RESEARCH & DEVELOPMENT REPORT NO. RD 2047

Transcription

1 RESEARCH & DEVELOPMENT REPORT NO. RD 2047 APPLICATION OF HYDROELECTRIC TECHNOLOGY IN STONECUTTERS ISLAND SEWAGE TREATMENT WORKS Research and Development Section Electrical & Mechanical Projects Division Drainage Services Department Jan 2008

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3 EXECUTIVE SUMMARY The objectives of this R&D Item No. RD Application of Hydroelectric Technology in Stonecutters Island Sewage Treatment Works (SCISTW) are to investigate the technical feasibility of constructing a pilot hydropower plant in one of the Vertical Outlet Wells in SCISTW and to estimate its cost effectiveness if installed. PolyU Technology & Consultancy Company Ltd. was commissioned in February 2007 to undertake an assignment under the Consultancy Agreement No. DEMP/06/19 for this R&D Item. Literature studies and market searches were conducted and relevant information of similar project was collected. It is recommended that a hydropower plant with a three-phase asynchronous generator and a basic propeller type turbine can be installed in the Vertical Outlet Well of SCISTW. By utilizing the net available pressure of the outflow effluent, the hydropower plant can generate electricity to supply some of the E&M equipment in SCISTW. Site measurements, including effluent outflow velocities, were made for estimation of the static and dynamic heads of the outflow effluent inside the Vertical Outlet Well. A hydropower plant of 45kW capacity is proposed to be installed in the Vertical Outlet Well of Sedimentation Tanks Nos. 40 & 42. The designed effluent flow rates of the hydropower plant are in the range of 1.1 to 1.25 m 3 /s while the designed available net head is from 4.5 to 5.5m. Possible options in installing the hydropower plant at the Vertical Outlet Well were investigated. Taking into account of technical aspects and site constraints, the configuration with the generator and turbine integrated into one unit and mounted inside the Vertical Outlet Well is recommended. A motorized control valve will be installed on top of the Vertical Outlet Well to control the effluent flow to the hydropower plant. The generated electricity will supply to an existing electrical switchboard in SCISTW, in parallel with the electricity supply of CLP, i.e. the hydropower plant to be grid-connected. The rated generation power of the proposed hydropower plant will only be about 45kW and is within the 200kW limit under the Technical Guidelines on Grid Connection of Small-scale Renewable Energy Power Systems issued by the Electrical & Mechanical Services Department (EMSD). CLP had been provided with relevant technical information of the hydropower plant and was i

4 basically satisfied. Nevertheless, CLP advised that the detailed design of the hydropower plant is still required to be submitted to him for formal approval and whether standby charge will be required for the proposed grid-connected hydropower plant can be evaluated after this hydropower plant project has been formally approved for implementation. It is expected that the proposed hydropower plant can provide a yield of about 263,000 kwh per year. The saving in electricity cost is estimated to be HK$201,185 per year based on that no standby charge will be required by CLP. The environmental benefit is 62.4 Metric Ton Carbon Equivalent per year or 229 Metric Ton CO 2 Equivalent per year. The estimated capital cost of installing the hydropower plant is about HK$5M. It gives a payback period of 26 years if only the financial aspect is to be considered. Although the financial benefit of this project may not be very attractive, it is considered worthwhile further exploring the application of hydroelectric technology at SCISTW in view of its environmental benefit in the reduction of greenhouse gas emission. If the pilot hydropower plant is decided to be installed, it will be able to be put into operation in end By then, more knowledge and experience in operating the hydropower plant could be obtained. It is also noted that the HATS Stage 2A project is undergoing, in which additional Sedimentation Tanks and their Vertical Outlet Wells will be built. If civil requirements of hydropower plant(s) are incorporated at the early stage of this project, the hydropower plant(s) can be designed with a lesser capital cost and better maintainability. Further study on the hydropower plants for the HATS Stage 2A project is recommended. ii

5 The Government of the Hong Kong Special Administrative Region Drainage Services Department Consultancy Agreement No. DEMP/06/19 Application of Hydroelectric Technology in SCISTW ( Final Report ) Submitted by PolyU Technology & Consultancy Co. Ltd.

6 TABLE OF CONTENTS Page No. 1 INTRODUCTION Background Scope of the Assignment Structure of the Report LITERATURE STUDIES ON HYDROELECTRIC TECHNOLOGY SUITABLE TYPES OF TURBINES AND GENERATORS Suitable Types of Turbines Suitable types of generators INFORMATION OF SIMILAR PROJECTS A 200 kw hydro plant in Puan Hydro, Korea A micro hydro scheme at a waste water treatment plant in Emmerich of Germany A small hydroelectric station for the new waste water treatment plant in Amann of Jodan A 1.35 MW hydro plant at The Point Loma Wastewater Treatment Plant TECHNICAL DETAILS AND BUDGETS OF SUITABLE TURBINES AND GENERATORS Tyco-Tamar Design in Australia Gugler Hydro Energy GmbH from Austria Kubota Corporation of Japan MEASUREMENT OF FLOW VELOCITY OF THE FINAL EFFLUENT IN THE VERTICAL WATER OUTFLOW WELL Equipment specification Results of measurements and estimations ESTIMATION OF STATIC AND DYNAMIC HEADS OF THE FINAL EFFLUENT IN THE VERTICAL WATER OUTLET WELL DESIGN REFERENCES Design Inputs Relevant Standards, Code of Practice and other Manuals/References PROPOSED HYDROELECTRIC TECHNOLOGY APPLICATION IN SCISTW POSSIBLE OPTIONS FOR THE PROPOSED HYDROELECTRIC SYSTEM General Turbine / Generator SET Control Valve/Gate LV Switchboard Cable & Conduit Routing

