The increased reliance on renewable forms of energy makes it more important than ever to identify energy sources that can efficiently supplement the variable output and available peak load capacities of such renewable sources like wind and solar power generation. Of the various options, reciprocating internal combustion engines are an ideal choice because they represent a decentralized, flexible, and reliable source for power generation. Reciprocating engines represent one of the more mature technologies used for power generation and play a critical role in numerous other industrial, commercial, and institutional applications. Originally developed in the 19th century, the most significant improvements occurred in the past three decades, driven by economic and environmental pressures for power density improvements (more output per unit of engine displacement), increased fuel efficiency, and reduced emissions.
Reciprocating engines have proven especially beneficial in producing peaking power to supplement renewable sources, such as wind and solar energy, during high demand periods. In today’s dynamic energy industry, there is a greater need for flexible, efficient electricity generation. No longer can we predict peak demand patterns. As wind and solar energy sources achieve greater market penetration, their intermittent energy supplies present challenges to operators trying to balance loads and maintain frequencies.
Download our white paper Reciprocating Engines: A Mature Technology that Is Proving Especially Relevant in Today’s Energy Environment to learn why reciprocating engines are the optimal peak power producers and best practices for maintaining performance.
Critical attributes for power generation
Reciprocating engine plants are well suited for flexible peaking and intermediate generation needs in the 20-300 MW output range. They offer competitive heat rates and multi-shaft reliability to compete in energy markets, plus industry-leading ramp rates and startup times to compete in ancillary services markets. These are critical attributes since these engines when powered by diesel fuel, are increasingly being used for emergency standby or limited duty-cycle service because of tighter emission standards and the relatively higher cost of fuel. Dual-fuel and gas-fueled reciprocating engines represent the engines of choice for the higher duty cycle stationary power market.
Ongoing improvements in efficiency, cost, emissions reduction, and usage of advanced fuel and/or hydrogen will ensure that reciprocating engines continue to remain viable and competitive with newer technologies such as fuel cells and microturbines in the distributed generation market. Their increased usage is also a result of newer configurations, involving the installation of multiple large engines, which make them competitive even in power generation applications of 200 MW or more.
Reaping the rewards of a preferred intermittent power source
There are several reasons why reciprocating engines are the ideal peak power producers, including:
Reliability- When operated and maintained according to manufacturer recommendations, modern reciprocating engines commonly exhibit availability factors of 95% or better.
Quick response- Reciprocating engines can start-up and ramp load more quickly than most gas turbines.
Efficiency- Reciprocating engines are very efficient, especially when incorporated into combined heat and power schemes (CHP) over a wide range of loads.
Versatility- These units can adapt to many industries and can be run on a variety of liquid and gaseous fuels, biofuels, and biogases, as well as carbon-neutral synthetic fuels.
Low water usage- Power plants using internal combustion engines tend to require significantly less water than similarly sized combined-cycle or simple-cycle natural gas turbine plants, resulting in cost savings.
Despite all their benefits, reciprocating engines are not without their disadvantages. Work is ongoing to help overcome specific challenges regarding environmental impact and efficiency. Reciprocating engines have improved significantly over the last two decades in terms of increased efficiency and reduced emissions. Electronic engine control and improved combustion chamber design, including the use of pre-combustion chambers, allow engines to operate on leaner fuel mixtures. Improvements in materials and design have allowed engines to operate at higher speeds and power densities while still maintaining long life.
“The primary challenge today is being environmentally friendly. Reciprocating engine manufacturers are being asked by customers and regulations to burn cleaner fuels such as natural gas and hydrogen.”
Jeff Pappalardo, market development manager for gas turbines and reciprocating engines, Parker Hannifin
Although natural gas burns much cleaner than diesel, it is not a 100% clean option. Oxides of nitrogen (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs – unburned, non-methane hydrocarbons) are the primary environmental concerns with reciprocating engines operating on natural gas.
Noise pollution is another concern with reciprocating engines because they generate more noise than turbines. With newer environmental regulations addressing the problem of noise pollution, there is more focus by manufacturers and engineers to change and enhance designs so as to minimize noise.
Although reciprocating engines have a comparatively high reliability rate, regulations and competitive pressures are driving engine manufacturers to continue performance and efficiency improvements.
Adjusting for changing loads
Weather conditions and times of day influence the amount of renewable power generation being fed to the grids. An ongoing challenge is that most existing thermal plants are designed for continuous high loads. This contrasts with the fact that reciprocating engines today are more often providing stand-by or intermittent power, which results in highly fluctuating load requirements. Although reciprocating engines can start up and reach full load capacity quickly and can withstand dramatic changes in load with many starts and stops, that is not to say such less-than-ideal situations don’t take their toll on equipment performance and service life.
Maintaining performance and efficiency
As is the case with most engines, a reciprocating engine is only as good as its maintenance. Engines need to be regularly inspected and maintained to keep peak performance. This is especially true given the demanding, corrosive environments in which most reciprocating engines operate.
Corrosion can affect an array of components so the use of advanced materials is important for those engines used in corrosive environments. Proper sealing is critical because leaks will shorten part lives and reduce engine efficiency. For example, if leaks occur in the combustion system, fuel flooding can occur thus damaging the piston rings. This will greatly reduce the combustion efficiency of the engine.
There are several preventative actions that should be taken to ensure that internal combustion engines are running at peak performance and not subject to added wear and tear. Ongoing monitoring will improve performance, reduce maintenance costs, and avoid unexpected failures, all of which lead to greater reliability, more efficient operations, and reduced fuel consumption and emissions. Unplanned outages are expensive, giving rise to the increased focus on predictive maintenance programs.
Understanding how you can make the most of new technologies
Reciprocating engine manufacturers continue to develop technologies that enable engines to operate with more fuel flexibility, allowing the engines to run on traditional fossil fuels, natural gas, and hydrogen. That’s good news, but it also means that users need to fully understand the increased component requirements that accompany these advanced technologies.
Download our white paper Reciprocating Engines: A Mature Technology that Is Proving Especially Relevant in Today’s Energy Environment to ensure your power generation plant is realizing the full potential of the latest reciprocating engine technologies and real-time system monitoring.
Article contributed by Jeff Pappalardo, market development manager
Engin Cekic, global account manager, power generation reciprocating engines
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