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In September 2008, EnergyPulse published an article by Harry Valentine on "The Potential for Seasonal Energy Storage" 1. One of the possibilities for very large-scale pumped hydroelectric storage that Harry mentioned would operate between the Salton Sea in Southern California and Mexico's Sea of Cortez. I didn't initially think his suggestion was practical. Lately, though, I've reconsidered.
The Salton sea presently covers an area of 974 km2, at an elevation of 70 meters below sea level. An inflow of sea water sufficient to raise the lake level by one meter could generate some 200 gigawatt-hours of electricity. That's a gigawatt of continuous output for 8.3 days for each meter of lake surface rise -- enough to supply the seasonal difference in daily average for over 10 gigawatts of peak solar power.
An obvious issue is the distance from the Salton Sea to the Sea of Cortez (or the Gulf of California, as most of us know it). The image below, from Google Earth, shows the two. The Salton Sea is the dark body of water toward the lower left center; the view looks south toward Baja California and the Sea of Cortez. The distance is 185 km. That means the average elevation drop is a meager 38 cm. per km. After Harry's article, I commented that "It would need a diameter of at least 100 feet (for a pipe or tunnel) to move enough water over that distance to generate 10 gigawatts". That was the minimum scale I felt would be needed to justify such a megaproject. But even at that scale, the capital cost of such an enormous water tunnel would make the stored energy prohibitively expensive.
After mulling it over, I decided to do some serious figuring to see if there was any way the project could possibly be feasible. The conclusion I reached, surprisingly, is that in fact it could be -- if it's done right.
What does "done right" mean, and where was I wrong when I previously scoffed at the idea? It wasn't in my "guestimate" of a 100 foot diameter for a water tunnel. That was actually a little optimistic. To carry sea water for 185 km. with sufficient flow and head to generate 10 gigawatts at the end, a tunnel would need to be more like 50 meters in diameter! Even if it were technically feasible to build such a gigantic water tunnel -- which I rather doubt -- the cost would be orders of magnitude too high to pay off. So how do I conclude that the project could be feasible?
There are a number of considerations, but they start from the fact that the project does not require a tunnel! Instead, it would employ a large sea-level canal for 98% of the distance between the two bodies of water. The desert region above sea level that the canal would traverse consists almost entirely of young alluvial deposits from the Colorado River delta. The course is flat and barely 30 meters in elevation at its highest. Cutting a sea-level canal through that terrain would be a large but not otherwise challenging civil engineering project.
Using an open canal rather than a buried tunnel changes the mode of operation for the pumped energy storage system in ways that make it more efficient. I'll explain about that shortly. But more importantly, it enables the system to serve additional functions that enhance its economic and social value. In fact, energy storage might ultimately be among the least of its functions. The system would also serve for:
large scale tidal power generation for northern Mexico;
a major shipping canal for both international and regional traffic;
infrastructure for economic development in the Mexicali region and the Imperial Valley; and
ecological enhancement of Salton Sea and lower Colorado River environs.
Large-scale tidal power generation is enabled by the unusually large tidal swings at the northern end of the Gulf of California. The typical tidal variation at the Colorado River delta is around 7 meters, with two cycles daily.
Using the canal for shipping might raise a few eyebrows. One can question whether there is really a need for a canal to bring freight to inland ports in Mexicali and the Imperial Valley. But it has its points. It would bypass congestion and cut air pollution at the present port of Long Beach, while saving rail shippers the expensive climb out of the LA basin over Cajon and Beaumont passes. It would reduce the travel distance for ships coming through the Panama Canal to the U.S., and would lower the cost of shipping container cargo to and from the Mexicali region and the American Southwest.
As part of an energy project, the canal's use for shipping seems an afterthought. However, to adequately serve its "primary" energy functions, the canal must be BIG. So big, in fact, that it would be a waste not to use it for shipping. My rough figuring calls for 100 meters wide by 35 meters deep at its Gulf entrance. That is ample to allow two Panamax cargo ships, drawn by railed canal mules, to pass in opposite directions. And in economic terms, shipping would be far more than an "afterthought". The canal's shipping role could ultimately eclipse its energy functions. That's not so much from port revenues or the avoided costs of operations out of Long Beach, but rather indirectly. It would attract business and industry to the regions around the canal. Which brings us to the next point: infrastructure for economic development.