7 11 HYDRAULIC DESIGN Surge PRESURE and Back PRESSURE Conclusions CIVIL & MATERIAL REQUIREMENTS General Support for the Turbine and Genentor BoTtom metallic screen and its Support The guide tubes and its Support Support for the Electricity Cables/conduits ELECTRICAL & MECHANICAL WORKS Major Electrical Equipment Hydro-Turbine Generator LV Switchboard and control panel CLP S REQUIREMENTS FOR ON-GRID CONNECTION OPERATION AND CONTROL OF THE HYDROPOWER PLANT Normal Start-up Normal Shut-down Emergency Shut-down Failure of Power Supply Control and INstrumentation Maintenance issues SPECIFICATIONS OF THE PROPOSED HYDROELECTRIC SYSTEM PROJECT INTERFACE AND IMPLEMENTATION SCHEDULE Project Interface Implementation Schedule BUDGETING Capital Cost and Recurrent Cost ANNUAL ENERGY YIELD, FINANCIAL AND ENVIRONMENTAL BENEFITS Power & Energy Generation Power Utilization Environmental Benefits CONCLUSIONS & RECOMMENDATIONS General E & M EquipmeNt & Civil Work Construction Method Statement Project Interface and Implementation

8 1 Introduction 1.1 BACKGROUND The Stonecutter Island Sewage Treatment Work (SCISTW) is capable of handling a daily sewage flow of 1.7 million m 3 /d. After treatment, the effluent is discharged via a 1.7 km long submarine outfall to the western approach of the Victoria Harbour. There are 36 sedimentation tanks (excluding two prototype tanks) and 18 associated vertical outflow wells in SCISTW. The vertical drop distance of water inside the vertical outflow well can be as high as 5.5-8m. The velocity near the bottom of the well can be greater than 7 m/s. Due to the difference in the static water levels, there is a potential to recover pressure energy of the effluent water at the vertical outflow well of the treatment works to generate electricity by a water turbine generator. In February 2007, the Drainage Services Department (DSD) commissioned PolyU Technology & Consultancy Company Limited (PTeC) to undertake an assignment under the Consultancy Agreement No. DEMP/06/19 (hereinafter called The Assignment ), with the objective to investigate the technical feasibility and cost effectiveness for constructing a pilot hydropower plant for the generation of electrical energy to be used as part of the electricity supply to the SCISTW by utilizing the net available pressure of the outflow. 1.2 SCOPE OF THE ASSIGNMENT The scope of this Assignment comprises: - To carry out literature studies and market searches to collect the up-to-date information including the technical data and job references, of the hydroelectric technology, in particular the application of low head micro-hydroelectric technology in sewage treatment plants; To investigate the possibility of applying the hydroelectric technology in SCISTW from the engineering point of view, including the required civil modification works, liaison with CLP Power for connecting the hydroelectricity generation plant to his electricity supply grid, etc.; and To carry out a preliminary assessment on the cost-effectiveness of applying the hydroelectric technology in SCISTW 4

9 1.3 STRUCTURE OF THE REPORT Following the introductory section, the remainder of this Report is structured as follows:- Part A Literature Studies and Market Searches Section 2 Literature Studies on Hydroelectric Technology This will review the advantages and disadvantages of hydroelectricity, and their relevancy to this project. Section 3 Suitable Types of Turbines and Generators This section will discuss the type of turbine and generator suitable for the application of this project. Section 4 Information of Similar Projects A few examples of applications in water/sewage treatment plants will be given in this section Section 5 Technical Details of Suitable Turbines and Generators This section will present technical details of some suitable turbines and generator collected from suppliers. Part B Technical Feasibility of the Proposed Hydroelectric Technology Section 6 Measurement of Flow Rate of the Final Effluent in the Vertical Water Outlet Well This section will present the measurement results of the flow rate. Section 7 Measurement of Static and Dynamic Heads of the Final Effluent in the Vertical Water Outlet Well This section will present the measurement of static and dynamic head of the flow in the Vertical Water Outlet Well. Section 8 Design References This section will contain the design references for the pilot hydropower plant. Section 9 Proposed Hydroelectric Technology Application in SCISTW This section will highlight the description of the proposed hydro turbine system. Section 10 Possible Options for the Proposed Hydroelectric System This section will summarise the options recommended for the pilot hydropower plant. Section 11 Hydraulic Design This section will provide the hydraulic design for the pilot hydropower plant. Section 12 Civil Requirements This section will give the details of the general arrangement of the hydroelectric system as well as the associated civil and structural requirements. 5

10 Section 13 Electrical & Mechanical Works This section will present the electrical and mechanical works for the hydropower system. Section 14 CLP s Requirements for On-grid Connection This section will stipulate the CLP s requirements for the on-grid connection of the proposed hydroelectric system. Section 15 Operational and Control of the Proposed Hydroelectric System The operational requirements of the hydroelectric system will be discussed in this section. Section 16 Specifications of the Proposed Hydroelectric System The construction method statement of the hydroelectric system will be provided in this section. Section 17 Project Interface and Implementation Schedule This section will discuss the project interface and present a tentative implementation programme for the hydroelectric system. Part C Cost-Effectiveness of the Proposed Hydroelectric Technology Section 18 Budgeting This section will discuss the estimated costs of the whole project Section 19 Annual Energy Yield, Financial and Environmental Benefits This section will discuss the annual energy yield, financial and environmental benefits of the whole project Part D Conclusions and Recommendations Section 20 Conclusions and Recommendations This section will summarise the whole project. 6

