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Cruising to Vegas: Carbon and Climate Change

Last week, I wrote about “The Treasure of the Sierra Nevada” — the treasure being trillions of tons of soluble carbonate minerals salted away in and below the desert playas of the Great Basin. The minerals are the stranded byproducts of several million years of chemical weathering of granite and other rock on the eastern slope of the Sierra Nevada mountains. The weathering products never made it to the sea, because the runoff waters that carried them flowed into the Great Basin and evaporated.

Here’s the deal: if we could somehow arrange for these weathering products to complete their aborted journey to the sea, then natural conversion of soluble carbonates to bicarbonates in the ocean would add enough alkalinity for the ocean to easily soak up all the fossil carbon we’ve dumped into the atmosphere since the dawn of the industrial era.

Of course we couldn’t possibly transport all of that deposited material to the ocean. Among other things, it would require turning half the state of Nevada into a giant open-pit mine thousands of feet deep. And even if we cared nothing about Nevada, we wouldn’t want to transport more than a fraction of the accumulated deposits. There’s so much there that we’d not merely be returning atmospheric CO2 to pre-industrial norms; we’d be lowering it enough to start a new ice age.

However, though excavating and transporting trillions of tons of weathering products is neither feasible nor desirable, a “mere” gigaton or so per year is another matter. It might be feasible, environmentally beneficial, and even (gasp) profitable. How, you ask? Read on!

Most efficient transportation

The most energy-efficient form of transportation is and always has been by water. On the oceans and the Great Lakes, the extreme low energy cost per ton-mile of cargo that giant tankers and cargo ships deliver is well known. But even inland, the most energy-efficient option for transporting bulk cargo is barging on navigable rivers and canals. Before the advent of mechanized railroads in the 19th century, nearly all heavy commerce moved by water. Factories and industry grew along waterways. Even today in the US, the Mississippi River and its navigable tributaries are important arteries for moving bulk cargo.

Of course, inland water transportation is far from speedy. Under way, a modern tow of barges on the Mississippi might make 5 knots. So barging is generally limited to bulk cargos that don’t need to arrive in a hurry. But bulk shipments of carbonate minerals from the Great Basin would certainly qualify on that score — if there were a canal on which to ship them. There isn’t, but might it be possible (and economically feasible) to build one?

Crazy logic

If you asked an experienced civil engineer that question, there’s a 90% chance that the response would be “Are you out of your friggin’ mind?” Possibly more polite, but that would be the gist.

The problem isn’t so much the channel excavation and lining; that wouldn’t be very much harder than building a new 4-lane interstate through rural countryside. The cost of the latter varies widely depending on terrain, but per a 1996 History of Transportation article by William Grossman for Collier’s Encyclopedia, the cost is usually a bit over $1 million per mile. For a project of the sort we’re talking about here, a cost even five times higher than that would not be a show stopper.

For a “Pacific and Great Basin Canal” of conventional design, the larger problems are twofold. One is the number and size of the locks that would be needed. The other is the water flow that would be needed to operate the locks. Or rather the lack of it.

Conventional locks are a Big Deal. Barge canals are generally regarded as practical only in flattish terrain where there is minimal need for locks. There must also be an adequate water flow through the canal to operate such locks as are needed. Routes from the Great Basin to the Pacific don’t qualify on either score.

The playa regions of the Great Basin where carbonate mineral deposits are most accessible are at 4000 feet or more above sea level. The lowest pass into those regions across the hills north of Las Vegas is a little over 5000 feet. So the canal would need to traverse some 6,000 feet of elevation change. By comparison, the elevation change through the Panama canal is only 170 feet: 85 up and 85 down. Two flights of three locks in each direction are employed to accomplish that. The largest rise is 31 feet. The locks are massive structures; their construction was a major feat of the engineering in 1914 when the canal was completed. Yet here I propose a canal with 35 times the elevation change in a desert where there’s essentially no water flow? Ridiculous!

