When most people think of generators, they think of the big, noisy machines that emergency crews use to power lights and equipment during blackouts. But generators come in all shapes and sizes, and there’s a perfect one for every need and application.
In this post, we’ll discuss what a generator is, the different types of generators available on the market, and how to choose the best one for your needs. Happy shopping!
What is a Generator?
In its simplest form, a generator is a device that converts one type of energy into another. Electrical generators convert mechanical energy into electrical energy, while heat engines convert thermal energy into mechanical energy.
Generators are used to produce electric power or to provide an auxiliary power source for home equipment, camping, RVs, outdoor events, powering agricultural equipment such as drip irrigation systems or borewells, or powering smaller tools.
Methods of Classification of Generators
You can classify a generator in many ways – by operation, by quality, by fuel used, and by application. We will brief you about these classifications in this article, along with the major characteristics of each type of generator.
- Types of generators by operation – brushed, brushless, and inverter generators.
- Types of generators by quality – consumer, contractor/commercial, inverter, and bargain-basement generators.
- Types of generators by fuel burnt – gasoline, diesel, biodiesel, emulsified diesel, hydrogen, propane gas, natural gas, and solar-powered generators.
- Types of generators by application – portable, standby, induction, and inverter generators.
As you have seen, inverter generators feature in multiple classifications above. We will now familiarise you with the major properties and characteristics of each type of generator presented above.
Types of Generators by Operation
The Gensets fall into three groups by the method of operation as detailed below:
This category represents the older technology that still has the carbon brushes used in some of the oldest generators. Brushed generators are easy to repair by most DIY mechanics. Brushes need periodic replacement every 600 operating hours or so. They produce AC power with the sine wave fairly close to the grid wave.
These types of generators use electromagnetic induction instead of mechanical brushes to operate. Brushless generators weigh less than the brushed generators for the same power output, thus being more portable. All reputed manufacturers produce brushless machines.
This group is the most recent development made possible by the advancement in the field of power electronics, whereby more powerful permanent magnets and solid-state switches of higher current ratings are now available.
Inverter generators are very sophisticated in function but compact. The inverter generators operate at a speed that just satisfies the load requirements as against brushed and brushless machines, which invariably run at 3600 RPM.
Hence, they are more fuel-efficient, quieter, and more environmentally friendly despite their higher initial costs and lower capacities. Their circuitry is more complex than most DIY mechanics can handle.
These generators deliver AC power at a high voltage and high frequency, which is rectified to DC power, filtered to get rid of the ripples, and then inverted back to 60 Hz, AC clean power. The process ensure strict voltage and frequency regulation with Total Harmonic Distortion, orTHD less than 3% in most cases.
Types of Generators by Quality
The build quality of generators is an important aspect to consider because the generator is expected to last the blackout when the grid power breaks down. While some of the modern-day machines would make Thomas Edison proud, others may be hard-pressed to survive even a week-long power outage.
It is suggested to check out the consumer reviews of these machines on Amazon, Home Depot, and other large retailers. Use at construction sites and rental service is the Darwinian test for the fittest generators.
Warranties offered by the manufacturers provide important insight into the quality of the gensets. A two-year limited warranty is the normal industry standard, with some manufacturers even offering a higher duration warranty. A 90-day coverage is an immediate giveaway about the quality of the imports. More careful purchasers would even look at the manufacturers’ information on generator recalls.
Based on build quality, generators may be put into four broad groups:
These are mid-quality machines, available in all power ratings from large manufacturers.
Contractor / Commercial Generators
Generator sets in this category are the workhorses used in most construction sites and outdoor applications like movie sets. These models are favored by rental agencies due to their rugged build quality that can last under extreme operating conditions. Most of these units use brushes to operate.
These machines provide clean and distortion-free power for the digital Equipment. Though much more costly than conventional gensets, portable inverter generators find favor with homeowners with modest power requirements and campers. Inherent paralleing capability further adds to their utility.
As the name suggests, these generators have the price as their only recommendation and are not very good quality. The term’s literal meaning indicates a section of the store that sells merchandise at reduced prices. Many cynics will even suggest buying two units so that you have enough parts to keep one unit running.
These units may use copper alloy instead of pure copper windings with crimped connections instead of welded ones.
Types of Generators by Fuel Burnt
For most consumers, the first consideration while selecting a generator is the type of fuel it burns. Gensets can be powered by gasoline, biodiesel, emulsified diesel, propane, natural gas, solar power, and hydrogen. Some generator models allow you to switch between two fuel types (dual fuel) or three fuel types (tri-fuel). These bi-fuel or tri-fuel generators are also known as hybrid generators.
Common factors that influence the choice of any particular type of fuel include flammability, storage provisions, shelf life, cleanliness, availability during power outages, fuel efficiency, economics, reliability, unit cost, efficiency, and maintenance costs of the generator set.
