Managing Demand in winter – What Eskom does?

South Africa has a ‘peak’ electricity demand profile in winter. The winter demand shows a rapid increase in electricity usage of approximately 4000MW, predominantly due to increased use of space heating, geysers, pool pumps and cooking appliances.

The electricity demand reaches a maximum during the evening, which is referred to as the evening peak between 5pm to 9pm. The greatest increase and risk period of load shedding in winter is between 5:30pm to 6:30pm.

The winter demand shows a rapid increase in electricity usage of approximately 4000MW, predominantly due to increased use of space heating, geysers, pool pumps and cooking appliances.

To maintain supply capacity when faced with winter demand, Eskom has adjusted its maintenance schedule so that additional capacity becomes available in winter by doing less maintenance in this period. However, scheduled maintenance must continue to be pursued for long-term plant health.

During this time key industrial customers assist by reducing their demand over the peak.

Every year, the high level of illegal connections causes significant load increase and subsequent overloading of localised networks. To counter illegal connections and prevent meter tampering, Eskom has embarked on an intense national partnership programme called Operation Khanyisa.

Operation Khanyisa promotes the legal, safe and efficient use of electricity in South Africa. This national partnership campaign has various stakeholders, including Business; Eskom; Government; Civil Society; the Media; and ordinary South Africans.

You can help sustain the capacity of our national energy grid by preventing, detecting and reporting electricity theft. Be an Operation Khanyisa ambassador. To report electricity theft anonymously you can either send a detailed SMS to 32211, or call the Call Centre, or use the MyEskom Customer App

On the Supply side, Eskom also purchases power from cross-border countries, mostly Mozambique, local independent power producers, and from municipal generation to increase supply capacity and reduce the use of expensive Open-cycle Gas Turbine generation.

But despite these measures to balance supply and demand, our national electricity system continues to remain tight and vulnerable, meaning that any shift on the power system could result in a shortage of supply.

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Managing demand in winter – What you can do?

It remains crucial for all Eskom customers to ‘Beat the Peak’ from 5pm to 9pm in winter by maintaining or achieving 10% electricity savings. As this occurs at night, residential customers have the power to make the biggest difference.

Let’s make the call to make a difference.
Let’s make the call to use less electricity today.

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Managing demand in summer – What you can do?

South Africa has a flat profile or Table Mountain profile in summer, which means that Demand is high for the entire day, until 9pm, predominantly due to the increased usage of air-conditioners, geysers and pool pumps.

In addition, planned generation maintenance increases significantly in summer, and we have less capacity to supply demand. This means that the risk of load shedding remains high throughout the day in summer until 10pm; and in the event of unplanned activities within the electricity supply chain. This makes it important for consumers to continue to reduce consumption during summer too and remember the call to “Live Lightly”.

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What are the impacts on supply capacity?

The stable supply of electricity is affected by many variables which can impact on our capacity to supply. They include, but are not limited to, extreme weather conditions, issues on our transmission lines, quality and availability of raw materials or primary energy such as coal, water, wind, solar as well as unforeseen faults from Cahora Bassa imports from Mozambique, and unplanned failure on our plant such as, fire damage or mechanical problems.

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What you can do to limit the need for load shedding?

In the event of significant incidents on the power system, the probability of load shedding increases, but it remains impossible to predict accurately when we will have to reduce load. It’s no longer simply an Eskom challenge, but a national challenge and each of us has a part to play in minimising the possibility and magnitude of load shedding.

Make a positive difference by reducing your electricity usage at home and at the office, and encourage your friends and family to do the same:

  1. Delay switching on lights and appliances until after the peak periods whenever possible
  2. Switch off your pool pump and geyser, and never run both at the same time or simultaneously with other large electrical equipment
  3. Most important: remember the golden rule, Switch off what you don’t need
  4. Adjust air-conditioners to 23 degree Celsius
  5. Retrofit your homes and businesses with energy efficient lighting

Saving electricity not only reduces pressure on the grid, but also reduces your electricity bill and South Africa’s carbon emissions.

Let’s do it together!
Let’s make the call to make a difference. Let’s make the call to use less electricity today!

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Wet Coal

Wet coal is one of the variables which can impact on our capacity to supply. In South Africa, coal powered stations comprise over 80% of our primary energy resources, due to our abundant coal supply and that it’s a relatively safe and cost effective way to generate electricity.

