Solar Cars — In Depth

Solar cars may soon become one more benefit of falling battery prices and the concurrent rise of fossil fuel costs. Since solar cars do not burn fossil fuels, they may reduce carbon dioxide emissions per vehicle by 43-54%. Recent advancements in battery efficiency may be the residual element that make solar cars ubiquitous. Until such a time, however, the small surface of a car limits the amount of energy that can be used to propel a car and its systems through solar power.

Since solar cars must be light and efficient, those that are constructed from ultralight composites are preferable, as they save weight. Prototype solar cars demonstrate the need for even more safety, technology, and — oh, yeah — design that’s a little bit more appealing to the average consumer.

Converting the sun’s energy through solar cell technology

The sun can power a vehicle when solar energy is converted into electric energy. Today, this conversion is usually obtained through photovoltaic (PV) cells, but new hybrid perovskite solar cells (PSCs) may surpass the conventional low-efficiency and stability that limits PV technology.

Sunlight is comprised of particles called photons. As both particles and waves, photons are responsible for refraction and diffusion. Some interesting characteristics about photons are that, as of what we know now, their frequency is independent of the influence of mass, they don’t carry a charge, and they can be a form of energy that is transferred or converted to other types of energy. It is that process of conversion that creates the photoelectric effect that makes solar power possible. When photons strike solar cells, they create a flow of electrons, resulting in electric current.

When exposed to sunlight, an arrangement of PVs produces power, but many other components are needed in order to conduct, control, convert, distribute, and store the energy produced in conjunction with PVs. These components can include a DC-AC power inverter, battery bank, system and battery controller, auxiliary energy sources and, sometimes, a required appliance. A balance of system hardware is needed, too, which involves wiring, overcurrent surge protection and disconnection devices, and other power processing equipment.

A PV system often uses batteries to store the energy it produces and to later supply that energy to electrical loads, such as at night or in cloudy weather. Batteries also supplement PV systems when they are near to their maximum power point, to power electrical loads at stable voltages, and to supply surge currents to electrical loads and inverters.  A battery charge controller keeps the battery from overcharging or overdischarging.

Less common than PVs but possibly more striking is recent research around inorganic-organic hybrid perovskite solar cells (PSCs). Cost effective, efficient, and possessing photostability, PCSs may change the way we think of solar cells. Dr. Seok at the Ulsan National Institute of Science and Technology in South Korea and a research team have studied how PSCs, a mixture of organic molecules and inorganic elements within a single crystalline structure, can work together to capture light and convert it into electricity. With unique crystal structures consisting of two cations and one anion, they can be fabricated more readily and inexpensively than silicon-based solar cells, due to their flexible and rigid substrate. PSCs reaching a photovoltaic efficiency of 22.1%, comparable to that of single crystalline silicon solar cells (25%), may, indeed, be the go-to solar cells of the future.

How a solar array creates enough energy to power a solar car

A solar array consists of hundreds of solar cells that convert sunlight into electricity. In order to construct an array, cells are placed together to form modules, which together build into an array. For an array to be able to power a solar car, one of the following configurations is generally used.

• Horizontal: Good for low latitudes; offers little interaction with the wind;
• Vertical: Free standing or integrated sails harness wind energy;
• Adjustable: Tilting the axis to increase power when the sun is low or to the side;
• Integrated: Covering every available surface with solar cells;
• Trailer: Retrofitting existing vehicles with little stability and may also include the batteries or drive motor;
• Remote: Mounting at a stationary location instead of the vehicle.

A selection of solar arrays to power a car involves a geometric configuration of optimal power output, aerodynamic resistance, and vehicle mass. Additional considerations can often include the surface area of a vehicle, degree of cooling of the cells and shading of the riders, mounting and encapsulation, and overall efficiency of the solar cell.

World Solar Challenge offers design and function inspiration for solar cars

The World Solar Challenge is an event created to offer universities and research institutes a venue in which they can design then race solar cars across 1878 miles of hot, dry Australian landscape. In 1982, two entrepreneurs, Hans Tholstrup and Larry Perkins, wondered if their home-built solar car, “Quiet Achiever,” could cross Australia from west to east. Success! The results inspired Tholstrup to prod others to explore the boundaries of sun-powered transport. With assistance from a major sponsor, the South Australian Tourism Commission, the World Solar Challenge continues today as a showcase for the development of advanced automotive technology and the promotion of alternatives to conventional vehicle engines. The event is held every three years.