11 Part A Literature Studies and Market Searches 2 Literature Studies on Hydroelectric Technology Within the various sewage treatment plants in DSD, there are various locations of vast water flow rate at low water head. DSD would like to explore the possibility of applying hydroelectric system at these locations to recover partly the energy in the water flow, without scarifying the performance of the sewage treatment plants. If the concept can be applied, then it will 1. help to boost the applications of renewable energy in Hong Kong; 2. help to reduce the emission of green house gases in Hong Kong; 3. reduce electricity bills of DSD; 4. also act as a response to government initiatives of green features in infrastructure projects. The following paragraphs are summary of literature studies on hydroelectric technology; a list of reference is attached at the end of this chapter. Hydro-electricity basically has following positive aspects: 1. Hydroelectric energy is a renewable energy source. 2. No carbon dioxide is emitted as a result of hydropower. 3. Hydroelectric energy is non-polluting. It does not cause chemical pollution of ground or water or the release of heat or noxious gases. 4. Hydroelectric energy has no fuel cost and has relatively low operating and maintenance costs, so it is a good investment in times of inflation and can provide very low cost electricity. 5. Hydroelectric stations have a long life. Many existing stations have been in operation for more than half a century and are still operating efficiently. 6. Hydropower station efficiencies of over 90% can be achieved, making it the most efficient of energy conversion technologies. 7. Hydroelectric energy technology is a proven technology that offers reliable and flexible operation. 8. Hydropower offers a means of responding within seconds to changes in load demand. 7

12 9. A dam can be a useful resource for leisure, fishing, irrigation or flood control. Point #6 may not apply in the sewage treatment plants of DSD. 90% efficiency can only be achieved in hydroelectric station of very large scale and high head. Point #8 does not apply in the proposal of this case. The output power will not be controlled but be simply fed into the grid. Obviously Point #9 does not apply in the sewage treatment plants of DSD. There are however some social, ecological and hydrological effects have to be taken into consideration when planning a hydroelectric power station. These effects can be enormous if the system is very large: 1. Hydropower is only suitable for sites with large volumes of flowing water. Decreased rainfall, due to climate change, would reduce the electricity available. 2. Considerable capital investment is required, especially for large schemes. 3. Dams cause large areas upstream to be flooded. This may cause displacement of people and will destroy animal habitat and flora. 4. Flooded vegetation will rot anaerobically and emit methane, a potent greenhouse gas. 5. The dams and diversion of water may also change the groundwater flows in the local area and this can change the ecology of the area. 6. Damming the river reduces flooding which reduces the amount of silt carried downstream. It also increases the amount deposited in the dam. This may mean that the dam has to eventually be dredged while downstream there is reduced fertility in the soil. The flow rates (as detailed later) in the sewage treatment plants of DSD are large and relatively fairly constant (as against rainfall throughout a year). Hence Point #1 is not applicable. No additional dam or reservoir is required to be constructed to hold the water. Hence the Point 3 to 6 are not applicable. Fortunately, most of the demerits mentioned here are not valid in the sewage treatment plants of DSD, maybe with only Point #2 as the exception. However, in the proposed pilot project, only one pilot hydro generator plant will be installed in one of the 18 vertical outflow wells at SCISTW. Hence the capital investment will not be too large. However, there is one specific point which need to be considered seriously in application of hydro plant in sewage treatment works as compared to other areas of applications. That is sewage water to be highly corrosive and hence all the involved equipment have to have enough protection against it. This point will add considerable amount to the capital cost of the equipment and support structure of the equipment. Therefore, overall speaking, application of hydroelectricity technology to recover energy from sewage water in general has more merits than demerits. 8

13 Reference: Adam Harvey, Micro-hydro Design Manual, Intermediate Technology Publications Jiandong Tong, Mini Hydropower, John Wiley & Sons, FM Griffin, Feasibility of Energy Recovery from a Wastewater Treatment Scheme, Proceedings of Hydropower Developments Conference, IMechE, Edward, B.K., The economics of hydroelectric power, Cheltenham, UK ; Northampton, MA : Edward Elgar, 2003 Grigsby, L.L., The electric power engineering handbook, Boca Raton, Fla.: CRC Press,

14 3 Suitable Types of Turbines and Generators Turbine and generator are the two most important components in a hydroelectric project. This Section will discuss the suitable types of turbines and generators to be used in the pilot project. 3.1 SUITABLE TYPES OF TURBINES Turbines can be classified as high head (more than 100 m), medium head (20 to 100 m) or low head (less than 20 m) machines. Turbines are also be classified by their principle of operation and can be either impulse turbines or reaction turbines. Table 3.1: Selection of turbine types based on available water head high head medium head low head Impulse turbines Pelton Turgo cross-flow multi-jet Pelton cross-flow Turgo Reaction turbines Francis propeller Kaplan Turbine selection is based mostly on the available water head, and less so on the available flow rate. In general, impulse turbines are used for high head sites, and reaction turbines are used for low head sites. In most sewage treatment plants of DSD, low head should be the usual cases. Hence, only reaction turbines are discussed here. The reaction turbines considered here are the Francis turbine and the propeller turbine. A special case of the propeller turbine is the Kaplan. In all these cases, specific speed is high, i.e. reaction turbines rotate faster than impulse turbines given the same head and flow conditions. Therefore a reaction turbine can often be coupled directly to a generator without requiring a speed-changing mechanism. Some manufacturers even make integrated turbinegenerator sets of this type. Significant cost savings are made in eliminating the speed changing mechanism and the maintenance of the integrated hydro unit is very much simpler. Actually, the Francis turbine is more suitable for medium heads than low heads, while the propeller is more suitable for low heads. 10

