Severn Estuary Tidal Energy - Regensw
Severn Tidal Power Feasibility Study
19 March 2009 – Severn Tidal Power Overview and Implications of Tidal Power Technologies Peter Kydd Director of Strategic Consulting Parsons Brinckerhoff
Severn Estuary Tidal Energy
Overview and Implications of Conventional and Innovative Tidal Technologies Agenda •
Overview of Conventional and Innovative Technologies for Tidal Power Generation
•
To summarise innovative technologies considered during the First Phase of the Feasibility Study
•
Review of Potential Benefits and Issues
•
Implications
•
Questions
Severn Estuary Tidal Energy
Overview and Implications of Innovative and Conventional Tidal Technologies Four Main Categories •
Tidal Barrages - fixed barrage with up to 9m diameter turbines and large sluice gates operating on head difference between basin and sea level
•
Tidal Lagoons – similar to tidal barrages but creates a basin by impounding between two points on the same shore or offshore – uses similar turbines and sluices as tidal barrages
•
Tidal Reefs – fixed barrage with 28m+ diameter inclined turbines operating on a constant 2m head differential
•
Tidal Fence – partial or no barrage structure with a linear array of ducted tidal stream turbines (16m+ diameter) constructed across the estuary to generate using a combination of the tidal currents and the head created as a consequence of multiple turbines impeding the flow
Severn Estuary Tidal Energy
Short-listed Options Tidal Barrages: – B3 – Cardiff Weston – B4 – Shoots – B5 - Beachley
•
Tidal Lagoons: – L2 – Fleming (Welsh Grounds) – L3 – Bridgwater Bay
•
Cardiff Weston proposal well understood but other options are less well known.
Severn Estuary Tidal Energy
Draft Short-listed Options B3 – Cardiff - Weston
Severn Estuary Tidal Energy
Draft Short-listed Options B4 – Shoots
Severn Estuary Tidal Energy
Draft Short-listed Options B4 – Shoots (B5 - Beachley similar but smaller)
Severn Estuary Tidal Energy
Draft Short-listed Options B5 – Beachley
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon (Welsh Grounds)
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon – Aerial View of Turbines
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon – Proposed Turbine Arrangement
Severn Estuary Tidal Energy
Draft Short-listed Options L3 – Bridgwater Bay
Severn Estuary Tidal Energy
Conventional Tidal Technologies
Conventional Turbine Technologies Bulb Turbine - generator mounted in a bulb on the main turbine axis - can be used used in both directions. Proposed for B1, B2 and B3 and lagoons. Used at La Rance (5.5m diameter) and Sihwa, Korea ( 7.5m diameter) Straflo Turbine – instead of containing the generator in a bulb, it is located around the turbine blade rim – more compact but less flexible operationally – designed for ebb only operation. Proposed for B4 and B5. Used at Annapolis Royal, Canada (7.6m diameter). Both types are used on many run-of-river hydropower plants around the world. Severn Estuary Tidal Energy
Conventional Technologies Conventional Turbine Technologies Run-of-River Plants using Bulb turbines include • Rock Island, USA – 8 x 53MW (1980) • Nina, China – 4 x 40MW (2001) • Santo Antonio, Brazil – 44 x 72MW (2009) Straflo Turbines – over 100 units mainly in Europe (Rhine etc) Conventional Turbines not suitable for tidal applications • Impulse Turbines including Pelton, Turgo, Crossflow • Francis turbines – suited to higher high head applications • Propellor turbines – constant loads or flows • Kaplan turbines similar to Bulb turbines but operate on higher heads – (up to 10m diameter, 200MW) Severn Estuary Tidal Energy
Conventional Tidal Technologies Bulb Turbines
Operate typically between 45 and 65 rpm Severn Estuary Tidal Energy
Conventional Tidal Technologies Straflo Turbines
Severn Estuary Tidal Energy
Conventional Tidal Technologies
•
Opportunities for Mitigation Previous studies on mature technologies focused on maximising energy
•
Energy abstracted approximately proportional to environmental impact
•
What opportunities do mature technologies bring to minimise adverse impacts? – – – – – –
Pumping to negate loss of high water level Can operate in ebb and flood mode (bulb turbines) Increase barrage permeability (by sluicing during generation / increasing turbine capacity) to reduce loss of tidal range (will reduce energy yield) High level sluices to assist fish passage (requires more sluices) Refine turbine design to minimise sudden pressure drops / rotor speed Limited periods of non-generation to temporarily restore natural tide cycle (for example to minimise fish damage, to preserve salt-marsh or to manage extreme flood events)
Severn Estuary Tidal Energy
Conventional Tidal Technologies
•
Modes of Operation Ebb Only - tidal range reduced, mainly through increased low tide level (illustrated right on Springs and, lower right - Neaps)
•
Ebb and Flood – tidal range reduced but equal loss of high and low water
•
Ebb Only + pumping – increases energy yield and compensates for any loss at high tide
Severn Estuary Tidal Energy
Embryonic Turbine Technologies
Tidal Current Turbines (Tidal Fence) Largest Installation: 2 x 600kW Diameter: 16m per 600kw rotor Speed: 15 rpm Scale up from 600kW to 1.6MW
Severn Estuary Tidal Energy
Embryonic Turbine Technologies VLH Turbine (Tidal Reef) Scale from 4.5m
to 28m diameter? Designed and Patented only to 5.5m diameter.
