The past few months have ushered in enormous changes for the energy industry, from the resurgence of the Organization of the Petroleum Exporting Countries, or OPEC, to a sudden slowdown in U.S. shale-oil production. The politics of energy have shifted, too, upending fast-growing industries such as solar power. Nonetheless, some investors see opportunities, given the growing global interest in energy security and the rise of electricity-guzzling technologies such as artificial intelligence.