Henry Brean observes that Hoover Dam’s ability to generate electricity is down 20 percent with low lake levels, a reminder of the tight integration of water and power questions along the Colorado River. The history of the big dams on the Colorado River, and the question of who gets their water, is inextricably linked with questions of who gets the power.
Hoover Dam
In a sort of a policy-based perpetual motion machine, a lot of the power generated by the dams’ big hydro plants is used to pump water uphill to farms and cities – down through the dam, then up again through big pumping plants to Phoenix and LA. Only, like most perpetual motion machines, the durn thing didn’t really work when they were building the last link in this chain, the Central Arizona Project. So they built a big coal plant instead which, as Shaun McKinnon recently reported, has turned out to be somewhat problematic.
Anyway, back to Brean, who notes that technology will save us, at least a little bit, with upgrades underway at Hoover Dam aimed at generating more electricity (which we seem to need) with less water (which seems to be what reality dictates in the long run):
The dam’s power customers plan to spend millions of dollars in the coming years to squeeze more electricity from the same amount of water and compensate for a loss of power capacity as a result of the shrinking lake.
The surface of the reservoir dropped 120 feet in the last decade, as the Colorado River came under the grip of the worst drought on record. The resulting loss of water pressure — known as power head — has reduced the dam’s power generating capacity by 20 percent.
The dam and its power customers can’t do anything about the lake level so they are trying to squeeze as much power as possible out of the water pressure they do have.
Though the quote doesn’t say, I assume the upgrades are to more efficient turbines.
Wonder if dam will last longer with less water pressure behind it?
RE: generating power to move water — NGS was built to power the CAP pumps because of a compromise that canceled additional power generating dams in the Grand Canyon. BuRec wanted to build add’l dams to provide power for CAP but enviros did not want dams in the Canyon (for good reason), so they settled on a coal plant instead. Now, because of concerns that the coal plant is polluting the air in the Canyon, they want to shut that down as well (whether for good or bad reason, it’s nonetheless inevitable). So ultimately, AZ is faced with significantly higher pumping costs to sustain their water lifeline. It’s frustrating at times, but things are so highly interconnected – especially in a system like the Colo. R. – the best option is just to accept what will happen and start figuring out how to adapt and plan for the new future.
This is what I love about the media. Henry Brean’s article starts out:
Nov. 14–Hot weather brings a spike in demand for water and power, so Hoover Dam keeps humming all summer long.
Things tend to quiet down from October to April, so that’s when workers try to catch up on equipment upgrades and large-scale maintenance projects.
Lately, a lot of that work has been geared toward improving power plant performance in the face of the lowest water levels Lake Mead has seen since 1965.
The dam’s power customers plan to spend millions of dollars in the coming years to squeeze more electricity from the same amount of water and compensate for a loss of power capacity as a result of the shrinking lake.
Reading this, you get the idea that the reasons for the mechanical upgrades at Hoover are to address the present conditions that exist at Lake Mead. A more realistic reason for the upgrades is that the equipment being replaced is well in excess of 50 years old. The article cites the Francis Turbines. The efficiency gains from replacing an old cast turbine with a stainless steel one is due to the new turbine weighing less – a lot less than the old one. Less force (Flow*Head) can produce the same output due to the smaller weight load. Wicket Gates was also cited in the article. The efficiency factor here is for the units going into ‘Condense Mode’ (another term for this is called: Spinning Reserve). Explaining the details of how Wicket Gates work and the relationship with the generator while it is in Condense Mode would probably fill an entire Post. The bottom line is: Think saving wear-and-tear on the unit as the main motive for this upgrade.
Brean’s last line was the most factual in the article. It states:
Water remains the top priority. After all, the dam was built to control floods and manage water deliveries on the Colorado River, not for its potential as a power source.
“The first goal is deliver the water,” Pellouchoud said. “The second goal is make as much energy as possible with the water you deliver.”
Overall, the spin of the article was focused on upgrades being related to low lake levels. Personally, I think that the prime reason is to replace old equipment at the Dam.
dg