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Power - Hydro turbine - 6,500 kW / China
Case study assignment
A Chinese electric utility has hired you to prepare a pre-feasibility study for implementing a small hydro project in the Hunan Province of China. Based on the utility's load projections, 4 MW of firm capacity will be required in the near future to supply base load power to the local electricity grid. In order to insure reliability, it is utility policy to install a second identical back-up turbine and generator.
Site information
The proposed project is located in the Ruchen County in the Hunan Province of China on the Jiujiedai River. The site location is easily accessible by road.
Based on the results of a preliminary site investigation, a project developing 150-m gross head would be technically feasible. A suitable site exists for the construction of a concrete dam with a crest length of 70 m that would provide some seasonal water storage without extensive upstream flooding. This is considered a "run-of-river" project. The site is located downstream of an existing hydroelectric project with additional storage capacity. A preliminary assessment has indicated that the combined available storage will be approximately 15.5 million m³. The following flow-duration curve for the natural flow at the site (i.e., before effects of storage) is available from previous studies.
Case study assignment
A Chinese electric utility has hired you to prepare a pre-feasibility study for implementing a small hydro project in the Hunan Province of China. Based on the utility's load projections, 4 MW of firm capacity will be required in the near future to supply base load power to the local electricity grid. In order to insure reliability, it is utility policy to install a second identical back-up turbine and generator.
Site information
The proposed project is located in the Ruchen County in the Hunan Province of China on the Jiujiedai River. The site location is easily accessible by road.
Based on the results of a preliminary site investigation, a project developing 150-m gross head would be technically feasible. A suitable site exists for the construction of a concrete dam with a crest length of 70 m that would provide some seasonal water storage without extensive upstream flooding. This is considered a "run-of-river" project. The site is located downstream of an existing hydroelectric project with additional storage capacity. A preliminary assessment has indicated that the combined available storage will be approximately 15.5 million m³. The following flow-duration curve for the natural flow at the site (i.e., before effects of storage) is available from previous studies.
An environmental analysis has concluded that natural inflow to the river downstream of the proposed dam would be sufficient to allow diversion of all but 0.1 m³/s of the available flow during low-flow periods.
The topography between the dam and proposed powerhouse location is steep and unsuitable for aboveground water conveyance structures. As such, a 3.4-km tunnel will be required, which can be hand-built using local, experienced labour. Based on a preliminary geological assessment it is anticipated that the rock will be ideal for tunnel construction and that only 20% of the tunnel will have to be lined. Approximately 45 km of temporary access road will be required for the construction of the tunnel to allow the removal of excavated material.
The powerhouse can be located on a stretch of the river where the river level will rise a maximum of 2 m during high flows. A 50-m long tailrace canal will have to be excavated in rock that has a side slope of approximately 30 degrees. A 485-m penstock will also be required. In order to connect the project with the central-grid, approximately 6 km of 110 kV transmission line will have to be constructed through relatively flat, open terrain.
For the greenhouse gas analysis, assume that natural gas is the fuel that will be displaced.
Financial information
The utility considering the project will invest in a detailed evaluation of the project if the pre-feasibility study indicates a positive net present value given a discount rate of 9%. The utility will consider financing 75% of the project costs at 9% over a period of 15 years.
The current electricity tariff is yuan 0.40/kWh (US$0.048/kWh), which is expected to increase 5% annually. General inflation is anticipated to be 2% over the 25-year evaluation term.
All amounts are to be expressed in US dollars. An exchange rate of 0.63 US$/CDN$ can be assumed. Costs in China relative to Canada can be assumed to be 80% for construction equipment, 50% for labour and 85% for equipment manufacture. Fuel costs in China can be assumed to be approximately equal to fuel costs in Canada.
