Direct Electric Power for Vehicles & Equipment

kbd512 · 2022-05-09 13:11:21

tahanson43206,

The prototype John Deere tractor in the link he provided to Alice's website has a very large battery onboard. If we're discussing what John Deere is actually doing, versus what we think they should be doing, then our inability to ever make all passenger vehicles or farming tractors run off of batteries should be part of the discussion.

Edit:
The amount of Copper required to run grid-connected vehicles also runs smack into total global Copper ore mining capacity limitations. This is interesting for Mars, and maybe necessary, but it's not being done on Earth for the reasons already stated. If it was feasible or practical to do it, we would've done it by now.

Last edited by kbd512 (2022-05-09 13:14:17)

Calliban · 2022-05-09 14:37:50

tahanson43206 wrote:

For kbd512 ....
The title of this topic is: Direct Electric Power for Vehicles & Equipment
I ** think ** that Batteries (of any kind) are NOT what Calliban intended for this topic.
Calliban, please clarify your intention for this topic.
I could be mistaken (of course) .... you may have intended to include discussion of battery powered tractors.
(th)

Yes indeed. It was the obvious implausibility of batteries as anything other than a niche solution, that prompted me to suggest grid connected vehicles in the first place. Whereas battery electric vehicles are most likely a fad, electrified railways and tramways have been an undisputed success and are the workhorses of public transportation in many countries. The train that carries me to London and back doesn't run on batteries. It draws power from a conductor rail. Most electric railways draw power from a catenary. Either way, this is a time proven success for transportation. But it clearly has limitations.

Going back to Kbd512s example of a 1-mile long 1000V cable, weighing 5.5 tonnes. We should be able to make these cables from aluminium alloy with PE insulation. To make 13 million of these cables to power most of the worlds farm vehicles, we would need tens of millions of tonnes of aluminium alloy. We would probably need as much aluminium as the entire world produces in 1 year. That is a lot of aluminium. But how much copper and aluminium is already embedded in transmission lines around the world?

Running vehicles on the end of cables is clearly not something that is practical for a machine that needs to travel any distance. But for machines that are essentially stationary, or only move short distances around a fixed point, it is the standard way of providing power. I do not run my machine tools using diesel engines. I use AC power directly from the grid. For mining and farming equipment, which does a lot of mechanical work but never moves very far from its point of origin, cable connected vehicles may be a workable solution. The materials requirements are not trivial for 13 million machines. But compared to battery electric, it looks achievable.

This site gives an indication of the cross sectional area needed for cables carrying power at what looks to be 1000V AC, applying ohms law and an RMS correlation for AC power.
https://www.electrical4u.net/calculator … ize-chart/

To carry 310kW, you need two 300mm2 aluminium cores. The density of aluminium is 2700kg/m3. So a 1-mile long cable would require 2.6 tonnes of aluminium. 13 million such cables would require 34 million tonnes of aluminium. Against Kbd512s chart, that is about six months worth of global aluminium production. If we tried to do the same thing using copper, we would need twice as much - about 74 million tonnes of copper. That is about 3.6 years of global production. Still doable, but the numbers look better if aluminium alloy can be used.

I would posit that whilst battery electric is implausible as anything more than a niche solution, grid electric could be scaled up without imposing unsupportable resource requirements. But it means working at the end of a cable, or having a sliding contact along a cable or rail. Kind of like a dog tied to its kennel by a leash. Acceptable perhaps for agricultural, soil moving and mining equipment. No good for a car and of limited utility for a truck. Grid connected power supply works well for a vehicle travelling a well defined route between two fixed nodal points, like railway stations. That is why it is applied to railways. The route taken by a train never varies in the slightest. So sliding contacts can be used to transfer power. Grid electric power is very efficient when used in this way. Transmission losses from power station to end user are typically about 5%. AC motors are around 95% efficient. So for every 1kWh that goes into the grid, we get 0.9kWh of mechanical power at the wheels. It is hard to beat that sort of efficiency. When combined with the inherently high efficiency of rail based transportation, electrified rail can provide an impressive amount of passenger-miles per kWh of electrical energy. But unless you are living in a city, it is unlikely to take you from your front door to where you want to go.

We could power road vehicles this way on Mars. We have a single segmented overhead DC cable, with sections of the cable alternating between -ve and +ve, with insulation in between the sections. Two sliding trolley contacts would run along the cable. Each contact would alternate between -ve and +ve, as it slid down the power line, with the other contact being the opposite phase at any point in time. By rectifying this rotating voltage, the vehicle can receive constant DC power through a single segmented power cable.