15 Figure 3.1 Selection of turbine based on available water head and power output (Source: Francis turbines can either be volute-cased or open-flume machines. The spiral casing is tapered to distribute water uniformly around the entire perimeter of the runner and the guide vanes feed the water into the runner at the correct angle. The runner blades are profiled in a complex manner and direct the water so that it exits axially from the centre of the runner. In doing so, the water imparts most of its pressure energy to the runner before leaving the turbine via a draft tube. Figure 3.2: Francis turbine (source: adapted from & 11

16 The Francis turbine is generally fitted with adjustable guide vanes. These regulate the water flow as it enters the runner and are usually linked to a governing system which matches flow to turbine loading in the same way as a spear valve or deflector plate in a Pelton turbine. When the flow is reduced the efficiency of the turbine falls away. The basic propeller turbine consists of a propeller, similar to a ship's propeller, fitted inside a continuation of the penstock tube. The propeller usually has three to six blades, three in the case of very low head (just a few meters) units and the water flow is regulated by static blades or gates just upstream of the propeller. This kind of propeller turbine is known as a fixed blade axial flow turbine because the pitch angle of the rotor blades cannot be changed. The part-flow efficiency of fixed-blade propeller turbines tends to be very poor. Figure 3.3: Axial flow propeller turbine For the intended location on the application in SCISTW, the head is low (less than 10 m) and there are more physical constraints in installing Francis turbine, an axial flow propeller turbine is more suitable for installation, such that the propeller is installed with its axis is vertical. Kaplan turbines, is a special type of propeller trubine, in which the pitch of the blades and the guide vanes can be adjusted. They are well-adapted to wide ranges of flow or head conditions, since their peak efficiency can be achieved over a wide range of flow conditions by controlling the gates openings and the pitch angles of the blades. Semi Kaplan turbines are the same as Kaplan turbines, but now the guide vanes are fixed, only the pitch of blades can be changed. Figure 3.4: Kaplan turbine 12

17 Figure 3.5 A drawing showing arrangement for a vertical axis Saxo axial flow Kaplan turbine (Source Bofors-Nohab brochure Small scale hydro turbine program 5702) Anyway, the flow rate at the intended location is relatively constant, hence basic propeller type turbine, not Kaplan type, is more preferable to increase the robustness of the trubine (need no blade angle changing mechanism) and to reduce the complication in control. However, Kaplan type turbine can also be considered. 3.2 SUITABLE TYPES OF GENERATORS For the power range of tens of kilowatt grid-connected renewable energy systems, the commonly used generators are: o Three-phase synchronous generator and o Three-phase asynchronous generator (also commonly referred as three-phase induction generator). In theory, any DC generators can also be used and then DC can be converted to three-phase AC via a three-phase grid-connected inverter. However this configuration is not recommended for the proposed system, due to the overall efficiency is low for this configuration in the proposed power range and the complications in the maintenance of the generator and the system. 13

18 Induction generators are generally more appropriate for relatively smaller systems (in tens/hundreds kilowatt, not megawatt scale). They have the advantage of being rugged, almost maintenance-free and cheaper than synchronous generators (around 10% to 25% lower in price for the range of tens of kilowatt). In fact, the choice on synchronous generators is quite limited for power range of tens of kilowatt. The induction generator is, in fact, a standard three-phase induction motor, wired to operate as a generator. Hence the choice of induction generators at tens of kilowatt power range is many. Induction generators can also allow for a wider variation of shaft speed (hence the water flow rate). Synchronous generators are generally appropriate for multi megawatt systems. They have the advantage of slightly higher efficiency and the excitation is directly controllable. Hence the excitation can be controlled for maintaining the stability, VAR compensation and voltage regulation of the power grid. In the proposed hydro plant, it is recommended to use induction generator. The reasons are: o The water flow rate in the proposed hydro plant is likely to have some variations (although small) due to the variation of amount of the incoming sewage water. Induction generator is more capable in coping with these variations. o In the proposed system, the expected range of power is tens kilowatt. It has little impact of the stability of the very large power grid of CLP Power. It is not required to control the excitation of the generator of this hydro plant to help to stabilize the power grid. o The efficiency of induction generator at tens/hundreds kilowatt range is well over 90% and it is only slightly (1 to 2 %) less than that of synchronous generator. o The capital cost of induction generator of this power range should be 10% to 25% lower than that of synchronous generator. o o The only regular maintenance required for induction generations of this power range is the regular lubrication of the shaft bearings and the replacement of shaft bearing after long years of services. While these maintenance items are also required by synchronous generators, synchronous generators need regular replacements of carbon brushes and polishing of slip rings. Hence the maintenance cost of an induction generator of this power range should be only 40% to 70% that of a synchronous generator. The advantage of using synchronous generator as VAR compensator is not an important point in this case. 14

19 4 Information of Similar Projects This Section gives a few examples of applications of hydroelectricity in water/sewage treatment plant in the world. One of it is as small as only 13 kw, while there is also an example of 1.35 MW rated output from the generator. This illustrated that the applications are in general feasible. 4.1 A 200 KW HYDRO PLANT IN PUAN HYDRO, KOREA The turbine generator unit is located in an underground powerhouse which delivers water to a water treatment plant, as well as providing electrical power to the facility. Turbine: 500mm Propeller type Generator: rated power RPM Rated head: 19.6 m Rated flow: 1.18 m 3 /sec The 500 mm Propeller turbine Water treatment facility Dam feeding the facility 500 mm runner Figure 4.1: Photos of the hydro plant in Puan Hydro, Korea (Source : 15

