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(updated June 2010)
As outlined in the paper on Transport and the Hydrogen Economy, nuclear power is relevant to road transport and motor vehicles in three respects:
- Hybrid and full electric vehicles potentially use off-peak power from the grid for recharging (but generally do not yet do so). This is electromobility.
- Nuclear heat can be used for production of liquid hydrocarbon fuels from coal.
- Hydrogen for oil refining and for fuel cell vehicles may be made electrolytically, and in the future, thermochemically using high-temperature reactors.
Towards Electromobility: cars
Hybrid electric vehicles are powered by batteries and an internal combustion (IC) engine. They may be parallel hybrid technology, with both batteries and/or engine propelling the vehicle (with sophisticated controls), or series hybrids, with the engine simply charging the battery. Both types may be capable of plugging-in to mains electricity from the grid, in which case they need much larger battery packs. For the series hybrid the engine then is used only when needed, so it can run at optimum speed and efficiency.
Higher capital cost of hybrids is offset by the prospect of slightly lower running costs and lower emissions. Better batteries will allow greater use of electricity in driving, and will also mean that charging them can be done from mains power, as well as from the motor and regenerative braking. These plug-in electric hybrid vehicles (PHEV) and a new generation of full electric vehicles (EVs) are on the verge of being practical and economic today.
Towards Electromobility: system
Widespread use of PHEVs and EVs which get much or all of their energy from the electricity grid overnight at off-peak rates will increase electricity demand modestly - in the order of 10-15%. More importantly it will mean that a significantly greater proportion of a country's electricity can be generated by base-load plant and hence at lower average cost. Where the plant is nuclear, it will also be emission-free.
Partnerships are starting to emerge between power utilities and automotive companies in anticipation of wider use of PHEVs and EVs in Europe. Deploying them is more of a challenge here than in USA because most cars are not garaged overnight so must be charged elsewhere, often more rapidly. In 2007 EdF and Toyota set up a collaborative trial in France using PHEVs (see below), and in 2008 RWE and Daimler announced an EV trial in Berlin involving 100 cars. The French trial was then extended to UK, with 50 EdF staff vehicles involved. Daimler already has Smart EVs on test in London. Part of the corporate collaboration relates to how users are billed, as well as how the cars are recharged.
Nissan has been developing alliances with local governments and infrastructure companies in several countries so as to commercialise its electric cars. In March 2010 it announced that it would initially build the Nissan Leaf EV in UK, investing £420 million and accepting a government grant of £20.7 million towards the battery plant and car production.
In March 2010, Nissan, Mitsubishi, and Toyota, with Tepco and Fuji Heavy Industries announced an association to establish a standardised technology in Japan for charging electric vehicles, with a view to making this global. The CHAdeMO Association expects to have 158 members including government bodies, and "20 foreign companies ….. such as automakers, electric utilities, charger manufacturers, charging service providers, and other supporting groups". Nissan has already selected AeroVironment to supply EV home charging stations in the USA for its Leaf EV from December 2010. These will fully recharge the battery from 220 volts in eight hours.
In May 2010 the Japanese government commenced a trial of Nissan EV taxis with California-based Better Place, based on rapid battery swaps in the Tokyo urban area, and with a view to establishing some 300 battery-swap stations there.
In October 2008 EdF announced partnerships with Peugot Citroen (which has since formed a partnership with Mitsubishi to produce and market EVs) and also the Renault-Nissan Alliance related to EVs and PHEVs. The former focuses on recharging systems and protocols, the latter on creating a large-scale zero-emissions individual transport system based on EVs. EdF claims already to operate the world's largest fleet of EVs - 1500 vehicles, and is now developing a new generation of innovative charging stations.
Ford, in collaboration with the US Electric Power Research Institute (EPRI), is undertaking a three-year test program on the Ford Escape PHEV to develop and evaluate technical approaches for integrating PHEVs into the electric grid. EPRI has identified nine utilities across North America to test drive the vehicles and collect data on battery technology, vehicle systems, customer use and grid infrastructure. In August 2009 Ford unveiled an "intelligent" system, testing one of the world's first vehicle-to-electric grids that will communicate with PHEVs for optimal battery recharging.
Volkswagen is pushing forward with EVs and series PHEVs, along with the Nissan-Renault and others. It sees fuel cell vehicles as "a pipedream."
In Italy, Mercedes Benz/ Smart and Enel are collaborating in an "e-mobility Italy" initiative which involves setting up an intelligent network of 100 public and 50 private charging points around Rome and putting an initial 100 Smart EVs on the road there. Enel claims that travelling a certain distance in an electric car requires around 40% less primary energy than in an equivalent petrol vehicle.
In the UK the government will subsidise the purchase of EVs and PHEVs from 2011, and also the provision of 11,000 municipal charging points by the end of 2013, 2000 of these being fast charge (80% in 20 minutes). To qualify, cars will need a range of 112 km, a top speed of at least 96 km/h and to meet EU safety standards.
In April 2010 the European Commission tabled a strategy for Clean & Energy-Efficient Vehicles. This included promoting common standards to allow all electric vehicles to be charged anywhere in the EU, encouraging the installation of publicly-accessible charging points, and research on recycling of batteries.
The 2010 Royal Academy of Engineering report said that "Results from electric vehicle trials show that EVs equivalent to a small petrol or diesel four-seat car use around 0.2 kWh/km in normal city traffic."
