Loans at very low rates from state-owned banks in Beijing, cheap or free land from local and provincial governments across China, huge economies of scale and other cost advantages have transformed China from a minor player in the solar power industry just a few years ago into the main producer of an increasingly competitive source of electricity. “The top-tier Chinese firms are kind of the benchmark now,” said Shayle Kann, a managing director of solar power studies at GTM Research, a renewable energy market analysis firm based in Boston. Pricing of solar equipment is determined by the Chinese industry, he said, “and everyone else prices at a premium or discount to them.” Besides Solyndra, the other two American manufacturers that filed for bankruptcy in August were Evergreen Solar, of Massachusetts, and SpectraWatt, a New York company. Another company, BP Solar, halted manufacturing at its complex in Frederick, Md., last spring. Those bankruptcies and closings represent almost one-fifth of the solar panel manufacturing capacity in the United States, according to GTM Research.