Ultimately, most long distance transportation of people and goods can be transported by electrified railways on both Earth and Mars. It is increasingly clear that the automobile is a fossil fuel optimised system. Automobiles have allowed unprecedented freedom, because the energy density and historic cheapness of fossil fuels, allows anywhere to anywhere transportation. Electric cannot work that way. It can only feasibly provide transportation between specific nodes. I believe that the future architecture of human settlements and industry and agriculture, will need to be reconfigured to work around the limitations of grid electric. This is the only way that electric power can meet humanity's transportation needs. And it will be the only way high speed transportation can be provided affordably without fossil fuels.

Last edited by Calliban (2022-05-09 16:08:46)

Calliban · 2022-05-09 16:25:08

A few statistics that show how advantageous electric rail transportation is.

In 2021, some 580 billion passenger km were travelled in the UK.

https://www.gov.uk/government/statistic … itain-2021

If were somehow possible to meet all of those passenger transportation needs using electrified railways, what would the energy consumption be? The UK electric train in tge below link requires 1.6kWh per 100 passenger-km, if full, travelling at 100mph.

https://withouthotair.com/c20/page_119.shtml

Lets say 0.02kWh/p-km on average, say 80% full. To provide 580 billion p-km, would require 11.6 billion kWh per year, or an average power of 1.32GW. That is the about the same average power output as a single 1600MWe EPR nuclear reactor. If the majority of UK passenger and freight transportation could be provided by rail, nuclear electricity could meet all transport energy needs using just a few large nuclear reactors.

Whilst it would be impractical for rail to meet all of a country's transport requirements, electric rail is probably our best hope of maintaining high speed transportation in a world of shrinking fossil fuel supply. Amazingly, the Japanese seem to have reached this conclusion over fifty years ago. In a future of shrinking surplus energy, electric trains make a lot more sense than battery electric cars.

Last edited by Calliban (2022-05-09 16:48:32)

kbd512 · 2022-05-09 16:54:37

Calliban,

It's not simply implausible, it's all but impossible to use Lithium-ion batteries just to power the farming tractors. The Tesla Model S 100kWh battery contains about 510g/kWh of storage or 51kg of Lithium per battery. In 2021, total global Lithium production was 100,000t.

51kg per 100kWh battery * 468,000,000 100kWh batteries = 23,868,000,000kg or 23,868,000t

23,868,000t of Lithium / 100,000t per year = 238.68 years of Lithium production at 2021 output level

Total global known Lithium reserves are estimated at 14 million metric tons. That's the real reason why we need to process sea water for liquid hydrocarbon fuels. We can't even put a battery in every industrial farming tractor without using Lithium from sea water. Even if we doubled the known Lithium reserves without extracting Lithium from sea water, so what? We covered tractors, but not any other piece of indispensable mobile machinery such as mining vehicles or trains or ships? Nobody has a car, there are no buses, nor any other type of battery powered machine? How practical would that be?

There are an estimated 180 billion metric tons of Lithium contained in sea water, but it's concentration ranges from 0.1 to 0.2 parts per million. At 0.2ppm, you need to process 5 million metric tons of sea water for every metric ton of Lithium. At 0.2ppm, for every metric ton of sea water you process, you get a whopping 0.2 grams of Lithium. Obtaining 1 metric ton of Lithium requires 5,000,000t of sea water. To obtain 1,000,000t of Lithium, that means processing 5,000,000,000,000t (5 trillion tons), or about 5,000 cubic kilometers. There are about 1.37 billion cubic kilometers of salt water to process.

One thing to note about the power cables is that these are 10kV power cables, not 1kV. 10kV at 45 amps.

We don't use Aluminum to make extension cords because Aluminum is not flexible. Aluminum cracks when you bend it back and forth, because it work hardens very quickly. You can work an Aluminum sheet back and forth in your hands a few times and it will break, guaranteed. I don't care what Aluminum alloy we're talking about, nor how dead soft it was when you start. All Aluminum alloy power cables that are rolled up onto a reel will break or degrade unacceptably after a week to a month's worth of work. It certainly won't have the ampacity that it did when you started, either, because the surface of the wire that the current travels along is no longer a smooth piece of metal.