All of the above factors will ultimately translate into
- Engine costs
- Fuel availability in normal and outage scenarios
- Environmental impacts
- Fuel system installation, storage, and operation costs.
- Personal safety and fire hazards.
- Impact on engine life and its wear and tear.
If you are using any fuel other than natural gas, you need to make some provisions for fuel storage. All gasoline stations will get closed during a blackout. Most outages result from accidents or routine maintenance and are short-term affairs lasting about 3-1/2 hours.
Outages due to extreme weather conditions like hurricanes, tornados, or ice storms are unique, and these events cause varying impacts on the generating and distribution systems depending on their vulnerability. The blackout may last anywhere from 6 to 15 days.
Let us now dive deep into different types of generators based on the fuel they burn.
Unleaded gasoline is a readily available fuel in the market. This makes it the most common choice among engine manufacturers. Availability in smaller capacities makes gasoline generators an ideal option for portable models.
However, you will not be able to store gasoline for the long term because it oxidizes quickly. Fuel stabilizers may extend the life to about one year. Gasoline is highly flammable, and you must store it in a shed that is some distance from your house. Never store it in the attached garage or the basement of your house. Needless to say, storing it in large quantities can be very hazardous. Gasoline is more expensive than other options like propane, natural gas, and diesel.
Look for an OSHA stamp of approval to guarantee the safety of the gasoline containers. These containers will hold up to 5 gallons of fuel and are provided with a spring-loaded lid, a provision for venting in case of fire, and a flame arresting screen.
As highlighted earlier, you may find it difficult to source gasoline if the grid power fails because it relies on electrical energy to pump. Other drawbacks of gasoline generators include relatively higher emissions, starting problems in cold temperatures, etc.
Diesel fuel is another readily available option like gasoline and the least flammable out of all. It is the most energy-rich fuel that is very safe to use and store. Many agencies carry out on-site diesel fuel delivery. It can be easily stored in 55-gallon drums for 18 to 24 months without additives.
Diesel fuel may not be available during power outages as it is difficult to pump diesel without power. But, it can be stored in large storage tanks if extended power outages are expected, and the cost is justifiable. Local regulations in many areas require double-walled construction for such tanks. You will find many options and products to combat diesel’s algae formation and oxidation problem. Diesel generators can operate in very cold environments with fuel additives.
Diesel generators have much longer life spans, even strenuous duty conditions, with an expected engine life of about 20,000 hours for liquid-cooled 1800 rpm engines and 10,000 to 15,000 hours for 3600 rpm engines. This, of course, is subject to proper and timely maintenance as per the manufacturer’s guidelines.
Though the initial cost of diesel generators is more than their gasoline counterparts, they are very affordable to operate. A 20 kW diesel generator may consume about 1.4 gallons each hour when running at full load. Diesel generators are designed for long continuous duties and give an efficient power output when you run them near their rated load.
Unlike gasoline counterparts, you should not run a diesel engine in dry condition while preparing for storage. It should have fuel in the lines, else you must carry out air purging from the entire fuel system before starting the engine.
Fuel injection pumps are very sensitive to the presence of water. So diesel engines require moisture-free and clean diesel fuels, and you should not refuel them in the rain. It is better to avoid installing a diesel generator in areas near lakes or rivers.
Diesel engine emissions are pretty high. Hence local authorities may impose certain restrictions in sensitive areas regarding the permitted number of hours of operation. Diesel engines produce much higher engine noise, necessitating well-designed sound restricting enclosures in residential and sensitive areas.
Diesel generator sets are much heavier, less portable, and require periodic maintenance by qualified technicians. You may face the issue of wet stacking if you run your diesel engine with less than 35% to 40% of the rated output of the generator set. You will get high levels of smoke from the generator engines, and they will appear to run rough. This is due to the fuel injectors getting carbonized.
The properties, advantages, and disadvantages of diesel and biodiesel fuels are quite similar to each other, with biodiesel machines being more eco-friendly than comparable diesel engines. Biodiesel is a liquid fuel that is created by mixing ordinary diesel fuel with natural and renewable sources like animal fats, recycled restaurant grease, or vegetable oils containing long-chain fatty acid esters.
Like diesel, biodiesel with blends up to B20 can be used in any internal combustion engine with no or very minor modifications. Biodiesel blends are designated by the percentage of biodiesel prefixed by the letter B, which means ‘B20‘ contains 20% biodiesel and 80% diesel. 100% biodiesel is referred to by the nomenclature B100. Some of the major features of biodiesel fuel are:
- Biodiesel is practically sulfur-free, resulting in reduced pollution.
- It has higher lubricity that reduces engine wear.
- It has a higher oxygen content resulting in fewer emissions.
- It is less toxic than diesel.