But hold on, please. Yes, it would be ridiculous if I were talking about a canal with dimensions that could accommodate Panamax freighters and massive locks like those built for the Panama Canal. I’m not though. River and canal barges are typically only a fraction of the beam and draft of a Panamax freighter. They’re nonetheless capable of hauling heavy tonnage economically; just not as much in one go. Also, there are alternatives to traditional locks that are much more efficient. They don’t require a flow of water.

Indeed, the aridity of the Great Basin and desert regions through which the canal would pass is one of the better arguments for building it. As a “free” side effect, the canal would bring high volumes of  water to the area. Granted, it would be seawater, not usable for regular crop irrigation. But it would support an extensive system of saltwater lakes and marshes along its route. Much of the water transpired by marsh plants and evaporated from the lakes in the desert environment would return as sorely needed rain and snowfall in the Colorado River watershed. As a collateral benefit, the canal turns out to be a worthwhile fresh water supply project for the parched Colorado River basin.

Lifts, not locks

The first photo below shows a flight of traditional locks built for passing canal boats up and down a substantial hill — Caen hill in Wiltshire, England to be precise. The flight, a section of the Kennet and Avon Canal, employs 29 locks rising 237 feet in 2 miles, according to its Wikipedia writeup. Note the sequence of ponds ascending the hill on the right side of the image. They’re extensions of the pounds, the level sections of water impounded behind lock gates. Normally the pounds are just long level sections of the canal between locks. For the Caen hill ascent, however, the regular pounds between locks are very short, They don’t have enough area to quickly fill the next lock down the flight, or receive a flood of water from the gate above, without an unacceptable change in water level. Hence the pound extensions to the side. The arrangement allows the locks to fill and empty many times faster that the natural flow of water in the canal would allow.

Caen Hill Locks, web  photo from https://canalrivertrust.org/

Despite the clever pound extensions, it still takes about twelve minutes for a boat to cycle through each lock. Most of that is the time it takes for enough water to flow into or out of the lock chamber to raise or lower its level by the roughly 8 foot increment between each successive pound.

A more efficient alternative to this traditional type of lock system is termed a boat lift. A beautiful example is seen in the Falkirk Wheel, pictured below, near Edinburgh Scotland. It raises and lowers canal boats 24 meters in one step to link two separate canal systems.

By Sean Mack – Own work, CC BY 2.5, https://commons.wikimedia.org/w/index.php?curid=2677705

The Falkirk wheel isn’t the most cost-effective design for a boat lift. The heavy cantilevered loads on those elegant rotating arms are very demanding. However minimizing cost wasn’t the top priority for its designers. The lift was intended, in part, as an architectural monument for Britain’s Millennium Link project. The emphasis on elegant appearance notwithstanding, it is remains impressively efficient. The balanced gondolas at opposing sides of the wheel each carry 500 tonnes of water and canal boats. Each 180-degree cycle of load / rotate / and unload takes about 15 minutes — mostly for loading and unloading. According to this Wikipedia article, the old set of 11 locks for which the wheel was a replacement required most of a day for boats to get through. By a supremely British metric, the energy needed to cycle the wheel through one turn is reckoned as equivalent to what it takes to brew 8 kettles of tea.

The reason behind the efficiency and speed of a boat lift is that energy is not being dissipated by pouring water into or flushing it from a lock chamber to raise or lower the boats within. Instead, what amounts to a moveable section of the canal itself is mechanically raised or lowered to allow boats in that section to move between two levels of the canal. The moveable lift sections are usually paired, with the rise of one balanced by the descent of the other.

Thanks to Archimedes principle — that any object that floats in water will displace a volume of water whose weight is exactly equal to the weight of the object itself — the weight of the lift sections does not depend on the size or number of boats floating within it. The weight only depends of the water level within the section. If the water levels are closely regulated, the weights of the ascending and descending sections balance. So while the immediate forces and the mechanical power required for raising one of the lift sections can be very large, both are supplied by balance with the descending section. The paired lift sections operate as a kind of see-saw, with the net power limited to what’s needed to overcome friction.

Contour hopping

The Falkirk wheel serves a canal that cuts directly across the contour lines of a hill. That’s appropriate when a steep rise separates two runs of the canal across relatively level terrain on either side. But it means running a section of the canal as an aqueduct traversing the rise. The extension bringing the upper canal to the Falkirk Wheel is scenic, but was challenging to build. And the larger the canal and higher the rise, the more challenging the aqueduct becomes.