Aluminum alloy overhead wires don't flex all that much in comparison to an actively used extension cord, but they're lighter per foot than Copper, so that is why they're used in high voltage lines. They're wound up on reels and then unwound 1 time, which would be when they're installed. Copper is much more ductile than Aluminum. That's why it's used in extension cords that are constantly flexed. Even Copper work-hardens and breaks over time. That means the extension cords / cables will be stranded Copper conductors, or some kind of Aluminum alloy with mechanical properties that I've never seen or heard of before.

There are over 200,000 miles of high voltage lines in America, and 5.5 million miles of feeder lines that run into our homes.

The 2020 survey recorded 2.02 million farms in America, with 897 million acres / 3.63 million square kilometers devoted to farmland. There were 2.2 million farms in 2007. Slowly but surely, all the smaller farms are being consolidated into larger farms.

kbd512 · 2022-05-09 17:25:00

Look at this web page and see fuel and water requirements per acre:

Purdue University - Estimating Fuel Requirements for Field Operations, by Samuel D. Parsons, Extension Agricultural Engineer, Purdue University

This is for corn and soybean only:

Iowa State University - Energy Consumption for Row Crop Production

Fertilizer Only:

Each year, Iowa farmers plant approximately 24 million of Iowa’s 31 million acres of farmland to corn and soybeans. Energy prices vary over time, but Iowa agriculture spends nearly one billion dollars annually on direct energy purchases. Due to the fact that so many Iowa farmers raise corn and soybeans, a basic understanding of energy used in row-crop corn and soybean production is helpful for managing farm energy expenses.
Annual energy consumption for corn and soybean production is in three major areas: field operations, artificial drying (typically corn only), and fertilizer/pesticides (agricultural chemicals). Agricultural chemicals are not a direct energy purchase by farmers. However, the thermal and chemical processes used in their manufacture can be significant and are often considered in farm energy budgets.
...
Additionally, energy required to manufacture machinery and other larger capital equipment such as grain bins can be significant at the time, but can be paid off over several years. Solar photosynthetic (renewable) energy required to grow and dry crop, also significant, is not considered a direct cost to the farmer.
Field Operations
Diesel fuel used for field operations varies with management practices. A range of 4 to 6 gallons per acre is common, particularly if one primary and one or more secondary tillage operations are used (Figure 1). Seeds must be planted, grain harvested, and weeds controlled (typically with spraying). Fuel used for these operations is typically 2 to 2.5 gallons per acre, which represents fuel consumption for a no-till system. The energy required for tilling soil can be an additional 2 gallons of fuel per acre or more.
The amount of fuel required for tillage depends on both the type and number of tillage operations
(PM 709 Fuel Required for Field Operations). Primary tillage refers to initial tillage on untilled soil. One single primary tillage operation that covers the entire soil surface, such as chisel plowing, usually requires at least one gallon of fuel per acre when tilling at a depth of 6 to 8 inches. Fuel consumption may be two gallons per acre or more depending on tillage depth and/or the number of different soil manipulations that occur (e.g., subsoiling and disking with a combination disk-ripper). Individual secondary tillage operations often require 0.6 to 0.7 gallons of fuel per acre. However, fuel consumption may be greater for large ‘combination’ implements with several operations (e.g. discs, sweeps, harrow, etc.).
...
Fertilizers and pesticides
Energy required to manufacture nitrogen (N) fertilizer is approximately 13 – 18 times greater than phosphate or potassium on a pound-for-pound basis. When anhydrous ammonia, a more energy efficient nitrogen source, is applied to soil, it is equivalent to 15 gallons of diesel per acre at an application rate of 125 pounds/N acre. This application rate is typically used in a corn-after-soybean rotation. Similarly, an anhydrous ammonia application rate of 175 pounds N/acre is equivalent to 21 gallons of diesel per acre. This application rate is typically used for corn-after-corn.
The energy used to manufacture pesticides varies depending on the product. In general, an equivalent of one gallon of diesel energy is used to produce approximately one pound of active ingredient. Using this value, two pints of glyphosate with one pound of active ingredient applied per acre would be equivalent to approximately one gallon of diesel fuel energy per acre.
Due to the fact that adjusting the nitrogen application rate by ten pounds per acre equates to more energy consumption than the amount commonly used for phosphorous, potassium or pesticide, most fertilizer and pesticide energy consumption is attributed to nitrogen fertilization for corn. Nitrogen is not usually applied for soybean production, and only about one to two gallons per acre (diesel fuel equivalent energy) would be used for phosphorous, potassium and pesticides combined.

