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Energy Efficiency
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Energy Efficiency and Insulation

Types of Energy

Here are some of the different types of energy...

Thermal and lightNo explanation required
KineticThis is the energy in movement, like a train in motion.
ChemicalThis is found in chemical bonds and can be stored.
NuclearThe energy from an atom's nucleus.
PotentialAnother energy that can be stored, there are two types:
Gravitational potential energy (GPE) - the sort a person has alot of before they jump off a bridge with a bungee rope. And elastic, the sort that the rope has when it is being pulled by the weight of the jumper

Energy Efficiency

Firstly, to understand energy you need to understand this: it is not something you can see or feel or sense in any direct way - it's just there. Secondly, energy does not disappear or get 'used up' but rather is converted or transfered into another form of energy. And this is where efficiency comes in.

Let's use the example of a light bulb! You don't want it to do anything, other than produce light. But the old traditional light bulbs we all should be getting rid of also produce heat, and quite a lot of it.

lightbulb with energy inputs and outputs

A 60W lightbulb is put on for one minute. A watt is equivalent to a joule per second, so it uses 3600J

The bulb produces 360J of light energy in that minute and also 3240J of heat energy. To calculate the efficiency...

Efficiency = [useful energy / total energy] x 100%
= [360 / 3600] x 100%

An energy saving bulb on the other hand is designed to produce as little heat as possible. In a similar experiment, but with an energy saving bulb, it produces only 80J of heat. So to get the same light output the bulb only needs to be...
360J + 80J = 440
440J / 60s = 7W


Insulation is also another way of making something more efficient - it cuts down the amount of heat energy leaving where it is required.

You can prevent heat being lost from the house by having double glazing or cavity wall insulation.

diagram showing how cavity wall insulation and double glazing reduces heat loss

One of the ways that heat is transfered is by convection, where warm air rises (as the density descreases) away from the source of heat, but then cools (density increases) and sinks. In double glazing the gap between the two panes is too small to allow this movement of air. As well, air is a poor conductor, so less heat leaves if it has to travel through air, then solid, then air and then solid agian until it finally reaches air.

With the cavity wall insulation, the gaps or cavities between the two walls are filled with an insulating material, which creates many small pockets of air that prevent heat from leaving. Older houses only have one wall so are less energy efficient.