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The electrically literate may find this somewhat simplified article redundant; or possibly amusing. They should check out Wikipedia for any gaps in their knowledge.
But I hope this will help those for whom Wikipedia is a bit too complicated and/or detailed.
All cartoons from The New Yorker - 1925 to 2004
Think of water in a hosepipe
Electricity is a means of transporting energy from a source, like the wind, to a device you use to exploit that energy, like your electric toothbrush.
The usual way of explaining electricity is to use the simile of the flow of water in a pipe (a current of water). We are all familiar with a hose pipe. Its pressure is analogous to the voltage; and the flow of water is analogous to the current.
The author - almost two - learning about currents and voltage
The work that can be done in an hour, for example if you use the jet to spin a bicycle wheel or push leaves along a path, is the pressure (like Volts) times the current (like Amps) for an hour.
You won’t be able to squirt the water from your hose far if there is no pressure or if there is no water. You need both. If the pressure falls the water ceases to flow.
It’s the same with a stream (current) of electricity making its way down a conductor; for example a wire. The electrical force acting on an electrical current provides the power to do work.
Most quantities in modern physics are named after an early natural philosopher or inventor. If we had let tradition do it, each would probably be related by some strange number, like the number of feet in a mile; or pounds in a ton. But most new physical values use the decimal system (the rationalised MKS or SI units: meter, kilogram, second).
A Watt is a measure of Power; the instantaneous capacity to do work; named after James Watt.
Under this system we define one Watt as equal to one Volt (electrical force) multiplied by one Ampere (current); or Amp for short. Read More...
Using this simple relationship you can easily calculate that 1000 Watts of power (one kilowatt) can be carried by a current of 4.17 amps at 240 volts (240 x 4.17 = 1000)
But the same power requires only 0.002 amps at 500,000 volts (0.002 x 500,000 = 1000). So when you turn on an electric kettle or toaster it will draw around 4 amps in your home at 240V but only 0.002 amps in the very high voltage grid to bring it from the generator in the power station.
Power exerted for a period of time is called Energy. Physicists measure energy in Joules (1 J= 1Watt acting for 1 second). But to get to a smaller working number electricity companies like to measure energy in kilowatt hours (1 kWh = 3,600 kJ = a thousand Watts acting for the seconds in one hour)
When your bill comes, you get charged for the Energy, the number of kWh* you used, not Power (kW).
*Terminology: 1000 Wh = 1 killowatt hour (kWh); 1000 kWh=1 megawatt hour (MWh); 1000 MWh = 1 gigawat hour (GWH), 1000 GWH = 1 terawatt hour (TWh).
Pushing a current through a conductor requires energy. The difficulty in doing this is called resistance; and is measured in Ohms. For each Ohm of resistance an electromotive force of 1 Volt is required to cause a current of one Amp to flow. In other words Resistance = Voltage (drop across the conductor) divided by the current (Amps) in the conductor. This is called Ohms law and is obvious, a priori, from the definitions of these quantities.
The important things to know about conductors are that: resistance varies depending on the material that the conductor is made from; and the electrical energy used to overcome resistance becomes heat. Read More...
Electrical conductors get hot depending on the current flow; and the heat generated goes up exponentially as the current increases in a wire.
Suppose the lead to a power board in your kitchen is carrying 2 amps and consuming 5 Watts per metre as heat. This is so small you don’t even notice the lead getting warm. If you add a few more appliances taking the total to 10 amps the heat in the lead will jump, not to 25 watts per metre as you might expect (5x5), but all the way up to 125 watts per metre; at which point it will probably burst into flames. This is why commercial power boards have a big safety margin with wires around twice as heavy as those in this example; so there is only moderate heating even at 15 amps.
Resistance falls as conductors get fatter, in proportion to cross-sectional area. This is obvious because two identical conductors (or water pipes) side-by-side carry twice the current of one.
You may have noticed that the cord to some high current appliances, like heaters, kettles and vacuum cleaners, gets warm. To avoid heating the wires in your house too much and possibly burning it down, properly installed wiring has current ratings well above a safe limit; electricians are careful that all strands of a cable are terminated; and the current is limited by fuses and other kinds of current breakers.
We often want some wires in home appliances to get hot: electric heaters, kettles, toasters, and so on work on this principle; an incandescent light bulb generates so much heat that the filament glows white hot; a fuse wire melts if the current gets above a certain limit.
But unless you want a bit of extra warmth, heating wiring in buildings is wasteful and a fire risk. It is particularly wasteful in the street or in wires running for miles in the country. Many millions of kilowatt hours of electricity can be lost heating the countryside.
The actual losses are equivalent to approximately 10 percent of the total electricity transported between power stations and market customers. In long links and in those carrying high currents, from time to time, the losses can be much higher than this.
What is electricity - really?
Above I invited you to think of electricity as a fluid of electricity running through a conductor that acts like a pipe.
According to our present conceptual model electricity is due to the movement of electrons in a conductor. Electrons are negatively charged fermions (particles that make up an atom) that are generally happy to hang around an atom to balance the positive charge of its nucleus. Read More...
Electrons are envisaged as milling around in the general vicinity but often at a great distance, relative to the size of the nucleus, like planets around the sun. The outer electrons define the physical size of an atom. Contrary to some pictures you might have seen they do not orbit elliptically like planets but occupy a space determined by their wave function and energy state. They are happy bouncing around in this space unless something, like a photon of light or heat, encourages them to jump to another energy level.
