“To this day, Tyr Energy, the owner, and Xcel Energy continue to see additional value when analyzing the Plains End plant,” Phil Rutkowski, business development manager for energy solutions for Wärtsilä North America, told POWER. “It is still one of the most flexible and efficient plants available for Xcel, and with its extremely high availability, Plains End has recently picked up the role as being the black-start facility for Xcel’s Denver metro service territory.”

Wärtsilä’s engines also are used at many other facilities, such as the Goodman Energy Center in Hays, Kansas, which was recognized as a POWER magazine Top Plant in 2009. The plant, built in 2008, originally utilized nine 20V34SG gas-fired engines, each with selective catalytic reduction technology to meet local air emissions limits, and with a generation capacity of 76 MW. The facility added three engines in 2015, and the expansion entered commercial service on April 1, 2016, with an increased generation capacity of 102 MW.

At the time of the expansion, Bill Dowling, Midwest Energy’s vice president for engineering and energy supply, said, “The continued development of the regional energy market in the Southwest Power Pool places a premium on owning gas-fired generation that is both flexible and reliable.”

The wide applications for reciprocating engines are noted in the projects where Wärtsilä’s engines are used, including the Barrick Goldstrike Mines in Nevada; the Gyorho CHP plant, which powers the city of Gyor in Hungary; the CHP plant at the Linate Airport in Italy; and the 175-MW Sasolburg power plant in South Africa.

On Land and Sea

“There are a lot of suppliers for reciprocating engine technology,” said ICF’s Paxson. “They’re being used on big utility-scale projects, coming from a number of manufacturers such as MAN Diesel & Turbo, Caterpillar, and Waukesha. They work with a variety of control systems… you can kind of pick from a cafeteria menu, depending on who the integrator is. Today, a small to mid-size power plant equipped with high-output reciprocating engines can effectively compete against a gas-turbine plant of the same size.”

MAN is among the leaders in engines for marine use. ESL Shipping, a leading carrier of dry-bulk cargoes in the Baltic region, recently ordered six MAN L23/30DF generator sets for cargo carriers being built in China.

4. Four-stroke diesel engine. MAN Diesel & Turbo in late 2017 unveiled its 20V45/60 engine for land-based power generation, capable of producing 26 MW, according to the company. Courtesy: MAN Diesel & Turbo

MAN also supplies engines for power plants. Seven of its 51/60DF gas-fueled gensets will power the new 127-MW Maria Gleta plant near Cotonou, Benin, in West Africa. The plant is scheduled to come online in 2019. Late in 2017, MAN unveiled its 20V45/60 (Figure 4), a four-stroke diesel engine that the company says is “the most powerful four-stroke engine in the market,” capable of producing 26 MW. It also offers a marine diesel engine, the MAN 45/60CR, with 12V and 14V versions rated at 15,600 kW and 18,200 kW, respectively.

U.S. Department of Energy (DOE) reports released over the past several months highlight the increased use of reciprocating engines, particularly in commercial and industrial environments, for power generation and combined heat and power applications. The DOE notes how “industrial and commercial companies have discovered cogeneration utilizing natural gas-fired reciprocating engines, not only for high thermal output but also low maintenance costs, low emissions, and high reliability for onsite generation and standby power.”

A DOE-sponsored report written by the Gas Research Institute said the use of gas-fired reciprocating engines in cogeneration resulted in “lower operating costs for the user and potential reductions in emissions of criteria pollutants and CO 2.” The report also noted the increased use of reciprocating engines for standby power, in part due to rapid start-up capability and strong load-following characteristics.

The engines’ “black-start” capability has a role in keeping electric grids humming. Black start is required when a power plant goes offline due to a malfunction or other incident, and the facility needs an external power source to resume operation. Operators can then start their on-site reciprocating engines for the electricity needed to restart the plant. They are often used at nuclear power plants to safely shut down and maintain reactors if there is a loss of power, coolant issue, or other operational anomaly.

“Reciprocating engines are used in almost all commercial and industrial markets globally,” said Aggreko’s Nelson. “Primarily used for backup, standby, or emergency power, generators can be crucial in situations where primary power sources are not reliable, are constrained, or non-existent. In the last few years, an increase in natural disasters has driven the need for large generators [1 MW and above] to provide power for local grid stabilization or for large manufacturers and producers to continue operations.

“During the shale boom in the United States in the early 2010s, remote well sites in the Permian Basin, Eagle Ford, and Bakken required generators to power large pumps,” Nelson said. “Utility power was non-existent and an integrated power solution was needed where 40 to 50 well sites existed in a single location. Petrochemical, refining, and manufacturing plants require off-grid, temporary power during turnarounds and shutdowns.”

Simplicity Breeds Popularity

The simplicity of reciprocating engines also is part of their popularity. “Reciprocating engines are basically the same technology you see in your car,” said ICF’s Paxson. “It’s a fairly simple piece of equipment compared to an aero-derivative [combustion turbine], and the munis and co-ops see [it] as much easier to absorb and digest. It’s a little less scary. The complexity of commercial turbines makes them nervous.”

The flexibility of reciprocating engines is cited as a major part of their appeal. Aggreko touts its Next Generation Gas generators as “versatile and flexible on any gas fuel type,” including associated petroleum gas, compressed natural gas, liquefied natural and petroleum gas, as well as stranded or flared gas. The company says its “mobile and modular plant design also delivers plant flexibility and full scalability, with the ability to increase or decrease capacity according to demand,” and says its generation sets are “ideal for harsh or remote locations.”

Though the market for reciprocating engines is partly tied to the increased use of renewable energy, another technology—battery storage—could limit the engines’ market share.

“The future of power generation will definitely be impacted by the implementation of renewables, and what happens in the storage arena,” said Paxson. “The cost of storage is going to drop precipitously over the next three to five years, much like we saw with [solar] panel and inverter pricing. Once storage technology gets close to parity, and it’s clean, it’s going to be a real mover and shaker in the marketplace, just as we’ve seen coal replaced with gas.”

GSEC’s Hayden agreed. “The more renewables we integrate into the grid, the more need for quick-start and quick-ramping resources,” he said. “The biggest threat to [reciprocating engines] is batteries as the prices continue to fall.”

More renewables and more storage, along with low prices for natural gas, have changed the face of power generation—and that shift will continue.

“We’re going to continue to see coal falling off the map. All the technology will be clean. One would expect in our lifetime that fossil could be replaced entirely with storage. In the mid-term, reciprocating technology is a good solution for institutions and munis,” Paxson said, noting that when it comes to technology advancements for power generation, “it’s going to be a brave new world.” ■

—Darrell Proctor is a POWER associate editor.