You may have seen a few stories about the Karma Revero's solar roof. For those that follow cars, the Revero is the re-born Fisker Karma, a hybrid gas and electric vehicle.
Fisker went bankrupt and was bought by a Chinese automotive components company. Fisker was renamed to Karma and the car was renamed from the Karma to the Revero.
Karma's website has this text on their website about the solar roof:
Lots of sites have written stories about the solar roof idea, copying the information from Karma without doing any kind of analysis.
Solar panels can be helpful when used on cars. Toyota offered, and may still offer, a solar panel option for the Prius that would use solar power to run a fan to vent the car when the interior was hot. This would reduce the inside temperature and help reduce the need for air conditioning.
Karma is claiming their solar roof can go beyond just powering a fan, and instead power the car. It may be factually true that the solar roof can power the car but it is misleading to suggest that they can do so in a way that you would notice on a daily basis.
Wikipedia lists the Karma (and presumably the Revero's) energy consumption at 65 kWh / 100 miles, or 650 Wh/mile. For comparison I get between 250-310 Wh/mile in my Model S on the highway in the summer with AC, depending on speed and elevation change.
Wikipedia reports that the Karma's solar roof can generate approximately 500 Wh per day.
Let's assume that the Revero has had some improvements and has increased its solar output by 50% to 750 Wh per day and the efficiency of the electric drivetrain has improved and its consumption was reduced to 400 Wh/mile. Together this means you can travel about two miles on the energy from a full day's solar roof generation.
750 Wh / 400 Wh/mile = 1.875 miles
This is an optimistic number and its very likely that actual generated range will be lower than this.
Two miles isn't a lot of driving range and it isn't surprising that other car manufacturers, even those with electric drivetrains, haven't been putting solar panels on their cars. In the summer it might save more energy to park in the shade.
The Revero's solar roof as it's currently presented is a gimmick that Karma is using to attract interest. Looking at the contribution of the solar roof over the life of the car might yield a different result. Even a small amount of energy per day could add up to a substantial amount over the life of the car, although that isn't the only factor. Will it generate enough energy to offset the extra energy used to haul around the solar roof and its electronics? Will it generate enough energy to offset the cost of the panels and electronics? I'd like to see Karma make their case by providing more information and clarify the real-world utility of their solar roof.
Update: Jalopnik writes The Claim That The Karma Revero's Solar Roof Will 'Power The Car' Is Such Bullshit. I agree.
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| By Fisker at speed in the fog.jpg: Fisker Auto derivative work: Mariordo (Mario Roberto Durán Ortiz) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons |
Fisker went bankrupt and was bought by a Chinese automotive components company. Fisker was renamed to Karma and the car was renamed from the Karma to the Revero.
Karma's website has this text on their website about the solar roof:
"Our solar roof will create enough energy to power the car. No other vehicle sold in the U.S. has ever offered this capability. Our owners consider our solar roof an important element in our brand identity, and we listened."
Lots of sites have written stories about the solar roof idea, copying the information from Karma without doing any kind of analysis.
Solar panels can be helpful when used on cars. Toyota offered, and may still offer, a solar panel option for the Prius that would use solar power to run a fan to vent the car when the interior was hot. This would reduce the inside temperature and help reduce the need for air conditioning.
Karma is claiming their solar roof can go beyond just powering a fan, and instead power the car. It may be factually true that the solar roof can power the car but it is misleading to suggest that they can do so in a way that you would notice on a daily basis.
Wikipedia lists the Karma (and presumably the Revero's) energy consumption at 65 kWh / 100 miles, or 650 Wh/mile. For comparison I get between 250-310 Wh/mile in my Model S on the highway in the summer with AC, depending on speed and elevation change.
Wikipedia reports that the Karma's solar roof can generate approximately 500 Wh per day.
Let's assume that the Revero has had some improvements and has increased its solar output by 50% to 750 Wh per day and the efficiency of the electric drivetrain has improved and its consumption was reduced to 400 Wh/mile. Together this means you can travel about two miles on the energy from a full day's solar roof generation.
750 Wh / 400 Wh/mile = 1.875 miles
This is an optimistic number and its very likely that actual generated range will be lower than this.
Two miles isn't a lot of driving range and it isn't surprising that other car manufacturers, even those with electric drivetrains, haven't been putting solar panels on their cars. In the summer it might save more energy to park in the shade.
The Revero's solar roof as it's currently presented is a gimmick that Karma is using to attract interest. Looking at the contribution of the solar roof over the life of the car might yield a different result. Even a small amount of energy per day could add up to a substantial amount over the life of the car, although that isn't the only factor. Will it generate enough energy to offset the extra energy used to haul around the solar roof and its electronics? Will it generate enough energy to offset the cost of the panels and electronics? I'd like to see Karma make their case by providing more information and clarify the real-world utility of their solar roof.
Update: Jalopnik writes The Claim That The Karma Revero's Solar Roof Will 'Power The Car' Is Such Bullshit. I agree.
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