By now everyone knows that electric vehicles (EVs) are much simpler to operate, with far fewer moving parts, no cooling water, pump, belts or fan, no muffler, exhaust or catalytic converter. They are eerily quiet and, of course, have no emissions at the point of use – indeed, none if charged from zero-carbon renewables.

Some experts believe that, at least for light-duty vehicles in sunny parts of the world, energy collected from the exposed surface of the EV itself can be sufficient to provide sufficient propulsion for limited mobility, say 20 to 30 miles. That means that the proverbial little old lady who only uses her car to drive to church on Sundays may never need to fill up or recharge her EV so long as the car is parked outdoors.

As reported in Energy Post in late October, the notion of solar cars is not as farfetched as it might have once seemed. David Hone, Shell’s climate change advisor, believes that solar augmentation, for example, in the form of solar roofs, may become widespread by 2030.

Falling Costs of Solar Power
Falling Costs of Solar Power

Fast things down under

As we talked about in an earlier post and video, Tesla’s home storage and the recent moves by Ikea to enter the domestic storage space, clearly indicates that there is an appetite for consumers to take ownership of the power space. What would it take for consumers to link their electric vehicles into their own generation however?

Experimental cars taking part in the latest solar race in Australia operate on roughly 1 kW of juice. That, of course is not enough to power a heavy SUV with air conditioning and golf clubs in the boot, but the range of solar-augmented EVs is likely to improve over time.

This year’s race included a cruiser category with four-seat “family cars” travelling the 3,000 km distance with a mere 64 kWh of external energy – enough to cause indigestion for oil company executives, if not nightmares.

As noted in The Energy Post, to put this into context, a Tesla Model S has a 100 kWh battery and a range of around 500 km. Modified Teslas have, however, managed to extend the range to 1,000 km, roughly 620 miles.

The Australian solar race – among the longest and most gruelling of its kind – started as a contest to see how university students can put their engineering skills to practical use. But over the years, this and other solar races have attracted major sponsors, including makers of solar panels, cars and car components. A growing number of experts, including Shell’s Hone, are convinced that super-efficient solar-augmented EVs may be the future of light-duty, short-distance transportation.

How a solar car works
How a solar car works

A question of physics

However, as Tom Lombardo writing in is keen to point out, the physics don’t currently add up.

As he describes the amount of sunlight reaching the Earth’s surface is about 1000 Watts per square meter. Given the surface area of a car, and assuming 100% efficiency, the EV could absorb 4800 Watts of solar power.  Furthermore, since 1hp is 746W, this equates to 6.4hp….less than a garden lawnmower.

All this explains why the solar roof Toyota offers on its new Prius hybrid models only extends the car’s range by 5 km, roughly 3 miles.

While it may not sound like much, given advances in technology, solar augmentation could be sufficient to meet the needs of ultra-light and super-efficient cars of the future offering a range of, say, 50 km or 30 miles per day – certainly more than enough for our little old lady friend to get herself to church on Sundays.

A power station on your drive

Such cars can become net power generators during summer months – assuming they are parked outdoor in sunny parts of the world – but may have to juice up from time to time during the winter months, cloudy periods, or when extended range or heavy lifting is required.

The numbers are obviously affected by location, the vehicle’s weight, and accessories such as air conditioning. Should large fleets of such cars emerge by 2030 or 2050, they can operate on no gas and no net electricity on an annual basis. Their excess generation during summer months would offset their shortfall in winter. That is not good news for oil companies or electric utilities

A bright future for Solar

Our next cars will not be entirely solar powered – that’s clear. Indeed, we’ve long argued that plug-in hybrids are the most likely next step.

The work being carried out in the Australian outback, and by engineers around the world, is starting to prove that although a solar powered car isn’t feasible, a practical, solar assisted EV is, clearly just around the corner.


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