Heat loss of a surface greenhouse won't be trivial, but it's only
about 30 kW/hectare even if the greenhouse is a perfect emitter.

Really? Is the following paper way off?

http://www.marshome.org/files2/Hublitz1.pdf

Fig. 7 shows upwards of 80kW for a 90 m^2 area, just in heat loss at
night. A hectare would be over 100x that much.

Note that the heat-flow profile is based on the sun being "at zenith"
-- i.e., high summer on Mars.

Did the authors somehow miss a couple orders of magnitude? Or am I
reading it wrong? I don't think this is a problem you can solve with
some special coating on your greenhouse shell.

-michael turner

On Jun 27, 11:11 pm, (Steve Willner) wrote:
In article .
com,
Michael Turner writes:

To repeat: greenhouses on the Martian surface will get exactly one
benefit from being on the surface: direct daytime pass-through of
sunlight at frequencies useful for photosynthesis. That's IT.

That seems to be quite a significant advantage, not a minor one. How
do you propose to illuminate your greenhouses if not by direct
sunlight? You need either something like 10 MW/hectare if you do it
with efficient electric lighting or a collector on the surface at
least as big in area as your greenhouse plus at least a square meter
of light pipe per hectare if you do it that way.

Heat loss of a surface greenhouse won't be trivial, but it's only
about 30 kW/hectare even if the greenhouse is a perfect emitter.
Probably a factor of 10 improvement is possible by using low-e
coatings, depending on how much trouble it is to keep dust off them.

--
Steve Willner Phone 617-495-7123 swill...@
cfa.harvard.edu
Cambridge, MA 02138 USA