Mitsubishi Electric, Toshiba and Showa Shell yesterday each unveiled plans to boost their solar panel production.Shigeaki Kameda, president of Showa Shell's solar subsidiary, said the company intended to become the world's largest producer of thin-film photovoltaic panels, with the business eventually rivalling its Y3,000bn ($33.6bn) oil-refining and petrol operations in scale.Mitsubishi said it hoped to produce 600 megawatts' worth of photovoltaic cells annually by the financial year to March 2012, up from 220MW.Toshiba, which makes residential solar-power systems, said it was aiming to take 10 per cent of the Japanese domestic market by the year to March 2013.