NOVELTY - Compensation of silicon feedstock having a dopant concentration to produce solar grade silicon, comprises calculating an initial compensating dopant based upon the dopant concentration to produce a desired resistivity; adding the initial compensating dopant to the silicon feedstock; and melting and directionally solidifying the silicon feedstock to achieve the desired resistivity over a portion(s) of an ingot produced from the silicon feedstock. The resistivity of the sample is determined by direct electrical measurement or an induction coil pickup.    USE - Method for compensation of silicon feedstock having a dopant concentration to produce solar grade silicon in the form of silicon ingot, sheet, silicon ribbon, or silicon wafer for solar cells (claimed) or photovoltaic solar cells.    ADVANTAGE - The method uses relatively low-cost silicon with low metal impurity concentration but contains a high dopant impurity concentration for solar cell substrates; and provides high efficiency solar cells.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method of compensating excessively doped silicon while in a melt, comprising adding an initial amount of compensating dopant to the excessively doped silicon while in the melt to initially compensate the excessively doped silicon in the melt to an approximate initially-compensated resistivity; sampling the initially compensated doped silicon while in the melt to measure its initially-compensated resistivity; computing a second amount of compensating dopant needed to add to the initially compensated doped silicon while in the melt to compensate the initially-compensated silicon in the melt to an approximate second-compensated resistivity; and adding the second amount of compensating dopant to the initially compensated silicon in the melt; and    (2) a silicon in the form of silicon ingot, sheet, silicon ribbon, or silicon wafer for solar cells, comprising both p and n type dopant, where difference between the p and n type dopants results in a resistivity of 0.1-10 ohm-cm.    DESCRIPTION OF DRAWING(S) - The drawing is a schematic view of sampling the melt during growth and for adding compensating dopant.