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Solar on the car, not the road …

March 8th, 2017 · No Comments

The pace of global change accelerates with each passing year. Energy systems — which tend, even amid revolution (wood to coal, coal to oil, …), to change slowly — are struggling, globally, to adapt to how that pace of change is accelerating within them as well. Globalization combined with information technology reach combined with materials science explosion combined with business practice advances combined with the realities of climate change (and its risks/opportunities — even if denied by @TeamTrump/@GOP) … are all coalescing to create the circumstances for tectonic shifts.

Writ large, the average person (in the developed world, at least) doesn’t spend much time thinking about ‘energy’ other than concern over the gas tank level and paying bills (primarily ‘at the pump’ since electronic billing has removed even the electricity and gas bills from many people’s consciousness).  Most energy-system change is occurring essentially invisible to the average person … with the (partial) exception of solar power, which has become perhaps ‘the’ symbol of 21st century energy  and the technological potential for successful climate mitigation(again, with strong reality-denying exception of @TeamTrump).

Solar has seen massive price drops, continued double-digit percentage year-to-year growth rates, and expanded penetration into energy markets around the world. In the developing world, solar is providing a leap frogging out of energy poverty for literally tens (and soon 100s) of millions of people. Solar is emergent and increasingly dominate in off-grid (from highway signs to remote homes), industrial scale, and distributed grid-connected electricity generation.

In the public consciousness, something sparked mania

Do Solar Roadways stand up to scrutiny?

and went viral in 2014: Solar Roadways. While any decent analysis would show this an amusing dream that might merit some research/development work but that serious investment should put it in the back-of-the-line behind many simpler and more productive solar applications, that Solar Roadway mania seems to have taken root with multiple demonstration projects and even large-scale plans underway around the world.

A question to ask, however, is whether it makes more sense to have solar ‘on the road’ (solar roadways) or solar on the things using the road?

Solar car challenge (

The idea of directly powering transportation using solar power has a long history, with the oldest solar car race now over 30 years old. While capturing attention, this really has been niche rather than a serious near-term transportation option.

There have been uses for solar power in mobile platforms. For example,

  • solar panels on electric golf carts.
    • Interesting, when talking to business people trying to sell them, it is rarely the electricity value that their customers are interested in when they but a solar option. It is the maintenance / staff implication:  the cart driver who forgot to plug in a cart, leaving it w/out power after a few days, or the annoyance of having to go out and get a dead cart in the middle of the day.  Having solar doesn’t necessarily provide 100% of the carts’ electricity requirements (though gives a true off-grid EV option) but greatly reduces ‘ran out of power’ annoyances and while extending operating ranges.
  • Solar-powered unmanned aerial vehicles/aircraft
    • Aviation has been playing around with moving away from fossil fuels, including electrically powered aircraft leveraging solar on the wings. With light-weighting of equipment, including solar, this has moved from demonstration and experiment to actual applications starting with unmanned aerial reconnaissance/surveillance.
    • One option that has been explored by major manufacturers (such as Airbus) is installing solar power into commercial aircraft wings — not to power the aircraft but to power auxiliary systems, especially when on the tarmac, to reduce fuel drain to power them.

That last has been part of the automobile market, with Toyota offering a solar option for the Prius since the 2010 model year for powering the ventilation system. Think parking in the August sun — the solar would power the vents and reduce heat buildup in the Prius, both improving comfort and air conditioning loads when entering the car (think 30F or more reduced heat build-up). While enough to power a fan, that 50-watt panel couldn’t provide meaningful propulsion benefits and wasn’t hooked up to the car’s battery system.

‘Serious’, however, is now around the corner with Toyota about to start having the solar on the rooftop connected to the Prius battery.  While few are likely to drive their Prius solely from this panel (the original option would produce enough electricity for perhaps 2.2 miles/day of driving with a new Panasonic panel increasing that to nearly 4 miles/day), this actually could take a real dent out of the fuel use for many.  The average US driver is about 40 miles per day and a reasonable share of commuters travel under 15 miles each way to work.  Imagine you have a 5 mile commute and park in an open lot.  One could see the plug-in Prius’ solar panel covering 40% of your commute plus some share of non-work (those weekend, vacation solar days) driving.

Now, assuming actual achievement of 4 miles/day driving off the solar panel (an optimistic assumption, for multiple reasons: cars not driven every day, shading reducing production, etc …), this is less than 1,500 miles per year or under 10 percent of the average 16,550 annual miles driven. Again, however, this could provide a meaningful dent into the average driver’s use and enable some interesting enhanced range uses (such as ‘refilling’ the car’s battery while parked for an extended period parked away from a plug).

Now, the Prius solar roof isn’t going to revolutionize transportation and, for most, it remains “a better choice to put the solar panels on your house” rather than car roof, but it is a clear indication that integrating solar into mobile electric transportation has moved from ‘pipe dream’ into commercial reality.



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Tags: Energy · solar · transportation

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