Reuters: Two Chinese companies on Friday announced plans to build a solar power plant in northwestern China that could one day be the largest photovoltaic solar project in the world. The news helped spur a rally in shares of solar power companies that was also underpinned by higher oil prices and a strong rise the broader market. China Technology Development Group Corp and privately held Qinghai New Energy Group will begin building a 30 megawatt solar power station in China’s Qaidam …