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The Origins of Diesel Generators

Diesel Generators – the Origins

The first practical and reliable electricity-generation devices were developed and produced by Charles Brush, an American engineer and inventor improving on earlier dynamo designs by making smaller, more efficient, and less costly devices. His machines were initially employed in cities to power streetlights but later by utility companies that sold electricity to a number of end users via a distribution network. The units were steam powered and produced direct current output. The first hydro-powered electricity in America was generated using one of Brush’s machines.

The invention of the internal combustion engine and a steady development of the concept led to the introduction of the first compressed charge, compression ignition engine by a German engineer, Rudolf Diesel, in 1892. From the early 1900s, generators became more and more common and were produced to be powered by steam engines, natural gas engines, and liquid fuel internal combustion engines. General Electric, Siemens, and Westinghouse, among others, offered units of various capacities, from units capable of powering an entire village to small units for individual homes.

Modern Diesel Generators

In essence, generators consist of an engine, a fuel tank, a voltage regulator, some form of engine speed control, and a starting mechanism, typically a battery and starter motor. Early designs consisted of two distinct components. Firstly, the dynamo, in the case of direct current output machines, or alternator, in the case of alternating current output units, and a separate engine that powered them. Modern generators as we now know them are an integrated design, called an engine-generator or genset. These units incorporate the engine into the generator to form an individual, unitary machine.

Diesel generators are the most commonly encountered machines today, especially in the larger capacity units. These generators are ubiquitous where grid power is absent or unreliable and come in a vast variety of sizes and configurations. These gensets are also found where continuity of supply is critical, for example, at medical and communications facilities where they provide backup in the event of grid failure. They are not the only option, however, generators can be powered with petrol or some other combustible fuel source, such as piped natural gas, for instance, or propane.

Alternative Fuel Types?

Diesel generators have a number of similarities to petrol, propane, and natural-gas-powered units. They all have similar general benefits and positive attributes. They are all proven technologies that run reliably in a wide range of ambient temperatures. Fuel is easily sourced and similarly priced and produces relatively low emissions. Whether powered by the heavier liquid fuels, petrol, or gas, the units cope well with start/stop loads and provide rapid on-demand power. Given the above, why are diesel generators generally considered to be better than the alternatives, especially the commonly found petrol-powered units?

The key differentiator between diesel generators and petrol units is that the former are far more fuel efficient. Although diesel fuel has around 45,5 MJ/kg (mega joules per kilogram) of energy, which is slightly lower than petrol (45,8 MJ/kg), it is denser than petrol which gives it around 15% more energy by volume. In addition to the difference in energy density, the overall efficiency of diesel generators is around 20% better than petrol units. In short, you get more power out of a litre of diesel than you do out of a litre of petrol. This fact makes diesel generators a far better solution for the provision of primary power where the genset has to run continuously.

Additional Reasons Why Diesel Generators Are Superior

These generators generally last longer than petrol-powered units and require less maintenance. They are mechanically simpler because they do not need an ignition system. The “oilier” nature of the fuel helps with engine lubrication, improving engine longevity. They also produce more torque than petrol engines do, and so, produce power at lower engine revolutions than their petrol counterparts, reducing engine wear.

Fuel combustion temperatures are also lower than in petrol engines. All these characteristics allow diesel generators to produce power with less stress on the engine component, which makes them more suitable for continuous running at high loads than petrol-powered units.

Diesel fuel has a longer shelf life than petrol. Under good conditions, it remains usable for between six to twelve months without the addition of any additives. In contrast, petrol only has a shelf life of around three months, which means that it must be used two to four times more quickly. Petrol is also substantially more flammable, which makes fuel storage more onerous for petrol. Diesel is generally a safer option with less chance of accidental ignition and fire.

Why are There Petrol-Powered Generators at All?

In the light of the many advantages of diesel generators, why are there so many petrol-powered gensets available in the marketplace? Firstly, and most importantly, small capacity petrol-powered gensets are usually substantially cheaper than an equivalent-size diesel generator. Diesel generators are also built more robustly, which makes them heavier and therefore less easily portable than a petrol unit.

It is also easier and more cost effective to build very small-capacity petrol engines, so petrol-powered units are readily available in sizes down to as small as units producing 650 watts. Diesel machines produce more toxic emissions than petrol units do and do not run as quietly as petrol-powered machines. At the small capacity end of the market, diesel generators do not offer the range of options that petrol-powered units come in.

How Do You Choose?

If price is the major consideration, and a small-capacity unit is all that is required, a petrol-powered machine will probably be the best choice for you. This is especially true if a very lightweight, easily portable machine is what you are looking for. It is not easy to find diesel machines smaller than 2kW in size. Where a larger unit for a more demanding environment is needed, a diesel generator is definitely going to be the best choice. If commercial- or industrial-sized units are required, this will invariably limit you to a range of generators.

The larger the capacity required, the more likely this will be. Utility-size gensets will invariably be powered by the heavy liquid fuels and not by petrol. Larger commercial and industrial generators should be sourced from specialist manufacturers like PacB. They are not a retail proposition like a small petrol unit is but require skilled professionals to size, specify, and install correctly. These skills come from years of experience in the generator field.