AN OVERVIEW OF DIESEL GENERATORS

INTRODUCTION

When it comes to generators, there are a lot of options on the market. Different fuel types, different sizes, different power outputs … it can be difficult to know which one is right for your needs. Let’s take a close look at diesel generators and see how they compare to petrol. We’ll cover topics like fuel efficiency, maintenance, and overall cost of ownership. By the time you’re finished reading, you’ll have a much better idea of whether a diesel generator is the right choice for your business. We hope you enjoy this overview of diesel generators.

COMMON USE CASES

Throughout the UK, generators are put to diverse uses. Here are a few examples:

Commercial and industrial. Manufacturers and industrial operations need both continual power off-site and in many cases backup power on-site in case main power fails.

Data centres. The UK’s data centre is booming, as we continue to digitise our economy. Whilst data centres normally operate by mains power, continual availability of power is essential, and built into data centre’s service level agreements. So standby, backup and Uninterruptible Power Supplies are used to ensure continual supply of electricity.

Utilities such as gas and water are a source of power themselves but harnessing and supplying these utilities requires equipment. The UK’s utilities industries are one of the biggest users of diesel generators.

Construction. Construction projects are usually situated where there is little or no available power infrastructure. Building roads, railways and critical infrastructure requires on-site diesel generators to power equipment and lighting.

Education. Institutions such as universities, colleges and schools require continual, reliable power to keep the lights on and the computer networks humming. Standby generators are often used to cover power outages whilst Uninterruptible Power Supplies are used to ensure digital devices do not power down unexpectedly.

Healthcare. Hospital, nursing homes, and healthcare facilities require 24/7/365 power for heating, lighting and essential equipment. Standby and backup generators are almost always present in healthcare institutions to ensure patient care is never put at risk.

Defence and military. Whether at home or abroad, in training or in real-life engagements, military personnel working in the field need power in places where it is not available from the grid. The UK’s military and defence organisations are one of the biggest users of diesel generators.

Events. From sporting events, to fairs and fetes, gigs and festivals, events are happening all over the UK but often outdoors and away from urban infrastructure. So, diesel generators play a critical role in providing the entertainment we love.

HOW DOES A DIESEL GENERATOR WORK?

Generators are amazing machines. They convert fuel – a chemical concoction – into electrical power. This power can then be used to power anything from lights, to machinery, to heating units, and more. Over the years we’ve found ways to make more and more efficient at converting fuel to electricity, and exciting new developments in sustainable fuel sources mean than in future they will become more environmentally friendly as well as useful.

HOW THE GENERATOR WORKS

At a high level, here’s how it works. A generator engine converts diesel fuel to mechanical energy. This mechanical energy rotates a crankshaft within the engine. The crankshaft is a rod which converts the up-down movement of pistons into rotational movement. This rotational energy is used to produce an electrical voltage via an alternator. Once the electrical energy is produced, it can be distributed out from the generator to connected equipment.

THE ENGINE

The engine consists of several cylinders (usually four or six) which house pistons. The pistons are set up in line with each and each connected to the same crankshaft.

Fuel is introduced into each cylinder and ignited. This explosion forces the piston to move. As each piston is connected to the crankshaft, the pistons rotate the crankshaft at high speed. The crankshaft converts the up-down movement of the pistons into horizontal rotational movement.

At WBPS, the generators we sell can have engines manufactured by well-known makers such as Badouin, Doosan etc.

THE ALTERNATOR

The rotating crankshaft transmits mechanical power to the alternator. The job of the alternator is to convert mechanical power to electrical energy in a process called magnetic induction.

Magnetic induction happens when a conductive material such as a copper wire passes through a magnetic field and voltage is produced. If the wire is connected in a complete circuit, power can be transmitted. This process was discovered by Michael Faraday in 1831.

Two of the main parts of the alternator are the stator and the rotor.

The stator contains copper coils wound into the alternator’s outer casing. The rotor also has wire coils wrapped around an iron core, but unlike the stator it is attached to the engine crankshaft, so it rotates with the engine. When voltage passes through the rotor coils it creates an electromagnetic field. As the rotor spins its magnetic field cuts across the stator’s conductive wiring and generates voltage.

Because the magnetic field builds and subsides, voltage fluctuates between positive and negative peaks. This generates what’s known as alternating current (AC). The stronger the field, the higher the peaks.

Consistent voltage levels are needed to power most equipment. So, an automatic voltage regulator or AVR adjusts the magnetic fields as needed. When power demand is heavy the voltage decreases, causing the AVR to increase the magnetic field. And when power demands are low, the AVR tempers the field.

SINGLE PHASE AND 3-PHASE POWER

Depending on the generator make and model, the generator may produce single phase or 3-phase power. Single phase power is generated when a single AC wave is used. These generators are generally cheaper but the power they produce can be lower and less consistent.

A 3-phase generator provides 3 voltage sources, or phases, from the same alternator. The sources can be connected in series for high voltage applications, or in parallel for low voltage needs. Although generally more expensive, 3-phase power can be more consistent, and a higher voltage can be produced.

GETTING POWER FROM THE GENERATOR TO THE EQUIPMENT

Power is delivered from the generator to a control panel. The control panel allows the operator to select a desired voltage. Power flows through a protective device called a circuit breaker. If current exceeds capacity, the breaker stops the power from flowing. This protects the generator from surges which could damage connected equipment.

The generator owner can attach power cables to the generator’s terminal board. Thus transforming electrical energy into light, heat or motion, providing the power we rely on every day.

ARE DIESEL GENERATORS DANGEROUS

A frequently asked question is whether diesel generators are dangerous. It’s a legitimate concern as we are all responsible for the health and safety of our colleagues, customers or neighbours.

