If a third of the new vehicles sold in the United States in 2004 were integrated with 200 watts of photovoltaics each, the total power capacity of these vehicles would be comparable to that of a large power plant.
To estimate the potential energy output from a VIPV system, we measured the dimensions of several vehicle types. Though more technical analysis would be needed to determine the
appropriate PV technology to deploy in VIPV applications, we assume for this exercise that flexible, thin-film PV would be the best fit, even given its low conversion efficiencies compared to crystalline silicon solar cells. As the table on the facing page suggests, the amount of PV that could be integrated onto a vehicle varies from 222 watts to 366 watts, depending on the vehicle style.
The energy output of a VIPV system will depend on many factors, from the solar resource in the region to personal parking habits. Ideally, a VIPV hybrid car would be parked with good southern exposure and minimal shading, like on the top-level of a parking garage. Assuming a vehicle with 250 watts of PV
capacity and in a location with an average of four sun hours per day, the annual energy output of the VIPV system would be approximately 300 kWh. This extra energy could be used for charging the vehicle's battery pack or operating a ventilation fan to reduce the energy requirements when the driver enters the vehicle for the next trip. In states where utility
net metering rules exist, plug-in equipped hybrids integrated with PV could feed electricity to the grid when the vehicle's batteries were fully charged.
The chart above illustrates the number of solar-powered miles that a vehicle with 250 watts could achieve given
PV system capacity factor (a percentage of annual energy output relative to the system's rated capacity output) ranging from 5 percent to 30 percent. The graph also illustrates the cost per solar mile given an assumed incremental cost of $2,000 for a
250 watt VIPV system. As the chart suggests, lower PV capacity factors (e.g., a less favorable solar resource and/or more frequent shaded parking) deliver lower solar miles for the life of the vehicle at higher cost per mile.
When operated at low speed on battery power only, the Toyota Prius uses about 200
watt hours per mile. Using this data for illustrative purposes, a 250
watt VIP V system could deliver approximately 1,500 solar-powered miles annually. Though that might be just 10 percent of the total miles this vehicle travels annually, the solar contribution is a positive step in helping to increase the vehicle's overall efficiency, similar to the use of regenerative braking in hybrids. The added cost of the solar PV would be in the range of $1,500 to $2,500. Over the life of the vehicle, this investment would translate to approximately $0.12 per mile for each of the 22,500
solar powered miles provided by the VIPV system, roughly equivalent to the cost of fueling a
30 mpg gasoline powered vehicle at $3 per gallon.
Vehicle-Integrated PV Brings Efficiency Gains
Many types of PV technology are available commercially. One trend is for the use of
building integrated PV; or BIPV. PV is being integrated into a number of building products to serve BIPV applications. For example, one vendor offers residential roofing products integrated with its thin-film amorphous silicon
technology. Many other companies offer BIPV products ranging from commercial and industrial roofing systems to semi-transparent
building facade materials integrated with pv. As with buildings, PV technology could be integrated onto the body panels of a vehicle. The energy output of a VIPV system would depend on the amount of
vehicle surface area exposed to sunlight and the efficiency of the PV technology appropriate for the application.
As gas prices rise and interest grows in reducing U.S. reliance on foreign oil, plug-in hybrid electric vehicles have emerged as a promising solution to dramatically increase the fuel economy of the nation's
light vehicle fleet. To learn more about plugin hybrid electric vehicles, visit
Electric Vehicle Concepts ,com
Interest in Solar-Integrated Cars Is Growing
Early indications suggest that VIPV may be catching on. A few pioneers are integrating hybrids with PV.
E-V Concepts, retrofitted a Toyota Prius with 270 watts of PV capacity and additional battery storage.
The conversion has increased the fuel economy of the vehicle by 10 percent. Even the big automobile manufacturers are eyeing the VIPV opportunity. Ford Motor Co. unveiled the Reflex, a
diesel electric concept vehicle with VIPV at the 2006 North American International Auto Show. Ford's corporate partner Mazda also recently unveiled a hybrid electric concept vehicle with
roof integrated PV. Mazda introduced the Senku, which means "pioneer" in Japanese, at the 2005 Tokyo Motor Show.
These examples demonstrate the VIPV opportunity, but they don't capture the full potential of VIPV. In the future,
ultra light vehicles with advanced thin-film solar technology could enable solar to provide a significant portion of the energy needs for transportation. Regardless of future innovations, VIPV may offer the best promise for solar energy to offset a significant portion of our
transportation related fossil fuel demand. It also may represent a significant new market for the solar electric industry.
Learn More About Plug-In Hybrids