In hilly terrain of the type that the Great Basin canal would traverse in places, the canal route would not cut across contour lines. It would follow one contour for some distance (with strategic cuts and fills to straighten the curves), and then hop to the next. The “hops” would be at boat lifts running directly up the slope between the two contours. A small example of such a lift is pictured below.

By User Calips on fr.wikipedia – Photographie prise par GIRAUD Patrick, CC BY-SA 1.0, https://commons.wikimedia.org/w/index.php?curid=1326439

Power generation

Now we’re coming to the interesting part for clean energy fans. The proposed Great Basin canal would not merely be a system for transporting heavy loads of soluble carbonate minerals from the Great Basin to the Pacific. It would be an important resource for clean power generation!

There are two main aspects of the canal as a clean energy resource. One is direct hydroelectric power generation. The other is pumped hydroelectric storage. We’ll look at power generation capability first. It’s non-obvious and requires some explanation.

The capability derives from the fact that the overwhelmingly dominant flow of cargo in the canal is from clay and mineral deposits at 4000 feet above sea level, transported down to sea level. Every ton of material loaded onto a canal barge at 4000 feet will displace a ton of canal seawater. As the barge moves down the canal toward the Pacific, it shifts a corresponding mass of seawater up the canal.

Assuming we want to leave saltwater lakes and marshes behind where we’ve excavated the carbonate materials, about 40% of the seawater shifted up-canal will be needed to fill the volume vacated when the materials were removed. The rest is potentially available to be sent back down the canal. On its 4000 foot descent, each metric tonne of seawater generates (and/or dissipates) 3.35 kilowatt-hours of energy. We’re shooting for a transport rate of one gigaton of minerals per year. 60% of that would be 600 megatons of seawater, for some 2 billion kilowatt-hours of energy per year. That’s a 24/7 average power of about 230 megawatts.

The actual power available to the the grid would be considerably less. Hydroelectric power generation is only about 89% efficient, and much of the power generated would be needed to move the barges and operate the boat lifts. However the biggest loss is that the flow available for power generation would likely be much less than 60% of the flow of minerals. That’s because a good portion of the seawater shifted up-canal by the down-canal movement of loaded barges would be needed to cover evaporation losses from the canal and from its associated lakes and marshes.

Seawater lost to evaporation is not necessarily lost to power generation, however. Regional geography and  prevailing winds guarantee that a large fraction of any seawater lost by evaporation will show up as increased precipitation over the Wasatch range in Utah or the western Rockies. Precipitation on the western slope of the Wasatch range flows back to the Great Basin, but the rest flows to the Colorado. It will still generate hydroelectric power; it’s just that  the power will flow from the turbines of dams along the Colorado River.

Energy storage and distribution

While the direct hydroelectric power generating potential of the canal is interesting, its significance is mostly symbolic. It’s the fact that the energy cost of canal operation could be negative — that it could be a net energy producer, instead of yet another energy consumer. But the more important energy aspect of the canal is its energy storage potential. Each of the 100 or so level changes that the canal would require joins two large reservoirs at different elevations. Each level change is an opportunity for installation of large scale pumped hydroelectric storage.

When all the stations along the canal are operating in the same mode, each canal section below the upper end of the canal has equal amounts of seawater flowing into it from its neighbor on one end and out to its neighbor on the other end. Water is flowing through all sections, but the water level in each is unchanged. Only the large lakes at the top of the canal will be rising or falling. They effectively serve as the upper reservoir for a single large pumped storage system, whose lower end is at sea level.

The many saltwater lakes and marshes that in aggregate comprise the upper storage reservoir could easily cover 1,000 square miles in total. That’s four times larger than Lake Mead but would still be less than 1% of the state of Nevada. The lower reservoir is the Pacific Ocean. The vast size of the two reservoirs combined with the 4,000 foot elevation difference give the overall system an energy storage potential of 8,800 gigawatt-hours per meter of level change in the upper reservoir.