If diesel generators are used in the correct way and within their specified ranges of operation, then of course they are perfectly safe and can provide safe, efficient power for many years with no concerns.

Nevertheless, we’re dealing with fuel, electricity, moving parts, noise and exhaust. So, any generator must be treated with due respect. Let’s look at some of the potential hazards, and how they are mitigated in modern, safe diesel power generators.

FUEL

Diesel fuel itself can give off noxious fumes which can cause dizziness and headaches. It must be stored and moved around in dedicated fuel storage tanks.

The generator itself emits exhaust which can contain fumes which are hazardous to health. Diesel exhaust systems must be properly designed and installed professionally to ensure the risk is removed.

NOISE

Other hazards include noise. Larger generators can emit a lot of noise due to the many moving parts and internal combustion. However, diesel generator noise can be reduced with the use of acoustic enclosures and canopies.

When using a generator, always follow the manufacturer’s instructions. Larger generators will require professional training and handover, which happens as part of the generator commissioning process, before they can be used.

SMALLER GENERATORS

Again, with smaller and portable generators, safety guidelines must be followed to ensure they can be used safely. They emit carbon monoxide as part of the exhaust. Carbon monoxide is a hidden hazard as it cannot be seen or smelled.

To avoid risk, never use a portable generator indoors (including in garages, sheds etc.) even if ventilated. Remember that carbon monoxide can linger for hours after the generator is switched off.

Even when using outdoors, make sure to keep it away from windows and doors to avoid carbon monoxide poisoning.

Always refuel the generator outside, and never store fuel near the generator.

ELECTRICAL SAFETY

As with all electrical appliances, there’s a risk of electric shock if not used correctly.

This is particularly acute when using a generator outdoors in wet conditions. The generator should be protected from wet, but again – never situated indoors. It should be placed under a canopy and in a position where water can run away from underneath it without puddling or pooling.

Don’t touch the generator with wet hands.

CABLING

Generators have cabling that’s specially designed to be used with generators. You should never try to convey power from a generator without using a cable made specifically for the purpose. You should check the quality of the cable and make sure it is free of breaks and cuts. When laying the cables, they should be placed under cable protectors. If fed through windows or doorways you should check that there’s no risk of the cable being snagged, pinched or crushed.

ARE GENERATORS NOISY?

REDUCING GENERATOR NOISE

Both diesel and petrol generators inevitably make some noise. In noise-sensitive environments, we naturally want to keep this to a minimum. But what can be done to reduce generator noise or even create a silent generator?

Sometimes it’s vital to maintain an environment that’s as free of noise as possible. For example, in hospitals or educational establishments, where generators are situated near people, noise must be kept to a minimum. On construction sites where building is taking place in residential areas, noise is also a concern. Often a project will have specific requirements to reduce noise to specified levels.

Noise is an environmental nuisance because it can cause hearing damage, sleep disturbance and mental stress. In some cases, it may also be a safety hazard. There are similar concerns around vibration.

Noise is measured in decibels (dB). Decibels are logarithmic, which means that 80db is MUCH louder than 70db than 70db is to 60db.

Fortunately, generator noise can be reduced from anywhere between 15dB to up to 50dB, a very significant reduction, using a range of noise reduction techniques. This will allow nearby staff and residents to live in as noise-free an environment as possible.

WHY ARE GENERATORS SO NOISY?

Generators make noise because the engine needs to suck in a mixture of air and fuel, and then compress it before igniting it. This process naturally produces noise and vibration. As well as explosions, your generator also contains moving pistons and crankshafts. These moving parts of the engine can be quite noisy. This applies to both petrol and diesel generators.

SILENCING GENERATORS

There are a few approaches to reducing generator noise. The most obvious is to site the machine as far away from people and homes as possible. However, this is not always possible or practical – for example on inner-city construction sites or in hospitals or data centres.

Another way to reduce noise from a diesel generator is to fit it with a silencer. This works by reflecting some of the noise back into the engine, where it is absorbed.

In particularly noise-sensitive situations diesel generators can also be fitted with an acoustic enclosure. This is a box that surrounds the generator and has special sound-absorbing materials fitted to the inside. Acoustic enclosures are typically custom-made because they need to fit both the generator and the space it’s housed in. The acoustic enclosure completely houses the generator set.

At WBPS we are often asked to customise the enclosure by installing fuel supply pipework, emissions treatments and exhaust silencers. We are also sometimes asked to paint the enclosure to match the surroundings or corporate colours of the client.

Acoustic canopies are usually installed where space is at a premium. They are often installed by lifting the canopy over the generator set.

Sound attenuation consists of attenuators fitted to inlets and outlets of the generator set, plus silencers fitted to exhaust systems.

ADDITIONAL BENEFITS

As well as reducing noise, acoustic enclosures often come with the additional benefit of being able to reduce vibration, stabilise the temperature around the generator set, and reduce the risk of fire.

VIBRATION REDUCTION

For smaller generators, a way to reduce vibration is to mount the generator on springs or rubber mounts. This helps to isolate the source of the vibration and absorb some of the noise. For larger generator sets, they will generally be mounted on custom built concrete mountings with fixings into the floor.

Noise is measured in decibels (dB) – more accurately described as the intensity of sound. Because decibels are on a logarithmic scale, an increase from 70dB to 80db is much greater than an increase from 60dB to 70dB.

At WBPS we recognise that noise must be reduced wherever possible and practical. Using a combination of high-quality generator sets, silencers, mufflers, acoustic canopies and enclosures, we can reduce the noise emitted by the generator by a significant degree.