The term solar farm can have multiple meanings. One is the number of farms that have been paved over with solar panels. Another is the number of farms with renewable-energy-producing systems, which can obviously overlap. When it comes to solar-powered farms, the number is 591 -- more than double the 204 recorded in 2007, according to the Census of Agriculture. That equates to six percent of NJ farms – compared to less than 2 percent for U.S. farms.