Inequality among renewables

Most generation professionals in the electric power industry are relatively unfamiliar with how hydroelectric projects really work. The prevailing view that flowing water turns a generator shaft to produce electricity, while true, does not acknowledge the complexities associated with the operation of these facilities.

Consider the Bonneville Power Administration, which markets power from federal dams along the Columbia River system within the constraints and requirements for other river purposes. Flood control, protection of fish listed in the Endangered Species Act, compliance with the Clean Water Act, etc, take precedence over power production.

And now there are “must take” renewables to accommodate. As part of its mission to market federal hydropower, BPA is the primary high-voltage transmission provider in the Columbia River Basin, home to more than 3000 MW of wind-powered generators. Consistent with FERC (Federal Energy Regulatory Commission) policies for open-access, non-discriminatory transmission, BPA integrates new power sources into its grid as requested.

Wind capacity in the area served by BPA is being developed well ahead of regional power demand growth because of the challenging Renewable Portfolio Standards promulgated by the western states. In fact, 80% of the wind power generated along the Columbia River is delivered to utilities located outside BPA’s balancing authority area.

The rapid increase in wind power production in the Northwest (along the Columbia River and elsewhere in the region) has increased the power system’s maximum output by a significant amount. Meanwhile, the balancing reserves needed to accommodate wind have consumed a major portion of the Federal Columbia River Power System’s operating flexibility.

To illustrate: Columbia River gorge wind patterns are extremely variable and storms cause large up and down ramps that are hard to predict with precision. To accommodate the 3000 MW of wind power currently interconnected to the federal system, BPA now sets aside about 850 MW of hydro capability to provide incremental (INC) reserves and about 1050 MW to provide decremental (DEC) reserves.

Translation: BPA runs hydro generation 1050 MW higher than minimum generation at all times so it can reduce hydro production (DEC) if the wind picks up and suddenly increases above its schedule. In addition, hydro generation is run 850 MW below maximum generation at all times so BPA can increase hydro output (INC) if wind dies and wind generation falls below its schedule within an hour.

One impact of rampant growth in renewables generation is illustrated in a recent report, “Columbia River high-water operations,” DOE/BP-4203, September 2010. BPA had been aware for some time that a combination of high stream flows and high wind could pose new challenges for its Columbia River system operations.

Such a “perfect storm” occurred during the first two weeks of June 2010, in an otherwise low-water year. BPA considers this event a likely preview of situations the organization and region will face again, and for longer periods during years of heavy snow.

Simply put, this was the conundrum caused by the freak weather system: Maximum wind and hydro generation together exceeded demand; reservoirs behind dams along the Columbia rapidly filled to maximum capacity; a need to control “spill”—that is, dumping water downstream without generating power—to control the amount of nitrogen in the river water. High amounts of nitrogen can be lethal to fish.

To minimize excess spill, federal hydro facilities produced, at times, more than twice as much power as needed to meet BPA demand. Since generation must equal demand, BPA was forced to sell its power at prices down to $0/MWh to reduce excess spill and manage total dissolved-gas levels. During the first two weeks of June, BPA disposed of more than 50,000 MWh for free, or for less than the cost of associated transmission.

But maximizing hydro generation was not enough to manage the high flows and prevent reservoirs from overfilling; spill flows had to be increased. Such additional spill is termed “lack-of-market spill” since it would not have been necessary had there been additional markets for power.

All thermal facilities in BPA’s balancing authority area were reduced to the minimum loads necessary to keep them connected to the grid during the weather anomaly. For example, the nuclear plant known today as the Columbia Generating Station was operated at less than 20% of its rated output for a few days to avoid a shutdown.

Grid impacts. Finally, because federal hydro generators were producing far in excess of BPA demand, and wind power and other resources also required transmission, the grid was stressed. Transmission availability significantly limited opportunities for increasing hydro generation to reduce dissolved-gas levels in the river.