VLH turbine can operate in ebb mode only (inclined at 35 degrees) 4.5m diameter generates 410kW Speed: 35 rpm Very low flow velocity (>2m/s) but relatively low power per m diameter Manufactured by MJ2 Technologies of France to a max size of 5.5m Severn Estuary Tidal Energy
Innovative Technologies Proposed for Severn Summary of Innovative Technologies Proposed for Severn Option F1 – Tidal Fence Concept – Proposed by Severn Tidal Fence Group (STFG) – F1a Cardiff to Weston – 256 tidal stream ducted turbines enclosed within partial barrage – F1b Minehead to Aberthaw – 800 tidal stream ducted turbines
Severn Estuary Tidal Energy
Innovative Technologies Proposed for Severn Summary of Innovative Technologies Proposed for Severn Option R1 – Tidal Reef Concept • •
Evans Engineering proposal –vertical axis turbines contained within syphonic modules (constant 2m depth) Atkins study for RSPB using alternate design and turbine configurations to achieve the same objective of 2m tidal variance
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Fence Option F1a – Tidal Fence from Cardiff to Weston Originally proposed by STFG using 256 5MW tidal stream turbines Main Issues: – Extrapolation from 16m 0.6MW propeller to 5MW propeller including blade diameter (18m), cost and development time – Impact on navigation from reduced top water level (c750mm to 1m for 3.5TWh/yr) and effects of extreme changes in currents through navigation passages – Subsequently modelled using anticipated output from 18m dia blade (1MW) resulting in top water level reduction of c 300mm but significantly reduced energy yield. – Concept of channelling greater flow through turbine cowls and restricting flow passages between will also encourage greater % of fish to pass through turbine blade swept area by comparison with conventional tidal stream
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Fence Option F1b – Minehead to Aberthaw Tidal Fence STFG subsequently proposed an alternate location between Aberthaw and Minehead using 800 1.6MW tidal stream turbines Key Improvements over F1a: – Extrapolation from 0.6MW turbine to 1.6MW more feasible and greater availability of deeper water to accommodate required blade length – Reduction in top water level c 0.3m for energy yield of 3.3TWh/a Key Issues – Development and testing time required to achieve over 100% increase in individual turbine capacity by comparison with the largest existing installation at Strangford Lough – Uncertainty of achievability – Changes in water currents and impacts on navigation – Supply chain pressures for manufacture and installation of 800 units and subsequent replacement cycles (assumed installation of 100 units per year) – Time required to firm up technology feasibility and costs prior to committing to a major implementation in the Severn
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Fence Energy Costs Modelled assuming a theoretical “level playing field” with other options Assumed development and testing timelines were not an issue to assess if technologies were competitive with other technologies The reduction in energy yield for Option F1a resulted in an unacceptably high cost per energy. Energy costs are in the order of 60% higher than large tidal barrages and tidal lagoons assessed under the fair basis method Note:The fair basis approach applies common assumptions and across all option costs (eg design, site investigation, unit rates for civil works, operating cost assumptions etc) except for option specific costs (eg tidal stream turbine costs and replacement periods).
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Fence Environmental Effects Principal effects are summarised below: – Accelerated currents through and around the Tidal Fence are likely to exert geomorphological changes including scour in the shipping channel and at the open ends potentially causing scour in the inter-tidal area; these effects require further study; – Reduction in upstream tidal range due to the reduction in flow speed. – Area of intertidal area lost upstream of the fence owing to the altered tidal regime is estimated as: – F1a 2,000 ha – F1b 2,800 ha – Accelerated water currents through the structure require further study in relation to navigation, both in terms of safety of passage through the structure and potential for ship impact; – Other effects such as on water quality, geomorphological response, and fish are uncertain and require further research.