20 4.2 A MICRO HYDRO SCHEME AT A WASTE WATER TREATMENT PLANT IN EMMERICH OF GERMANY This is a very small hydro plant at a waste water treatment installation. Technical Data: o o o o o Average output power: 13 kw Water head: H=3.6 to 3.8 m Water flow rate: Q = 400 l/s Generator type: Asynchrongenerator 15 kw, 400V/50Hz Expected annual yield: 65,000 kwh Figure 4.2: Photos of the hydro plant at Emmerich of Germany (Source: 16

21 4.3 A SMALL HYDROELECTRIC STATION FOR THE NEW WASTE WATER TREATMENT PLANT IN AMANN OF JODAN The town of Amann of Jodan has decided to equip itself with a new wastewater treatment plant. In this region, the purification of water is of vital interest and the volume of water to be treated is high: 277,000 m 3 /day. The engineers who designed the installation, which was commissioned in 2005, found a way to reduce the operating costs of this type of installation. Yearly production has been targeted at 21,900,000 kwh in the long run by turbining of waste water upstream and downstream from the station. The company that is going to build and operate the new sewage treatment plant in Jordan, entrusted the turbining design to a minihydraulics laboratory in Switzerland. This laboratory decided to use the height difference between the town of Amann (site of the pre-treatment plant) and the sewage treatment plant in As Samra (103.5 m), in order to produce electricity between the outlet of the treatment plant and the run-off into the Oued Duleil (47.8 m). The company also claimed that there is great potential for electricity production in a treatment plant, and most sites do not use this potential. Indeed, the digestion gas (biogas) that is produced can be transformed into electricity thanks to a TOTEM (Total Energy Module) and surplus hydraulic pressure can be turbined. When the conditions to use these two potentials are combined, a sewage treatment plant can produce more electricity than it consumes. The engineers of the company realized that the height difference and flow were financially interesting at the Amann site. They decided to recover the surplus pressure at the entrance to or at the outlet of the sewage treatment plant by replacing the dissipating valves with turbo generators thus allowing for the production of electricity. They distinguish between two types of energy recovery. In the first type, raw sewage is turbined at the outlet of the sewage pipes that transport the waste water from the town upstream from the treatment plant. In the second type, treated water from the treatment plant is turbined at the outlet of a pipe or at a stream or river, like in a conventional hydro-electric installation. The town of Amann will make significant energy savings using the principle which was decided upon. Indeed, sewage treatment plants use a great amount of energy. The driving force needed for the sifters, mixers, pumps, fans, etc. consume great quantities of electricity. 17

22 4.4 A 1.35 MW HYDRO PLANT AT THE POINT LOMA WASTEWATER TREATMENT PLANT The Point Loma Wastewater Treatment Plant of San Diego (California, USA) is located on a bluff above the Pacific Ocean. Treated wastewater ( effluent ) is discharged into the ocean through a 7.2 km ocean outfall after a 27-m drop from the plant to the outfall. A 1,350 kilowatt hydroelectric plant captures the energy of the effluent as it flows down the outfall connection. The power plant, partially funded by a grant from the California Energy Commission, produces up to 1.35 megawatts for sale to the electric grid, enough power to supply energy to 10,000 homes. Opened in 1963, the Point Loma Wastewater Treatment Plant treats approximately 662,000 m 3 /day of wastewater generated in a 1,165-km 2 area by more than 2.2 million residents in 12 municipalities. Located on a 16-ha site on the Point Loma bluffs in San Diego, the advanced primary treatment plant has a capacity of 908,400 m 3 /day. Figure 4.3: The 1.35 MW generator of the hydroelectric project being installed in the Point Loma Wastewater Treatment Plant (source: Wastewater Department, City of San Diego Metropolitan). 18

23 5 Technical Details and Budgets of Suitable Turbines and Generators The following turbine and generator suppliers have been approached and those gave responses are:- (i) Tyco-Tamar Design of Australia (ii) Gugler Hydro Energy GmbH of Austria (iii) Kubota Corporation of Japan Data were collected from these of turbine and generator suppliers. This section will present those in the relevant rating range to the proposed project. 5.1 TYCO-TAMAR DESIGN IN AUSTRALIA Tyco-Tamar Design in Tasmania of Australia can supply series of micro to small trubine/generator set with power output from the generator varies from less than a kw to hundreds of watt. Those suitable ones (both in available water head and the rated power, hence the estimated flow rate) off the shelf are high-lighted in red in the table. Table 5.1: Models of micro to mini turbine generator sets from Tyco-Tarmar Design Co. Ltd. Turbine Type Code Head range (m) Electrical Range (kw). Pelton LCP1 16 to to 3 Turgo Impulse LCT1 6 to to 3 Pelton AP2 28 to to 9.1 " " AP3 34 to to 15 Turgo Impulse AT1 20 to to 7 " " AT2 10 to to 15 " " AT3 6 to to 15 " " AT3 twin 4 to to 15 Pelton SP3 60 to to 24 " " SP3 twin 60 to to 38 Turgo Impulse ST3 55 to to 34 " " ST3 twin 45 to to 34 " " ST4 25 to to 77 " " ST4 twin 25 to to 90 Pelton SP4 80 to to 60 " " SP4 twin 80 to to 63 Turgo Impulse ST5 30 to to 140 " " ST5 twin 30 to to 230 Pelton SP5 120 to to

