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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.

Spaniard, I searched the internet and found a copy of Hall and Pietro's EROI analysis free to download here.
https://libgen.li/edition.php?id=136738520

Maybe you can find holes in their analysis?

Positions don't change for two reasons.  Either one of the positions is wrong, or the people holding them don't listen.  Usually, both are true at once.

Spaniard wrote: 'And about "renewables need fossil fuels". That's wrong. The right statement is, renewables needs storage. Fuel has advantages and disadvantages, as well as batteries.'

Intermittent renewables have short term and long term variability.  Batteries are expensive and have high embodied energy, meaning a lot of energy is needed to make them.  What this means in practical terms, is that batteries can be used for smoothing short term variability.  A battery big enough to power your house for weeks, would be as big as your house.  And it would cost as much as your house.  And most of the batteries would only be used a few times per year.  What would that do to the marginal cost of storage?  Would the system ever return the energy needed to build it?

This is why in real grids, batteries are used for frequency control.  They are there to meet demand for as long as it takes to bring backup fossil power online.  That is usually gas turbines burning LNG.  LNG isn't cheap by historical standards.  But it is a bulk commodity that can sit in an underground tank.  The marginal cost of storage is very small.  Do you understand what is being said here?

Spaniard wrote: 'Renewable reduce the fossil fuel usage today per $ more than nuclear. Invest on renewable today helps more on reduce our fossil fuel dependency than nuclear.'

That is unlikely.  A renewable system feeding a grid needs a fossil fuel power station as backup.  It will be very difficult and expensive to build enough storage to obviate the need for backup.  And remember that 'storage' is really just another powerplant that sucks in electricity at one end and spits out less electricity as output.  Backup means building two power plants and paying for the capital and operating costs of both.  You also have to invest in additional transmission infrastructure and frequency control, because intermittent renewables have no inertia.  Levelised cost of energy does not account for these things.  At the end of that process, you achieve a modest reduction in fossil fuel consumption.  But the added cost is huge.  And all of that extra infrastructure has a lot of embodied energy, most of which comes from coal, natural gas and diesel.

The cost of new nuclear power depends primarily on build times.  These have stretched from just a few years back in the 70s, to about two decades today.  Part of this is due to regulatory burden and part is due to the loss of all scale economies and supporting industries over the past forty years.  The French built nuclear powerplants cheaply, because they were able to build quickly and in large volume.  They established a national industry that met all parts of the nuclear supply chain.  No one has this now.  But it was a policy choice to shut that down.  It isn't an inherent problem.  And we could, with political will, rebuild it.

Spaniard wrote: 'Insist in making linear projections of copper. But as offtherock commented (and I did in the past), copper usage per unit power is not fixed.'

Yes it is.  The cross sectional area of a copper conductor is directly proportional to the power transmitted.  That is basic physics.  So the more power produced, the more copper needed.  It is possible to use other conductors in particular situations.  Aluminium alloys have always been used in high voltage transmission lines.  We could use aluminium in more applications.  But there will be penalties in terms of power density, corrosion protection and fatigue.  Iron can be used to transmit DC power (though not AC).  Here again, there are penalties in terms of power density, weight and the need for corrosion protection.  As Void noted, carbon nanotube conductors may become practical at some point.  But all alternatives come with cost or performance burdens at present technology sets.  We would already be using them otherwise.

The other alternative for intermittent renewables, is to accept the fact that power will fluctuate and plan your activities around that.  If that is possible, then the energy could indeed be quite cheap, because backup and storage are no longer needed.  But how much of society could work that way?  Could grids function with continuous rolling blackouts?  I don't know.  I would guess that an intermittent energy supply would burden society with a lot of other costs.  But it is the only way I can see this working.

The old fashioned windmills did not try to store wind energy to cover periods when wind was not blowing.  They just varied work rate to match supply.  And they harnessed mechanical energy from the wind to drive mechanical processes with only basic, short range mechanical power transmission.  Those were cheap and simple systems.  But the people involved had to work with intermittent power.  Can we adjust our society to do the same?  Again, I think this is the only way this can work.

Another option that has received surprisingly little attention, is that we escape our pointless addiction to electricity.  I have said this many times before, I know.  We don't anywhere near as much electricity as we use.

