A Solar Car for the Masses?
Ford’s Solar Car Isn’t Just A Toy
It’s car show season again. I’m not sure I’ll have time to take in the DC Auto Show later this month, but if I do, the entry I’ll be keenest to see won’t be the new Corvette “supercar” or the Acura TLX prototype, as much as those speak to my love of cars. Instead it’s the Ford “C-MAX Solar Energi” concept, an unlikely marriage of electric vehicle (EV) and solar photovoltaic panels (PV). The car previously debuted at this year’s Consumer Electronics Show in Las Vegas.
This isn’t the first time a carmaker has put solar panels on the roof of a car, even if we exclude competitions like the Solar Car Challenge and many other efforts to test how far or fast one-off solar vehicles designed by engineering students or enthusiasts could travel. However, I believe this is the first time an “OEM” has added solar panels to a production car for the purpose of providing a significant fraction of its motive power.
The biggest hurdle that any attempt to power a car with onboard solar panels must overcome is the low energy density of sunlight at the earth’s surface and the relatively low efficiency of current solar panels, which are much improved over past versions. A typical EV requires 0.25-0.33 kilowatt-hours (kWh) of energy to travel one mile. 1.5 square meters of solar panel on the roof of a vehicle would receive on average only about 6 kWH per day in much of the US, assuming it was stationary and never parked under a roof or tree, and much less in winter. That’s enough to travel up to 20 miles, or the equivalent of less than half a gallon of gasoline in a typical hybrid.
The clever part of Ford’s solar design is its recognition that the rate of self-charging from the car’s rooftop wouldn’t be sufficient to liberate its owner from the gas pump without help in the form of an “off-vehicle solar concentrator.” This is essentially a glass carport that focuses the sun’s rays on the car’s PV roof and, according to the write-up in MIT’s Technology Review, works with the car’s software to move the car during the course of the day to keep the roof in the brightest area. That maximizes the amount of energy stored in the car’s battery, yielding enough for the daily needs of a fair percentage of drivers.
It’s not immediately obvious that combining two of the most expensive energy technologies of today — EV and PV — represents a good strategy for making them competitive with the status quo, particularly given the likelihood of relatively stable gasoline prices for the next few years and the significant improvements being made in the fuel economy of conventional cars, for which 40 mpg highway is no longer considered remarkable. The ordinary hybrid version of the C-MAX is rated at 43 mpg combined city/highway, and the plug-in version on which the solar prototype is based is rated at 100 mpg-equivalent on electricity alone.
I have no idea what Ford would charge for the solar option, should it eventually build the car, but it’s a good bet that it would be a significant multiple of the roughly $300 cost of the solar panels. Even without the Fresnel-lens carport, integrating PV into the car’s roof in a durable manner, together with the changes to the car’s power management hardware and software, are unlikely to come cheap.
Nor is it obvious that putting solar panels on a car’s roof is the best way to provide renewable electricity for vehicles. As Technology Review notes, Tesla is pursuing high-voltage (thus rapid) recharging facilities powered by stationary solar arrays, thus removing the constraint on effective PV area. It’s even simpler for many EV owners who want to avoid “exporting” their car’s emissions to fossil-fuel power plants to sign up for 100% renewable power from their local utility.
It’s no secret that EV sales have been disappointing, initially, for various reasons. The latest figures for the US indicate that EVs, including plug-in hybrids like the non-solar C-MAX Energi, accounted for sales of just under 100,000 vehicles in 2013, or 0.6% of the US car market, compared to nearly 500,000 hybrids, at just over 3% of total sales of 15.5 million. If the US Congress eventually pursues tax reform along the lines suggested by outgoing Senate Finance Committee chair Max Baucus (D-MT), then the federal EV tax credit of up to $7,500 per car, which has helped push EV sales to current levels, would be in jeopardy. Carmakers should be thinking seriously about the long-term value proposition for EVs on their own merits.
That’s where a car like the C-MAX Solar could shine. Once technology-hungry early adopters and the greenest consumers have been satisfied, the mass market will be seeking cars that compete on mainstream measures of convenience, cost and performance. In that light, even a Tesla that can be recharged to half its battery capacity in around 20 minutes via the company’s network of Superchargers falls short, compared to a gasoline car that can be refueled in under 3 minutes. No recharger on earth can deliver energy to a car at the effective rate of a gas pump, without dramatic changes in battery technology.
Yet the C-MAX Solar can do something that no other type of car can do: make its own fuel, in a car that can also be refueled conventionally at any gas station, anywhere. That could provide a unique selling point, enhancing the convenience of cars in a totally new way, rather than requiring compromises on convenience as other EVs do.
Conclusions – A Step Toward Better, Faster, Cheaper
I’ve long believed that the transition from fossil fuels to low-emission energy technologies has been hobbled by its dependence on government subsidies and would accelerate when those technologies can delivery attributes that outperform on measures of “better, faster, cheaper.” Ford’s solar prototype must still demonstrate that it can become a real production car, rather just than a car show concept. If it does, it could be an important step towards making EVs attractive to average consumers without requiring thousands of tax dollars in incentives. That could help create the basis for a truly sustainable transition to a new energy economy.