Design, development and control of a self-tracking photovoltaic roof for a road vehicle

In last years, increasing fleet electrification, improvement in solar panel efficiency and reduction in their costs are concurring toward an increasing attention to the integration of photovoltaic in road vehicles. As in fixed plants, the adoption of solar tracking systems would allow to enhance the solar contribution. But a mobile solar systems for a car must have specific features, due to space constraints and to specific exigencies of a mobile application such as instabilities, energy and aerodynamic losses. Due to these reasons, they should operate only in parking mode. A kinematic model of mobile solar roof, as a parallel robot, has been developed and used to optimize the roof geometry; the benefits of a mobile roof, in terms of solar energy gain at different latitudes and months, have been assessed. A second prototype of solar tracking roof with two degrees of freedom has been then realized, to overcome some mechanical problems. In order to detect the relative position of the sun and to achieve the best roof orientation, a model based control strategy has been developed, using sky images detected by a small camera. The control system has been successfully validated over experimental data. In order to assess the economic feasibility of the project, a preliminary study on payback value has been performed. The comparison of a fixed horizontal roof and a solar tracking roof on a hybrid vehicle has shown that a significant reduction in payback occurs with the adoption of a mobile solar roof. Copyright © 2013 SAE International.