ISLE AU HAUT — The news reports were glowing: A planned microgrid on Isle au Haut could “hold the answer to the future of electricity,” wrote ensia, an environmental media outlet based in Minnesota. It could one day “be a model for the entire nation,” according to another national broadcast. The project, depicted in 2020 as being on the verge of installation, would include solar panels to generate energy and supercapacitors and heat pumps to store it. That hardware would be accompanied by state-of-the art software that would decide when it was most cost-effective and efficient to store and release...