The broad desert areas surroundings of the canal route are prime locations for solar power. The energy storage capacity of the canal would provide the means to convert abundant but intermittent solar energy into reliable 24/7 grid power. Available land, clean reliable power, and easy access to worldwide shipping would make the canal a magnet for industrial development. That would bring jobs and residential development. But what about fresh water -- which is notably scarce in that region?
New supplies of fresh water for the region would have to come from desalination of sea water. Geothermal resources at the southern end of the Salton Sea could be useful for that purpose, but probably a portion of generated solar and tidal power would need to be tapped as well. Modern sea water desalination plants consume about 3.2 watt-hours per liter of fresh water output. (The theoretical minimum is .77 Whr / liter. 2) To meet the domestic water needs of a regional population of one million, some 200 million liters per day would be needed -- assuming no special efforts to reduce consumption below the 200-300 liters per day of the "typical" American lifestyle. If met entirely from desalination, that would be a steady 27 megawatts for desalination -- less that 1% of the average output from the solar installations that the canal could support.
We're now beginning to touch on the most controversial aspect of the project: its environmental impact. Before I can talk more about that, however, I need to backtrack and explain the physical characteristics of the canal. The features that allow it to serve for both energy storage and tidal power generation have a lot to do with its impact.
The main part of the proposed canal -- and 75% of the heavy engineering -- lies in Mexico. It consists of a large sea level canal that begins 20 km out in the Gulf of California, runs between sea walls to the shore, and then continues north-northwest for 130 km. to the U.S. border. From where it crosses the border, just east of the town of Mexicali, the canal route follows the sea level elevation contour almost due north for another 60 km. It meets the Union Pacific Railroad trunk line just east of the town of Niland, where it widens into an excavated harbor and seaport. The western shore of the sea level harbor will be only a few km. from the Salton Sea. Pipelines of manageable size complete the connection to the Salton pumping and generating station.
In addition to the canal itself, dozens of saltwater lakes and tidal marshes will be built along its course. Salt tolerant grasses and other plants will grow in the marshes, providing habitat for birds and fish. Although they have obvious environmental benefits, the lakes and marshes are functional components of the power generation and storage systems. They provide surface area to enable short-term storage of large volumes of sea water with minimal changes in water level.
The constructed lakes and marshes need not be deep; total surface area is what matters. Those near the south end of the canal provide storage for water delivered at high tide. Water is released from there at low tide for power generation. The rise and fall of water in these marshes mirrors the twice daily rise and fall of the Gulf of California tide, but at a reduced scale.
The lakes and marshes near the north end of the canal, in contrast, provide storage for water pumped up from the Salton Sea during hours of surplus power. The stored water is returned to generate power at night and other times when generation is down.
We can see now why the open canal works so much better in these applications than a water pipeline or tunnel. A pipeline is inflexible; it connects the two great reservoirs at either end, but to move any water between the reservoirs, it's necessary to move the entire 180 km. plug of water through the pipeline. That involves high losses to flow resistance. In contrast, the canal is is "elastic". It constitutes a long stretched out reservoir in its own right. There are seasonal average flows through it, drawing water from the Salton Sea in summer and replacing it with water from the Gulf in the winter. But the seasonal average flows are one to two orders of magnitude less than the daily flows that generate tidal power and supply load-following capacity to the power grid. With the canal system, those larger daily flows are mainly local -- between the primary reservoirs and nearby sections of the canal and its auxiliary lakes and marshes. Losses to flow resistance are drastically reduced.
Salton Sea Impact
There are several regions impacted by the project. The first is the Salton Sea itself and the area immediately around it.
From the 1930's and into the 1980's, the Salton Sea was a productive fishery and a popular destination for tourism and camping. But with no outlet, the waters have grown steadily saltier and more polluted from wastewater and agricultural runoff. Fish caught there are no longer judged safe to eat and can't be sold commercially. Algae blooms from high fertilizer levels in the water periodically deplete oxygen and suffocate fish. The stink from dead sea life has at times driven away tourists and campers.
Even more ominous for the Sea's future is that California has long been overdrawing its Colorado River allotment. Under court rulings, it is reducing its draw, which means less flow into the Salton Sea. Moreover, a larger portion of the fresh water that is drawn will be pumped to San Diego and other cities, rather than being used for irrigation in the Imperial Valley. With greatly reduced fresh water input, the Salton Sea will continue shrinking and becoming much saltier.
