supply industry

South Africa is on a low-carbon trajectory and many of the existing coal-fired power stations will have to be replaced within the next 10 years. So, what are the options and alternatives? By Dr Rob Stephen*

Implications for SA’s electricity supply industry

Inverter-based (renewable) systems such as PV and wind provide cheap energy, since the fuel is free; however, they do not provide the full suite of attributes required for a power system. Ideally, one needs to provide a balance to ensure the inverter-based resources are complemented by other generation types to ensure a stable and reliable supply of electrical energy.

One of the major areas requiring attention is inertial response for frequency control. The Integrated Resource Plan (IRP) mentions that – due to the expected low penetration of renewables, i.e. below 40% – this will not be an issue before 2030. However, at low loads with high solar and wind generation, it is possible that the inertia required may be inadequate well before 2030.

Studies need to be done to ensure that either the decommissioned plants are converted to synchronous condensers or that inverter-based resource generation is curtailed. Energy storage systems should be included in the inverter-based generation packages. Markets should be introduced with a move away from ‘take or pay’ power purchase agreements. The ability to curtail inverter-based generation should be permitted with limited penalties (which are payable by customers).

What about the infrastructure?

The IRP as proposed does not mention the infrastructure needed to incorporate the proposed generation. Eskom estimates that an amount of R20 billion is required for integration. This includes 2 650 km of transmission line. A major risk to the success of the plan is the acquisition of servitudes for the lines. A servitude can take up to 10 years to acquire. The IRP, however, requires generation to be available in two to three years.

Another aspect to consider is that the performance of current coal-fired power stations is worse than anticipated. The proposed IRP, if implemented according to plan, may not be sufficient to ensure a reliable supply of electricity in the short term.

Government’s recently issued RFI (request for information) intends to address this by inviting power producers to tender for short-term generation, which could mitigate the need for load-shedding. This is an excellent initiative and, although it may be criticised as being too little too late, I feel it is a step in the right direction.

Responding to the road ahead

The reality regarding the future generation and load mix is as follows: • Inverter-based resources will continue to drop in price, providing low-cost energy, albeit erratically. • Storage costs are likely to continue dropping, which can provide short-term energy and ancillary service support. • Demand for electrical energy is likely to increase. The supply of electrical energy will be varied between households, utilitysized generation from independent power producers, and the current utilities. • The operation of the grid will become more difficult, with variable generation in size, duration and location causing risk to frequency, fault level and voltage support. How can South Africa respond to this scenario? The answers are as follows: • Learn from other countries: the deregulation, advent of markets and renewables has been in place for the last 20 years. Solutions have been found to almost any scenario and engineers are continuing to develop others. • Reduce bureaucracy by creating markets: at present, applications need permission from government, including the regulator. It may be more efficient to create a market for generation and allow authorities to monitor the market adherence rather than investigate

each potential generation source. Again, solutions in Denmark and Germany can be investigated. • The acquisition of servitudes needs to be expedited dramatically, also through reduced bureaucracy. • Plan for small, rapidly installed, flexible generation units that can be placed where needed with short lead times. The days of large baseload mega plants are limited and may lead to late installation or oversupply. • Design the grid components for robust plans that can cater for large variations in load transfer and reduced initial capital costs. This is due to the load scenario being highly variable and uncertain.

Engaging with CIGRE

What does this mean to CIGRE members? Founded in 1921, CIGRE is an international non-profit association for promoting collaboration with experts from all around the world by sharing knowledge and joining forces to improve electric power systems. It consists of over 10 000 members from more than 90 countries. The organisation’s aim is to transfer technical knowledge and to develop solutions to problems faced by members. This is achieved by forming working groups consisting of international experts who are knowledgeable in specific areas.

One fortunate aspect of the challenges Eskom faces is that other utilities have faced similar ones over the past two decades. CIGRE has developed a number of solutions, such as market design, grid operation with a high penetration of renewables, protection philosophy and design with varying fault levels, and planning in an uncertain environment. It is possible, therefore, that all the issues faced by Eskom and the electricity supply industry could be successfully addressed by engaging the international experts in CIGRE.

Another exciting development is the rapid generation and use of hydrogen as the energy of choice for transport and other sectors. Renewable energy generation, when in surplus, could be used to generate hydrogen from water. This ‘green’ hydrogen

can be exported or used locally for trains, trucks and other applications. This would mean that South Africa could maximise the installation of renewable energy generation if the grid curtails the output, as the balance could be used to generate hydrogen for export or local use.

Conclusion

We live in exciting times. Fortunately, solutions exist for most of the challenges the South African electricity supply industry, including Eskom, is facing. We need to leverage the information and expertise of organisations such as CIGRE and learn from other countries. That way, we can best ensure a reliable, efficient and sustainable electrical energy supply into the future.

Author’s note: The comments provided above are my own and not necessarily those of CIGRE or Eskom.

*Dr Rob Stephen is the international president of the International Council on Large Electric Systems (CIGRE).