A Free-Market Energy Blog

Curtailed Hydro from Wanapum Dam Crack: An ‘Unpredicted Change in the Wind’?

By -- March 17, 2014

“Projections show that wind generation will increase rapidly to approximately 6,250 MW by 2013.  This vast amount of wind power interconnected to the Bonneville Power Administration’s transmission grid will likely overwhelm the existing federal hydropower system’s ability to provide sufficient integration services in the future….

As the percentage of wind generation grows, the risk of having a major system event from an unpredicted change of the wind energy level increases.”

– Technical Analysis of Pumped Storage Integration with Wind Power in the Pacific Northwest – Final Report, U.S. Army Corps of Engineers (August 2009).

The magnitude and location of the current unfolding story of a large crack in the hydro-rich Wanapum Dam on the Columbia River in Central Washington became known only a week after the Grant County Public Utility District declared a potential emergency.  Officials reported there is no immediate threat of a catastrophic breach in the dam but called the situation a “serious problem.”  The cause of the crack probably will not be known for some time.  The dam is still producing hydropower, but curtailed production from a water drawdown behind the dam could be felt by California electricity users.

But what did the infrastructure consultants MWH (quoted above) mean when it stated in a technical report for the U.S. Corps of Engineers in 2009 about the problematic integration of hydropower and wind energy: “the risk of having a major system event for an unpredicted change of the wind energy level increases”?

According to the Wind Energy Resource Atlas of the U.S.: “Spring and summer are the seasons of maximum wind power” for the Columbia River Corridor.  Spring is also when snowmelt fills the reservoirs behind dams. The mile-long Wanapum Dam, built in 1959, has 10 reinforced concrete spillway gates each of which are 65-feet wide, 126 feet tall and 92-feet deep. The net head or fall of water on the dam is 80 feet.  If the one cracked spillway failed the water flowing that opening in the dam would be no more than normal for this time of year.  But the water behind the dam has had to be drawn down resulting in less hydroelectric generation.  Wanapum also has 10 hydroelectric turbines on the opposite side of the dam that was not cracked.

However, early reports of the dam crack were vague and were believed to have involved the hydropower turbines. (Wanapum Dam photo here.) The part of the dam that has failed is called an ogee, which is a big concrete bump on the upstream higher elevation portion of the dam over which water has to flow.  The ogee has a 2-inch wide crack across its full underwater face.

The greater concern is that the entire ogee (depiction here) has slipped causing the utility vehicle access road atop the dam to bulge (see: “Outside Experts Weigh in on Columbia River’s Damaged Wanapum Dam,” Northwest News Network, March 5, 2014). The major regional risk is that Wanapum Dam’s hydropower facilities are so large that the Grant County PUD would have to start to buy power to meet any contractual obligations.  California’s Pacific Gas and Electric (PG&E) buys power from the Grant County PUD Wanapum Dam.

Running Hydro with Wind Cracks Dam Foundations

A 2013 Swedish study (“Cracking in the Concrete Foundation of Hydropower Generators”) identified “stops and starts” of hydropower plants as a cause of foundation cracks:

Experience from earlier reports in this field has indicated that cracks may occur at the points where loads from the unit are transferred into the concrete structure. These cracks may be caused by incorrect design of the foundations, incorrect estimation of design loads, mechanical connections in the supporting structure failing to perform the function for which they were designed, or incorrect maintenance of components leading to increased load levels.

If the unit’s operating modes are changed, this also impacts upon the loads occurring in the unit and affects the surrounding structure (i.e. more starts and stops, more power regulations, operation outside the best efficiency range with changes in load levels).

The report concluded:

During inspection, cracks were discovered in the concrete foundation, near the stator and rotor spider supports, at some hydropower stations in Sweden. The cracks were believed to be related to new patterns for generator operation, thereby changing the dynamic loading of the stator and rotor spider supports. Previously the generators ran continuously, while nowadays there are an increased number of stops and starts, sometimes even several times during one day.

Increased dynamic forces due to runaways, and also other dynamic events such as emergency stops, may also contribute to increased stress levels and cracking of the foundation. Furthermore, although extreme loads such as short circuits of the generator seldom occurs, the influence on the dynamic forces acting on the supporting structure and concrete foundation may be strongly influenced during such events.

Sweden both generates and imports a substantial amount of its electricity from wind farms (see “Windpower in Sweden,” Wikipedia).  Unpredictable wind power is thus a source of the “stops and starts” of Swedish hydropower plants serving as backup electricity when the wind stops blowing.  A Nov. 30, 2010 article in the New York Times (“Integrating Wind and Water Power, an Increasingly Tough Balancing Act”) reported that the hydropower providers were coming to the end of the ability to use hydroelectric for system balancing and peaker power because of too much penetration of wind power in the electric grid.

Steve Weiss, an environmental advocate, is quoted: “Hydro sounds like it’s a great fit for wind, but in turns out to be a pretty terrible fit.”

Ideally, hydropower is the best fit with stop-and-go wind power because of its very quick start up time.  But in the real world of structural and power engineering it doesn’t work out that way. If both the river is high and there are high winds, grid operators have to manage a situation of excess power. An ongoing conflict between wind farm operators and the Bonneville Power Administration (BPA’s) has been raging for some time over BPA’s policy of dumping wind power, euphemistically called “curtailment.”