To address these issues, the regional county governments and water agencies got together in 1993 and formed the Salton Sea Authority. The Authority has studied a range of options for addressing the Sea's problems. Several of the early options studied involved canal and pipeline combinations for exchange of water between the Salton Sea and either the Pacific or the Gulf of California. Their focus was limited to stabilizing the water level and managing water quality in the Salton Sea, so they did not include the energy or shipping functions of this proposal.
In May 2007, the Salton Sea Authority issued its "Preferred Alternative and Funding Plan" 3. None of the canal and pipeline options made the cut for consideration in the final selection. That angered not just die-hard canal proponents, but also others who want to see the Salton Sea restored and maintained at its full current size. The "preferred alternative" that was selected reduces the marine sea to less than 10% of its present area. With no canals or pipelines for water exchange, the reduction is necessary in order to slash evaporation losses and accommodate the reduced inflow of irrigation runoff from the Colorado River.
I can't fault the Salton Sea Authority for the plan they selected. In fact, I think it's rather elegant, in the way it manages to preserve the existing shoreline while creating new wetland habitat. The Authority has selected what is probably the most cost-effective alternative for the specific problems it was chartered to address.
On the other hand, there's no question that the canal project described here would also serve to stabilize the Salton Sea and maintain its salinity at an ecologically productive level. The twice daily tidal flows through the canal combined with pumped storage operations would support a high volume of water exchange between the Salton Sea and the Gulf of California. It should be ample to avoid salt build-up, without the need for dikes and impoundments in the Salton Sea. The daily cycling of water through the salt marshes along the canal would provide natural filtration and fertilizer uptake that should eliminate problems with algae blooms. In terms of initial cost, it would be an expensive solution to the Salton Sea's problems. But it would be a solution.
The open water surfaces of the canal and its salt water lakes and marshes would be large enough to affect regional micro-climate. It would increase average humidity downwind of the canal by a small amount and moderate local day-night temperature swings. Since all moisture that evaporates at one location on the earth ultimately falls as rain somewhere else, the project should (theoretically) increase rainfall in northern Mexico, southern Arizona, and west Texas. Whether the effect would be large enough to notice, I don't know.
The real impact would be from the influx of business and population that would follow completion of the canal. The many dozens of storage lakes built around the canal would create some thousand miles of waterfront in what was previously empty desert. The bluffs formed by excavation of a large sea level canal would host prime view lots overlooking the landscaped canal corridor. It's likely that within two decades, the canal would develop into the central artery of an extended "linear city". That prospect will be sufficient to turn some environmentalists solidly against it. Many abhor the idea of building new cities in the desert, when the earth is already in crisis from overpopulation and dwindling resources.
I see it differently. We do face an urgent need to slash consumption and find ways to live more efficiently. However, when efficiency is the goal, building from scratch is often a lot easier than trying to reform a complex existing system. It's not actually all that hard to build super-insulated buildings that require negligible energy expenditure for heating and cooling -- even in the desert. It's also fairly easy to design for very low water usage. Dry climate landscaping, drip irrigation, and low-flush toilets are only the beginning. When fresh water must come from solar-powered desalination plants, there is an economic incentive to use it sparingly. Innovations like blown-mist shower systems, adapted from submarines, start to make sense. The planned communities that will develop along the canal route could be showcases for low-impact, post-carbon lifestyles.
The most problematic area of environmental impact would be to the Gulf of California. The Gulf is a rich area for marine biology. Its nutrient-rich waters are home to a range of unique species, and provide the winter breeding and nursery waters for the California Grey Whale. A sizeable region at its northern end is designated by the Mexican Government and by the U.N.'s Education, Scientific, and Cultural Organization (UNESCO) as a biosphere reserve.
The canal route that I described above would cut straight through the biological reserve. In itself, that wouldn't necessarily be a problem, because sea walls would isolate the canal from the shallow coastal waters and wetlands of the reserve. But construction of the canal and sea walls could be very disruptive. So an alternative route that would bypass the reserve might have to be used. That route would pass west of the Colorado River delta and open into the Gulf near the town of San Felipe, well south of the delta area. That route would be about 35% longer than the most direct route to the head of the Gulf. As it happens, though, there has long been interest in Mexico for building a sea-level canal along a good portion of that route. It would connect to and flood the dry lake bed of Laguna Salada, and create a local seaport for that region of Baja California.