Hybrid electric vehicles
Hybrid electric vehicles have been on the market for several years and are now fairly sophisticated and reliable, and are consequently in high demand. However, today's hybrids still depend entirely on liquid fuels, while using regenerative braking to increase efficiency.
Hybrids have a battery which is charged by an internal combustion (IC) motor (as well as regenerative braking), and in full, or parallel, hybrids drive may be from both or either. They claim much enhanced fuel economy, though figures suggest that there is little advantage over efficient diesel motors in highway use. Their advantage is in urban driving, and their significance is mostly as an important step towards plug-in hybrid vehicles.
The Toyota Prius is the best-known hybrid car of this type. The Mk3 version has a 1.8 litre, 73 kW engine, a 10 kW AC generator/motor, a nickel metal hydride battery (mass: originally 45 kg reduced to 29 kg in 2004 model, Mk3 model unknown) and a 60 kW AC electric motor, all with sophisticated power electronics and controls. The battery pack is 6.5 Ah at 201.6 volts (1.34 kWh) delivering 27 kW and has an 8 year/160,000 km warranty (expected life is quoted at 240,000 km). From 2009 the battery pack was to be lithium-ion type, but NiMH has been retianed in Mk3. The range on battery-only is very small however. The vehicle cost is about 30% more than a comparable conventional vehicle. Toyota has a larger full-hybrid vehicle, the Highlander SUV.
Honda has a different hybrid system, Integrated Motor Assist (IMA), using nickel metal hydride batteries charged (in the Civic and new Insight hybrids) by a 1300cc engine plus regenerative braking. The batteries mainly assist acceleration via a thin 10 or 20 kW electric motor /generator between the 60 kW engine and transmission. Unlike Toyota and Ford systems, IMA cannot function to any extent solely on battery power. The whole system has an 8-year warranty.
Ford has several hybrid models. The Escape Hybrid was launched in 2004. Like others, it utilizes a an Electronically Controlled Continuously Variable Transmission or eCVT to allow the distribution of power between the 2.5 litre internal combustion engine and the main electric motor to be determined by driving conditions, so that the engine is shut off when the electric motor can provide enough power to run it. It uses regenerative braking to help charge the 1.8 kWh nickel metal hydride battery pack. By March 2009, some 100,000 Escape Hybrids had been produced.
In New York, taxis have run a trial with 375 Ford Escape hybrid vehicles and authorities are repoted to be planning to convert the whole fleet of 13,000 by 2012.
Further interesting hybrid and PHEV designs are in an Appendix.
Peugeot's RCZ hybrid has a 1.6-litre diesel engine driving the front wheels and a 27 kW electric motor driving the rear wheels. It has regenerative braking to charge a high-voltage battery pack of unspecified capacity. It may be marketed from early 2011.
Mazda's Tribute hybrid is a more conventional full hybrid SUV with nickel hydride battery and 2.3 litre petrol engine. Mazda's Premacy hydrogen RE people mover has a lithium ion battery pack and a hydrogen-fuelled rotary engine. It appears to be a full parallel hybrid. Commercial leasing is envisaged.
The basic (non plug-in) hybrid vehicle's battery simply stores regenerated braking energy, helps with acceleration, and provides a very small amount of low-speed electric functioning.
Plug-in Hybrid Electric Vehicles (PHEV)
A further stage of the hybrid EV technology is plug-in hybrid-electric vehicles (PHEVs), or "gasoline-optional hybrid-electric vehicles" with a much larger battery than the hybrids described above and drawing most of their power, at least for short trips, from the electricity grid via the batteries rather than from liquid fuels. (Incidentally these can also supply power back to the grid when they are plugged in.) However, in contrast to the hybrid where the battery is mostly kept topped up, PHEVs (and full electric vehicles) need to be capable of repeated deep discharge.
There are two basic concepts with PHEVs: parallel and series. The parallel PHEV is like the Prius and Ford Escape, with drive from either battery or IC motor or both. The series PHEV such as the Volt simply uses the motor to charge the battery. With larger batteries this becomes an EV with "range extender" engine. A Mitsubishi concept has both series and parallel modes.
A Prius conversion to PHEV requires about 9 kWh in battery capacity and the PHEV version of the Volt has about 16 kWh so that the engine becomes a range-extender simply to charge the battery with the GM E-Flex system. In August 2007 Toyota obtained approval for testing on road of a plug-in version of the Prius, the first small PHEV to be certified thus, though DaimlerChrysler has a small fleet of PHEV vans under test. With PHEVs a lot of driving, particularly short trips, can be in battery-only mode, hence zero on-road emissions. They can reduce overall petrol/gasoline consumption by something like 30 to 50 percent, but will consume most of the difference as electrical power - predominantly from the grid. Power consumption is variously quoted at around 0.16 kWh per kilometre but requiring 50% more capacity than power used (IEA 2008), to 0.3 kWh/km per tonne mass.
A PHEV with 16 kWh battery giving 30 km range cuts fuel consumption greatly, given that many cars do not travel much more than this daily, though the nickel metal hydride battery pack weighs four or five times as much as the Prius's normal one. Several dozen Prius cars in the USA have been modified to be PHEVs. The electrical efficiency (mains power to wheels) in PHEV is about 75-80%, or 25-30% overall from primary heat.
