Advanced tech without electricity/internal combustion?

Cheopis wrote:

Weird Harold wrote:On your metal-poor world, optical quality glass might make sense, but Safehold isn't metal-poor so metal mirrors or glass mirrors with metal "silvering" would be far cheaper and manageable than lenses. Especially if you want something bigger than a solar "easy-bake Oven(tm)"

I responded to this with the post immediately above this post, I think. Like mirrored surfaces, a large array of prisms could mimic a very large Fresnel lens, without metal.

Even without metal for "silvering" it would take less glass and less perfection to build a reflective array than it would a refractive compound lens. Adequate mirrors could be made from opaque glass or simple non-metallic paint on glass sheets.

You also have to consider solar-tracking -- your proposed design would only provide decent power for about an hour either side of Noon unless you build a boiler that can track the focal point. A mirror-array has a lot less mass for any given amount of solar concentration and consequently can be made to track the sun with a lot less effort; one slave in a tread-wheel pivoting an acre or so of mirrors, or something similar, would be manageable. Tracking your multi-ton, multi-element rooftop installation would require a lot more effort.

Thucydides wrote:Frankly, land is too valuable to be covered in mirrors, photovoltaic panels, Fresnel lenses and so on, particularly when there is no ROI when it rains or when the sun goes down.

The land best suited to Solar Power Arrays is not good for much else. Unfortunately, it is also usually a good distance from where the power is needed.

Experimental installations like Solar 2 test possible ways of storing energy as well as technology for collecting it. Where renewable resource technology is currently lacking is a viable method of transporting stored energy.

JRM wrote:
I saw an attempt to redirect the thread, but I wonder if we shouldn't post a new thread to determine the demographic weight of current and former Ranger owners.

I admit that I have a 97 Ranger with 155,000 miles.

Keep driving. Lots of wear left there.

Don

Weird Harold wrote:Even without metal for "silvering" it would take less glass and less perfection to build a reflective array than it would a refractive compound lens. Adequate mirrors could be made from opaque glass or simple non-metallic paint on glass sheets.

You also have to consider solar-tracking -- your proposed design would only provide decent power for about an hour either side of Noon unless you build a boiler that can track the focal point. A mirror-array has a lot less mass for any given amount of solar concentration and consequently can be made to track the sun with a lot less effort; one slave in a tread-wheel pivoting an acre or so of mirrors, or something similar, would be manageable. Tracking your multi-ton, multi-element rooftop installation would require a lot more effort.

Think about the precision required for a very large array of reflective mirrors that can track the sun. Part of the reason this type of solar mirror array isn't commercially successful yet is because it's expensive. The more precise and efficient you want it to be, the more expensive it is and the more expensive your energy will be, either money-wise or resource-wise.

Additionally, the lens method would certainly use a linear element to absorb heat, and the focal point would shift throughout the day, much like trough-style reflective solar elements today.

Additionally, and this idea just popped into my head, there would be nothing stopping you from having the system be three sided, not one sided. The building could be built like a greenhouse, arched, and the lenses would be shifted through the course of the year. On Earth, if you are in the Northern hemisphere, as Winter approaches, your flattest lenses would be adjusted south, row by row. Yes, you would lose a lot of energy, but you could make it work reasonably well.

OK, this is definitely making it into paper in what I'm writing. During the winter it will probably just heat water, perhaps even enough water to keep a house warm. In the summer, it might provide power for, say, processing crops or making tools, or whatever.

Mirror solar systems also concentrate solar power by having a concave surface facing the sun, and concentrating power at an exposed surface between them and the sun. This makes them more vulnerable to bad weather. On the other hand, lens solar systems can concentrate light from many shapes, and some of the most efficient will be concave, with the object of the concentrated light being protected and insulated under the structure that holds the lenses in place.

If you're going to do small-to-moderate-sized primitive solar thermal energy without the ability to make cheap, efficient mirrors, I really think lensing power would be more effective than reflecting it. If you can make cheap, efficient mirrors, it becomes a different scenario entirely. If you can make cheap computers and cheap servos, then massive arrays of mirrors becomes even more attractive.

Since they can make corrective lenses, Safehold clearly has a fairly advanced glass industry. They are probably at the cusp of having mirrors be better than lenses for solar energy.

With the glassmaking industry being what it is, and with heliographs being used, I'm a bit surprised no Mother Church members have thought about trying to use lenses to burn Charisian sails. Trying to do it at sea probably wouldn't work that well, but setting up mirrors, lenses, etc in placed where you expect an attack?.

Weird Harold wrote:

Thucydides wrote:Frankly, land is too valuable to be covered in mirrors, photovoltaic panels, Fresnel lenses and so on, particularly when there is no ROI when it rains or when the sun goes down.

The land best suited to Solar Power Arrays is not good for much else. Unfortunately, it is also usually a good distance from where the power is needed.

Yeah, it's not good for everywhere. Europe & the Eastern US tends to have a lack of deserts = more expensive land and less sun. Also, high latitudes mean very little sun in winter. Spain, France, etc. are possible but still fairly high latitude (Madrid 40, Paris almost 49).

Canada, Russia etc, are very high latitude.

The US Southwest, parts of Mexico, the Middle East, North Africa are good since they have deserts (very cheap land and lots of sun) very near the cities and are low latitude. Maybe Australia too.

cralkhi wrote:Yeah, it's not good for everywhere. Europe & the Eastern US tends to have a lack of deserts = more expensive land and less sun. Also, high latitudes mean very little sun in winter. Spain, France, etc. are possible but still fairly high latitude (Madrid 40, Paris almost 49).

Canada, Russia etc, are very high latitude.

The US Southwest, parts of Mexico, the Middle East, North Africa are good since they have deserts (very cheap land and lots of sun) very near the cities and are low latitude. Maybe Australia too.