Solar cars typically are low in profile, need a proven charging system, and contain a supplemental battery pack. Today, while solar cars push the limits of energy efficiency, they also can inform everyday vehicle technology.  World Solar Challenge cars must utilize no more than six square metres of solar panels as they test and promote the solar cars through an “ultimate synergy of nature, motion, and innovation.”

The three classes of World Solar Challenge entries are:

• Challenger Class: These tend to be smaller and sleeker with improved driver vision. They involve lateral thinking to meet the conflicting needs of maximizing the solar collection area, minimizing aerodynamic drag, meeting requirements for driver vision, and other design requirements.
• Cruiser Class: Entrants must work with specifications of payload, energy consumption, and, quite importantly, a subjective element of practical aesthetic design that would appeal to consumers around the world.
• Adventure Class: This is non-competitive and allows cars built for previous editions of the event to run again, usually with new team members. It can also be used as a catchment for those who, while meeting the exacting safety standards, may not have quite made full compliance with the latest requirements.

Many memorable solar cars have emerged from the World Solar Challenge:

The first World Solar Challenge took place in 1987, with winning entry, GM’s “Sunraycer” hitting an average speed of 42 mph. Ford Australia’s “Sunchaser” came in second.

The 2007 World Solar Challenge became the fourth successive victory for the Dutch Nuon Solar team in the challenge class, averaging 55.97 mph under new, more restrictive rules. The Belgian Punch Powertrain Solar Team’s “Umicar Infinity” placed second.

In 2012, a high school student and his mentor from Adelaide, Australia helped to design a solar-powered car to transport pregnant women in Zimbabwe to a local health clinic. They came up with a low-maintenance, solar-powered, three-seat vehicle that was capable of traversing difficult terrain.

“Stella,” a solar car with a real lack of aesthetic design appeal, first appeared in the U.S. in 2014. Students from the Eindhoven University of Technology in the Netherlands originally built the solar-powered vehicle as an entry in the World Solar Challenge race,  A more recent version comes with the claim that it produces more energy than it uses, has a range of 621 miles on a full charge, and can reach a top speed of 77.6 mph. Stella demonstrated that technology that had once been directed to the race track could also be applicable to the consumer market with combined performance and specialized innovation. It can discharge energy back into the grid, so it’s got the potential to be a prototype for other solar-powered vehicles that provide a mobile source of renewable energy.

The last time the World Solar Challenge was held was 2015. Here are the highlights of that event:

Challenger Class

1st Nuon Solar Car Team “Nuna 8” (The Netherlands) average speed 91.75
2nd Solar Team Twente “Red One” (The Netherlands) average speed 91.63
3rd Tokai University “Tokai Challenger” (Japan) average speed 89.41

Cruiser Class

1st Eindhoven “STE2” (The Netherlands). Total Score: 97.27 points*
2nd Kogakuin “Owl” (Japan). Total Score: 93.61 points*
3rd HS Bochum “Sunriser” (Germany) Total Score: 82.91 points*

Mainstream solar vehicle technology advances — with nearly mainstream solar cars close by

The 2010 Toyota Prius advanced solar automotive development with is solar-powered cooling system. With ventilation that was a separate function from the motor, the vehicle worked concurrently to maintain interior vehicle temperature and pointed us to the possibilities of solar cars of the future. In just the last month, moreover, Toyota has announced that its new Toyota Prius plug-in hybrid, called Prius Prime in the U.S., comes with a full length solar panel on the roof that helps recharge the car’s lithium ion battery when the car is parked. It also powers such things as air conditioning, power steering, power windows, and interior lighting while the car is being driven.

In 2015, Envision Solar International won a statewide contract from the State of California to provide EV ARC™ products to California state departments and other state and local agencies or entities. Envision Solar was proud to be able to announce, “This means that many CA government workers and employees will now be able to charge their electric vehicles with sunlight at their workplaces!”

The “Immortus“ is a limited edition bespoke solar electric sports car with on-board storage capacity. Inspired by the world portrayed in post-apocalyptic movies, the Immortus is designed to exhibit a toughness that no other car has: endurance. The ability to run on the power of the sun and store the energy for later use make it a car of significant endurance.

In conclusion

We may still be a good way off from a viable, commercially produced solar powered car. But solar cars have a lot of positives. Their panels work silently, so they don’t contribute to existing road noise pollution. They don’t create greenhouse gases, they use free solar energy, and they may be able to free us from dependence on foreign oil. Solar power has the potential to become a viable source of renewable energy for vehicles. We just need a bit more time, research, and innovation.

