Mechanical energy transmission

Up: Energy transmission

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Mechanical energy transmission cables

Due to the very high energy densities that are handleable with diamondoid nanosystems (See e.g. page Electromechanical converters)
and the possibility of infinitesimal bearings energy could potentially transmitted mechanically.

Transmission medium (meta)material

Bundles of nanotubes may be a good option due to their high tensile strength.
Maybe such bundles with finite strand length could be made into incrementally repairable metamaterials? Anisotropically elasticic metamaterials might be a good choice to get aground tight corners.
See: Elasticity emulation

Translative and/or rotative

Energy could be transmitted via translative or rotative or combined movement of macroscale diamondoid ropes/rods/tubes.
For continuous pulling flexible belts ropes or chains could maybe be considered.

Limits to transmittable power density by tensile strength

Power is force times speed (corresponding to voltage times current).

• The force is limited by the tensile strength of the used rods.
• The speed is limited by the turn radius and thus indirectly by the tensile strength of the housing structure.

Method of bearing

To maximize power density in mechanical energy transmission both the force and the speed needs to me maximized.
This can lead to significant centrifugal forces at places where mechanical power transmission lines curve.

There are methods for ultra low friction levitaion but these typically can provide much less supporting force.
Thus these methods of bearing motion may more suitable for:

• rotative/torsional power transmission
• low speed chemical and entropic power transmission (beyond the scope of this page)

Infinitesimal bearings seem like the only non-macroscopic bearing technology that can take very high loads.
Thus the feasibility of translative/reciprocative mechanical energy transmission depends on the effectiveness of infinitesimal bearings.

Infinitesimal bearings can be arranged as concentrically cylindrical shells along the whole length of the cable.
Infinitesimal bearing layer-number reduces the relative speeds per layer linearly.

Doubling the thickness of an infinitesimal bearing cuts the total friction by half.
While internal bearing area doubles interface speeds half and dynamc friction quaters.
Overall total speed dependent dynamic friction halves. (See: Superlubrication)

Sharp turns – high speeds

With rising speeds in translational transmission cables centrifugal forces become exceedingly high making beefy supporting structures necessary.
Power densities beyond the already very high limit imposed by by diamondoid systems withstandable centriugal forces are then accessible. See: Unsupported rotating ring speed limit.

Sharp turns – slow speeds

For lower power densities and lower speeds very sharp bends can still be problematic as the transmission medium needs to bend. Anisotropic elasticity metamaterials may be a good option. See: Elasticity emulation One may want to use metamaterials anyway for

• stopping cracks from propagating
• doing easy incremental repair (perhaps even live on hot on running systems?!)

But adding anisotropic elasticity is additional design effort and may lead to a bit of a trade-off.

For torsional/rotational transmission lines specially designed 90° turning elements may be usable.

Rate limitations on startup and power surges

For medium long to very long distances one can meet the limit of specific strength that is the rods can't turn/pull their own inertial weight anymore.
This limits the power-up rate (unit: watts per second). To mitigate that one could put energy storage cells and interfacial drives continuously alongside the power line. This can kick-start powerlines or compensate for too sudden power surges.

Speed of sound as limit for (uncached) energy transmission

The energy transfer speed (propagation of the rising flank after power-up) is equal to the (very high) transversal or longitudinal speed of sound of the chosen diamondoid material but still significantly slower than electrical impulse propagation. The maximum speed of continuous axial movement is not limited by the speed of sound though. For all practical purposes this limit is so high that it wont matter much.

Violating the the speed of sound limit

There are

• AC alternating rotative
• DC continuous rotative
• AC alternating translational (aka reciprocative)
• DC continuous translational

Note that for the last one translational energy transmission cables
the speed of sound of the energy transmission medium (meta)material is not a limit.
Cables carrying speeds exceeding that significantly exceed the speed of sound c_sound in diamond may be possible possible.
Consequences:

• Energy can be transmitted faster than the speed of sound (without caching)
• Limits on areal power-density are set only by against centrifugal force supportable turning radii and tolerable friction losses

Note that when going to the multi km/s speed range even with bending radii the size of planets
there is already notable (albeit not brutal) centrifugal force.

Practically though with the speed of sound already being very high in diamondoid systems
supersonic speeds will likely not be present in widespread infrastructure systems.
Rather only experimental systems and maybe (highly speculative) launch loops.

