- New Scientist, 17 September 2008
- From New Scientist Print Edition. Subscribe and get 4 free issues
- Jim Giles
WE'RE crawling bumper-to-bumper down El Camino Real, a four-lane highway out of San Francisco, when a gap opens up in the traffic ahead. My driver, multimillionaire Elon Musk, seizes the opportunity and steps on the throttle. I'm instantly pinned to my seat, watching helpless as we surge with terrifying acceleration towards the rear end of a truck. Yet there's not even the faintest hint of the roar you'd expect from the nifty little sports car we're in. The engine barely makes a sound. That's because this is the Tesla Roadster, the first all-electric production sports car of the century. Musk brakes hard and once again we're crawling with the traffic, albeit a few cars further ahead.
Musk has a track record of successful technological leaps. He co-founded the online money-transfer company PayPal, and made his millions when it was sold to eBay in 2002. He is co-founder of the rocket company Space Exploration Technologies (SpaceX). Then in 2004 he decided to invest part of his new-found fortune in tackling what he considers to be one of the most important challenges of our age: cutting CO2 emissions from road transport. This sector is responsible for emitting one-fifth of global greenhouse gases. Musk weighed up the options and concluded that the most efficient way of cutting emissions was to build an electric car. He has become an evangelist for the technology. "In 30 years' time, the majority of cars in the US will be electric," he declares.
Time will tell whether Musk is right, but he has already achieved his first goal. A handful of Tesla Roadsters are now on the road, about 1000 have been ordered, and the model has already become a poster child for electric cars. With a top speed of 210 kilometres per hour (130 miles per hour), and an abilty to accelerate from 0 to 100 km/h in about 4 seconds, it has banished the pootling golf-cart image that dogged its predecessors.
What's more, it has maintained impressive green credentials. The Roadster produces no CO2 exhaust emissions, and even when you factor in the CO2 released in generating the electricity used to charge its batteries it produces less than half the amount of that emitted by the greenest gasoline cars on the market. Generating electricity from renewable sources would cut the Tesla's CO2 footprint still further. And it's cheaper to run than a gasoline-powered car - Tesla estimates it costs less than 2 cents per kilometre. One kilometre in a conventional car with a fuel consumption of 9 litres per 100 kilometres (26 miles per US gallon) - with gasoline at $3.60 per gallon - costs more than 8 cents.
However, at $109,000 apiece, Tesla Roadsters are aimed squarely at people with money to burn. It's designed to show that electric cars can be fun and sexy, not to be a practical runabout. Musk doesn't deny this. "I've no interest in the Roadster itself," he says. "It's a means to an end." Or, in other words, a proof of principle. The company's next car, which Musk predicts will be in production within three years, will be a family-sized sedan which he estimates will cost around $60,000. After that comes a compact version of the same car for $30,000.
It's a bold ambition. But are all-electric cars like these the best replacement for the gas guzzlers that dominate our roads? And if they are not, what is the best way to make a cheap low-emissions car without compromising on the comfort and performance consumers have come to demand?
The Tesla Roadster is certainly not the only design vying to knock conventional cars from pole position. With oil prices still far higher than we've been used to - and reducing CO2 emissions and cutting reliance on foreign oil at the top of the political agenda in the US and elsewhere - kicking the gasoline habit has become a priority for drivers and politicians alike. And with sales of gas guzzlers falling fast (see chart), mainstream car manufacturers are finally waking up to the message that lean, green cars are what people want.
The race is on to build the lowest-emissions vehicle, and car companies are hedging their bets with a spectrum of new technologies, each with its own pros and cons. In the past, the biggest fork in the road lay between all-electric cars on the one hand, and hydrogen-powered cars on the other. It may even be a hydrogen-electric hybrid that ultimately carries the day. But there are plenty of doubters with regard to both technologies.
Musk, for one, is adamant that hydrogen is a waste of time and will never match the capabilities of all-electric battery-powered cars (see "Whatever happened to hydrogen?"). Yet this July, Honda launched its first commercial car powered by hydrogen fuel cells - the Honda FCX Clarity - in Musk's home town of Los Angeles. Honda initially plans to lease 200 cars over three years, at a cost of $600 per month. BMW began a similar scheme last year, leasing 100 dual-fuel cars that can burn either hydrogen or petrol in their customised internal-combustion engines. Hydrogen still has a long way to go though, not least because the refuelling infrastructure is sorely lacking, with just 26 hydrogen refuelling stations across California to date, and only 150 worldwide.
