Solar cells: roads versus roofs
From Wise Nano
taken from http://crnano.typepad.com/crnblog/2005/02/nanotechnology__1.html#comments
This article requires extensive editing but unless someone else does it first, I'll have to do that later.
This was sparked by mohit asking, "how far do use see the scope of nanotechnology as a fuel as well as a energy source?"
Molecular Nanotechnology (MNT) and Molecular Manufacturing (MM) will not be fuel sources in and of themselves. Rather, the technology will enable the production of incredibly sophisticated products. As a fuel source, MM will allow the production of extremely inexpensive solar cells as well as efficient long-lasting batteries (maybe hydrogen fuel cells?). I personally feel that with the advent of a MM capability, the vast amounts of energy generated by the sun will cause other large-scale means of energy generation (hydroelectric dams, wind power) to become secondary. For instance, CRN has pointed out that the US has many square miles of roads all over the country; if we had the technology to produce diamond encased, networked solar cells on every square centimeter of that roadway:
1) Maintenance would be virtually unnecessary due to the extreme strength properties of diamond,
2) The area covered could potentially generate the energy currently consumed by the US and require no more area than is currently being utilized,
3) Power circuits could be integrated into the roadway, effectively eliminating the need for power lines along the side of these roads.
Without a need for power lines along every stretch of road, we've GAINED useable land, in addition to land currently used by power plants and the like which would become obsolete.
- Martin
Martin -
If such a thing as a diamond-covered solar cell roadway were to become available, I'd expect you'd see a strong lobby from current power generators' organizations against it (with the possible exception of the oil and/or coal lobbies, if the initial diamondoid materials are based off of petroleum- or coal-derived carbon, and if these companies didn't see the writing on the wall.)
Additionally, being diamond is not a perfect fix to structural issues - there're still the planar weaknesses crystalline structures exhibit. (Look at how traditional diamond facetting is done, for instance - with a medium-strength rap)
I'd wonder how well diamondoid solar cells would work under snow, sand, oil, and other materials you could expect to build up over roadways. Would it get slippery in the rain? Would it potentially short out over swamplands or in the rain?
However it might not necessarily need assembler-style tech, altho' that might be the most efficient way to make such devices. Simple 'tiles' of diamondoid with buckytube conductors could be plant-fabricated and sent to construction sites.
-John
John,
I don't deny that MM "could severely disrupt the present economic structure, greatly reducing the value of many material and human resources, including much of our current infrastructure. Despite utopian post-capitalist hopes, it is unclear whether a workable replacement system could appear in time to prevent the human consequences of massive job displacement." as presented at http://crnano.org/dangers.htm I'm feel corporations will likely be reluctant to accept a technology which will eliminate any need for their products.
I also agree that diamond is not a perfect fix to structural issues. I'm saying that a diamond coating of roadways will not hinder the structural integrity of the road while enabling solar cells to operate without utilizing any extra land. Currently, vast arrays of cells can be networked for electrical power, like at a school down the block from me, or they can be fastened to rooftops, like they are on my roof. The difference being: The school down the block has to use valuable space to generate their power, while my roof can be used both as a roof and a power source.
The idea behind the having 'solar roads' is that there is such a large area generating power that shadows from cars, trees, buildings, environmental conditions, etc. limit the total power generated per day to a point still well above the power consumed per day. If the roads in one part of the country are all covered by snow, in another part they are covered by sand, somewhere it's raining, somewhere birds fly over the road, animals cross the road, and all over the country roads are spotted with oil (which would be phased out if electricity were as plentiful as this idea implies), and anything else that is happening over the road, the total power generated by the entire country is still greater than the total power that is consumed. The problem of rain is nonexistent: we have solar cells that are perfectly capable of operating (much less in danger of shorting out) in all weather conditions.
In his paper “Design of a Primitive Nanofactory†on page 49, Chris points out that ,“a square mile of desert land receives more than 500 MW of solar power [I assume he means ‘per day’] (including night and seasons)â€. I don’t know exactly how many square miles of road are available or how much energy is used by the US each day, but the idea is a good one.
