I Hope This isn't a Scam

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This Nigerian College Student Built a Wind- And Solar-Powered Car From Scraps

I’ve run numbers for a solar-powered car before, when someone had proposed just popping solar cells on a car and thinking that would be viable. It won’t work. It’s not really close, so even with a head start of charging the battery up, I have to wonder what you’re going to get.

Gasoline has an energy density of around 120 MJ/gallon. Let’s convert this into units used in electrical systems: 1 kW-hour is 3.6 MJ, so a gallon of gas is a little over 30 kWh of energy. Electrical systems are much more efficient than internal combustion, so let’s assume we only need 10 kWh of electricity to do the work of a gallon of gasoline (which also might require things like regenerative braking). Comparing to a 30 mpg gasoline engine, this is 3 miles/kWh, which is about what commercial electric cars are getting.

According to maps I found, solar insolation in the US is highest in the southwest, peaking above 5 kWh/m^2/day, and I think that assumes your panels track the sun to keep it perpendicular to the panel. The solar panel on the car looks to be about 2 square meters, so we can get around 10 kWh with a full day’s charge — we can replace about a gallon of gas. Nigeria’s insolation is higher, so let’s multiply this insolation by 2, but the claim is that this happens in 4-5 hours, so maybe that’s a wash. And the panel doesn’t track the sun, so this is probably generous.

Can you get around town in something like that? Sure. You can go 30 miles in a day on a charge, plus whatever charging you get as you’re out and about. But then you’ll have a depleted battery, and wouldn’t be able to do this every day since you can’t charge it at night. Unless you’re going under 10 mph and it’s always sunny, this can never be a “charge-as-you-go” system without an order-of-magnitude improvement somewhere.

There’s also this, which sets off the skeptic alarm in a much stronger fashion:

Not only did Oyeyiola install a giant solar panel on top of the Beetle; he also inserted a wind turbine under the hood. As Preston explains, that allows air to flow into the grill while the car is moving, subsequently turning the turbine’s rotors and charging the battery at the back of the car. Oyeyiola also built a strong suspension system to deal with the weight of the battery itself.

Unless this is just a really poor description of something else, it sounds an awful lot like a perpetual motion machine — using the wind generated by your motion to charge the battery. Realistically, such a device should drain the battery faster, because it can’t be 100% efficient.

3 thoughts on “I Hope This isn't a Scam”

  1. It’s rather counterintuitive that a solar car won’t work, but a solar airplane has worked. Normally, you would think that surface transport is much more energy efficient than flight. I suppose the plane can have huge solar panels, but a practical car can’t.

    http://www.solarimpulse.com/

  2. “As Preston explains, that allows air to flow into the grill while the car is moving, subsequently turning the turbine’s rotors and charging the battery at the back of the car”

    From my memory of old vw bugs – the engine is at the back and there are no substantial grills at the front.

    Also – if this is a car from the 70s, which it looks like, it is seriously heavy and those tyres dont exactly look ideal for low rolling resistance.

    I think it looks like Scam.

    I think for non-city driving in somewhere as sun-drenched as Lagos then there is a possibility of a viable solar car. It needs to be built more along the lines of a double seater recliner bicycle, super-light, thin hard tyres and very low wind resistance. .

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