THE largest university in Oregon is camouflaged, its many parts spread among the tight urban canyons of downtown Portland. But one building at Portland State University stands out. It has a roof of grass, plants and gravel, like a slice of the high desert on the wet side of Oregon. It is 10 stories high, and inside, all the mechanical organs work with so little waste – pumping water, air and electricity to the 400 residents of the dormitory and, on lower floors, to classrooms – that it would impress even the thrifty New Englanders who founded Portland.