The most controversial impact to the region is probably the large influx of tourists and recreational boating that the canal would enable. At present, the only access to the Gulf of California from the heavily populated California coast is a long slog around the Baja peninsula. That has kept the gulf comparatively unspoiled and free of large-scale development. The canal would most certainly change that. But that might not be a bad thing for local marine life. Isolation has by no means prevented the gulf's waters from being heavily overfished. Some once-popular species have already been fished to apparent extinction. A healthy tourist industry based around diving and sport fishing could be the only realistic way to curtail overfishing and conserve local marine life. At least, that seems to be how it has worked in some other areas.4
Notes and References
1. Valentine, Harry, The Potential for Seasonal Energy Storage, Click Here
4. See, for example Click Here and linked reports on the job creation and economic benefits of marine conservation. The jobs created are mostly in tourism, and provide relief to the poverty that drives overfishing in less developed areas.
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Excellent. This is the sort of thinking that is needed to manage our future. It seems to me that the civil work required would be not out of scale with past projects of similar purpose (Suez canal, Panama canal) and some of much less use (palm islands). The idea clearly has enough merit to warrant financing of at least several levels of detailed enginreering study.
Bob Amorosi 9.10.10
Roger Arnold deserves a medal for being a model innovator. The thinking he did and research of data to put this article together is precisely what engineering invention should be all about. We need a lot more creative people like Roger in America to solve the challenges facing us in the future. If this website had an award for the best thinker/writer articles, this one would win my vote hands down.
Now if only someone in a high office could take the ideas in this article and fund the necessary engineering studies, and if their conclusions looked promising, start the ball rolling to raise the investment money to realize them.
Harry Valentine 9.10.10
Roger, I commend you on your innovative approach to exploring the future potential of the Salton Sea. Researchers and climatologists who have discovered the long-term cyclical weather patterns in the SW USA have also discovered that the watershed of the Colorado River has undergone repeat cycles of rainfall and extended drought. In short, the Hoover dam was built near a peak of precipitation and could run dry for several decades. Your research regarding the Salton Sea offers hope to the the SW USA . . . in fact, it may offer the best hope for the future of the region.
Roger Arnold 9.11.10
Guys, you're making me blush. That's high praise. I'm not sure I really deserve it, but I won't insist that you take it back. Thanks. ;-)
As you're all aware, the idea is only the first step. It's marvelous the research that can be done and what can be discovered with a bit of googling, but it mustn't be mistaken for the kind of serious design study that is needed before commencing this sort of project. However, I do think it's true that we've sunk sufficiently deep into the unholy do-do of climate change, peak-oil, and financial crisis that it will require bold and large-scale initiatives if we're to have any hope of extricating ourselves. Timid half-measures and business-as-usual are not going to cut it.
Hmm, I think I'd better shut up. I'm beginning to sound, even to myself, like a politician. I can't think of any worse fate!
Peter Macalua 9.14.10
Roger Arnold, I salute you and your brilliant ideas. As an electrical engineer with long years of experience, I have never encountered such brilliant weaving of rather separate and conflicting impact ideas and quitely reorganizing them as if by magic everything come into play. Congratulations Sir!
Jerry Toman 9.14.10
While the idea is great, in and of itself, it could further form the basis for a new "Garden of Eden" in which additional energy could be produced from the sea water, warmed even more by the sun and fed to an array of Atmospheric Vortex Engines, which could not only generate power, but, in some seasons, could provide a cooling cloud cover for more conventional agriculture.
It could also be combined with the "seawatergreenhouse" technology or biofuel plants based on algae production. Many, many possibilities are engendered by this.
Good work, Roger--and congratulations on being able to "rethink" your original conclusions by "expanding" the concept into something that could have truly great benefits to the region as well as serve as a model for other "geo-engineering" projects.
Many jobs for Mexicans and Americans can result from this...maybe that "wall idea" between the two countries wasn't such a great one after all! May an "Arnold Friendship Bridge" connect the two countries at the intersection of the border and the new "Arnold International Canal"!