Perhaps the biggest surprise announcement has come from General Motors, the company that brought us the ultimate gas guzzler, the Hummer, and only five years ago voluntarily destroyed its own fleet of low-emissions electric cars, dubbed the EV1 (see "The resurrection"). "We believe the ultimate solution is the electrification of the automobile - as soon as possible," said Jon Lauckner, a GM vice-president, at a green vehicles conference in San Jose, California, in July.
GM clearly has some catching up to do. In April this year, Toyota announced that it had sold its millionth Prius - its flagship low-emissions car. The success of the Prius has spurred GM to rework plans for a new plant in Mississippi. Instead of gas-guzzling SUVs, the plant will make cars that operate on a similar principle to the frugal Prius.
Unlike the Tesla, the Prius has a hybrid propulsion system that combines a gasoline-powered internal combustion engine with a battery-powered electric motor. At up to 25 km/h or so, the Prius runs near silently on its electric motor. Accelerate beyond that and a regular petrol engine kicks in, giving a combined fuel economy of about 5.1 l/100 km. Energy from the engine and energy recovered during braking tops up the battery so there is never any need to plug the car into the mains electricity grid.
The Prius uses nickel-metal hydride (NiMH) batteries - a tried and tested battery technology common in portable radios and other gadgets, and one that GM briefly employed on the second generation of the EV1. A few design changes, such as larger conductors within the cell, allow the batteries to deliver the tens of kilowatts needed to drive a car. They are also about half the weight of the equivalent lead-acid batteries - the type used in the first EV1s. While these accounted for about one-fifth of the mass of the EV1, the Prius batteries can be made much lighter as they only back up the gasoline engine, rather than replacing it completely. NiMH cells also last much longer than lead-acid batteries: some are still running after 10 years of regular recharging, says Ahmad Pesaran, an engineer at the National Renewable Energy Laboratory in Golden, Colorado.
But that's just the start. Over the past decade, engineers have been tinkering with the design of an even more efficient type of battery. This is the lithium-ion (Li-ion) cell, the kind used in laptops and cellphones. The result is lithium-ion batteries that can dramatically outperform NiMH cells, carrying about twice the energy for the same mass (see "Powering the next generation"). Some pre-production units are now in the final stages of testing. Pesaran estimates that the Li-ion cells will withstand 5000 recharge cycles. NiMH cells can take about 3000.
Li-ion batteries are still expensive, but according to analysts at the investment bank Morgan Stanley a new generation of batteries will help reduce their price and thus lead to cheaper hybrids and drive worldwide annual demand for the cars to 3 million by 2020. Last year 347,000 hybrids were sold in the US (see graph).
Plug in, switch on, drive off
While the existing Prius needs to continually recharge its batteries using its engine and regenerative breaking, the next generation of hybrids is likely to have higher battery capacity and be chargeable directly from the electricity grid. These are the so-called "plug-in hybrids". Prius enthusiasts who can't wait for the car's next incarnation are already beefing up their Priuses with off-the-shelf systems (see "Pumped-up Prius"). Plug-ins are likely to be the easiest way to begin cutting transportation-derived greenhouse gas emissions without the need for a new refuelling infrastructure which, for example, hydrogen would require.
A study by the Electric Power Research Institute (EPRI) in Palo Alto, California, concluded that hybrid cars charged with electricity produced in fossil-fuel power stations would still produce less greenhouse gas emissions than conventional cars (see chart). Another study, led by Michael Kintner-Meyer at the Pacific Northwest National Laboratory in Richland, Washington, calculated that the existing US electricity-generating infrastructure has sufficient capacity to supply 70 per cent of all car journeys if they were made in electric vehicles, without adding any new power stations. That's assuming that most cars are driven for less than 42 kilometres per day. On paper, at least, the message seems clear: to save the planet, go electric.
If Li-ion batteries perform so well, why not ditch petrol engines altogether? "The big question, the number one question, is cost," says Mark Duvall, an expert in electric vehicles at EPRI. A closer look at the Tesla explains why. The vehicle is not expensive by sports car standards, but the overall price conceals the cost of the 7000 or so Li-ion cells that make up the battery. Tesla will not comment on the cost of individual components, but Duvall estimates the battery alone would cost around $20,000 - as much as a conventional mid-range family car. Even so, Tesla's battery is cheap for its size because the company uses off-the-shelf cells already mass-produced for mobile devices. This presents another problem: wiring all these cells together creates a complex system that has multiple potential points of failure. Car manufacturers may baulk at the thought, preferring to keep things as simple as possible. So instead several are working on new designs consisting of about 10 cells. Unfortunately, kilogram-for-kilogram, these cells currently cost more than twice as much as existing off-the-shelf batteries.
