaton Red Head 900 mw capacity barrier 1 kilometre the island forms part of the barrier the Inner Sound of Stroma with six tidal barrier sections in 30 metres depth of water shipping can pass freely around or between the barrier sections

Some further details 1 Automatic by-pass channel gates 2
index page 2 Uni-flow river unit return to this index page 3 Floating objects 4 Maintenance 5 Some proposed tidal flow turbines start 6 Voith-Schneider rotors 7 Small river units return to the start of the presentation

Automatic by-pass channel gates

© clf anderson diagram only not to scale
Bypass channel gates venturi passages keep the gate firmly open tidal flow gate hinge chamber “squish” chamber bypass channel “squish” chamber the “displacement phase” gate is self opening and self closing it is foam filled so as to be slightly buoyant and has a thrust bearing at the top © clf anderson diagram only not to scale

Bypass channel gates the inlet passage flow pushes the gate open tidal flow the “displacement phase” gate is self opening and self closing it is foam filled so as to be slightly buoyant and has a thrust bearing at the top the gate is opened and closed by the change in tidal flow direction © clf anderson diagram only not to scale

Bypass channel gates the inlet passage flow pushes the gate open tidal flow index page the “displacement phase” gate is self opening and self closing it is foam filled so as to be slightly buoyant and has a thrust bearing at the top the gate is opened and closed by the change in tidal flow direction the gate is prevented from slamming by the “squish” chamber damping action the gate only closes fully when the “squish” chamber contents have escaped © clf anderson diagram only not to scale

Uni-flow river unit

uni-flow river unit upstream downstream narrowing entrance channel wide exit channel a uni-flow unit has only one downstream by-pass channel © clf anderson diagrammatic only not to scale

uni-flow river unit clockwise rotor on this unit upstream anti-clockwise rotor on this unit a pair of mirror-imaged rotors may share a single by-pass vent passage to the downstream level © clf anderson diagrammatic only not to scale

uni-flow river unit clockwise rotor on this unit upstream anti-clockwise rotor on this unit a venturi passage may be used to ensure a low water level at the outlet of the positive displacement vent © clf anderson diagrammatic only not to scale

uni-flow river unit upstream downstream narrowing entrance channel wide exit channel index page river bed a “bulbous bow” ship profile may be used to ensure a low water level at the outlet of the positive displacement vent © clf anderson diagrammatic only not to scale

Floating objects

Floating objects FREE wheel rotor liferaft liferaft the trash screen can be sloped to provide a “beach” to allow any floating objects swept into the entry to be safely landed © clf anderson diagrammatic only not to scale

Floating objects FREE wheel rotor Protection skirt the skirt extends below the waterline level on each side it may be arranged to float up and down with the tide its purpose is to deflect the top layer of tidal flow parallel with the face of the barrier it prevents floating objects from being carried into the rotor and guide vanes © clf anderson diagrammatic only not to scale

the skirt deflects the surface water to protect floating objects such as small disabled vessels, life rafts or swimmers index page protection skirt protection skirt escape channel Protection skirt © clf anderson diagram only not to scale

Maintenance

Maintenance the generator units are not normally manned and are remotely controlled each group of rotor units could be fitted with a current sheltered dock for workboats a helideck on each group will permit rapid evacuation of a casualty Stroma 3 security considerations may prefer inspection and maintenance access to be by helicopter only with no access being made available from the sea © clf anderson diagram only not to scale

Maintenance access roadways are installed during final commissioning
Stroma 3 access roadways are installed during final commissioning equipment such as a mobile crane and HP water jetting equipment could be held on each group of generator units as required © clf anderson diagram only not to scale

Maintenance trash screens are self cleaning when the current changes direction Note: screen bars run horizontally not vertically as shown in this diagram the screens prevent access to the rotor by cetaceans, pinipeds and large fish each screen is designed to be easily lifted from its slot mounting and replaced inspection of underwater parts can be by ROVs (remotely operated vehicles) shellfish accretions can be removed using high pressure water jetting robots © clf anderson diagram only not to scale

Maintenance isolation gates open isolation gates closed conventional canal lock gates may be used isolation gates are moved at slack tide to allow maintenance on the rotor and the drive these gates would be kept closed until the unit is in place and fully commissioned power would then be immediately available to produce revenue © clf anderson diagram only not to scale

Maintenance isolation gates open gates may be made adjustable to control the entry flow isolation gates closed gate disk base top bearing high pressure water is pumped down the gate spindle to flush out grit and to lift the gate to allow it to be turned during slack tide reaction jets at the blade tips may be used to turn each gate floor of guide chamber these are the only underwater bearings in the whole device automatic gates can be used to close off the bypass channels © clf anderson diagram only not to scale

Maintenance this unit is in operation this unit is fully isolated if required, the isolation gates can be fully sealed using water bags to allow the water level in the guide chamber to lowered for extensive maintenance the water bags would be retained in place regardless of the state of the tide © clf anderson diagram only not to scale

Maintenance flow guides water-filled bags water bags alone may be used to isolate the rotor chamber thus saving costs © clf anderson diagram only not to scale

Maintenance index page the chamber may be provided with guide slots in the sides of the water passages isolation gates may simply be lowered into place when isolation is required high pressure water jets at the bottom edges of each gate will clear shellfish and weed from the guidance slots as it is lowered into place conventional canal lock gates may also be used © clf anderson diagram only not to scale

