Replacing the Internal Combustion Engine Dronfield U3A Modern Science Group considered various alternatives to the Internal Combustion Engine (ICE).

The following 5 alternative engine architectures have one major feature in common with the standard piston engines that have dominated the automobile for more than a century: Fuel is burned inside a chamber to convert chemical energy into mechanical energy for propulsion. However, that requires moving air and fuel in and exhaust gases out of the combustion chamber, all of which adds complexity and reduces efficiency.

Stirling In 1816, Scottish inventor Robert Stirling conceived of the closed-cycle engine with the working fluid (in this case, air) remaining contained within the device. The heat source—which could be almost anything, including combustion—is external to the engine. Pairs of pistons operate together to provide the complete cycle. The air in one chamber is heated via heat transfer through the cylinder wall pushing back the displacer piston, which is linked to a second power piston in the expansion chamber. As the heated air continues to expand, it displaces the power piston, which drives a crankshaft that produces rotational torque. As the air cools, both pistons move back to their original positions, and the process repeats. Until recently, Stirling engines were mainly used for stationary applications—in part because they were not suitable for typical transient applications where the power delivery varied significantly over time. However, newer configurations and the ability to use alternative fuels have revived interest, especially for range-extender applications where constant speed operation and low noise (due to the continuous external combustion) are beneficial.

Opposed-Piston Opposed Cylinder (OPOC)

The opposed-piston opposed-cylinder (OPOC) architecture has drawn considerable attention

recently with the emergence of a new company called Ecomotors. Ecomotors includes numerous

veteran auto-industry executives and engineers, including Don Runkle of General Motors and

Peter Hofbauer, formerly of Volkswagen.

The primary claimed advantage of the OPOC architecture is high power density and fuel

efficiency improvements of 50 percent over current spark-ignition engines. Ecomotors has

developed a modular configuration with each module consisting of two cylinders. Within each

cylinder are two pistons that are linked to a common crankshaft. The pairs of pistons oscillate

back and forth with a common combustion chamber between them. The OPOC engine operates

on a two-stroke cycle, with each piston exposing only the intake or exhaust ports, allowing better

management of which ports are open by timing each piston.

Hofbauer explains that the use of two pistons per cylinder allows the pistons to move only half

the distance for the same compression ratio so that the engine can run twice as fast. Like many

of these alternative architectures, the OPOC engine can run on a variety of fuels including both

gasoline and diesel as well as biofuels. Modules of two cylinders each can be joined together

providing as much power as needed for a given application while electronically controlled

clutches allow the individual modules to be shut down for reduced fuel consumption during light

loads.

Scuderi

For more than a century, virtually all the engines used have operated on either a two- or four-stroke Diesel or Otto cycle, with the entire combustion cycle taking place within any number of single cylinders. Each cylinder would have intake, compression, power and exhaust activities. The idea of the split cycle—in which one cylinder handles intake and compression and a second handles power and exhaust—dates back to at least the late 19th century, yet no one has ever had much success with it. The Scuderi Group hopes to change that with a split-cycle design it has been developing over the last several years. Each engine module consists of two cylinders and pistons tied together through the crankshaft and a high-pressure crossover passage. Because only air is being squeezed into the first cylinder, it has 75:1 compression ratio. The outlet valve of cylinder one releases the high-pressure air into a crossover passage where some cooling occurs. When the inlet to the second cylinder opens as that piston approaches the top of its stroke,

the high-pressure air rushes in from the crossover. After the valve closes, fuel is injected and ignited about 15 degrees past top dead center. This timing ensures that the air is not recompressed, which improves overall thermodynamic efficiency. Scuderi claims a normally aspirated version of its engine can produce up to 135 hp per liter, giving it much better power density and lower fuel consumption than conventional engines. An air-hybrid version using a high-pressure accumulator that is charged during vehicle coast-down could improve efficiency by another 50 percent. The Scuderi concept is compatible with spark-ignition operation on gasoline and other fuels or compression ignition with diesel fuel. The first functional Scuderi engine began testing on a dynamometer in mid-2009, and the company hopes to strike a production deal with an automaker within five years.

Free-Piston

The free-piston engine has some similarities to the OPOC but generally only uses two pistons per module. The pistons are attached to each end of a solid connecting rod and oscillate back and forth in the cylinder, alternately firing each piston on a two-stroke cycle. Free-piston engines have lower friction than traditional crankshaft-based piston engines as a result of reduced rotary motion. A free-piston engine can achieve up to 50 percent thermodynamic efficiency, or about double the efficiency of a conventional gasoline engine. However, that same lack of rotary motion makes this design problematic for use as a propulsion unit. One architectural configuration of the free-piston engine that could prove useful in the future is to use it as a generator for an extended range electric vehicle. Copper windings around

the central section of the cylinder could be combined with magnets on the connecting rod to generate electricity that would be used to charge a battery. The compact size of the engine and nearly vibration-free operation make this a viable alternative for these electrically driven cars.