That storage capacity is so huge that even if the entire Southwest region that it served were to move to 100% intermittent renewables, the system could handle it. There’d be no need for any fossil fueled backing generation. Distribution of the pumping and generating capacity among hundreds of stations along the canal route plus hundreds of square miles of intermediate storage reservoirs would make the capacity extremely robust.

Recreation

Last but not least (as they say) there is one final aspect of the canal project that I should mention. In fact, it’s the source of my title for this article.

A Pacific and Great Basin canal would have huge potential as a recreation resource. It would support boat and barge travel from the Pacific to Las Vegas and beyond to Reno. In this context, “barge” can include not just heavy freight carriers, but also passenger carriers that could be the equal in amenities, if not in size, to ocean cruise ships. Importantly, it could also include privately owned or rented “house barges” for families or small groups.

In Great Britain, the old system of canals had ceased to have much importance for commerce by the middle of the last century. Many of the smaller canals fell into disrepair and were closed, More recently there’s been a movement to restore and maintain them, due to the growing  popularity of “narrow boating”. Narrow boats are live-aboard canal boats, the aquatic equivalent of RVs that are popular here. Their long narrow shape enables them to negotiate the smallest and narrowest of the old canals.

By RHaworth – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=546926

Canal boats of this sort would make appealing successors to highway RVs for leisurely family vacations in a post-carbon world. In the main canal, they’d be towed by tractor robots running on the tow paths for safe “hands off” cruising. But there could be pull-outs and side canals along the way that would lead to docks, stores, picnicking and hiking areas. The biggest of those side canals would undoubtedly lead to a Las Vegas boat park and marina.  It might be adjacent to a “Venice in Vegas” complete with quaint canals, pedestrian bridges, and gondoliers.

The interesting thing about tying in to the Las Vegas and Reno hotel and hospitality industry  is that the entire canal project could conceivably be funded as a way to attract visitors. The two cities have both tried to deemphasize gambling and increase their appeal for family vacations. They face stiff competition for tourist vacation dollars from states with coastal resorts. So imagine the effect if, on top of everything else these cities have to offer, they could advertise ocean sport fishing, scuba diving, and surfing on a 10,000 acre “ocean”  in the middle of the desert.

My initial SWAG for the average cost of the canal proper is $5 million per mile, which is about 5 times higher than the average cost of a mile of rural interstate. For 700 miles of canal (which is about what it would take) that’s $3.5 billion. For 200 boat lifts at 2.5 million each, add $500 million; for 200 pumped hydroelectric stations, 100 MW capacity, $25 million each, another $2.5 billion. That looks like $6.5 billion. For comparison, The Las Vegas Convention and Visitors Authority reports that in 2015, gaming revenues for Clark County (where Vegas is located) were $9.6 billion.

My numbers are little more than semi-informed guessing. They could easily be off by a factor of two or more. But it’s an interesting thought that what would be the greatest carbon mitigation and ecology enhancement project ever attempted could be funded by the money that visitors to Clark county drop on the gaming tables there in a single year.

Content Discussion

Roger Arnold's picture
Roger Arnold on June 13, 2016

To put this in better perspective, following are some specific numbers to chew on. I didn’t include most of these in the article itself, because it was getting rather longish as it was.

* My “stawman” version of the canal is sized for delivering one billion metric tonnes of alkaline clay and carbonate minerals from the Great Basin to the Pacific ocean annually. This would be enough to capture and store about 200 million tonnes of CO2 per year. That represents about 4% of annual CO2 emissions from the US.

* A frequently mooted price for fossil CO2 emissions is $30/tonne; at that price, the clay and minerals transported by the canal would generate $6 billion per year for negative carbon emissions.

* The canal dimensions that I’m assuming for that level of cargo traffic are twin lanes in a divided canal, each 15 meters wide at the water surface and 7 meters deep. With a divider strip 2 meters wide at the surface water level plus two outside tow paths 3 meters wide, the canal corridor would be 38 meters wide. That compares to a minimum width of 23.2 meters for a 4-lane interstate highway.

