A base structure having a bearing surface defining a bearing plane and an inner portion spaced apart from the bearing surface in a direction that is substantially perpendicular to the bearing plane. Methods are also disclosed for storing electrical energy in the form of heat energy in which an installation of the invention is used, and for a method of returning electrical energy from heat energy stored by a method according to the invention. A given bias is applied to the well and the threshold voltage of the transistor is thus lowered.