24 Turgo Impulse ST6 30 to to 440 " " ST6 twin 30 to to 640 Pelton SP6 190 to to 330 " " SP6 twin 190 to to

25 Turbine Type Code Head range (m) Electrical Range (kw). Francis F6 2 to to 8.5 " " F9 2 to to 45 " " F10 2 to to 70 " " F12 2 to to 104 " " F14 2 to to 153 " " F16 2 to to 220 " " F18 2 to to 300 Turbine Type Code Head Range (m) Electrical Range (kw) Semi Kaplan FS to to 3.5 " " FS to to 15.4 " " FS to to 23 " " FS to to 33 " " FS to to 50 " " FS to to 75 " " FS to to 113 " " FS to to 171 Figure5.1: An example of a 110 kw Semi-Kaplan turbine, Model FS2-365, (with hydraulically operated turbine blades) at assembly stage (Source: Tyco-Tarmar Design Co. Ltd.) 21

26 Figure 5.2: Left: Hydralical power pack with PLC for the controlling the main inlet valve and the blades of the semi-kaplan trubine to maintain optimum efficiency. Right: The main electrical cabinet which contains the electrical switch gear, gnerator protection, local power distribution circuit breakers, a PLC, and other asscoiated control and electrical equipment. (Source: Tyco-Tarmar Design Co. Ltd.) As mentioned in previous section, Francis type trubine is not recommended due to the head and the physical constainted in the site, only Kaplan or semi-kaplan trubine from this company will be considered. Then, it seems that the most appropirate one is model FS2-245 semi-kaplan turbine/generator set: the head can range from 1 to 20m, while the output power ranges from 5. 7 to 50 kw. The company claims that units can be designed and manufactured to suit the particular site to gain maximum efficiency. 22

27 5.2 GUGLER HYDRO ENERGY GMBH FROM AUSTRIA Gugler Hydro Energy GmbH is a company of 80-year old and she specializes in small trubine. She claimes that she is worldwide successful as complete provider of small hydropower plants with its innovative products. Gugler Hydro Energy GmbH offers a three-blade Kaplan turbine (model: Gugler KT 50) of turbine diameter of 0.5m, it has mannual adjustable runner blades, fixed wicket gates, the other technical details are: Net head range (H n ): 1-6 m Discharges rate range (Q A ): 300-1,500 litre/sec Rated trubine output (P T ): kw Rated generator output (P G ): 1.8 to 50 kw Turbine speeds (n 1 ): 350-1,000 rpm Runaway speeds (n d ): 1,200-3,200 rpm Generator speed (n 2 at 50 Hz/60 Hz): rpm Limits and parameters: 23

28 Operation curves of the KT-50 turbine/generator set is shown in the following figure. Figure 5.3: Operation curves of the KT-50 turbine/generator set of Gugler Hydro Energy GmbH Figure 5.4: the KT-50 turbine/generator set of Gugler Hydro Energy GmbH 24

29 Another suitable candidate for the proposed project from Gugler Hydro Energy GmbH is its KT-35 model. Its technical details are: A three blade Kaplan runner Runner diameter 355 mm Manual adjustable runner blades Fixed wicket gates; Net head range (H n ): 1-6 m Discharges rate range (Q A ): litre/sec Rated trubine output (P T ): kw Rated generator output (P G ): 1.8 to 35 kw Turbine speeds (n 1 ): 350-1,000 rpm Runaway speeds (n d ): 1,200-3,200 rpm Generator speed (n 2 at 50 Hz/60 Hz): rpm Limits and parameters: 25

30 Figure 5.5: Operation curves of the KT-35 turbine/generator set of Gugler Hydro Energy GmbH 26

31 5.3 KUBOTA CORPORATION OF JAPAN Kubota Corporation established in 1890 and now is a stock-listed company at Tokyo, Osaka, New York and Frankfurt. It has about 24,000 employees and a net sales amount of US$600 million/year. Kubota can supply a turbine/generator set of 45 kw rated power output suitable for this project. The technical details the turbine generator set are: 27

32 Figure 5.6: Operation curves of the 45 kw Turbine gnerator set from Kubota Corporation (Note: the term reverse running pump turbine is used here in the manufacturer s data sheet, however it should be the same as the basic propeller type ). 28

33 Part B Technical Feasibility of the Proposed Hydroelectric Technology 6 Measurement of Flow Velocity of the Final Effluent in the Vertical Water Outflow Well The water flow rates at three different points inside one of those deep vertical outflow wells were measured through tailor-made supporting rigs and a test instrument procured specifically for this project. The measurement was conducted on 23 rd July 2007, from 9:00 am to 5:30 pm. 6.1 EQUIPMENT SPECIFICATION Test device - Safety factor = Anticorrosive materials Flow meter - Range of measurable flow velocity ~ 0 to 9.8 ms -1 - Real-time monitoring - Anticorrosive materials Figure 6.1: The flow meter sensor used in the measurements 29

