Speed regulation on generators: power without ups and downs

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Technical Article. Pic of a man operating a generator set.

What we demand of a generator is a stable power delivery. And a constant engine speed is crucial in achieving this.

The famous Swiss architect Le Corbusier said that machines are “a fantastic perfection tool”. However, experience tells us that even the most sophisticated machinery is not perfect. Although the mechanical systems are designed to be balanced and deliver based on optimal parameters, one must take into account that there are always some factors which can alter their efficiency.

The speed of an engine, for example, may be affected by a drop in voltage or by power surges. And, in the case of generators, such variations are of critical importance, given that the engine speed directly determines its operating frequency.

Logically, this can entail a problem, because the thing that interests us about a generator is that it be capable of maintaining the most stable power possible around a certain value.

The good news? Everything is foreseen and technology provides us with the solutions for the engines never to lose direction.

Regulating a solid response: generator speed control

At present, the engines powering electrical generators contain a speed regulator for speed control.

The function of this regulator is to detect any imbalance in the engine speed and to cause it to revert quickly to its optimal working regime.

Thanks to this device, our generator’s engine will always keep a constant rhythm. In this way, the generator will be capable of always complying with the requirements of the load, giving us the power that we need to obtain.

Moreover, the speed regulator acts as a security device, because it protects the engine from excessive speeds which can cause the engine to break down.

Genesal Energy: reliable engines

At GENESAL ENERGY, we offer you diesel generators equipped with three different types of governed engines:

  • Engines with mechanical controls
  • Engines with mechanical controls and inbuilt electronic controls
  • Electronic engines

All of these are designed to recuperate the working frequency, both after a load impact and after a sudden drop thereof.

The response to the drop in frequency will depend on:

  1. The inertia of the engine itself.
  2. The inertia of the alternator.
  3. The characteristics allowed by the installed AVR (Automatic Voltage Regulator).

At the same time, in the engines with mechanical speed regulation, we apply a parameter called “speed drop” or “droop”. This parameter represents the percentage of over-speeding that the engine is experiencing when it is operating without a load, compared to the nominal speed (at full load). Once we have calculated this, we can configure the engine so that it quickly stabilizes when a load is applied to it..

All regulators need a certain period of time in order to act. At GENESAL ENERGY, we carry out all the necessary adjustments and tests to ensure that the regulators control the engine speed and the generator frequency correctly. In this way, we give a reliable response to our clients’ requirements.

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How do variables affect the sizing of a generator?

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Analyzing the effect of voltage and frequency drops is indispensable for deciding which engines and alternators are more adequate for a generator.

Voltages are not a static phenomenon. They fluctuate resulting in peaks and drops during certain phases of the equipment’s functioning.

In fact, when we speak about circuits we distinguish between two types of situations:

  • The steady condition: It is the stationary situation of normal functioning in which the voltage ows in a balanced state according to the conditions determined by the network.
  • The transitional state: it occurs in certain periods of time in which the voltages and electrical intensities vary, before the circuit comes to its steady state and becomes stabilized.

The voltage variations occurring during these transitional periods are known as variables.

When do variables occur?

Logically, the normal situation in which variables occur is when we cause a circuit to pass from one condition to another, i.e. at the moment of connecting or disconnecting the equipment.

In fact, when we switch on and off a generator, short voltage peaks are triggered. Although they tend to end by themselves, we must not take them easily. Why is that? Because if the alternator and the engine happen not to be capable of coping with them, major functioning problems may ensue in the generator.

A matter of analysis

For this reason, in the process of designing and sizing a generator, it is indispensable to carry out a strict variable analysis.

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Technical article. Gas vs Diesel

Diesel and Gas Powered Generators: What is the difference?

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Technical article. Gas VS Diesel

The two most common generator types on the market are diesel engine powered generators and those using gas powered engines.

Apart from the fuel powering them, they have other distinctive qualities which make them more or less adequate according to the use we want to give them.

Let’s see what they are.

Diesel generators

The reliability of a classic

For quite a long time, diesel engine generators have been a standard in the market. Their good reputation was the result of a great flexibility of application, both in industrial and household areas, as well as their robustness and reliability.

This type of generator may be used as a main power supply, as well as for co-generation or emergency applications. They are fully autonomous and may, therefore, function in places which have absolutely no power-supplying networks.

What advantages have made diesel generators so popular?

  • They are more easily disassembled and installed than gas units, making their installation wherever needed a simpler task, while also using a fuel which is easily accessible and more economical than gasoline.
  • They are robust and sustainable, capable of ensuring many hours of yearly operation.
  • Diesel fuel gives high efficiency to the equipment using it because it burns at a much higher temperature than gasoline.
  • Diesel fuel is also very safe because it is less flammable than other types of fuel.

