The terrible energy crisis that is currently devastating South Africa, combined with the apparent absence of competent people involved, “dealing” with (one might even say “causing”) the crisis, has resulted in a lot of unnecessary confusion in this regard.
While obviously, a complete detailed discussion of large scale electricity generation systems, which reliably meet the demand of an entire country, includes a lot of detailed technicalities, which are beyond the scope of this article, the subject can be understood at a macro level, by just understanding a few key concepts.
The first concept to understand is that the total demand for electrical power must always instantaneously be exactly balanced by total electrical generation supply. Our electrical devices are driven by alternating current (AC), which is transmitted in the form of a very precisely controlled wave which has a single phase amplitude of 220V and a frequency of 50Hz (it’s a bit more complicated than that, because it’s actually a three phase wave, but it’s easier to understand a single phase wave, and that’s all you need to understand for the purposes of this article). If the demand for electrical energy does not exactly balance with available generated electricity, then that wave starts changing characteristics, the amplitude and/or the frequency of the wave will change. The grid and all the devices attached to it, can only tolerate relatively small changes to that wave, before physical damage starts occurring to equipment, including generating equipment, grid switchgear etc. For that reason, protection switches are incorporated throughout the grid, which will automatically disconnect, when they detect unacceptable deviations.
It is this protection system which can potentially cause a sudden nationwide black-out. For example, if a particular power station unexpectedly shuts down, then the demand immediately exceeds supply in those portions of the grid, and the AC wave form will start changing, if that deviation gets beyond what the protection systems are designed to tolerate, affected parts of the grid will automatically shut down, which may include other running power stations. Which in turn means an even greater deficit between supply and demand, resulting in other protection systems tripping, which can cause a rapid cascading catastrophic shutdown of the entire grid. Restarting power stations when there is no power available on the grid is called a “Black Start”, which most competent people agree is something which will take a long time to achieve, possibly a few weeks or even months. Clearly, such a situation needs to be avoided at all costs, if possible!
The video below explains what a Black Start is, very well.
For this reason when demand exceeds supply, portions of that demand which exceeds supply are shut down by those controlling the grid, to protect the grid equipment, which is called “load shedding”.
The fact that in South Africa, at present this happens day and night without end now, and the authorities seem to be on the verge of losing control over the amount of load shedding required at any point, should give you some idea of the severity of the crisis we face!
The other thing that is useful to understand is cable losses and transmission limitations. Essentially what this amounts to, is the fact that as you “pump” power into one side of a cable, depending on its length, resistance and the current flowing through the cable, a proportion of the power pumped into the cable is lost in the form of heat. This effect is mitigated when transmitting electrical energy long distances, by using very high voltage (the higher the voltage, the lower the current, for a given power level), but there is only so much that can be done. The result is that the power generated at the power station, is not what reaches the user a long way away. A consistent proportion of that power is lost along the length of the cable. In a fairly large country like South Africa, this is a significant problem, especially when power stations are failing all the time, which means that power suddenly needs to be diverted to users from potentially a long way away. It should further be noted that power distribution cables have hard limits to amount of power they can handle, so you cannot suddenly double the power being transmitted, if that would exceed the cable rating (not to mention maintenance issues, which further steadily degrade the power transmission limits of the cables).
If you understand those two issues, that is probably enough to understand why, while renewable energy generation is desirable in the long term, especially in South Africa blessed with our abundant sunshine, renewable energy is at best a side issue, when it comes to solving our current energy crisis.
The simplest way of justifying the statement that renewable energy is not really relevant to solving our current energy crisis, is to refer to the point that demand for electrical power must be instantaneously be met by supply. Renewable energy sources are by their very nature unreliable, and uncontrollable. We cannot control the sun, clouds, or wind! The power available from those sources, may, or may not, be available at any point in time, and may effectively vanish a few seconds later, as a cloud comes out over the solar installation, for example (clouds have a very large detrimental effect on the efficacy of solar panels). But the demand for energy must be instantaneously met with sufficient supply, at all times, to avoid load shedding! If you understand this principle, then it becomes clear why generation from non-renewable energy sources is actually the key to preventing load shedding.
