Solor Power on Venus

[joncee1949]

Forgive me if this is a stupid question, but here it goes anyway. I you were able to land a craft on the surface and find ways to deal with the adverse heat, would it be possible to use solar cells to trickle charge a battery? I know the cloud cover is pretty dense, but would enough solar energy get through the atmosphere to be of any use? I am not looking for a solution to power anything large, maybe only a probe. Any other suggestions of ways to recharge the on-board probe batteries? <br />

 

[vogon13]

You could have the photovoltaics on a balloon, and the instruments could be lowered from the balloon to lower depths for study, and the instruments could be reeled back up when they became too warm, and then you could use them somewhere else after the balloon drifted some more.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mlorrey]

The cloud cover begins at something like 60-80 miles altitude, and extends for a few hundred miles above that.<br /><br />You would need to orbit or float a solar powered baloonn above the cloud cover, and beam the power down with a microwave beam via masers. This would also necessitate a pretty good sized rectenna receiver on the ground. <br /><br />I would say it would be far more feasible to operate with a nuke plant that operates with a liquid metal coolant, like sodium, lead, etc.<br /><br />My personal preference is to station a large shade of solar cells in the Venus-Sun L1 point, large enough to cast a shadow over at least 50% of the dayside of the planet. Power generated would be split up: a small percent going into maser beams to surface probes and floating balloon stations. The rest would be used to beam power at Mars to help warm it up.<br /><br />Floating balloon stations would feed on CO2 in the atmosphere to build ballast of CNTs that would be used to build skyhooks. While some could be used for transportation, because of their thermal conductivity they could also be used to help cool Venus' atmosphere in a massive terraforming project, while at the same time sequestering CO2 out of the atmosphere. In particular, as additional older skyhooks are built, older ones would detach from the surface and drift into space, and could then be transported to Earth, the Moon, Mars, thus permanently removing that carbon from Venus.<br /><br />Venus currently has 92 Earth atmospheres. Orginally Earth had about 52 times what it has now, but most of it was sequestered by life into limestone. Since Venus never developed life, as it was too close to the Sun, it never got that help. Reducing Venus' atmosphere to somewhere around where Earth started off at, engineered life forms should be able to be introduced to take over the process from technological systems and accelerate the change given the exponential replication capabilities of biological systems.

 

[rocketman5000]

mlorry, I hope to see that day. Could you create carbon nanotubes directly from CO2 or would you have to transform it to another medium say graphite to create them. Aren't nanotubes currently constructed from graphite? <br /><br />I believe that if your interest is terraforming however it would be way easier to create a mirror for increasing the flux at mars and decreasing it at Venus. Creating the power need at the source through photovoltaics would require about the same amount of infastructure as needed for rectennas and conversion to electricity.

 

[pocket_rocket]

At the high temperature found on venus, I would think that thermovoltaic means would be adequate for low power probes. I'm not up to snuff on new technology in thermocouple devices.

 

[vogon13]

There has to be a temperature difference across a thermocouple for it to work. A thermocouple on the surface of Venus won't work after it is in thermal equilibrium with it's environment.<br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[chriscdc]

There was a paper that I read recently in nature that used a direct CO2 method to produce a Single walled tubes with a large number of semiconducting tubes, but I can't find it again and I couldn't open the full paper from where I am anyway.<br /><br />The main method for producing tubes are from methane, so if you have a good source of Hydrogen, such as sulphuric acid on venus or ice on mars, then manufacture should be easy. You just need to pass it over iron particles (in an atmosphere consisting of a noble gas).<br /><br />One cool way to heat up mars would be to use balloon mounted Ion drives in the upper venutian atmosphere. The velocity of the particles need not be that high eg the escape velocity of venus, some current drives operate at ~20 times this velocity.

 

[mlorrey]

I don't think heating up the upper atmosphere is the way you want to go: the heating is needed at the ground level to trigger outgassing of CO2 from carbonate rocks. Upper atmosphere warming will not help this at all, it will only help in boiling off more atmosphere to space.<br /><br />I agree it would be easier merely to reflect the sunlight at Venus, but Mars is not always in line to use that effectively, the more you tilt the venus mirror to hit mars for more of its orbit, the less shading of venus that occurs. With electric conversion and maser beaming, you can direct the energy in multiple directions as needed, for many different spacecraft as well as at Mars, possibly at interstellar missions as well.

 

[pocket_rocket]

I stand corrected.

 

[chriscdc]

Huh.<br /><br />I think there was a miscommunication. I was just saying that one way to get a green house warming effect on mars would be to transfer atmosphere from venus to mars and partially kill 2 terraforming birds in one go.<br /><br />Actually using the venutian atmosphere as a source of carbon would be great. Closer to the sun so even more effective solar power. If you can use the carbon itself as the substrate for a solar power cell you could make balloons out of them and fill them with the hydrogen that you get back after the formation of the tubes. As long as you get more power out of the system than you put in for creation or maintence then it would be worth it.