MM would definitely make production less expensive and it could be programmed to automatically repave roads with this material, but you’re right, your idea of plant fabricating ‘tiles’ would be remarkably useful in countering peak oil (again, assuming we switch to electrically powered transportation) if it were not for the industries you have previously mentioned; unless “they†were to own the patents, factories, and tiles, any such proposal would be met by intense opposition.
- Martin
While straight diamond crystal can indeed be cleaved, that's not really a problem. There are two basic approaches that could be taken, or even combined:
1. Tempering. Glass, you may have noticed, is also subject to fracture, in fact it's quite brittle. But if you make a glass object such that it's interior is in tension, and surface is in compression, then cracks originating on the surface are forced shut by the compression, and cannot propagate into the interior. The same can be done with diamond, though building stressed structures could be tricky.
2. Crack stopping microstructure. There are a number of classes of intermediate structures which tend to stop cracks from propagating through a brittle solid, by providing voids which terminate the growing crack. So long as the feature size is small compared to light, they'd have little effect on optical properties.
Now, friction... Rather than trying to make diamond have a high coeficient of friction, and keep the roadbed clean to enhance light transmission, it would be simpler to just roof over all the roads, and do the solar power on the roof. It would certainly have advantages in areas with bad weather...
- Brett
Brett,
I was assuming that the problem of cleaving the diamondoid was limited to crashes/accidents in which an object became airborne and slammed into the road. In that sense, a crack through the surface and circuitry would be a problem. Such an instance would necessarily require some sort of repair, especially if the circuitry was damaged.
Points 1 and 2 would seem likely candidates to strengthen the cells, though I'm sure other properties could and probably would be implemented.
As far as the simplicity of constructing roofs for all roads everywhere versus the simplicity of a high coefficient of friction, I'm unconvinced.
Keeping with the tile idea and assuming the ability to automate the nanofactory’s locomotion along a predetermined route, satisfactory tile placement, ability to observe and compute road curvature and camber, etc., I would think that programming an onboard computer with a few basic properties would be less expensive and require less effort than designing appropriate-height supported shelters for roads. Basic properties of nanofactories producing roadway solar cells might include:
1) The nanofactories are solar powered.
2) Each nanofactory has enough solar cells to recharge its battery in 8 hours and a battery unit capable of storing 36 hours of operating power (for use at night and in case of inclement weather).
3) Nanofactories, their solar cells, and their batteries (utilizing any stored energy of course) can be produced and cannibalized on site depending on the width of the road.
4) Each roadway cell is composed entirely of carbon taken from the surrounding environment.
5) Each roadway solar cell has a similar shape with the solar cell tile in which it is embedded (for my purposes I'll assume this to be only parallelograms and trapezoids).
6) Each cell is oriented with one positive and one negative electrode on each side, which can be connected to adjacent cells or to circuits running along the edge of the tiles.
7) Infrastructure access can be pre-programmed (power monitoring stations, power line junctions, etc.)
8) Each cell is networked within the tile and can be networked with any other adjacent tile, regardless of it’s shape, provided that the common side is aligned and of equal length (for simplicity).
9) Each tile design has a surface ‘fingerprint’ designed for the shape of the tile so that any curvature in the surface of the road will necessitate a grooved surface at the mm to cm scale designed to increase friction of centrifugal forces and provide the greatest traction in order to maximize a vehicle’s centripetal force. For instance, a trapezoidal shape for curves would have its smaller side towards the inside corner regardless of the direction of the curve; no matter which direction you turn, the surface would always be designed to have greatest friction moving from its smaller side (inside of the curve) toward its larger side (outside of the curve). Square and rectangular tiles might have designs similar to what you see on tire treads today.
With this simple outline, it seems possible that each tile would have a surface explicitly designed to aid traction in the expected direction of motion. Also, this method is analogous to repainting the roads rather than building a long and tall covering that accomplishes the same objective.
Some drawbacks of this may be that:
1) Hauling around batteries and extra solar cells may be prohibitively inefficient.
2) Cannibalization and production of factories may occur far too often… maybe they aren’t cannibalized, but instead creep along with the rest of them until they come upon a fork in the road.