- Biodiesel may thicken or ‘gel up’ at lower temperatures faster than diesel. This poses a serious concern in cold areas. Blends with smaller biodiesel ratios will perform better in these conditions, although additives are normally used to counter these problems.
- It can oxidize with extended storage to form a semisolid gel. This will be a concern for standby generators operated very occasionally.
As you increase the blend, less amount of fossil fuel is used with much lower emissions. It may be unavailable during a power outage.
As is the case with biodiesel, the pros and cons of emulsified diesel are very similar to those of diesel fuel except for the following variations. Emulsified diesel is, in fact, formed by mixing the diesel with water that is already blended with the mixing agent that keeps the mixture together.
Emulsified diesel has a shelf life of 18 to 24 months, requires large storage tanks, and may not be available during power outages. On the positive side, it has fewer emissions due to a reduction in the quantity of fossil fuels used, is less flammable, and is easily obtained.
Obtaining and maintaining the correct water and diesel fuel ratio might pose a serious challenge.
Propane overcomes some of the shortcomings of gasoline and diesel fuels, like it possesses a longer shelf life, is the cleanest among all the fuel sources in the fossil fuel category, that can be stored in large tanks or smaller cylinders, and is available during power failures. 20-lb barbecue pit cylinders are very common, but you can purchase or lease larger storage tanks at a cheaper price.
Propane generators require less frequent oil changes, are more emission compliant, have lower engine noise levels, have no residues to clean in fuel lines and system parts, and do not suffer from wet stacking issues like their diesel counterparts. You can start these generators easily in areas with lower temperatures. These types of generators are available with air-cooled and liquid-cooled engines, with air-cooled versions being very affordable in terms of initial costs.
On the flip side, propane is stored in a pressurized cylinder that develops 200 psi pressure on a warm day. It is a flammable hydrocarbon gas that liquefies under high pressure. Though propane is an explosive gas, propane cylinder explosions are actually quite rare.
Propane cylinders are made from welded steel, and are always mounted upright to ensure the discharge of vapor instead of liquid propane. The cylinders have a service valve to connect to the generator with a 300 psi hose and a relive valve to vent any excessive pressure.
They must be inspected visually by qualified personnel 12 years after manufacture. A regulator reduces the line pressure to a value the engine can tolerate. This complex system is more expensive, with a higher installation cost and more frequent failures.
Generators with propane engines have a shorter life expectancy than engines with other fuel sources like gasoline or diesel. Engine life may be in the range of 5000 hours for 1800 rpm liquid-cooled machines. The life expectancy of air-cooled propane engines is much shorter than diesel engines.
Propane has a lower energy density which translates into much higher fuel consumption in gallons to generate electric power for the same load pattern. Though the cost per gallon for propane is lower than gasoline and diesel, the operating fuel costs are much higher.
Natural Gas Generators
Natural gas generators can be easily adapted to run on propane or gasoline. Except during an earthquake or the pumping station floods, natural gas is readily available when you need it. You need to lay natural gas lines up to the generators so these machines never run out of fuel. Due to this fixed piping network, they cannot be classified as portable generators. The gas lines result in much higher installation costs for the system.
The various advantages of natural gas generators include unlimited fuel supply, environmental friendliness, reduced engine noise levels, lower emissions, no odor, no waste, can start easily in cold conditions, and no wet stacking like diesel engines. They can be used as both standby generators and prime power generators.
Natural gas supplies vary in quality. So you need to verify that the water and delivery pressure are compatible with your engine operation. A damaged gas pipeline is very explosive and may lead to a fire hazard.
Natural gas generators are less expensive in smaller sizes in comparison to diesel units. But they have a shorter life expectancy and start becoming costlier for higher ratings. In addition, they have higher installation and maintenance costs. However, natural gas as a fuel is cheaper than diesel.
Solar generators are ideal if you want to go completely green, particularly for off-grid applications with limited power requirements. Their portability and ease of use make them an excellent choice for providing extra energy on the move, powering smaller tools, or minimal essential devices during blackouts. They are not suitable to power an entire home due to limitations in capacity, higher charging times, and being dependent on the weather conditions.
The solar generators use solar panels to capture the solar energy, which is then used to charge the generator’s batteries. This stored energy is converted into AC power by inverters present in the solar generator. The charge controller manages the charging process of the batteries.
As these generators rely on solar energy for their operation, there are no fuel costs and harmful emissions associated with them. However, their high initial and maintenance costs.
Hydrogen generators, like their solar counterparts, have a non-toxic fuel without any emissions that produce more energy per unit weight than any other fuel source. Hydrogen is extremely abundant in sources like water.
The high electric power output from hydrogen generators makes them suitable for feeding power to laboratories, large homes, refrigerators, and air conditioners. You can maintain them at a much lower cost, and they are quite rugged to handle. They can be provided with the required safety features to make them portable and safe to operate.
