By M.C. Hunter, P.Eng
The 6.0 Mw Rose Blanche hydroelectric development is located on the southwest portion of the island of Newfoundland. This is the first new development undertaken by Newfound-land Power since 1983 and it has represented a real learning experience because of the change in regulatory requirements, technologies available and the working relationships formed with suppliers and contractors. Environmen-tal issues dealt with included a 5 year assessment process, fisheries compensation/enhancement, minimum streamflow requirements, construction and emergency preparedness plans. Technical issues included the use of spiral welded steel penstock, design and construction of an earthfill concrete face dam and turbine generator design and control systems. The necessity to build the plant essentially in one construction season required a cooperative effort from all contractors and suppliers involved in the process.
Newfoundland Power is an investor owned public electric utility with roots dating to 1885. The Company serves approximately 180,000 customers in 600 communities located on the island portion of the Province of Newfoundland and Labrador and it employs approximately 760 people. In addition to the distribution and transmission of electrical energy, 22 small hydroelectric plants comprised of 32 individual units are owned and operated at various locations. The oldest plant was commissioned in 1900 and the newest prior to Rose Blanche was commissioned in 1983. These plants range in size from 250 kW to 15 Mw for a total installed capacity of 87 Mw. They generate, on average, 420 gWh annually which accounts for about 8 per cent of our customer's peak load and 9 per cent of their energy requirements. The balance of capacity and energy is purchased from Newfoundland and Labrador Hydro, a provincial crown corporation.
Consistent with the belief that small hydroelectric installations can provide clean, efficient energy to its customers, Newfoundland Power studied various potential hydro plant sites during the 1980's. In 1991, the Provincial Government changed legislation to permit private development for sites less than 15 Mw. Previous to this change, Newfoundland and Labrador Hydro had exclusive water rights for developments over 1 Mw. The investigation work carried out in the 80's was reviewed at this time and the Rose Blanche project selected for development.
Site Selection
The criteria used to select environmentally and economically attractive sites for potential development were;
The site at Rose Blanche was decided upon because of overall success in meeting the various criteria. It is located on the Rose Blanche Brook on the Southwest coast of Newfoundland, approximately 45 km east of Channel Port Aux Basques. The actual development is approximately 5 km upstream of the community of Rose Blanche.
The dam, which is generally a major cost of a hydroelectric development, would be relatively small and economic at less than 10 per cent of the project cost. The transmission line was also economical as it could be built at a low voltage because of it's proximity to customers. The line is also relatively short compared to most lines for hydroelectric sites accounting for only 3 per cent of the total project cost.
The penstock was determined to be in the range normally expected for a development of this size and, as a result, accounted for about 25 per cent of the cost. The access road was also determined to be economical, as the distance to site is short compared to similar projects.
The powerhouse, turbine/generator, control equipment, substation, etc. were costs that were not going to change significantly much when similar head and flows were involved.
There were no present users of existing resources in the area that would conflict with the operation of a hydro plant. The only potential resource conflict that was found for this location was that the downstream portion of the river served as a water supply for the town. This however would not be affected in a negative way by the development as the hydro plant dam would actually improve water regulation on the system.
Customer service reliability would be improved. The Rose Blanche/Port Aux Basques area is served by a 185 km long series of radial transmission lines that traverse an area which is subject to some of the harshest weather conditions in the Province. The Company has had a concern with the reliability and security of supply to this region for some time and has situated permanent and portable generation there. This done however, there was only sufficient capacity to cover approximately 45 per cent of the peak load requirement. Some of the older diesel generation in the area is due for retirement and situating the hydro plant at Rose Blanche avoided the cost of replacing this equipment as well as increased the amount of peak load coverage.
Economics
The cost of the project was estimated in 1998 dollars to be $13,789,000. This total cost may be broken down by major component as follows;
Roads and Bridges $930,000
Substation $524,000
Distribution, Transmission
and Forebay Line $362,000
Communications $260,000
Penstock $3,000,000
Temporary Facilities $50,000
Forebay Dam, Intake and Tailrace $2,300,000
Powerhouse $975,000
Turbine/Generator and Mechanical $2,650,000
Equipment Installation $300,000
Engineering and Supervision $850,000
Environmental
Studies $450,000
Fishways $225,000
Comp. Channel $225,000
Reservoir Clearing $150,000
IDC $350,000
Misc. Contingency $188,000
Project Total $13,789,000
The project financial analysis was based primarily upon comparing the cost of production at Rose Blanche against;
The only case analyzed against which the cost of Rose Blanche did not compare favourably was a comparison considering avoided thermal energy production. As it is expected that additional generation capacity will be required in 2002, comparing the cost of Rose Blanche with the marginal cost of existing thermal generation beyond that year does not reflect reality. A more valid comparison revealed that the present value of the project was $5.6 million less than the cost of installing peaking generation in 2002. The system losses and new diesel costs combined with the cost of thermal generation exceeded the cost of Rose Blanche by $2.7 million. The long term levelized production cost of energy from the development was determined to be 5.94¢/kWh.