Safety

For not well designed translational energy transmission cables damage from mechanical impact can becomes a very serious hazard.
Concentrated release of the transitionally in the system stored energy at the damage point could result in a serious detonation.
It should be not too difficult to design systems such that horrendous accidents pretty much are impossible though.

Quantitative numbers

Example: Limit for areal power density:
50GPa ... ~ tensile strength of natural diamond - mechanosynthetisized one will be stronger
c_sound ... the longitudinal speed of sound in diamond

• 1000th c_sound: 50GPa * 18m/s = 900GW/m² = 9GW/dm² = 90MW/cm² = 900kW/mm²
• 100th c_sound: 50GPa * 180m/s = 9TW/m² = 90GW/dm² = 900MW/cm² = 9MW/mm² (seems practical)
• 10th c_sound: 50GPa * 1.8km/s = 90TW/m² = 900GW/dm² = 9GW/cm² = 90MW/mm²

Note that if the cable (for whatever reason) is free standing and goes around in a cricle there is a scale invariand speed limit of about 3km/s above which a nanotube ring ruptures due to centrifugal force. This also poses a limit to areal power density in small scales of at least 15MW/mm². soem form of nanoscale levitation method may be needed to reach such powerdensity levels.

[Todo: Compare to expensive overhead power line ~ 1MW/mm²] [note the involved high kinetic energies]

To minimize acoustic losses in the environment a (high) number of litzes/strands operated in different phases can be combined. Elastic losses translate to capacitive losses in electrical lines. Rotation has higher stiffness but also higher speed dependent power dissipation [to verify]. Translation has lower stiffness and lower speed dependent power dissipation [to verify].

Note: Inertal energy is bound in non-sinusodial steady state operation and surfaces at shutdown.

[Todo: Discuss insertion and extraction of mechanical power]
[Todo: There seems to be a discrepancy to the power densities noted in Nanosystems. Note that they are related to volume not area like here.]

Transporting chemical energy

The idea is to pack some energy storage cells on the energy transport track. Its probably very useful for low speed systems - including almost all the stuff of everyday use. For high sppeed systems at some point the kinetic energy will outgrow the chemical energy since it grows quaddratically instead of linear with speed. Also chemomechanical converters are slower than mechanomechanical transmissions and may loose efficiency when operated to fast.

Mechanical energy transmission cables vs electrical superconductors

• Non mechanical technology path

It's still unclear whether superconductors will some day meet widespread use. It doesn't seem too unlikely though.

• With advanced thermal isolation even today's superconductors may be usable. These YBCO superconductors contain not the most abundant but also not exceedingly rare elements.
• The discovery of a practically usable room temperature superconductors is (as of 2017 to the knowledge of the author) still an unpredictable scientific discovery. Superconducting topological insulators may be a promising field.
• With advanced mechanosynthesis a giant space of strongly metastable non-equilibrium structures becomes accessible that is not accessible via conventional thermodynamic production methods (mixing,melting,annealing,...). The neo polymorphs. This allows for much more powerful random and systematic search.

Measuring the remnant resistance of superconductors has (to the knowledge of the author) never been archived (physics usually does not like true infinities / true zeros). So the energy transmission efficiency should be even higher than the one of mechanical energy transmission cables.

The downsides of superconducting energy transport in comparison are:

• involvement of not so extremely abundant elements
• susceptibility to electromagnetic interference (solar storms / EMPs)
• associated strong magnetic stray fields
• achievable efficiencies for mechanical energy transmission cables should be near 100% anyway.

On a highly speculative note:
Has anyone thought about bearing things by floation them on superfluids?

Alternate uses

Warning! you are moving into more speculative areas.

Beside energy transport continuous linear movement cables could be used for the forces they develop. When curvature and speed produces forces exceeding gravitational acceleration (note that there is no need for escape velocity) the cable could (very speculatively) lift by itself and build a launch loop. When such a cable is cut a big scale explosion may follow depositing lots of material at the explosion site.

A better approach may be J. Storr Halls static Space Pier.
If you want some discussion of the widely known space elevator concept in light of advanced APM capabilities go here.

Related

• superlube tubes
• global scale energy management
• power density
• upgraded street infrastructure
• unsupported rotating ring speed limit
• global microcomponent redistribution system
• Pages with math
• Large scale construction