A FEASIBILITY STUDY INTO THE USE OF AN ARCHEMEDIAN SCREW TURBINE FOR HYDROELETRIC GENERATION AT TEDDINGTON WEIR, LONDON. 1 st JULY 2009.

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A FEASIBILITY STUDY INTO THE USE OF AN ARCHEMEDIAN SCREW TURBINE FOR HYDROELETRIC GENERATION AT TEDDINGTON WEIR, LONDON 1 st JULY 2009 Prepared Ham United Group (HUG) Prepared Paul

1 A FEASIBILITY STUDY INTO THE USE OF AN ARCHEMEDIAN SCREW TURBINE FOR HYDROELETRIC GENERATION AT TEDDINGTON WEIR, LONDON 1 st JULY 2009 Prepared Ham United Group (HUG) Prepared Paul Parker/Michael Moreno for: by: Peter Rixon Thames Renewables 46 Platts Eyot Hampton TW12 2HF Tel: Tel: HUG@richenvironmentnet.org.uk paulparker@thamesrenewables.com

2 With our compliments Thames Renewables Issue/revision DRAFT Issue Remarks Date 01/08/09 Prepared by MM Signature Checked by PP Signature Project number TRE 206 Teddington Weir Hydropower Feasibility Study 2

3 IMPORTANT NOTICE Whilst reasonable steps have been taken to ensure that the information contained within this Report is correct, you should be aware that the information contained within it may be incomplete, inaccurate or may have become out of date. Accordingly, Thames Renewables, its agents, contractors and sub-contractors make no warranties or representations of any kind as to the content of this Report or its accuracy and, to the maximum extent permitted by law, accept no liability whatsoever for the same including, without limit, for direct, indirect or consequential loss, business interruption, loss of profits, production, contracts, goodwill or anticipated savings. Any person making use of this Report does so at their own risk. Nothing in this Report is intended to be or should be interpreted as an endorsement of, or recommendation for, any supplier, service or product. Teddington Weir Hydropower Feasibility Study 3

4 Contents 1.0 Introduction Hydropower Machinery The Archimedean Screw The Propellor or Kaplan Turbine Requirements for Installation the Archimedean Screw Hydrology and Energy Capture Flow Duration Curve Head Duration Curve Environmental Site Audit Abstraction license Derogation Consent Impoundment License Conservation Fisheries Flood risk Effects on navigation Costs and Economics Installation Costs Income Grant Funding Cost/Benefit Calculations Conclusion and Recommendations Teddington Weir Hydropower Feasibility Study 4

1.0 Introduction Ham United Group (HUG) is a local community group based in Richmond whose aim is to improve and enhance the environment and quality of life for residents in Ham.

5 1.0 Introduction Ham United Group (HUG) is a local community group based in Richmond whose aim is to improve and enhance the environment and quality of life for residents in Ham. This study has been carried out as a result of HUG s interest in investigating the possibilities of installing a hydropower scheme at Teddington Weir. Figure 1: Teddington Weir layout Teddington Weir is situated on the River Thames (OS grid reference TQ ) approximately 4.8 miles downstream from Molesey Lock and 3 miles upstream from Richmond Lock. It is on the limit of the tidal Thames and between Teddington and Richmond the river is semi-tidal, meaning that it is tidal for two hours before and two hours after high tide. It is also the largest weir on the Thames as other weirs may have more gates but none are as big as those at Teddington, the largest gate (Roller Sluice) being 4.5mx15m. Thames Renewables has been asked to report on the potential energy yield at the site, appropriate technologies, and to identify any potential impediments to a scheme. Teddington Weir Hydropower Feasibility Study 5

6 2.0 Hydropower Machinery There are a number of types of system for generating power from flowing water. Generally speaking the selection of the specific type of technology depends very much on the location, turbine type technologies generally tend to be used more for higher head applications. Propeller type turbines and Archimedean screws are more suited to low head high volume situations. All solutions will require protection from large objects in the form of a trash screen, and a means of stopping the equipment usually via a sluice gate. There will be a balance of system required to convert the kinetic energy of the equipment into electrical energy via a gearbox and generator, together with the associated control gear which will required a housing. Teddington is a relatively low head site with a high flow rate and is most suited to two types of plant the Kaplan turbine and the Archimedes screw. The screw tends to have a more favourable financial profile than a Kaplan, despite a possible slightly lower efficiency 2.1 The Archimedean Screw The Archimedean screw, the water extraction screw has been known since ancient times. However by inverting the flow of water, the Archimedes screw pump can be used as a power generator for the extraction of energy. A water power generating facility makes use of the energy difference between two different levels of flowing water by transferring the water from natural bed of the stream at the higher level to the bed at the lower level and effectively extracting its potential energy, which is then made available at the rotor shaft for further use. With an Archimedean screw varying water heads and varying water flow rates upstream and downstream of the screw only marginally affect the efficiency and have no effect on the function or operation of the hydrodynamic screw. This flexibility makes it better suited to the semi-tidal conditions at Teddington where flow direction and head heights can change on a daily basis. With hydrodynamic screws, fine screening installations for protecting against floating objects and fishes, needed for turbines, can be avoided. Debris and fish can pass through the screw unhindered and unharmed. Teddington Weir Hydropower Feasibility Study 6

Another positive aspect claimed by the manufacturers is that the water becomes enriched with oxygen, which in turn improves the quality of the water downstream.