Conductors and insulators
Some elements, like the metals, bond to each other in such a way that outer electrons can pass energy on to the next; or perhaps get shared in one big cloud.
By stimulating electrons to move we can make them carry energy along a conductor but this is more like the baton in a relay or an ‘Indian wave’ in a stadium than a flow of water. Each one in the chain just gives the next one in line a ‘shove’; pass it on. The ‘shove’ goes down the conductor and after passing-on the ‘shove’ each electron continues to hang about as before.
On the other hand non-metals tend to form molecules in which the electrons are not free to pass energy on. A material in which no current can flow we call an insulator. Read More...
Whether an atom is a metal or not depends on the number of protons in the nucleus. After disregarding the first two (hydrogen and helium), elements can be lined up nicely by their proton count (roughly half their atomic weight) in a table: the first row pair of 8 then 18 then 32 columns wide; so that every 8th, 18th then 32nd is similar in properties; for example: a noble gas, a halogen or an alkali.
This pattern was observed by chemists before it was explained. Once recognised it allowed chemists to see the gaps and find the missing elements. This regular pattern of repetition is called the periodic table of the elements.
Quantum mechanics now provides a model predicting/describing/explaining this observed behaviour.
Metals are not the only conductors. Some non-metals like carbon have one form, graphite, which is a good conductor and another, diamond, which is a good insulator.
Selenium, another non-metal, has semiconducting properties and was widely used before silicone in solid state rectifiers. As a schoolboy I built several battery chargers and power supplies employing selenium rectifiers which were then easily obtained from disposals stores.
Black phosphorous is another non-metallic conductor.
If an electron is stripped from and atom (or it acquires extra electron) it is said to be ionised and if the whole atom is mobile; for example in a fluid (gas or liquid) the whole atom can act as a transport for electrons or of positive charge (an excess of protons).
For example, salt water is a good conductor and even the earth (rocks and soil) can be used as the return conductor in a circuit.
As kids we used this in our one-wire telephone to friends in neighbouring houses.
AC and DC
When the current is in one direction only we call it direct current DC; and when the ‘shoves’ are in one direction and then the other, back and forth like a swing, we call it alternating current or AC.
Both carry usable energy but AC makes less efficient use of the conductor as there are two points each cycle when nothing is happening and high currents, and greater loss, happens at the peaks.
So how do we make electrical currents flow?
If we want to carry energy along a conductor we need to stimulate electrons to start passing it on as one shove to the next; in the desired direction.
By far the most common way of doing this is by passing a conductive wire through a magnetic field; or a passing a magnetic field across a wire. This gives the electrons a shove along the axis of the wire. The field has to be moving relative to the wire. A stationary field like the Earth's magnetic field requires the wire to be moving.
You have probably tried to push the matching poles of two magnets together. In the same way a magnet pushes the electrons along a wire. This push-back becomes stronger if we resist the current by putting it to use in a circuit; for example to heat a wire or make another magnet move in a motor.
It is quite easy to make a coil of wire into an electro-magnet. This can be as strong as most magnets you might have played with.
This is how the alternator in your car makes electricity to charge the battery. It has a whole bunch of wires (usually end to end in a coil) and every turn of the shaft rotates these wires through a magnetic field. The effort required to do this is in direct relation to the energy required to charge the battery.
Most electrical generators work on this simple principle. It very efficiently turns mechanical energy into electricity; or back again to mechanical energy in an electric motor. Read More...
It's quite easy (as a child) to make one yourself and run it with a toy 'donkey engine' to light a light bulb.
3 Phase Alternator Operation (the rotating bit here can be a permanent magnet)
Water pressure can be used to rotate the shaft of an alternator (an AC generator) below a dam.
Steam is used to drive a turbo-alternator in a coal, gas, geothermal or nuclear power-station. Petrol oil or gas engines; or wind can be used to rotate the shaft of an alternator; and tides, currents and waves drive machines to do the same thing.
There are many images of various types of power generation elsewhere on this website.
Other ways of making currents
But we can also get currents moving in other, harder to understand, ways.
A photovoltaic solar cell exploits the ability of semiconductors to allow electrons to move in one direction only. If these are then excited by energy from photons (a type of boson), they get pumped along specially designed current paths in one direction only.
This is oversimplifying a phenomenon requiring knowledge of depletion layers, electron tunnelling, and even quantum mechanics for a full explanation. You need to know a bit about semiconductors. Read More...
Photovoltaic solar cells are still in development and a lot of work is going into improving their conversion efficiency and bringing down their cost.
It is hoped that someday they will be able to provide up to 20% of our energy requirements; possibly more if we can find an economical way of storing energy from day to night and season to season.
Thermocouples employ the flow of heat in a metal from a hot area to a cold one called the Seebeck effect. Electrons in the hotter areas are more energetic than in the cooler part causing a voltage gradient. Electrons flow at different rates in different metals so if two dissimilar metals are in electrical contact near the source of heat the net difference in voltage gradient (in response to the same heat gradient) will result in a current flowing from one metal to the other.
Thus some of the heat flowing from hot to cold is converted to electricity. This is what is helping to power the recent Mars Lander: Curiosity. It uses decaying plutonium to provide the heat to thermocouples. These provide base load energy at night when Mars is very cold. Curiosity also has solar panels.