In 2005 DaimlerChrysler brought out a PHEV Mercedes Sprinter van prototype, with 107 kW (143 bhp) internal combustion engine and 90 kW (120 bhp) electric motor, its batteries giving it a 30 km electric range. This may lead to a commercial version with the technology.
GM's Chevrolet Volt is a series PHEV, with 16 kWh battery pack giving 65 km all-electric range. The Volt is intended for mass production and may be on sale from 2010. The Volt is essentially an electric vehicle with on-board 1.4 litre IC engine as "range extender", to charge the 175 kg battery pack when it is depleted, and power the 112 kW electric motor driving the front wheels. Full charging from mains takes about 3 hours on 220 volts and 8 hours on 110 volts. GM is promoting the vehicle as an "extended-range electric vehicle" rather than "plug-in hybrid". In Europe it will be called the Ampera.
The Audi A1 e-tron is a PHEV with a small Wankel motor simply to top up the battery. The single electric motor delivers 75 kW peak power or 45 kW continuous to the front wheels. The 380 volt lithium-ion battery has a nominal energy content of 12 kWh giving an all-electric range of 50 km, and weighs less than 150 kg. A fully depleted battery can be recharged in approximately three hours from a 380 volt grid. It has regenerative braking. The 250cc motor drives a 15 kW generator at constant 5000 rpm, and the whole charging set up weighs only 70 kg and is barely audible. The vehicle mass is 1190 kg and overall range is 200 km (with 12 litre fuel tank).
The Lotus Evora PHEV has two 152 kW electric motors driving each of the rear wheels independently via a single speed geartrain, integrated into a common transmission housing. A 17 kWh lithium polymer battery pack is centrally-mounted and can be charged from domestic supply overnight. It gives 55 km range. A 35 kW 1.2 litre 3-cylinder IC motor drives a generator to charge the battery and give range extension. The range extension pack weighs only 85 kg. Lotus says that this is an optimum compromise between large battery with mass and cost implications, and greater reliance on IC motor (as in Prius).
Toyota plans to introduce PHEVs equipped with lithium-ion batteries for fleet customers in Japan, the USA and Europe by late 2009 as well as speeding up the development of small electric vehicles for mass production, following on from its FT-EV concept car.
The Chinese F6DM is a plug-in hybrid made by BYD, and backed in the USA by Berkshire Hathaway. It has a lithium-ion iron phosphate battery giving it a range of 100 km on that alone. It can be recharged in 9 hours. The BYD F6e is a fully electric version.
Volvo has announced a diesel PHEV which is being deployed in collaboration with Vattenfall, the Swedish electric utility and is expected to be fully available in 2012. Its lithium-ion battery will be charged from a standard wall socket in about five hours, as well as by regenerative braking. Three test cars based on Volvo V70 are in operation.
Peugeot Citroen plan to market a HYbrid4 PHEV diesel in 2012.
Mitsubishi has announced a PHEV based on its i-MiEV (see EV section below). At low speed this PX-MiEV functions as an EV using lithium-ion batteries, with low battery level it functions as a series hybrid (engine charges battery), and at high speed as a parallel hybrid in the sense that the 85 kW, 1.6 litre petrol motor takes over the front drive, being assisted by up to 60 kW of electric power from two motors (front and rear) for acceleration. The concept is a 4WD, with a sophisticated control system and regenerative braking. Plug-in charging can be 100 or 200 volt domestic or at "high-power quick charging" stations giving 80% in 30 minutes. In EV mode it has 50 km range.
PHEVs are likely to remain competitive even when there is an option for the on-board energy carrier to be hydrogen rather than simply a battery and the on-board electric powerplant is then supplied through a fuel cell, so plug-in hybrid-electrics have a long-term application.
Full Electric Vehicles (EVs)
These are an extension of the PHEV concept, as well as substantially predating it. Plenty of these have been built, but mostly with heavy lead-acid batteries and for uses other than motor cars. Today a number of manufacturers are building EVs with over 35 kWh on board, using lithium-ion (or lithium magnesium oxide) batteries. A range of electric cars now starting to come on the market have energy usage of 10-20 kWh/100 km, with 15 kWh/100 km being typical best,* albeit without considering heating or air conditioning.
* Sustainable Energy - without the hot air, 2009, D MacKay, ch20.
The small Indian REVAi car made in Bangalore, popular in the UK as G-Wiz i, has lead acid batteries. It is very small, and registered as a heavy quad cycle. It weighs 665 kg (including 270 kg batteries) and has a 13 kW AC motor driven by 9.6 kWh of battery capacity, with regenerative braking. Recharge of 9.7 kWh is in 8 hours and range 77 km. In 2009 a L-ion version was released, with lithium-ion batteries, reducing the mass by 100 kg and recharge time to 6 hours, while increasing the range to 120 km and nearly doubling the price. This model also has provision for fast charging from 3-phase power: 90% in one hour.
General Motors produced the EV1 in the 1990s, first with lead-acid batteries then with NiMH batteries, but the 18 to 26 kWh on board did not give enough range and recharge was slow.
EVs and series PHEVs can eliminate the mechanical transmission (as well as the complex parallel PHEV control system) and have a drive motor/generator in each wheel, though this will affect the unsprung weight adversely and hence roadworthiness. But this is a very simple system and requires minimal further development apart from optimising batteries.
