Nine things you need to know about electricity

In South Africa, electricity comes and goes: we call it load shedding.

That’s because Eskom, the state-owned power utility, is unable to generate enough electricity to meet demand, and so it “sheds” power over the course of a day, meaning scheduled power cuts for everyone in the country.

The economic impact is enormous, the personal irritation levels are high. All anyone can talk about is the (insert swearword here) load shedding, and ways to mitigate its effects on their lives.

In our house, things are not as bad as they might be, largely because my technically clued-up husband Bob Seddon has been making plan after plan: solar and battery-powered strips of LED lighting, for instance.

He has also patiently (he is very patient!) been explaining things to me, in a way in which even someone who, at the age of 14, gave up all pretense of being scientifically minded can understand.

Magic in a light socket?

And, dear reader, it occurred to me that there may be many people just like me, who view things like electricity according to science-fiction writer Arthur C. Clarke’s third law: Any sufficiently advanced technology is indistinguishable from magic.

But electricity is not magic, and only when you don’t have it all the time do you start to think about it, and realise that there are many things that you don’t understand.

In the service therefore of the technically clueless, I present Bob’s answers to some very basic questions. He was at pains to say that everything you are about to read is not the full scientific picture. It’s reductive and, in some cases, ridiculously simplified (see for example the explanation of what a turbine is). It is, rather, a way to think about things that we both hope makes sense to broad range of people. (The questions are mine, as are the italics bits in brackets.)

Here goes:

One: What is electricity anyway?

It’s complicated. Lightning is electricity in the wild, if you like. The stuff that arrives in our houses and businesses is essentially a flow of energy through a wire.

Two: How do you make electricity?

At the moment, almost all electricity produced by turbines. A turbine is a big spinning thing that produces electricity (there’s one in the main picture of this post). Wikipedia as a useful sentence: “A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work.”

(Stay with us people.)

So: in a coal-fired power station, coal is burnt to turn water into steam which spins a turbine which produces electricity.

(We have heard much of diesel-powered open-cycle gas turbines, which are used by Eskom to beef up our power supply: essentially, open-cycle gas turbines are combustion turbines fired up by a liquid fuel, that precious diesel.)

Hydro power, as produced by Cape Town’s Steenbras dam, uses the force of water to turn a turbine.

A nuclear power station reactor uses heat from a nuclear reaction to produce steam to spin – you guessed it – turbines.

In those big wind power stations, wind turns the big blades which turn… the turbine.

But in solar power, there are no moving parts. A solar panel captures the energy of the sun and turns it directly into electricity. We can use it in that form, but it is not a steady source of power because it is dependent on presence of light (the sun), so we store that electricity. The most common form of storage is a battery. But you could use that energy to move water and then get hydro power.

There’s another form of solar power, where you use mirrors to concentrate light on to a small area, often containing salt, where it can make something very hot. Salt stays hot for a long time, and you can use that heat to generate steam to spin that big spinning thing called a turbine.

All this is different from mechanical power, like that used to power steam trains and cars. Trains have cylinders and pistons driven by steam, while cars burn petrol to push pistons up and down, which turns the crankshaft which turns the wheels. The car battery provides the power to start the car, and the alternator recharges battery and runs lights and such.

Three: And there are different kinds of electricity?

Yep. There’s AC (alternating current) and DC (direct current). The difference between the two means thinking about waves, which are an accurate metaphor for what is happening here.

Think of a wave in the ocean. The ocean itself doesn’t move but the wave carries energy. Similarly, an electrical wire doesn’t move, but alternating current, which cycles from a positive voltage through zero to a negative voltage, and back again, carries electrical energy, through the wire.

In direct current, the energy is generated by a voltage (see below) differential (like the difference in pressure between the bottom of the ocean and the top).

The modern world almost always uses alternating current because it can run over long distances with little loss of power.

Four: How is it measured?

There are three basic measurements that people talk about:

Amps – a measure of electrical charge moving past a given place per second (so if you have a hosepipe, that’s how much water is coming through it).

Volts – this is a measure of the amount of force that is pushing that water through the hosepipe (battery power and lightning are measured in volts).

Watts – this is the amount of energy an item needs to function; the rate at which energy is consumed. A watt-hour is a unit of energy, the amount of energy an item consumes over a given time. And a megawatt? That’s a one million watts.

(Some information above came from these two articles:

AMPs, Watts, and Volts: A Guide to Measuring Power
What is a watt? )

Five: What is this thing called the “grid”?

Basically, it’s the entire network of electrical power spread across the country.

There’s an article in the Conversation that explains it well: The grid is made up of three things: generation, transmission and distribution.

Generation is the plants that provide electricity, transmission is the high-voltage lines that transport electricity across the country and distribution is that low-voltage lines that bring power to homes and businesses.

(That Conversation article is the single simplest explanation there is about the grid: South Africa’s power grid is under pressure: the how and the why)

Six: What the hell are all these different kinds of batteries?

A battery is a device that stores electricity as direct current – and that means all of them! So a torch, for instance, is designed to use direct current from those batteries you get in the supermarket.

Generally, batteries have three parts: a positive terminal, a negative terminal and an electrolyte. You can use various materials for these three components according to what you want to do with it. So a car battery, generally a lead-acid battery, has positive and negative terminals connected to lead plates which are separated by acid electrolyte. A chemical interaction between all these generates power.

Making the lead plates thicker gives you a deep cycle battery, which means you can take more current out of the battery without destroying it. And if you replace the liquid acid that separates the plates with a gel or something called AGM (absorbed glass mat), that makes the battery safer, and you can seal it up.

Lead-acid batteries have drawbacks – you can’t take out all the energy without destroying the battery and they have limited life spans. But they are relatively cheap because they are very old tech.

Then there are lithium batteries like the ones we have in our cellphones: they overcome many of the drawbacks of lead-acid batteries but they are much more expensive.

And the big problem with batteries when it comes to powering our houses is that they generate direct current, and the world is geared to used alternate current.

Seven: And that means these mysterious things called inverters?

Indeed. An inverter is a device that turns the direct current from a battery into alternating current, so that the power is usable by our houses.

So when you buy what’s commonly called “an inverter”, you are often buying an inverter that comes along with a battery. Most inverters still use variations of lead-acid batteries. The fancier the battery, the more expensive this bit of kit is going to be.

Eight: Why don’t batteries last forever?

They just don’t. Their chemical make-up changes over time.

Nine: How does solar energy power things in a house?

Solar power charges a battery, and an inverter converts it for use. A whole house solar installation takes lots of batteries and that that’s one of the reasons they are so expensive.

Dear reader, I for one now feel I have a better grip on the ways in which electricity is made, and how it gets used. And please, if you have read this from the point of view of technical knowledge, be kind. The magic stuff in the wires has been with us for a long time now, so much so that it is something we can’t see or think about. This is offered in the hope that it makes some of our world visible to us.


Main picture: A turbine at Soyama power station in 2010. Qurren (talk), with IXY 10S compact digital camera / Wikimedia Commons (CC BY-SA 3.0).

The stuff that’s always at the bottom of blog posts….

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