Jerry Toman 9.15.10
One thing that concerns me, Roger, is the scale of earth excavation required to build a sea-level canal through say 50 km of terrain about 20-25 m above sea level at its surface as well as the "need" for it to be 100 m across.
I'm thinking that for something like this to actually "get built" in reasonable time and with reasonable financing costs, it might be better if it were roughly half that size (width if not depth) and built on two levels--one at sea level for about one-third of the distance and second one at approximately 20 m altitude, with "locks" connecting the two sections.. You could have wider sections ~0.5 km long, about every 5 km or so to allow large ships to pass, kind of like a "turn-out" seen on mountainous roads.
Of course, you would have to invest capital and energy to be able to pump the water up to the 20 m level, but you would get that back as the sea water is allowed to fall through turbines into the depression. I would envision this to be best accomplished in several stages, with "marshes" allowed to flourish over the course.
John K. Sutherland 9.15.10
Roger, Well thought out. Perhaps the Mexico drug lords could be persuaded to fund the 130 km in Mexico. They need nice little shipping routes like this with lots of traffic.
I would like to see you do a similar analysis of the Dead Sea project that has been talked about.
Roger Arnold 9.15.10
Jerry, if the main purpose of the canal were to support a moderate volume of shipping and if excavation costs were a major issue, what you suggest could make sense. Even though the time it takes to cycle through them makes locks a pain for shipping.
However, the size I estimated for the canal was based on its use for large-scale tidal power generation and pumped hydroelectric storage. You don't want the flow rate through the canal exceeding about 2 meters per second -- a fast walk. One meter per second or less is better. Otherwise you start running into erosion problems and significant loss of head. To support 10 GW of tidal power from a 7 meter tidal swing, the canal needs to be on the order of 100 meters wide by 35 meters deep, at least around its southern end where it is conveying large flows between the gulf and the storage lakes and marshes.
I estimated the total excavation volume for the sea-level, 100 m width canal as being roughly one billion cubic meters. That's 5600 m2 average cross section times 180 km. That sounds like a lot, and in fact it is about four times the volume of material that was moved for the Panama canal. But technology has changed a lot since 1905. That's only about a year's work for one of the big bucket-wheel machines used to remove overburden in open-cast coal mining.
Roger Arnold 9.15.10
Oops, sorry. Slipped a decimal point. One billion cubic meters is about ten years of work for one of the larger models of bucket wheel excavators made by ThyssenKrupp. Those are rated for removal of 12,500 cubic meters of overburden per hour, according to the Wikipedia article.
Jerry Toman 9.15.10
This is so "preliminary" that a lot of alternative schemes are possible and need to be explored. But I still like your idea of "extending" the SOC by whatever amount could be considered "economic", for many reasons, not the least of which is to provide warm water to feed an array of AVEs in a climate modification scheme for what is otherwise an "unlivable" region, that could serve as a nucleus of development and sustainability for people living on either side of the border.
Connecting just a 50 or 100 km canal, built entirely in Mexico with a new, cross-border rail line at its terminal is another option, leaving the balance of any flow to the SS to be carried by conventional pipeline. Again--I don't consider a "high-flow" case to be necessary due to the possibility of developing other means to generate the electrical energy you anticipate would be needed.
I guess what I would question is the "need" to generate 10 GW of power from tidal action and pumped storage facilities, believing that there might be cheaper methods of generating a high fraction of this amount. Many of the "other" benefits you have described might still be achievable in this manner, requiring significantly less transport of water from the Sea of Cortez to the Salton Sea.
Len Gould 9.16.10
Looks to me like those dredging ships used to build the palm islands might be a more economical way to excavate. Call these guys.
With typical capacities of 10,000 cu meters and doing perhaps 100 loads per day, a fleet of these ships could be done the job in 10^9 / 10^6 = 3 years approx.
Jerry Toman 9.16.10
Suppose it were feasible to build a sea level canal to carry ships say 40-80 km inland?
Would there be any advantage in making it "horseshoe" shaped, with flow only in one direction allowed? Could the width be decreased to less than 50 m in such a case?
Ships lined-up outside for 2-3 hours, could start entering one leg on the "rising" tide, one after another.
