Physics: Useful Energy and Efficiency

Useful Energy

Energy is the ability to do work or cause change.
There are various forms of energy such as kinetic energy, potential energy, thermal energy, electrical energy, chemical energy, among others.
Energy can be transformed from one form to another, which happens in most daily activities and natural phenomena.
Useful energy is the energy which achieves the desired result in any energy transformation.
An example of useful energy is the kinetic energy produced by an engine to move a car.
In many energy transfers, not all of the input energy is converted into useful output energy. Some is ‘wasted’, often as heat.
Wasted energy is not lost but transformed into other forms which are less useful or unusable directly.

Efficiency in terms of energy transformation or transfer is the ratio of useful output energy or power to the total input energy or power.
It’s represented usually as a percentage, and can be calculated using the formula: efficiency(%) = (useful output energy or power / total input energy or power) x 100%.
The higher the percentage, the more efficient the device is, and the less energy it wastes.
It’s always physically impossible to have 100% energy efficiency due to energy loss mainly through sound or heat.
Devices are often designed to increase their efficiency, by limiting energy losses. For example, a car engine has its exhaust system insulated to limit heat loss or a television is designed to require less electrical energy to function.
Conductors and insulators can influence efficiency of devices. Good conductors of heat or electricity enable energy to transfer quickly and easily, while good insulators slow down the transfer of energy, which can be useful when trying to prevent energy wastage.
Adopting energy-efficient devices or practices helps in conserving energy resources, curbing pollution, and saving money.

The Law of Conservation of Energy states that energy cannot be created or destroyed, but it can be transferred from one form to another.
According to this law, the total amount of energy in the universe remains constant.
While energy transformations, understand that what looks like loss of energy is actually energy being transformed into a less useful form.
Sankey diagrams are a useful tool for visualising energy transfers in a process, showing useful energy outputs, wasted energy and the total energy input.

Energy is derived from various sources which could either be renewable or non-renewable.
Renewable resources, such as wind energy, solar energy, hydropower, and geothermal energy, are those that can be naturally replenished over time.
Non-renewable resources, including natural gas, coal, and petroleum, are those that do not naturally replenish in a short period of time.
Majority of the world’s energy comes from non-renewable resources, however, these are finite and their extraction and usage have severe environmental impacts.
Renewable energy resources are considered to be more sustainable as they have less environmental impact and are naturally replenished on a human timescale.