Pumped Storage Power Generation Kicks in Fast for Peak Loads

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Researched by Industrialinfo.com (Industrial Information Resources Incorporated; Houston, Texas). The need to meet demand peaks in electricity supply systems could see healthy growth in pumped storage power generation projects worldwide. Generation based on pumped storage is cost efficient compared to combustion-based systems in meeting peak load situations and plant can be brought into full operation from standstill within about three minutes.

A 1,330 MW scheme is entering the first phase of final design for Eskom (Johannesburg), the South African power utility that supplies 95% of the country's electrical power and 50% of the African continent's power. The feasibility study has been completed on the Braamhoek pumped storage scheme which will be sited on the escarpment of the Drakensberg mountain range on the borders of the Free Sate and Kwazulu-Natal provinces.

The scheme is designed to avoid peak capacity deficiencies that could occur as Eskom drives its massive electrification-development process into the furthest corners of the rural areas of the country.

The $500 million project will see dams at the top and base of the escarpment with water being pumped back into the top dam by reversing the turbines in off-peak periods. The project specifications contain two dams, underground waterway tunnels, an underground powerhouse complex, access tunnels and access roads. Powerlines from the scheme will run into the nearest electricity grid.

With the final design phase expected to take about 30 months, Eskom is currently looking for consultants to carry out geotechnical investigations, layout of electromechanical, and the basic tender and design of all primary civil and building work, including associated infrastructure.

Having identified the need for the project and completed the feasibility study, Eskom is proceeding with the project that is scheduled to be fully operational by 2012. Although, it is not clear at this stage whether Eskom will find an equity partner for the project, it will be examining a number of ownership models between now and the start of construction which will include joint venture funding options.

The timing of the project will be of particular interest to possible partners as Eskom will be going through various stages in the privatization process during the same period and will be increasing its continental and global outreach in addition to bringing its organizational and professional resources to bear on non-core projects such as its share in South Africa's third cellular phone service provider. Around 2007/8 it will de-mothball power generating resources as demand outstrips current commissioned supply sources. Having new associates may assist the privatizing giant to obtain new power generation construction contracts that will be awarded in open, competitive bidding to 'independent' companies.

Larger pumped storage generating schemes worldwide are generally in the 1,000 MW plus range with Kannagwana in Japan at 2,700 MW and Tienhuangpuing in China's Yangtze Delta at 1,800 MW at the upper end of the scale. Industrialinfo.com has reported on 23 pumped storage hydro power projects worldwide in recent years, as part of its International Industrial Database

Click on the image to the right to view the Top 6 Pumped Storage Hydro Power Projects Table

A World Bank brief on pumped storage projects highlights appropriate siting, equipment and construction in view of the high costs associated with the systems. Cost effective sites with head ranges between 300-600 meters in relatively steep topography. A low waterway to head ratio reduces the need for surge tanks to control transient flow conditions and higher head projects require smaller volumes of water to provide the same level of energy storage and smaller size waterway passages for the same level of power generation.

In 1977, the Sterkfontein dam project was commissioned by the national water authority to pump water from the strong flowing Tugela River up and over the Drakensberg mountain escarpment. The dam provides deep, low evaporation storage and releases water into the Vaal Dam river feed system on the Highveld plateau, which feeds South Africa's highest concentration of industry and population in the Pretoria-Johannesburg area (5,000-6,000 feet above sea level). Water is pumped up 500 meters from the Tugela reservoir at 173 cubic meters/second by four 250 MW pump turbines during periods of low demand. During periods of peak demand in the morning and evening water is released from the upper dam at a rate of 312 cubic meters/second to generate up to 1,000 MW of power.

South African has the terrain, civil and power engineering skills to develop this form of power generation. Hydro engineering on a major scale has taken place in the country over the past three decades including pumping water over mountain ranges, tunneling, damming and reversing river flows to provide water supply to citizens and industry. The World Bank brief also says that the use of abandoned mines could be considered for pumped storage power generation schemes. Core engineering expertise developed over the years is available for projects to generate clean peak power.