Why is there this belief that you have to put the solar cells Somewhere Else?

You put the solar panels over the parking lots and roofs you've already created; it's not like that's going to shade valuable growing land. (It's not like deserts don't have interesting and valuable ecologies that we might not want to obliterate.) There's a whole lot of parking lots and roofs in the Eastern US, and having those shaded doesn't do any harm. It doesn't do any harm to have the solar panels where people live and there's infrastructure, either; means less distance to transmit electricity, any repairs are easier, etc.

You put solar panels on the tall buildings, where you've covered the windows with anti-insolation film anyway to get your air-conditioning budget down in the summer. The available film is only about 7% efficient (60% area of a ~12% efficient organic solar cell film) but you were going to do this anyway; the 7% only has to cover the difference between the price of the different light-blocking films, which it does handily.

Also, the best available tech for energy storage where the input is renewables is to make ammonia. Your inputs for ammonia are a lot of water and a lot of air and electricity, so you don't want to be in the desert where there isn't any water. You might, in cases like the Sahara, want to use coastal ammonia plants getting fed power from inland solar arrays, and pipe the ammonia north to Europe.

Places like Canada can go with wind, but not terrestrial wind; there's a lot more wind out over the ocean. So you make sailing ships, drag the prop to generate electricity, and use the electricity to make ammonia. Come back to port when full, pump out, and out you go again. Anybody with a port can do that.

None of this is technically difficult.

Graydon,

I've never even heard of regenerative braking on a boat to generate power. That's pretty darn clever. But why not just use a few windmills over water, and go pick up the ammonia with tankers? I suppose you could make the argument that a mobile generator can move around and put itself at the boundaries of storms and weather patterns.

Definitely interesting. Thank you for that

You need to put the solar cells (mirrors, lenses etc.) "somewhere else" because that is where the sun shine is more regular and continuous than the roof of a parking garage in a place like Boston or Toronto.

You also need to put the cells/windmills/unicorn treadmills elsewhere so that the load can be shifted to maintain grid stability. Having a sudden "surge" of sun power or wind power when there is no demand is bad enough, having intermittent surges because it is partly cloudy or the wind is variable can crash the grid (and large baseline generators like thermal, combined cycle gas turbine, nuclear and even hydro from large dams cannot be cycled fast enough to deal with this sort of thing). You also have the issue of "wanting" to be free of the grid when the sun shines but also "demanding" electrical baseline power when it does not, something which will probably be very costly to consumers (since the economies of scale inherent with baseline power will no longer exist).

What is really needed is large scale energy storage. Current technology provides as much capability as you trying to power your house in an emergency with your laptop battery. The only thing that I can think of that could work at the scale needed would be something along the lines of a Lofstrom loop, where electrical energy is fed in "whenever" , stored as kinetic energy and can be withdrawn "whenever", but without the fluctuations which cause instability in the grid. Of course a Lofstrom loop for even a small city would probably be several kilometres in diameter, and "regional grid" sized units would be visible from space, which gives you an idea of the scale and scope of this. The advantage here is that intermittent, off peak power generation can be stored for use when demand is higher, but solar and wind producers will have to accept much lower prices for energy, since any plan that pays the "Feed In Tarrifs" (FIT) will rapidly bankrupt any private utility, or cause massive financial damage to taxpayers (as is happening in Ontario right now).

https://en.wikipedia.org/wiki/Launch_loop

Graydon wrote:Why is there this belief that you have to put the solar cells Somewhere Else?

You put the solar panels ...

Up until your post, we hadn't been talking about solar panels. Solar Panels can indeed be put just about anywhere there is a wall or roof; some interesting research has been done in Solar Paint that can turn anything into a solar energy collector.

Pretty much ever other solar energy technology requires a lot of regular sunlight and a lot of space -- a lot of "Somewhere Else."

Cheopis wrote:I've never even heard of regenerative braking on a boat to generate power. That's pretty darn clever.

That's why pretty much every sailboat with an auxiliary engine has a folding prop; an unpowered propeller is a drag device. (Why early steam frigates had ways to hoist the prop clean off, too.) The usual term for running a generator off the prop is "shaft alternator", something quite common from the 30s forward as a means of charging the ship's batteries on sailboats. Definitely clever; someone managed to turn a disadvantage into an advantage.

Cheopis wrote:But why not just use a few windmills over water, and go pick up the ammonia with tankers? I suppose you could make the argument that a mobile generator can move around and put itself at the boundaries of storms and weather patterns.

Windmills have a fundamental problem; you're trying to get optimal power extraction (foils as light as possible) and durability (heavy, overdesigned foils) from the same set of rigid foils. Pretty much any windmill that is good at producing power is bad at surviving a hurricane. (Derecho, local thunderstorm, the jet stream is drunk, etc.)

Sails -- even very modern wing sails -- can be optimized for dealing with a broad range of wind speeds, and the prop can be optimized for generating power from the much denser water at a given hull speed, and you don't have to try to produce some difficult and doubtful compromise between power extraction and durability with one set of rigid foils rotating around a common centre.

Plus, there isn't much wind, relatively speaking, anywhere you can easily anchor a windmill. If you seriously want to use wind as a source of energy, you need to go where the wind can be found.

Take a look at http://earth.nullschool.net/ for a roughly-real-time depiction of the global wind field. Lots more wind out over the oceans.

Cheopis wrote:Definitely interesting. Thank you for that

Thank you!

It's one of my favourite renewables proposals -- it's not like we don't know how to build sailing ships. It'd employ people. Direct-ammonia-fuel-cell powered electric cars have less power train mass than gasoline and ICE for pretty much any range, and as everything improved the price of energy would tend to come down. Plus we need the ammonia for fertilizer. It's nice clean catalytic tech.