New Mars Forums

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.

A ducted wind power concept.  I like it.  The cross sectional area of the duct is lower than the swept area of a conventional horizontal axis wind turbine of the same tower height.  So power density is lower.  But the tower and duct are static structures and won't wear out quickly.  The moving parts are relatively compact and close to ground, making it easy to swap them out as modular components.  So this design benefits from greater longevity and is easier to repair.  If I wanted building integrated wind power, this sort of ducted design is where I would start.

The Trump administration is to fast track development of a lunar nuclear reactor.
https://www.zerohedge.com/geopolitical/ … actor-moon

This is expected to be a 100kWe system.  This would also be useful in supporting Mars mission and allowing ISRU propellant production.

Solar wind sails with dynamic soaring could propel a spacecraft to 6900km/s - 2.3% of the speed of light.
https://www.nextbigfuture.com/2025/08/b … aring.html

That would get us to Proxima Centauri in less that two centuries.  To Barnards Star in about three.  This is a tool that really could be used for starflight.

This is how the tumbling machine will work.

The tumbling pot is inside the central nacelle.  The wind blows through the blades spinning the nacelle with the tumbling pot in it.  The nacelle with the blades mounted on it is the only moving part.  The weakness in the design is that I will needs to climb 15' up a ladder to change the tumbling pot.

The tower is now in place.

It is mounted on top of a post.  I coated it in creosote and used a post auger to put it about 6' into the ground.

I will need to build a hoist to get the cradle, nacelle and blades onto the tower.  The cradle is finished.

I tied the blades together with a hardwood ring.

This has greatly increased the strength of the assembled nacelle.  Unfortunately, it has also added a lot of weight.

Tomorrow evening I start work on the hoist.