7 Another positive aspect claimed by the manufacturers is that the water becomes enriched with oxygen, which in turn improves the quality of the water downstream. Water banking and turbine installations are not only a major obstacle and potential hazard for fishes travelling upstream but also for fishes travelling downstream. Water power generation of any type is an obstacle for the spawning migration of migratory fishes. In many waterways this affects the European eel because eels are considerably affected by Kaplan turbines and Francis turbines. But grey trout, salmon or river lamprey are also at risk. The length distribution for the various species show that both small fishes (larger than 8 cm) and large specimens (up to 58 cm) can pass through the hydrodynamic screw without harm. Even relatively small and weak fish such as gudgeon or the miller's thumb have been able to pass through the hydrodynamic screw without injury. The overall result is that the hydrodynamic screw is very friendly to fishes and highly suitable for fish migration. According to present knowledge, the fishes suffer, if at all, only minor injury in form of damaged scales and bruising. The key advantages of the Archimedean screw are therefore as follows: No control system the screw matches itself automatically to the supply frequency and the water supply The efficiency is greater than with comparable waterwheels and small turbines Flat, stable efficiency gradient Robust, long wearing, trouble free No cleaning, little maintenance No fine screens necessary Little underground digging required in comparison to turbines Very friendly to fish Teddington Weir Hydropower Feasibility Study 7

2.2 The Propeller or Kaplan Turbine In the 'propeller' or axial-flow turbines shown, the area through which the water enters is as large as it can be: it is the entire area swept by the blades.

They have the advantage over radial flow turbines that it is technically simpler to improve the efficiency by varying the angle of the blades when the power demand changes.

8 2.2 The Propeller or Kaplan Turbine In the 'propeller' or axial-flow turbines shown, the area through which the water enters is as large as it can be: it is the entire area swept by the blades. Axial-flow turbines are therefore suitable for very large volume flows and have become usual where the head is only a few metres. They have the advantage over radial flow turbines that it is technically simpler to improve the efficiency by varying the angle of the blades when the power demand changes. Axialflow turbines with this feature are called Kaplan turbines. Kaplan turbines are highly efficient at the design flow rate, but less so at lower flow rates. They tend to be more highly engineered and rotate at up to twice the flow rate and are therefore more expensive than Archimedean screws. The complexity of the design also makes the system more prone to maintenance issues, and will require more elaborate trash and fish screening. 2.3 Requirements for Installation the Archimedean Screw Teddington Weir is owned by the Environment Agency (EA) and consists of a fish pass, two large roller sluices, 20 radial gates and a large section of spillway with a flap gate at each end (figure 1). The spillway section can provide a good location to install the hydropower system, or a more discreet solution could be to relocate Flap Gate 1 further upstream to make way for the screw. The screws would be installed by cutting away a section of spillway or removing the flap gate Figure 4: Installation of an Archimedean Screw and replacing with sluice gates in order to provide a path for the water to enter the screws. Each screw would require a width of approximately 4m. The EA will be consulted at an early stage to determine the structural requirements for the scheme. A concrete trough would be constructed within the body of the weir to accommodate the screw itself, Mann Power Consulting indicate that with the available flow a screw with a maximum flow rate of 10 cumecs (m3/s) can be accommodated, provided that a width of 4.5m is available. Teddington Weir Hydropower Feasibility Study 8

9 FLOW (m3/s) 3.0 Hydrology and Energy Capture The kinetic energy of moving water can be converted into electrical energy via the hydropower machine. The key factors in determining how much power can be extracted are; the flow rate of the water and the distance the water falls across the site. In order to predict energy yield this data must either be obtained from bodies such as the EA or collected via a hydrological survey. In the case of Teddington both head and flow rates are well documented and data has been purchased for the site from the EA. 3.1 Flow Duration Curve Flow data gathered by the EA at the Kingston Gauging station was used to determine the flow duration curve for the site. This breaks down the expected flows into a series of percentages which over the year the flow can be expected to match. Therefore for the 50% value or Q50 the flow will meet this value at least 50% of the time. The Q95 value is of particular relevance as this is the figure which the British Hydrological Association recommends is the minimum residual flow left in the river. In the case of Teddington this value is 7.74 cumecs, although the exact figure will be confirmed by the Environment Agency and included within the license conditions. The maximum flow available to the scheme recommended by the EA is the Qmean value which is 65 cumecs. This is far in excess of the proposals given here although it is theoretically possible and advantageous to design to this level. FLOW DURATION CURVE AT TEDDINGTON % 20% 40% 60% 80% 100% % EXCEEDANCE Total River Flow Available Flow Teddington Weir Hydropower Feasibility Study 9

