Using a single junction PIN (p-type, intrinsic, n-type) diode, made of silicon, and doped with boron and phosphorus, high energy protons have been converted to electricity, through ionization from electronic stopping in the silicon, at an efficiency of 0.2%. A simulation of 3.02 MeV D-D protons has been performed, using a 3 MeV linear accelerator. Proton fluxes of ~3 × 1010 protonscm-2×s-1 were incident on a PIN diode with 0.7 cm2 of surface area facing the incident protons. Losses in efficiency as a function of proton fluence are compared with dpa (displacements per atom) rates calculated using the Monte Carlo ion transport code TRIM (Transport and Ranges of Ions in Matter).