 

[mlorrey]

Yes, transferring carbon to Mars would be a way to go. Deciding whether to ship it as dry ice (solid CO2) or CNT or just graphite is a designers choice. Given 3-5 degrees warming (i.e. done by our venus maser service), enough outgassing should occur as part of a vicious cycle to boost the atmosphere to about 500 millibars pressure within 30 years and enough greenhouse effect to replicate climate in Lhasa, Tibet. The atmosphere would be all CO2, though, so people would need to walk around with oxygen masks outside.<br /><br />This would be a lot cheaper way to get a lot of CO2 into the mars atmosphere than shipping dry ice across the solar system.<br /><br />Adding more carbon from Venus may help, but ideally Mars needs more nitrogen. There is solid frozen nitrogen on Titania, and I suspect other KBOs have similar stocks. This may be a situation where lightly dropping a nitrogen rich KBO on Mars would be a smart idea: not only in adding nitrogen that would be needed by any life forms we introduce, as well as in filling out the density of the atmosphere, but the impact heat would also warm things up. A few hundred cubic miles of nitrogen ice should result in several tens of thousand cubic miles of gaseous nitrogen.<br /><br />I don't believe there is much nitrogen in the Venusian atmosphere.

 

[nexium]

According to a very old article on terriforming Venus, there is almost 1% nitrogen in the Venus atmosphere which is the correct amount, if we get rid of nearly all the carbon dioxide without losing nitrogen. The carbon however would make a layer 600 feet thick covering all of Venus, which would be a major fire hazard if we make a 21% oxygen atmosphere. There are a bunch of problems such as not enough hydrogen to make the water for a small ocean and an acquifer. Neil

 

[mlorrey]

Yeah. If the carbon lands as graphite or CNT, there is a major problem with it being a fire hazard: the amount of sulphur in the atmosphere also means that you'd be building a planetary surface of gunpowder. Here on Earth our ancestral life forms turned that carbon into coral, which became limestone, and is now the major part of our continental rafts. Once we get Venus atmospheric pressure below 50 bars, we can introduce life forms that will start that process, but you are correct regarding hydrogen requirements. This is another application where generous use of KBOs would be a help: adding water while using the impacts to drive a significant percentage of the atmosphere into space at escape velocities where the solar wind can carry it away. This process is referred to by Martyn Fogg as "impact erosion". If the KBOs strike at the right points and angles, this would also help get Venus to spin a bit more. Debris blasted into orbit would form a ring that would provide more shading effects, and eventually would coalesce into a moon that would increase Venus' rotational speed by tidal effects.

 

[chriscdc]

Actually the transfer process was what the ion drives were for. In this case though the iondrives are pointing their exhaust towards mars<br /><br />It wouldn't be efficient but you could tailor the ion drives to only direct the nitrogen atoms at mars whilst the other molecules/atoms would miss. You could do the same for oxygen etc.

 

[rasun]

Sunlight at the surface is weak, but that only means you'd need more solar cells. But do they work at all at 450 C?<br /><br />Based on this document:<br />http://gltrs.grc.nasa.gov/reports/2005/CP-2005-213431/27Landis.pdf<br />it seems that even if you could exrtapolate the data to 450 C (and still not burn the solar cell) their efficiency would be reduced by at least 75% (compared to 0 C).<br />

 

[nexium]

We have not tried as far as I know to make solar cells that operate at 450 degrees ambient. Likely it is possible, but only one or two watts per square meter is available on the present surface of Venus, unless we can convert far infrared to electricity. Neil

 

[qso1]

Not a stupid question at all.<br /><br />Currently, its not practical in part because there are a lot of components within previous Venus surface craft that can only survive a couple hours. Once the extreme heat permeats the craft, there is no way to radiate it away. Venus probes launched to date have not had active cooling designed into them AFAIK.<br /><br />Someone mentioned that solar cells would loose 75% of their efficiency under such brutal conditions. IIRC, solar cells in general are only 15 to maybe 20% efficient to begin with.<br /><br />Solder circuits would melt after a couple of hours or so. Any moving components would generate excess heat and eventually fail under such punishing conditions. This is the reason Venus surface probes are so short lived.<br /><br />We will probably have to rely on future advances in all technologies across the board to have a long term probe that will operate on the Venusian surface. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[mithridates]

Just a note to remind everybody that the temperature is only 450C right at the surface; around 8 to 10 km above the surface where the highest mountains are it's slightly under 400C and the pressure is about 50 times that of Earth instead of 90 times. Still formidable but significantly less harsh than the conditions below. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[MeteorWayne]

Oh yeah, 400 C is "cool" with me <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>