----- Original Message -----
From: "Alex Caliostro"
would this system also work at night ....?
http://www.energylan.sandia.gov/sunlab/PDFs/solar_dish.pdf
Alex,
It's not that simple, unfortunately.
But these Solar-Stirling arrays can definitely be a part of an
expanded and reengineered system ... leading to a more affordable
and ecologically sound hydrogen (or battery) economy... and NOW
(at least within the short term).
The interesting thing is that now we seem to have two very
different but extremely promising ways to increase the Solar
Stirling efficiency - simply through the synergy of on-site
combination - leading to much a much higher desirability of the
Sandia-type Solar Stirling (SSS) than as a stand-alone system.
By that I mean, starting with the base SSS you would need to
"site" these is a high desert - of course New Mexico is perfect,
as is much of the southwest USA. Second you need to provide a
different "head" (or operative unit) to replace the Stirling
pistons at night (this swap can be done automatically). This
night-time head would be a simple water-based multi-tube heat
exchanger (water stored in underground cisterns is cooled from say
80F to 40F.). Third, you need to modify the SSS head to
accommodated active-cold-water-cooling (using the chilled water
from the night before). This will bump the Carnot efficiency of
the Stirling way up over air cooling. Fourth you need to add a
whole secondary array of improved-zinc-refining dishes (improved
with the reverse-SOFC if that is feasible) which use the
electrical power from SSS array to make large amounts of zinc from
zinc oxide (which is recycled).
The zinc is available for use in either zinc-air batteries or for
onboard hydrogen generation for transportation needs - replacing
fossil fuels. I don't know which route is more efficient,
batteries or hydrogen fuel-cells, but the zinc-air battery may end
up being a better overall option for transportation because of
simplicity.
The batteries could be put right into a Prius for instance.
Instead of a home charge you would do a zinc-exchange at the
new-age filling station (or both). Solar zinc batteries are likely
to be much cheaper to recharge via zinc exchange, than via grid
electricity. My preliminary calculations show that solar-zinc
might be the equivalent of 2 cents per kwh equivalent (if the SSS
gives 6 cent equivalent electricity- excluding profit and
transportation costs).
So here we have a kind of natural synergism emerging !
Best of all, it is truly no-carbon instead of carbon neutral - the
actual carbon-neutrality of using biomass is a bit questionable
anyway.
This is an area of great promise. The combination system is likely
to be much more efficient at capturing the maximum possible energy
of solar radiation than is wind, for instance - since wind cannot
be reliably coordinated with solar zinc refining - nor to grid
requirements of power demand. Wind can be fickle but in parts of
the southwest, the sun shines brightly 350 days a year and nights
are relatively cool, even in the summer.
Jones