10 FLOW (m3/s) HEAD (m) 3.2 Head Duration Curve The head data for the site was obtained upstream and downstream of Teddington Weir, this data was manipulated to refer to the same ordinance datum and the resulting head was calculated. Resource estimates must also take into account energy losses arising from frictional drag and turbulence, such as those resulting from say trash screens or exit channels. The effective head will always be less therefore than the actual head and a correction value may be used to represent these losses 50mm has been used in this study. HEAD DURATION CURVE AT TEDDINGTON % 20% 40% 60% 80% 100% % EXCEEDANCE Total River Flow Head Teddington Weir Hydropower Feasibility Study 10

11 4.0 Environmental Site Audit The EA released a good practice guide 1 in August This document is designed to give guidance to potential hydropower developers on what will be required by the EA and other statutory consultees. The Environmental Site Audit is a checklist that should be completed for Teddington in the post feasibility phase. Some of the likely key issues are listed below. 4.1 Abstraction license If the turbine is located directly by or within the weir, only an impoundment licence and a flood defence consent may be required, but not an abstraction licence. Flow depletion may not have to be considered, if there is no depleted reach, but other impacts on the river flow may need to be examined. The details of such a scheme need to be discussed with the relevant Environment Agency Area office. 4.2 Derogation Consent The Environment Agency may wish to incorporate a condition within the abstraction licence which reserves a volume for future upstream licensing or improvement to fish passage. The quantity will depend on the location of the site within the catchment, the risk to fish passage, including aspirations for future improvements, the potential for increased future water demand upstream and the time limit of the licence. The quantity will be in accordance with Catchment Abstraction Management Strategies (CAMS) assessments and ecological and fish passage needs. 4.3 Impoundment License If the impoundment (i.e. the weir) is to be increased or altered as it is proposed in this document, then an impoundment licence will be required from the Environment Agency. 1 GOOD PRACTICE GUIDELINES ANNEX TO THE ENVIRONMENT AGENCY HYDROPOWER HANDBOOK THE ENVIRONMENTAL ASSESSMENT OF PROPOSED LOW HEAD HYDRO POWER DEVELOPMENTS Teddington Weir Hydropower Feasibility Study 11

12 4.4 Conservation The site lies adjacent to Ham Lands, which is a local nature reserve. The local authorities of Kingston upon Thames and Richmond appear to be the statutory bodies in this case and may need to be consulted. There might also be a requirement to carry out a full ecological survey to identify any endangered species for example which would need to be protected. 4.5 Fisheries This is one of the busiest fish transit areas on the river and important species such as Salmon and Sea Trout along with over 30 others including migrating eels from the Sargasso will necessitate evidence of no harm, possibly via an independent assessment. Migratory species must be protected possibly with bypass channels around the screw. The effectiveness and efficiency of any existing fish pass will need to be maintained or even improved for a scheme to be consented. Archimedean screw turbines have been demonstrated to cause minimal damage to fish, provided appropriate protection to the leading edge of the screw is applied. For turbines with a tip speed <3.5 m/sec a hard rubber extrusion should be used; for turbines with a greater tip speed a compressible silicone extrusion is required A 100mm trash screen is recommended for use with Archimedean screw intake. A screen of at least 10m2 would be required for a proposed flow of 10m3/s per screw. An angled screen which encourages wildlife to pass over the weir should be selected. 4.6 Flood risk Formal written consent ( flood defence consent ) from the Environment Agency is likely to be required for these activities. To ensure there is no adverse impact on flooding in the locality, a flood risk assessment is likely to be required to demonstrate that the effects of the proposal can be managed satisfactorily. Construction activities may also require planning permission, and the views of the local planning authority should be obtained. 4.7 Effects on navigation Water levels may fluctuate as the turbine(s) are switched on or off. The local Navigation Authority must be consulted at the earliest stage. Formal permission for the works may be required where this has the potential to impact on navigation in the watercourse. Teddington Weir Hydropower Feasibility Study 12

