Analysis of energy capture by vehicle solar roofs in conjunction with workplace plug-in charging

• Vehicle-roof-installed solar array operation is analyzed for commuter travel.
• Battery capacity saturation may limit effective solar energy capture by the system.
• Solar charging can’t keep pace with faster workplace level 2 plug-in charging.
• Optimizing energy capture will require smarter controls in future vehicle designs.

Solar cells integrated into electric vehicles have long been a mainstay of collegiate racing competitions, but the small amount of roof area has prevented vehicle-solar installations from having a dramatic market in more conventional vehicles. Still, vehicle solar roof installations have a great potential because they can almost always be exposed to the sunlight as they are frequently parked for hours in parking lots at work, shopping, or other open spaces. At the same time hybrid and electric vehicle drivers are typically concerned about their all-electric driving range and do whatever they can to plug-in and “top off” the battery whenever possible. Unfortunately this behavior mode of topping off the battery can establish situations where the vehicle’s solar collection is neutralized because the battery is already full. This paper analyzes this conflict for different charging and driving scenarios with an emphasis on commuters who would have access to workplace charging. It is found that regular commuters who make use of level-2 workplace charging could experience a loss of more than 75% of the potentially available photovoltaic output from roof-installed solar on their vehicles. This surprise finding is discussed from the perspective of plug usage habits and “range anxiety”.

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