Photo credit: desertdutchman via Foter.com / CC BY

Toyota Says Lithium Ion Batteries Now Safe To Use

Until now, Toyota has been cool to the idea of using lithium ion batteries. Instead, it has preferred nickel metal hydride batteries in its hybrid cars. The problem, Toyota says, is that traditional lithium ion batteries can explode or burst into flame. That’s what is happening with the batteries in the new Samsung Galaxy 7 smartphones. Until recently, Toyota has been content to develop hydrogen fuel cell technology for its zero emissions cars of the future.

Now Toyota says it will use a lithium ion battery developed in cooperation with Panasonic in its new Prius Prime plug-in hybrid. “It’s a tall order to develop a lithium ion car battery which can perform reliably and safely for 10 years, or over hundreds of thousands of kilometers,” said Koji Toyoshima, the chief engineer for the Prius. “We have double braced and triple braced our battery pack to make sure they’re fail-safe … It’s all about safety, safety, safety,” he says. The Prius Prime will have an 8.8 kWh lithium ion battery, which should give the driver more than 30 miles of all electric range before the onboard gasoline engine kicks in.

Vastly improved control technology is what gives Toyota the confidence to use lithium ion batteries in the Prius Prime. The new system precisely monitors the temperature and condition of each of the 95 cells in its new battery pack. “Our control system can identify even slight signs of a potential short-circuit in individual cells, and will either prevent it from spreading or shut down the entire battery,” said Hiroaki Takeuchi, a senior Toyota engineer.

Panasonic has used its expertise in manufacturing lithium ion cells to increase the precision of battery cell assembly. Even microscopic metal particles or other impurities can trigger a short-circuit, overheating and potential explosion. “The environment where our lithium ion batteries are produced is not quite like the clean rooms where semiconductors are made, but very close,” Takeuchi said.

Battery experts say increasingly sophisticated systems that can track individual cell conditions are becoming closely guarded trade secrets. “State of charge management, safety management, and algorithm development is becoming one of the higher tiers of proprietary internal development,” said Eric Rask, principal research engineer at Argonne National Laboratory. “It’s very internal, very strategic, and companies are seeing management algorithms as a competitive advantage.”

“Developing lithium-ion batteries for both hybrids and plug-ins will enable us to also produce all-electric cars in the future,” said Toyoshima said. “It makes sense to have a range of batteries to suit different powertrains.” The use of the word “will” is important. It marks a possible turning point for Toyota, which needs to compete with battery electric cars coming from most of the world’s major manufacturers.

With hydrogen refueling infrastructure virtually non-existent in most of the world, fuel cell cars are not going to be competitive any time soon.  Hyundai will introduced a battery powered Ioniq in 2017. Toyota can’t afford to get too far behind in the zero emissions market segment.

Source: Reuters  Photo credit: Toyota

Toyota Prius May Switch To Plug-In Hybrid Technology Shortly

The Toyota Prius is the gold standard when it comes to fuel economy. The new Prius in Eco trim is capable of going up to 58 miles on a gallon of gas. That would have been unthinkable before Toyota married its hybrid technology to the internal combustion engine. The problem for Toyota is that it has painted itself into a corner. Improving on the Prius with its iconic Synergy Drive will be a tall order. It’s easy to make a Belchfire 5000 with a V-8 engine get 10% better gas mileage, but it’s a whole lot tougher to make a current generation Prius 10% more efficient. Nevertheless, people expect continuous improvements. What’s a poor car company to do?

According to Shoichi Kaneko, assistant chief engineer for the Prius Prime, creating the next generation Prius will be a difficult challenge. Because Toyota wants to lead the way in transitioning to a fossil fuel free transportation model, just making a better standard hybrid powertrain might not be enough. “Ultimately, PHEV may be the way to go,” Kaneko says.

Back in 2013, Toyota’s managing officer, Satoshi Ogiso, told the press, “To beat your own record becomes very difficult.” To get the current car to where it is today took a lot of small improvements. The engine is the most efficient production internal combustion engine ever built. Engineers took a little weight out here and massaged the sheet metal to get a tiny aerodynamic gain there. Now to get the next generation car up to 60 mpg or more will be incredibly difficult.

That’s why the company is thinking it may need to make plug-in hybrid technology the foundation of the 5th generation Prius when the time comes for it to debut. Making a plug-in hybrid powertrain standard equipment would allow Toyota to get to that next level.  It would move the brand forward while keeping the Prius relevant.

