Reuters: Squeezed by aggressive Chinese and U.S. rivals globally, Japanese makers of solar photovoltaic (PV) systems need to boost their technological edge if they are to stay ahead in their near-$1 billion home market. Asia’s biggest economy is the world’s third-largest market for solar energy, and state support for the sector has attracted investments from among the region’s biggest solar firms. China’s Suntech Power is the fourth-largest supplier of solar PV systems in Japan — a …