Energy Transfer: Efficiency

Understanding Efficiency

Efficiency is a measure of how effectively a device transfers or converts energy from one form to another.
It is defined as the ratio of useful energy output to the total energy input.
If all the input energy is converted into useful output energy, the device is said to be 100% efficient, which is ideal, but never achieved in real-world systems.
In reality, some energy is always ‘lost’ during the transfer, typically as waste heat, sound or light.

The efficiency of an energy transfer can be calculated using the formula: Efficiency = (useful energy output / total energy input) x 100 % .
The efficiency is expressed as a percentage, with larger values indicating greater efficiency.
Remember that although it is termed as ‘lost’, the energy is not destroyed - it has merely been converted into a non-useful form. This corresponds with the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only transformed or transferred.

To improve the efficiency of an energy transfer, you need to reduce the amount of non-useful energy output.
This might involve using materials that conduct heat less readily, modifying the design or using more advanced technology.
For example, energy loss from homes can be reduced by using insulation, double-glazing and draught excluders.
The need for improved efficiency is particularly important as part of efforts to reduce energy use, conserve resources and combat climate change.

In many common situations, energy transfers can be quite inefficient.
For example, only about 20% of the energy from burning fuel in a car engine is used to move the car. The rest is lost as heat and sound.
Additionally, while light bulbs are designed to convert electrical energy to light, a great deal of this energy is also inadvertently converted into heat. This is especially true for traditional incandescent light bulbs.

Understanding efficiency and its principles can help us make smarter choices in our everyday lives.
For example, choosing energy-efficient appliances can save money and reduce environmental impact.
When buying appliances, look for the EU Energy Label, which rates the efficiency of the product from A+++ (most efficient) to D (least efficient).