The new Prius Prime plug-in hybrid is the proof of concept car for Toyota’s future plans. Kaneko says Toyota poured a lot of resources into making the Prime the best Prius possible. Part of that is the addition of a new double wishbone rear suspension to improve ride and handling over the old beam axle. If the Prius Prime struggles in the marketplace, that could force Toyota to reconsider its plug-in hybrid strategy.

That would be unfortunate. Purist bemoan plug-ins as a stop gap measure, but it seems clear they will be an important part of the electric car revolution, at least for the next decade or so. If the Prius Prime has a lackluster sales performance, it will probably have more to do with its polarizing styling than its plug-in hybrid powertrain. The new car, with its multitude of slashes and creases, and its ungainly front and rear treatments, is unlikely to make anyone’s Top 10 Car Designs list.

2016 Toyota Prius Most Fuel Efficient Car Ever Tested By Consumer Reports

Until recently, the 2000 Honda Insight was the most fuel efficient car ever tested by Consumer Reports. It got 51 miles per gallon. But the 2016 Toyota Prius has just eclipsed that number. As tested, it returned 43 mpg in CR’s city driving test and recorded 59 mpg during steady state highway cruising at 65 miles per hour. The combined fuel economy as observed by Consumer Reports was 52 mpg. CR calls that a stunning achievement, especially since the prior generation of the Prius could manage “only” 44 mpg combined in its tests.

The improvement is due to close attention to details. The gasoline engine is now 44% efficient — one of the highest efficiency ratings of any production internal combustion engine. The restyled body is more aerodynamic for less drag and the transmission has been redesigned to reduce internal energy losses and make it more efficient as well.

The new Prius uses a lithium ion battery for the first time. It is lighter than the nickel metal hydride battery used in prior versions of the car and is more efficient at storing energy . It also costs more. With increased battery power, the Prius now operates in electric only mode more often during city driving.

The new Prius was delayed almost a year because company president Akio Toyoda wanted the car to have flashier styling, a better ride, and better fuel economy. He got his wish, Consumer Reports says.

“The 2016 Toyota Prius has sharper handling, a more cushioned ride, less grabby brakes, and nicer interior materials. And even with its flashy new exterior styling, the interior has plenty of space, while the hatchback layout makes it easy to haul large items. As such, the Prius is a proper family car for five occupants, with strong crash-test results.” It goes on to say the previous mileage champ, the original Honda Insight, “felt more like a two seat science project.”

Not everything about the new Prius pleased the testers. They disliked the wimpy gear selector and wished for more supportive seats on long drives. They also disliked the lack of rear visibility caused by the smaller rear windows used in the restyled body. The midrange Prius tested by Consumer Reports had a list price of $27,323.

Prius sales are down 22% so far in 2016. Many other manufacturers like Hyundai and Volkswagen are finally getting around to bringing Prius competitors to market just as buyers are flocking to larger, thirstier cars. Fuel economy is a low priority for many people who think low gas prices will last forever. It remains to be seen whether all the effort Toyota made to hone the Prius will pay off in increased sales volume.

Source and photo credit: Consumer Reports

Toyota Prius Super Bowl Ad Is…..Interesting?

Heck On Wheels! That’s what the new Toyota Prius is, if you believe this video that will debut during the Super Bowl on Sunday. Toyota is desperate to attract younger drivers to the Prius brand. At present, the average age of Prius drivers is almost as old as Buick owners. That’s not a good thing. It wants people to know its all new fourth generation car is sporty and fun to drive.

The world of automobiles is changing at a furious pace. Younger Americans are less interested in owning a car. Many welcome the coming “car sharing” paradigm that will let them rent a car only when they need one. The absence of monthly payments for a car loan and insurance, coupled with no expenses for fuel or parking sound pretty attractive to lots of city dwellers who are fed up with congestion and a lack of parking spaces.

So, is a Toyota Prius really “heck on wheels”? It’s interesting the title substitutes “Heck on wheels” for the much more powerful and emotionally charged “Hell on wheels,” especially when the lyrics to the accompanying song contain such words as “badass” and “mother trucking.” One can only imagine what shenanigans the director of  the video had to go though to get this low powered front wheel drive car to power slide through corners.

