Transportation 100 Percent Solar Powered?

by Solarevolution June 09, 2012 06:14
At this critical juncture in history, many factors must be considered in developing new transportation infrastructure. Going up blind alleys will be very costly; every day matters in the oil depletion count-down. The electric passenger car is one of those blind alleys, for many reasons. It's time to get a 21st century transportation system off the ground. Consider this thought experiment, Solar Skyways:
  • Cost of fleet maintenance: To maintain the global fleet of nearly 1 b vehicles including trucks, fuel at $5/gallon ($210/barrel, net after refining), wild guesstimate of 10,000 miles/year/vehicle [USA is 12,000] at 25 mpg, that's 10 T VMT (vehicle miles traveled; USA has 3 T VMT) = $2 T/year. Or, 30 B barrels at $100 * 60% [IEA] used for transport = $2 T. So, ignoring all other private vehicle maintenance costs, by eliminating fuel altogether for ground vehicles we have a budget of arguably $2T/year to offset new capital costs. Can we do better than that? If we were to transition to renewables in 10 years, we could invest $2T * 10 = $20 T in renewables infrastructure. After that, energy costs (maintaining solar systems) would be a tiny fraction of what it is today. No wars over oil, for one thing.
  • How much will Solar cost? Solar PV 4 meters wide yields 1 megawatt per mile. Placed over major roads (say 4 million miles worldwide, roughly 20-30%), we achieve 4 TW electric. Can we build 4 TW of solar for under $20 T? Prices are now <$3/watt installed at MW scale. That leaves money on the table to cover much of the cost of the Skyways' construction too.
  • How many vehicle-miles will solar deliver? Average worldwide solar capacity factor is 5 kWh/kW/day, so 4 TW * 5 * 365 = 7,000 TWh. Suspended robotic electric vehicles weighing 1/4 tonne will use < 200 Wh/mi, so we can achieve 7,000 T / 200 = 35 T VMT. (Recall USA has 3 T VMT; global is on the order of 10 T VMT. Projected global travel in 2050 is less than 35 T VMT.) It appears that we will have surplus electricity by 2X to share with the folks living along the street. Or we can have the solar panels 2 meters wide.
  • Load-matching: EVs charged at night for use in the daytime is a grotesque mismatch between source and sink (engineer-speak, or "supply and demand" to the economists) which would require mountains of batteries (and mountains conquered by huge mining trucks). Solar energy, on the other hand, occurs at the same time people do most of their traveling.
    Even in winter with less sun, people travel less anyway.
  • Won't we still need storage? Yes. Using the grid for storage will be far less costly than batteries. And if deep storage isn't ready for prime time yet, in the meantime maybe you get charged more for travel at night or on cloudy days in the wintertime. Beats having somebody blow up the Middle East in a huff!
  • Single use vs multiple use: If "Detroit" manufactures a car for private use, the cost is $20,000 per driver / 2 passengers per vehicle = $10,000/pax. If we manufacture an ultralight vehicle at $10,000 that is used in public infrastructure 10X per day, 2 pax, that cost will be $500/pax. If you and I go into competition with "Detroit" in these challenging economic times, who will win more customers?
  • Safety: The automobile has been considered an improvement on the quality of life. Tell that to the families and friends of the million people who die in traffic accidents every year. What about the tens of millions seriously injured? By getting urban vehicles off the ground, the land is freed for pedestrians and bicyclists who no longer have to fear for their lives.
  • Performance: When shared by five modes (trolleys, buses, cars, bikes, pedestrians) the existing public transportation infrastructure (a.k.a. streets) cannot perform well for any one mode. Cars get congested, trolleys slow to a crawl to avoid running over pedestrians, bicyclists and pedestrians meet walls of traffic. Put all vehicles above the human realm (gravity matters, after all) and everybody gets where they want to go painlessly and rapidly.
  • What might it look like?
    Uppsala Solar Podcar
  • Visual intrusion? Fair enough. You might ask Eddie Murphy (Bowfinger) how he feels about that!

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