Ok, well, that’s a half truth. It is a fantastic tool for raising awareness of our power consumption, the act of turning our electrical devices off for an hour and then back on again is, well, stupid. In most cases, it takes less power to keep an electrical device on for an hour than to turn it off and on.
Let’s look at the theory a little bit. Apologies, this will get real technical, real fast.
We have 2 energy storage components in our electrical circuits. No, I’m not talking about batteries, I’m talking about capacitors and inductors.
Capacitors, through use of parallel, electrically charged plates, store “Voltage” (The mere concept of “storing” voltage is silly, but to keep things a little simple, let’s assume we can).
Your thinking, “Ok Phill, that’s cool, how does that mean it’s bad?”
I’m glad you asked faithful reader.
Think, at initial conditions, t = 0, before we turn on the circuit, it contains NO charge. It’s just chillin’ there. We throw the switch, suddenly the capacitor starts to charge. The voltage across it increases at an exponential rate. At V = E(1 – e^(-t /τ)), where E is the source voltage, t is time and τ is the time constant of the given circuit (τ = RC). The capacitor will reach full charge after 5 time constants, so depending on how complex the circuit is, it will take longer to charge.
Ok, now to the other side of the coin, capacitors also draw current! Yes! But ONLY when they are charging. Now this is at a rate of I = (E/R)e^(-t/τ) , where R is the circuit resistance and again t is time and τ is the time constant.
Right. Now, Power. What everyone is going on about with “Earth Hour”. Power of a circuit is defined as P = VI. Voltage times Current. So, looking back at our capacitors, we have a device that will draw a large amount of current starting out, then drops down, and the voltage starts out small and moves up. You think “That’s ok, they will cancel each other out”. Nope.
Voltage of the ENTIRE circuit. You will have other components drawing current and requiring voltage. So the voltage of the circuit, with a suddenly applied voltage source, will still be larger than the voltage of the capacitor. Therefore, at t = 0+ (Just after we turn on the circuit), we have a large current draw with the same voltage, resulting in a large power draw, via the relation of P = VI.
Inductors are essentially the same, except they “store” current. So the current flow through them drops exponentially and the voltage rises exponentially. So the same problem applies with the P = VI.
Now that’s out of the way, how does this effect anything?
Well. The basic structure of an AC-DC power supply is a Bridge rectifier (1.4V drop at all times), Transformer (A really big inductor, yeah, it has inductance) and a set of Capacitors. You turn on, say, your phone charger. To you, it works instantly, to the device, it has a “start up time”. The capacitors in the circuit need to reach their charged state, the transformer needs to warm up. All this takes more power than required to maintain its state of equilibrium.
This power supply structure is in almost EVERY device you plug into the wall. AC is easier to transport, but DC is much more useful in everyday applications.
Well. That’s power supplies out of the way, let’s look at lights.
Those “Power saving” fluorescent globes you buy? Yeah, the ones that take age to start up…
They require an extremely large voltage to turn on. They’ve got little “Starters” in them that convert large current flow into a large voltage spark to turn them on. Now, P = VI. Large current OR voltage flow means…Large power draw. Once they have reached their state of equilibrium (after 3 mins i might add) then they settle down. They still draw a very distorted current, which, trust me, is bad. You aren’t paying for the distorted part, but the power companies still need to generate it and pay for that. But we’ll get back to the power companies later.
“But Phill, I don’t like them, so I have plain old Incandescent globes”. Well done, I salute you. I hate the power savers. That’s more personal opinion though. You’re still not off the hook. The Incandescent globes are made by making tiny coils of tungsten, and hence, making a small inductor. Again, P = VI, la di da. Drawing large power at start up. There is also another thing to keep in mind. As temperature increases, so does resistance. Now those globes get mighty hot don’t they? Well what about when they have been turned off for a while? They are cold. Therefore, resistance is lower, therefore, a higher current draw (Based on fundamental law of electronics, Ohms Law, V = IR. Or as we are using it here, I = V/R ). The element heats up, resistance gets higher, less power draw.
Well. That’s the maths behind the circuitry done, let’s look at the economic side, yeah?
Power distribution is done by 3 different companies, or branches. There is the company that generates the power, the company that distributes the power, and the company that provides it to you.
The providers buy the rights off the distributers, who buy their power from the generators. Now, this happens on the hour, every hour. The distributers have to guess what the next hours power draw is going to be, and buy that much power off the generators, who will take power generation plants up and down to meet the demands of the suppliers.
So, if we have a massive dip of power draw, the generators will lose money, the distributers will lose money, and the suppliers will lose money. NOT just from you not using power, but because
- To shut down the generators, for even an hour cost a fortune. But they can’t leave them running because no one is buying the power.
- To turn the generators back on, there is again, inductors and capacitors, in the systems. Now, generators are HUGE inductors. How much current do you think it takes to get it up and running again?
- Power factor correction.
“Power factor correction? What’s that?” That my friends, is the bane of power generators and distributors around the world. When you plug something that has an inductor or capacitor in it into your wall socket, it will draw both real current, and an Imaginary (Complex) component. You, as a consumer, only pay for the real power you draw, but the distribution company has to buy real AND imaginary current from the generators. To combat this, for every capacitor and inductor you plug in, they plug the opposite in. This evens it out to mostly real power draw. That is power factor correction. Now imagine turning everything off suddenly. Suddenly the distribution and generation companies are drawing FAR too much imaginary power. Power that still needed to be generated. Power that you are trying to save by turning everything off. So they correct this buy unplugging all their capacitor banks so it’s just back to real power.
Then you turn everything back on. Suddenly they are drawing the large imaginary power again. Again, they still have to generate that power. So they have to plug all their capacitor banks back in. Massive energy and money loss for the major companies. Who do you think they will pass these “Savings” on to?
Well, I’ve defiantly rambled on for FAR too long. Suffice to say, during Earth Hour, I’m not turning ANYTHING off. I won’t be turning anything on either. Got to maintain the Equilibrium.