Environmental
When small hydroelectric developments are constructed with proper environmental mitigation, they provide one of the cleanest sources of renewable energy. Because production at Rose Blanche will displace approximately 38,000 barrels annually of oil consumption at Newfoundland and Labrador Hydro's thermal plant, it will not only reduce dependency on foreign -supplied fossil fuel, but will also reduce emissions of sulphur dioxide, carbon dioxide and nitrous oxide emissions, a consideration that has received global attention as a result of the international "greenhouse gas" conference in Kyoto, Japan.
The water rights release was obtained and the project registered with the Environmental Assessment Branch of the Department of Environment and Labour in September 1991.
The Company was informed in November 1991 that an Environmental Preview Report (EPR) was required. This work required field surveys over a number of seasons and a final report was submitted in May, 1995. The document was accepted and the project cleared from further assessment in June, 1995. Up to this point however, the Department of Fisheries and Oceans (DFO) had yet to comment on any fisheries related issues.
DFO responded in May 1996, their concerns addressed and the Company's response submitted in August 1996. DFO's response in January 1997 revealed a necessity for further field work to rationalize the level of instream flow that we had proposed which was less than the rate DFO had requested. The minimization of this flow was necessary as the level has an impact on the annual energy production of the plant. A compensation plan for lost habitat was also discussed at this time and data obtained for the design.
Field work was completed in the summer of 1997 and a comprehensive baseline study carried out in September 1997. An acceptable compensation plan was submitted in October 1997. The essence of the proposal was as follows;
Engineering Construction Schedule
Design of the access road and bridges began in January, 1997, tender issued in June 1997 and construction began in September.
Preparation of the tender package for the turbine-generator water-to-wire package began in early 1997 and the final negotiated contract signed in December, 1997.
The transmission line was installed during the first quarter of 1998 with the engineering of the powerhouse, penstock and forebay dam completed during this time as well. Construction at site started in May, 1998 with rock excavation for the spillway and completion of the access road to the dam and spillway sites. Foundation preparation for the penstock began at this time as well. The dam work started in July and was completed by the end of November. Penstock installation was done in the period of July to December. The powerhouse was started in August and completely closed in by mid October. The turbinE-generator equipment arrived mid November and was fully installed by mid December.
Dam and Spillway
The original dam design concept was for a concrete gravity based structure with an overflow spillway. Site investigation revealed a side channel that had apparently once been the natural outlet for the river. This could be economically excavated and was used for both the diversion channel during construction and the spillway for operations. The design of the dam was then changed to a more economical rockfill concrete face dam. This was designed in conjunction with Acres International. Both the dam and the spillway were designed for 1:10,000 year flood. The contract for the dam and spillway was let to one contractor who was responsible for the excavation and construction of the spillway, the cofferdam, the main dam including the intake structure and provision of the intake and bulkhead gates and hoisting mechanism. A flow compensation valve was provided in the dam so water could be provided to the downstream river when the penstock was drained for maintenance.
Penstock
The penstock tender specified one of three types; woodstave, fiberglass and steel. Given the rough and rocky terrain in the area, it was fully expected that woodstave might have been the leading contender as backfilling fiberglass is typically required for support and steel is usually very expensive. On analysis of the bids, a proposal suggested the use of spiral welded pipe. Though this technology has been used in the gas pipeline industry, we had not encountered it before. This method of fabricating the pipe involves the feeding of the steel from a roll, edge preparation and automatic welding all performed by machinery. This shop welding technique enabled this steel pipe bid to be competitive with the other options. The capital costs in conjunction with the elimination of the maintenance associated with woodstave resulted in the work being awarded to that proposal. The contract covered the design, supply, delivery and installation of the pipe as well as the design and construction of the penstock supports and thrust blocks. The normal waterhammer design specification was for maximum static plus 30 per cent and the emergency waterhammer was maximum static plus 100 per cent. Of note was that the successful contractor was the same that was successful on the dam and spillway. The contractor used a Toronto based engineering firm for the design and a local Newfoundland company for the field assembly welding.
Powerhouse
The powerhouse is a steel superstructure with exterior metal cladding. Once again, the contract was awarded to the same contractor who was successful on the dam and penstock. The scope of work included excavation, supply and erection of the powerhouse superstructure, cladding and doors, supply and installation of the powerhouse crane rail and stops and installation of the owner-supplied 30 ton powerhouse crane. The powerhouse design was done by Acres International in St. John's in consultation with Newfoundland Power.
Fishways and Habitat Compensation Channel
This work consisted of the construction of 2 fishways, repair of the existing town water supply fishway, modification to the existing natural channel to operate as a permanent channel for fisheries habitat and excavation of the powerhouse tailrace channel. This work was awarded to a local contractor in the Port Aux Basques area.