Despite maximising the differential by using very different metal alloys, the conversion efficiency of heat to electricity is still relatively poor, compared to mechanical conversion. But efficiency is a secondary issue if the energy source is plentiful and free. The biggest issue is the equipment cost: how much energy is converted per dollar of device?
Efficiency does have an impact on physical size. This may be important is space is limited. This becomes evident when we calculate how big an area of solar panels some industries might need.
For example an aluminium smelter would need many square kilometres of solar panels (around 30 million present generation commercial panels) to supply the electricity required to separate the metal from alumina. This would not be feasible anyway as the aluminium pots can't be shut-down overnight or on dull days.
As already mentioned ions are negatively or positively charged atoms. These can be caused to flow by chemical and sometimes physical means.
For example, changing ion concentrations across a barrier, through which only some ions can pass (osmosis), is used very widely in nature. This happens in our body cells to produce nerve signals and; in the case of some eels, produces thousands of volts. Read More...
Why are there different voltages and currents?
As we have already seen, the same energy can be transmitted at a lower current (and heat loss) by increasing the voltage. You might wonder why we don’t just use very high voltages everywhere.
The problem with very high voltages is that they will force high energy carrying currents to flow through even relatively poor conductors; like wet or dirty insulators; trees; or people. Even damp sea air or ionised air from lightening can be a risk. High voltage lines have also been blamed for bush-fires in Australia.
Thousands of people receive electric shocks at 240v each year without harm; but this voltage is right on the margin. Unless you can spring away you will probably be seriously injured. Annually around 150 are killed in Australia and another 1,000 hospitalised. Even 110v will kill you in the bath (popular in movies); or barefoot on a wet tiled floor.
We are partially electrical machines ourselves and excessive currents can seriously damage our nervous system; or in the extreme cook us.
The problem with lower, safer voltages is that to stop too much energy being wasted as unwanted heat; or fire; wires need to be increasingly thick and expensive.
So to make wires carry more current without excessive heating we need either: to increase their diameter; or to use a more conductive material.
Gold and silver are very good conductors but too expensive to use except on a tiny scale in electronics.
Copper is also quite good, as is aluminium, but iron and steel; used quite extensively in hard wearing situations, like railways, are not as good.
Aluminium is widely used with many strands wrapped around a strong steel core for very high voltage lines; due to its light weight and competitive cost.
But more expensive copper can carry the same current through a thinner wire and is more corrosion resistant. There is a trade-off to decide the best option for a particular situation.
Advantages of AC
As previously mentioned DC makes better use of a conductor and the current is uninterrupted and less heat is generated at a given current and wire diameter.
But unlike direct current (DC), alternating current (AC) in which the direction of the current reverses and then returns 50 or 60 times a second (frequency is measured in Hertz: 1 Hz = 1 cycle per second), can be used to induce an alternating magnetic field in a ‘transformer‘.
The 'mains' frequency is arbitrary from the early days. Like railway line gauges, almost any could have been chosen; within some practical limits. Europe went metric with 50 Hz; the US chose 60 Hz to synchronise with electric clocks.
A transformer enables one voltage and current combination to be converted to another with very little loss; although there is always a small additional heat penalty due to magnetic hysteresis; don't wory about this unless you are interested - Read More....
Transformers are used in their thousands all over the electricity grid. These allow engineers to supply low-voltage-high-current local distribution networks with higher-voltage-lower-current power lines to minimise losses while maximising community safety.
So around your street the domestic supply lines run at 240/415volts. These local lines are supplied through transformers at regular with intervals.
You have no doubt noticed those metal covered pits in your shopping village pavement; those green humming cabinets in some streets and those grey boxes with wires going in and out up power poles. In Australia these supply the four low voltage wires (3 phases and neutral) from the local three wire intermediate voltage grid; that typically runs at 11,000 volts (and can definitely kill you).
These lines, in turn, run to an intermediate sub-station transformer supplied by a higher voltage. These substations are linked to an even larger main substation supplied by the transmission grid; running at voltages of up to half a million volts.
In low voltage distribution most energy is lost heating the conductors (wires) and transformers but in high voltage transmission energy is also lost due to arcing (leakage) across insulators.
AC transmission is used because of the advantages transformers provide. But AC leaks some energy due to low frequency electromagnetic radiation, inducing currents in other nearby metals and other conductors that produce warming. Some cooking tops use this induction principle to heat metal pans without a heating element.
The ability to transfer energy to another circuit (or conductor) like this; by means of an induced fluctuating magnetic field is called 'induction'. The unit of inductance is the 'Henry' (H); again named after an early researcher. The inductance of a circuit is one Henry if a current changing at the rate of one ampere per second results in a change in electromotive force one volt (H=Vs/A).
Instead of producing heat in the conductor, induction produces a varying magnetic field; that can be 'stolen' by another circuit to make a current flow. The power transferred to the 'secondary' circuit, and thus lost to the 'primary' circuit, is like another form of resistance that applies to AC; in addition to normal DC resistance.
The overall power lost or 'AC resistance' is called 'impedance'; the measure of the opposition that a circuit presents to the passage of a current when a voltage is applied. Impedance is much more difficult to calculate than simple 'resistance', as it depends on the nature of the oscillating current and voltage in an AC system; including the frequency and the 'waveform'.