The disadvantages of hydrogen generators include the high initial costs, trouble in operation during cold seasons due to freezing of water at those temperatures and less availability.
Different Types Of Generators by Application
Any portable device is intended to be moved from place to place and used only when needed. The same is true with portable generators. Portable generators, also known as the Gensets, provide temporary electrical power in the absence of grid power. A portable generator can range from 0.5 kW to 17 kW capacity and comes with varying power configurations suitable for various usages.
The smaller rated units can be carried and shifted by hand, while larger units are usually provided with wheels. Hence the term portable generators are used to describe them. The bigger units can provide power to an entire home. But, portable generators in the range of 5 to 8 kW can power up all the essential requirements.
Generators for the American market produce AC power at 60 Hz frequency and at 50 Hz in many other parts of the world. Medium and mid-sized Gensets produce electric energy at both 120 V AC and 240 V AC to power electrical appliances such as air conditioners, clothes dryers, and well pumps. Generators from many manufacturers also produce DC power at 12 V for battery charging purposes.
However, this DC power is too dirty to be used for computers and other electronic devices.
It is usually kept in a storage place indoors, moved out during a power failure, filled up, manually started to produce electricity, and connected to your loads. It is very common to see extension cords running from a portable generator through the open windows and doors to the standalone cord and plug equipment like a window AC or a refrigerator.
Gasoline and diesel portable generators have an onboard tank to fuel the engines. You may need to refuel your portable generator multiple times daily if you operate it continuously. Portable generators do not require installation to be carried out by professionals but must be installed outdoors only as gasoline generators produce poisonous carbon monoxide gas vapors.
Prepare a protective canopy if you want to use them during snow or rain, as most grid power breaks happen during winters.
The simplest way to connect portable generators during power failures is through cords. But hardwired equipment to your home, like built-in lights, the boiler will not receive electrical power by this method. You may need to disconnect such hardwired devices from the building wiring individually using the cords and wire them back when the permanent power resumes. The process will have to be repeated every time you want to use your portable.
A better and safer method is to use a device called a power transfer switch. The transfer switch ensures that selected loads receive electric power isolating them from the dead grid lines simultaneously. A transfer switch requires a permit from your electricity company and, once installed, allows you to hook up your portable to the inlet via a special generator cable and turn the knob of the switch from Line to Generator.
Standby generators can provide power output if you have a fuel supply. They are installed near your house and connected to the transfer panel, which is also connected to the utility line and your home wiring.
Standby generators can use the fuel source that you are using to heat your house – natural gas, propane, or diesel. As the fixed system is always connected to the house wiring and the fuel source, it offers a fully automatic operation without needing to refuel. This is achieved through the use of an automatic transfer switch which takes about 10 to 30 seconds to transfer the loads from the utility power to the standby generator.
On the restoration of the grid voltage, the system will connect you back so that the loads receive electric power again from the utility lines. Standby generators require professional installation and permit approvals from the electric and fuel utilities. The cost of installation for a standby generator system with the automatic transfer may vary from $6,000 to $12,000, including the charges for electrical wiring and fuel hook-up.
You were already introduced to inverter generators in our section on different types of generators by operation. The main difference with the conventional generator lies in the fact that an inverter generator engine speed adjusts up or down to match the load demand, unlike the conventional one, which continues to run at full speed at all times. This results in lower fuel consumption and lower emissions.
An inverter is a device that converts DC power to AC electronically. Hence, an inverter generator first converts the generated AC power to DC and then inverts it to finally deliver AC power that is much cleaner and suitable for sensitive electronic components.
A portable inverter produces an alternating current of variable frequency in line with the engine speed with higher speeds resulting in more current and higher frequencies. The rectifier circuit in the generator transforms it to produce DC power which is inverted back to have clean and steady electric power at 60 Hz frequency. This also results in much less noise than conventional generator engines.
Induction generators are also known as asynchronous generators. These are basically induction machines with rotors running at more than the synchronous speed of the machine. The induction generators are more rugged and require no communicators and brushes. They are useful due to their ability to produce useful power at varying rotor speeds in applications such as wind turbines. However, on the flip side, they consume much reactive power.
The induction generators are of two types – the self-excited generators and the externally excited generators.
The externally excited generators take reactive power from the grid and supply active power back to the line. This active power is proportional to the speed of the machine above the synchronous speed. The externally excited generators find their applications in regenerative braking applications needed in equipment like electric locomotives, elevators, cranes, and hoists.
Self-excited generators derive the reactive power for their operation from a capacitor bank connected to the stator terminals. The self-excited generators find their major application in producing electricity in windmills, paper mills, and water companies.
We hope that we have successfully guided you about different types of generators with their advantages and disadvantages and that you are ready to make your choice. If we have missed something or you have certain questions to ask, write in the comments section, and we will get back to you.