Wärtsilä has been contracted to supply a 56 MW Smart Power Generation power plant to the Stillwater Utilities Authority (SUA) in Oklahoma. The contract was signed in September 2014 and the equipment delivery will begin in November 2015.
Wärtsilä says its 50SG is the largest gas engine in the world.
The power station will balance wind and solar generation in Oklahoma. “When the wind stops blowing and the sun goes down, we need to keep up the load. Quick-starting engines are perfect for this,” SUA’s Director Dan Blankenship said. The plant will also be used for peaking power.
The new plant will replace a 26-MW gas turbine built in the 1950s. The main reason why SUA opted for internal combustion engine (ICE) technology was operational flexibility. “It takes eight hours to start our current capacity. Smart Power Generation can go from start-up to full load in just ten minutes,” says Dan Blankenship. The plant will consist of three Wärtsilä 50SG engines running on natural gas.
The new Wärtsilä 50SG is a four-stroke, spark-ignited gas engine operating on the Otto cycle and incorporating the lean-burn principle. It has been designed using the proven gas technology used in the smaller Wärtsilä 34SG engine. An important feature of this new gas engine in Wärtsilä’s portfolio is its exceptionally high power plant net electrical efficiency rating – more than 53% in combined-cycle mode.
In less than ten years, the installed wind capacity has grown 18-fold in Oklahoma, increasing the need for fast back-up power. Source: US Department of Energy.
Operational flexibility is also appreciated because of the changing market environment in the area. In March 2014, Southwest Power Pool (SPP), the regional transmission organization, took over the dispatch of electric generation for all regional generators in Oklahoma. SPP determines on a daily basis which units will be operated to meet electricity demand most efficiently and reliably. Stillwater’s former inefficient capacity has been called upon only as spinning reserve.
“With new, fast-reacting capacity, we expect to be dispatched more often. We will rank better in the merit order and get more running hours,” Blankenship said.
Gary Groninger, Business Development Manager for Wärtsilä, said: “This plant will provide maximum operational flexibility and the highest simple-cycle operating efficiency in the industry. The plant will provide unmatched benefits to the Stillwater community for the decades to come.”
SG engines are spark ignited, lean-burn, otto-cycle gas engines. In this process, the gas is mixed with air before the inlet valves. During intake, gas is also fed into a small prechamber, where the gas mixture is rich compared to the gas in the cylinder. At the end of the compression phase the gas/air mixture in the prechamber is ignited by a spark plug. The flames from the nozzle of the prechamber ignite the gas/air mixture in the whole cylinder. After the working phase the cylinder is emptied of exhaust and the process starts again.
Oklahoma has more than 1,700 active wind turbines with over 1,300 MW capacity, and ranks sixth among all American states. Wind farms provided 14.8% of Oklahoma’s electricity in 2013 and can power the equivalent of more than 1,000,000 average American homes. The capacity of grid-connected solar panels is still relatively small, but is growing rapidly, 133% in 2013 alone. (Sources: American Wind Energy Association and Interstate Renewable Energy Council.)
Wärtsilä has years of experience supporting wind farms with power plants in the 200 MW range in Texas and Colorado. A new 225 MW wind-integrating power station is under construction in Oregon. Wärtsilä’s total capacity in the United States is some 2,400 MW.
A closer look at the Wärtsilä 50SG
With the launch of the Wärtsilä 18V50SG gas engine, Wärtsilä now has two high-output, highly efficient prime movers when entering the market for large-scale power generation. The new Wärtsilä 18V50SG is the world’s largest gas-powered generating set and is ideally suited for use in locations where a constant supply of gas is assured. On the other hand, when gas supplies cannot be guaranteed under all circumstances, the dual-fuel Wärtsilä 50DF is the right choice. Read more about the Wärtsilä 50SG engine from the article – World’s largest gas engine.
The lean-burn gas engines (SG) feature port admission of gas, prechamber with controlled gas flow as well as individual cylinder control of gas charge and ignition timing. This choice of concept along with extensive research in combustion and combustion control has made it possible to elevate the efficiency from 40% to more than 49% in the bigger engine models. The combination of high efficiency and low emissions is probably unequalled in the market.
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