Some proposed tidal flow turbines

Some present tidal flow energy extraction concepts
these use fixed or free floating underwater generator units to extract a very small proportion of the energy which could be available from the tidal current

there is a significant risk that ships
will collide with the surface towers of these underwater generators especially in fog or bad weather Proposed IMECHE * high aspect ratio tidal flow rotor Note the cavitation trails from the blade tips, the small blade surface area, the very small area of current flow which is being harvested and the complicated and expensive foundation all of the engineering and electricals are under water unless the whole rotor assembly is able to swivel through 180° energy can only be extracted from one direction of tidal current which halves the generation time and the repayment revenue stream maintenance work, such as shaft seal replacement, will be problematical and expensive power appears to be exported by a cable under the sea bed * Institution of Mechanical Engineers leaflet “UK Energy Policy - Challenges and opportunities”

twin rotor tidal flow generator proposed by Marine Current Turbines Ltd.
the rotors are very close to the water surface and thus are vulnerable to collision with surface vessels

comments by clf anderson
* water has roughly 800 times the density of air † † i.e. 100 square kilometers per gigawatt comments by clf anderson

aspect ratio tidal flow rotor
Proposed RGU * high aspect ratio tidal flow rotor Note the cavitation trails from the blade tips, the small blade surface area, the very small area of current flow which is being harvested and the complicated and expensive foundation all of the engineering and electricals are under water maintenance work, such as shaft seal replacement, will be problematical and expensive collision with a basking shark or lost freight container will cause catastrophic damage * Robert Gordon University, Aberdeen -

these rotor units can swivel round so as to be able to
extract energy from both directions of tidal flow

Gorlov rotors are strung along a small diameter spindle
Verdant Power Gorlov rotors are strung along a small diameter spindle the generator is installed at one end of the long spindle

an experimental underwater
tethered tidal flow energy extraction device by TidEl all of the engineering and electricals are under water the electric cable which takes power ashore must flex through 180° four times every day scaling up will cause cavitation problems at the blade tips maintenance will be problematical index page

Voith-Schneider rotors

A Voith-Schneider rotor may be used
for extracting one-way river flow energy or extracting two-way tidal flow energy

the rotor has almost all of its components above the water level
the generator is also above water level the rotor blades can reach to almost the full depth of the water channel very large sized rotor blades suffer from cavitation

A Voith Schneider rotor fitted in a venturi channel in a river
plan view of venturi casing positive displacement mode on this side of the channel blade control rods river flow rotor runs clockwise control rod anchorage each blade is “feathered” to travel against the flow A Voith Schneider rotor fitted in a venturi channel in a river this rotor has high efficiency but is complicated and expensive it is inherently self regulating on loss of electrical load © clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale

the rotor may be used in small tidal channels
plan view of venturi casing blade control rods rotor runs clockwise flood tide control rod anchorage lost water flow energy the rotor may be used in small tidal channels the control rod anchorage must be reversed at slack water otherwise the rotor will run in alternate directions on each tide © clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale

rotor blade and guide vane shapes are diagrammatic only not to scale
venturi casing lost water flow energy rotor runs clockwise ebb tide control rod anchorage has been reversed change of control rod anchorage maintains the same direction of rotation for both directions of current flow which permits the use of roller clutches to allow the generators to motor ahead of the rotor at slack tide most of the engineering and all of the electricals are above the water © clf anderson rotor blade and guide vane shapes are diagrammatic only not to scale

index page

Uni Flow Energy Extraction generator
for extraction of flow energy from small rivers

units may be floated into place using buoyancy chambers and/or airbags
buoyancy chambers are filled with sand or gravel ballast when each unit is installed river flow the water level rises in each entrance channel as the flow slows down the water level falls in each exit chamber three prefabricated Uniflow channel units placed side by side in a river © clf anderson diagram only not to scale units may be floated into place using buoyancy chambers and/or airbags each prefabricated unit rests on the riverbed and may be piled into place

Uniflow channel unit plan view
side wall of exit channel side wall of entrance ramp exit flow entrance flow turbine runner duct turbine runner Uniflow channel unit plan view © clf anderson diagram only not to scale

Uniflow generator unit
generator and thrust bearing are installed above the maximum river flood level supports are adjustable so as to allow accurate levelling of the power unit to accommodate the slope of the river bed dimensions and type of turbine runner vary according to water depth and flow rate flood water can spill over the top of the unit drive shaft guide tube trash screen river flow direction turbine runner note: inlet slope is exaggerated a venturi system may be used to apply a vacuum to the base to compact the river bed river bed level © clf anderson diagram only not to scale Uniflow generator unit

alternative river generator unit
generator and thrust bearing are installed above the maximum river flood level prefabricated entrance channel spun concrete pipe waterfall profile spun concrete pipe exit chamber fixed to the river bed river bed level © clf anderson diagram only not to scale alternative river generator unit

a Deriaz turbine runner with the blades closed
© clf anderson a Deriaz turbine runner with the blades closed Kaplan runners have a similar layout an Archimedian screw may be used on many sites

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of the presentation

FREE* wheel an environmentally benign energy source

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