In large grids impedance can cause significant losses.
Because current and voltage can get out of synchronisation (phase angle); current can be rising as voltage is falling causing additional heating in wires and transformers. The 'power factor' indicates the degree to which power is lost when the current gets out of phase with voltage and/or the waveform becomes distorted. A power factor of 1 represents no loss. If the power factor is degraded (is less than 1) a lot energy can get lost.
Over long distances all these factors can result in losses so high that the cost of energy actually transmitted becomes uneconomic.
Obviously losing 50% in transmission and distribution, before the electrical energy reaches a consumer's meter doubles the effective price of that energy to the retailer or to the wholesale market; losing 75% is catastrophic.
Some appliances like large motors or large banks of fluorescent lighting cause the power factor of the grid to become degraded. It is illegal to connect these to the electricity supply unless they have additional components to compensate/correct for this impact.
When I was a boy a popular brand of light bulb advertised on the trains that: 'Mazda Lamps use only pure electricity'. It was a joke in our family (my Uncle was also an electrical engineer) that this meant they seldom worked, as the waveform and phase angle are hardly ever 'pure'. Obviously some ignorant advertising executive was responsible for that - except that I still remember it!
But on second thoughts maybe it was 'O for an Osram'...
The 1964 Osram Australia Campaign - There is also a link to Mazda Lamps UK
Like cables that can overheat, and potentially melt, transformers can get overloaded. The amount of power a transformer can handle without getting too hot or becoming 'saturated' is specified as volts times amps or VA. For a particular frequency, in this case 50 or 60 Hz, this tends to be a function of physical size. You can quickly get an idea of the load a local grid is carrying by the size and number of transformers you can see.
Some energy is lost as electro-magnetic radiation. This almost all-pervading 50 Hz (or 60 in the US) radiation continuously bathes us throughout our lives and can be heard by touching a finger to the central (active) terminal of an amplifier or video recorder audio input.
The energy lost due to radiation rises with frequency whereas transformer size reduces, for the same VA, with frequency. This is why generators do not increase the frequency and why the older plug-packs, for charging phones, and so on, were bigger and heavier than the new ones. The old ones contained a mains frequency transformer to drop the voltage (to say 6 or 12 volts) before converting it to DC.
The newer ones multiply the frequency, so that a tiny transformer is all that is needed, before conversion to DC. They use an electronic circuit to step-up the frequency in a way that (unlike the older transformer) is relatively independent of input voltage; these are known as 'switched mode power-supplies'. The little ones (eg to recharge your phone) have an adverse impact on power factor, causing some small additional losses in the wiring in your home. The big ones, like those in your desktop PC and recent television, have power factor correction as part of their circuit.
In the early days of electricity transmission in the US and England a DC grid was in competition with AC.
Hence the joke in the cartoon above. The initial transformer in an AC powered valve radio, used to supply high voltage to the anodes of the valves and low voltage to their filaments, would offer no impedance due to induction; just a pure resistive load with small resistive value. The 'primary' would heat very quickly and burn-out if connected to DC.
Radios were very expensive and this silly, wealthy man does not know the difference - ha ha!
DC pulses in the grid, due to magnetic pulses from sunspots and supernova, can similarly destroy transformers in the grid; as happened in Canada in 1989.
Today the most common use of DC on a large scale is to run electric trains. All the older electric train and tram networks in Australia employ DC transmission. This was used to reduce heat losses associated with relatively low voltages and high currents.
DC was once produced directly in dedicated power-stations (like the Power House Museum in Sydney). Later it was produced by rectifying AC from the grid in substations equipped with three phase mercury-arc vapour rectifiers (like huge vacuum tubes - or light-bulbs) that glowed blue in the night and could be seen from the trains. When I was a little boy my father, who was an electrical engineer, took me to see one while it was down for maintenance; I was very impressed. Of course I was very familiar with the old valve radios that used vacuum tube rectifiers (No 80).
DC is now produced from AC more efficiently using large silicon based semiconductors called solid state rectifiers.
But DC has its own issues, including induced corrosion in nearby metal pipes due to the constant voltage gradient. Most modern railways, including some in Australia, now use much higher voltage AC (directly from the grid) instead.
In recent years some long distance high voltage lines have been built using DC. Read More...
Whereas an AC transformer works in both directions and a grid link can be transmitting power in one direction (say from NSW to Victoria) and then in the other virtually instantaneously; DC needs more elaborate conversion, to and from AC.
It's relatively easy to convert AC to DC but the reverse requires some elaborate electronics (called an inverter) to produce an alternating current in the required waveform and to synchronise it correctly to the host AC grid. Very rapid heating and equipment loss can result if this is not done properly.
If the link is to be used in both directions rectifiers and inverters are required at both ends; with appropriate switching.
Once this could not be done economically due to heavy energy conversion losses and enormous equipment expense but in the closing decades of the last century rapid advances in ‘solid state’ silicon semiconductor technology substantially addressed these difficulties.
Although gigawatt scale equipment is still very costly this technology can bring energy losses down sufficiently to make long distance high voltage DC transmission economically competitive with very high voltage AC; in some circumstances, particularly under salt water where AC induces electrical currents that waste energy.
Why buy electricity when you can make your own?
