ENERGY
South Africa is on a low-carbon trajector y 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
I
nverter-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).
52
IMIESA May 2020
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 ser vitudes for the lines. A ser vitude 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 per formance of current coal-fired power stations is worse than anticipated. The proposed IRP, if implemented according to plan, may not be suf ficient 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:
• I nverter-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 ancillar y ser vice 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: • L earn 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. • R educe 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
