Wietze Post – What if the wind don’t blow and the sun don’t show? 

Wietze Post paints a picture of South Africa’s transition to a resilient renewable network. Highlighting the need for an open electricity market, widespread distribution of generators, and strategic battery placement, Post illustrates how a far-flung grid can ensure uninterrupted power supply even in the face of unpredictable weather patterns. Drawing parallels with Australia’s renewable energy landscape, he emphasises the importance of redundancy and overcapacity to safeguard against potential failures, offering a roadmap for a sustainable energy future in South Africa.

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Part 4 of 4. By Ir. Wietze Post

How will SA transition to a renewable network?

Our current grid is not reliable. If it were, we would not have load shedding. Besides, our centralised generation fleet risks a simultaneous nationwide power failure. Before load shedding started, the consequences of failure would have been dire. Meanwhile all our gensets, solar, wind turbines, and batteries have mitigated the fallout.

Yet if Eskom tripped today, most of the grid would likely not restart. By the time part of the system is up again, thieves will have stolen large sections which Eskom will not replace.

Fortunately, in this bleak setting, SA Inc. is now better prepared for such a scenario. Gradually, load shedding has prepared some of us to fend for ourselves.

So, how do I expect SA to transition to a renewable network? And how will we always have power even if the wind doesn’t blow and the sun doesn’t shine?

There’s a way a renewable grid can run into a generation problem. For that to happen, more than half the country must be dark and windless. If there’s no wind for longer than a day in winter, we could have a power supply problem. The summer rainfall area is very unlikely to be windstill and see no sun for more than a day. In the Western Cape, it’s fairly common to see no sunlight during 6 consecutive days in winter. But to have no wind during those six days is highly unlikely. Yet should that occur, then the rest of the country will be able to supply energy.

So what do we need to put in place to make it work? I’ll explore that in this article. First, we already have an operational grid, so we have a lot of existing backup.

The government is splitting Eskom into three companies for generation, transmission, and distribution. They also intend to create an open electricity market. Laws and processes to make these changes have passed, or are passing, through Eskom and Parliament.

Read more: Wietze Post: Why 2024 will be another horrible loadshedding year

An open electricity market.

Electricity trading is already taking place between large generators and customers. Trading will expand to smaller parties. The relevance of the electricity market is that it gives price signals. The pricing at various times of the day or week, will show when there’s a shortage. The cost of electricity during shortages will rise. That will encourage South Africans to sell electricity at those times. You could keep your home battery charged and release your energy at a profitable time. Large operators will also look for profitable timeslots to release their energy.

It’s easier to manage demand with active market pricing. Thus it will be better to have an open electricity market. It will lead to solutions. The high prices during shortages will encourage suppliers to set up new capacity. Competing suppliers eventually put constant downward pressure on electricity prices.

As in other countries, energy traders will establish Virtual Power Plants (VPPs). We already have electricity companies who act as aggregators. Currently, they deal with large volumes. By 2025, they will both supply you with energy and sell your excess at the residential and business level. Via a control box in your switchboard, they optimize your electricity flow to and from the grid. On the grid side, they pump your energy into the grid when it’s most profitable for you (or them). VPPs can instantly pump megawatts from thousands of rooftops into the grid. You/they will earn from these transactions.

VPPs analyse your consumption patterns. They ensure there’s enough energy in your system when you need it. In other words, they won’t sell your energy moments before you need it yourself. A VPP can fill your battery when energy costs are minimal, free, or with consumption credit. With the consumption credit, you’re paid to accept energy. A battery owner can profit from arbitrage: you buy energy when it’s cheap and sell it later for a high price.

Thus, the most impactful change we need in South Africa is a wholesale electricity market. Trading electricity is a critical component of a resilient, reliable electricity supply system. Private suppliers will bring us cheap and reliable electricity.

Our current situation, with Nersa setting prices, is keeping electricity expensive.