Annual operation & maintenance (O&M) costs would include property taxes (0.2% of total project cost) insurance (0.5% of total project cost), transmission line maintenance (5% of transmission line and substation cost), spare parts (0.25% of total project cost) and labour cost of US$80,000. An additional 10% (of the annual operation and maintenance budget) should be allowed for administration and 10% for contingencies. It is anticipated that approximately US$100,000 will be required every 10 years for major maintenance.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from the analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
The topography between the dam and proposed powerhouse location is steep and unsuitable for aboveground water conveyance structures. As such, a 3.4-km tunnel will be required, which can be hand-built using local, experienced labour. Based on a preliminary geological assessment it is anticipated that the rock will be ideal for tunnel construction and that only 20% of the tunnel will have to be lined. Approximately 45 km of temporary access road will be required for the construction of the tunnel to allow the removal of excavated material.
The powerhouse can be located on a stretch of the river where the river level will rise a maximum of 2 m during high flows. A 50-m long tailrace canal will have to be excavated in rock that has a side slope of approximately 30 degrees. A 485-m penstock will also be required. In order to connect the project with the central-grid, approximately 6 km of 110 kV transmission line will have to be constructed through relatively flat, open terrain.
For the greenhouse gas analysis, assume that natural gas is the fuel that will be displaced.
Financial information
The utility considering the project will invest in a detailed evaluation of the project if the pre-feasibility study indicates a positive net present value given a discount rate of 9%. The utility will consider financing 75% of the project costs at 9% over a period of 15 years.
The current electricity tariff is yuan 0.40/kWh (US$0.048/kWh), which is expected to increase 5% annually. General inflation is anticipated to be 2% over the 25-year evaluation term.
All amounts are to be expressed in US dollars. An exchange rate of 0.63 US$/CDN$ can be assumed. Costs in China relative to Canada can be assumed to be 80% for construction equipment, 50% for labour and 85% for equipment manufacture. Fuel costs in China can be assumed to be approximately equal to fuel costs in Canada.
Annual operation & maintenance (O&M) costs would include property taxes (0.2% of total project cost) insurance (0.5% of total project cost), transmission line maintenance (5% of transmission line and substation cost), spare parts (0.25% of total project cost) and labour cost of US$80,000. An additional 10% (of the annual operation and maintenance budget) should be allowed for administration and 10% for contingencies. It is anticipated that approximately US$100,000 will be required every 10 years for major maintenance.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from the analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- A Francis turbine is well suited for the site (150 m head and 4 MW firm power). Assuming a standard efficiency curve for a Francis turbine, efficiency is at least 90% between approximately 60% to 100% of the turbine's design (maximum) flow.
- To generate 4 MW assuming 150 m gross head, 90% turbine efficiency, 5% hydraulic losses, 95% generator efficiency, 1% transformer losses and 1% parasitic electricity losses, a flow of approximately 3.4 m³/s will be required. Adding residual flow requirements of 0.1 m³/s, the firm flow becomes 3.5 m³/s.
- Based on 3.4 m³/s corresponding to 60% of design flow, a design flow of 5.7 m³/s can be selected.
- In order to assess the storage needed to maintain a firm flow of 3.4 m³/s, manipulation of the flow-duration curve is required such that the total area under the modified curve is equal to the area under the curve representing the natural flow conditions. An example of a possible solution is presented below.
- The rest of the RETScreen analysis can be completed using the available data and the formula costing method and applying a factor of 2 to the cost of the renewable energy equipment to account for the cost of the back up turbine and generator.
Real project
Results
The Jiujiedai Hydro Project is located in Ruchen County, Hunan Province, China, on the Jiujiedai River. The project was completed within 3 years and is expected to achieve good economic benefits. The installed capacity of Jiujiedai station is 6.3 MW (with an auxiliary back-up 6.3 MW turbine and generator) and the annual energy output is 51.37 million kWh. The simple dam and resulting storage reservoir resulted in minor flooding and resettlement.
System description
This project consists of a 3,377 m long low-pressure tunnel with a diameter of 3 m and a steel penstock of 486 m with an inner diameter of 2 m. The water diversion system consists of an intake gate of the tower type, located 30 m away from the dam. A surge tank with an inner diameter of 6 m is located 53 m away from the outlet of the tunnel.
