A Beginners Guide To Energy

Published: 18 Apr 2008
by Dr Kelvin Kemm

These days, at any type of social function that I attend, it is a virtual certainty that the topic of energy will come up.

What then usually follows is total confusion. The same is true of many newspaper stories on the topic. So I am going to give a bit of a beginner’s guide to energy.

There are all sorts of types of energy that we read about, including psychic energy, emotional energy, mental energy, and so on, let alone stories about the healing energy in crystals, or the energy that flows out of shiny stones into your tired muscles.

So let us get down to real energy, and not the fairy-tale stuff. In physics, energy is the ability to do work. Actually, it does sound confusing, because there is also a principle in physics that states that energy cannot be created nor destroyed it can only change form from one type to another.

Often, the person who has not studied the physics of it cannot see where the energy has gone, so it does tend to have a natural mystery about it.

Energy cannot be created nor destroyed, except in the case of a nuclear reaction. Einstein came up with the famous equation, E = mc2, which states that energy (E) is equal to the mass of an object (m), multiplied by the square of the speed of light (c2). What this tells one is that, if you took a brick and converted all its mass into energy through nuclear conversion, then there would be enough energy available to drive a large ship around the world a hundred times. That is a real load of power, but we will leave nuclear out of our story now. By the way, you cannot actually convert an entire brick into nuclear energy, so, as they say in the TV programmes, do not try this at home.

If one wants to know what is the total amount of energy used by the whole country, then this, in principle, includes all electricity, all petrol and diesel, all aviation fuel, all wood and charcoal burnt, and so on. In fact, to stretch it somewhat, it also includes all manual labour, which is the energy derived from the food eaten by people.

But, typically, when one refers to the energy consumption of a country, one would refer to electricity consumption, plus the consumption of liquid fuel, such as petrol and diesel. Many newspapers refer to ‘energy consumption’ when they mean electricity consumption. Since electricity is such a hot topic at the moment, let us talk a bit more about electricity. When electricity is being used, the rate at which it is used is measured in watts (W), or more usually, kilowatts (kW), which is a more convenient size for everyday use.

‘Kilowatt’ is not an amount it is a rate. If a person uses 10 kW for an hour, then that figure is an ‘amount’, and it is measured in kilowatt hours.

So, when you are eating your cornflakes, one spoonful every ten seconds, then a spoonful every ten seconds is the rate, which is like watts. When, in an hour, you have eaten the whole box of cornflakes, then that is the amount, as in kilowatt hours. The newspapers are forever getting these wrong.

So, if you use one kilowatt of electricity for one hour, then you have used one kilowatt hour, which is exactly the same as using half a kilowatt for two hours, just like taking two hours to eat the corn flakes you still eat the whole box. So you are not saving electricity if you use it slowly.

The electricity suppliers would like everybody to use less so don’t eat the whole box, so to speak. The other issue which gets confused is that the time of day also counts.

For electricity usage, there are peak usage periods, such as breakfast and dinner times. The electricity suppliers would rather spread the demand over the day, so if you want to be really cooperative, then have your bath at 03:00, when most people are asleep, and not near breakfast time or dinner time.

The bottom line is that we all need to both cut down on total electricity usage, where possible, and also to try to move our usage outside peak times, where possible.

There is a challenge to everybody to try to do this, so cut your kilowatt hours and move the kilowatts you do use into off-peak times whenever you can.