This is Iowa State's "Store" Website, but the file is free to download:
PM 709 Fuel Required for Field Operations

It looks like we've painted ourselves into a corner with this electrification nonsense.

As a side note, turning corn into Ethanol is moronic.

There's no magic here.

You need diesel.

If you can't get it from the ground, then you need to make it from scratch using solar thermal power.

There is not enough nuclear power, nor will there ever be in a timeframe that actually matters.

Nothing else but diesel fuel will do.

The alternatives are orders of magnitude increases of consumption in other areas where there are not orders of magnitude more materials to throw at the problem.

Calliban · 2022-05-09 17:42:23

Kbd512, the article you referenced talks about various energy inputs in terms of the equivelent energy in gallons of diesel. Ammonia fertiliser production uses natural gas not diesel. Same with many other things. I guess they figure that a gallon of diesel equivelent is a unit of energy that the farm hicks will be able to relate to.

As an aside: calcium is a ductile metal with almost as much conductivity as aluminium.
https://en.m.wikipedia.org/wiki/Electri … nductivity

Calcium cables would need to be well sealed. One crack in the insulation and oxidation will destroy the cable inside of a week. Maybe a better solution on Mars than on Earth.

Last edited by Calliban (2022-05-09 17:43:43)

SpaceNut · 2022-05-09 18:00:27

Power cords that reel out and retract for mars would be cut quite quickly due to the sharp rocks as evident with rover wheels.

That would mean that we can dump the mass of the cable for one that is short possibly no more than 10m long to attach to the power charging stations that can be remote solar battery for recharging during the night as we would add additional batteries to the tractor for mars.

Of course for mars inside a greenhouse that uses natural light could mean beamed energy from the ceiling of the greenhouse to direct power via rf the tractor.

Thank you to all that have had way more time than I to look at this reference for making it practical.

kbd512 · 2022-05-09 19:12:54

Calliban,

Measuring all energy inputs in terms of gallons of diesel provides a consistent unit of measure for determining how practical it is to attempt to use a substitute for what we're already using. If farmers used Joules of energy, would that be more to your liking as an engineer? Hey, Calliban, go pour 53,788MJ of energy into that combine's fuel tank. Just so you know, if you drop in a 13.5 gram pellet of Uranium into the fuel tank, then that combine won't start. Most farmers know what a gallon milk jug looks like, so they know what 400 gallons (53,788MJ of diesel fuel) looks like. All I know is that I really like what our farmers are making and I can't live without it (literally). I want them to make enough food to feed everyone, so I don't get too wrapped around the axle (or soil tiller blade) about how they calculate energy usage so that they understand it.

Calcium has more merit than Aluminum if ductility is required, and it is for any power cable payed out from a reel. Total global Calcium metal production is under 50,000t. Despite its abundance in the Earth's crust, producing enough Calcium metal conductor wire is likely every bit as impractical. Calcium is very ductile, though, so if there's a way to absolutely seal it against oxidation using some kind of polymer insulation, then if we "just" scale up production by several orders of magnitude, maybe it could work. I also agree that using it on Mars would be less of an issue than using it on Earth.

US Department of the Interior - US Bureau of Mines - Electrolytic Production of Calcium Metal

kbd512 · 2022-05-09 20:27:26

SpaceNut,

The "sharp rocks" issue is why I said we need to use Kevlar chafe guards over the power cables, whether here on Earth or on Mars.

This is the only "hope" that I hold for the giant power cable idea:
Copper + Carbon Nanotubes Yield Lower-Resistivity, Higher-Capacity Conductors

If that doesn't pan out, then Copper coated ductile Iron is your only realistic option. Ductile Iron takes even longer to work-harden than pure Copper. It's not as good a conductor as Copper, but maybe it doesn't need to be since most of the current is carried along the surface of the conductor when AC power is transmitted. This is also a real commercial product available at very reasonable prices, unlike Copper-coated CNT.

The downside to Copper-Clad-Steel (CCS) wiring, is that it only has about 40% of the IACS of pure annealed Copper. If you required 1kg of Copper wiring to carry a given amount of current, then you need 2.5kg or CCS wire. At some point, the power cable that the vehicle is dragging along, will weigh more than the vehicle. That 5,594kg 2AWG 10kV wire thus becomes 13,985kg, which means more electric motor power is required to drag that boat anchor through a plowed field. Your only real hope of farming using electricity is Copper-Clad CNT wiring, because anything else is insanely impractical (and also why we're not already doing industrial farming using electricity). So... If wiring technology catches up to where it would need to be, then I'm cautiously optimistic that this will become doable in another 20 to 30 years, assuming we devote the bat guano crazy amount of power required to make enough Copper-Clad CNT wiring. Any magnetic Iron-core wire would also become stiff as a board while dumping that much current through it. I almost forgot about that part. So, yeah, Copper-Clad CNT wiring or bust.