In May 2008 Nissan (with Renault) announced that it would downplay PHEVs and would mass-produce full electric vehicles from 2010 for Japan and US markets. In January 2010 Renault-Nissan claimed to be "the only automaker committed to mass-marketing all-electric vehicles on a global scale." It has formed numerous alliances with states, municipalities, utility companies and others to develop infrastructure for these. The Renault-Nissan alliance is spending EUR 200 million per year on developing EVs, investing EUR 4 billion overall, with 1000 staff working on the project at each of Nisan and Renault.
Considering vehicles with 50 to 100 kW motors, Renault-Nissan sets out three ways to charge them: Slow charge on standard network (10 or 16 amps, 220 volt) at home or workplace (6-8 hours), quick charge at service station (20-30 minutes, 32 amps, 400 volt) and battery swap (5 minutes), now in conjunction with Better Place (see below). The cars will have advanced lithium ion batteries in the floorpan with an effective life of five years. The initial Mixim concept has two 50 kW motors, front and rear, but other developments could have a motor at each wheel.
The Nissan Leaf has laminated lithium-ion batteries of 24 kWh driving an 80 kW synchronous AC motor with drive train and a range of 160 km from an overnight domestic charge at 240 volts, or 80% from public quick-charge station in 30 minutes. It can also be charged from 120 volts, and ha an onboard 3.3 kW charger and regenerative braking. It intended to be on the road in a few US states in December 2010 and is designed for the mass market from 2012. Renault in mid 2009 announced that it would market a range of four different EVs from 2011-12, with the vehicles being sold at about the same price as diesel equivalent and the batteries being rented. It expects running costs to be 20% lower and maintenance costs 50% lower than equivalent petrol vehicles.
The Renault Fluence ZE takes a 22 kWh lithium-ion battery with 250 kg mass powering a 70 kW synchronous motor and giving 160 km range. It will be built in Turkey and sold in Israel and Denmark from 2011 without any battery, this being leased in the Better Place system.
Toyota has stood back from EV developments while enjoying the success of its hybrid Prius. But in May 2010 it announced that it would invest $50 million in US-based Tesla and jointly develop a new low-priced EV - basically a Toyota with a Tesla powertrain. Tesla also bought the NUMMI car plant at Fremont in California as a base for all its manufacturing. The plant has a capacity of half a million vehicles per year and uses the Toyota Production System. Production will now be mainly the new Toyota-Tesla model and its own Tesla S, development of which is being financed by a $465 million federal loan, to be mass-produced from 2011. The target price for the new model with Toyota is less than $30,000.
More than 1000 Tesla Roadsters have now been sold, but this is a high-priced ($110,000), high performance EV. It has a 3-phase 185 kW motor driving through a single-speed 8.27:1 gearbox, and a 53 kWh lithium-ion battery pack weighing 450 kg. The vehicle mass is 1235 kg. The plug to wheel efficiency is quoted at 174 Wh/km. The Tesla S is much heavier (1735 kg) but half the price ($57,000, delivered in 2012). Its powertrain specifications are not public, except that it has a single-speed transaxle gearbox. It will have three lithium-ion battery pack options of 42, 65 or 85 kWh, giving 250, 360 or 480 km range, with charging from domestic power, 45 minute quick charge from 3-phase 480-volt/ 100 amp supply, or 5-minute under-floor battery pack swap.
Mitsubishi has developed the i-MiEV with 16 kWh lithium-ion battery pack giving it a range of 130 km (at 18 kW power instead of the full 47 kW), hence 7.5 km/kWh. It has regenerative braking. It recharges from 220 volts in 6 hours (through a 15 amp household plug), but can also take 80% charge in 35 mins. Mass is 1.1 tonne. It is now being marketed in RH drive markets Under a September 2009 agreement the i-MiEV will be supplied to Peugeot Citroen for marketing in Europe from late 2010.
In Tokyo the first three Nissan EV taxis commenced a 90-day trial in May 2010, promoted by California-based Better Place, which has focused on infrastructure rather than vehicles. Rather than recharging the actual vehicles, the entire battery pack is swapped in about one minute, since the taxis need to travel an average of 360 km during a 10-hour day. The Japanese government is supporting the Tokyo trial to establish the practicality of converting the city's 60,000 taxis to EV, eliminating a billion tonnes of vehicle CO2 emissions annually, and requiring 300 battery-swap stations.
Renault is building 100,000 switchable battery vehicles for Better Place's first full-scale deployments in Israel in 2011, followed by Denmark and Australia. The Renault-Nissan-Better Place partnership is non-exclusive, both sides seeking to make their systems and batteries available to multiple customers and users. Better Place has also signed a technology development agreement with China's Chery Automobile Co, the biggest independent carmaker in China.
In the UK, the company which makes London's black cabs is to develop an electric-powered version, which it is promoting as a "zero-emission urban taxi" designed for congested urban areas. Manganese Bronze has signed an agreement with Tanfield, to develop a battery-powered version of its TX4 London cab - the TX4E. Tanfield is to deliver an initial ten of these under an agreement with the UK Technology Strategy Board. Tanfield subsidiary Smith Electric Vehicles is the world's largest manufacturer of road-going commercial electric vehicles.