Both wind and solar thermal power systems can be used to provide direct mechanical power for many applications.  That power doesn't have to be transmitted using electricity.  Hydraulics, compressed air and mechanical power transmission would all work.  Before the invention of the electric motor, line shafts were used to transfer power from a central waterwheel or steam engine, to multiple machines on a machine shop floor.  There are still factories in the US that use this solution today.  Hydraulics could do this even more efficiently.  Wind turbines or solar thermal plants equipped with hydraulic pumps, can generate and transmit power without need for copper, cobalt or rare earths.  Just steel, concrete and synthetic rubber.

Stationary mechanical power sources can also transport goods.  This can be done by pumping water down a pipeline, carrying floating capsules.  An old fashioned windmill could do that.  In fact, the inland freight transport of entire nations could be done in this way.  No need for electricity.  Just mechanical wind pumps raising water through a head of a few metres.

The sun can also provide direct heat.  This is useful for a huge range of things, from cooking, to iron reduction to brick making.  Crude iron powder can be produced by heating a retort containing iron oxide to 800°C and passing hydrogen or methane through it.  The reduced iron powder can then be seperated from silicate slag by crushing, followed by magnetic seperation.  It can then be converted into steel using an electric arc furnace.  A town could have a centralised oven that cooks food using solar heat.  A laundrette could wash all of the clothing for a town using a mixture of mechanical wind energy to run machines and solar hot water.

To summarise, we don't need high tech solutions to build a society that works with far less consumption of fossil fuels.  It is our slavish addiction to electricity that stands in the way of doing these things.  Also, the fact that we don't seem to be able to conceive solutions that might require a different way of life.  For example, using the town laundrette instead of a home washing machine.  Using a public bathing faciluty instead of a home bathroom.  Eating out at a town restaurant fitted with a large solar cooker with hot rock thermal storage.  Changing energy sources means changing our way of life.   There is surprisingly little thinking about this.

Solar thermal power has some very significant advantages.  It doesn't really offer better power density than PV.  But the materials needed to build it out are steel and concrete.  It is thermal concentrators, boilers and steam generating sets.  Things that we have been building since the end of the Victorian age.  The materials involved are abundant and recyclable.  Energy storage can be added to it with a tank of molten salt.  And we don't need to depend on a Chinese economic system that will soon be gone.

I have installed the cradle for the wind turbine.

The next step is to hoist the nacelle and blades into the cradle.  That is going to take some creative thinking.  The nacelle is as finished as I can get it.

A good place to start if you wish to understand the resource intensity of different energy sources, in the US DOE Quadrennial technology review.  Specifically, chapter 10.
https://www.energy.gov/quadrennial-tech … eview-2015

The DOE have already done the work in estimating the amount of materials of different types needed per TWh of electricity generated.  Solar power especially, is a horrendous resource hog.  Wind power is better, but the material needs are still an order of magnitude greater than nuclear or natural gas.  It was this realisation that awakened my interest in direct mechanical power from the wind.

The economics of intermittent renewables are a strong function of where they are being built.  Location matters for RE in a way that it doesn't for other energy sources.  If the world economy ran on wind and solar energy, there would be huge geographic disparities in wealth, given that the resource is very geographically dependant.  In an RE world, your wealth would depend very much on the location of your birth.

But there is a simple reason why RE will never provide cheaper grid based electricity than nuclear power or fossil fuels.  The reason is that wind and solar cannot replace fossil powerplants.  Those power plants have to be there in standby, waiting for windspeed to drop or the sun to be obscured by cloud or night.  The only thing the RE plant can do is reduce the fuel consumption of the fossil plant.  The fossil plant still has to be built, it has operating cost and maintenance cost.  This is in addition to whatever the RE capacity costs.  All of these costs end up on your power bill.  RE and fossil economics cannot be looked at seperately because they are both needed to ensure a reliable power supply.

Turns out that the Russia collusion scandal was a hoax invented by Obama on behalf of Clinton.  Most people suspected this at the time, there is now solid evidence.
https://youtu.be/tJbsz3sbVz4

Presumably, Obama will face criminal charges now.  I doubt that Trump will see him executed.  But one thing is for sure.  Both Obama and Clinton are finished as political players now.  There is clear evidence that they misled the public with false information.