[geeks] $100 One Laptop Per Child - grist for the mill

[Phil Stracchino]

Geoffrey S. Mendelson wrote:
> On Sat, Nov 18, 2006 at 09:41:21PM -0600, Brian Dunbar wrote:
>> Okay, so I know this isn't 'the' solution but it could be 'a' solution.
>>  I wonder if Solar Power Satellites could supply that need.
> 
> Possibly, but it's an awfully expensive way. For example lower cost systems
> may be better at least at first. Passive solar systems would be a lot
> cheaper if you could come up with something that was much cheaper than the
> photovoltaic (solar cell) electrical systems.

I can't find the link right now, but I read an article recently about an
outfit that's developing a truck-portable sun-tracking heliostat for
solar-thermal power generation.  If memory serves, they were talking in
terms of a fully automated unit about four meters tall by three in
diameter with an output (at central-US latitudes) somewhere in the range
of single-digit kilowatts.  They can be ganged in parallel to create
solar power farms if needed, but the target market is residential users
and businesses who want to unplug from the grid.

I don't know how cheaply they could be produced, but one of those plus a
bank of storage batteries could *run* a power grid for a third-world
village.  Enough, at least, to provide everyone with electric light.


Another idea that occurred to me is, instead of a hand-cranked
generator, how about a treadmill one?  If it's properly designed, you
should be able to have people walk on it, or tether an ox on it, or
strap bicycles on it and have people pedal, or if someone stops in the
village with a Land Rover, have him back it onto the rollers and let it
idle in second or third gear for twenty minutes or so.

In either of these cases, power storage could be via a battery bank, or
via some kind of mechanical "storage battery".  Geared motor/generators
to wind up a really big spring, say, or a swashplate pump/motor
connected to a motor/generator to compress air in a big tank.  If water
supply is assured, you could even store energy by pumping water up into
an air-pressurized holding tank, and let it turn a Pelton wheel.

In the case of the heliostat, you could even use thermal storage:
primary circuit from the heliostat dumps heat into a really big
insulated heatsink, secondary circuit takes heat from the heatsink to
drive some kind of heat engine, which would probably be a Stirling
engine.  The drawback of this, of course, is that the system would
produce power most efficiently when its "heat battery" was almost empty,
and progressively lose efficiency as the heatsink heated up.



-- 
 Same geek, same site, new location
 Phil Stracchino                     Landline: 603-429-0220
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 Renaissance Man, Unix generalist, Perl hacker, Free Stater