Nevertheless, their greater simplicity and increased reliability are valuable factors. Tesla plans to adopt the technology in its next generation of electric cars. Using a smaller pack will also help keep costs down, giving their planned sedan a range of 250 kilometres between charges. But recharging will still be a problem. Recharging Tesla's existing Li-ion battery pack from the domestic supply, for example, takes about 3.5 hours.
Supporters of electric cars argue this shouldn't stop affordable ones finding their way onto the market because most people rarely need to drive long distances. In the US, for example, the average trip in a private car is less than 16 kilometres. Three-quarters of commuters in the UK drive less than 32 kilometres a day. These drivers could save hundreds of dollars a year if they switched to all-electric cars.
On-street electric charging points are already being tested in San Jose and other US cities. In the Netherlands, electric utility company Essent and the start-up Electric Cars Europe, are also developing a plan for installing charge points across the country.
Perhaps the most ambitious recharging scheme comes from the Californian start-up Better Place. Launched in 2007, the company is collaborating with the Renault-Nissan Alliance in a bid to mass-produce Li-ion electric cars and build the recharging infrastructure needed to make the vehicles attractive to drivers. The company plans to launch the service in Israel and Denmark first - both ideal starting points as each country's major population centres are confined to an area around 150 kilometres across. In Israel, for example, Better Place aims to have the cars in showrooms and half a million charging stations installed by 2011. The stations will be in malls, parking lots and other public places. If a car runs out of juice, rather than wait for it to recharge at a charging point, the driver would pull in to a refuelling station where a machine automatically removes the battery and replaces it with a charged one, all in around the time it takes to fill the fuel tank on a conventional car.
If all that sounds like another quagmire where a lack of infrastructure will slam the brakes on development, GM says it has an interim solution. The firm's upcoming electric vehicle, the Chevy Volt, will use a Li-ion battery to propel the car from 0 to 100 km/h in under 9 seconds, and up to a maximum speed of 160 km/h. When the battery is running low, a petrol motor kicks in, but not to drive the wheels; the motor only charges the battery. That means the experience of driving will always be like driving an electric vehicle, but with the added benefit of being able to recharge on the go rather than having to plug in and wait for hours. GM claims this will push the range of the Volt up to a very useful 575 kilometres. When gasoline is being burned to charge the battery, it runs with a fuel efficiency of around 4.8 l/100 km. Because the Volt can be plugged into mains electricity for recharging, most short journeys will run on electricity alone. No wonder some people are hailing it as a "Prius killer".
Whether GM can deliver on its promise remains to be seen. The company wants to launch the car in 2010, but the cost of the Li-ion batteries may bump the price up to around $40,000, hampering its mass-market prospects. The company is not revealing much about its investment in the project, but says it has 700 staff working full-time on it. "This is definitely not a niche product," says Rob Peterson, a GM spokesman. "It's the number one priority for the company."
Back in the Tesla, a few kilometres down the road, a man on the sidewalk turns and stares as we cruise quietly past. Then his face lights up in recognition: "Hey! It's the Tesla!" It seems that, in this corner of California, Musk has already made electric cars sexy. Now it's just the rest of the world that needs to be convinced.
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Whatever happened to hydrogen?
If you followed the developments in hydrogen-fuelled cars in the 1990s, you probably remember car makers proclaiming they were "only 10 years away" from the mass market. Ask them now and you'll hear something eerily similar. Yet the technology has not stood still: every year new prototypes are unveiled. In the last two years BMW and Honda have each committed to manufacturing a couple of hundred cars that will be available through lease to a lucky few who will help showcase the technology.
It's a sound idea, in principle. Hydrogen is a great energy carrier. It can be burned in an internal combustion engine, as inside the BMW Hydrogen Series 7 car, or combined with oxygen in a fuel cell to produce electricity to power electric motors, as does the Honda FCX Clarity. And given that they can be refuelled in minutes, emit only water vapour and have a driving range that matches conventional cars, they would seem to be an excellent solution to the problem of car emissions. So why has no manufacturer announced plans to mass-produce a hydrogen car?