Despite transmission losses and the costs of transmission, domestic mains electricity is considerably cheaper than making your own. Even with the latest increases due to the carbon tax and MRET it is still quite cheap (written in 2012); at around $0.26 cents per kWh; and less for off-peak.
You can’t easily match this by making your own electricity.
Transporting energy from large efficient point sources is generally cleaner as well as cheaper than generating electricity locally on a small scale.
The average Australian household consumes about six megawatt hours (MWh) per year but peak demand can easily exceed ten kilowatts (kW). For example with: the clothes washer and dryer; dishwasher; kettle; toaster; oven; cook-top; instantaneous hot water; and a room heater running; plus the more continuous loads like refrigeration, lighting, TVs, computers, pool pumps etc. peak power might be double this number. If air-conditioning is also running ten kilowatts is totally inadequate.
If you install your own diesel generator capable of supplying peak power of say 10 kW and running continuously 24/7 you will have a big bill for the capital (opportunity cost); maintenance; and depreciation.
Your fuel alone will cost you more than simply buying the same energy from the grid. This is why the proponents of electric cars say they are cheaper to run than cars run on petrol.
You might argue, as some do, that solar energy is plentiful and free. Proponents of this theory could test it by cutting themselves off from the grid and attempting to get their six MWh, plus their morning and evening peak electricity demand of 10kW, from solar panels. They will need around 30 panels (these would totally cover a typical suburban frontage) and because domestic peak demand is when the sun is not yet up and in the evening, they will need some very big and expensive batteries as well to flatten out day to day peaks and troughs and to provide energy when the sun doesn't shine at all..
My back of envelope estimate puts the cost of such a system, using prices presently quoted on-line, at well over five times that of buying the same energy from the grid.
Since I first wrote this article batteries have become cheaper and Electricity consumption has dropped as cost increased. By 2016 Li-ion batteries had surpassed lead acid as the cheapest 'whole of life' option. The cost of batteries to car companies like Tesla dropped below the US$200 per kWh barrier for the first time (< $200,000 per MWh).
Yet based on these lower prices, to continue to behave as if they were still grid connected an average household would still need several hundred thousand dollars worth of batteries.
So off-grid country properties (that do rely on solar power for electricity) have to manage peak demand to well under 10kW; and use alternative energy sources like gas or wood for cooking and heating; in addition to oil and/or petrol for backup generation, farm machinery and some power tools.
But as electricity prices rise gas is beginning to be a local generation option; either as a complement or as an alternative to the grid. Worldwide, this is increasing the market's demand for gas and thus the export and domestic price.
Nevertheless market equilibrium has resulted in gas co-generation in some large commercial buildings and industry becoming a real option.
Gas powered fuel cells are being trialled as a means of local grid demand/supply matching in several locations. These units are very energy efficient with much better fuel utilisation than large scale thermal generation.
When using natural gas the hydrogen goes to making electricity and water at around 60% electrical efficiency; while the carbon component is oxidised producing heat and carbon dioxide. For every kWh of electricity they generate, around 1.2 kWh (4,000 BTU) of heat is produced. This needs to do something useful, like heating water; to bring the total efficiency to around 85%
Like solar or wind the capital cost per kWh generated is still considerably higher than conventional coal generated electricity. But with falling prices, as the technology is refined and as grid electricity prices rise, fuel cells may well become a competitive generation option for local peak smoothing within an integrated local distribution grid.
The problem with wind and solar to an even greater extent is seasonal, daily, and hourly variability. Electricity demand is also variable but in a far more predictable way; again seasonally, daily and hourly. These demand and supply peaks and troughs hardly ever match. In particular winter demand peaks in southern latitudes occur when solar incidence is low or non-existent. Wind does blow at night but often when demand is very low.
I have explained (in Renewable Electricity, elsewhere on this website) that even in the best wind provinces it is available for generation for only about a third of the time and that this limits the practical contribution that wind can make to total generation to around 30%. This capacity factor limits solar to much less as it is dark for half the time and overcast or raining for another proportion.
Let's take a real example: unlike much of Australia wind resources are of a very high quality in parts of South Australia and Tasmania. This has encouraged a great deal of wind investment there. In 2016 in South Australia (just 5% of the national electricity market) wind generation reached 4,292 GWh, from over 700 installed turbines with a combined capacity of 1.6 GW of wind generation.
As expected, a simple calculation based on hours in a year gives us an average capacity factor of 31%. The remainder of the time the State was dependent on other sources of electricity. In this case, fossil fuels and two interlinks to the neighbouring State of Victoria allowing the wind farms to dispose of unwanted energy when local demand is low and for consumers to get power from interstate when there is no wind. Nevertheless this swap was in the wind generator's commercial interest as the farms produced 33% of the State's generation, the surplus, that enjoyed a substantial financial subsidy, being exported.
But fluctuations in the wind; high air-conditioning demand; and major storms, together with the closure of base load fossil generation; and the limitations of the interlink, resulted in serious blackouts.
As I previously discussed, an effective, efficient and low capital means of energy storage could dramatically change this. But it needs to be on a very large scale. You can easily see that to move to 90% wind power in South Australia first they would need another 1400 turbines and then a means of storing two thirds of their energy for when the wind is not blowing: 8.6 terawatt hours (TWh).
The intrinsic cost of wind energy, when not subsidised by means of large-scale generation certificates (LGCs), is already very much higher than the present alternative fossil-based sources, as demonstrated by the price difference between South Australia (33% wind, 60% fossil) and Queensland (0.05% wind, 94% fossil) in the following table.
