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Why Arizona's Solar-Powered Train Won't Work

Another day, another proposal for a multi-billion dollar rail line in the United States. An Arizona company called Solar Bullet wants to build a 220 mile-per-hour train from Tucson to Phoenix, a journey of about 115 miles. Aside from the whopping $27 billion price tag for just the first phase, this idea has garnered a rush of attention for another reason -- the promise to make it solar powered.

Four parallel tracks (not shown in the artist's rendering) would run fast and slow trains in each direction, with the slow one making six intermediate stops and doubling the one-way time to 60 minutes. Over the tracks for the entire distance would be a solar panel array, providing the necessary power, which Solar Bullet says would be about 110 megawatts.

There's a sort of cool, kill-two-birds beauty to the idea of simultaneously reducing oil consumption through mass transit and powering it with solar panels. And all the company's two founders are asking is $35,000 for a feasibility study. But to save time, I conducted my own feasibility thought experiment, done for the cost of this posting.

The results were not encouraging. Here are a few reasons why Solar Bullet has a snowball's chance in the Arizona sun of succeeding:

  • Arizona is a great area for solar power, but like all our sunniest areas, doesn't have the population density to make mass transit sufficiently profitable
  • Solar power peaks at midday, whereas peak transit times are in the morning and early evening, before and after there's enough power available
  • While solar panels would cover all 115 miles, the trains would need power at specific points, potentially requiring expensive battery energy storage
  • Spreading panels across a vast distance adds greatly to maintenance costs, and would add an additional risk of theft and vandalism
  • Bond and loan costs for new train systems are already crushingly high; adding in solar will only add to that problem
The final point I might make is the most important: energy is all about price. Adding in cute distribution schemes is about showmanship or politics, and will inevitably fail because they tend to add enough extra cents to the cost-per-kilowatt-hour to make it impractical.

It's easy to poke holes in ideas like this, but ultimately they will have effects, albeit unintended ones. One possibility is that people will become fed-up with hearing about the next cool energy idea, something that has already happened to an extent. But the other, more helpful possibility is that talking about what will and won't work will be educational, helping us to make better choices in the future.

In the meantime, if you've got any more reasons that a solar-powered train would or wouldn't work, feel free to add them below.

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