What type of application are you interested in when you say "large project"?
If you are describing a single large ASHRAE 90.1 model that may take
over 15 minutes to run, I often simply use the "group of input files"
tab to execute my approx. 8 models (i.e. 4 baseline and 4 proposed with
different oversizing in the HVAC) using my 4 processor cores
simultaneously, so it takes 30 minutes instead of 2 hours. And if you do
this often, it might make sense to buy a new dedicated multicore core
machine that you can use to execute jobs, and access the files over a
network. I would recommend this approach just because it requires no
extra software or setup.
If however you are doing global optimization or parametric studies with
HUNDREDS of executions, then you will likely need the approach that Dr.
Crawley or Dr. Li have mentioned, and invest into grid/cluster/cloud
computing. Fortunately, this is a problem that has been solved many
times over in the IT world and there are many approaches and platforms
available, the problem really is choosing one.
(Aside: This is all a topic near and dear to my PhD and professional
objectives, so if anyone wants to submit a paper or research project let
me know!)