Energy Resources and Transfer: Energy Transfers

Energy transfers can occur in many ways, such as by heating, radiation, electrical work or by force.
These transfers can occur between different energy stores, such as thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear, and internal energy.
Energy cannot be created or destroyed, only transferred or transformed. This is known as the principle of conservation of energy.
When energy is transferred, some usually becomes wasted energy - resulting in a less efficient energy transfer.
Work is done whenever force causes a displacement. Work done on an object is equal to the force applied times the distance moved by the object.
The rate at which work is done or energy is transferred is called power. The unit of power is the watt (W), equivalent to one joule per second.
Energy efficiency can be calculated using the formula: efficiency = efficient power transfer/total power input. Efficiency is usually represented as a decimal or a percentage.
When an energy transfer involves a heating process, the amount of energy transferred can be calculated using the formula: energy transferred = mass x specific heat capacity x change in temperature.
In a closed system, no energy or matter is transferred in or out, the total energy remains constant.
Conduction, convection and radiation are three modes of energy transfer. Conduction occurs through solids, convection through fluids, and radiation through any kind of matter, including vacuum.
Insulation can limit energy transfers by all three methods, reducing energy waste and improving efficiency.
Sankey diagrams are a useful tool to visually represent energy transfers, showing the useful energy outputs, wasted energy and total inputs.
Although energy transfers are usually represented as linear sequences, they often occur in complex interrelated systems, where many transfers can occur simultaneously and affect one another.