It turns out there is no shortage of reasons why hydrogen cars may remain "10 years away" for several decades yet. For a start, the technology is far from mature. Fuel cells cannot yet meet the reliability standards expected by modern car drivers. Storing hydrogen is also tricky. It has to be compressed or liquefied, which requires high pressures or on-board cryogenic systems. Other technologies that avoid this, such as storing hydrogen in solids like metal hydrides, are yet to emerge from the lab.
Even if these technological hurdles are overcome, one of the biggest obstacles is the cost of building the infrastructure to deliver hydrogen for transport. To date, there are only about 150 hydrogen refuelling stations worldwide. That's compared with about 10,000 petrol stations in the UK alone.
It's a Catch-22 situation. Without filling stations, consumers will not buy hydrogen cars, yet since there are no hydrogen cars on the road, energy companies have no incentive to invest in building the stations. That's one reason why the US National Research Council (NRC) reckons that the government would have to spend $55 billion over the next decade or so to make fuel-cell cars competitive with conventional cars by 2023.
The council, which published its findings last month, did not write hydrogen off, however. Battery power may have more immediate potential but hydrogen cars, by virtue of being able to travel long distances on a single tank, were declared a viable long-term solution. Massive investment combined with development of a portfolio of hydrogen and electric technologies would mean that by 2050 cars could be almost entirely free of reliance on oil, the NRC says.
Powering the next generation
They're in cellphones, laptops and now electric cars. Lithium-ion (Li-ion) batteries are behind a quiet revolution in electronics. Though the technology is still relatively young - Sony sold the first commercial Li-ion batteries in 1991 - the batteries already dominate the portable device market. Their success is down to one key factor: they have a high energy density - and so are lighter per watt supplied - than all competing battery technologies.
While they have been a boon for portable electronic devices, Li-ion batteries have their drawbacks. Most notoriously, Sony recently had to recall more than a million laptop batteries because a handful had spontaneously caught fire.
Newer battery designs attempt to avoid that problem while boosting energy density still further. Yi Cui and his colleagues at Stanford University in California are pursuing one of the more promising options. Cui thinks that Li-ion cells would be able to pack more energy into the same space if the cathode, currently made from carbon, were made with silicon instead, as silicon can hold more charge than carbon. It has not been chosen in the past because it degrades during recharging: as lithium ions enter the silicon lattice, it expands, straining the electrode. Cycling the battery through many charge cycles eventually causes it to crack.
Cui's lab may have found a way around this problem. His electrodes are built from bunches of silicon wires, each one less than 100 nanometres in diameter. The small size reduces the strain that the electrode suffers when lithium ions flow in and out of the structure during charging and discharging, a process that causes the volume of the wires to change by a factor of 4 (Nature Nanotechnology, vol 3, p 31). Cui is also working with a new cathode material, which he declines to identify. In combination with his silicon, the electrodes could increase energy density fivefold, he claims.
Gerbrand Ceder, a materials scientist at the Massachusetts Institute of Technology, is using computer simulations to evaluate the potential of about 20,000 new cathode materials. He reckons that doubling the energy density in Li-ion batteries is more realistic.
Benjamin Jones is a student at Dartmouth College in Hanover, New Hampshire. He owns a two-seater 1991 Honda CRX which, according the US Environmental Protection Agency, should burn 8.7 litres of fuel for every 100 kilometres driven. Yet earlier this year, while driving in rural Missouri, he averaged a fuel consumption only a shade over 2.9 l/100 km (80 miles per US gallon).
That is not an unusual tale amongst extreme fuel-efficiency drivers. In this obsessive world, car owners go to extraordinary lengths to boost the distance they can drive on a tank of fuel. Often they will improve a car's aerodynamics by adding smooth wheel covers or wheel skirts, for example, or partial grille blocks. Some remove seats to reduce their car's weight, while others go as far as altering the transmission system to give gear ratios that reduce their engine's revs at cruising speed. In the extreme, a handful of enthusiasts are converting their own cars into home-made electric-hybrid vehicles.
Jones runs an online community at ecomodder.com where drivers exchange tips and ideas to cut fuel consumption. The site keeps an unaudited log of the most fuel-efficient cars. At the time of writing, pole position was held by a 1976 Vanguard CitiCar at 1.7 l/100 km (140 miles per US gallon)
A lot can be done to cut fuel consumption without making any technical changes to your car. A simple gadget that plugs into the engine can give drivers a real-time read-out of their fuel efficiency, and once presented with that figure they soon learn how to drive more efficiently, says Jones - for example, by accelerating less dramatically, and avoiding routes with traffic lights to cut down stops and starts.