Of course, at the "apex", you would need to build a proverbial "wide-spot-in-the-line" with wharves for them to unload their goods onto trains, if not locks to carry them "yet further inland" through a canal built at a higher level (perhaps with a "downslope" toward the Salton Sea).
Roger Arnold 9.19.10
I spend several hours yesterday browsing the archives of the Imperial Valley Press Online and chasing references. I wanted to see what's been happening with the Salton Sea Authority's "preferred alternative and funding plan" in the time since I originally wrote this article.
The plan is stalled, if not entirely dead. The state has not come through with any funding. Nominally that's due to the budget crisis, though I suspect that continuing opposition from various groups made it easier for Sacramento back off. What I find interesting is that one factor in the opposition's success was uncertainty about the actual viability of the "preferred alternative". It's possible that its system of dikes would be vulnerable to earthquakes and unstable land on the Salton Sea bed. The dikes would have been employed to create a horseshoe marine lake surrounding a system of salt marshes and a central salt pan.
The area has long been known to be geologically active. There are geothermal resources near the south end of the Sea, and magnitude 6 quakes have been recorded. That's hardly surprising, given that the whole Imperial Valley is a northward extension of the rift that split Baja California from Mexico and created the Sea of Cortez. It would be seabed today, had the Colorado River not dumped the Grand Canyon into it and created the plug of material that Mexicali sits atop.
Apparently, the land is more unstable even than people thought. There was a recent study published in Nature of core sample from the lake. They appeared to show that in the past, whenever the Colorado river flooded and deposited a new load of water and sediments in the lake, it was followed by sizeable earthquakes. I'm not sure how they determined the coincidence of sediment deposits and earthquakes, but that's what they claimed.
The obvious question is how this would affect the canal project that I proposed. It would certainly be raised as in issue by opponents. The "worst case" scenario would be an earthquake that opens a fault leading from the canal to land below sea level in the Salton Sink. Water would flow from the sea-level canal to the basin below. If the water managed to carve a good sized channel that couldn't quickly be blocked, the entire Salton Sink might eventually be filled. Communities with total population over a million would be flooded -- not to mention thousands of square miles of productive farmland.
It's actually pretty easy to protect against that disaster scenario. I didn't show it, but my strawman canal design included several points where the canal flared out and split along both sides of an artificial island. The islands were actually floating "corks" for the canal, moored in place. If cut loose, they would drift into the neck where the two halves of the canal rejoined. They would jam into that neck, plugging the canal. So the only water that could empty into an opened break in the canal would be the contents of the canal segment containing the break.
Xuguang Leng 9.20.10
70 m of elevation over 185 km is not very useful for electricity generation. Colorado River is 2,330 km long and 3,101 m elevation. On average, Colorado River has 3 times of elevation difference per km than "Salton Sea Canal". Yet, Colorado River is damed only a few places, the rest is not useful.
Even the elevation is useful, it requires a canal that is more than 2 times the length of Panama Canal, and probably wider and deeper as well. I don't see how it is economically feasible. To generate electricity, it is much easier just dam a river.
Roger Arnold 9.21.10
Looks to me like those dredging ships used to build the palm islands might be a more economical way to excavate.
When I was growing up in Colorado 50+ years ago, there was at least one place in the mountains I remember visiting where you could explore the hulk of a long-abandoned placer mining dredge. It amazed me that you could have one of these humongous mining barges operating in a small mountain stream. The way it worked was that they created a mobile pond in the middle of the stream where they were working. They excavated material from one end, ran it through crushers and sluices to extract the gold, and dumped the spoil out the other end.
I imagine the equipment for a canal project like this might work in a similar manner. Instead of dumping the excavated material out the back, it would have long conveyor booms to dump it off to the side.
I don't really know what equipment would work best for this type of project. The project is easily large enough to justify custom equipment -- rather like the giant tunneling machines that custom-built for each major tunneling project. But the sort of "components" that the project engineers have to play with include the 100-ton power shovels and 400-ton dump trucks that are employed in the Canadian oil sand operations. The point I was making in estimating the excavation volume and time was just that, although it's large, it's in line with what's done routinely in open-cast coal mining operations.
I guess what I would question is the "need" to generate 10 GW of power from tidal action and pumped storage facilities, believing that there might be cheaper methods of generating a high fraction of this amount.
