Swedish home-furnishings giant IKEA officially powered up its Brooklyn, N.Y., store’s rooftop solar system this spring after several delays, including a mid-construction switch of its main contractor. Photo: By Esther D'amico Store-top installation enables four different types of photovoltaic panels to be evaluated. The store is one of four worldwide participating in a $11.7-million pilot program IKEA established in 2009 with Loughborough University, Leicestershire, U.K., and the now-defunct contractor Perpetual Energy Ltd., Knutsford, U.K., to monitor and evaluate performance of photovoltaic systems. While the systems at each of the four sites are operational, their monitoring capabilities are as yet limited

The value of the U.S. solar power market soared last year as several states, including New Jersey, significantly boosted installed capacity, according to a recent study by the Solar Energy Industries Association and market research firm GTM Research. Federal, state and, in some cases, local incentive programs and funding initiatives helped raise total year-over-year market value 67%, to $6 billion, the study shows. Market news was healthy nationwide as 16 states each installed more than 10 MW of photovoltaics, up from four in 2007. New Jersey, however, already has surpassed that amount and ranks second nationwide, trailing only California in