BPA grid operators have not found a way to bring unpredictable and sporadic wind power into the grid especially when rivers are full and hydropower is at peak generation. (see online: “Water On, Wind Off? Generator Curtailment in the Pacific Northwest,” American Bar Association “Trends” newsletter on the environment, energy and resources, November-December, 2013).

The failure of integrating wind and hydropower has resulted in a so-called Smart Grid demonstration project by BPA (see: “The Growing Case for Building a Smart Grid to Supplement Alternative Energy Development,” Examiner.com, Aug. 10, 2010, online).  Part of this pilot project entails the electric grid operator taking over the on and off controls of home water heaters with smart meters in order to store excess power as heat.

Wind and Water Power Don’t Mix

Another problem is that ramping hydroelectric power turbines fast and slow to back up erratic wind power puts a strain on the hydropower plants by wearing out equipment faster and resulting in foundation cracks as reported by the above-cited Swedish study. Hydropower and wind power have ended up not to be compatible. About half of the wind power generated in the Pacific Northwest is purchased by California. After the first report of the crack in Wanapum Dam, Grant County PUD officials clarified on March 4 that the crack involved a spillway on the western face of the dam and not one of the spillways running through a turbine in the powerhouse.

Since 2004, Grant County PUD has been replacing the 10 hydroelectric turbines located in the powerhouse of the dam, which will be completed in 2018.  Wanapum Dam was built in 1959. By comparison the four huge hydroelectric turbines on Parker Dam along the southerly reach of the Colorado River have never been replaced since 1934, although they have been rehabilitated and the controls have been digitized.  The Parker Dam hydro turbines are used to generate constant power to pump water to Southern California and are not operated as peaker plants to back up erratic wind power plants.

Grant County PUD says the reasons for replacement of its turbines is that they are at the end of their useful life and new turbines are necessary to reduce harm to salmon. However, the major technical reason cited by Grant County PUD for replacement of the turbines is “The generator experienced severe stator winding failures due to frequent thermal cycling and operation at high loads” ((see “Wanapum Generator Turbine & Generator Upgrades, July 22, 2008, Board-Meetings08-GCPUD Presentation (07.22.08). (1). pdf).

The 2013 Swedish study cited earlier stated the reasons for foundation cracks at some hydropower stations “were believed to be related to the function of the stator supports and to new patterns of generator operation… [due to] many stops and starts [of the generator].” (A stator is the stationary portion of an electric generator or motor.)

A week after the Wanapum Dam crack was identified and announced to the media, it is apparent that the foundation crack in a spillway gate is not physically related to any turbine vibration or resonation. That is because the spillways and the turbine powerhouse are separate facilities on the dam. This doesn’t negate the Swedish study cited earlier that the physical integrity of hydroelectric facilities are being compromised by the reckless integration of wind and hydropower.

Need Answers on Wanapum Dam, San Onofre Nuke Plant Failures

The Wanapum Dam foundation spillway crack and the cracking of steam tubes in the San Onofre Nuclear Generating Station in Southern California are not directly related. However, nuclear scientist James Conca inferred that the cracks of steam tubes at San Onofre were related to operating at high levels of generation.  Conca states that San Onofre did not need to be shut down if it was merely operated at 20% less output:  “All we had to do was decrease one reactor’s output by 20 percent to solve the problem, which would have dropped total output of San Onofre by 8 percent” (see: “Scientist Says No Reason to Shut Down San Onofre Nuke Plant,” Calwatchdog.com, Jan. 3, 2014, online).

Testimony before Congress asserted San Onofre was being run as a backup peaker plant to handle the vagaries of green power (see: “LTR-13-0346 – Vinod Arora Email re: San Onofre Nuclear Generating Station,” online). 

The cost to Southern California electric ratepayers of attempting to integrate green power into the grid: $4.1 billion (see: “Decommissioning San Onofre Nuclear Generating Station,” SongsCommunity.com). The public has a right to answers to some questions.  To what degree has the apparently reckless policy of integrating wind energy into power grids caused the need to replace hydroelectric power plant turbines and shut down nuclear facilities resulting in huge decommissioning costs on ratepayers, and avoidable risks on bondholders?  What ramifications might this have on the bond market if bond raters foresee more failure of conventional energy facilities?

The public deserves greater transparency and accountability about whether the replacement of hydropower turbines at Wanapum and the cracked steam tubes at San Onofre are the result of the reckless policy to integrate green power into the western regional electric grid.  The cost to decommission the San Onofre Nuclear Power Plant is estimated to be $4.1 billion.  The cost to replace ten hydroelectric power turbines at Wanapum Dam is $300 million. To answer the question of the lead headline of this article: Is the Wanapum Dam crack due to an “unpredicted change in the wind?”

The apparent direct answer is no. But there is another indirect answer blowing in the wind. The crack in a spillway of the dam has brought attention to the fact that the mandated integration of wind power into hydroelectric and nuclear powered electric grids is plausibly resulting in the costly replacement of hydropower turbines that show up in higher hydroelectricity rates and huge decommissioning costs for nuclear power plants. In 1962 pop musician Bob Dylan released his song “Blowin’ in the Wind,” with its memorable refrain: “the answer, my friend, is blowin’ in the wind.”  

In other words, even though the reason the wind blows is intangible, the answer is so obvious it is right in your face.  And the reason that hydropower dams in Sweden are cracking, and hydroelectric turbines are possibly having to be prematurely replaced in the U.S., and nuclear power plants retrofitted as peaker plants to back up erratic wind power have experienced mechanical failures, is indeed “blowin’ in the wind.”

Comments are closed.