New York Times: Solar power, the holy grail of renewable energy, has always faced the problem of how to store the energy captured from the sun’s rays so that demand for electricity can be met at night or whenever the sun is not shining. The difficulty is that electricity is hard to store. Batteries are not up to efficiently storing energy on a large scale. A different approach being tried by the solar power industry could eliminate the problem. The idea is to capture the sun’s heat. Heat, …