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Tidal Reef Concept Originally proposed by Evans Engineering Main Issues: – Original concept attractive in terms of objectives but main issue is the practicality of how they may be achieved – Several variants proposed as the concept was developed by Evans over summer/autumn 2008 – Predicted energy output reduced from initial estimate of 20TWh to between 11 and 14TWh by Evans Engineering (27 November 2008 submission) – Turbine type, physical size, wave damage, cavitation risks and configuration –
1m reduction in high water level
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Tidal Reef Alternative RSPB Atkins Review (December 2008) Accepted Evans objectives but rejected Evans configuration. Proposed alternative configuration.
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Atkins Variant Main Issues: – Control to achieve constant 2m head differential on ebb and flood tides – Predicted energy output (20TWh or 13TWh) – Development of suitable turbine types (type and scale) – Proposal based on ebb only prototype (VLH turbine) – 1m reduction in high water level (impacts navigation) – Requires navigation lock – Depth of water requirements for large diameter turbines – Time required to firm up technology feasibility and costs prior to committing to a major implementation in the Severn
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Reef Energy Costs Note: Fair basis and no implementation delays assumed for comparative purposes The indicative results for option R1 (Minehead to Aberthaw) are in the order of 40% higher than large tidal barrages and tidal lagoons assessed under the fair basis method
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Reef Environmental Effects Principal impacts are summarised below: – – –
–
Symmetrical reduction in upstream tidal range with the spring high water level reduced and the spring low water level increased by one metre each. The intertidal area lost upstream of the fence is estimated as 8,600 ha. The accelerated water currents through the reef require further study in relation to navigation, both in terms of safety of passage through the structure and potential for ship impact. Other effects such as on water quality, geomorphological change, fish (Millau pilot tests on VLH turbine reveal mortality rates between 0% and 16% increasing from the turbine hub to outer rim) are uncertain and require further research.
Severn Estuary Tidal Energy
Implications Main Implications Objective of reducing environmental effects offset by: • •
Relatively High Energy Costs Technology Development and Demonstration Timeline
Uncertain potential effects: • • • •
Geomorphological response Navigation impacts Fish mortality Water quality
Innovative Technology Fund – will help inform timelines and costs Can objective of reduced environmental effects be achieved using existing mature tidal technology? To be considered in Phase 2.
Severn Estuary Tidal Energy
19 March 2009 – Severn Tidal Power Overview and Implications of Tidal Power Technologies Peter Kydd Director of Strategic Consulting Parsons Brinckerhoff
Severn Estuary Tidal Energy
Overview and Implications of Conventional and Innovative Tidal Technologies Agenda •
Overview of Conventional and Innovative Technologies for Tidal Power Generation
•
To summarise innovative technologies considered during the First Phase of the Feasibility Study
•
Review of Potential Benefits and Issues
•
Implications
•
Questions
Severn Estuary Tidal Energy
Overview and Implications of Innovative and Conventional Tidal Technologies Four Main Categories •
Tidal Barrages - fixed barrage with up to 9m diameter turbines and large sluice gates operating on head difference between basin and sea level
•
Tidal Lagoons – similar to tidal barrages but creates a basin by impounding between two points on the same shore or offshore – uses similar turbines and sluices as tidal barrages
•
Tidal Reefs – fixed barrage with 28m+ diameter inclined turbines operating on a constant 2m head differential
•
Tidal Fence – partial or no barrage structure with a linear array of ducted tidal stream turbines (16m+ diameter) constructed across the estuary to generate using a combination of the tidal currents and the head created as a consequence of multiple turbines impeding the flow
Severn Estuary Tidal Energy
Short-listed Options Tidal Barrages: – B3 – Cardiff Weston – B4 – Shoots – B5 - Beachley
•
Tidal Lagoons: – L2 – Fleming (Welsh Grounds) – L3 – Bridgwater Bay
•
Cardiff Weston proposal well understood but other options are less well known.