The new cab is now likely to be on the road in 2010 and could replace many of the city's 20,000 licensed cabs. It will have a top speed of 80 km/hr and a range of 200 km on one battery charge. It will be powered by an advanced electric drive train and an iron phosphate lithium-ion battery pack. The technology will be Tanfield/ Smith's well-proven all-electric system, recharged off-peak in 6 to 8 hours, and capable of rapid top-up in an hour. Running costs are expected to be well under half those of the present TX4 diesel version.
Meanwhile Smith has available in UK the Ampere van, powered by a 50 kW motor from a 24 kWh lithium-ion iron phosphate battery pack. It claims 160 km range on a single charge with 800 kg payload, and weighs 1520 kg (tare). It also produces the Smith Newton truck with up to 7 tonnes payload. This is powered by a 120 kW motor with 80-120 kWh lithium-ion iron phosphate batteries (recharge in 6-8 hours) and has a range of 160 km. The first US models were delivered in mid 2009. Ford is collaborating with Smith to power an EV version of its Transit van.
Peugeot Citroen have the C1 ev'le which claims to be the first UK 4-seater production EV. It has a 30 kW motor and a lithium-ion battery pack which recharges in 7 hours from 13 amp socket, giving the 900 kg vehicle a 110 km range.
Early in 2009 Ford announced four new small EVs being developed with Magna on the Focus and Fusion platforms, to be on the market by 2012. The test vehicles are powered by a 100 kW three-phase AC motor which drives through a single speed gearbox. A 23 kWh lithium-ion battery pack gives a range of 130km and can be charged from a standard 220 volt socket in 6 hours or 110-volt in 12 hours.
Volkswagen in 2009 unveiled its Eup! commuter EV with production model expected in 2013. It has 18 kWh of lithium-ion batteries (mass 240 kg of total 1085 kg) giving an electric range of 130 km. A US version will be bigger and have 200 km range. It can get 80% charge in an hour or full charge in 5 hours from 230-volt system. It uses Toshiba's SCIB (Super Charge Ion Battery) technology which is resistant to short circuits. Solar panels on the roof run ancillary systems.
BMW has developed the Mini-E. It has a 35 kWh lithium ion battery pack taking up the back seat area and weighing 260kg. It can be charged in 8-10 hours from a household wall socket (presumably at 16 amps on a 240 volt system, 35 amps on 110 volts) or in two hours with special fittings. A 150 kW motor gives the 1.5 tonne car a claimed range of 250 km, hence almost 7 km/kWh.
Mercedes early in 2009 announced its Concept BlueZERO E-cell car with 35 kWh lithium-ion battery capacity and a range of 200 km. The compact electric motor develops 100 kW peak (70 kW sustained) power and a maximum torque of 320 Nm.
Daimler has had Smart EVs on test in London and plans to market them in 2010. The current version has a 17 kWh lithium-ion battery pack giving a range of 135 km.
Major Chinese battery maker BYD expects to release its E6 car in California in 2010. It claims 300-400 km range and a battery life of 2000 cycles, using a lithium-ion iron phosphate battery giving less than 18 kWh/100km. Charging of 48 kWh battery pack is in 9 hours from 220 volt 10 amp (sic) domestic supply (presumably 2.2 kWh/hr), or one hour from fast charge point. Four power combinations are offered: 75 kW, 74 + 40 kW, 160 kW, and 160 + 40 kW, where a front traction motor delivers 450 Nm torque, a rear one 100 Nm. Mass is 2020 kg. BYD's F3e prototype had consumption of less than 12 kWh/100km and range of 300 km. It also has two corresponding serial PHEVs: F6DM and F3DM, the latter - with 13.2 kWh battery pack - having been on sale in China since 2008. <http://www.byd.com/company.php>
A University of Delaware test EV based on a Toyota Scion can run for some 200 km on a two-hour 240 volt charge or overnight 120 volt charge. The annual fuel cost of driving 400 km per week with off-peak charging is estimated at about $150, compared with $2500 for equivalent petrol-power. It also has vehicle to grid (V2G) capacity.
For many uses batteries on their own will be inadequate on several counts - they have poor performance in hilly regions, in winter temperatures and when the driver wants to run heating and air conditioning. While many battery vehicle drivers become well disciplined in their vehicle use so they can plan their journeys around the requirements of battery charging, the PHEV technology remains attractive to give greater versatility.
Sources of electricity
While all electricity generation technologies including renewables will play a part in meeting increased electricity demand for PHEVs and EVs, the positive implications of the scenario on nuclear power are:
The UK Department of Transport and teh Royal Academy of Engineering (2010) have both estimated that if the UK switched to battery electric vehicles, electricity demand (kWh) would rise about 16%. The US Electric Power Research Institute modeled 60% of US vehicle use being electric and found a 9% increase in electricity demand. As can be seen from the graphs above, this need not increase the system's peak capacity if most charging is off-peak, thereby greatly increasing the proportion of total generating capacity supplied by base-load plant - see below. A study conducted by the Pacific Northwest National Laboratory for the US Department of Energy in 2006 found that the idle off-peak grid capacity in the USA would be sufficient to power 84% of all vehicles in the USA if they all were immediately replaced with electric vehicles. Areva has calculated that if 10% of cars in France were electric it would increase base-load demand by more than 6000 MWe ("four EPRs", or 10% of nuclear capacity). In the above diagrams, assuming significant move to electric cars, the base-load demand is increased by about 35%.
