Flexibility in power plants is acknowledged as a critical instrument for managing fluctuation in electric demands and providing grid support services. The ramp rate – the pace at which a power plant may increase or reduce output – is one indicator of this flexibility. Wärtsilä engines can ramp at over 250 MW/minute, far quicker than gas turbines, delivering ultra-responsive power required for renewable energy integration.

Flexible generating units contribute to grid stability by scaling output up or down when demand and system loads shift. Electric grid managers rely on power plants that can offer additional load (or restrict demand) on the same timeframe as fluctuations in renewable production since solar and wind energy can fluctuate in minutes. The ramp rate is the rate at which output increases or decreases every minute and is commonly stated in megawatts per minute (MW/min).

Most industrial frame gas turbine types offer ramp rates ranging from 10 MW/min to 100 MW/min, with an average of roughly 25 MW/min. Ramp rate is determined by the capacity of the producing unit, the operating conditions (whether the unit is just starting up or running at a minimal load hold point), and optional technologies for reducing startup time and improving ramp rate. A power plant’s ramp rate is also affected by the number of units and their configuration. A ramp rate of 100 MW/min, for example, is based on multi-turbine plant designs, such as a 2×1 combined cycle gas turbine (CCGT) plant with a net power output of 750 MW and each gas turbine rated to ramp at 50 MW/min. While ramp rate in MW/minute is an essential measure, it is also crucial to understand the operational parameters that allow promised ramp rates to be realized.

Ramp rate vs. starting loading capabilities

For gas turbines, the initial loading capability is frequently significantly different from the quoted ramp rate. Only until the unit has attained self-sustaining speed can gas turbine ramp rates of 35 to 50 MW/min be achieved. Under hot start circumstances, the quickest loading gas turbine types supply 30% load after 7 minutes and require approximately 30 minutes to reach maximum power. The Wärtsilä 34SG combustion engines are real rapid starters, with an effective ramp rate of 50% per minute and a full load time of 2 minutes. This translates to 100 MW/min for a 200 MW facility.

Figure 1 compares the initial load delivery of Wärtsilä power plants and gas turbines, displaying the proportion of load provided 7 minutes after initiation. This is based on manufacturer-published ramp rates and assumes optional gas turbine technology for rapid loading. Wärtsilä engines have a substantial operating advantage over gas turbines due to their quick startup time. Both the Wärtsilä 34SG and 50SG engines have now achieved full load, despite the fact that gas turbines are still delivering output.