At a global scale, I've adequately illustrated how wildly impractical it will be to replace some but not all of the diesel powered tractors using giant batteries or giant current-technology power cables. That won't stop anyone from attempting such a wildly impractical non-solution based upon religious dogma about liquid hydrocarbon fuels being "bad" or "saving the planet" or "running out" (we will never "run out" if we synthesize more of it from scratch using solar thermal power) or similar nonsense, but ore exhaustion will rapidly put an end to their wildly impractical idea no matter what anyone thinks or believes.

Hybrids make more sense for heavy duty trucks that frequently start and stop, but tractors and combines run near maximum output capability almost the entire time that the engine is turned on, similar to commercial aircraft engines. Whereas commercial aircraft benefit from flying very high where the air is very thin, and engine output is greatly reduced, no such luck with tractors dragging giant steel blades through the ground.

I didn't pick up on your wireless power transmission idea, but that is probably the most practical type of power transmission we would be able to do on Mars since power cables are impractically heavy and resource-intensive, assuming the Iron Oxide dust storms don't interfere with wireless power transmission, which they will. I don't know if there's a way around that, but I don't think so. Copper-Clad CNT wiring it is, then.

kbd512 · 2022-05-09 20:47:23

This process has to be scaled up from a laboratory experiment to a highly repeatable commercial wire making practice that produces results as consistent as wiring made using all the traditional methods:

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

If that can be scaled up appropriately, then electrically powered farming is technically feasible at some level, at least here in America and possibly Europe as well. Elsewhere? Good luck. You'll have to overcome an educational deficit before you can think about using it in 3rd world countries (maintaining the machinery, not using electricity, in case that point isn't clear).

Calliban · 2022-05-10 02:32:53

I think the abrasion problem of sharp rocks on the cable, is likely to be a show stopper for this idea deployed on Mars. Even with a kevlar sheaf, abrasion is going to be a serious problem if the cable comes into contact with the ground repeatedly and scrapes over sharp volcanic rocks.

Then we have the problem of extremely low temperatures on Mars. Temperatures of -90°C will make all materials more brittle and more prone to fatigue than the same materials on Earth. Copper or calcium may be ductile at room temperature. Will they still be ductile at the semi-cryogenic temperatures that we will face the morning after a long Martian night? Would we need to warm the cable up somehow before we can safely flex it?

Whatever equipment we send to Mars needs to be durable enough to survive tens of thousands of hours of continuous service. It is no good if a key component, weighing several tonnes, wears out after a few hundred hours work. A good engineer should always be prepared to give every idea balanced consideration without prejudice. I think we have collectively done that here. But it begins to look sub-optimal compared to other concepts.

I still believe that direct electric provides a lot of advantages both on Earth and Mars. Electric railways in particular make far more efficient use of primary energy than attempting to manufacture a propellant for a road vehicle. But flexible cables appears too fragile and too vulnerable to degradation for use in the Martian environment. This takes us back to our original concepts for digging and mining.

1. CO/O2 produced by electrolysis. Stored either as pressurised gases or cryogens and burned in either a compression ignition or gas turbine engine. The low energy density is less of a problem onma building site, with a refuelling hose never more than a few hundred metres away.

2. A portable high power density nuclear reactor. This could operate on a closed cycle, with waste heat being lost by radiation; or an open cycle, using stored CO2 as propellant. Shielding mass is far less problematic if the vehicle is operated remotely. A problem with putting mobile nuclear reactors in vehicles may be cost.

3. Battery powered vehicles. Our work here has shown that this solution has severe mass penalties. A minimum of two batteries are needed per vehicle. Also, would batteries be deferentially effected by the low temperatures prevalant in the Martian environment?

From our discussion so far, CO/O2 does look like the best option, in terms of cost and technological readiness. I also suspect that the waste heat generated by both chemical and nuclear powered options could be put to good use heating the structures of digging and soil moving equipment. This would allow equipment to be in use 24/7 with less concern about brittle failures during the Martian night. Such options are impossible for battery electric and impractically power hungry for cable-electric.

Last edited by Calliban (2022-05-10 02:53:46)

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