34 6.2 RESULTS OF MEASUREMENTS AND ESTIMATIONS Measurement Position 1 Depth = 4480 (mm) Effective Depth = 1800 (mm) Time interval = 60 (s) Number of turns - Sample 1 = 879 (Turns), 4.76 ms -1 - Sample 2 = 877 (Turns), 4.75 ms -1 - Sample 3 = 862 (Turns), 4.66 ms -1 Average measured flow 4.72 ms -1 velocity = Theoretical maximum flow 5.94 ms -1 velocity at that point Measured/Theoretical= 79% Measurement Position 2 Depth = 5980 (mm) Effective Depth 3300 (mm) Time interval = 60 (s) Number of turns - Sample 1 = 1113 (Turns), 6.06 ms -1 - Sample 2 = 1108 (Turns), 6.03 ms -1 - Sample 3 = 1115 (Turns), 6.07 ms -1 Average measured flow 6.05 ms -1 velocity = Theoretical maximum 8.05 ms -1 flow velocity at that point = Measured/Theoretical= 75% Position 3 (the estimated position of the turbine) Depth = Effective Depth (the depth is too deep to be measured by the instrument) Theoretical maximum flow velocity at that point = Estimated flow velocity, based on Measured/Theoretical=~75 %, as obtained in above 2 measurements 7480 (mm) 4800 (mm) 9.7 ms ms -1 30

35 Remarks: 1. The conversion from the number of turns to flow rate (in ms -1 ) is based on the conversion information provided from the manufacturer of the flow rate sensor. 2. The theoretical maximum flow velocity is calculated from equation of basic free fall in vacuum. Hence there is expected difference between theoretical maximum flow velocity and the actual velocity due to fluid viscosity and air pressure. 3. The reason for measurements cannot be taken for position 3 is the limitation of the length measurement rod, otherwise the mechanical strength of the whole set up will be too weak. Figure 6.2: Measurement configuration 31

36 7 Estimation of Static and Dynamic Heads of the Final Effluent in the Vertical Water Outlet Well Based on the results of the above section, the velocity of the flow at the position of the turbine is about 7.2 ms -1. Hence the dynamic head at the location = v 2 /(2g) = 2.64 m While the static head is estimated to be 4.8 m. Hence the total head in the worst case is 7.44m. Note this is the worse case, as (i) the installation of the guide tube and turbine in the well will reduce the flow velocity, (ii) the velocity of the flow used here is the velocity at the centre of the flow which is the highest, (iii) it may not be a full-bore condition at the top part of the well (the effective head is likely to be 4.5 m). 32

37 8 Design references 8.1 DESIGN INPUTS In this Report, design inputs for the hydropower plant shall include taking references to all statutory requirements, design standards, codes and guidelines, at both local and international dimensions. 8.2 RELEVANT STANDARDS, CODE OF PRACTICE AND OTHER MANUALS/REFERENCES The proposed works shall be designed based on the relevant codes and standards that meet the Drainage Services Department, other local government department, and utility companies requirements as well as to follow the good engineering practice on similar works. The following codes of practice, standards and other manuals/references with the associated amendments and additions shall be adopted for the design of the Project: Table 8-1 Relevant Design Standards, Code of Practice and other Manuals/References For Civil, Structural and Geotechnical Works: 1 General Specification for Civil Engineering Works, Volumes 1, 2 and 3, Civil Engineering Department 2 Stormwater Drainage Manual, DSD 3 Building Department Practice Note for Authorized Persons & Registered Structural Engineers No. 141 Foundation Design 4 BS 8007 Code of Practice for Design of Concrete Structure for Retaining Aqueous Liquids 5 BS 8110 Structural Use of Concrete 6 BS 4482 Specification for cold reduced steel wire for the reinforcement of concrete 7 BS 4483 Steel fabric for the reinforcement of concrete 8 BS EN Drains and Sewer Systems Outside Buildings Performance Requirements 9 BS EN Drains and Sewer Systems Outside Buildings Planning 10 BS EN Drains and Sewer Systems Outside Buildings Hydraulic Design and Environmental Considerations 11 BS EN 295 Vitrified Clay Pipes and Fittings and Pipe Joints for Drains and Sewers 12 BS Steel, Concrete and Composite Bridges. General Statement 13 BS Steel, Concrete and Composite Bridges. Specification for Loads 14 BS Steel, Concrete and Composite Bridges. Code of Practice for Design of Concrete Bridges 15 BS 8010 Code of Practice for Pipelines 16 BS 4449 Specification for Carbon Steel Bars for the Reinforcement of Concrete 17 BS 4027 Specification for Sulfate-Resisting Portland Cement 18 BS 4248 Specification for Supersulphated Cement 19 BS 8004 Code of Practice for Foundations 33

38 20 BS 534 Specification for Steel Pipes, Joints and Specials for Water and Sewage 21 BS Specification for Wrought Steels for Mechanical and Allied Engineering Purposes. General Inspection and Testing Procedures and Specific Requirements for Carbon, Carbon Manganese, Alloy and Stainless Steels 22 BS Circular Flanges for Pipes, Valves and Fittings (PN designated). Specification for Copper Alloy and Composite flanges 23 CIRIA report No. 78 Mechanical and Electrical Works: 24 Standard Specifications of the Water Supplies Department 25 General Requirements for Electronic Contracts, Specification No. ESG01, Electronics Division, Electrical & Mechanical Services Department, EMSD 26 Supply rules and other requirements of the CLP Power Hong Kong Limited. 27 Renewable Energy Systems and CLP s Electricity Grid, CLPP 28 Code of Practice for the Electricity (Wirings) Regulations, EMSD 29 General Specification for Electrical Installation in Government Buildings of the HKSAR, Architectural Services Department, ASD 30 Regulations for Electrical Installations, Institution of Electrical Engineers, UK 31 Technical Guidelines on Grid Connection of Small-scale Renewable Energy Power Systems, 2005, EMSD 32 IEEE Standard 1547 for Interconnecting Distributed Resources with Electric Power Systems 33 UL 1741, Inverters, Converters, Controllers and Interconnection System Equipment for Use with Distributed Energy Resources 34 EA G59/1, Recommendations for the Connection of Embedded Generating Plant to the Public Electricity Suppliers Distribution Systems 35 Code of Practice for Energy Efficiency of Electrical Installation, EMSD 36 Guidelines on Energy Efficiency of Electrical Installation, EMSD 37 Addenda to Guidelines on Energy Efficiency of Electrical Installations, EMSD For Design of Building Services: Electrical Installation 38 Electrical Ordinance 39 IEE/IET Regulation 40 Codes of Practice for Electricity (Wiring) Regulation, EMSD 41 General Specification for Electrical Installation in Government buildings 42 BS 6651 Code of Practice for Protection of Structures Against lighting 43 CIBSE Code 44 Code of Practice for Energy Efficiency of Lighting Installation, EMSD 45 Guidelines on Energy Efficiency of Lighting Installations, EMSD 46 Addendum No. 1 to Guidelines on Energy Efficiency of Lighting Installations, EMSD Fire Services Installation 47 Codes of Practice for Minimum Fire Service Installations and Equipment, Fire Services Department (FSD) 48 FSD Circular Letters 34