At the end, the star, who identifies himself as “Todd with a job,” is surrounded by a collection of the nerdiest geeks ever assembled on a single set. All of them look like refugees from their mother’s basement. They play exploding guitars and electronic zithers, as the pulsate around the parking lot in a scene worthy of a Black Sabbath concert. Are 20 somethings really that much into heavy metal from the 80’s? Toyota obviously thinks so.

Super Bowl ads are a mirror of American popular culture. They are watched by more people than a Donald Trump press conference. At $3 million for a 30 second spot, they can pay huge dividends it they connect with the audience. Kia’s happy hamster ads turned the dowdy Kia Soul into a hot selling, ultra cool ride. One of my personal favorites was The Magic Fridge, which almost made me want to drink light beer, before I came to my senses.

Every ad tells a story. It has a beginning, a middle, and an end. Most are laden with psychological motivators designed to make people want to open their wallets and buy stuff. Ads are also a way of transmitting cultural norms to viewers. You can read more about this phenomenon in a blog entry entitled Let’s Analyze Super Bowl Commercials! posted by master teacher Carolyn Fortuna on her website IDigIt Media.

What do you think of this ad? Does it appeal to its audience? Will it make the Prius the darling of the under 30 set? Let us know in the comments below.

Chevrolet Says Bolt EV’s Price Is $37,500

At last week’s introduction of the production-ready Chevy Bolt, GM hedged the specific price but in launching its consumer webpage, the automaker says it will definitely sell for $37,500 including delivery, and before incentives.

This otherwise official info precedes any more formal announcement which may pin on a price of a few dollars less, but the disclosure confirms what had been strongly hinted.

A $37,500 price furthermore was the goal all along. For that, Chevrolet is offering an electriccar with range to be over 200 miles, although its EPA ratings are among other critical numbers yet to announced.

As it is, 200-plus could double the best Nissan has to offer with regards to range per doller. The 2016 Leaf has been boosted this year with 107 miles range, and asking price is $35,050-and-up for the refreshed five-year-old car.

Thus far, more positive commentary than not has come forth for GM’s first purpose-built nationally marketed EV, and it’s hoped to move the plug-in market into greater relevancy for numerous consumers who’ve held out for more.

The Bolt is to be on sale by end of this year and with a full $7,500 federal credit will net for just under $30,000 although buyers will need to pay the whole selling price up front.

Just as relevant, in markets like California and others where state subsidies are available, even before dealer discounts the Bolt could net within the mid-high 20s scope people now pay for the world’s best-selling green car, the Toyota Prius.

Obviously a different kind of car, the Prius hybrid does burn gas. For 2016 the fourth-generation midsized Prius offers 52-56 mpg and unlike the compact crossover Bolt, can be filled at any gas pump for zero range anxiety.

But with federal data saying average daily driving needs are under 40 miles for 75 percent of all drivers, even those who double this will have a far-greater cushion with the Bolt’s 200-miles range.

More info is expected on the Bolt today at the Detroit Auto Show.

2016 Toyota Prius: First Drive Of 56-MPG Hybrid

When a Toyota Prius drive event comes with a handling course, you know that things have changed.

And in some ways, the all-new 2016 Toyota Prius hybrid is a very different car from the three generations of Prius that preceded it.

Perhaps the main difference is simply that it drives, handles, and feels pretty much like a regular car from behind the wheel.

We've been very eager to drive the fourth-generation Prius hybrid, which debuted in Las Vegas in September and made its first auto-show appearance just weeks later at the Frankfurt Motor Show.

It'll start to arrive at U.S. Toyota dealers in January, but we were able to put almost 100 miles on a pair of 2016 Prius models this week at the media drive event, when Toyota released full details of the new vehicle.

The main reason to buy a Prius has historically been its fuel efficiency, and the new model retains its title as the most fuel-efficient vehicle sold in the U.S. without a plug.

2016 Toyota Prius - first drive, Laguna Niguel, CA, Nov 2015

But while Toyota executives had said the company was aiming for a 10-percent improvement over the last model's 50-mpg combined rating, the reality is slightly more complex.

Most versions of the 2016 Prius are rated at 52 mpg combined (54 mpg city, 50 mpg highway).

The Prius Two Eco model, however, the lightest of all versions, delivers that 10-percent boost and a fraction more, coming in at 56 mpg combined (58 mpg city, 53 mpg highway).

Over the course of a long day spent in the two different models, including some spirited canyon driving and that handling course, we saw ratings on the car's fuel-economy meter ranging from the high 40s to 53.7 mpg.

We think it's safe to say that the new Prius should deliver a real-world 50 mpg under most circumstances, perhaps a bit less in cold weather.