National Electricity Market
Price maximum (A$/MWh)
LGC price (current wind subsidy - $ per MWh)
|Annual generation 2014-15 (TWh)||13||56.5||64.3||68.2|
Note that Qld is considerably less populous than NSW but exports its cheaper electricity to the larger State
Sources: Office of the Chief Economist; NEM data dashboard; LGC closing rates 20/3/17
Given this high cost of wind generated electricity, the additional cost of any electricity storage would need to be trivial to avoid totally uneconomic electricity price increases. South Australian electricity distributors already pay four to five times the national average for their wholesale electricity.
At the moment the only commercial large scale (terawatt) method for storing energy is pump-storage, associated with hydroelectric schemes. The best of these lose over 30% the energy in pumping water up hill and then letting it run back through the turbines, an added cost. Pump storage is primarily used for providing extra generation when consumer demand is high; not for smoothing wildly fluctuating generation from wind or solar farms.
In Australia hydro-generation is far too small and unresponsive to compliment a large-scale contribution of renewable energy. The entire capacity of the Snowy Mountains Hydroelectric Scheme is only 7.8GW. Pump storage is a tiny fraction of this but an increase is within reach of complementing the presently small contribution of wind generation, albeit at a cost to consumers or taxpayers.
Due to falling panel costs and improved efficiency, photovoltaic (PV) solar generation may now be cheaper per kWh than wind. But the lower capacity factor and rapid fluctuations in output when it is cloudy require even higher levels of storage to make solar competitive as a total energy solution (see Why buy electricity when you can make your own? above). Any storage solution like batteries needs to be highly distributed to be sufficiently responsive; ideally connected and matched to particular photovoltaic solar panels.
Indeed many off-grid PV solar and wind installations use batteries. So why not use them to allow more wind and solar for the grid in general?
Batteries store electricity by converting it to chemical energy and then back. An ideal battery would store electricity with no losses, for example heat being generated during charging or discharge. It would be constructed from plentiful; non-toxic chemicals; and would be light weight to enable its use in vehicles and hand held devices. It would work in any climate and safely store chemical energy at a similar density to high explosives like TNT. As in any battery the chemical reaction must be reversible. This should be possible many thousands of times over, before the storage qualities are significantly degraded, because a thousand cycles is only three years of daily use. And recharging should be as fast as possible - certainly no more than the discharge time.
Since I first wrote this significant advances have been made in battery technology and these have been quickly commercialised. Sometimes too quickly resulting in fiery mobile phones and damaged aircraft.
For more than a century our best rechargeable battery was the lead-acid accumulator, like that in your conventional car; truck; or buss. Then, at last, in the last decade of the 20th century, new materials based on rare-earths offered new avenues of research. Commercial nickel metal-hydride (NiMH) batteries, that met many of the desired criteria, became a reality. Nickel is less dense than lead and the new batteries packed twice as much energy per kilogram as lead-acid cells. As an added bonus they could be small or large and had no messy liquid acid or fumes. This improvement opened the way to many new types of hand tools and electric vehicles.
For many years lithium shimmered as the 'Holy Grail' of battery technology. Lithium is the lightest metal and the least dense solid element. It's also highly reactive, with the greatest electrochemical potential and energy-to-weight ratio of any element in the periodic table.
But lithium metal is so reactive that it spontaneously bursts into flame and early attempts to build a safe and practical battery ended in tears. Nevertheless work went on, involving many improvements until, in 1985, Akira Yoshino assembled the first practical rechargeable lithium-ion battery at the Kawasaki Laboratory of the Asahi Kasei Corp in Japan. His new battery avoided using lithium metal directly, making it less unstable, yet provided another doubling in energy density over NiMH.
With volume, the battery prices quickly fell, so that new opportunities and markets, like little drones and more complex telephones, proliferated. The trouble is that Li-ion batteries are still rather dangerous. Higher current energy density comes with a risk, as Boeing discovered on their new 787; as did UPS when a battery fire brought one of their planes down. Samsung too had to withdraw their Samsung Galaxy Note 7 recently due to higher density batteries catching fire. Further increase in energy density is likely to make them even more dangerous.
Among these new markets for batteries are electric cars.
The electric car maker Tesla is well aware of the dangers inherent in the lithium-ion (Li-ion) batteries it uses. At the present time a Tesla P100D can get a third of the way from Sydney to Brisbane carrying an 85 kWh lithium-ion battery weighing 544 kg (around half a ton). To obviate the risk of fire or explosion the Tesla 'battery' is not a single unit but consists of 7104 small individual Li-ion cells organised in 16 modules, separated across a wide pan below the car.
It would be nice to drive all the way to Brisbane without a lengthy recharging stop. But the risk would be significantly magnified if the battery had four times the present energy density, let alone the density required to go head-to-head with conventional car with a full tank of petroleum.
Although petroleum has one hundred times more potential energy than a super-battery, that energy is difficult to release all at once. This is because the fuel requires three times its weight in oxygen to combust and there generally isn't that much oxygen around. That's the reason conventional cars seldom explode, although there are tens of thousands of crashes every year. It's actually quite difficult for movie makers to make cars explode. To get a nice explosion in the movies, the fuel is usually atomised by a real explosive because, in real life, unless atomised by the crash, there's generally not enough oxygen close-by to sustain more than a relatively unimpressive fire.
