Windmills of Nextera Energy’s Peetz Table wind farm twirl in the distance behind the East Cheyenne Gas Storage Facility in Logan County, Colo. Source: Midstream Energy Holdings LLC.
The wind doesn’t always blow nor does the sun always shine, yet renewable energy sources remain in high demand by an environmentally aware public. What can take up the slack, since asking the public to quickly switch off air conditioners and clothes dryers on short notice is impractical?
Power companies are turning to natural gas to make up the difference to keep the lights on, according to a recently published study by Black & Veatch. Entitled “A Bridge to the Future,” the white paper prepared for Houston-based Midstream Energy Holdings LLC analyzes what renewables mean to the gas business in general and gas storage providers—like Midstream Energy—in particular. Black & Veatch found there is an “underappreciated role” for gas “in making renewable power usable.”
Rather than replacing gas as a fuel source, renewables actually stimulate new gas demand, it emphasized. Renewables add to the value of gas storage, which for decades has matched the yin and yang of gas supply and gas demand.
“Emergence of solar, wind and other renewable power sources will modify the role of natural gas but is not expected to replace either gas or its storage assets for many decades to come,” the study said. “In fact, in states with the fastest rates of renewable energy deployment, natural gas networks have proven to be crucial to providing timely access to backup generation when conditions are unfavorable for renewable energy generation.”
Storage is crucial to making a renewable-dependent power grid work because “pipelines alone cannot deliver sufficient gas to meet all daily changes in demand—fast-response help from gas storage has proven to be essential,” it added. “The need for gas-fired generation to backfill for renewable power creates sudden demand for gas and requires rapid responsiveness available only from gas storage facilities.”
Power utilities put extensive work into weather forecasts when planning how much capacity to put online. But suppose a daily forecast starts off accurately: bright sunshine and brisk breezes, but then clouds move in and the wind dies. Another power source needs to take up the slack—and that’s nearly always quick-cycle, gas-fired generation.
Black & Veatch found gas demand can spike by as much as 25% in a few hours, thanks to the interplay of fickle weather and consumer needs. It noted an incident in February 2014 in the Rockies required “quick supply additions that only storage facilities are designed to provide.” Midstream Energy owns and operates the East Cheyenne Gas Storage Facility in northern Colorado that lies near the important Cheyenne Hub of the nation’s gas transmission system, which provides interconnections between Trailblazer, Colorado Interstate, Rockies Express and other gas systems.
Power companies must as a result take into account alternate-source generation capacity in addition to solar panels and windmills. Advanced, gas-fueled generators are ideal since they can be turned up and down comparatively quickly.
“With fast ramping capabilities, natural gas-fired combined cycle units or combustion turbine units provide the majority of 8,000-10,000 megawatts of the flexible capacity that is required by the electric grid. Natural gas storage is needed to follow the hourly load curve because such large load variation will likely exceed line packing capabilities of natural gas pipelines,” it said.
Environmentally focused California seems to be setting the example for such load balancing.
“California has recognized that gas-fired generation must be able to start multiple times a day, ramp down when the sun is shining, and restart quickly to meet evening peaks. Indeed, the California Independent System Operator, which manages California’s electric grid, requires a specific amount of flexible capacity,” the study said.
The white paper noted gas probably will continue to fill this make-up role “unless (or until) a breakthrough in battery technology and proliferation of battery-storage infrastructure can provide additional [renewable] power.” That represents important additional demand over and above the federal-mandated move away from coal-fired power generation.
“The Black & Veatch Energy Market Perspective, projects that a total of 49 gigawatts of coal-fired electric-power generation capacity will be retired across the United States by 2020, and that it will be replaced by a combination of natural gas-fired combined-cycle and combustion turbines as well as renewables,” the study said.
Midstream Energy Holdings’ market area in the Mountain West will certainly be included in that trend—along with the growing renewable market. “At the growth rate expected for renewables in the Rockies, by 2020 a 20% increment for fast-response gas supplies might be needed to fuel quick response back-up generation for renewables, in addition to baseload power,” the report found.
Paul Hart can be reached at firstname.lastname@example.org.