Wind and solar are no quick fix for load shedding

While punted as the silver bullet that will solve South Africa’s energy crisis in an environmentally friendly way, the truth about these renewables paints a more challenging picture.

By mid-November, South Africa’s utility giant Eskom will have exceeded 1 000 hours of load shedding for 2021, making this the worst year on record. Homes, schools, clinics and countless workplaces are facing the dual crisis of increasingly unaffordable and unpredictable electricity supply.

The need for decarbonisation of the energy sector as part of our responsibility to mitigate against the impacts of climate change requires shifting the use of fossil fuels for electricity generation. Globally, alternative energy sources such as large-scale hydro, nuclear, wind and solar photovoltaic (PV) generators are used in various combinations as strategies to achieve governments’ emissions targets. South Africa has identified solar PV and wind technologies as part of its increasingly aggressive strategy to reform the sector by 2030. 

The reality is that variable generation from these resources has its technical and economic challenges, which constrain our options in an energy system that already faces severe issues. The projected short-term rollout of wind, solar and gas projects’ potential to address the wave of load shedding between September and November gives a sense of the scale of these challenges.

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South Africa’s total installed generation capacity stands at roughly 47GW. It consists of coal, nuclear, pumped storage (hydro), gas, diesel, solar PV, concentrated solar PV (CSP) and wind-based power plants. 

The plants for each of these energy sources have different technical characteristics and requirements that shape their performance and how they are managed. Wind and solar farms have zero fuel costs, but are wholly dependent on the nature of solar irradiation and wind patterns in their areas.

A key measure of performance for Eskom’s power plants is the energy availability factor (EAF), which is the ratio of available generation capacity to installed generation capacity. 

Eskom’s EAF had fallen to below 65% by November, as high levels of planned maintenance coincided with the declining performance of the existing coal fleet, which is increasingly susceptible to plant failures and unplanned outages. As a result, Eskom has had to run its fleet of open-cycle gas turbines, which run at relatively high cost, for long periods to meet the shortfall. 

A measure too short 

In terms of future renewables capacity, the Risk Mitigation Independent Power Producer (RMIPP) procurement programme, which is already facing delays, stands to add almost 2GW of dispatchable power including gas, wind turbines, solar PV and battery banks.

The fifth competitive bidding round of the Renewable Energy Independent Power Producer Programme (REI4P), initiated a decade ago, released results of its process at the end of October, with winning projects totalling over 2.5GW of variable generation (wind and solar plants) at record low tariffs (at a minimum 0.34c/KWh and average 0.47c/KWh.

Statistics from Eskom’s data portal indicate the extent to which existing and prospective renewable energy projects can be expected to reduce the need for load shedding in the short term.

Figure 1 shows the aggregate power output from wind, solar PV and CSP from 1 September to 7 November, which totals 1 513 hours. Their total installed capacity was 5.76GW but peaked at only 4.3GW at an average of 1.98GW in this period. 

The capacity factor, which is the ratio of actual energy produced to maximum energy output, over that period came to only 34.58%, which is within the expected range for wind and solar PV generators. 

Figure 1: Wind, solar and CSP power output into the South African grid from 1 September to 7 November 2021. (Source: Eskom Data Portal)

Figure 2, the performance of existing REI4P plants, is shown alongside projected performance once the new bid window five and the RMIPP projects come online. The analysis assumes that all projects are located in similar areas and run at full capacity for the full duration.

Figure 2: A figure comparing the performance scenarios of the existing installed renewable energy with REI4P bid window five and RMIPP projects with the 4GW Eskom capacity shortfall requirement. (Source: Engineering News)

With as much as half of the coal generation fleet offline by mid-October, an additional 4GW of generation capacity would have been required to avoid stage four load shedding. 

Figure 2 allows us to assess the current and medium-term capacity of the renewable energy sector against the threshold of our current predicament. Existing renewables delivered more than 4GW on an hourly average for only seven hours (0.46%) and more than 2GW for 567 hours (39.42%) over the 1 513-hour period. 

At this level of performance, even if they materialised overnight, the proposed 25 projects from the REI4P and eight RMIPP projects would still only meet the 4GW threshold 37.5% of the time. 

The proposed rollout of renewable energy sources are therefore unlikely to solve the national shortfall over the next few years, and the challenge of improving the performance of Eskom’s existing coal fleet cannot be avoided to address reliable electricity delivery.

The harsh reality

Energy storage options such as large batteries are often presented as silver bullets for handling the variable performance of wind and solar power. Eskom itself has already begun raising finance, initiated by a $57 million (R870 million) investment for a battery energy systems project consisting of 200MW (800MWh) with four hours of capacity per day, distributed across seven sites throughout the country. 

While these battery systems will benefit from the increased use of renewable energy in the grid, projects of this scale come nowhere close to compensating for the low capacity factors typical of wind and solar plants. For this reason, complementary energy resources will be required to quickly ramp up and down production in response to their characteristic variability. 

The implications of the real performance of variable renewable energy resources in our national grid pose significant challenges for South Africa’s decarbonisation efforts. However, if this task is to be navigated successfully, we require more critical assessments of the trade-offs involved in the energy transition than the current public debate has allowed for thus far.

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The harsh reality facing the electricity sector is that in order to stabilise the national grid and curb load shedding over the next two years, the existing coal fleet will need to be repaired urgently. It is clear that maintenance has not been a priority for the regime, and finances – and external technical support where necessary – will need to be expedited by the state to bring as many of the available coal generators online. The entry of alternative energy technologies will have to remain medium-term options that are installed in a phased manner but unfortunately offer little ability to resolve the immediate crisis.

South Africa is poised at a cliff edge and needs an urgent commitment to rebuild Eskom into a public utility capable of managing trade-offs and facilitating a just and equitable energy transition in a phased, technically sound manner. 

Instead, those charged with governing the sector arguably most critical for facilitating economic and social progress appear determined to hand over their responsibilities to private hands. Reconfiguring our already unequal energy sector to create secure, de-risked opportunities for multinational private power utilities, commercial banks, large landholders and private equity players abroad will not serve the interests of all South Africans, but enrich a select few in the name of climate justice.

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