The main disadvantage of this type of generator, as in the case of any machinery which includes a diesel engine, is that it causes high levels of polluting gas emissions. Therefore, the present day diesel generators incorporate an additional antiparticle filtration system that ensures its conformity with the legislation in force.

Natural gas powered generators

Clean and economical energy

Gas engine generators have gained much popularity due to their great reliability, cost efficiency and sustainability.

This type of generator can be used as a primary power source, in co-generation applications or as an emergency source and its engine may be fuelled by liquefied natural gas (LNG) or liquefied petroleum gas (LPG). The latter is a gaseous fuel obtained from the distillation of oil.

Generators powered by LNG fuelled engines get their fuel from the natural gas distribution network, whereas LPG fuelled generators are connected to a tank which will have to be periodically refuelled.

What are the benefits of natural gas powered generators?

  • They are more respectful of the environment, because the gas causes less emission than other non-renewable fuels (such as coal, diesel or gasoline).
  • They are economical, because gas is the most affordable fuel, second only to coal (which is not an option due to its high emission level).
  • They are high-efficiency generators in co-generation applications.
  • When fuelled by an underground natural gas network, the fuel supply is not conditioned by inclement weather or problems with the communication infrastructure (which do condition diesel generators that need periodic refuelling).
  • They are highly compatible and easy-to-use units, given that it is possible to install them in remote locations, using high capacity tanks.
  • They are very quiet generators.

Among the disadvantages of this type of generator, one must consider the following:

  • Liquefied natural gas (LNG) powered generators are less autonomous than diesel engine ones because it is absolutely necessary to connect them to a distribution network.
  • In the case of LNG equipment connected to the network, one has to take into account that any catastrophe or natural disaster can affect the supply system.
  • Gas is an exceptionally flammable fuel and entails a bigger fire hazard than diesel.
  • The engine and control system are much more demanding, which can result in the product’s final price being higher.
  • They require a more punctual and complex maintenance.

Diesel vs Gas Generators?

Choosing one type of generator over the other is a decision which involves taking into account numerous variables, some of which are not always obvious.

At Genesal Energy, we advise our clients, offering them the solution which is most adequate to their projects.

For more information, please contact us at:

consultas@genesal.com +34 900 730 124

Dereating: how Temperature and Elevation Affect Generators

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Testing a generator derating ambient temperature

In certain environmental conditions, generators can suffer power losses. Preventing these will allow us to ensure the maximum efficiency of our equipment.

All engines and alternators are capable of offering 100% capacity when they operate in standard or not so demanding environmental conditions, but when they must function in environments with high ambient temperature or at a high elevation above sea level, their capacities may be reduced.

The engine manufacturers, for instance, usually guarantee a certain performance provided that some values are not exceeded (generally a temperature of 25ºC and 1000 m above sea level). If these values are exceeded, the user has to bear in mind that, very likely, the engine will not perform at its top capacity.

This loss of power in function of temperature and elevation is known as derating, and is something which has to be very much taken into account when it comes to sizing a generator.

Generator dreating in conditions of altitude

Just as it happens to us human beings as we climb higher above sea level, the lack of oxygen and the low pressure affect the performance of the generator.

Elevation affects all kinds of engines, but this effect is more prevalent in atmospheric engines, which depend upon atmospheric pressure for the air to reach the cylinders adequately.  These losses of power may even occur at elevations below 1000 meters.

In the case of turbo engines, the turbine is capable of countering this air deficit. Therefore, generally, the power derating of this type of engines starts to occur at an elevation of 1000 meters above sea level and its effect is inferior to that affecting atmospheric engines.

The alternator also suffers at a higher elevation, given that with less air it tends to overheat. In general, the majority of manufacturers guarantee that the alternators will not lose power until reaching 1000 meters above sea level. At higher values, the average loss of power is generally of 3% for 500 m of elevation.

Generator performance at high temperatures

Generally, temperature affects generator engines starting at 40ºC. Above this ambient temperature: 

  • The air is already very hot and its quality is no longer optimal to generate good combustion when mixed with fuel. This generates loss of power.
  • The fuel may reach the engine at an excessive temperature, and combustion will not take place in adequate conditions. 
  • The efficiency of the cooling system will be diminished. As a result, if the radiator is not correctly sized, the generator can stop functioning due to an excessive water temperature. 

Generator derating ambient temperature

As far as the alternator is concerned, it is also affected by high temperatures. The majority of manufacturers guarantee the power of their alternators, as long as they operate at an ambient temperature of below 40°C. At higher values, the derating in an alternator is generally of 3% for each additional 5º C.