Hydro Turbine-Generator/ Switchgear and Controls
It was decided early in the process that for this size of project, the most cost effective method to procure the prime mover and associated equipment was to contract the work to one supplier who would put together the turbine, generator, switchgear and controls, a so called water-to-wire package. This was done for several reasons;
As Newfoundland Power has a small engineering team, it was felt that our small hydro operating expertise would be best utilized in working co-operatively with a single system designer to ensure that the equipment performed as required rather than in the administration of several smaller contracts. The engineering required to coordinate the individual systems would have been large and would have required the assistance of consultants which would have added unnecessary cost to the project.
As noted earlier, part of the DFO approval was predicated upon maintaining a minimum flow at all times in the river downstream of the plant. This created difficulties with the traditional method of operating a Francis turbine hydro plant which involves shutting the unit down during low flow periods to allow storage to build up. Once there is sufficient storage, the unit would be operated at best efficiency until the water is depleted, at which time the cycle would begin again. In order to maximize the production at the plant, it was felt that the unit should be able to operate at high efficiencies down to a relatively low flow as compared to the full flow rate. Rather than dictate the solution to the potential suppliers, the tender was written such that they could propose any type of unit or arrangement that would maximize the production given the flow regime. From a technical perspective, the units would need to be able to operate in the ranges noted and still meet the cavitation guarantees. This process resulted in several different types of bids including single Francis types, double Francis in a single spiral case and twin Francis turbines in separate spiral cases.
The contract was eventually awarded to Sulzer Hydro who proposed a twin turbine concept with a single generator mounted between the turbines. This concept had very high efficiencies over the flow range.
Their proposal provided the additional benefit of having the turbines and generator mounted on a single base. This enabled the entire unit to be shop assembled rather than having to do it in the field thus making it easier to fix any problems that could occur. The basic unit alignment was also done in a shop setting providing for a much faster field installation. The unit was shipped as an assembly with the exception that the spiral cases and runners had to be removed due to load restrictions on the highway through Nova Scotia.
In addition to the turbine-generators, Sulzer provided the bifurcation, inlet valves, high pressure hydraulic oil unit, governor and unit controls and switchgear. The control scheme was developed through a collaborative process with Newfoundland Power, Sulzer and their electrical subcontractor Thompson Technology Inc. As we are used to the various types of operation that may be required, we specified the water management scheme that was necessary. This included modes of operation such as constant water level, constant load, "normal" operations (best efficiency or, depending upon inflow, maximum load either one or both turbines) and black start capability. As the plant is at the end of a long radial transmission line, the capability to black start the unit and pick up customers during emergency conditions was essential. Again through collaboration between the supplier and the owner, the capability to pick up load in 2 Mw increments was designed into the plant. The transmission line from the plant to the customers was sectionalized to provide the proper load profiles for these circumstances.
Prior to the controls and switchgear being shipped to site, NP's senior controls engineer spent time in the subcontractor's factory reviewing the programming and the equipment. This again saved time on site as a minority of changes were required during commissioning.
A fisheries compensation valve was purchased and installed in the plant for times when the inflow to the system is too low for the units to run economically or when it is down for maintenance. The valve was specified to pass the required instream flow unless the reservoir head decreased past a certain level.
The valve controller would then throttle flow in order to maintain a constant head thus matching discharged flow to the actual inflow to the system. Should the head begin to increase due to higher flows, the controls are designed to open the valve to the minimum flow requirement and regulate there. The head would then continue to build until there was enough water to operate one turbine at best efficiency.
Installation of all of the equipment was achieved using Newfoundland Power's own engineering, electrical and mechanical workforce supplemented by local construction trades. Sulzer and its subcontractors provided installation and commissioning supervision and technical assistance.
Substation
The substation was designed and constructed by Newfoundland Power personnel. The transformer is a 7000 kVa unit which steps the voltage from 6.9 kV to 25 kV for transmission to the grid. A line side breaker is provided on the high voltage side to protect the transformer from potential high fault currents on the network in the Rose Blanche area. Two station services are provided, one from the high voltage side for normal shutdown conditions and one from the low voltage side for provision of services under black start conditions. An auxiliary power unit is also provided in the powerhouse for the provision of emergency lighting and battery charging.
Conclusion
The Rose Blanche unit was synchronized to the system on December 22, 1998. In general, Newfoundland Power was pleased with the project and the way it was accomplished in what was recognized as a very aggressive schedule. This was achieved by the approach taken by the design and construction team of focusing on minimizing the amount of project management necessary and by working in conjunction with the suppliers and contractors in developing the most expedient and cost effective methods of construction. Small hydro projects cannot be burdened by excessive project management as this takes too much time and causes the project too much overhead cost. Tight control of timelines and costs are essential but this is achieved through dealing with the situations at site rather than through a more typical project management office. It is interesting to note on this project that the environmental permitting timeline was far longer than the actual construction time. The environmental mitigation cost was approximately 7 per cent of the project cost with the engineering and supervision cost only 6 per cent. This is indicative of the trend in hydroelectric developments where significant time and project costs will have to be devoted to the environmental issues.
M.C. Hunter is Manager, Energy Supply with Newfoundland Power Inc. ET