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It might work better for a lower stage, which would presumably have a lower peak velocity.  At 2km/s, the incoming air will carry some 2MJ/kg of kinetic energy.  That much heating is more manageable via regenerative cooling and is beneath dissociation temperatures, which start to become significant at temperature >2500°C.  Boosting an upper stage to say 2km/s at 30km seperation height would greatly improve payload capacity.

TH, at that speed (>Mach 30) the air would be shock heated into a plasma as it enters the tube.  W.r.t to the tube, the air is moving at 11km/s.  That is a kinetic energy of 60.5MJ/kg, all of which is converted into a combination of pressure and thermal energy, as the air accelerates to the velocity of the tube.  Your tube will probably melt and frontal pressure will blow it apart.  Did Gemini pick that up?

The rotor is now installed!

I still have some work to do to get the machine running.  Weather permitting, it will be up and running by weekend.  This has been the toughest DIY project I have ever taken on.  I renovated a house with less time and effort than it took to build this.  In heinsight, I would do it differently.

This book containsdesign information for a number of different windmills built by settlers in north America in the 19th century.
https://core.ac.uk/download/17270953.pdf

Most of these would have been less efficient than my mill, but easier to build.  Ease of construction is an important factor when choosing a windmill design.  My mill was a pig to build and assemble.

It has been bank holiday weekend here in the UK.  I have spent 3 days working on my windmill.  After months of work the end is now in sight.  Today I have hoisted the rotor.

This picture shows the rotor on the ground prior to hoisting onto the tower.

I decided to add a scaffold tower for extra stability.  At the end of today, the rotor is hoisted onto the table at top of the tower.

Tomorrow after work, I will be adding a platform to the scaffold tower and lifting the rotor bearings into their cradles.  At this point, work on the rotor will be complete.  All that will remain is to attach the rope drive.

GEO is getting increasingly crowded.  Given the need to maintain distance between satellites, we may reach a point where there is no more room for new satellites without removing old ones.  This may ultimately be solved by installing an orbital ring at GEO.  Satellites can be bolted to this ring without need for station keeping or seperation from other satellites.  A ring would greatly increase the capacity of GEO.

One way of avoiding the problem of electrode attack would be to use high pressure argon as the electrode material.  At a sufficiently high voltage gradient, argon becomes electrically conductive.  Metallic electrodes would sit about one inch above the magma surface.  The magma itself is electrically conductive when molten, due to the presence of ionic compounds within it.  So the argon allows electric current to flow from the electrodes into the magma.  Something like this:

The argon acting as the anode would need to be constantly purged with fresh argon as oxygen would build up in the gas.

One complication with this approach is the potential solubility of argon into the magma melt.  Whether this would be an intractible problem, I do not know.

Kbd512, that is a good analysis.  Polysilicon production consumes a lot of coal already.  According to your reference, carbon is needed to reduce the silicon dioxide into metallurgical silicon, and hydrogen is needed to make the silane for purification into semiconductor grade.  These processes are very difficult to divorce from fossil fuel inputs, unless we source the carbon and hydrogen from biomass.  This means that attempting to substitute PV for other energy sources will only serve to shift fossil fuel consumption from electricity production into PV manufacturing.  The alternative (biomass) places another unsustainable burden on the Earth's forests.

In areas with plenty of direct sunlight, trough solar thermal collectors can be used to raise steam at 300°C.  This is beneath superheat temperatures, but it should be possible to generate power with 30% efficiency.  When heat losses from the collectors is factored in, it turns out that a solar thermal powerplant has about the same power density as a PV plant.  So the obvious question is why are we trying to generate power using slabs of semiconductor grade silicon instead of simple, curved alloy steel reflectors?  The embodied energy in a curved steel mirror is at least an order of magnitude lower than a PV panel.  And the technology is really simple.  Mirrors, coolant pipes, boilers and steam generator sets.  This is close to Victorian levels of technological sophistication.  We can add energy storage using stainless steel tanks containing molten nitrate salts.  We could even co-fire solar thermal plants with biomass or coal.  This means that long duration backup power doesn't need a whole other power station.  Just a seperate boiler, but using the same steam generator set.

I can see areas where PV is useful.  In offgrid small power situations, you want an energy source that requires no attention once installed, uses no fuel and has no moving parts.  In those small power situations, cost and embodied energy are less important because the systems involved are generating only small amounts of energy for important functions.  You wouldn't build a solar thermal plant to power a wrist watch, a traffic light or a calculator.  But given the resource requirements, building a PV plant to power a city looks like the wrong technology choice as well.  All technologies have their specific niches where they make sense.  For some reason, the people in charge have lost sight of that.  They are making decisions based upon what is trendy.

Offtherock, the man is talking about the need for carbon as a reducing agent for silicon dioxide.  Carbon means anthracite or charcoal.  There then needs to be a vapour deposition process to convert metallurgical silicon into semiconductor grade.  That means turning the silicon into silane, which is made by reacting silicon with hydrogen.  In the west, hydrogen is produced by steam reforming methane.  In China, they use coal to produce carburetted water gas, because coal is the resource they have in abundance.  Coal also provides the majority of electricity, especially in western China which is where PV manufacture is concentrated.  China absolutely dominates global polysilicon production.  So coal is what is used to make these panels and everything that goes into them.