* The barges would move at 2 meters per second, about equally divided between 1 mps of the barge through the water and 1 mps flow rate of water through the canal.

* Cargo hold in each barge is rectangular 49 m long by 12 m wide by 5 m deep. It would be filled to about 3 m average depth for load of clay and minerals, but same barge could also carry 60 standard 40-foot cargo containers in a 3-layer stack.

* Barges grouped in 3-barge “tows”, 150 m long. Spacing between tows is 650 meters at full cargo traffic level, to accommodate other traffic. All traffic is normally moved by electric tractors on two paths. Tractors are all networked for coordinated movement.

* Lift sections accommodate one 3-barge tow or a raft of smaller vessels no more than 150 m long by 15 m wide; to avoid bottlenecking and backing up canal traffic, lift stations would normally have two 150 m lifts in a 310 m lift section, with each operating on a 12-minute load-move-unload cycle.

* Average virgin hydroelectric power generation for the canal of 100 MW at 5 cents per kilowatt-hour for dispatchable power would equate to $43.8 million / yr, but average pumped hydro throughput of 100 GWh / day (full regional deployment of renewables; 50 GWh purchased surplus, stored, and sold daily) with at two cents / kWh arbitrage would bring $360 million.

* Hardest to estimate are revenues from canal cruises, boat rentals, lodging and other revenue from expanded tourist market. But a 10% increase in visitors attracted would mean roughly 5 million additional visitors and perhaps $10 billion in additional revenue.

Roger Arnold's picture
Roger Arnold on June 13, 2016

(duplicate deleted)

Roger Arnold's picture
Roger Arnold on June 13, 2016

(duplicate deleted)

Jim Baird's picture
Jim Baird on June 13, 2016

Roger how far a field do you have to go to distribute the minerals and the cost of this distribution?

Bob Meinetz's picture
Bob Meinetz on June 13, 2016

Roger, does $5 million/mile include the cost of the land itself?

Roger Arnold's picture
Roger Arnold on June 13, 2016

Good question. It probably needs more research. My current idea is a conservative approach that is pretty much guaranteed to be harmless.

At the ocean port, the canal barges would be emptied, like giant dump truck beds, into a “factory freighter’. The freighter would be equipped with a large porous plate through which seawater — and no fish — would be drawn. A portion of the seawater taken in would be used to leach soluble carbonates from the load of clay and minerals. The pH of the leachate would be similar to what’s found in alkali lakes in the Great Basin: up to around 10, toxic to most sea life.

The rest of the seawater intake would be used to dilute the leachate stream to levels not quickly toxic — perhaps 8.5. Then the mixed stream would be broadcast across a wide swath of the ocean surface in the freighter’s wake. An oscillating fire hose would do it. Mixing with surface waters would immediately dilute the broadcast stream to pH levels entirely safe and barely distinguishable from the background ocean pH. The mildly more alkaline surface would be further spread by taking the freighter on a course crosswise to prevailing winds.

The nice thing about the system is that it doesn’t matter how much the alkaline waters are diluted. The relationship of roughly 9 molecules CO2 absorbed for every carbonate ion introduced will still hold. And “hot spots” for absorption are perfectly OK, because normal winds and turbulence in the atmosphere will keep it well mixed.

Roger Arnold's picture
Roger Arnold on June 13, 2016

(Another duplicate. I need to get a new mouse, or maybe install a new mouse driver. The mouse buttons aren’t being properly de-bounced. One left click on ‘submit’ tends to registers as multiple single clicks. Sorry.)

Roger Arnold's picture
Roger Arnold on June 13, 2016

In the study in which I found the “slightly over $1 million” per mile for a four-lane interstate in rural areas, I believe it did. The cost per mile was many times higher (2 orders of magnitude, in some cases) for suburban and urban areas. Much of that was undoubtedly due to higher costs for acquisition of right-of-way, but a lot was also due to the cost of permitting and associated court challenges, plus the cost of relocating other infrastructure.

