Is it possible to set up a heliostatic system that melts snow from a
courtyard _directly_, ie, through direct sunlight reflection?  (Not
through energy accumulation and powering another snow-melting system) 
The courtyard, specifically, is 18,000 sq.ft., lined on all four sides
by short- and medium-height buildings, and located in Ithaca,
NY.  The location gets between 100 and 200 hours of snowfall a year. 
If this system is possible, what is the most practically feasible
setup?  Square footage of needed reflectors, etc?  Location of
mirrors? etc.  I realize many
factors affect the answer, but I'm trying to get a general
understanding of what's possible.  The answer will impact an
architectural project for Cornell University - one in which we're
trying not to embed the courtyard with heated pipes or rods.

Interesting.

You want to use solar reflectors to melt snow in a 185 ft square quadrant.

The trouble with snow is that it reflects light, so pure reflection is pointless.

What you really want to do is to heat up certain areas/artifacts so
that there is a cross flow of warm air.

Since warm air rises, my best guess so far, would be to blast a
pool/fountain in the centre to get an updraft of H2O, and cook hot
objects in the corners to provide hot air that has to be sucked in
laterally.

The downside is that you'll get a cold downdraught against the face of
the buildings.

Perhaps reversing system might be optimal
- getting a downdraught in the centre - but heating it - less than the corners.

To test it out you need strips of corrugated iron, matt black paint
and some aluminium foil - for a trial the reflectors could be at near
ground level.

Darn thing is that it might be aesthetically interesting.

Snow melts best under three main conditions.

Firstly, the amount of sunlight fall on the area you want to melt. 
That is why the houses on the north side of a street are usually clear
of snow long before the houses on the south side.

Secondly, the amount of sunlight that is absorbed.  White snow
reflects most of the light falling on it.  A way round this is to have
areas that are dark, such as clearing parts of the area down to a
black asphelt base.  These areas of cleared snow will enlarge as they
heat up.

Thirdly, you can add pellets to melt the snow.

The combination of increasing sunlight, reducing reflectivity and
melting pellets is probably the best you can do.

Excuse me for finding a bit humorous that a solution is being sought
here for a building for the school of architecture at a major
university.     http://www.architecture.cornell.edu/html/text_only.html

Will reflecting sunlight really increase the heat enough to melt the snow?
I doubt it.  A good deal of light will be reflected, UV light too,
(great place for a winter tan) but how much radiant heat will be
reflected over the distance of 100 to 200 ft?
But even if an expert says it can,
the 18,000 sq ft courtyard  - that's 180x100 or 135x135 say,  is going
to need an awful lot of unsightly mirrors to do the job, which will
not enhance the appearance of the building.

Does the whole court have to be cleared of snow?
Wouldn't just the paths be enough?  People aren't going to be standing
around in an Ithican winter.
Let the rest of the snow melt when it thaws  (I hope adequate drainage
has been planned.)
If in northern Europe they can heat soccer fields, the court shouldn't
be a real problem.
Does the school or U. want an ecological solution?
What sources of wasted heat are available  - for the paths, at least?

I am trying to ask leading questions because I don't think the mirrors
are the answer, but it could be a good project for some kind of
course:  Model, testing the heat reflection of mirrors at a distance
of maybe 100 ft (how much gets dissipated??)  What will the average
snowy weather temperature in the court be, and will the heat
reflective raise it above freezing?

Good luck!