PacB Group // A Look at Large Generators


A Look at Large Generators

How large is a large generator? In 2015, the world’s largest internal combustion engine power plant was inaugurated at a site near Amman in Jordan. The plant is powered by 38 Wärtsilä 50DF multi-fuel engines with a combined capacity of 573 MW. In recognition of its world-record size, the plant was accepted into the Guinness book of records.

Large generators are typically powered with diesel or fuel oil but may also be powered by natural gas. Very large generators are classified in terms of their rotational velocity. Low-speed diesel engines run at roughly 200 RPMs and are typically two-stroke engines. Medium-speed models ramp up the rotational speed running at around the 800 RPM mark and utilize a four-stroke diesel combustion cycle.

Finally, high-speed diesel engines are capable of powering a drive shaft at or above 1200 RPMs. All the engines designed to run very large generators employ massively re-enforced engine blocks to cope with the huge power that they are capable of producing. In 2011, Kawasaki Heavy Industries, Ltd. delivered an 18 MW diesel power generator to the Okinawa Electric Power Company, Incorporated (OEPC). It was the world’s largest single, medium-speed diesel power generation system.

The generator is driven by a medium-speed, four-stroke diesel engine. Large generators in the high-speed range are produced by General Electric powered by diesel or gas in sizes up to 40 MW. Large generators are often paralleled to produce utility scale output. Wärtsilä supplied two 50 MW Smart Power Generation plants to an energy and services company in the United Kingdom where each plant was based on five Wärtsilä 34SG engines running on natural gas.

Large Generators is a Relative Concept 

Generators aimed at small commercial and residential users will typically range from 8 to 30 kW. These units are suitable for homes, small retail outlets, and offices. In this market, 40 kW units would be considered large generators. Gensets for large industrial and commercial entities would typically range from 8 kW up to 2,200 kW intended for use in office complexes, factories, and other industrial facilities. A 2,2 MW genset can be housed in a 12 m shipping container, including controls, fuel tank, electrical power distribution gear, and everything needed to operate the unit as a standalone power station or as a standby backup solution.

These units are referred to as power modules and are trailer based, so they can be moved from site to site. A combination of these modules can be used to create small power stations using from 1 to 20 units per section. Sections can be combined further to create utility scale installations that may employ hundreds of power modules. In these larger sizes, the power module (engine and generator) are brought to site on trailers and are then connected together to form a complete synchronized power plant. Compared to Kawasaki’s 18 MW behemoth single, 2,2 MW power modules seem not to qualify as very large generators. Size is very much relative to your point of reference.

Buying Single Large Generators as Opposed to Paralleling

Where power needs are substantial enough, the question becomes whether it is better to go with single large generators or split the burden between two or more smaller units. For example, instead of a single 1500 kW generator, three 500 kW gensets could be employed. This approach is known as paralleling and can be the preferred approach in the appropriate circumstances. Paralleling allows for greater flexibility. A single unit offers no redundancy. With multiple generators, if one fails or has to be shut down for maintenance, the load can be shifted to other units, allowing for operations to continue. It may also be more cost-effective. In most instances, once you reach a certain generator size, it becomes more economical to parallel smaller units than use a single unit. This corresponds with the point at which one exceeds the sizes of engines that are mass-produced for use in applications other than generators, such as trucks, earthmoving equipment, and ships. Truly massive engines are produced in relatively small quantities, so are harder to come by and more costly. The engine typically comprises more than half the cost of a generator, so keeping the engine cost as low as possible makes a lot of financial sense.

Large Generators – Which Fuel Type?

Diesel fuel is the traditional choice for commercial and industrial standby power but is by no means the only choice. Natural gas is also an option, but in the past, natural gas has been seen as less desirable in industrial applications. This was based on cost, power density, concerns over the effect on durability, and fuel supply reliability. The development of new technologies in engines, enclosures, and other generator components have made the differences between diesel and natural gas-powered units less clearly defined.

Diesel has historically had the following benefits over other fuels: Diesel is seen as a reliable fuel supply not subject to the risk of disruption in the supply pipeline. In addition, diesel generators typically cost less than natural gas units. Gensets that use diesel engines usually require less maintenance compared to other types of generators. Diesel is not nearly as flammable as other types of fuel, so it is reasonably safe to store and relatively easy to clean up in the event of a spill. Natural gas, on the other hand, does not require fuel storage.

Natural gas is fed through a pipe system, so is available when needed, barring any issue with the supply line. Natural gas is an extremely efficient fuel source and gas is one of the cleanest fossil fuels available. Natural gas burns cleanly with virtually odorless exhaust emissions. Natural gas gensets also tend to be much quieter than diesel units. Large generators running on natural gas typically cost more than their diesel counterparts, but the initial expense can be justifiable in some installations.

Making the Right Choices Requires Expertise

PacB Power Solutions is renowned in the industry as a manufacturer of superior-quality large generators. When it comes to specifying industrial diesel generators, significant technical know-how and experience are pre-requisites for purchasing and installing the correct solution. Generator sizing, fuel type, and configuration need to be thoroughly understood and matched to the customer’s site-specific conditions and requirements.

PacB will assist with the design and manufacture of any generator control systems, including various AMF (Automatic Mains Failure) and ATS (Automatic Transfer Switch) systems and all the additional components that the industry requires. We have expert knowledge and experience of all the main controller brands in the industry. PacB is able to design and manufacture Synchronous PLC controlled panels for multi-station generator supply over a vast range of sizes and voltages, including systems in excess of 1000 kVA.


Our qualified technicians offer support and advice in the selection of the right power solution for your needs by calculating your power requirements.

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