Africa

New Development: Best of the Year

Tekeze and Canoe Creek hydropower projects win Project-of-the-Year awards at POWER-GEN International event in Orlando.
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Tekeze and Canoe Creek Hydropower projects win Project-of-the-Year awards at POWER-GEN International in Orlando.

By Lindsay Morris

On Dec. 14, Power Engineering magazine recognized the 2010 Projects of the Year Award winners during an awards dinner at POWER-GEN International in Orlando.

Two hydropower projects – the Canoe Creek Hydroelectric Project and the Tekeze Hydropower Project – were among the winners.

The 5.5 MW Canoe Creek project is a run-of-river facility that is owned and operated by Tla-o-qui-aht First Nation. The 300 MW Tekeze project boosted Ethiopia’s electric capacity by 40 percent.

Best Renewable/Sustainable Project

Tekeze Hydropower Project

The Tekeze Hydropower Project in Ethiopia, located a tributary of the Nile, is the Project of the Year for renewable/sustainable projects. The $350 million project, funded by the government of Ethiopia and owned by Ethiopian Electric Power Corp., adds 40 percent more electric capacity to the country and was the largest public works project in Ethiopia’s history at the time of construction.

Due to the lack of natural resources and the cost of imported fuels, power generation in Ethiopia comes primarily from hydroelectric sources.

The Tekeze project is the tallest arch dam in Africa at 188 meters. The 300 MW facility includes a double curvature concrete arch dam, a method of design that minimizes the amount of concrete used.

It created a reservoir 70 kilometers in length. An underground powerhouse containing four 75 MW Francis Turbines sits 500 meters downstream of the dam and is fed by a 75-meter-high intake structure connected by a 500-meter-long concrete-lined power tunnel.

A 230 kV double-circuit transmission line 105 kilometers long was constructed through mountainous terrain to connect to the Ethiopian national grid.

The project’s beginnings date back to 1995 when the Ethiopian Ministry of Water Resources conducted a study identifying the site as one of two preferred dam sites for hydropower development. MWH joined the project in 1998 and made modifications to an existing design for the dam, powerhouse and tunnel system, resulting in cost savings.

A multi-stage impoundment approach was implemented during construction, which allowed the river diversion to be closed in May 2007, nearly two years prior to dam completion. This allowed for more than 3 billion m3 of water to be retained, advancing generation by more than one full year.

The value of the water captured via early impoundment was worth approximately $40 million. In addition to power generation, the Tekeze dam enables regulation of river flow, allowing downstream communities year-round access to the water supply.

A 10-year 2000m3/sec flood on Aug. 9, 2006, was an unexpected test for the dam. The dam proved its ability as a gravity structure and no damage was incurred to any of the permanent structures.

Local community infrastructure was improved as a result of the project, including construction of more than 40 kilometers of roads and installation of the first communications links from the area to the outside world. Also, as a result of the project, education was improved in the area as the wife of the MWH chief design engineer spearheaded efforts to build a new school near the village of Seboko.

The school was financed by contributions from engineers, contractors and staff working on the project, local residents and a supportive local government.

On-the-job training was also provided to locally-hired employees. Ethiopian Electric Power Corp. implemented programs to provide education and training to local workers. Programs included education to combat AIDS, malaria and other safety, health and welfare issues affecting the local community.

Honorable Mention

Canoe Creek Hydroelectric Project

Canoe Creek Hydro is a 5.5 MW run-of-river hydroelectric facility on Vancouver Island that provides power to a remote community on the island and helping the island become less reliant on mainland power.

The facility is owned and operated by the Tla-o-qui-aht First Nation and located in the heart of the Nation’s Tribal Parkland.

The Barkley Project Group Ltd., along with Amnis Engineering and Hazelwood Construction One, worked with Vitaulic, a manufacturer of mechanical pipe joining solutions, to develop Canoe Creek.

The 300-MW Tekeze Hydropower Project in Ethiopia boosted the country’s generating capacity by 40 percent.

Construction started in May 2009 and ended in May 2010. The plant went into service in June.

Canoe Creek Hydro operates by diverting stream flow into a penstock at a high elevation- up to 84 percent grade – intake.

This made construction a challenge, as did the facility’s location in the Pacific Rim Rainforest, where annual precipitation is amongst the heaviest in the world, particularly in the winter months when construction took place.

Constructing the 4-km-long penstock line in these conditions using welding techniques would have proven difficult. Instead of using mechanical welding on the penstock, the companies used mechanical couplings. In the field, the couplings proved advantageous in many ways.

For example, couplings could be installed in any weather condition with no special requirements.

Couplings also reduced the amount of excavation, bell holing and dewatering that would be common with welding work.

Couplings also improved site safety. As the pipe was already on site, Hazelwood grooved and re-coated the pipe prior to sending it up the single-lane logging road for assembly.

The Canoe Creek Hydropower project on Vancouver Island operates by diverting stream flow into a penstock at a high elevation – up to 84 percent grade – intake.

In addition, the replacement of welding with mechanical joints allowed for a reduction in the number of laborers required on the job site.

Canoe Creek also employed local laborers.

Environmental benefits were also gained by replacing welded joints with mechanical joints.

Welding one kilometer of straight-run 36-inch pipe produces about 40,338 kg of CO2 emissions using a diesel-powered machine and 9,463 kg of CO2 emissions using an electric-powered machine.

Grooving and coupling that same run of pipe produces 62 kg of CO2 emissions. The use of couplings also reduced the amount of x-raying required on site, reducing radiation emission.

Lindsay Morris is associate editor of Power Engineering magazine.

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