You may be right about cheaper generating methods, but at this point, the AVE remains speculative. Tidal power is known technology, and economical in locations with large tidal swings. 10 GW, however, wouldn't be the average output. That would correspond to the peak flow rates when the high water reservoirs were charging or when the low water reservoirs were discharging. The average power output would be about a quarter of that.
70 m of elevation over 185 km is not very useful for electricity generation.
Correct, but you have misunderstood the operation of the project. It's pumped hydroelectric storage in the vicinity of the Salton Sea, and tidal power generation in the vicinity of the Sea of Cortez. The canal allows for exchange of water between the two seas, at an average rate determined by the seasonal differences between generation and storage. The exchange is needed to limit the buildup of salt levels in the Salton Sea.
Xuguang Leng 9.21.10
I am an electrical engineer. But I know water needs elevation difference to flow. 70 m of elevation in 185 km will make water barely flow over the long distance. There probably won't be much elevation left to generate the electricity, assuming you can find a good site that has steep elevation drop to build the power plant.
There is not a lot of capacity in Salton Sea either. 1 sq. km is about 200 acres. 1000 sq. km is about 200,000 acres. 1 m over 1000 sq. km is only 600,000 acre-feet of water. The annual flow of Colorado River through Hoover Dam is in millions of acre-feet. So the Salton Sea isn't anywhere near to be massive, even assume a large canal can be built. Colorado River is evergreen, Salton Sea? You fill it up and it is gone. No more electricity.
Roger Arnold 9.21.10
LOL! Is anybody else having the difficulty that Xuguang is having in understanding what was -- and was not -- proposed?
I thought my description was pretty clear, but Xuguang apparently read it and got a completely different picture stuck in his head. Everything he writes is 100% correct, but what he's writing about has almost nothing to do with the system I described. So did I botch the description, or does Xuguang need to work on his reading comprehension?
If I was making implicit background assumptions about readers understanding of pumped hydroelectric storage that I shouldn't have been, I'd like to know about it. My aim is to educate people about possibilities, not to confuse them.
Xuguang Leng 9.22.10
I think somebody had previous proposed in this forum that pump storage can be built between the two Great Lakes. The Great Lakes are certainly better pair that Salton Sea and Pacific Ocean, but they still won't fly.
Has anybody ever, over the history, built a canal/aquaduct over long distance that reverse flow? And how long doe it take the water to flow 185 km? How many stages of pumping stations you need to have on the way? Note you want to have reverse flow, so the canal has no slope, no gravity flow, pure pumping. What is the pumping/generation efficiency? And the engineering/construction cost is what billion? What again is the benefit?
Roger Arnold 9.22.10
Good! You're starting to ask the right questions. Yes, the average flow through the canal is close to zero. (There's a small net inflow, to cover the excess of evaporation over fresh water inflow to the Salton Sea from other sources. That average inflow, however, is insignificant against the daily flows for power buffering, and even the average seasonal flows for water exchange and seasonal power buffering.)
I wrote this article over a year ago, and I don't have the calculations handy, but as I recall, an average flow rate of one mps through a 100 m wide x 35 m deep canal gave a 2 m drop over the 185 km course of the canal. The flow resistance, however, goes as something like the 2.4th power of the velocity. It's a high Reynolds number flow with a fully turbulent boundary layer, so the empirical formula that I dug out of a hydraulics textbook is not a simple power law. But if the flow rate were to increase to 2 mps, the drop would become something more like 12 m -- which is enough to start being a problem. So the canal must be large, to keep flow velocities small.
What you're still missing is that very little of the daily flow through the pumps and generators travels any great distance. It's predominantly between the Salton Sea and the constructed salt lakes and marshes within a few miles of the sea itself. If you play around with Google Earth, you'll see that the land to the east of the Salton Sea rises fairly quickly. Not "mountain slope" quickly, but fast enough that there is land well above sea level within only a mile or two of the current minus 70 m shoreline. The daily flows required for buffering intermittent energy resources are 90% between the Salton Sea and the salt water lakes and marshes constructed around the canal on that nearby land.
Because the predominant flows are local, the canal could be blocked entirely at its middle, and it would make no short-term difference to the daily operations of either the pumped hydro station at the Salton Sea nor to the tidal power operations at the other end. So why have the canal at all?
