Green Jobs

Eskom may soon pull trigger on 100-MW solar-energy project - 1 February 2008

Embattled power utility Eskom will decide later this year whether it will go ahead with its 100-MW solar energy project, earmarked for the Northern Cape.

“We are hoping for a decision to continue with the project – or not – by March or April,” says Eskom renewable energy corporate specialist Louis van Heerden.

He says the feasibility study for the project was completed at the end of last year, and that “the results are currently being evaluated”.

“Aspects to be considered include costs, the risk associated with the construction and operation of such a new technology, and how the project fits in with Eskom’s greater electricity-supply plans.”

Eskom has a five-year, R300-billion capital expenditure plan to deal with the current electricity supply shortfall. The utility’s proposed solar project last year received approval from the Department of Environmental Affairs and Tourism. In 2001, Eskom initiated a feasibility study to determine the more suitable option between either a trough or a central-receiver system for the purpose of the solar project.

In the end, the molten-salt-type central-receiver technology was the favourite.

Eskom then launched the latest feasibility study on the project, this time focusing specifically on the central-receiver system.

Central-receiver technology concentrates the sun’s energy through multiple large mirrors, using the concentrated thermal energy to produce steam to drive a conventional steam turbine for electricity generation.

The energy concentration is achieved by a field of large sun-tracking mirrors (called heliostats), which reflect the sunlight to a receiver, mounted on a central tower in the middle of the mirror field.

A heat-transfer medium (molten salt) is pumped through the receiver, absorbing the highly concentrated radiation reflected by the heliostats.

The heated fluid is then circulated through a heat exchanger, where the thermal energy is used to generate steam and power a turbine.

Temperatures within the system can reach in the region of 600 ˚C.

Upington was chosen as the most likely site for the project as each year the Northern Cape records some of the highest aggregates of sunny days a year worldwide.

. . . Read the remainder of this article by Irma Venter on Engineering News.