At 10:06 PM 12/23/2004, Jeff Condit wrote:
I don't know all the ways various slowdown amounts would affect various things, but clearly at some point it would affect the weather and climate.
Yes, of course. The real question, though, is whether or not any reasonably likely implementation of tidal energy generation would make a noticeable acceleration in the slowdown. My sense is not. The earth's rotation is already slowing by, I found, 1.5 milliseconds per century, due, I presume, to tidal forces from the earth and moon.
One estimate I saw shows that throughout history natural tidal friction loses about 1023 J per century.
Which corresponds, then, to a slowing of the day by 1.5 milliseconds
However, most of the tidal surges are in places which are broad, and the water is free to flow in and out over the entire period with relatively low flow rates and very little elevation change across the system. Damming up the natural system prevents this flow until the peak tide where there is an elevational difference if many meters across the dam.
Damming the system globally could, I suppose, increase effective tidal friction substantially. However, such massive tidal projects are not, to my knowledge, being contemplated.
As of 1999 the DOE estimate of global energy use was 4.02x1020 J but increasing rapidly with emerging 3rd world infrastructures. I don't have a more recent number, but worldwide efferts to curb this energy rise may have had some effect. Thus at the current usage we may be slowing down a second per year every decade or so.
Doesn't this assume that all the energy is coming from an increase in tidal friction? Which is not even close to true?
You can do your own studies if you like. What I don't like is that this is never talked about.
*This* particular problem is a long way from raising its head.... Nearly all energy generation does not increase tidal friction at all. Only if truly massive structures were created could a significant effect be created on tidal friction. Further, some of the energy that would be generated would simply be a substitute for energy expended in raising the earth's temperature due to tidal friction. Instead of the heat from the movement of the tides being dissipated in the shoreline and ocean, some of it would be converted into power and dissipated remotely. I don't find it obvious how much a power generation system would necessarily increase tidal friction, even if massive. In other words, all that tidal movement already interacts with the shore and the ocean itself to generate heat; the energy of this heat is subtracted from the rotational energy, thus slowing the earth (and, as it happens, speeding up the moon). A tidal generation system would not necessarily generate more heat, it would depend, I would guess off-the-cuff, on the exact design.
But even if the increase would be substantial, the project would have to be by far the largest thing ever constructed by humans in order to have a significant impact.
I'm all for anticipating environmental consequences, but I think this one is not realistic unless a *huge* effort were put into constructing massive systems, and presumably, before anything like that were done, there *would* be consideration of the consequences. It would take a long time to build the system, plenty of time for people to notice the problem and object.
I think the effects from heating the earth due to solar collection are more likely to be significant, but even there, the effects would still be much smaller than what we get from altering the atmosphere by emitting CO2.
The studies I have read on planetary atmosphere kinematics indicate wind patterns are a product of both tidal effects on the atmosphere and daily heating cooling cycles. As a result, harnessing wind would probably have a lesser effect on the rotational kinetic energy.
Again, much less, because wind systems are not going to cover the massive areas that are involved in tidal friction.
In large desserts the ground normally reflects a certain aomunt of radiant energy back into space while absorbing some as heat. If large solar atrrays in the dessert could the same anount as the normal soil, then to overall heating of the Earth would be unchanged.
But this is unlikely. Large solar arrays would, I believe, necessarily have a lower albedo, substantially, than your default desert surface. However, I *still* think that the effect will be small compared to the atmospheric ones that we are already "enjoying."
The difference would be that energy would be transferred from the dessert to other clode-by wetter areas where people live, thus the dessert would be a bit cooler while the surrounding areas would be a bit warmer.
I don't think the desert areas would be cooler. They would be warmer, unless somehow it is managed to get very high efficiency in energy conversion. And so would the areas to which the energy collected is transferred.
Note that my own preferred futurist scenario for energy generation would be satellite solar power. In this case, the energy is collected in space, albedo is not a consideration. The collection antennae would be effectively transparent to radiant heat; so, while there would be some local heating in the area of an antenna, it is quite possible that the use of the land underneath the antenna would be such as to increase albedo, thus lowering solar heat retained. So the net effect in the area of the collection antennae would depend on the land usage underneath the antenna. (The L5/Oneill/SSPS people suggested using it for agriculture, which might lower albedo, but it does that anyway....). The efficiency of the energy transmission system from space to earth was projected at about 90%. I don't know what portion of that ends up as heat at the receiving antenna. But there is, unavoidably, heat generated at the point of energy use. Again, however, if this were large enough to be of concern, it might be possible to balance it by arranging for increased reflection of solar energy reaching the earth, back into space. For zero net effect.
This could cause weather shifts and slight local climatic changes, but the global effects would be minimized. Of course, this approach would never be taken because solar power is expensive, and so is driven by economics which mandate maximum power conversion per $ invested, resulting in dark colored panes that do not reflect much of their incident radiation on purpose.
Yes. If the solar collection panels are at earth surface, I think this is unavoidable. However, if they are in space, it is not a relevant concern. The waste heat would be reradiated from the panels into space.
It has been stated that the Earth regulates its own temperature via increasing cloud cover as global temperatures rise. This is a negative feedback system. However, geologic evidence indicates the duration of ice ages is long, which in turn suggests the Earth has at least two stable states, not just one. (Stable in the shorter term; since the ice ages come and go in the long term.) Thus if the Earth gets covered with clouds and subsequently cools down, it does not necessarily lose its cloud cover for a very very long time even though it gets cold. I think we need to be focussing on harnessing the renewable energy flowing around the planet and redirecting it in constructive ways that do not alter the global energy budget. We should not be beaming in copious amounts more from satellites, or messing with planetary kinematics, regardless of who's $ is talking. And we should not be boosting the conversion of convenient stored energy well beyond sustainable levels except (perhaps) to promulgate an exit from an ice age.
Satellite solar power should have no effect on planetary kinematics. It should also, properly implemented, not change the earth's heat budget. Yes, like all energy usage, it will add heat to the environment, but it is not this heat which is really the problem today, and that contribution could be balanced rather easily. The serious problem is the change in the atmosphere from fossil fuel burning, which then causes changes in heat retention by the earth, thus leading quite likely to global change. Satellite solar power could contribute, in the construction phase, to atmospheric change, from massive booster exhaust gases; however, the bulk of the construction in the L-5 conception was to take place from lunar materials. The engineering was worked out over twenty years ago; the obstacle was not practical, nor was it economics, really, but politics.
____________________________________________________________ You are subscribed to the OT discussion forum
To Post messages: mailto:[email protected]
Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/ot_techservinc.com
Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected]
Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