It's explained in the article, but perhaps not as clearly as it should have been. I'll let you think about it for now. And if it's any consolation for you, your thoughts about this, and the problem of the long distance between the two seas, mirror my own thinking when I initially rejected Harry's suggestion. It took me some time to see the collateral benefits and overall system advantages that a large canal would enable.
Len Gould 9.23.10
Another benefit which you haven't mentioned, Roger, is the possibility that the system can overcome the "lack of water" objection to large development of solar-thermal generation in the otherwise ideal area around (or even over) the Salton Sea.
Len Gould 9.23.10
1000 sq km @ 1 kw/sq m raw insolation with 50% area coverage, 15% plant efficiency provides a 5 x 10^8 x 0.15 = 75 GW nameplate output. At 33% capacity using the pumped storage Roger describes, provides a continuous baseload capacity of 25 GW.
And the resulting shading of the sea itself would sufficiently reduce evaporation rates so that a lot more of the inflowing fresh water could be diverted to other uses.
Roger Arnold 9.24.10
Hmm, I think you'd get a lot of community pushback at the idea of enclosing a good portion of the Salton Sea under an array of solar panels. It might also be difficult to provide for the periodic washing of dust -- or in this case, salt crystals -- that the panels would accumulate. But as a benchmark for perspective on the issue of scale, it's instructive.
What would almost certainly be feasible, however, is building large solar ponds in some of the shallower portions of the Salton Sea. Solar ponds are efficient collectors for low-grade heat, around 110 degrees C (230 F). Not much use for generating power, but quite handy for desalination. There's a new-ish process for fresh water production via "forward osmosis" and relatively low grade heat. It looks very promising to me. Should be several times more efficient, per area of collector, than PV production of electricity driving conventional reverse osmosis.
There's also an interesting new process for biologically-catalyzed production of carbonate minerals from brine and atmospheric CO2. It could become the basis for a large green industry for production of carbon-negative building materials.
Jerry Toman 9.24.10
The closest natural analogy to the Atmospheric Vortex Engine is the "waterspout" which can form at sea level with water temperatures barely above 30 C.
Thus, water from a large solar pond could be used as feed to the engine and produce electricity efficiently.
Here's a video of a waterspout in the Gulf of Oran.
Several different versions of this and other waterspouts can be found on the internet.
The most prolific waterspout zone in the US is the Florida Keys.
In the Gulf of California, there are several bays that, with a little engineering, could be converted into "waterspout generators" without need of additional solar ponds, though employment of these as "superheaters" could further increase water temperature and thus, power available from the AVE.
Don Giegler 9.25.10
You're certainly right about the area being seismically active. The San Andreas Fault, more specifically. Apparently the Los Angeles Times wrote up a 2009 incident report on the same at:
Was there a sequel for the Easter 2010 event? Know that Mexicali suffered some quake damage from that one, but heard nothing about the canals that currently run into the Salton Sea or about any changes to the sea itself. Saw somewhere that the Colorado River flow over the years has had as much to do with the character of the sea as anything else. Besides OBE and SSE analyses would such a pumped storage undertaking require looks at 100-year or 500-year flood events?
Roger Arnold 9.25.10
You're right about the San Andreas fault. But the quakes that were written about in the Nature article I mentioned were apparently not related to shifting along the fault. They were simply due to the weight of water and sediments washed into the basin by major flooding events on the Colorado. The construction of Hoover dam has presumably put and end to such floods.
What I don't quite understand is how flooding could deposit that much water and sediment without cutting a new channel that would divert the Colorado into the Salton Sink. That has happened with some regularity in the few million years. Once a channel into the Salton Sink has been carved, the river flows that way until a freshwater sea completely fills the basin, and forces the flow south again to the GOC. After that, the freshwater sea begins drying up. Apparently it only takes a on the order of a hundred years to do so -- pretty darn fast, considering that a sea completely filling the Salton sink would hold as much water as the Great Lakes.
Roger Arnold 9.25.10
I'm leaving tomorrow on two weeks vacation. I probably won't be responding to any more comments until after I get back.
If anyone really wants to discuss this with me -- they're welcome to call my cell phone. That's (408) 802-3060. (That's the number that should be listed in my author's profile. The number that's listed there now is obsolete. I can't seem to get the editors here to fix it.)