Engines — the key driver of the energy transition


What are the differences between reciprocating internal combustion engines and aeroderivative gas turbines?

Although both power generation technologies are considered flexible, reciprocating internal combustion engines have been proven to start and stop quickly, adjust power rapidly, and operate efficiently at various loads when compared to aeroderivative gas turbines (aeros). To put it another way, engines are more flexible.

As power systems worldwide are transitioning towards 100% renewable energy, the output of variable renewable energy sources is rapidly increasing. This variability is a challenge for power systems, causing the need for flexibility in power generation.

That’s why we believe flexibility is key! Our engine power plants provide future-proof energy solutions with outstanding flexibility and efficiency.

At Wärtsilä, we want to ensure that our engines run efficiently and reliably regardless of which fuel becomes the leading choice. Whatever the future holds, our engines will be able to handle it — so you can invest confidently in a more sustainable future today.

Three reasons engines are driving the energy transition

In this article, you will learn why and how engines alone can provide the indispensable flexibility needed to keep the grid stable and our power supply reliable while accelerating the energy transition and mitigating climate change.

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There are significant differences in the actual capabilities of addressing the variability of renewables even among so-called flexible power generating technologies. South Australia’s power system is an excellent example of a grid with a high proportion of renewables. We gathered real-world data from the South Australia’s National Electricity Market to show how two power generation technologies, engines and aeros, behave as a part of the power system.

In the animation video below, we demonstrate the exceptional flexibility that engine power plants provide in balancing renewables. There is now clear evidence that engines are dispatched much more frequently and earlier than aeros. We can also see how the engines provide continuous balancing of renewables on a minute-by-minute basis.

See the flexibility of engine power plants in action

This visual case study, based on real-world data from South Australia's national electricity market, showcases the engine power plant's unmatched flexibility when comparing to an aeroderivative gas turbine power plant in full operation.

Understanding the six elements of flexibility

To ensure reliable power supply, high-renewable power systems require balancing power plants that we can always count on to provide exactly the right amount of electricity output as and when needed. No more, no less. Too little output, and we suffer power outages; too much, and we damage the grid.

What we need are flexible or dispatchable power plants. The dispatchability of a power plant is determined by how fast it can start up and reach full load, how short the minimum up and down times are, how low the minimum stable load is, and plant net efficiency. Essentially, dispatchability amounts to how fast and efficiently a power plant can adjust its output; the faster and more effectively it can adjust its output, the better it will be at enabling the integration of renewables into the grid.

Infographic comparing internal combustion engines against aeroderivative gas turbines for power generation.

Learn what makes power generation technology truly flexible. After reading, you'll know what are the most important factors to consider when choosing the optimal capacity for your power plant.

Engine technology is optimal in driving the energy transition

1. Unlimited cycles every day

In order to balance the grid, power plants must be able to switch on and off quickly throughout the day. Unlike aeroderivative gas turbines, which have limitations on operational times as well as the number of times they can go on and offline during the day, reciprocating internal combustion engine power plants can perform an unlimited number of cycles without the need for additional maintenance. This is possible thanks to engine power plants’ short start-up time, near-zero minimum up and downtime, as well as rapid ramp rate. That is to say, their unmatched flexibility.

2. Efficiency at partial loads

When emissions compliance is taken into account, engine power plants are more efficient than gas turbines even at partial loads. That is because they can operate with as little as 10% load, making them ideal for spinning reserve markets. Engine power plants, which typically consist of multiple independent units, are capable of maintaining high efficiency while meeting changes in demand by selectively shutting down individual engines and quickly adjusting the load. Because of their higher minimum load and cycling restrictions, gas turbines are unable to increase their output incrementally from 1% to 100%.

3. Resilient performance in real-world conditions

Because ambient conditions can derate the net efficiency of gas turbine power plants, it’s important to note that real world conditions differ from ideal conditions. Humidity and heat have less or no of an impact on engine power plants. In fact, they can maintain their efficiency and power output under more extreme conditions. For example, even at 45 degrees, Wärtsilä engines can maintain over 45% efficiency. This resilience is especially important as heat impacts efficiency more when plants operate at partial load. The ability of Wärtsilä power plants to overcome ambient challenges demonstrates their wide range of operational flexibility and reliable performance.

Engines are competitive on greenhouse gas (GHG) emissions

Engine power plants emit fewer greenhouse gas emissions than gas turbine power plants. This is partially because they are highly efficient, especially when running plants at 100% load, 25˚C temperature, 30% relative humidity, and consider methane’s global warming potential over 100 years.

Graph comparing CO2eq emissions from engines vs aeros.

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Any information including facts, opinions or quotations, may be condensed or summarised and is expressed as of the date of writing and are based on publicly available sources believed to be reliable. The information may change without notice and Wärtsilä is under no obligation to ensure that such updates are brought to your attention.