Concentrating sunlight onto photovoltaic cells means you need a lot fewer cells. This approach combines clever use of optics and mechanics, with cheap, ubiquitous materials (plastic sheeting, air, a tiny amount of aluminum to coat the reflecting surface). Here's the basic environmental impact (from the notes in the PDF presentation, slide 4):
Our approach is to suspend concentrators on support and control cables stretched between poles. The ground under the concentrators is shaded only by about 10% and remains free for other uses like farming or ranching. Suspending the concentrators also preserves habitat. It is also inexpensive: telephone companies, ranchers, and farmers have already figured out how to set posts cheaply across vast spaces.Cool indeed.