Last Update: May 22, 2018
As a society we have had 100+ years of normalizing the convention that we refuel cars at gasoline stations. Regular as clockwork, every 300 miles or so, we are supposed to stop at a gasoline station to spend a few moments pumping carcinogenic fluids into our cars. Conventional wisdom says that's the only way to travel around.
An electric car powered by solar panels on the roof challenges that norm in two ways. First, as an electric car it is not refueled with gasoline but electricity. Secondly, the fuel is not acquired from a far distant land, does not involve carcinogenic fluids, and instead generated at the point of consumption, with no ill side effects on health or environment.
The gasoline car owner simply can't do the same. Normal gasoline derived from crude oil requires a few million years to cook underground before it can be extracted for use. Gasoline extraction and production requires huge industries, immense capital investment, hundreds of thousands of workers, and much more. The closest a gasoline car owner could get to making their own liquid fuel is to investing in the land to grow a big corn crop from which to make ethanol. But as we see below, that's highly impractical.
The electric car owner who owns their own home, and whose home is suitable for solar energy (south facing roof with an unobstructed view of the sky) can easily put up solar panels and generate enough electricity every day to power their home and their car.
See also: Understand home solar power system design with this detailed walk-through to understand how solar power is implemented.
For the sake of argument let's compare/contrast between:
- Powering an electric car with solar panels on a roof
- Powering a gasoline car with corn ethanol on your own plot of land
Powering a car with Corn Ethanol
Many gasoline cars can run on ethanol or a blend of gasoline and ethanol. None that I know of run on pure ethanol. Even if someone grows their own ethanol, they'll have to blend it with gasoline to run their car. We aren't going to consider that additional complexity, and when you're reading this, keep in mind the reality is more complex than this.
At the risk of an unnecessary detour, this
howstuffworks.com article goes over how much corn and land is required to create ethanol to power a car. A typical ethanol car gets 8.5 kilomoters per liter, and it takes 3.13 kilograms of corn to produce a liter of ethanol. Average Americans drive 15,000 miles a year, or about 24,150 kilometers a year.
- fuel required: 24,150 km / 8.5km/liter = 2841 liters of ethanol a year
- corn required: 2841 liters * 3.13 kg/liter = 8892.88 kg of corn per year per car
- land required: 8892.88 kg / 3,225 kg/acre = 2.75 acres of land growing corn per year per car
The corn doesn't magically make itself into ethanol. The fermentation process requires vats and grinding machines to process the corn, farm equipment to tend your field, and a lot of time to ensure the crop yield is up to snuff. These machines require money, and chemicals, and seed, and fuel, and labor.
The total land required might be 3-4 acres to grow and the ethanol required to power one car for one year. And there is additional costs in the machines, fertilizers, seeds, and labor required to grow that crop and convert it into ethanol.
This is completely impractical for the vast majority of us. It's difficult to get most people to grow a small vegetable garden. This project of growing corn to make ethanol is more like full fledged farming. Obviously individuals won't be doing this, but instead they would be buying ethanol at a gasoline station.
Since individuals won't be growing their own ethanol, let's consider the land impacts of powering the entire USA vehicle fleet on corn ethanol. This isn't a whimsical suggestion, since that exact plan is among the proposals to end the use of fossil fuels.
What about scaling this up to the 135 million passenger cars cars in the US? (
in 2006 according to the Dept of Transportation) Powering them all on corn ethanol requires 371 million acres of corn production, plus the industrial infrastructure to process all that corn into fuel.
That land requirement, 371 million acres, is almost the size of Texas, Alaska and California combined. (those three add up to 421 million acres) 371 million acres is about 10 Iowa's or about 8 Nebraska's.
Further, corn is supposed to be a food crop. According to the
US Census Bureau, in 2010 there were 920 million acres of farmland in the USA. Producing enough ethanol to power all US passenger cars would take over 1/3rd the total current farmland. Somehow we are supposed to keep feeding ourselves while diverting a huge portion of food production so it instead becomes vehicle fuel.
In other words, the proposal to power cars with Ethanol -- while it would eliminate increases in atmospheric CO2 -- is simply untenable due to the land required to grow the corn to make the ethanol.
Powering a car from solar panels
Now let's do a similar estimation for electric cars, starting with how much of a solar array is required to power a home and one car.
According to the
U.S. Energy Information Administration, the average "residential utility customer" in the U.S. consumes 10,837 kWh a year or 903 kilowatthours (kWh) per month. That's 30 kiloWatt-hours of electricity per day. Being an average some will consume more, others less.
According to an online calculator to estimate solar array size requirements, 100% coverage of 10,837 kWh/year requires an 8.42 kiloWatt solar array in an area (Columbia Missouri) with 4.75 hours of usable sunshine a day. In an area like Phoenix Arizona, with 6.58 hours of usable sunshine a day, the solar array required shrinks to 6.08 kiloWatts. How that works is the available solar power varies from area to area - Phoenix is sunnier than Columbia Missouri and can produce more electricity per acre.
Okay, the typical household requires 10-11,000 kWh/year, what about their car? For the average 15,000 miles per year of driving, and 300 Wh/mile, the average electric car should consume 4,500 kiloWatt-hours per year. Per electric car. A household with one electric car would then see its average electricity consumption rise to 15,337 kWh/year. Again, these are averages calculated on the back of a napkin. Some will consume more, some less.
Going back to the solar array estimating calculator, the size required in Columbia MO is now 11 kiloWatts or so. That will cover one household with one electric car.
According to a slide deck by the
Dept of Energy published in 2009, the average size of a home solar array is 3-5,000 kiloWatts.
A do-it-yourself 11 kiloWatt solar array from
freecleansolar.com costs $18,200, and consists of 40 solar panels along with racks and wiring and inverters. The roof space required is 750 square feet. Another similarly sized system from the same place, costing $19,000, has 35 panels, but still requires 750 square feet of roof space.
Therefore it's feasible for the average U.S. home to produce enough electricity, on their roof, to power the home and one electric car. That's more power than corn-based ethanol (home plus car, versus just the car) in a fraction of the land.
It's easy to conceive scaling this up to a large portion of the homes and others buildings in the U.S. In most cases solar panels on the roof can generate a large portion of the electricity required by that building. No land space has to be diverted from its existing use. Food crops can remain as food. The land is already taken up by homes and businesses and parking lots, and instead we'd be adding an additional function to that land, namely electricity production.
Conclusion
The connection between wind power, solar power, and electric cars is strong. So strong that often-times promotional shots of an EV show solar panels or wind turbines in the background.
It's so compelling that many electric car owners go ahead and put solar panels on their roof.
As we've just seen it would be feasible to supply a large portion of our collective electricity needs with solar panels on rooftops and over parking lots around the country. As we saw elsewhere, electricity from wind or solar power systems is a zillion times cleaner than any fossil fuel power plant possible.
What's holding us back? The thing holding us back from this result is the economics, but the cost of solar power is falling rapidly. We know in our hearts it's the right thing to do, let's do it already.