On the other hand, batteries contain all the chemicals required to release their stored energy. They're chemically self-contained and if shorted or become unstable in a fire, like TNT, they can release their stored energy almost instantaneously. At the moment the Tesla battery has about the same energy as 75 kg of TNT split into over seven thousand little cells. Quadrupling this stored energy, say to get to Brisbane on one charge, would add an extra punch to every cell and put the battery up there with explosive potential of a 500 lb bomb. This is not just a Tesla problem. Any battery capable of this level of energy density, approaching that of petroleum, will have this problem.
Despite recent failures, an attractive feature of Li-ion technology, compared to other very high energy batteries, is its relative safety.
Tesla now manufactures stationary energy storage systems for off-grid solar. These significantly reduce the risks, compared to an automotive accident or a mobile phone, but they are often much larger. It's not entirely clear what might happen in the case of a building fire or collapse or flooding - presumably Tesla have engineered the units with a worst case scenario in mind, as the larger units have the energy storage of a very large bomb indeed.
It's tempting to think that with Li-ion technology we have found the Holy Grail of batteries - all we have to do is get the price down - and mass production is the answer. But the batteries still fall well short of our ideal, as outlined above particularly in terms of cycle life, efficiency (energy lost to heat) and cost.
Here are some features of present generation of, advanced, high energy density, batteries:
|Nickel metal-hydride (NiMH)
Low self-discharge types:
13.9–70.6% (per month)
1.3–2.9% (per month) at 20 °C
8% (per month) at 21 °C
Source: Wikipedia: NiMH - Lithium-ion
Note in particular the cycle durability. Longer battery life is one reason that Toyota uses NiMH cells in it's hybrid vehicles.
Others are higher intrinsic safety and greater specific power.
Cost remains the greatest issue of all.
According to Wikipedia, in 2017 the price of energy storage using lithium-ion cells has dropped to less than $200 million per GWh. This is the price Tesla pays. They will cost you a lot more.
So some proposed batteries as a solution to South Australia's woes.
Let's say that just 5% of battery storage would avoid blackouts during periods of peak load when the wind drops. Yet in this example just 100 GWh of battery storage, to smooth out wind fluctuations would cost an eye-watering twenty billion US dollars, way more than a new power station. And if these batteries were discharged several times a day to cover drops in the wind they would soon need replacing. With a maximum life of 2,000 cycles the batteries would only last half a dozen years, probably less, like your mobile phone or car battery. All of these costs end up on the consumer's electricity bill.
As it turned out the political populists in South Australia were just talking tokenism: 100MWh of battery storage. This is equivalent to just 1% of the average daily generation of the State's wind farms - about a thousandth of that required to make a difference, should the wind drop or equipment fail during peak demand.
In other contexts, like PV solar, batteries are a partial answer (see above). But although great strides have been made in battery technology costs are still, at least, one order of magnitude too high. Energy losses also remain a significant factor, as high energy batteries lose up to 20% of the energy stored as heat and, more gradually, most of their stored energy by leakage over a year.
As we have seen, with repeated heavy use few batteries retain their storage capacity for more than five years. Super-capacitors store electricity as charge without a chemical conversion. Thus they have lives of many decades and can be repeatedly charged and discharged. But their energy density is still less than a battery so they presently cost more. Further, unlike a battery, a capacitor's voltage falls more or less linearly as they discharge so they need additional electronics to compensate for this; adding to cost and degrading their intrinsic efficiency.
A possibility I once considered (and now publicly declare as the likelihood of patenting the idea is now nil) is that a capacitive layer could be incorporated in future vapour-deposited thin film PV solar panels. Such an innovation could extent their output during periods of darkness and to meet demand peaks thus reducing dependence on batteries for energy smoothing.
There are many applications in which their advantages, like long life, outweigh the higher cost over a battery but it is unlikely capacitors will entirely replace batteries for large scale energy storage any time soon.
Other methods like heat storage in molten salt or hydrogen storage are costly and lose too much energy (30% to 70%) in storage and/or in the recovery to electricity.
There is a discussion of the Spanish experience using hot salt for storage, in the article on Spain.
My brother is an advocate of mechanically lifting weights. Others suggest pressurising gas to drive water through a turbine, for example in underwater bags. But in each case, capital cost and conversion efficiency remain significant hurdles.
As electricity prices rise there is pressure to make our current systems more efficient.
Some commentators have suggested converting the whole grid to direct current, DC. This would decrease grid losses and extend the grid's practical geographic reach.
As it turns out my family was once heavily invested in DC systems (see The McKie Family - Untimely Death), leading to events without which I would not have been born.
As advocates point out most of today's electronic devices could easily be converted to run on DC. But most motorised appliances could not.
All the transmission and distribution transformers, of which there are hundreds of thousands, would need to be replaced by much more complex electronic equivalents that would be likely to be more costly; even when mass produced.
Although the conversion would be daunting it would be a way of saving some of the energy presently lost to simply heating the environment.
It would also reduce or eliminate the constant low frequency radiation that now surrounds us: the buzzing noise you hear if you touch your finger to an open microphone connection.
This could be a dubious benefit as there is no evidence that this radiation is harmful. It is even possible that this actually protecting us from more dangerous natural radiation; and is a factor in people living longer today than in the past.