PHEVs and EVs to a large extent will be able to utilise power at off-peak times (and at lower rates), hence drawing on base-load grid capacity and increasing the demand for that. This will mean lower average cost of power generated in the grid system, since the base-load component will become a very large proportion of the peak demand. If vehicle to grid (V2G) feed in peak periods is enabled, that will help reduce costs further, but there are some complexities to be overcome for this to happen.
Some battery technologies allow short-duration high-current opportunity charging that means an overall increase in power generating and distribution demand. The increasing electrical load will occur at a rate that can be accommodated by normal planning for additional power resources and infrastructure. PHEVs and EVs can contribute to oil independence, as well as cleaner air. Ford estimates that the payback period for the price premium on a PHEV is seven years.
A further development of EVs, or at least the infrastructure for them, is being pioneered by Better Place, in what are effectively "islands" for car populations - Israel initially and then Denmark. Here, full changeover battery packs will be offered. Nissan is involved with the project. A further development of the idea is for Tokyo's taxis. However, many manufacturers do not see this concept as viable since the battery design and structure is integral to the vehicle and they have no intention of standardizing batteries.
PHEV technology is seen as the base for later utilization of fuel cells simply because hydrogen is likely to be at least as expensive as petrol/gasoline and therefore any ability to use mains power will be economically attractive. Supplementing this is energy conservation (from regenerative braking) to a battery. The choice of technology for a PHEV power plant is likely to have much less impact than the plug-in aspect of the design enabling use of base-load mains power.
Battery technology and Charging
This is the key for both PHEV and EV: achieving high capacity with low mass and low cost, coupled with safety and a long life. Batteries need to be capable of repeated deep discharge. Also they are likely to need to run heating and air conditioning where there is no IC engine or where it switches off part time. They also need to be able to function to a satisfactory level in vey cold weather.
While current automotive fuels provide 12-14 MJ per kilogram mass (net of IC engine efficiency, 45 MJ/kg gross thermal), the best batteries provide only 2-3 MJ/kg (550-800 Wh/kg net), and that at twice the volume. Commercial batteries are much less than this (see below).
As well as being heavy and bulky, batteries are expensive. Costs today are reported to be about $1000 per kWh capacity, and the aim is to reduce this to below $500/kWh.
Lead-acid batteries are well known in traction roles as well as for starting cars and running accessories. But they are very heavy and only last a few years.
Nickel metal hydride (NiMH) batteries are well-proven and reasonably durable, though can be damaged under some discharge conditions.* They are similar to nickel cadmium (NiCd) batteries, but use a hydrogen-absorbing alloy as the cathode instead of cadmium.
* if a cell in a multiple assembly fully discharges the others may drive it to reverse the polarity and permanently damage it.
Research continues on lithium-ion batteries*, particularly their cathodes, which deliver more power from less mass and are constantly being improved in relation to safety, reliability and durability. Early ones used cobalt oxide cathodes, newer ones use manganese oxides or iron phosphates, which tend to be less efficient but are more reliable. A spinel structure (3D lattice with manganese) gives fast charge and discharge but lower capacity that cobalt-based type (though still 50% more than NiMH). A123 are reported to claim that their Li-ion batteries will last for at least ten years and 7000 charge cycles, while LG Chem claims 40 years life for lithium-manganese spinel batteries for the GM Volt.
* regarding lithium resources, see http://lithiumabundance.blogspot.com/
Ultracapacitors are another research frontier to provide electricity storage for cars, to supplement batteries in providing for acceleration, and also being able to accept high inputs from regenerative braking.
Regarding energy density, indicating capacity and hence run time, lithium-ion batteries hold about 110-170 watt-hours per kilogram of battery mass, the much safer and more durable lithium-ion iron phosphate and lithium-ion manganese batteries being at the lower end of this range. These compare with 29 Wh/kg from metal hydride (NiMH) batteries in today's Prius (though other published figures for NiMH batteries give up to 90 Wh/kg) and 30-40 Wh/kg from lead-acid batteries. But the Li-ion cost is now around US$ 1000/kWh.
For power density, indicating how much power can be delivered on demand, manganese and phosphate-based lithium-ion, as well as nickel-based chemistries, are among the best performers.
Lithium-ion batteries are specified for the GM Volt and the Fisker, and intended for Ford's forthcoming PHEVs and the electric London cab. However, most of those are likely to use more advanced ones with lithium-ion iron phosphate (LiFePO4 or Li2FePO4F) cathode, the latter giving a lower power density but greater service life. Both kinds are much safer than early ones with lithium cobalt dioxide cathodes. The Volt is charged in eight hours from 120 volt outlet or half that from 240 volts, so presumably at 16 amps.
Nissan has joined with NEC and a subsidiary, NEC TOKIN, to set up Automotive Energy Supply Corporation (AESC) to develop and market advanced laminated Li-ion batteries for use in PHEVs and EVs. AESC commenced operation in May 2008.
Nissan, EdF, and others envisage an infrastructure integrating three types of charging systems: from household supply overnight (6-8 hours, off-peak), similar slower charge in parking lots during the day, and fast charging points which will give up to an 80% charge in 30 minutes. In addition to these there should be 5-minute battery pack changeovers for long trips, raising the possibility of batteries being leased rather than owned, or electricity suppliers selling a service configured for different users, not just batteries and power.
