Baseload electrical energy is, for the purpose of this article, energy that is readily dispatchable at a predictable energy availability factor level (EAF). The primary energy that enables dispatchability and predictable EAF are nuclear and fossil fuel.  The most compelling aspect of baseload that need consideration is that, power generation must be relatively continuous. Baseload therefore means electrical energy source that can be completely relied upon.

How about solar and hydroelectricity

Solar energy is used in two different forms as a source of primary energy, viz: (i) solar photovoltaic and rechargeable battery and inverter system; and (ii) concentrated solar and turbo-generator system. In these formats, Solar Energy does not meet baseload requirements as per the above-mentioned definition. During the period when the sun’s radiative intensity is lower than required, concentrated solar is unable to heat the working fluid to desired temperature levels or when the sun emits higher than required radiative intensity and photovoltaic cells lose their overall efficiency.

The intensive study on solar rays’ physical behaviour has yielded Improvements on these solar-oriented system.  Recent designs and application of heat storage systems have allowed for the storage of useful heat over an extended period of time and photovoltaic cells are now being designed and built to withstand beyond design-base heat intensity.  Photovoltaic is inefficient and require large space (agriculturally productive tracks of land could be lost to this technology) for small energy output, also then photovoltaic’s operational life is notoriously short. Soon solar will be engineered to meet the baseload requirements as defined above.


A dam built across a river and a pumped-storage reservoirs with associated penstocks and turbo-generator arrangement can generate hydroelectricity.  In both cases, the amount of hydro-electric power generated is inversely proportional to the hydraulic head of the source. South African hydroelectric systems suffer low EAF as the seasons change from rainy to dry. The pumped storage system has an added disadvantage as its availability is already compromised due to necessary pauses between generating and pumping water back into reservoirs. Hydroelectric generation is therefore not a suitable baseload system (as per this article’s definition) for South Africa due to the fact that the South African river systems in unsteady and unreliable.

Other potential sources of energy

The other South African energy resources such as wind and tidal energy are analysed in Table 1 hereunder.

Table 1:  Tidal Wave and Wind Power Energy Resource Evaluation in South Africa

Grid stability issues

Even if PV solar, wind and battery energy technologies succeed at providing most of the energy required and they significantly surpass electrical energy generated by synchronous generating machines, a new problem would ensue. These inverters are not capable of keeping the grid stable, safe and efficient. The grid stability is defined as the grid’s ability to remain at the specific frequency and voltage levels.

The inverters in renewable energy generators mentioned above do not have capabilities to prevent the inertia shortfall, unless if further investment is made into equipment such as the synchronous condensers. The synchronous condensers emulate the synchronous turbo-generators in keeping the grid stable, safe and efficient.

Conclusion and necessary forward

A diverse baseload energy generating portfolio that includes renewables and aims to reduce adverse environmental impacts and associated externalities is essential for driving the country’s economy. As has been indicated herein, nuclear energy is an obvious choice for such a baseload portfolio. The other energy sources that must be explored and evaluated for the South African baseload is a geothermal energy source.

Rudzani Tshitahe, Pr. Eng, MSAIMechE
South African Institution of Mechanical Engineering (SAIMechE)
Tel: (011) 615-5660

2 Responses

  1. Nuclear energy is not a viable for SA given that it is a capital intensive investment which rarely is on budget and on time vis Hinckley Point in the UK and many many other plants. There is considerably more research development and investment in storage technologies which are becoming cheaper by the day whereas traditional energy generation systems are becoming more expensive by the day because of the environmental impacts which have to be ameliorated. Storage technologies for renewables are rapidly deployable in contrast to other power generating options such as nuclear where you pay now and if you are lucky you receive power 10 years down the line from a system the design of which is 10 years old and probably 150% over the original budget. SA has many many other alternatives and unless some private enterprise wants to invest in nuclear technology and supply power at a competitive price it is not a viable option by a long stretch.

    1. I agree with most points you raised, the point argued was only to support nuclear as a viable baseload technologyu as compared to the other generating technologies mentioned. As for private enterprises being competitive, that has been proven to be a fallacy in these reported cases reported by Reuters: half of capacity from the 2021 renewable energy delivery windows failed, six projects failed to raise finances and six others never signed agreement. These private enterprises often argue that access to the national grid is a major constraint for them, but once the access is provided they sing a different tune.

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