The importance of having foresight

Given all of the above, when sizing a generator, it is crucial to have a clear understanding of the environmental conditions under which it will operate, i.e.: the inferior and superior limits of ambient temperature and barometric pressure in the setting-up location, as well as the elevation above sea level at which the equipment will be located. 

With this clear information provided, we, the engineers, shall be able to foresee and counter the effects of power derating, selecting the most adequate engines and alternators for each equipment.

If your project will be carried out in extraordinary environmental conditions, we at GENESAL ENERGY can advise you and size your generator in such a way that your ideas never lack power.

Risks and Consequences of Using Generator Sets at a Low Load

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Minimum load for generators

Generator sets are designed to work at their maximum power and their correct care and maintenance is, therefore, essential for them to function optimally. All the equipment must work at a minimum of 50% power load and their continued use at inferior percentages – that is to say at a low load – is counterproductive and may have serious consequences.

Main symptoms of something malfunctioning

One should be concerned when:

  1. The engine gives off oil mixed with fuel through the exhaust manifold – including the exhaust outlet or the muffler.
  2. There is oil spillage, dripping of oil of a very dark colour, as if burnt.
  3. The exhaust gives off a white smoke, more smoke than usual is seen or there is soot coming out of the exhaust outlet.
  4. The valves and tubing are clogged by dirt (presence of cinder).

Effects of low load running

“We saw engines working continuously for 24 hours at a tenth of their load and exhaust manifolds with six centimetre holes reduced to one centimetre by the accumulated cinder and oil”, Genesal Energy Technical Director Guillermo Docampo explains.

Negative effects of low load:

  1. Large accumulation of soot (cinder) in the pistons, in the grooves of the piston rings, in the valves and the turbocharger. If, subsequently, the engine functions at full load the pistons may be blocked by faulty lubrication.
  2. Low temperatures will result in insufficient combustion of the fuel, which, in turn, will cause the lubricating oil to be diluted and lose its properties because part of the fuel has mixed with the oil.
  3. Grinding of the cylinder liner. Excessive wear.
  4. The non-consumed fuel and the lubricating oil will also penetrate the exhaust manifold and will possibly exit through its seals, being very obvious -almost scandalous- because of its burnt aspect and by the stains it causes ((see photo below)).

Non-consumed fuel exiting through its seals

Why does low-load functioning in a repeated and continuous way cause an increase in oil consumption?

In reality, when an engine works at a low load, the ideal working temperature of the engine is not attained. This favours oil flow towards the upper part of the piston, because a correct adjustment within the piston-rings-cylinder assembly was not achieved. This is due to the lack of dilation resulting in an increased consumption of oil; the oil flows more easily between the valve guides and the stems due to a greater clearance because there was no sufficient warming.

How to prevent malfunctions? Is it possible to reduce the risks?

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The importance of the load profile and consumption of a generator set

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Technical article: load profile and consumption of a generator

Knowing the type of loads that we must power is vital in order to correctly determine the power rating of a generator set.

The power that a generator set manages isn’t an absolute and static value. Its level tends to fluctuate according to certain factors and processes, and it does so differently in each type of unit.

For this reason, calculating the power a generator set needs to function is not a simple operation. Different variables must be taken into account which, if not considered, can cause serious issues in our installation.

For instance, an overload in any of the phases can cause overheating and voltage imbalances. This can cause damage both in the generator set and the equipment connected to it.

Start-up: the first step load

The generator set is going to be limited during its start-up by what is called the first step load, that is: the total transient load that the genset is initially capable of enduring until reaching its stable regime with some transient variations in voltage and frequency.

This is why it’s important to verify the characteristics in the nameplates of the equipment connected to the generator set, and to be aware of the possible transient effects which they may suffer during its start-up processes. 

Certain equipment such as pumps or motors with variable drives, for instance, may increase their current temporarily during commissioning. 

Likewise, elements such as UPS’s (uninterruptable power supplies) can cause harmonic distortions which must be contemplated in our calculations.

Which parameters affect the dimensioning of loads? 