3) Carbon is omnipresent, but it may not be easily accessible to a nanofactory without some kind of processing system, which would add to the bulk and inefficiencies.
4) I’m no electrician, so I may not be truly grasping the scope of electricity these panels will produce. What size wiring will be required for such a load and will it be possible to network the entire country, not to mention the resistance within the wiring and the heat generated by that resistance.
5) What would need to be programmed for infrastructure? I have no idea how you could pre-program where to build external electrodes and the like.
In defense of your roof suggestion I would like to examine a few basic properties of nanofactories producing a road covering with solar panels built into it. Again, assuming the ability to automate the nanofactory’s locomotion along a predetermined route, satisfactory tile placement, ability to observe and compute road curvature and camber, etc..
1) The nanofactories are solar powered.
2) Each nanofactory has enough solar cells to recharge its battery in 8 hours and a battery unit capable of storing 36 hours of operating power (for use at night and in case of inclement weather).
3) The roof structure is composed entirely of carbon taken from the surrounding environment.
4) The roof structure is supported by pillars/columns/beams that are somehow anchored to the ground (driven into the ground maybe?).
5) The roof structure is never less than 20’ above the surface of any part of the road. (trucks)
6) The structure is capable of withstanding the elements.
7) The nanofactories can orient themselves with regard to magnetic (or true, which might be slightly more difficult) North.
8) Solar panels are not built into any roofing that faces north. Solar panels are built into any roof that faces East, South, and/or West.
9) All solar panels are networked and enable infrastructure access.
Some advantages of this method are that the cells are less susceptible to dirt and sand hindering their performance; though wind can blow these materials to that height it is highly doubtful that this would be a serious problem. Building a roof structure in which the panels are much closer to directly facing the sun than would be the case for a road, would cause the panels to be immensely more efficient. Instead of having an A framed structure (which could potentially protect drivers from water and snow) you could get much more bang for your buck if, for East-West roads, you had a kind of lean-to where the top only faced due south and was highest on it’s northern side. I’m sure other designs could take advantage of other orientations.
Some drawbacks of this may be that:
1) Hauling around batteries and extra solar cells may be prohibitively inefficient.
2) Carbon is omnipresent, but it may not be easily accessible to a nanofactory without some kind of processing system, which would add to the bulk and inefficiencies.
3) I’m no electrician, so I may not be truly grasping the scope of electricity these panels will produce. What size wiring will be required for such a load and will it be possible to network the entire country, not to mention the resistance within the wiring and the heat generated by that resistance.
4) What would need to be programmed for infrastructure? I have no idea how you could pre-program where to build external electrodes and the like.
5) How is the whole thing anchored to the ground?
6) How much weight would need to be supported? How strong would it have to be to support it’s own weight? How strong would it need to be to consistently and repeatedly resist the elements? More importantly, how much human engineering would be required for different road widths?
7) What would need to be programmed with regard to effective use of area facing south when the roadway can weave in any direction?
In conclusion I’d like to look at the pro’s and cons of each and leave the rest up for debate.
Pro’s of solar-road idea:
Increased traction on paved surfaces due to control of surface properties. Small number of designs utilized. Basic idea, nothing more than a new surface with special features. Extended road life.
Pro’s of solar-roof idea:
Possible emergency shelter. Immensely more efficient than solar-road cells. Marginally to markedly more power generated due to less shadows and less solid materials piling on top of the solar cells. Possible exploitation of ability to aim the cells at the sun.
Con’s of solar-road idea:
Questionable efficiency regarding nanofactory power source Factory size and cannibalization/production unclear, as well as what happens to the factories when production is complete. May require processing system to utilize carbon from environment. Unclear how infrastructure could utilize the resource. The designs of each tile shape and composition must be programmed in advance.
Con’s of solar-roof idea:
Questionable efficiency regarding nanofactory power source May require processing system to utilize carbon from environment. Unclear how infrastructure could utilize the resource. The designs of each road width must be programmed in advance with specifications regarding strength of support beams and orientation with respect to due south. Unclear how the structure would be anchored to the ground.