It should be quite clear that you cannot reliably meet the deficit in supply from renewable energy sources, which may, or may not be available, at the exact point when supply is unable to meet demand, or when renewable energy generation may vanish a few seconds later.
In a stable, functional power grid, “base load” generation can be thought of supplying at least the “minimum” amount of power required each day. In a functional, stable grid, demand for power drops down to minimum level every 24 hours (usually at night) and peaks at other times in the day. Base load generation is a form of power generation which runs 24/7, ideally supplying at least up to the level of minimum demand required each day (think of a turbine that just runs steadily all the time, 24/7). Base load generation, by definition, reliably runs in all weather, at all times of the day and night. Renewable energy sources of wind and solar, simply do not meet this requirement (this statement should not be controversial).
Peak load generation is a potentially different form of energy generation from base load generation. Peak load generation is intended to meet the demand as that climbs above the minimum required, each day.
But unfortunately, renewable energy sources are not even suitable to be the primary method of meeting the peak load demand! (They have a secondary role play, but more on that further below).
Again, the point to remember is that supply must exactly meet demand instantaneously, at all times during the day and night. The need for the concept of peak load generation is that different forms of energy generation have different “ideal” ways of being run for lowest costs, equipment longevity and ease of control. Large coal and nuclear power stations tend to work best when they are run at relatively constant load (using the driving of a car as an analogy, coal and nuclear power stations work best when they are run at constant “speed”), so coal and nuclear are often used as sources of energy for base load generation. The purpose of the differentiation in concept between peak load vs base load generation is to try set the overall system up such that the large coal and nuclear stations run at relatively constant load each day supplying a steady “base load”, while other forms of generation which are more conducive to being spooled up rapidly and then shut down again (for example open cycle gas turbines) are better suited to supply additional power dynamically, when the demand peaks above what the base load stations are currently supplying. But again, the key thing to remember is that you have to exactly meet demand instantaneously as it rises each day. Which means that your peak load generation units need to be 100% reliable, available and instantaneously controllable, so that they can be driven to exactly meet demand as it it rises each day. You cannot hope that the sun will come out in time, or the wind will blow on demand, and worse, you cannot be at the complete mercy of a cloud coming out over a solar installation, or the wind suddenly dying.
Of course the wishful thinking is that using some form of energy storage, then renewable energy sources can be made to meet these energy generation requirements. The idea is the energy generated by renewable energy sources, when it is available, could be stored in some fashion, so that it can be later be supplied precisely at the instantaneous point of demand, thereby resolving the main problem with renewable energy, which is the unreliable nature of the weather. And there are in fact some established practical ways to do this, at least partly.
The most practical method of energy storage currently in use, are pump-storage schemes which use excess energy generated on the grid to pump water up to higher altitudes, and then when power is needed later, the water can be released to run back down through water turbines, to generate electricity. We have a small number of such systems in South Africa (Drakensberg, Palmiet and Ingula currently under construction), which are very valuable. We should do what we can to build more if possible (we have a very useful escarpment that runs almost right around the country, but unfortunately a very limited number of viable rivers). The available power from those storage units is currently 1400 MW from Drakensberg and Palmiet combined (assuming they are fully operational and not malfunctioning in any way), and when Ingula is available that will rise to 2732 MW. To put that into perspective, one of the older “six pack” coal power stations (Matla, Kriel, Tutuka etc) is each rated at 3600 MW (although those are all ageing and have been very badly treated, so those will not probably provide that full rating anymore). So the thing to remember is that the total power available from storage on the South African grid, at any time after the water has been pumped up the escarpment, is about half of one large coal power station.
It should be noted that those systems apparently have the capability to restart the grid in the event of a “Black Start” disaster (which essentially means the pump-storage station has enough power to supply at least one other power station to drive all it’s pumps etc, to restart that other power station, which can then be used to start other power stations in turn), that is, provided sufficient storage water had been pumped up and held in reserve at the top of the escarpment, before the grid collapsed! Which means that in the current crisis, it is actually crucial that that storage is not depleted to any large extent!
