Limits of Electrification

Is electricity a viable replacement for gasoline for all motor vehicles?

In an earlier post we looked at how practical it would be to turn school buses into electric vehicles. Turns out it is feasible, but not cost effective. That made me wonder whether electrification ever fails to be a viable solution.

Logical Extreme

To answer that, let’s start at the logical extreme. A fully loaded 18 wheel tractor trailer weighs about 80,000 pounds, or 40 tons. That’s quite a bit more than our school bus’s 14 tons but it is not outrageous.

Starting With Knowns

To answer my electric school bus question, I derived a number of values that will make it rather easy to answer this question. The key values are down below for any curious geeks like me.

How many Batteries?

Long haul trucking is largely about time. If we need to stop every 3 hours to charge for 8 hours, that is not going to be an attractive solution. If we want our batteries to be competitive with gasoline, we’ll need as much range as we can get. Ideally, a full day worth of distance on a fully loaded truck.

That makes my job simple. I’ll just toss a bunch of batteries on the truck and see how far they’ll take me.

A Reasonable Start

Let’s start with the first reasonable value; 1,000 kWh (enough to power a house for almost 2 months). The batteries to hold that energy add almost 20,000 pounds, 10 tons, to our truck.

19.71 (Pound ÷ kWh) • 1,000 (kWh) = 19,710 (Pound)

19,710 (Pound) ÷ 2,000 (Pound ÷ Ton) = 9.855 (Ton)

Sadly, it’s range is barely more than 100 miles.

5.13 (Ton Miles ÷ kWh) • 1,000 (kWh) ÷ 50 (Ton) = 102.93 (Mile)

Fortunately, it takes up less than 10% of our trailer

0.3 (Cubic Feet ÷ kWh) • 1,000 (kWh) ÷ 3,500 (Cubic Feet ÷ Trailer) = 0.08 (Trailer)

Not a bad star for $100,000 of batteries.

100 (Dollar ÷ kWh) • 1,000 (kWh) = $100,000

A Less Reasonable Next Step

For my next step, I considered 10,000 kWh of power (enough to power a home for more than a year and a half).

10,000 (kWh) ÷ 17 (kWh ÷ ((Home) x (Day))) = 588.2 ((Home) x (Day))

This battery costs a cool million dollars, but it gets us to a range of 370 miles. Again, cost is a problem, but I expected that. However, this battery consumes over 80% of a tractor trailer. I may need to add a second tractor trailer for just my battery in order to make this work.

Convergence

The next steps reveal the core problem. As I add more batteries, the balance of weight and distance enters a stalemate. Having 100,000 kWh of battery (powering a home for 16 years) gets me a distance of 500 miles and requires 9 trailers for just my battery.

The following step, 1,000,000 kWh of battery (160 years of power for a house) gets me a range of 518 miles but requires over 80 trailers of battery and costs about $100,000,000.

Even at over one trillion dollars in batteries, I’ll barely get over 520 miles.

How Far is Far Enough?

I couldn’t find data I’d call reliable here, but a number of sites specify daily driving ranges of tractor trailers of anywhere from 350 to 550 miles. That means our 370 mile battery is our first potentially viable option for range. Unfortunately, it isn’t practical since that battery consumes 80% of the trailer.

What Does that Mean?

Electrifying consumer vehicles may be a good option to reduce gasoline consumption and greenhouse gas emissions (it may even be viable for School Buses), but the same technology is not viable for commercial transportation (yet).

Variables

  • Soon, we’ll be able to get batteries for $100.00 per kWh
  • Modern batteries weigh about 19.71 pounds per kWh
  • Modern batteries consume about 0.3 cubic feet per kWh
  • Extrapolating from an electric car, let’s assume we can move one ton 5.13 miles on a single kWh. Alternatively, we could move 5.13 tons one mile per kWh. This is likely a generous estimate since the truck is likely less aerodynamic and will have friction from 18 wheels instead of 4. However, we’ll use it for now as it’s as sensible an estimate as I have.
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