But persistent wet-weather conditions can cause supply challenges that impact on available capacity. To understand how wet coal impacts on supply it’s important first to understand how coal is used in power stations. This is described in the next section, “Coal and the steam generating process”.

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Coal and the steam generating process

The collieries which supply Eskom are contractually obliged to ensure that their coal meets quality requirements including coal size, its moisture content, abrasiveness and combustibility.

It is delivered to three kinds of stockpile – the “live stockpile”, “seasonal stockpile”, and the “strategic” stockpile. The coal on the strategic stockpile is mainly coarse material which does not easily absorb moisture.

However, the stockyards that store Eskom’s reserve coal supply are spread over areas of up to several square kilometres and cannot be protected against severe weather conditions, although we do have contingency measures in place for their management.

Coal is fed from the stockpiles to storage bunkers at the power station on conveyor belts and from there is fed into pulverising mills which grind it into dust as fine as cake flour. Hot air, to dry it, blasts the powdered coal through coal burners to the boiler furnace where it burns like a gas – and the heat from the burning coal causes demineralised water contained in tubes to convert to steam at high temperature and pressure.

This superheated steam passes to the turbines where it expands and releases its energy causing the turbines to spin – and generate electricity.

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The effect of excessive water on the coal

Though coal normally contains both inherent as well as surface moisture, it is clear that excessively wet coal has a limiting effect on the effective generation of electricity.

It can become a muddy sludge that creates blockages at transfer chutes which shift coal from one conveyor to another – and the excessive weight of wet coal can cause conveyors to break.

Wet pulverized coal can also cause clogging of milling plants and associated pipe works, which leads to mills being shut down to be cleared by hand, meaning boilers cannot receive fuel so must be shut down too.

Coal should enter a boiler furnace at the optimum temperature of 900C to ensure that combustion takes place in the shortest possible time. When it’s wet, more hot primary air is required to dry it before it can get to the boiler with the risk of the coal igniting and causing fire in the mills.

Eskom is dealing with the wet coal challenge and doing all it can to prevent stoppages in the future, including more effective stockpile management, ensuring adequate availability of coarse coal for excessively wet conditions, researching and improving the operations of boilers, and researching the properties of coal itself, to ensure that coal supplied by collieries is up to the standards required.

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Transmission Problems

Transmission problems can impact on our capacity to supply electricity due to the following variables:

  1. Imports. Eskom imports 1400MW of electricity from Cahorra Bassa in Mozambique. In summer the seasonal floods pose a risk to this supply option because the transmission lines can be disrupted and only repaired once the flood water has receded. The loss of this import has a similar impact to losing a generating unit from a power station.
  2. Fire - When there is a grass fire under a power line, the heavy smoke from the fire rises and spans the gap between the power line and the earth wire located above it. The smoke plume is highly conductive due to its carbon content and provides a perfect medium for fault current to flow from the power line to the earth wire. As soon as this happens, the protection systems open the breakers, disconnecting the power line and the supply to customers. Because a veld fire can last for at least an hour before it is put out by emergency services, it usually means that consumers experience several hours of interrupted supply.
  3. Theft – Theft of metal parts from the transmission towers as well as vandalism affects transmission and the ripple effect means that everyone suffers the consequences. It leads to higher prices, power outages causing production down-time, traffic congestion, household inconvenience and appliance damage – and a constrained power grid that inhibits economic growth and job creation.
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Planned Maintenance

80% of our coal-fired power stations have reached or are past their mid-life cycle. To understand how planned maintenance can impact on our capacity to supply, think of a power plant as a motor vehicle like a car or a truck... It’s used every day, but once a year, or after having done a certain amount of mileage, it has to be taken for a service that includes things like checking that all the moving parts are still in good condition; applying lubricants between moving parts; replacing broken parts, or parts at risk of breaking soon … Like maintaining your car, maintenance on a power station cannot be compromised. If we do, this could have serious consequences which could place the entire grid at risk.