The core problem with energy storage is one of scale. Both in terms of the costs involved, as well as just sheer size. Storage systems tend to be at least as expensive (usually much more), as the electricity generation systems which supply them with energy – remember that storage systems do not generate electricity themselves, they need to be supplied with energy generated in some other form – so at the very least, users are paying at least twice, whenever energy is stored. But more than the cost, is the problem of the scale of storage. It is simply not financially feasible, or practical, to attempt to store the quantity of energy that will completely run a modern industrial country on a daily basis! But in order for renewable energy systems to be considered as the primary source of energy for a country, enormous amounts of energy storage becomes necessary! Unless you are talking about some small unindustrialised island nation, the amount of storage required is simply ludicrous in practical terms (as a rough rule of thumb, you need to store all the energy generated from renewable sources during the last 24 hrs, and have the ability to release that stored energy at high enough power levels, for that to become a reliable source of power, available to meet instantaneous demand, during the daily consumption cycle).
Which is why there is not one single example where the idealogical ideal of running a modern industrial country completely, or even mostly, on renewable energy has been shown to be successful! Not one! They ALL need the vast majority of their power generated from non-renewable energy sources!
In South Africa, given the scale of our current crisis, renewable energy is thus largely irrelevant! The fact that we have hours of load shedding, day and night means that we simply have a massive short fall between demand and supply, more than the authorities admit, given that the overall Eskom grid generation capacity has almost halved since the problem first became apparent in 2008. Eskom’s current reporting states they have a total available capacity of no more than 30 000 MW. But it should be remembered that the crisis started in 2008, when they had about 48 000 MW. Which means that simple arithmetic indicates we need at least an additional 18 000 MW, just to revert back to the position we were in when the crisis started. And that does not account for any sort of economic growth. Or replacement of ageing and damaged units.
It is very clear that at a level of 30 000 MW total available generation capacity, all generation units are being run into the ground, without any opportunity to do sufficient maintenance, or any spare reserves to handle break downs, or anything else, while still only supplying significantly less than current depressed demand from a crippled economy. The current non stop, and steadily worsening, load shedding, is unavoidable evidence of that state of affairs.
It is thus not controversial to state that the only way of solving that problem, is the urgent large scale building of power stations which are based on reliable, controllable sources of energy, starting with base load generation units, so that we at least have enough power to meet the minimum power demand every day (the fact that we have load shedding in the middle of the night tells you we cannot even do that). Once we have enough base load generation capacity, then obviously the focus should switch to increasing peak load generation capacity, as well as replacing aged and damaged existing units.
A rough thumb suck estimate of what is required to replace existing ageing and broken power stations, as well as add critically needed additional capacity, is we urgently need at least 36 000 MW additional generation capacity, which is reliable and available to supply instantaneous demand night or day, to properly get back on track – which is equivalent to ten large coal or nuclear power stations! Building of those should already be happening, right now, but sadly none are even planned! What an amazing state of affairs, and a complete and utter failure by all those imbeciles involved! They should all hang their heads in shame!
Renewable energy generation is not really an option that will be of any use to solve the immediate problem. Renewable energy should be seen as a bonus we can perhaps think about later, once we have a functional stable grid again, but right now in terms of solving the current crisis, it’s largely irrelevant!
Renewable energy has an obvious role to play as a “bonus” peak load power source. When the sun is shining, and/or the wind is blowing, well then renewable sources can be used preferentially to supply power as demand rises above base load. But if a cloud comes out, or the wind stops blowing, then non-renewable peak load power generation sources need to be available, to kick in instantaneously and take over.
Another obvious role for renewable energy would be to drive the energy storage systems when the sun is shining or the wind is blowing, for example pumping water up the escarpment in the pump storage schemes. But again this is a bonus function that cannot be relied upon exclusively, and in all cases, the ability to instantaneously be able to fall back on more reliable energy sources must be available, where that power is needed to meet instantaneous demand.
So renewable energy has a definite role to play, but only once we have a stable functional grid, which can completely meet instantaneous demand at any time, day or night, from non-renewable energy sources.