Generating power, saving the planet
Eskom pulled out all stops during the construction of the Palmiet Pumped Storage Scheme to minimise the impact of the project on the environment.
Eskom’s commitment to taking care of the natural environment where its power stations operate is not new. The Palmiet Pumped Storage Scheme, commissioned in 1988, is regarded as a forerunner in environmental engineering.
Situated on the Palmiet River in the Western Cape, it is unusual in that it not only generates peaking power for the country’s national grid, but its reversible pump/turbines also act as a link in an inter-catchment water transfer. The dual role of the storage scheme makes best use of the country’s scarce water resources.
Extraordinary measures were taken to safeguard the environment during construction of the project, as it is located in the heart of the Cape Floral Kingdom; the smallest, but most diverse plant kingdom in the world.
Water and electricity supply
Water: for decades, the Steenbras River and its reservoirs have supplied water to Cape Town, but population and industrial growth create an ongoing need for more water in the Western Cape. The then South African Government Department of Water Affairs and Forestry (DWAF) identified the Palmiet River as a potential source of water for the city, provided its waters could be transferred across the range of mountains separating it from the Steenbras catchment.
Electricity: given South Africa’s scarce water resources, a conventional hydroelectric power station was not a feasible option for peak power generation. The solution, it was decided, lay in the construction of a pumped storage scheme with reversible pump/turbines. Water stored in an upper reservoir is released to drive the turbines during periods of peak demand and pumped back at night and over weekends when demand for electricity is less.
The Palmiet Pumped Storage Scheme was thus carried out as a joint venture between Eskom Holdings and DWAF, with engineers beginning work in 1983. Construction of the two reservoirs was undertaken by DWAF, while Eskom oversaw the building of the power station with its reversible pump/turbines and associated waterways.
Water from the Palmiet River is pumped to the high-lying reservoir in the mountains, from where it gravitates into the Steenbras system for Cape Town. The volume stored permanently in the two reservoirs provides Eskom with the generating capacity it needs for peak electricity demands. The power utility commissioned the two 200 MW units in 1988. Both organisations contributed to the capital costs of the project and the partnership continues, with Eskom operating the power station and DWAF the reservoirs.
The Cape Floral Kingdom is extremely diverse, and 70% of the ‘fynbos’ (from the Dutch ‘fijn bosch’, which means ‘fine-leaved bushes’) plant species are endemic and not found naturally anywhere else on earth. The Kogelberg is regarded as a centre of this biodiversity and is justifiably known as the heart of the fynbos plant kingdom. In 1998, UNESCO registered the area as a biosphere reserve; the first in South Africa.
A multi-disciplinary Palmiet Committee was established in the early stages of planning for the scheme and comprised representatives from many state bodies, educational institutions and societies, all with specialist knowledge. An environmental impact control plan, considered a forerunner of its time, was developed and implemented. Here, the overall approach was to implement controls from the outset and to rigorously follow them throughout the construction, with particular attention being paid to the protection of the unique fynbos flora. This proved to be an effective and economically viable approach.
The in-stream flow required to satisfy ecological needs was established, and operating rules ensure that releases of water mimic natural seasonal cycles, so that extractions do not compromise the in-stream flow requirements. Transfers from the Palmiet River increase the annual yield of the Western Cape system by an average of 22,5 Mm3 per annum.
Blue Planet Prize
The vision of the International Hydropower Association (IHA) is to advance sustainable hydropower’s role in meeting the world’s water and energy needs. At Hydro 2003 – held in Cavtat, Croatia – the Palmiet Pumped Storage Scheme received international recognition in the form of the Blue Planet Prize from the IHA. The prize recognises good practice and sound management in the development and operation of a hydro power scheme, on the basis of technical, economic, social and environmental criteria.