But power plants cannot be taken to the mechanic. Our engineers must go to the power plants and, due to the sheer size and number of the parts; it takes quite a long time for the full maintenance to be completed. This means we have many units offline during the year, with a greater percentage in summer and as a result have less generating capacity, and cannot supply as much as we do during winter. The result is that demand outstrips the available supply a lot quicker during summer, placing us at risk of load shedding every hour of a summer’s day, where in winter it is basically only during the peak demand period in the evening.

Let’s make the call to make a difference.
Let’s make the call to use less electricity today.

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When the power goes off, is it always load shedding?

When the power goes off, it is sometimes difficult for a customer to know whether the cause is load shedding, or another reason.

There are three basic reasons why the power could go off – Faults on the networks, Planned Maintenance of the networks, and Load Shedding. From an Eskom perspective, all are managed differently, but the impact on the customers is similar – the power goes off.

The main difference is that when a network fault occurs, it is unplanned and unexpected. Eskom has to respond to the event, either after reports from customers, or where our telecontrol systems tell us that the power has gone off.

Planned maintenance of the networks, as the name implies, is planned and prearranged, and customers are notified in advance when their supplies will be disrupted so that we can perform maintenance. The impact on customers is isolated to the specific area or network where the work is to be done. Planned outages vary in duration, depending on the amount of work to be done.

By contrast, load shedding impacts all customers in rotation, according to a plan (the schedule) and for a consistent period of time.

In Eskom we need to manage all three processes, i.e. firstly by responding to and repairing faults that occur on a random basis, secondly the deliberate, planned process of managing planned outrages to do essential maintenance work on specific networks, and thirdly, the deliberate, planned process of load shedding - switching off power in rotation across the whole country to protect the grid from collapse.

It is important for customers to try to distinguish between the 3 types of power outages.

If you are scheduled for a load shedding period when the power goes off, you can reasonably assume that the reason is indeed load shedding.

However, if the power outage persists for longer than the published switch-on time, it should be treated as a fault and reported.

Also, if the power goes off and –

  1. you have not been informed in advance of a planned maintenance in your area,
  2. if you are aware from the media that South Africa is not in load shedding, or
  3. if you know we are load shedding but your power has gone off at the wrong time according to your schedule, then the best advice is to assume that it is a fault and report it to Eskom (if you are an Eskom customer) or to your municipality (for customers of metros / municipalities).
Eskom (or your municipality) will then investigate as soon as possible, so that you would not have the unnecessary delay if you waited for several hours and only then called to report the fault.

Customers are strongly advised always to check the load shedding schedules, and any outage that does not coincide with these MUST be reported as a fault. Do NOT assume that it is load shedding if the power is off and the schedule does not say that it should be. Eskom staff and municipal staff must ALWAYS assume it is a fault unless it coincides with the published load shedding schedules, or with a notified planned outage.

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What will be affected by power outages?

The following will not be available when the electricity supply to your home is switched off:

  • Electric geyser and electrically heated water supplies
  • Gas hot water systems that rely on mains power to control the system or ignite the gas
  • Electric appliances such as stoves, kettles, toasters, microwave ovens, refrigerators, dish washers, washing machines and tumble dryers
  • Electric lights
  • TV and hi-fi equipment
  • Cordless phones, fax machines and answering machines that run on electricity
  • Electrically motorised security gates and garage doors (those with battery backup should have sufficient capacity to operate a few times during load shedding)
  • Pool pumps
  • Personal computers
  • Electric air conditioning
  • Mains powered electric clocks and alarm clocks (without backup batteries)
  • Household electric pumps for water features, irrigation or plumbing systems
  • Automatic electronic control systems and time clocks

What will usually not be affected by power outages?

  • Security systems that have battery backup (some may trigger an alarm because of the power interruption)
  • Other electronic systems and devices with battery backup or UPS support
  • Landline Telephones that do not rely on mains electricity
  • Cell phones (provided they are charged)
  • Laptops and tablets (provided they are charged)
  • Battery operated toys and appliances

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How can I prepare for load shedding?

