Calculate the efficiency of a system. Enter the total energy input into a system, and the total energy or work output to determine its efficiency. This calculator can also determine either the output or input, given the efficiency and the value of the other variable.
Efficiency Formula
Efficiency describes how effectively a system converts an energy input into useful output (and therefore how little is wasted), and it is often expressed as the percentage of useful work/energy output divided by energy input. In the SI system, work and energy are commonly measured in joules (J). Efficiency is very often used in applications of heat transfer since heat loss is a core issue in modern-day engineering. It's also used to evaluate mechanical, solar, and chemical efficiencies.
Efficiency can be calculated through the following formula:
N = \frac{W_o}{E_i} \times 100- Where N is efficiency
- Wo is the work output
- Ei is the energy input
To calculate efficiency, divide the output by the input, then multiply by 100 to express the result as a percentage.
Work and energy both use the standard unit of joules, but the calculator above lets you choose common energy units and converts them internally. You can use different units for input and output, but you should make sure you are comparing the same type of quantity (input energy to output energy, over the same process). The above explanation is for the use of efficiency in physics and thermodynamics, but efficiency can be used in anything from finance to work performance.
How to Calculate Efficiency
Efficiency is a measure of a system's ability to convert energy from one form to another. So a system with 100% efficiency will output 100% of the energy input. If you have studied thermodynamics, you know that 100% efficiency is unattainable for heat engines (and essentially impossible for real processes) because there are always losses, from heat transfer to friction.
Let's take a look at an example of how you can calculate efficiency.
- The first step is to calculate or measure the energy being input into a system. This is generally measured through direct means, like measuring the total electricity input into a system, but it can also be calculated.
- The next step is to calculate the total useful work/energy output. This can sometimes be tricky and require some manipulation of equations. The reason this can be hard is that very often, input is either electricity or heat, and the output is motion, like that of a motor. You may need to convert motion into work/energy using mechanics (for example, force-distance work or rotational work/torque relationships).
- Last, enter the input and output into the formula and analyze the result.
How to improve Efficiency
Improving efficiency is the backbone of continuous improvement in engineering, especially in mechanical systems. Mechanical systems can be extremely inefficient. Take, for example, a gasoline ICE (internal combustion engine). A typical gasoline engine often converts on the order of about 20–30% of the fuel’s energy into useful mechanical output (with the rest lost mostly as heat). That means roughly 70–80% of the energy provided by gasoline is not converted into useful work. Engineers have been working to improve this for decades.
Here are the best ways to improve the efficiency of mechanical systems:
- Reduce heat loss through the use of insulation
- Reduce the friction of parts through lubrication or redesigning components
- Reduce the number of transfer components. The less, the better
- Capture lost heat to power other systems
There is an unlimited number of ways someone can improve the efficiency of a system, mechanical or not. It's up to an engineer to think critically and come up with new ways to do that.