Approaching the new Prius from the front, it clearly is the latest version of the Prius design idiom--but with a sleeker shape and a lower nose.

2016 Toyota Prius - first drive, Laguna Niguel, CA, Nov 2015

Toyota has made a point of noting that the Toyota badge on its nose no higher off the pavement than the badge on the Scion FR-S sports car, and the new car definitely looks lower and less slab-sided.

It's 3 inches longer, a fraction of an inch wider, and most importantly, the driver sits more than 2 inches lower in the car--which by itself gives the car a slightly sportier feel. Call it the anti-SUV seating position.

Accent lines below the windows and above the sills break up the flat metal of the sides, and it's not until the back of the rear doors that it all starts to go wrong.

While styling is obviously subjective, the combination of the traditional high tail with blacked-out roof pillars, tall question-mark shaped taillights, and a profusion of lines and creases produced grimaces in virtually every journalist in our driving wave.

2016 Toyota Prius - first drive, Laguna Niguel, CA, Nov 2015

Suffice it to say that at least the cars following you will know you're in a new Prius. No other vehicle looks remotely similar from behind.

Inside, the 2016 Prius uses nicer materials and less textured hard plastic, giving the cabin a more refined feel that's closer to the mainstream.

The dash sweeps around into the door caps, and we're especially fond of the available two-tone upholstery in a cream-and-beige combination.

The car's designers stuck with the single central Multi-Information Display at the base of the windscreen, now composed of a pair of 4.2-inch full-color TFT displays.

It's considerably cleaned up over the last version's monochrome and more chaotically laid-out display.

A color touchscreen now caps the vertical part of the center console, sitting slightly ahead of the dash itself and looking similar to the Toyota Mirai hydrogen fuel-cell vehicle--though slightly more restrained.

The 2016 Prius seats are a huge improvement over those in the last generation: They're less flat, with better contours from both the cushion and back-rest bolsters.

Toyota moved the peak of the new model's roof forward several inches--after boasting that they'd moved it rearward for the last generation--and that cuts into rear seat headroom.

2016 Toyota Prius - first drive, Laguna Niguel, CA, Nov 2015

The rear seat is also bolstered to move outboard occupants slightly inward--so in those rare occasions where a fifth passenger is riding in the middle, all three riders are likely to be somewhat uncomfortable because the outboard riders will be awkwardly angled against their bolsters.

Prius that doesn't drive like one

With styling and comfort out of the way, it's really the driving experience that distinguishes the new 2016 Prius from any previous model.

Put simply, it feels less like a Prius and more like a normal car.

Previous generations were renowned--and not in a good way--for utterly numb power steering, lack of feedback to the driver, and handling and roadholding that came in somewhere between remote and mediocre.

2016 Toyota Prius - rear suspension

The new car's movements in curves and over rises are predictable, and there's decent feedback from the electric power steering.

Combined with the lower seat position, it's possible to throw the Prius through corners a bit--though it's no Mazda or BMW, and no one will ever buy the 2016 Prius for sporty driving.

But the new model pretty much drives like any other car, to the point where we frequently forgot we were in a Prius--something almost impossible to do with the old car if you had any experience driving other vehicles.

That's a huge improvement.

New rear suspension, new batteries

Part of the reason for the better handling and driving experience is a new rear suspension that uses fully independent trailing arms, rather than the semi-independent rear torsion beam of the old car.

Among other design changes, Toyota has moved the battery from its old location below the cargo deck to the space under the rear seat. Effectively, the battery and gas tank have swapped places.

And in a first for the conventional Prius hybrid, there are two battery options. For the base Prius Two, a 1.2-kilowatt-hour battery pack uses the old, proven nickel-metal-hydride cell chemistry.

2016 Toyota Prius - lithium-ion battery pack

In every other model, however, a 0.75-kWh lithium-ion pack--far more compact and lighter--provides the same power output and degree of hybridization.

The difference in pack capacities, as a Prius engineer explained, was because the older nickel-metal-hydride battery operates in a very narrow charge band, while the lithium-ion pack can use considerably more of its state-of-charge range.

No AWD for U.S.

The new rear suspension is designed to allow an electric motor to power the rear wheels as well--in what Toyota calls e-All-Wheel-Drive.

Executives on the U.S. drive said they didn't see a demand for an AWD Prius in this country, so for now, that system remains available only in Japan--although several reporters from the wintry Northeast questioned that assertion.