For the Great Basin canal, the cost of land would probably be minimal. Much of it would be across BLM land or low-value desert. I arbitrarily chose $5 million per mile as a SWAG, because of the greater volume of earth needing to be moved required as well as the likelihood of more difficult terrain than the “slightly more than $1 million per mile” freeway projects may have traversed. As I said, though, $5 million per mile is a SWAG (stupid wild-assed guess), not a true estimate. It’s meant to give a feel for the scope of the project, not to be taken seriously.

Nathan Wilson's picture
Nathan Wilson on June 13, 2016

Nifty idea Roger; I’m all for grand engineering, and certainly for man-made lakes. A few questions though:

– How do you pay for the system operation? If digging up the clay costs the same as digging up coal ($40/ton), and each unit of clay removes 0.2 units of CO2, then you’d need a CO2 price of $200/ton, just for digging.
– How much of the salt water will leak into the ground and contaminate the ground water? I guess clay makes a good lining for a lake, but the canal must leak too?
– I’m puzzled by the low cost and large pumped-hydro potential. If we predicted the cost assuming it was just a pumped hydro system, I could make a wild guess that a 10 hours system is on the order of $1/Watt, with the turbine-generators being about 40%. So your 8,800 gigawatt-hour system (w/ tiny 1 meter water level range) would be $880 billion if fully powered.
– Without a large net flow, does the water become stagnant and clog with algae?
– How does the cost for the open canal compared to a piped implementation, carrying leachate solution down to the sea, and seawater to the Great Basin? The pipes could have straighter, more versatile routing, but instead of moving 1 gigaton of minerals per year, we’re moving 10 gigaton? of solution downhill, and a similar amount of seawater up. That’s 320 tons/second, for 2 m/sec flow, each pipe is 14.2 meters in diameter.

While the clay is being harvested though, the water flow is very large: 400 megatons per year is 324,000 acre-feet/yr, or 500 square miles at 1 foot depth.

Bob Meinetz's picture
Bob Meinetz on June 14, 2016

Roger, offhand it seems friction losses and inefficiencies might make up a bigger slice of the energy pie than what you’re assigning to them.

Wouldn’t a two-way pipeline (of a dimension on par with the Trans-Alaska one) of seawater going up, alkaline slurry going down be

• More energy-efficient
• Cheaper
• Better able to transgress geography
• Less intrusive?

The potential energy of descending slurry could help pull seawater up via a mechanical turbine system split into stages. But even with the added mass of minerals going down, I can’t imagine there wouldn’t need to be electrical pumps helping out.

A consideration affecting either scenario is the 7-9 magnitude earthquake predicted for sometime in the next decade or two, which will move the Pacific Plate between 3 and 7 meters northward and dump a whole lot of murky seawater somewhere.

Alistair Newbould's picture
Alistair Newbould on June 14, 2016

Just wondering where the $40 a ton of coal came from. I found this (2012) article
https://www.washingtonpost.com/business/economy/cost-of-mining-coal-continues-to-climb/2012/10/24/d15666ca-1931-11e2-bd10-5ff056538b7c_story.html
which quotes around $10.00 a ton. I don’t know if either figure includes rehabilitating the land after extraction. Obviously that would not be required for the proposed clay mine.

Overall a very interesting idea. Another source of income might be shrimp farming – ready market in the hotels. And as the evaporation would gradually increase salinityIto make Dead Sea type concentrations it may be you would need to set aside some salt producing areas. I cannot quite figure if that would actually solve the problem (of increasing salinity).

Now I must go over to “whatsupwiththat” because I’m sure htey are going to love this idea!

Roger Arnold's picture
Roger Arnold on June 14, 2016

Good to see you thought of that. It’s an option I’ve kicked around myself. It would certainly be less intrusive, but it would it would lack most of the important collateral benefits. And I don’t think it works out well for capacity and energy efficiency.

Flow resistance is proportional to the square of the velocity, so specific energy efficiency (relative to capacity) requires a large channel and slow velocity. Also, a pipeline would have no capacity for pumped hydroelectric storage. In the end, I suspect that the enabling effect of the energy storage aspect of the canal for carbon-free energy would be more significant for decarbonization than the carbon capture aspect.