Focusing on the home base, using a 13 amp plug such as standard in UK, and 240 volt system, a 16 kWh battery pack such as in the GM Volt could be recharged in 5.5 hours. Many battery packs will be much larger than this, so 40 amp charge points may often be necessary for overnight charging, particularly with 110 volt systems.
Fuel cell vehicles
Experimental fuel cell vehicles (FCV) are now appearing, starting with buses. For sources of hydrogen for these see companion paper Transport and the Hydrogen Economy.
Honda has unveiled its FCX Clarity hydrogen-powered fuel cell vehicle with lithium ion battery pack and announced plans for marketing it. The motor is 100 kW AC, with Proton Exchange Membrane fuel cell stack and 170-litre compressed hydrogen tank giving a range of 620 km. Vehicle mass is 1.6 tonnes. The first US deliveries are scheduled for July 2008 in southern California with a three-year lease term at a price of $600 per month, including maintenance and collision insurance. Over three years to 2011 Honda plans to deploy about 200 of these vehicles, some of them in Japan.
Toyota has announced that it has developed a fuel cell hybrid vehicle - Toyota FCHV-adv - equipped with a high-performance fuel cell stack and nickel metal hydride batteries. The design of the membrane-electrode-assembly (MEA) has been optimised to allow for low-temperature start-up and operation down to minus 30°C. Fuel cell output is 90 kW, matching the motor which delivers 260 Nm. Efficiency was improved by 25% from the earlier FCHV through improving fuel cell unit performance, enhancing the regenerative brake system and reducing energy consumed by the auxiliary system. In the 1.9 tonne 5-seat vehicle a 70 MPa pressure vessel is used to store hydrogen which allows for an operating range of more than 800 km in the Japanese driving-cycle.
Beyond the electric vehicle initiatives described above, the Renault-Nissan Alliance is developing fuel cell-powered electric vehicles. In 2008 two prototypes are in an advanced engineering phase:
Both FCVs have been created to demonstrate the viability of the fuel cell concept and to underline the Alliance's commitment to a zero emission future. During 2008 Nissan demonstrated the X-Trail FCV in six European countries and Renault showcased the Scenic ZEV H2. In August 2008 Nissan announced a new generation stack with power output increased from 90 kW to 130 kW, for larger vehicles. Fuel cell stack size is reduced by 25% to 68 litres from 90 litres, which allows for improved packaging flexibility.
The Mercedes-Benz B-Class with fuel-cell drive has passed its winter testing in northern Sweden and Mercedes plans to launch the first series FCV in mid 2010. Small-series production of the B-Class F-Cell was to commence in early 2010. A refined, more compact, yet more efficient system is used in this than the A-Class FCV. The compact electric motor develops 100 kW peak (70 kW sustained) power and a maximum torque of 320 Nm, surpassing the performance of a standard 2-litre petrol engine. Range is 400 km. At the same time, it uses the equivalent of just 2.9 litres/100 km of fuel (diesel equivalent).
An issue with using hydrogen in fuel cells is overall energy efficiency. If a nuclear reactor generates electricity which is used for electrolysis of water and the hydrogen is compressed and used in fuel cell powered vehicle, the efficiency is much lower than in the electricity is used directly in EVs and PHEVs.* However, if the hydrogen can be made by thermochemical means the efficiency doubles, and they are comparable with EV/PHEV.* Say 35% x 75% x 90% x 40% = 9.5% optimistaically, cf 35% x 85% = 30% for EV.
An Australian Academy of Science report in December 2009 summarised the situation regarding fuel cell vehicles: "Fuel cell technology currently has a number of unresolved problems before it can be used widely for motor transport. The most likely fuel cell type in cars will be proton exchange membrane fuel cells. These operate at around 90°C and would be ideal for vehicles if they can be produced cheaply and are robust, neither of which has yet been achieved. They also need to operate with hydrogen rather than natural gas. The only way this could be done is to use an on-board gas reformer which is very expensive, has a weight penalty and would probably have safety issues. Ceramic fuel cells can run with natural gas, but they operate at temperatures in excess of 600°C and therefore may be unsuitable for vehicular application."
Appendix: Further Interesting Designs
BMW has produced an ActiveHybridX6 4WD, for marketing in the USA from 2010, and a similar ActiveHybrid7 series. The parallel drive system consists of a 298 kW twin-turbocharged 4.4-litre V8 gasoline engine and two electric synchronous motors delivering 68 kW and 64 kW, respectively. Maximum system output is 358 kW, and peak torque reaches 781 Nm over a very wide range. It is able to run solely on electric power up to 60 km/h, with the internal combustion engine activated automatically when required. The two-mode transmission (stop-start and highway) uses a 7-speed automatic gearbox. The 2.4 kWh high-voltage NiMH battery pack is recharged partly through regenerative braking and maximum output is 57 kW. However, it gives an all-electric range of only 2.5 km.
From a stop and at low speeds, only one of the BMW's two electric motors is activated. As soon as the driver requires more power or increased speed, the second electric motor automatically starts the internal combustion engine. The second electric motor then serves as a generator to provide a supply of electric power to the vehicle systems. When driving steadily at a higher speed most of the power required is delivered by the combustion engine in a largely mechanical process. Here again, one of the two electric motors acts as a generator.
