Types of generators and how they compare

4 Types of Common Generators: Everything You Need to Know

Different types of generators vary according to size, application, and external source, or mechanical energy, used.

How does a generator work?

The electric-generator definition is quite simple: a machine that converts mechanical energy into electricity. The primary purpose of electric generators is to provide backup power due to outages, though there are generators that serve as the only source of power, which might be needed in mining and oil and gas operations.

Generators are often categorised by their external source, or mechanical energy. To talk about various generators therefore involves types of electric power generation. So what are the types of generators and how do they compare? Let's find out.

What do generators run on?

The different types of power generation come from these external sources:

Gasoline	Typically used for short periods
Diesel	Most popular fuel for industrial generators
Natural gas	Generators rely on underground access to natural gas; more environmentally friendly than gasoline or diesel
Propane	Another greener alternative to diesel and gasoline; often the choice for fuel when natural gas isn’t an option

 

Other external sources include wind, solar, hydro (water), coal and nuclear energy, which are mostly used by generators in power plants to harness power for the grid and hydrogen, typically used in laboratories. Homes, businesses, medical centres and hospitals tend to rely on diesel, gasoline or natural gas to convert to electricity.

Types of generators

Typical generator examples by application: portable, inverter, standby and industrial.

Portable generators

What are portable generators used for?

Portable units typically power essential small appliances in the home or for camping. As the name implies, these are movable generators. If powered by gasoline, they typically run anywhere between 7.5 hours to 12 hours. We said “typically,” because a few can operate for 18 or even 24 hours. That said, the running time depends on load, which refers to how much power is being generated and what the generator is powering. The fuel tank is located inside the generator and appliances or devices and be plugged directly into the generator’s sockets.

Portable industrial generators, which can also do the job of commercial portable generators, are also available, and can run for less than 16 hours, powering multiple appliances. These can vary in size. Some are too large to be carried but can be placed on a trailer and taken to, for example, a construction site.

Portable generators usually use gasoline, diesel or natural gas. Some even rely on propane, which is more energy efficient than natural gas, but heavier. Propane is mainly used for caravans as it can run for days – some can even last for just over a week. Most portable units tend to be noisy, as they lack sound insulation. More models are appearing on the market today that address this issue.

Inverter generators

What are inverter generators used for?

Lightweight and compact, these actually fit the portable-generator definition, yet are considered to be a category all their own. Powering electronics with a generator can be tricky, but this is where inverter generators are invaluable. While they have many applications, they’re particularly useful for computers, microwaves, mobile phones and other sensitive electronic equipment that need certain values of voltage and frequencies.

How does an inverter generator work?

The mechanics are different from other portable generators. In terms of currents, the power from the engine is a high-frequency AC. It’s then converted into DC by the alternator. The generator has an inverter, which converts the current back to AC.

These extra steps in generating electricity, and the fact that the initial AC is high frequency, mean the current is more stable, which leads to less harmonic distortion. Thus, the electricity is as good as that provided by the mains electrical supplier. This also translates to energy efficiency – the generator adjusts its voltage to exactly what the connected load requires, no more, no less.

Popular as a type of generator for home, these units are also available as industrial inverter generators for use on construction sites and other demanding environments.

Standby generators

What are standby generators used for?

The standby-generator definition is a little loose. Usually, these are fixed to the ground, but not always. They are larger than portable units and are available for both residential and industrial applications.

Standby generator types are usually powered by natural gas, diesel, or propane. When a power outage occurs, the automatic transfer switch (ATS) disconnects you from the main power supply and transfers the electrical load to your generator. When power is restored to the mains, the ATS switches you back over. Note, natural gas can be a problem, however. If the outage is due to a natural disaster, natural gas pipelines are normally turned off to safeguard against explosions.

The running time of a diesel-engine generator is limited by the size of the tank. As standby generators can be large, they’ll also have larger tanks. Standby generators that operate on diesel can run for 24, 48, 72 hours – and some, even longer.

Open-set, or uncovered, diesel generators create noise at high decibels, while a natural-gas generator is more quiet. Placing either generator in an enclosure designed to reduce noise can help. Quarter-turn latches help enclosures isolate noise produced by generators, so pay attention to the small components.

What is a generator canopy?

This is a generator cover, and if sound-proofed, can help with noise. It also provides protection against the elements. Placing a canopied generator within an enclosure can add an important level of security and additional protection against weather.

Industrial generators

What are industrial generators used for?

These are typically standby generators, but on a different scale. They operate in an industrial environment where power is in high demand for everything from robotics, machinery and lighting systems to computing centres. For this reason, these units are large-capacity generators, robust and able to supply a long, continuous supply of electricity. Consequently, they need to be large and powerful.

Industrial vs. commercial generators

These are often be used synonymously, but they are different. You know an industrial-size generator when you see it. Most of today’s industrial generators are designed to supress noise with components such as heavy-duty vibration mounts, which absorb shock and vibration. An industrial generator can be found in power plants and some hospitals. Commercial generators are typically not as large, nor do their applications and environment demand the same level of power. Medical centres and office blocks would typically make use of these generators, depending on their needs.

Types of industrial generators

This refers to the mechanical energy being used and the generator’s size. For instance, as we’ve already noted, there are portable industrial generators, but these aren’t meant to do the job of the large, powerful generators. Industrial units tend to be diesel engine generators, although natural gas, gasoline and even hydrogen are other types.

Natural gas vs diesel generator

Once upon a time, diesel generators were considered loud and grimy, but advances in technology have solved those problems. Industrial natural-gas generators were, and still are, the greener option. And natural-gas units have also benefited from technology advances. They can now optimise the RPM of their engines, ensuring their response output closely mirrors that of diesel generators.

However, diesel has significantly greater peak energy density than natural gas. Energy density is impacted by engine and fuel conditions, so even a neglected diesel generator will probably surpass a natural-gas generator in performance.

Types of diesel engines

The two types of diesel engines are two-stroke and four-stroke. Typical diesel engines rely on the four-stroke cycle, while larger engines use the two-stroke cycle.

There are four stages of the engine’s operation: intake, compression, ignition and exhaust. In the two-stroke cycle, these four stages occur in one 360˚ revolution of the crankshaft. In a four-stroke engine, the stages take two complete revolutions.

Advantages of diesel generators

• Value – diesel generators tend to be more cost effective than other generator types, with a lower purchase price
• Fuel efficiency – diesel has a higher thermal efficiency than gasoline generators, which makes it cheaper to operate
• Durability – tough engines that stand up to different environments and conditions
• Low maintenance – fewer parts need replacing and even then, the cost of parts is less than gasoline generators
• Longevity – as long as the generator is maintained properly, users can expect years of use

Disadvantages of diesel generators

• High CO2 emissions –technologies have made strides in lessening diesel generators’ carbon footprint, but still have a long way to go
• Noise – Noise pollution can be high if measures aren’t taken to dampen the sound
• Weight – diesel generators are heavy and not easily moved
• Corrosion – must be kept in a dry place to prevent corrosion

 

At a glance: uses of generators

Generator types and working applications:

Portable	Kitchen appliances, home and job-site power tools
Inverter	Home medical devices, mobile phones, laptops, construction-site tools
Standby	Hospitals, medical centres, restaurants, commercial premises, manufacturing
Industrial	Robotics, lighting systems, manufacturing, computer centres

 

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