Which solar projects? Based on this https://www.nrel.gov/docs/fy13osti/56290.pdf (2013) report the the smallest number I find is 2 acres/GWh/year. That's direct land use (ie. only the landuse directly below the panels) for "2-axis tracked CPV" plants (granted, an average). Total landuse is 2.8 for the same type of plants.

The Wolf Creek station come in at 1.02 acres/GWh/year (based on 90% capacity factor)