 He left UD in 1993, to dedicate his time to AstroPower Inc. which he founded in the early 1980s.He returned to UD in 2003 as the Executive Director of the Solar Power Program, Research Professor at the Department of Electrical Engineering and Computer Engineering and Senior Policy Fellow at the Center of Energy and Environmental Policy.Barnett joined the UNSW School of Photovoltaic and Renewable Energy Engineering in 2011.