The turbo-expander is the most crucial and expensive component in Organic Rankine Cycle (ORC) power generation systems. The turbine engineering, design and research development process for ORC system is costly, time-consuming, and difficult for new-entrants in the ORC field. This paper investigates re-design and retrofit of an off-the-shelf turbocharger for a 1 kW ORC system. The expander requirements were determined for the 1 kW bottoming cycles for Capstone Gas Turbine from the system design. A radial turbine was selected and an offshelves turbocharger from a small petrol-driven vehicle was acquired. The turbocharger was simulated to study the offdesign performance in the ORC system. The turbocharger was evaluated by expansion of compressed air in room temperature to assess the leakage of working fluid and lubrication. A preliminary design was developed to deal with leakage and lubrication issues. The conceptual design of ORC turbine includes the casing design and selection of auxiliary components such as bearings, seals and lubrication system.