Let's watch this test case

> you're holding out for some future possibility of these devices
> reaching fruitition while at the same time using the rationale of
> immature technology to condemn SPS.

I'm arguing a few things in this debate (as it has evolved) only some of
which depend substantially on future technology. To repeat them (as
every time I rewrite them they seem to get more coherent as a
presentation :-)

1. That one needs to at the very least make a judgment call on whether
R&D on PV, fuel cells, MEMS stirling engines, etc. will produce systems
that are cheaper per W in capital cost and per kWh in operation than SPS
+ Grid in twenty years time in order to decide whether to invest in SPS
starting now. If R&D on such local systems will actually produce the
kinds of breakthroughs in cost or efficiency companies are *already*
announcing in PV and MEMS heat-to-electricity-conversion devices, then
SPS will just be an obsolete non-go as an investment when coupled with a
hydrogen infrastructure for smoothing over times when the sun doesn't
shine (and a Hydrogen infrastructure would pretty much happen even with
SPS, since Hydrogen use for local backup storage given grid failures or
carbon sequestration for liquid fuel production for automobiles makes
sense even with SPS power).

2. That passive solar and insulation and energy efficiency make economic
sense right now, and wind and PV also make easy economic sense in
limited applications right now (e.g. solar power to handle air
conditioning loads in the south), and that pursuing these strategies
drives Amory Lovin's "soft energy path" as an incremental set of
relatively small investments. Further, that PV+Wind+Tidal+biomass+etc.
with Hydrogen or Hydrogen derived liquid fuels as energy carriers would
probably make economic sense for most everyone right now (or near
certainly in the next five years) [and certainly for 80% of humanity
overall) if tax preferences and external costs were taken into account
related to pollution and security which would mean oil would be priced
more like at $250+ / barrel instead of $25 / barrel as it is now
(although admittedly PV production techniques needs to be rethought to
reduce pollution, although I think that would happen with a move to
greater production quantity -- though admittedly I am doing some
handwaving on this point :-). Thus there is an existing long term
solution already possible (with the removal of tax and other artificial
legal preferences for fossil fuels and centralized nukes) that SPS needs
to do better than -- and this long term solution can be reached
incrementally at low risk. We can argue the issues with this Earthly
solution (nothing is perfect), but it is IMHO an acceptable one and the
one SPS needs to do much better than.

3. That even is SPS succeeds economically and technically with whatever
subsidies and tax preferences and investments, that SPS will still fail
on environmental grounds of requiring the expansion and upgrading of the
grid by a factor of three or so (as everyone switches to electric heat
and produces hydrogen locally for automobile fuel). SPS will also fail
on social and political grounds of placing national security in the
hands of a small technical elite who must be relied on second by second
to keep the country running. SPS will also fail on security grounds of
being a more obvious system with only a few main installations which are
more vulnerable to attack than Earthly alternatives (and further,
vulnerable an attack which doesn't kill many people directly, yet leaves
a nation completely dependent on energy imports, allowing a bloodless
takeover) and thus requires the militarization of space to defend SPS,
putting any habitat occupants more at risk for becoming embroiled in
longstanding and self-defeating Earthly feuds transferred to space and
yet based on a failure of the imagination and inability to let go of
scarcity and low-productivity based economic assumptions.

4. That there are alternative approaches to producing space habitats
that rely on creating a self-replicating seed and launching it with
expensive launch systems (not CATS). Thus SPS is not needed to create
space habitats -- although admittedly such space habitats might use SPS
type technology either to produce their own power or to beam power to
Earth for launch vehicles used by people leaving Earth to live in Habitats.

I have not been convinced by your rebuttals on those points. Still, it
has been for me at least a useful and informative debate. I think, for
example, your point that using the grid won't scale for energy backup if
most people move to PV or wind is a good one, and needs to be factored
into any such development plans (thus pushing for more emphasis on local
hydrogen etc. storage to end reliance on the grid entirely). I think we
are reaching the point where we can just agree to disagree, and each
pursue our different approaches, and see what happens.

--Paul Fernhout