 Six-phase heating (see Technology below) was created and patented for the US Department of Energy (DOE) in the 1980s for use on DOE sites as well as commercial applications.Electrical resistance heating is used by the environmental restoration industry for remediation of contaminated soil and groundwater.ERH consists of constructing electrodes in the ground, applying alternating current (AC) electricity to the electrodes and heating the subsurface to temperatures that promote the evaporation of contaminants.