Roger Arnold's picture
Roger Arnold on June 14, 2016

The cost for open-pit coal extraction is overwhelmingly in the cost of removing overburden. I believe I recall a figure of $1 per cubic meter of soil or soft sedimentary overburden. That translates to 40 cents a ton. Some 50 meters of overburden per meter of coal seam defines the rough limit of economic extraction.

Mining the desert playas would be much cheaper. No overburden, and hydraulic methods from floating barges could be used.

Regarding saltwater contamination of groundwater along the canal root, the canal would need to be lined. Preferably with a non-steel reinforced concrete that’s inherently immune to effects of salt water. The lining isn’t just to prevent leakage; a smooth surface is needed to reduce flow resistance in the canal.

Regarding cost of pumped hydro, I was projecting 200 stations, 100 MW each, at $25 million each. That’s $0.25 per watt, which is of the same order of magnitude as your $1.00 per watt. I’m assuming that with 200 identical stations ordered, and no cost for the reservoirs (canals and lakes) specific to the pumped hydro functionality, $0.25 per watt would be feasible. But at this point it’s still guesswork. If a serious feasibility study were funded, one of the first priorities would be to get hard estimates from credible vendors.

Regarding stagnation and algae growth, there’d actually be quite a high flow through the canal sections. 60 – 80 cubic meters per second, in fact. It’s just that it’s mostly a looping flow within the two legs of the canal at each level. It would be feasible to include an artificial salt marsh and large area sand filter within the loop.

Bob Meinetz's picture
Bob Meinetz on June 14, 2016

And good to see you’ve thought of that, I’m comforted I had the same nagging suspicion about flow resistance. Back when I did acoustic design for recording studios, it was the same principle for ductwork: big ducts = slower airflow = less resistance (noise).

Your idea deserves funding to take it from the SWAG to the SEG (Semi-Educated Guesses) stage.

Engineer- Poet's picture
Engineer- Poet on June 14, 2016

specific energy efficiency (relative to capacity) requires a large channel and slow velocity.

Fair enough.

Also, a pipeline would have no capacity for pumped hydroelectric storage.

You could just vary the speeds of the upstream vs. downstream pipelines opposite to each other.  It’s not like your seawater reservoir at the top end wouldn’t provide plenty of buffer.

More issues to consider:

1.  Evaporative losses anywhere above sea level is a deadweight loss of input pumping energy.  You’ll have to move sediment at least fast enough to compensate for that, plus your other flow losses.
2.  Neutral or slightly-buoyant “pigs” carrying sediment inside a pipeline might be a viable alternative to barges.  They could roll along the top of the pipeline on wheels, then just float into the ocean at the bottom end.
3.  Energy recovery by turbines is easy with a pipeline, and you don’t need locks.  Passing pigs around energy-recovery systems needs some cleverness but it’s hardly impossible.

Engineer- Poet's picture
Engineer- Poet on June 14, 2016

What would salt marshes do for your evaporative losses, and makeup water pumping requirements?

Nathan Wilson's picture
Nathan Wilson on June 14, 2016

On second thought, that $40/ton coal price (rounded from EIA) averages various mine types, and includes other costs that Roger mentions below; not relevant.

And I don’t think that salt removal will reduce salinity, at least not the normal solar evaporation type (the evaporated water would need to be returned to the pond). Reverse osmosis would work, but that costs energy.

Roger Arnold's picture
Roger Arnold on June 15, 2016

(still using that stupid malfunctioning mouse)

Roger Arnold's picture
Roger Arnold on June 15, 2016

Salt marshes would of course increase evaporative losses. As you note elsewhere EP, the losses would reduce the flow available down-canal for power generation. If evaporation exceeded the up-canal flow from loaded barges moving down-canal, then it would be necessary to spend power to pump additional water uphill.

Evaporation from salt lakes and marshes is a great way to increase precipitation into watersheds when the lakes and marshes are at low elevation and upwind from mountains. The Salton sink and the area around Death Valley ought to be covered with them. The higher elevations up-canal, not so much. Only the minimum needed to support fish and waterfowl, and make the environment attractive to visitors, if energy is expensive.