Regarding your point about the expense of a composite energy system that includes solar.
https://newmars.com/forums/viewtopic.ph … 10#p233410

Your point seems to be that better storage technology and smart grids will be more available and cheaper in the future.  I will talk some more about that tomorrow.

An introduction to EROI.
https://euanmearns.com/eroei-for-beginners/

The reason complex societies cannot survive on low EROI energy sources is that large amounts of energy are needed to operate systems and build / repair / replace infrastructure.  We can divide human energy consumption into three categories.

(1) Essentials.  These are the things that keep society running.  They include energy for transportation, food, water, minimal heating, industry, etc.
(2) Luxuries.  These include travel for leisure, luxury goods, abundant heat, relaxation, etc.
(3) Investment.  This includes energy invested to repair or replace infrastructure.  It also includes energy invested into new equipment and new technology investment.
(4) War.

Society must meet the demands of (1) to survive even in the short term.  Some of what is left over will need to be reinvested to sustain the energy sources that society depends upon (3).  Also included in (3) is the energy that must be invested to sustain infrastructure.  When these deductions are accounted for, anything remaining will be used for a combination of luxuries, technology development, investment in new equipment and war.

If EROI falls too low and investments in new energy supply consumes too high a proportion of harvested energy, all other categories of energy use are squeezed.  It becomes difficult to simultaneous meet essential energy needs whilst also having enough left over for luxuries and investment.  Economic growth will tend to decline, because growth requires energy investment in new infrastructure or technological development.  In the past, civilisations have fallen due to maintenance crisis.  This occurs when surplus energy is insufficient to maintain the infrastructure on which the functioning of society depends.

Some general conclusions can be drawn from this.  Firstly, there is a minimum EROI for which any society is sustainable, given the burdens of essential energy use and maintenance of infrastructure.  Secondly, the wealth of a society and its ability to grow and develop technologically depend upon EROI being greater than a certain threshold value.  The 20th century was marked by very rapid technological advancement, industrialisation, urbanisation, population growth and infrastructure development.  This was made possible through the use of high EROI fossil fuels and the surplus energy they provided.  It allowed huge levels of investment above and beyond those required for basic human survival.

I have almost finished the cone clutch and pulley.  Here is a picture.

Next weekend, I will hoist the nacelle into the cradle, bolt the pulley and clutch to the table and connect the rope drive.  At this point, the machine will be fully operational.

I have great doubts about the sustainability of PV as a bulk energy source.  A lot of people are emotionally attached to it because it seems to them to be an elegant solution - harnessing the power of the sun with no moving parts.    But the materials requirements are huge, as is the embodied energy needed to produce all of the equipment required.  On top of this, it is a technologically difficult product to produce and relies on long supply chains for all of the material inputs and equipment.  PV modules are relatively cheap at present, only because the Chinese are producing them at massive scale, using stranded coal and forced labour.  How long can all of the things that make it possible hold together?  There are just too many things that can go wrong with PV supply chain for it to make any sense pinning our future on it.  It is extremely precarious and resource intensive.  People advocate it more for emotional than practical reasons.  That is about as stupid as it is possible to be when dealing with something as vital to life as energy supply.  We need systems that we can sustain using limited resources that are as close to home as possible.

It has been a busy weekend.  I decided to modify my windmill to make it more versatile.  After installing the tower, I realised that putting the tumbling pot in the nacelle was a bad idea.  It means having to climb 20' up a ladder every few days to change it.  Do that 100 times per year and the risk of falling off the ladder and killing myself becomes significant.

I decided to modify the design so that the rotating nacelle drives a pulley, which transfers power via a rope drive to the tumbling pot.  This is mounted on a table which is attached to the tower at waist height.  The pulley on the table drives a short shaft through a bearing, with the other end of the shaft driving a cone clutch (male).  The tumbling pot is mounted on its own bearings.  The female coupling of the cone clutch drives the tumbling pot on its bearings.  The tumbling pot can be disconnected by pulling the male and female parts of the cone clutch apart.

The modification has added a lot of time to the build process.  But in addition to the improved safety of having the tumbling pot close to the ground, I should be able to use the windmill to drive other tools.  Once it is up and running, practically any rotating tool can be driven by the windmill by fitting it with a female cone clutch and clamping it to the table.  An obvious addition would be a small wood lathe.  A disc saw is another possibility, as is a grinder.  I have a flexible coupling that I can use to drive a drill as well.

My intention is for the stone tumbling to function as a sort of dump load.  When I need mechanical power for some other tool, the tumbling pot will be disconnected and then reconnected when the job is finished.  This allows the windmill to power multiple applications, without any energy being wasted.

The power produced by the windmill depends upon windspeed, air density, swept area and efficiency.  The blade diameter is 2m.  Assuming efficiency of 33% (2/3rd the Betz limit), a 10mph wind would produce 58W of power.  I do not know what the efficiency of the device is.  A low end of 25%, would give a power 42W in a 10mph wind.  A 35% efficiency would give 60W.  Since I don't know what the efficiency is, I can only estimate power to be 40-60W in a 10mph wind.  A mini wood lathe draws about 100W of power, which equates to a 12.6mph wind speed for my machine.  A bench grinder consumes anywhere between 150 - 400W.  Of course tools will still work at lower power.  But work rate will be correspondingly reduced.