by Bob Shively, Enerdynamics President and Instructor

Renewable power and natural gas generation have somewhat of a love-hate relationship.  On one hand, they are symbiotic: Variable renewable resources need flexible generation resources to pick up load when the wind doesn’t blow or the sun doesn’t shine.  And other than limited hydro resources, gas generation is best suited to provide the flexible generation needed.  But the renewable industry realizes that cheap gas generation makes it harder for renewables to compete on price.

Gas producers and generators have their own worries about renewable portfolio standards: It appears, in the short term at least, that gas units may be used less frequently to accommodate mandated renewable generation without the gas generators being paid for the flexibility they provide to the system.

An excellent summary of the two ways of seeing the relationship is provided by Navigant’s Richard Smead in the paper Incorporating Gas Fired Generation and Renewables – Looking at the Whole Picture.

One way to bridge the gap is for gas power plant manufacturers to design specifically for use on a system with high penetrations of renewables. One example recently announced is the GE FlexEfficiency 50 Combined Cycle Power Plant.

GE FlexEfficiency 50 Combined Cycle Power Plant

This unit is designed towork efficiently both as a baseload power plant (one that runs most hours of the day) and as a unit that is required to ramp up and down in response to renewable variability.

In the past, units that were designed for baseload use operated inefficiently when frequently ramped up and down, and units designed to be ramped up and down effectively were too expensive to run at baseload.  The new design has a ramp rate of 51 MW-minute compared to a typical 17 MW-minute ramp on a traditional baseload combined-cycle unit.  Yet the unit has an expected efficiency of 60% compared to a typical 40% for traditional gas units used for frequent ramping.  The result is a unit that integrates well with variable renewables.

Unfortunately for those in the U.S., GE will first introduce the new units in Europe and China. Why? Because these countries have stronger long-term policies that support renewables.  If we want to see it available here, it is up to policy makers, regulators and market participants. They must make necessary market changes so that power plant developers are assured of a revenue stream reflective of the benefits they bring to the market. Then they can finance projects that utilize technologies such as the FlexEfficiency 50. When that occurs, we may truly see natural gas and renewables join in a symbiotic, happy relationship.