We do get all excited by fancy solar systems with pumps and panels, but the hardest systems to do well are the passive ones, which require good architectural design and careful siting, rather than throwing money at hardware.
The new Blue Ridge Parkway Destination Center, designed by Lord, Aeck & Sargent, was designed very carefully indeed, using techniques from the aerospace and defence industries. They partnered with Pennsylvania State University's Applied Research Laboratory (ARL) to construct a computational fluid dynamics (CFD) model to study the air flow within the building.
They used this information to design thirteen Trombe walls (which use the sun to heat a small air space between a glass wall and a heavy-mass wall such as concrete. The trapped heat is then transferred into the building, either indirectly through the concrete or, as is the case with the Destination Center, directly through vents.) According to the press release:
"Traditionally, CFD has been used in the aerospace and defense industries, but more recently it's been used in high-tech architectural applications. We feel that its potential for modeling passive buildings is largely untapped," said Vikram Sami, LEED AP, a member of Lord, Aeck & Sargent's design team who led the collaboration with the ARL. "The Destination Center's Trombe walls move air heated by the sun into the facility's exhibit hall, which is the main focus of the building. Since the Trombe walls face due south, they're fully exposed to the sun in the winter when maximum heating is desired. The walls are shaded in the summer by a roof overhang to prevent overheating of the building."
It also has a radiant floor, heat recovery ventilators, storm water management and is topped off with a 10,000 square foot green roof planted with native, drought tolerant plants. ::Lord, Aeck & Sargent