  1. The first parameter to contemplate is the type of load. As we’ve pointed out, some units experience transient increases in current during start-up. With this in mind, we’ll pay special attention to the following loads:
  • Uninterruptable power supplies (UPS). The alternator’s rated power is oversized depending on the installation.  
  • Big motor loads. They can increase starting power to up to 6 times the power, depending on the type of start-up.  
  • Lighting loads (with special attention to sodium vapour lighting and metal halides). 
  • Systems with Variable Frequency Drives (VFD). These can cause an oversizing from 40 to 100%. 
  • Other loads which are especially sensitive to transients and voltage and frequency variations. 
  1. Another factor we must keep in mind is the type of start-up of the motor in question. This is due to the fact that each type of starter requires a specific starting current, which must be higher than the unit’s rated current. Thus, we find that:
  • Electric motors with star-delta starting: its “starting current” will be equal to three times the rated or operating current. 
  • Direct starting motors: demand 6 times nominal current. 
  • Starter motors with variable frequency drives: special attention must be payed to its technical sheet as normally the ramp and increase in speed is configurable. 

Other important aspects to consider for genset load calculation

To finish carrying out this entire calculation of power with maximum precision, other variables must be kept in mind such as: 

  • Power factor during start-up.
  • Starter power.
  • Rated power factor.
  • Rated power
  • Efficiency
  • Number of start-ups

Ultimately, we must be extremely rigorous in this calculation. To avoid any surprises, it’s vital to know the type of load we’re dealing with as well as its behaviour. All, with the objective of the generator set always powering a balanced load, without generating unexpected peaks.

 

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10 Benefits of having a power generator set

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Technical article. 10 benefits of power generator sets

In a world increasingly dependent upon energy, technology and data, it is a priority to have a reliable and sustainable supply of electricity. This is precisely what generator sets offer us.

However, the virtues of these devices go beyond what meets the eye and it is worth knowing them. We compiled a list of 10 fundamental benefits so that none of them is left out:

What are the main advantatges of having a generator set?

1. Uninterrupted Power: The Importance of Ensuring Continuity

Electricity supply no matter what. Generator sets are meant for you to always have electricity whatever happens. This means that problems with the electrical network will no longer be critical for you, given that you will be constantly backed up by an autonomous generation solution which is 100% effective.

2. Say Goodbye to Downtime: Boosting Productivity

Farewell to losses: relying on the backup of a generator set in your business allows you to forget about time and productivity losses supposed by power blackouts.

3. Empowering Autonomy: Expanding Possibilities

More autonomy, more possibilities: when using an energy distribution solution such as a genset you are no longer dependent on the limitations imposed by the infrastructure of the electrical network. This means more peace of mind and, most of all, more freedom when it comes to conceiving your business projects and letting them fly.

4. Mobile Power Solutions: Enhancing Flexibility

It allows you more mobility: generator sets allow you to have a power supply in areas lacking an electrical network. Therefore, they eliminate obstacles when it comes to carrying out projects and they contribute to the development of remote or disadvantaged areas.

5. Tailored to Your Needs: Customized Designs

Your project is in charge: at present, the design of gensets is tailored to the clients’ needs and the features of their projects. According to your requirements, you will be able to choose: between engines using different fuels, between stationary or mobile generators, between hybrid and marine generators, as well as between different profiles of power delivery and of use.

6. Adding an Extra Layer of Protection: Ensuring Security

An additional security layer: the consequences of a power outage go beyond the mere issue of productivity. A sudden “blackout” can cause severe damage to our devices and machinery and this is something that can be avoided if we have the backup provided by an emergency genset.

7. Sustainable Energy: Reducing Environmental Impact

It contributes to sustainability: as opposed to the great impact left by the emissions produced by thermal power stations, generator sets offer a model of energy production which increasingly allows one to leave the least possible environmental footprint. The present-day trend is represented by generators using fuels with low CO2 emissions, like natural gas or liquefied petroleum gas (LPG). Moreover, these are low noise devices, producing no sound pollution.

8. Long-Term Value: Making a Sound Investment

It is an investment which pays off: A generator set will give you an extremely valuable service and will continue to do so for a long time. Most certainly, with appropriate use and maintenance, you will have a safe, long-term investment.

9. Streamlined Energy Production: Enhancing Efficiency

More efficient energy production: statistics show that electricity losses in the Spanish network of transport and distribution amount to 8% of all available production. Using distribution solutions such as gensets, one manages to reduce such losses. Moreover, we contribute to avoiding overloads in the network during the peak hours.

10. Cutting Costs: Maximizing Savings

You save in consumption: gensets allow you to reduce costs, by helping you manage the electricity demand in a more economical way. For example, you can use them as a backup during peak hours, in order to avoid excessive consumption. According to calculations, you can save up to 40% in this time slot.

 

In short, a generator set brings you peace of mind, opens up a large spectrum of business opportunities and all this in an effective and sustainable way.

Do you think it could be an interesting solution for you as well?

At Genesal Energy we have a wide experience in the design of personalized generator sets and we’re here to help you turn your project into reality.

 

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In a generator set, reliability is key

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Steps to choose the right generating set

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