Severn Estuary Tidal Energy
Draft Short-listed Options B3 – Cardiff - Weston
Severn Estuary Tidal Energy
Draft Short-listed Options B4 – Shoots
Severn Estuary Tidal Energy
Draft Short-listed Options B4 – Shoots (B5 - Beachley similar but smaller)
Severn Estuary Tidal Energy
Draft Short-listed Options B5 – Beachley
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon (Welsh Grounds)
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon – Aerial View of Turbines
Severn Estuary Tidal Energy
Draft Short-listed Options L2 – Fleming Lagoon – Proposed Turbine Arrangement
Severn Estuary Tidal Energy
Draft Short-listed Options L3 – Bridgwater Bay
Severn Estuary Tidal Energy
Conventional Tidal Technologies
Conventional Turbine Technologies Bulb Turbine - generator mounted in a bulb on the main turbine axis - can be used used in both directions. Proposed for B1, B2 and B3 and lagoons. Used at La Rance (5.5m diameter) and Sihwa, Korea ( 7.5m diameter) Straflo Turbine – instead of containing the generator in a bulb, it is located around the turbine blade rim – more compact but less flexible operationally – designed for ebb only operation. Proposed for B4 and B5. Used at Annapolis Royal, Canada (7.6m diameter). Both types are used on many run-of-river hydropower plants around the world. Severn Estuary Tidal Energy
Conventional Technologies Conventional Turbine Technologies Run-of-River Plants using Bulb turbines include • Rock Island, USA – 8 x 53MW (1980) • Nina, China – 4 x 40MW (2001) • Santo Antonio, Brazil – 44 x 72MW (2009) Straflo Turbines – over 100 units mainly in Europe (Rhine etc) Conventional Turbines not suitable for tidal applications • Impulse Turbines including Pelton, Turgo, Crossflow • Francis turbines – suited to higher high head applications • Propellor turbines – constant loads or flows • Kaplan turbines similar to Bulb turbines but operate on higher heads – (up to 10m diameter, 200MW) Severn Estuary Tidal Energy
Conventional Tidal Technologies Bulb Turbines
Operate typically between 45 and 65 rpm Severn Estuary Tidal Energy
Conventional Tidal Technologies Straflo Turbines
Severn Estuary Tidal Energy
Conventional Tidal Technologies
•
Opportunities for Mitigation Previous studies on mature technologies focused on maximising energy
•
Energy abstracted approximately proportional to environmental impact
•
What opportunities do mature technologies bring to minimise adverse impacts? – – – – – –
Pumping to negate loss of high water level Can operate in ebb and flood mode (bulb turbines) Increase barrage permeability (by sluicing during generation / increasing turbine capacity) to reduce loss of tidal range (will reduce energy yield) High level sluices to assist fish passage (requires more sluices) Refine turbine design to minimise sudden pressure drops / rotor speed Limited periods of non-generation to temporarily restore natural tide cycle (for example to minimise fish damage, to preserve salt-marsh or to manage extreme flood events)
Severn Estuary Tidal Energy
Conventional Tidal Technologies
•
Modes of Operation Ebb Only - tidal range reduced, mainly through increased low tide level (illustrated right on Springs and, lower right - Neaps)
•
Ebb and Flood – tidal range reduced but equal loss of high and low water
•
Ebb Only + pumping – increases energy yield and compensates for any loss at high tide
Severn Estuary Tidal Energy
Embryonic Turbine Technologies
Tidal Current Turbines (Tidal Fence) Largest Installation: 2 x 600kW Diameter: 16m per 600kw rotor Speed: 15 rpm Scale up from 600kW to 1.6MW
Severn Estuary Tidal Energy
Embryonic Turbine Technologies VLH Turbine (Tidal Reef) Scale from 4.5m
to 28m diameter? Designed and Patented only to 5.5m diameter.
VLH turbine can operate in ebb mode only (inclined at 35 degrees) 4.5m diameter generates 410kW Speed: 35 rpm Very low flow velocity (>2m/s) but relatively low power per m diameter Manufactured by MJ2 Technologies of France to a max size of 5.5m Severn Estuary Tidal Energy
Innovative Technologies Proposed for Severn Summary of Innovative Technologies Proposed for Severn Option F1 – Tidal Fence Concept – Proposed by Severn Tidal Fence Group (STFG) – F1a Cardiff to Weston – 256 tidal stream ducted turbines enclosed within partial barrage – F1b Minehead to Aberthaw – 800 tidal stream ducted turbines
Severn Estuary Tidal Energy
Innovative Technologies Proposed for Severn Summary of Innovative Technologies Proposed for Severn Option R1 – Tidal Reef Concept • •
Evans Engineering proposal –vertical axis turbines contained within syphonic modules (constant 2m depth) Atkins study for RSPB using alternate design and turbine configurations to achieve the same objective of 2m tidal variance
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Fence Option F1a – Tidal Fence from Cardiff to Weston Originally proposed by STFG using 256 5MW tidal stream turbines Main Issues: – Extrapolation from 16m 0.6MW propeller to 5MW propeller including blade diameter (18m), cost and development time – Impact on navigation from reduced top water level (c750mm to 1m for 3.5TWh/yr) and effects of extreme changes in currents through navigation passages – Subsequently modelled using anticipated output from 18m dia blade (1MW) resulting in top water level reduction of c 300mm but significantly reduced energy yield. – Concept of channelling greater flow through turbine cowls and restricting flow passages between will also encourage greater % of fish to pass through turbine blade swept area by comparison with conventional tidal stream