If as-available energy is cheap and plentiful, then pumping salt water up to where plenty of undeveloped open space is available can still be a good tradeoff. Though it would be more for the general ecological health of life in the watershed than for cities tapping its rivers. It only takes 600 feet of head to drive RO desalination of seawater. So if the evaporation surfaces would be higher than that, it would be energetically more efficient to just use RO desalination for municipal water supplies.

Of course, energy is a relatively small part of the cost of RO desalination. Pump turbines are really cheap and low maintenance compared to RO plants. Tradeoffs, tradeoffs!

Engineer- Poet's picture
Engineer- Poet on June 15, 2016

FYI, the comment you actually wrote keeps appearing and disappearing for me (mostly disappearing, I’ve only seen it come up on this page once).

Engineer- Poet's picture
Engineer- Poet on June 15, 2016

Doing a take of an alternate scheme, consider rail instead of canals.

The fuel efficiency of freight trains is given as on the order of 450 ton-miles per gallon.  Assuming short tons, 140,000 BTU/gallon of diesel fuel and 45% brake thermal efficiency, that is 101 kJ of net work to move 1 metric ton 1 km.  Given that a metric ton takes 9.8 kJ to raise or lower by 1 meter, a bit over 10 meters of net altitude change per km (1% grade) would be sufficient to power the trains.  4000 feet of Δh would suffice to move things roughly 80 miles, and rail lines do not have to follow contours of the land precisely.

If 80 miles could get you within reach of a navigable river, the rail system would be a lot quicker and cheaper to build than canals.

I started taking a look at the energy requirements of pipelines, but the Darcy-Weisbach equation looks difficult enough without trying to compensate for the higher shear levels of close-fitting “pigs” and I have enough hairy algebra on my plate right now with another thing I’m writing.

Edit:  A lookup of rail rolling resistance brings up numbers closer to 0.001-0.002, so multiply the potential distance numbers above by 5 to 10.

Edit 2:  A double rail line running 20 MPH at 25% occupancy by 120-ton hopper cars could shift over a billion tons per year.

Bob Meinetz's picture
Bob Meinetz on June 16, 2016

EP, a convincing argument you make for rail. Add to it 170 years of moving commodities and transferring them to ships from rail, and we have a body of experience which would likely shave 10 years from development time and $10 billion from cost.

Since we’ve invaded the realm of pragmatism, I hope I’m not damning with faint praise if I assign an order of magnitude more vision and purpose to your idea than it would ever receive from a Trump administration.

Engineer- Poet's picture
Engineer- Poet on June 16, 2016

I can’t claim credit for this idea; I took it straight from the ore-crusher at the Wonder Mine in Death Valley, which was powered by the rock coming down the tramway from the mine up the side of the mountain.

Mark Heslep's picture
Mark Heslep on June 16, 2016

$40/ton is the current market price. Indeed, the actual cost to produce from surface extraction is closer to the figure you cite.

Mark Heslep's picture
Mark Heslep on June 16, 2016

One advantage of pipelines: they have a substantial right-of-way cost advantage over rail (or canal), in that rail subdivides property whereas pipe can be buried or elevated. The Hyperloop proposal enjoys lower theoretical right-of-way costs over high speed rail for this reason.

Helmut Frik's picture
Helmut Frik on March 3, 2017

To get the Dimensions neccesary for a chanenel you don’t just use a rectangular body of water (difficult and expensive to be built) but a much wider stretch of water. Most of the channels would have a wider profile, e.g. like this one here : http://www.br.de/br-fernsehen/sendungen/rundschau/trapezprofil-rechtecksprofil-querschnitt-100.png?version=e8f9e
If you#s start the channel at the Missesipy instead of the Pacific, it would transport sweer water, which would reduce consruction costs dramatically, because there would not be the necessity any more to build everything absolutely watertight to avoid to get the salt in ground water which can have devasting effects over large areas. It would allow a pumped storage in many small steps, but without expensive penstock, and a additional benefit for transportation. So a dual use project. If transport can be really slow it can happen along with storage / generation cycles of the pumped storage scheme, with practically unmotorized, unmanned ships. If thats economical reasonable in the end is another question.