For example, in Australia, the market manager operates on 5-minute intervals. Bidding for each future 5-minute slot starts weeks ahead. Generators bid packets with price and volume. The market manager ranks each by price, from lowest to highest price. The highest-priced energy packets lose out. Up to some price level is included in the energy sent out. Whatever the bid price is for that packet, sets the price for all suppliers in that 5-minute slot. To learn more about the Australian bidding system, follow these links:

Bidding, Dispatch & Pricing

Bidding and Dispatch Process

The NEM, bid stacks and five-minute settlement

A far-flung grid.

Another way to boost a resilient and renewable grid is to spread it far and wide. Grid operators must encourage all generators, large and small, to connect to the grid. Yet most distribution grid managers have regulations which chase suppliers away. That’s a big mistake.

South Africa stretches latitudinally (north-south) from 22°S to 35°S. We thus have shorter and longer days within SA every day. In summer, the Cape has longer days than Gauteng. In winter, it flips. Longer days mean solar power is worth more early in the morning and late afternoon.

Longitudinally SA spans from 17°E to 33°E. We have earlier sun on the East Coast than on the West. So East London regularly has a lot of early sun at 6 am, while it’s still dark in Alexander Bay. The reverse is true late in the day.

In the morning, East London could generate solar power for Alexander Bay. In the evening, Alexander Bay can return the favour. It would help us all if we worked together on a grid-sized scale. Solar panels on the East Coast should face east, while on the West Coast, they should face west.

Wind turbines must be widely distributed in various windy areas. In general, we want wind plant generation not to be correlated in time. They should generate power at different times of the day.

Read more: Wietze Post: Future of energy – refiners, smelters and other opportunities for renewables

We generally need overcapacity in each location. As we transition, the open electricity market will show the gaps. I expect we’ll find that about 50% overcapacity of annual energy generation will be enough. But we’ll probably never reach those goalposts. As energy becomes cheaper, the demand will expand. The goalposts will shift.

We should set up more transmission lines with neighbouring countries. They should similarly have widespread solar and wind resources within their country. The wider our connections, the less likely that some areas will be left in the dark.

Batteries are very important in a grid. They should be installed all over the place. We will likely eventually find that 2 to 4 hours of storage will be enough at most points of consumption. The batteries must be connected to the grid, and interact with it.

As a final tool, the grid manager can use demand management, as they do now.

Several times I’ve mentioned the need to install overcapacity. Usually, a good choice for clients is a plant capacity of 1½ to 2X the annual energy consumption. Always install a battery. That size plant usually earns itself back in 4 to 8 years, depending on the situation. The plant will operate for 25 to 30 years. It’s cheaper than buying energy from the local grid.

Example – Backup and redundancy in the Australian fleet.

Australia’s fleet has a high percentage of renewable generators. Some States operate solely on rooftop solar power for hours of a day. The State of South Australia often operates on 100% renewable power. Their backup is a 60MW gas plant. Besides that, they’re connected to the Eastern grid (NEM – National Electricity Market). The NEM still has several coal plants in operation. The NEM also absorbs South Australia’s daily excess renewable generation.

The redundancy in the renewable system comes from having many solar panels. They’re on residential roofs, business premises, and solar farms. Likewise, they have thousands of wind turbines. Nobody notices when a solar panel or wind turbine stops (except the operator).

Further redundancy comes from wind turbines and solar plants complementing each other. The sun shines during the day and the wind blows at night. The sun is powerful in summer, and the wind dominates in winter. South Africa is much the same.

Moreover, they have spinning machines (massive flywheels) to maintain grid stability. The Australians will not install more spinning machines. They’ve learnt that batteries with grid-forming inverters are better and cheaper. They’re busy building massive battery farms, as quickly as possible. The batteries are spread throughout the country.

A standard battery storage duration is materialising. That is 2 to 4 hours of storage for each generator’s rated output. Thus, each plant is dispatchable within defined ranges.

Besides the batteries, the far-flung grid is a key factor in buffering the system. Australia’s Eastern grid goes from Tasmania to far-northern Queensland. It’s narrower than South Africa. The wind is always blowing somewhere within the grid, and the sun is stronger in some parts of the country. Early sun in the east also feeds the grid to the west, and vice versa. As in South Africa.

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