In baseball, a utility infielder is a reliable and versatile player who can fill in at multiple positions depending on the needs of the team. In 21st-century power generation, a reciprocating engine can play such a role.
Indeed, reliable and versatile power plants driven by gas or diesel four-stroke engines are becoming increasingly common. Reciprocating engine plants are used not only for backup, standby, and emergency needs but as the primary power in some applications. And as renewables are poised to become a larger and larger share of the world’s electricity generation, reciprocating engine generators can serve an important role to “fill the gaps,” ensuring continuity of power output when wind and solar installations aren’t producing.
Along with use by power utilities, reciprocating engines have many industrial and institutional applications. They can provide primary or backup power in critical facilities such as factories, universities, hospitals, water treatment plants, and data centers, along with commercial buildings and multi-family dwellings. Aside from their electricity, they produce thermal energy that can be recovered and put to a variety of uses. This is a benefit that increases overall reciprocating engine efficiency.
Read part 1 of our white paper- 2021 Power Generation and Renewable Energy Trends, to learn how fossil-based power generation technologies and power grids are rapidly evolving to meet the demands of the 21st-century market.
Reciprocating engines offer a wide range of advantages for power generation.
Ready to go at a moment’s notice. Reciprocating engines have both fast start-up and shut down, with a minimum uptime of one minute, and minimum downtime of five minutes. They also operate efficiently at partial loads. This makes reciprocating engine plants ideal as a complement to wind and solar installations, to help ensure continuous power generation.
Highly scalable and flexible based on power needs. According to EIA, the capacity of an average reciprocating engine generator is just 4 MW, with the largest around 19 MW. This is compared to 56 MW for natural gas combustion turbines, and 166 MW for combined cycle units. The smaller capacity makes them easily scalable through stacking. As an example: a reciprocating engine plant with six 10 MW engines can provide a range of power levels — from 10 to 60 MW, at 10 MW increments. The plant is therefore well suited to supply more precise levels of additional capacity at times of high demand, or when renewable sources experience an outage.
Fuel-flexibility. They can be engineered to use a variety of fuels. Diesel and liquefied natural gas are common, though many engines are designed to be dual fuel.
Broad operating parameters. They can operate at high altitudes and high ambient temperatures. According to an article in POWER Magazine, reciprocating engines maintain their rated efficiency and power output across a broad range of conditions. Gas turbine power plant efficiency, however, deteriorates by about 1% for every 10-degree increase in temperature.
High reliability. According to the same article in POWER Magazine, outage rates are less than 1% per unit. It’s also extremely unlikely that every unit in a multi-engine plant would be down at the same time. The fact is, engine-based power is a very mature technology, with high reliability.
Thermal output can be tapped for other uses. The efficiency of a reciprocating engine can be enhanced through systems that collect thermal energy from the engine exhaust, cooling water, and lubricating oil. This heat can then be used to produce hot water, low-pressure steam, or chilled water (with an absorption chiller). This can be put to many uses in industrial or institutional applications.
A fact sheet by the U.S. Department of Energy (DOE) includes an illustration of multiple reciprocating engine plants of increasing capacity. Electric efficiencies increase by the size of the plant’s output and range from about 30% efficiency for a smaller plant, to 42% for the largest plant. Capturing an engine’s thermal output can boost overall efficiency significantly, up to approximately 80%.
On the other hand, a simple gas turbine can achieve energy conversion rates from 20% to 35%, according to the DOE. New technologies promise to push this efficiency to around 60%. Adding thermal capture — harvesting heat from the system for other uses — may boost it to upwards of 80%. A natural gas combined cycle turbine can achieve electrical efficiency of around 50 to 60%, according to the International Petroleum Industry Environmental Conservation Association, a global oil and gas industry group.
There are nearly 2,400 reciprocating engine plants in the U.S., according to the DOE Fact Sheet. These represent 54% of installations worldwide. The market is expected to grow globally, with a predicted value of $26 billion by 2026, according to Global Market Insight. This growth will be driven by technical advancement, along with the increasing popularity of liquefied natural gas as a primary fuel in a growing number of units.
The growth is also driven by new applications, including as a complement to renewables. According to the U.S. Energy Information Agency (EIA):
Reciprocating internal combustion engines, which are typically used for backup, standby, or emergency power, are now becoming increasingly popular for larger utility-scale power generation applications, especially in areas with high levels of electricity generation from intermittent sources such as wind and solar. The recent increase in natural gas or dual-fuel capable reciprocating internal combustion engine units has been driven in part by advancements in engine technology that increase operational flexibility and by changes in natural gas markets that have generally provided ample supply and relatively stable fuel prices.
Suparna Ray, principal contributor, U.S. Energy Information Agency
Many operators of reciprocating engine plants have likely discovered that their costs of maintenance are significant. High RPM engines typically require a full annual overhaul, at a significant cost to the operator. According to an article in EPRI Journal, the rule of thumb is that maintenance costs for a reciprocating engine are twice those of a gas turbine.
However, at least some OEMs are addressing this issue through improved engineering and design. Wärtsilä, for example, has developed long-lasting spark plugs and improved the design of its pre-cooling chamber. Both enhancements help increase the interval between plug changes.
Another OEM, Cummins, now offers a program that guarantees maintenance costs. [This helps the operator more fully understand their ongoing investment.
Parker's solutions can help reciprocating engine plant operators manage their costs and optimize maintenance. We offer systems, subsystems, and components that work throughout the plant to reduce emissions, lower maintenance costs, preserve plant and component life and improve turbine efficiency. This includes a wide range of filtration offerings, including plant-level, auxiliary module, air intake, pressurized air, oil, gas, dual fuel, engine crankcase, and more. We also offer fluid condition sensors to monitor fuel dilution, soot ingress, and contamination on engine lubricating oil.
To learn more, read our Power Generation and Renewable Energy Trends White Paper – Part 1.
This article was contributed by the Filtration and Parker Energy Teams.
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