  • Keep aware of the state of the power system and whether the country is likely to load shed, or if it is load shedding, and if so, in what stage.
  • Keep checking your load shedding schedule and plan on the assumption that load shedding WILL take place
  • Think about communication: ensure that your cell phone / laptop / tablet is always fully charged when power is available.
  • Think about transport: ensure that your vehicle always has fuel in the tank because many petrol stations cannot pump fuel during power outages.
  • Think about cash: ensure that you have enough cash because ATMs cannot operate without electricity.
  • Think about access, security and safety:
    • Make sure that the backup batteries in your electrically operated gates, garage doors and security systems are in good condition to last through periods of load shedding.
    • Keep temporary lighting readily available, e.g. battery-powered torches, gas lamps and candles. Make sure you put these items in places where they will be easy to find in the dark. Modern LED lamps and torches are recommended as they are bright, long lasting and avoid the fire hazard of gas lamps and candles.
    • Keep battery-operated equipment charged (e.g. cell phones, torches, laptops, tablets, radios).
  • Think about keeping things cool and heating them up:
    • Boil water and keep it in thermos flasks for hot drinks for times when the power is scheduled to be switched off.
    • Use an insulating cover on teapots and other pots and pans to keep drinks hot, and meals warm.
    • Prepare meals beforehand in readiness for periods when there will be power cuts.
    • Obtain a small stand-by bottled LP gas heating ring for essential cooking and to boil water for hot beverages.
    • Keep adequate stocks of essential foodstuffs.
    • Keep refrigerator and freezer doors closed. A power outage lasting four hours should not cause food spoilage, and a freezer should keep frozen food safe for at least a day. It is a good idea to have alternative snacks available that do not need refrigeration.
    • Most medication requiring refrigeration can be kept in a closed fridge for several hours without spoiling. (To be sure about this, check with your doctor or pharmacist.)
    • Fill plastic containers with water (still leaving some space inside each container for expansion during freezing) in a deep freeze or the freezer compartment of your fridge. This frozen bottled water will help keep food cold during a power outage.
  • If circumstances dictate that you cannot be without power even during periods of load shedding, you may want to consider investing in a petrol, diesel or gas-powered generator, or a UPS system designed to power those pieces of equipment and appliances that you consider essential.

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Can load shedding damage my appliances? What should I do to prevent this?

If the power goes off, it is safer to turn off (or even better, disconnect) any electrical appliances that you were using. Keep one light switched on so that you can see when the power returns. Clearly mark on/off switches with a piece of masking tape if necessary.

When the power comes back on, it may do so with a momentary surge, which may damage electronically controlled appliances such as computers, television sets, VCRs, DVDs, etc.

Remember to reset the time-control clocks on cooking ovens, pool pumps, geysers and other automatically controlled appliances, unless these are battery operated.

Also remember that householders are responsible for all electricity usage and appliances in their homes.

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What precautions should I take in case load shedding happens while I am away?

Switch off and disconnect all non-essential appliances such as computers, coffee machines, television sets and entertainment consoles.

Switch off your geyser while away so that you avoid the cost of heating water unnecessarily. (Remember to switch it on as soon as you return, install a geyser timer or ask a neighbour to switch it on for you a few hours before you get home.)

Leave appropriate lights on for security purposes (preferably operated on timers, not left on all day and night).

Replace conventional outdoor lights with motion sensor lamps for security. They use less electricity because they only activate when the sensor is triggered.

Switch to solar-powered garden lights which use free energy from the sun.

Leave your refrigerators and freezers as empty as possible

Make sure that the backup batteries in your electrically operated gates, garage doors and security systems (alarms and electric fences) are in good condition.

Fix leaky taps. Allowing water, especially hot water, to drip down the drain wastes both water and electricity.

Set your pool pump to operate for a maximum of four hours a day, which is ample to keep the pool clean while it is not being used.

Make sure your pool pump is set so that it does not operate in the period from 5 to 9 pm, which is when the peak electricity demand for South Africa occurs.

Leave a key with neighbours and ask them to check your property regularly, and to make sure that the main switch or earth leakage have not tripped (i.e. all essential appliances such as security systems, fridges and freezers are still functioning).

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What about customers with special needs?

Customers with special needs, such as medical support equipment (ventilators, dialysis machines, etc.) should consult their medical practitioner about what special arrangements can be made. For example, it may be possible to obtain a battery backup unit for medical equipment, or to get additional oxygen cylinders as a backup.

It is generally impossible to leave the power on for individual customers when whole networks and areas are switched off, so customers with medical needs must please take extra precautions to ensure that their needs are provided for, and that they are adequately prepared to deal with power cuts.

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Infographics for Loadshedding:

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