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Fence Option F1b – Minehead to Aberthaw Tidal Fence STFG subsequently proposed an alternate location between Aberthaw and Minehead using 800 1.6MW tidal stream turbines Key Improvements over F1a: – Extrapolation from 0.6MW turbine to 1.6MW more feasible and greater availability of deeper water to accommodate required blade length – Reduction in top water level c 0.3m for energy yield of 3.3TWh/a Key Issues – Development and testing time required to achieve over 100% increase in individual turbine capacity by comparison with the largest existing installation at Strangford Lough – Uncertainty of achievability – Changes in water currents and impacts on navigation – Supply chain pressures for manufacture and installation of 800 units and subsequent replacement cycles (assumed installation of 100 units per year) – Time required to firm up technology feasibility and costs prior to committing to a major implementation in the Severn
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Fence Energy Costs Modelled assuming a theoretical “level playing field” with other options Assumed development and testing timelines were not an issue to assess if technologies were competitive with other technologies The reduction in energy yield for Option F1a resulted in an unacceptably high cost per energy. Energy costs are in the order of 60% higher than large tidal barrages and tidal lagoons assessed under the fair basis method Note:The fair basis approach applies common assumptions and across all option costs (eg design, site investigation, unit rates for civil works, operating cost assumptions etc) except for option specific costs (eg tidal stream turbine costs and replacement periods).
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Fence Environmental Effects Principal effects are summarised below: – Accelerated currents through and around the Tidal Fence are likely to exert geomorphological changes including scour in the shipping channel and at the open ends potentially causing scour in the inter-tidal area; these effects require further study; – Reduction in upstream tidal range due to the reduction in flow speed. – Area of intertidal area lost upstream of the fence owing to the altered tidal regime is estimated as: – F1a 2,000 ha – F1b 2,800 ha – Accelerated water currents through the structure require further study in relation to navigation, both in terms of safety of passage through the structure and potential for ship impact; – Other effects such as on water quality, geomorphological response, and fish are uncertain and require further research.
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Tidal Reef Concept Originally proposed by Evans Engineering Main Issues: – Original concept attractive in terms of objectives but main issue is the practicality of how they may be achieved – Several variants proposed as the concept was developed by Evans over summer/autumn 2008 – Predicted energy output reduced from initial estimate of 20TWh to between 11 and 14TWh by Evans Engineering (27 November 2008 submission) – Turbine type, physical size, wave damage, cavitation risks and configuration –
1m reduction in high water level
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Tidal Reef Alternative RSPB Atkins Review (December 2008) Accepted Evans objectives but rejected Evans configuration. Proposed alternative configuration.
Severn Estuary Tidal Energy
Evaluation Issues – Tidal Reef Option R1 – Atkins Variant Main Issues: – Control to achieve constant 2m head differential on ebb and flood tides – Predicted energy output (20TWh or 13TWh) – Development of suitable turbine types (type and scale) – Proposal based on ebb only prototype (VLH turbine) – 1m reduction in high water level (impacts navigation) – Requires navigation lock – Depth of water requirements for large diameter turbines – Time required to firm up technology feasibility and costs prior to committing to a major implementation in the Severn
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Reef Energy Costs Note: Fair basis and no implementation delays assumed for comparative purposes The indicative results for option R1 (Minehead to Aberthaw) are in the order of 40% higher than large tidal barrages and tidal lagoons assessed under the fair basis method
Severn Estuary Tidal Energy
Evaluation Outputs – Tidal Reef Environmental Effects Principal impacts are summarised below: – – –
–
Symmetrical reduction in upstream tidal range with the spring high water level reduced and the spring low water level increased by one metre each. The intertidal area lost upstream of the fence is estimated as 8,600 ha. The accelerated water currents through the reef require further study in relation to navigation, both in terms of safety of passage through the structure and potential for ship impact. Other effects such as on water quality, geomorphological change, fish (Millau pilot tests on VLH turbine reveal mortality rates between 0% and 16% increasing from the turbine hub to outer rim) are uncertain and require further research.
Severn Estuary Tidal Energy
Implications Main Implications Objective of reducing environmental effects offset by: • •
Relatively High Energy Costs Technology Development and Demonstration Timeline
Uncertain potential effects: • • • •
Geomorphological response Navigation impacts Fish mortality Water quality
Innovative Technology Fund – will help inform timelines and costs Can objective of reduced environmental effects be achieved using existing mature tidal technology? To be considered in Phase 2.
Severn Estuary Tidal Energy
