The parking dilemma for solar-powered vehicles.

Parking a solar electric car in the sunshine will help charge its battery, increasing its driving range. On the other hand, it will also raise its indoor temperature, leading to the need to switch on the air conditioning to make it comfortable when driving, increasing the driving load and reducing the vehicle range. Thus, one may wonder if the solar-extended range is somehow reduced or even eliminated by the increasing demand due to air conditioning. To address this "parking dilemma", we have characterized the thermal properties of a passenger car for typical summer conditions in a moderate latitude temperate location (Lisbon, Portugal) to be able to explore the vehicle's thermal performance when parked in the sun. Results show that effective solar charging depends critically on the onboard installed PV capacity. For the specific conditions tested and a 0.5 kWp PV system, the critical parking time below which the parking session does not contribute to net charging is around 2 h. For systems with more than 0.8 kWp installed capacity, parking in the sun always provides a positive impact on the vehicle's driving range.