[extropy-chat] Moving on (was CF research)

Eugen Leitl eugen at leitl.org
Wed Feb 14 14:31:00 UTC 2007

On Tue, Feb 13, 2007 at 10:45:12AM -0500, Keith Henson wrote:

> There are critical industrial processes that just don't lend themselves to 
> distributed solutions.

Yes, but residential energy production (whether a methane motor generator,
a methane fuel cell, a wind turbine, or a roof/facade PV array) is a problem 
space which profits exactly from decentralisation, and in situ production.
In case of heat-power coupling, the transport losses are easily avoided,
and ditto applies to low-voltage, high-current PV power, which otherwise
would need up-transformed for transport, with conversion and transport

The most real advantage is that's a low-threshold technology.
Very different from terrestrial (nanotube) or lunar (aramide) tethers,
linear mass drivers or even cheap LEO launches. While I like them,
nothing helps like low-tech like insulating a house, using heat
pumps and high-efficiency burners, installing solar gardes,
thermal solar collectors, and similiar. 
> Consider aluminum as an example.  An aluminum pot line uses 250,000 amps at 
> 800 volts.  That's 0.2 Gw, if the plant has 5 pot lines, it eats a 
> Gw.  (Metalic aluminum represents about 40 kwh/kg.)  Or consider 
> cement.  Last time I looked, grinding clinker to dust was taking 1.5 to 2 
> percent of the total US generation.

Concrete production along with aluminum (and air nitrogen fixation)
are a major sinks of energy, and large-scale producers of CO2
(doubly so, if you calcinate carbonates). I don't find these
processes particularly sexy, and would frankly wish we would
substitute them with something more hi-tech, and greener.
> And when you are talking about solar cells, remember the cost of the 
> support structures.  I have seen 100 nm films and let me assure you that 

You'll notice that houses are typically built to withstand most weather,
hail included. It is of course rather expensive to retrofit houses (starting
with north-south alignment, for instance, difficult to fix after the fact),
but buildings which have designed for energy efficiency and integral power
generation do need to be that much more expensive. Consider that most
current PV panels are waranteed for 25-30 years, that's a reasonably good
life time for a building facade without renovation.

> one hail storm would be the end of them.
> You also have the problem of collecting the current from solar 
> cells.  That's something I have been concerned with recently.  There are 

Um, collecting the power is a solved problem. Off-the shelf power
electronics for some 3-5 k$ will generate your AC phase-synced to 
the rest.

> also serious difficulties with storage.

Conventional power plants have a large thermal inertia, which along
with nocturnal demand lull is the reason there's a major overcapacity
during nighttime. The demand peak is during day, so if you dump things
into the grid you would only need very marginal nocturnal capacities
without requiring storage (which is not a huge problem, whether central
(reverse hydro, air-pressure cavities) or decentral (electrochemical
energy sources, e.g. such as a water electrolyser built into a pressure
tank along with a hydrogen/oxygen fuel cell which dumps direcly into
the electrolyser -- low efficiency maybe, but if PV is an order of
magntude cheaper than solar efficiency for a storage cycle is not 
that important). 
> Now, much of this goes away with nanotechnology, but if you are talking 
> near term it's a hard problem.

Sufficiently near-term about everything is a hard problem. Redesigning
infrastructure towards sustainability is a major effort, and takes time
and lots of resources.

Eugen* Leitl <a href="http://leitl.org">leitl</a> http://leitl.org
ICBM: 48.07100, 11.36820            http://www.ativel.com
8B29F6BE: 099D 78BA 2FD3 B014 B08A  7779 75B0 2443 8B29 F6BE
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