13 5.0 Costs and Economics Investment and revenue streams are necessary for any financial analysis. The three main points that should be taken into account when doing the cost/benefit evaluation for the Archimedean Screw are the installation costs, the annual operational costs and the annual income from the electricity produced. The following section will look at what each of these involves. 5.1 Installation Costs The total investment required for the Archimedean Screw can be divided into two main cost components: The Electro-mechanical costs Civil Engineering, Grid Connection and Installation/Commissioning Costs The electro-mechanical costs consist of the main machine components of the scheme. Apart from the screw itself it should also include the trough, generator, gearbox, screen and inlet sluice gate. As for the civil engineering costs these should cover project management and site supervision through to materials (for screw supporting structure) and plant (shuttering, swing shovel etc). The electricity generated will be sold to an energy company under a power purchase agreement. These are negotiated on a case by case basis, therefore the costs below are indicative only. The connection will require a local transformer and 3 phase connection. The hydro installation is considered an embedded small generator and a G59 agreement with the distribution network operator EDF will be required for connection to the grid. A breakdown of all the major costs is shown on the Economic Analysis below (Table 1). Costs were obtained from Mann Power Consulting Ltd who are a UK supplier of the Archimedean Screw. 5.2 Income Electricity generated is sold to an energy company under a bespoke contract, however some typical values are as follows: Price paid for electricity produced and exported: 0.09 per kwh Renewable Obligation Certificate sales (ROC) 0.04 per kwh Climate Change Levy (CCL) Exemption Certificates: per kwh Note however that there is a strong possibility that a feed-in tariff will be introduced in This will see a higher price paid for all electricity generated and a simplified simpler of administration. Teddington Weir Hydropower Feasibility Study 13

14 The value of each kwh generated should be in the range of 0.25 to 0.30 which will affect the economic analysis greatly. Another point is that generated power could be sold to a local consumer such as Teddington Studios, which would attract a higher return. 5.4 Grant Funding There are funding schemes available, in particular the Low Carbon Buildings Programme (phase 2) can be of interest to not for profit organisations. There are also EU funds distributed by the regional development agencies, i.e. SEEDA in the case of Teddington. Thames Renewables has extensive experience of various funding bodies in both the private and public sectors. 5.5 Cost/Benefit Calculations The table below contains basic estimates based on the calculated flow, head and efficiency data. The overall efficiency of the screw has been estimated at 60% and it is possible that this figure is a conservative one. On a more cautionary note the proposed scheme at Romney Weir, Windsor has been abandoned twice by the developer npower due to excessive costs. The scheme is similar in size to option 2 below, i.e. two 4m diameter screws, costs seem to have been initially reported as being around one million pounds, however later reports talked of several millions. Our own estimate is around 1.2m however civil engineering costs are extremely difficult to quantify, and this is potentially the area of risk. The civil engineering costs should be firmed up as a priority. Teddington Weir Hydropower Feasibility Study 14

15 Economic analysis TEDDINGTON WEIR 1 ST JULY 2008 Option 1 Option 2 Option 3 Number of screws Max Flow m³/s Max Power KW Peak efficiency Design study fee 3,500 3,500 3,500 Detailed project plan fee 15,400 22,300 28,400 Liscence and planning application fees 1,500 1,500 1,500 Screen 5,000 10,000 15,000 Inlet sluice gate 15,000 30,000 45,000 Hydropower machine 120, , ,000 Generator 10,000 20,000 30,000 Control and grid connect system 20,000 40,000 60,000 Transportation 30,000 40,000 50,000 Craneage 20,000 30,000 40,000 Screw supporting structure 130, , ,000 Works to inlet and outlet channels 350, , ,000 Power house 15,000 30,000 45,000 Electric Connection 50,000 50,000 50,000 Project management/site supervision 39,270 56,865 72,420 Installation and commissioning 23,562 34,119 43,452 Total Installation 848,232 1,228,284 1,564,272 Cost per KW 5,655 4,094 3,476 Annual Costs: Operational costs Insurance 1,000 2,000 3,000 Rates 1,500 3,000 4,500 Meter reading Equipment maintenance 2,200 4,400 6,600 Total Annual Costs 5,700 10,400 15,100 Annual Income: Energy capture KWh 1,083,337 1,730,568 2,243,208 Carbon dioxide saved (tonnes) ,205 Capacity factor 82% 66% 57% Electric Sales to the grid 86, , ,457 Savings by using own electricity Renewable Obligation Certificate 43,333 69,223 89,728 Total revenue 130, , ,185 Total Annual Income 124, , ,085 Payback period (years) Return on Investment 25 year IRR 14% 16% 16% 25 year NPV Discount Rate 7% 600,314 1,070,598 1,396,728 Teddington Weir Hydropower Feasibility Study 15

16 6.0 Conclusion and Recommendations The initial feasibility illustrates a good potential for a hydro scheme at Teddington using an Archimedean screw. There appears to be ample data to support continuing the project to the next stage which will require formalising the project team and will involve initiating discussions with the various stakeholders. Fundraising will also be required as there will be consultant reports required to take the project through to the planning stage. Teddington Weir Hydropower Feasibility Study 16

17 Teddington Weir Hydropower Feasibility Study 17

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