39 49 L.P.C. Rules 50 Requirement of Water Authority 51 BS 5839 Automatic Fire Detection and Alarm System 52 Fire Offices Committee Rules 53 General Specification for Fire Service Installation in Government Buildings, Hong Kong MVAC Installation 54 The requirement of the Hong Kong Fire Services Department including Codes of Practice for Minimum Fire Service Installations and Equipment, and Inspection and Testing of Installations and Equipment issued by the FSD, together with FSD circulars/letters/amendments. 55 Building Ordinance and the affiliated regulations 56 General Specification for Air-conditioning and Refrigeration, Ventilation and Control Monitoring and Control System Installations in Government Buildings 57 CIBSE Guide 35

40 9 Proposed Hydroelectric Technology Application in SCISTW The proposed pilot hydropower plant incorporates a turbine to convert energy in the form of falling effluent water in the vertical outflow well of the sedimentation tanks of SCISTW into rotating shaft power. The static pressure head between the water level of the tank and the water level of the horizontal trench at the bottom ranges from about 4.5 to 6 metres depending on the operating conditions and the exact location of the turbine. The shaft power is then converted to electricity by a generator coupled to the turbine. The output voltage is expected to be 380 V three-phase AC and then connected to a switchboard and control panel. The hydro-turbine is designed to work under maximum 6 m static head under operating conditions. The effective static head is about 4.5m while the efficient operating flow rate is from about 1.1 to 1.25 m 3 /s. The maximum power output from the generator shall be approximately 45kW to 50kW. Besides, the hydro-turbine shall be designed to cater for the start up under hydro-static /surge conditions that may be as high as 17 metres total head equivalent. This head will be diminished as the turbine flow increases to the normal operating range as specified. As mentioned above, the estimated maximum power output of the system is about 45kW to 50 kw, and this is basically the maximum allowable output from a turbine with the given possible water head, typical machine efficiency and physical internal dimension constraints of the well. The dimension constraints limited the external size of the whole setup to be within 1.2 m in diameter. Then with reasonable allowance for fixture mounting, the effective diameter of the turbine can only be about 1 m in diameter. After experience gained in this pilot project, this maximum power output for subsequence installation may be increased slightly by increasing the effective diameter of the turbine without affecting the overall external diameter. Power generated by the hydro-turbine generator will be utilized at the SCISTW to provide co-generated power with the utility to the all electrical installation within SCISTW. All power generated by the hydro-turbine driven generator shall be utilized on site as a reduction in the amount of power received from the utility. There will be no export (to outside of SCISTW) of the power by the turbine generator. The hydro-turbine generator unit shall always operate in conjunction with the utility supply, and shall not operate independently without the utility. 36

41 Effluent Outflow Water Turbine Generator LV Switchboard Local LV Distribution Board Figure 9.1 Schematic of power flow of the hydro plant 37

42 10 Possible Options for the Proposed Hydroelectric System 10.1 GENERAL Major equipment/facilities to be incorporated in the hydropower plant include turbine, generator, control valve/gate, LV switchboards and control panel. The turbine and the generator will be installed in a vertical outflow well. The control valves/gates will be installed at the top of the well. The LV switchboard and control panel will be installed inside an existing switchboard room near the vertical outflow well. Additional small cable conduits will also be required to be installed between the generator and the LV switchboards/control panel TURBINE / GENERATOR SET The turbine has to be mounted vertically inside the vertical outflow well in order for the turbine to capture the water flow with minimum civil modification works. Of course, another alternative is to re-route that part of effluent water to a separate structure (next to the vertical outflow well) which houses the turbine in whatever orientation. However, this alternative is not recommended in this report due to the complicated civil modification works involved. The selected vertical outflow well for this pilot project is #40-#42 (i.e the well between tank #40 and tank #42). The reason of the selection is: This well is near the upstream end of the effluent water flow (in fact the 2 nd first well along the flow path) under all these wells. In case, there are needs to stop the flow of effluent water under this well during turbine installation period, the operations of other wells are minimally affected. Although this well is not the first well in the flow (well #44-#46 is the first one), it very often operates together with the well #44-#46. Therefore there will be no effluent water flow from well #44-#46 to well #40-#42. The reason of not selecting the first well #44-#46 is that there is an existing odour eliminator at the top of the well. If the odour eliminator can be removed, it is better to install the hydroelectric system to the first well #44-#46. 38

43 Figure 10.1: Diagram and photo shows the location of Tank #40 and Tank #42 which will be used in the pilot hydro project. 39