Why are generators not 100% efficient?

The efficiencies of the generators are not 100% because part of the energy is lost as heat during the generation process.

September 13, 2023
BY BISON

You’re not powerless when it comes to the efficiency of your generator. The system’s effectiveness heavily relies on the quality of fuel used, the construction of the equipment, and its maintenance. However, there is a definitive method to boost your power efficiency.

Enter the world of BISON portable generators. More and more industries are adopting this more portable power system for their energy needs. Improving the efficiency of your generator can significantly reduce operating costs.

In this article, BISON generator manufacturers in China explore the circumstances under which generator efficiency can work in your favor.

What does generator efficiency mean?

Although the principle of electrical efficiency can seem intricate, it is not difficult to grasp. In simple terms, efficiency is the proportion of useful output to input. What are you receiving in exchange for what you’re giving? It can be written as a decimal from 0.0 to 1.0 or as a percentage.

Consider this hypothetical: a generator set produces 100 kW of electricity while consuming 30 litres of diesel per hour. Litres and kilowatts cannot be compared directly, so the fuel volume has to be converted into energy input first. For a liquid-fuelled set, fuel energy input is Pfuel (kW) = q × ρ × Hu / 3.6, when fuel flow q is in litres/hour, density ρ is in kg/litre and lower heating value Hu is in MJ/kg. With an assumed density of 0.84 kg/litre and an LHV of 42.7 MJ/kg, the set receives 298.9 kW of fuel energy and achieves approximately 33.5% fuel-to-electric efficiency.

However, no generator can achieve 100% efficiency. Some energy leaves through the engine exhaust and cooling systems, while mechanical and electrical losses further reduce useful output.

Power capacity and conversion efficiency are separate characteristics. Suppose a generator takes in 1000 watts of mechanical power and delivers 700 watts of electricity: it has an efficiency of 70%. A 1000-watt rating, by contrast, describes capacity, not how well the generator converts energy.

In practice, the efficiency of generators can vary greatly. This depends on factors such as local weather conditions, the quality of fuel used, how often maintenance is performed, and the overall condition of the generator. However, by choosing a generator made by a BISON generator manufacturer, you can greatly improve the efficiency of your generator.

Why generators can’t be 100% efficient?

The generator efficiency ratings are not 100% because some energy is lost as heat during the generation process. This is due to the inherent inefficiencies of the mechanisms used to convert one form of energy into another. Additionally, some energy is lost as a result of mechanical losses due to the friction and wear and tear of the moving parts within the generator. Electrical losses can also occur due to the resistance of the wire and other components in the electrical system. Generators also have a certain amount of standby power consumption, even when they are not generating electricity, and generator efficiency standards can vary at different speeds and load levels. All of these factors contribute to the overall inefficiency of generators.

Impact of inefficient operation of generators

The inefficiency of generators has a number of implications, including:

Generators require more fuel to operate than they would if they were 100% efficient.
Generators produce more emissions than they would if they were 100% efficient.
Generators are less reliable than they would be if they were 100% efficient.

Factors contributing to lower generator efficiency

The following categories describe important losses in the alternator:

Friction losses: Friction losses occur when mechanical parts of the generator move against each other, causing heat and energy loss. This includes the friction between the bearings, gears, and other moving parts. Lubrication problems increase mechanical resistance. Regular maintenance, lubrication, and use of high-quality parts can help reduce friction losses.

Magnetic losses: Magnetic losses, also known as core losses, occur due to the magnetizing and demagnetizing of the core material that occurs with each cycle of the AC power. These losses are inherent to the operation of the generator and can be reduced by using high-quality core materials and efficient design.

Windage losses: Windage losses occur due to the resistance of the air (or other cooling medium) against the rotation of the generator. This can be reduced by using efficient generator cooling fan designs and keeping the generator clean and free of dust and debris. Deposits that obstruct airflow impair cooling. In gas generators, dust and dirt blocking the vents cause heating and wasted energy.

Electrical losses: These losses happen due to the resistance of the electrical conductors used in the generator. The resistance causes a portion of the electrical energy to be converted into heat. Using conductors with lower resistance and cooling the generator to keep the resistance low can help reduce these losses.

Generator design: The design of a generator can also affect its efficiency. Rotor and stator design and the quality of the materials used influence these losses.

It’s important to note that while these losses can be minimized, they cannot be completely eliminated. The goal of generator design and maintenance is to maximize efficiency by reducing these losses as much as possible.

How to improve generator efficiency?

Proper maintenance

Regular maintenance and servicing can help to keep the generator in top condition, reducing the risk of breakdowns and improving overall efficiency.

Regular load testing

Load testing helps confirm that a generator can deliver the required power under load and reveal performance issues that need attention. For diesel generators that frequently run at light load, manufacturer-recommended load-bank testing can also help reduce wet stacking.

Fuel quality

The quality of fuel used can significantly impact the efficiency of the generator. Using high-quality fuel can help to improve performance and reduce the risk of damage to the generator. Fuel that does not match a gas generator manufacturer’s specification can cause poor engine performance and progressive engine damage, reducing efficiency. Old fuel can cause starting problems and inefficient fuel use in a gas generator.

Optimal sizing

Choosing the right size of generator for your needs can also improve efficiency. A generator that is too large will consume more fuel than necessary, while one that is too small may not be able to meet demand.

Proper installation

Proper installation can also impact the efficiency of a generator. This includes factors like the location of the generator, the type of foundation it is installed on, and the configuration of the exhaust system.

Conclusion

Heat, friction and electrical losses explain why generators cannot be 100% efficient. Distinguish alternator efficiency from the fuel-to-electric efficiency of the complete set when comparing results. Match capacity and operating load to demand, follow the manufacturer’s guidance and maintain the fuel, air and cooling systems to reduce avoidable losses.

The energy industry is always looking for ways to improve the efficiency of its generators, and BISON generator is committed to providing the best possible product for its customers. As a generator manufacturer in China, BISON offers petrol, diesel and inverter generators for dealers serving different power needs. Work with the BISON team to select the right generator capacity and fuel-saving features suited to your customers’ loads.

FAQs

How do you calculate generator efficiency?

Divide useful electrical output by input and multiply by 100%. For an alternator, input is mechanical shaft power; for a complete generator set, it is fuel chemical energy input. Use matching power units and the same operating point and time interval. A power meter can measure electrical output; use active power in kW, not apparent power in kVA.

Does a greater wattage indicate increased efficiency?

A higher wattage denotes an electrical device's usage of more electrical energy over a certain duration. To illustrate, a microwave oven with 1,200 watts consumes double the electrical energy and generates double the heat in a minute compared to a 600-watt microwave oven.

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Winnie

Taizhou BISON Machinery Industry CO.,LTD

6+ years of expertise in generator export. A specialist in BSCI and international standards (EPA, EURO V, CE). Dedicated to providing professional solutions for generators, genest, and generator parts with a global perspective.

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