Some blue-sky enthusiasts suggest that a superconducting DC grid will form the future electricity transport backbone; for example to span the 4,000 kilometres from Sydney to Perth.
The electrical conductivity of most metals (and other conductors) changes according to temperature.
Except in some exotic materials they become more conductive as temperature falls.
Some metals like niobium-titanium or niobium-tin alloys become superconductors at very low temperatures, just above absolute zero. That means that electrical currents are transmitted freely with no resistive losses; and consequently no electrical heating.
The Large Hadron Collider (LHC) has miles of superconducting magnetic coils. Many magnetic resonance imaging (MRI) machines in hospitals employ similar coils.
To make such a super conducting magnet the wire needs to be bathed in liquid helium. This reduces its temperature to just four degrees above absolute zero. The boiled-off helium gas is then recovered and re-compressed to liquid helium in extremely sophisticated cryogenic apparatus. Not only is this apparatus very expensive but it consumes energy to remove heat leaking into the system.
According to the CERN website - the LHC's cryogenic system employs 120 tonnes of helium to keep the superconductors at 1.9 K (−271 °C, −456 °F). Running the cryogenic system including: circulating the liquid; recompressing the boiled off helium gas; and disposing of the heat continuously consumes 40 MW of electricity.
If this cooling system fails, at any point in the conduction path, the material ceases to super-conduct. The very high currents in use instantaneously vaporise the metal at that point, often causing an explosion and/or very serious equipment damage. This happened catastrophically in one of the first runs of the LHC, shutting it down for nearly a year.
This risk, together with the financial and energy cost of supercooling present generation superconductors, if they were stretched out in hot environments over hundreds or thousands of kilometres, makes them impractical at present for commercial electricity transmission.
But research continues into high temperature superconductors. These already exist in the laboratory but seem to collapse under high magnetic fields; making the present generation useless for high power applications. Their operation involves quantum mechanics and is still somewhat mysterious. This is one area in which a better understanding of quantum mechanics, in part through work at the LHC, might change the future.
Assuming anthropogenic climate change has reached criticality, principally due to overpopulation, the World needs to urgently reduce our consumption of fossil fuels. See: Climate Change - a Myth? on this website.
At the moment our only significant economic alternatives to fossil fuels, presently required to provide energy when the wind is not blowing and the sun is not shining, are hydroelectricity and nuclear (fission) power. Recent studies show that 'fracking' for gas and even burning wood are potentially worse for the environment than burning coal.
Uranium is presently the principal nuclear fuel but as the very heavy elements, like uranium and gold, are created in comparatively rare neutron star mergers, these elements were also relatively rare in the dust that coalesced to become the Earth, so accessible resources are limited, maybe to a millennium worth of fuel. Fortunately to those recourses we can add thorium that can be 'bred' as a potentially safer nuclear fuel.
So with wind and solar generation meeting up to half the demand, the World could wean itself off burning coal and gas for electricity within a few decades; and still have sufficient energy to reduce dependence on petroleum and sustain a population of ten or eleven billion with more equity in health and material wellbeing, next century.
After uranium and thorium we have an almost limitless source of energy - nuclear fusion.
The Sun is powered by fusion but on Earth the sun's energy fluctuates too much to gather it's energy easily; due to the Earth’s rotation; and the tilt of its axis that gives us summer and winter. It also give us tides and generates the weather, that gives us wind energy, but all these factors get in the way of the radiant energy reaching our solar panels on a consistent basis.
Some commentators have suggested that solar collectors in orbit would provide a 24/7 energy supply if we could get it down to the surface. We might do this with lasers or microwaves. In either case there would be very significant dangers and environmental considerations to be addressed. Either method would make a very nice James Bond, or even Star Wars, style death ray.
But we have already harnessed this source of energy on Earth energy many hundreds of times. It is the principal source of energy in the hydrogen bomb. Unfortunately we don't want all that energy at once.
Scientists have recently succeeded in creating controlled fusion on a small scale in the laboratory. But this is far to small and costly to be of commercial use.
Somewhere in between would be good.
At the moment there is no practical commercial reactor in sight; principally because conventional nuclear fission reactors, using uranium (and other unstable heavy elements) are a lot less complex and therefore less costly.
But work continues. A complexity or cost breakthrough in nuclear fusion would solve our energy needs as a central issue facing mankind; particularly if we are also successful in reducing world population to sustainable levels in the future.
The ultimate Science Fiction (or Pons and Fleischmann/ Back to the Future) dream is that particle physics may someday reveal a reversible way to store energy as mass and then recover it as energy when wanted; cheaply with little or no loss. Batteries already do this on an infinitesimal scale but a gram or so of mass is presently out of reach.
This is like the alchemists dream of turning base metals into gold.
It would be far more valuable than that. The entire energy transport network; the grid; gas; and petrochemicals; would become redundant.
You might wonder why I'm bothered with this subject.
The answer is that electricity has always been part of my life; and that of my ancestors almost since it was discovered (see The McKie Family - Untimely Death).
Indeed, it has probably always been part of your life too. It's the revolutionary discovery that has led to the modern world. So it shouldn't it be of interest to everyone?
Joke: How many New Yorkers does it take to change a light bulb? Two: One to call the handyman; and one to mix the cocktails while they wait.