On a dusty street in an industrial area close to San Francisco, Pat's Garage looks like any other mechanic's shop. But over the last 18 months, Pat Cadam and colleague Nick Rothman have been performing some radical tinkering on a select few cars that have passed through their doors. They've supplemented 50 Toyota Priuses with 5-kilowatt lithium-ion (Li-ion) batteries and modified them so they can be plugged in - rather than only charged using their petrol engine - and run purely on electricity at up to 55 kilometres per hour before the petrol engine kicks in to help out. In unmodified Priuses, the petrol engine kicks in at around 25 kilometres per hour.
This means that in trips around town, the gasoline engine in a modded Prius rarely turns on. That leads to significant fuel and emissions savings. When I drove a few blocks with Cadam, the reading on the dashboard was stuck at 99.9 miles per gallon - Toyota had not designed the instrumentation to display higher gas-mileage rates.
One of Cadam's most famous customers is based just a few miles away in Mountain View. Google.org, the philanthropic arm of the web-search giant, is spending $10 million on RechargeIT, a project aimed at helping to speed up the introduction of low-emissions electric cars. Google engineers have been testing four Priuses and two hybrid Ford Escape SUVs, all supplemented with Li-ion batteries. This Google fleet has been put through its paces on 38 different routes, devised using US Department of Transportation data and designed to cover the range of journey types made by Americans. Last month, the company announced that these Priuses averaged 2.5 l/100 km. On urban journeys, that improved to 2 l/100km. Even the converted Escape got close to 4.7 l/100 km, almost halving the consumption of the most efficient conventional SUV.
These figures don't include the energy used to charge the batteries when plugged in, so these vehicles actually use significantly more energy than these numbers suggest. Even so, electric motors are so much more efficient than gasoline engines that plug-in hybrids could still reduce emissions of carbon dioxide by millions of tonnes every year. And with gasoline prices looking likely to stay high, Li-ion hybrids come out on top even for those consumers who care about counting the pennies more than saving the environment. At 4.3 cents per kilometre, a journey in one of Google's cars costs at most half as much as in a conventional car.
Industry's first modern-day foray into the electric car market was a controversial one. In 1996, General Motors launched it's EV1 all-electric car (left). The EV1's development was triggered by Californian laws demanding that car makers in the state start producing zero-emission vehicles, but a legal challenge mounted by the manufacturers followed as quickly as the cars appeared. Critics allege that GM was never enthusiastic about the project. Only 800 EV1s ever hit the road, all of them leased rather than sold, and the company retained the right to withdraw them.
Many leaseholders loved the sleek, quiet EV1s and made overtures to GM to buy them. The car giant rebuffed most of these offers and in 2003 the vehicles were withdrawn and crushed.
In 2006, Sony Pictures released the film Who Killed the Electric Car? In it, GM was accused of conspiring with oil companies to sink electric-vehicle technology. In response, GM put a statement on its website which said in part: "When GM launched the EV1, gas was cheap, there wasn't a war in Iraq, and there was less discussion about global warming. There were far fewer reasons for people to make the trade-offs in their transportation lifestyle to make the EV1 work for them. The good news is that both the technology and the GM team who developed the EV1 live on. We didn't kill the electric car; electric vehicle technology is far from dead."
"TESLA ROADSTER: 248 hp electric engine powered by 450 kg lithium-ion battery... Top speed: 200 km/h(electronically limited)... Acceleration: 0-100 km/h in 4 sec... Price: $109,000... CO2 emissions: 25-46 g/km... Effective fuel consumption: 1 l/100 km"
"TOYOTA PRIUS: Hybrid: 1.5 litre petrol engine and 67 hp battery-powered electric motor...CO2 emissions: 104-130 g/km... Fuel efficiency: 5.1 l/100 km... Top speed: 170 km/h... 0-100 km/h: 10.9 sec... Price: $22,000... Range: 875 km"
"HONDA FCX CLARITY: Fuel cell running on hydrogen gas powers a 134 hpelectric motor... CO2 emissions: 80-151 g/km... Effective fuel consumption: 3.5 l/100 km... Top speed: 160 km/h0-100 km/h: 10 sec...Price: $600 per month... Range: 450 km"