In recent years, we have seen a global move towards the use of renewable energy, in particular Photovoltaic (PV) solar energy. However, PV generation is not necessarily the obvious choice for Africa.

Concentrated Solar Power (CSP) may be a better alternative, as it is particularly suited to sunbelt countries.

This is according to Matthew Coulson, Intern, EES Africa (Pty) Ltd. EES Africa is a South African-based, ISO 9001:2008 certified company providing management, engineering and auditing services to a range of industries throughout Africa.

The South African scenario

South Africa is seen by many industry players as a paradigm for Africa when it comes to renewable energy generation.

As part of its national strategy to shift the country’s energy supply from its mainstay, coal, to green renewable energy sources, the Department of Energy (DoE) in South Africa has implemented the Renewable Energy Independent Power Producers Procurement Programme (REIPPPP).

PV, wind and, to a lesser extent, CSP plants are now being constructed or are in operation. To date, the REIPPPP has procured multiple gigawatts of renewable energy at costs increasingly competitive with coal-fired electricity.

Recently South Africa completed its first CSP plant, KaXu Solar One in the Northern Cape, and four more are under construction.

What is CSP?

CSP produces energy by means of thermal generation techniques. “CSP uses parabolic troughs, which are curved, mirrored troughs, to reflect direct incoming solar radiation onto an absorption tube containing fluid,” says Coulson. “Other methods make use of parabolic dishes and solar towers with solar radiation reflected into the tower by mirrors or ‘heliostats’.”

What is holding CSP back?

Development of CSP has been largely neglected in favour of PV production. The technological maturity of PV, along with its suitability in regions where diffuse radiation is prominent, has given PV generation the advantage.

“CSP technology is not well developed and, for this reason, installation prices of CSP plants are prohibitively high, about triple that of a PV plant per MW,” states Coulson. “However, these prices are predicted to fall rapidly with development and maturity of the CSP market.”

CSP’s role in grid management

Traditionally, electricity generation plants can be categorised as base load and peak load (peaker) plants.

Base load refers to electricity generated by ‘always-on’ plants which continuously output a set amount of power. Peak load plants are used to supplement base load plants at peak electricity usage times.

The main renewable energy sources, PV and wind generation, cannot be classified as either of these types of plants.

They are instead classified as intermittent sources of electricity. Intermittent sources put more pressure on the peak load generation plants as the grid is burdened with a greater level of fluctuation.

With the increase in intermittent sources of renewable energy must come a larger peak load generation capacity too.

“CSP is capable of contributing to peak load power generation capacity to supplement the intermittent sources. Its ability to dispatch power on demand is extremely valuable and will become increasingly important as the grid adds more intermittent sources of energy,” Coulson concludes.