1 Steam Cars : Phorum
General Steam Car topics
solar cars revisited
Posted by: tom ward (IP Logged)
Date: May 10, 2002 08:13AM
<HTML>I recall reading about use of solar heated oil as an energy medium on thjs site. I suggest a modification of the system. While the oil approach may cost less at the start it does not take advantage of latent heat of fusion which could either reduce the volume and mass involved or extend range. If thousands of ceramic beads filled with molten metal or salt were dumped into a pressure vessel with a water injector near the bottom and a steam out let near the top you would have a boiler which is simple to construct and has an enormous exchange area to volume ratio. Add a second vessel with ice filled beads as a condensor and you have a system completely isolated from the atmosphere. This makes possible a more a more aerodynamically efficient vehicle.
Beads when taken in the thousands will flow just like a liquid and therefore could be drained and filled and pumped just like oil.</HTML>
Beads when taken in the thousands will flow just like a liquid and therefore could be drained and filled and pumped just like oil.</HTML>
Re: solar cars revisited
Posted by: Peter Brow (IP Logged)
Date: May 10, 2002 08:53AM
<HTML>Hi Tom,
Interesting idea. The Robert McElroy system, described on the "Solar Steam Car" page at my website, does seem to use latent heat of fusion, in that the "thermal liquid" was described as an asphalt-like material which underwent a phase change (between solid and liquid) during heating or cooling. However, the latent heat of fusion of metals might be higher per pound. Sodium in sealed pellets might be nice -- until the pellets wear and leak. Then the steam generation rate would really take off! Or perhaps molten lead inside of steel pellets. Some calculations on the recoverable heat per pound of weight of various heat-storage media would be useful.
I've done some math on bead-type heat exchangers, and yes, the weight/volume per unit of heat-exchange area can be amazingly low with small beads -- esp around the size of BB's. Then again, most heat battery systems operate with much lower temperature differentials than steam generators fired with hydrocarbon fuels, so much more heat exchange area is needed for a given steam output.
Bead-handling systems tend to be noisier and more prone to wear than liquid-handling systems, but there may be ways to reduce wear and noise to acceptable levels.
Small size and light weight have been claimed with phase-change molten salts as heat storage media, but these tend to be toxic, costly, and/or highly corrosive.
Peter</HTML>
Interesting idea. The Robert McElroy system, described on the "Solar Steam Car" page at my website, does seem to use latent heat of fusion, in that the "thermal liquid" was described as an asphalt-like material which underwent a phase change (between solid and liquid) during heating or cooling. However, the latent heat of fusion of metals might be higher per pound. Sodium in sealed pellets might be nice -- until the pellets wear and leak. Then the steam generation rate would really take off! Or perhaps molten lead inside of steel pellets. Some calculations on the recoverable heat per pound of weight of various heat-storage media would be useful.
I've done some math on bead-type heat exchangers, and yes, the weight/volume per unit of heat-exchange area can be amazingly low with small beads -- esp around the size of BB's. Then again, most heat battery systems operate with much lower temperature differentials than steam generators fired with hydrocarbon fuels, so much more heat exchange area is needed for a given steam output.
Bead-handling systems tend to be noisier and more prone to wear than liquid-handling systems, but there may be ways to reduce wear and noise to acceptable levels.
Small size and light weight have been claimed with phase-change molten salts as heat storage media, but these tend to be toxic, costly, and/or highly corrosive.
Peter</HTML>
Re: solar cars revisited
Posted by: tom ward (IP Logged)
Date: May 10, 2002 12:46PM
<HTML>I envsion the beads as being composed of a lead BB wrapped in carbon fiber with a ceramic coating infused around the fibers. The carbon ceramic composite would probably answer your durability questions. Also the ceramic material would be highly corrosion resistant. My hope is that a long life cycle would offset the higher production costs.</HTML>
Re: solar cars revisited
Posted by: Peter Brow (IP Logged)
Date: May 12, 2002 04:40AM
<HTML>That would be a perfect construction for wear resistance; those beads would last nearly forever. But, have you looked at the price of ceramic ball bearings lately? There is also wear in the bead-handling equipment to consider, and I think the heat-transfer rate of ceramics is low. Keep going, though, you may be onto something here. I'm going to see if I can dig up any figures on how much energy we can store in molten lead, and how it compares to oil and some of the other materials, on a pound-for-pound basis. At this point, it does look like a promising approach, though the beads might need steel jackets for affordability & good heat transfer.
Peter</HTML>
Peter</HTML>
Sorry, only registered users may post in this forum.