The dam is a single-curve masonry arch dam with a maximum height of 26 m and crest length of 69.5 m. The crest width is 4 m and the bottom width is 7.9 m. The dam is divided into a spilling section and a non-spilling section.
There are two powerhouses; a main powerhouse and an auxiliary powerhouse. The electrical switchgear is located in the auxiliary powerhouse.
The 5.7-km long 110 kV power line connects the project with the Wenmin substation. From this switch station, the electricity is sent to Chenzhou grid through Denman 110 kV transmission line.
Lessons learned
The hydropower potential in China accounts for approximately 18% of the global total. The exploitable medium and small hydropower resources are estimated to be 139 GW. Most of the potential sites are located in the vast mountainous regions, which account for 70% of the country's area and which are inhabited by 56% of the total population. The ample water resources can be used to expand rural electrification based on small hydropower development. From 1984 to 1992, 160 million people who had no access to electricity were supplied with electric power, out of which, 58% or 93 million people are supplied with electricity generated by hydropower. Small hydropower is an integral part of the economic vitalization and improvement of local living standards in mountainous areas. By the year 2000, the installed capacity of small hydropower in China reached 30 GW, which produces an annual electricity output of 100 TWh. Chinese small hydropower technology and equipment, in addition to meeting the demand at home, is also exported to other countries.
Photo
Jiujiedai Hydro Project, Hunan, China
References
Results
The Jiujiedai Hydro Project is located in Ruchen County, Hunan Province, China, on the Jiujiedai River. The project was completed within 3 years and is expected to achieve good economic benefits. The installed capacity of Jiujiedai station is 6.3 MW (with an auxiliary back-up 6.3 MW turbine and generator) and the annual energy output is 51.37 million kWh. The simple dam and resulting storage reservoir resulted in minor flooding and resettlement.
System description
This project consists of a 3,377 m long low-pressure tunnel with a diameter of 3 m and a steel penstock of 486 m with an inner diameter of 2 m. The water diversion system consists of an intake gate of the tower type, located 30 m away from the dam. A surge tank with an inner diameter of 6 m is located 53 m away from the outlet of the tunnel.
The dam is a single-curve masonry arch dam with a maximum height of 26 m and crest length of 69.5 m. The crest width is 4 m and the bottom width is 7.9 m. The dam is divided into a spilling section and a non-spilling section.
There are two powerhouses; a main powerhouse and an auxiliary powerhouse. The electrical switchgear is located in the auxiliary powerhouse.
The 5.7-km long 110 kV power line connects the project with the Wenmin substation. From this switch station, the electricity is sent to Chenzhou grid through Denman 110 kV transmission line.
Lessons learned
- There is already a middle-size reservoir hydropower station on the upstream of this project (storage capacity of the reservoir is 15.20 million m³). The reservoir assures good water availability.
- Hydroelectric stations have a long life and many existing stations have been in operation for more than half a century and are still operating at high efficiencies.
The hydropower potential in China accounts for approximately 18% of the global total. The exploitable medium and small hydropower resources are estimated to be 139 GW. Most of the potential sites are located in the vast mountainous regions, which account for 70% of the country's area and which are inhabited by 56% of the total population. The ample water resources can be used to expand rural electrification based on small hydropower development. From 1984 to 1992, 160 million people who had no access to electricity were supplied with electric power, out of which, 58% or 93 million people are supplied with electricity generated by hydropower. Small hydropower is an integral part of the economic vitalization and improvement of local living standards in mountainous areas. By the year 2000, the installed capacity of small hydropower in China reached 30 GW, which produces an annual electricity output of 100 TWh. Chinese small hydropower technology and equipment, in addition to meeting the demand at home, is also exported to other countries.
Photo
Jiujiedai Hydro Project, Hunan, China
References
- Damodaran, Prof V.K., Managing Director, UNIDO International Centre for Small Hydro Power, Hangzhou.
- Parthan, Binu K., "Personal communication," IT Power India, 2002.