In August 2009 BMW announced its PHEV concept car. This is a parallel hybrid which combines BMW ActiveHybrid technology with an efficient 1.5 litre 3-cylinder turbodiesel engine in front of the rear axle and an electric motor on each axle, drive normally being from all three. The rear electric motor gives consistent 24.6 kW and peak 38 kW, linked with the diesel motor, the front one is synchronous giving continuous output of 60 kW and peak power of 83.5 kW. Regenerative braking from the rear axle charges the 10.8 kWh lithium-polymer battery pack which is arranged along the centre axis of the floor pan. Its mass is only 85 kg. Mains charging is through a 220 volt 16 amp plug, giving full, recharge in 2.5 hours. At 380 volts and 32 amps charge time is 44 minutes. Electric-only range is 50 km, giving 17.5 kWh/100km. Mass is 1400 kg.
In September 2009 Mercedes announced its Concept BlueZERO E-cell plus PHEV car based on its B-Class. This is a series hybrid, combining an efficient 1-litre 3-cylinder 50 kW turbocharged petrol engine (from the Smart) in front of the rear axle to charge the battery, and a compact 100 kW electric motor (70 kW sustained level) with a maximum torque of 320 Nm. It is front-wheel drive. Regenerative braking also charges the 17.5 kWh lithium-ion battery pack in the floor pan. Mains charging is at 3.3 kW, presumably through a 220 volt 15 amp plug, giving full recharge in 6 hours. Rapid charging is at 20 kW to give a 50 km range. Electric-only range is 100 km, giving 17.5 kWh/100km. An all-electric version has 35 kWh battery capacity.
The luxury Fisker PHEV, with first production to be delivered in 2009, has 80 km range on battery before the 2-litre IC motor kicks in and appears also to be a series PHEV. Charging in said to be 4 to 8 hours.
Ford has an Airstream PHEV concept car powered by a hydrogen-electric hybrid drivetrain - the HySeries Drive. The lithium-ion battery pack drives the vehicle and a compact steady-state fuel cell system is a range extender - the fuel cell’s sole function is to recharge the Li-ion battery pack as needed, using 4.5 kg of hydrogen on board. It can also be mains charged.
The Tesla Roadster EV is reported to have 56 kWh on board and to recharge its 450 kg of batteries from a 13 amp mains supply in 16 hours, or rapidly in 3.5 hours, though more recent figures say 8 hours on 120 volts*. Its motor is 185 kW, three phase. Vehicle mass 1.2 tonnes and claimed range is 350 km. Deliveries commenced in 2008. The Tesla S, development of which is being financed by a $465 million federal loan, will be mass produced in California from 2011.
* The 3.5 hr would mean 16 kWh per hour, so 64 amps charging rate on a 240 volt system, the 8 hours on 120 volts would mean 58 amps. Two mobile connectors are offered to enable "charge from any available electrical outlet": 240 volt 30 amp, and 120 volt 15 amp, along with a "high-power connecter". The battery pack is claimed to have a 160,000 km lifecycle and cost $12,000 to replace.
Porsche has produced 918 Spyder plug-in hybrid, as well as the Cayenne S Hybrid SUV with parallel full-hybrid drive, and the 911 GT3 R Hybrid race car with electric drive on the front axle and a flywheel mass energy storage.
The Spyder has a powerful V8 engine as well as electric motors on the front and rear axles with overall mechanical output of 160 kW. Power is transmitted to the wheels by a seven-speed transmission that feeds the power of the electric drive system to the rear axle. The front-wheel electric drive powers the wheels through a fixed transmission ratio. It has a fluid-cooled lithium-ion battery and uses regenerative braking. The driver can choose among four different running modes: The E-Drive mode is for running the car under electric power alone, with a range of up to 25 km. In the Hybrid mode, it uses both the electric motors and the IC engine as a function of driving conditions and requirements, offering a range from particularly fuel-efficient all the way to extra-powerful. The Sport Hybrid mode also uses both drive systems, but with the focus on performance. Most of the drive power goes to the rear wheels. In the Race Hybrid mode the drive systems are focused on pure performance, running at the limit to their power and dynamic output. With the battery sufficiently charged, a push-to-pass button feeds in additional electrical power (E-Boost), when overtaking.
The Porsche 911 GT3 R Hybrid has two 60 kW electric motors on the front transaxle supplementing the 4-litre rear engine. A flywheel stores energy from regenerative braking and supplies it for brief acceleration.
Volkswagen has produced a diesel-electric LI concept car, a narrow two-seater (fore & aft) with 10 kW electric motor assisting an 800 cc diesel engine giving 1.38 litres/100km.
The Norwegian Think (formerly Pivo) once owned by Ford has its Think City EV with 30 kW 3-phase motor, 160 km range, and sodium batteries standard with lithium-ion as option. Think quotes 9.5 hours recharge from 230 volts at 14 amps for 80% recharge. Mass is 1.04 tonnes including 260 kg battery pack.
Main Sources:Romm J.J. & Frank A.F. 2006, Hybrid Vehicles Gain Traction, Scientific American April 2006.Economist Technology Quarterly, 10/6/06.Brown, Russell 2006, Critical Paths to a Post-Petroleum Age (ANL paper).Phil Jones & David BarberR. Hunwick, Plug in Vehicles presentation 16/10/07. OECD/IEA 2008, Energy Technology Perspectives. AAS 2009: Australia's Renewable Energy Future Royal Academy of Engineering, May 2020, Electric vehicles: charged with potential.