Wankel

Felix Wankel's rotary design is not exactly a new engine architecture, having been used in a variety of production cars since he completed the first running prototype in 1957. Like several of the other architectures discussed here, the Wankel has the benefit of very high power density. The current 1.3-liter normally aspirated two-rotor design used by Mazda in the RX-8 sports car generates 238 hp. Unfortunately, Wankels have had issues with high fuel and oil consumption, which has limited their use in recent decades. However, several modern developments have made a revival of the Wankel a distinct possibility. New machining processes can provide much-improved surface finish on the chamber walls, and new seal materials can reduce oil consumption and improve durability. The addition of direct fuel injection will facilitate reduced fuel consumption and emissions by preventing unburned fuel from flowing out through the ports as the rotor sweeps by. The emergence of extended range electric vehicles (ER-EV), like the Chevrolet Volt, has suddenly provided a seemingly ideal application for Wankels. Because the engine in these vehicles is only used to drive a generator, it can be optimized for operation at certain fixed speeds rather than transient operation. The compact dimensions also make it easier to package in this type of vehicle, and its vibration-free operation allows more seamless charge-sustaining operation. At the 2010 Geneva Motor Show, Audi showed an ER-EV

concept based on its new sub-compact A1 that uses a Wankel range extender, and powertrain engineering consultants AVL and FEV have both shown similar demonstration vehicles in recent months. Even General Motors has acknowledged investigating the use of a Wankel for future generations of the Volt.

Using different Fuel

Hydrogen internal combustion engine vehicle

A hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen

vehicle using an internal combustion engine. Hydrogen internal combustion engine vehicles

are different from hydrogen fuel cell vehicles (which use hydrogen + oxygen rather than

hydrogen + air); the hydrogen internal combustion engine is simply a modified version of the

traditional gasoline-powered internal combustion engine.

History

Francois Isaac de Rivaz designed in 1806 the De Rivaz engine, the first internal combustion

engine, which ran on a hydrogen/oxygen mixture. Étienne Lenoir produced the

Hippomobile in 1863. Paul Dieges patented in 1970 a modification to internal combustion

engines which allowed a gasoline-powered engine to run on hydrogen.

Mazda has developed Wankel engines that burn hydrogen. The advantage of using ICE

(internal combustion engine) such as wankel and piston engines is that the cost of retooling

for production is much lower. Existing-technology ICE can still be used to solve those

problems where fuel cells are not a viable solution as yet, for example in cold-weather

applications.

BMW tested a supercar named the BMW Hydrogen 7, powered by a hydrogen ICE, which

achieved 301 km/h (187 mph) in tests At least two of these concepts have been

manufactured.

HICE forklift trucks have been demonstrated based on converted diesel internal combustion

engines with direct injection.

Alset GmbH developed a hybrid hydrogen systems that allows vehicle to use petrol and

hydrogen fuels individually or at the same time with an internal combustion engine. This

technology was used with Aston Martin Rapide S during the 24 Hours Nürburgring race. The

Rapide S was the first vehicle to finish the race with hydrogen technology.

Low emissions

The combustion of hydrogen with oxygen produces water as its only product:

2H2 + O2 → 2H2O

Combustion of high temperature combustion fuels, such as hydrogen, kerosene, gasoline, or

natural gas, with air can produce oxides of nitrogen, known as NOx emissions. Although

these are only produced in small quantities, research has shown that the oxides of nitrogen

are about 310 times more harmful as a greenhouse gas than carbon dioxide.[8] Tuning a

hydrogen engine to produce the greatest amount of emissions possible, results in emissions

comparable with consumer operated gasoline engines from 1976

H2 + O2 + N2 → H2O + N2 + NOx

Adaptation of existing engines

The differences between a hydrogen ICE and a traditional gasoline engine include hardened

valves and valve seats, stronger connecting rods, non-platinum tipped spark plugs, a higher

voltage ignition coil, fuel injectors designed for a gas instead of a liquid, larger crankshaft

damper, stronger head gasket material, modified (for supercharger) intake manifold, positive

pressure supercharger, and a high temperature engine oil. All modifications would amount to

about one point five times (1.5) the current cost of a gasoline engine.[10] These hydrogen

engines burn fuel in the same manner that gasoline engines do.

The power output of a direct injected hydrogen engine vehicle is 20% more than for a

gasoline engine vehicle and 42% more than a hydrogen engine vehicle using a carburetor

Liquid nitrogen vehicle

A liquid nitrogen vehicle is powered by liquid nitrogen, which is stored in a tank. Traditional

nitrogen engine designs work by heating the liquid nitrogen in a heat exchanger, extracting

heat from the ambient air and using the resulting pressurized gas to operate a piston or

rotary engine. Vehicles propelled by liquid nitrogen have been demonstrated, but are not

used commercially. One such vehicle, Liquid Air was demonstrated in 1902.

Liquid nitrogen propulsion may also be incorporated in hybrid systems, e.g., battery electric

propulsion and fuel tanks to recharge the batteries. This kind of system is called a hybrid

liquid nitrogen-electric propulsion. Additionally, regenerative braking can also be used in

conjunction with this system.

Description

Liquid nitrogen is generated by cryogenic or reversed Stirling engine coolers that liquefy the

main component of air, nitrogen (N2). The cooler can be powered by electricity or through

direct mechanical work from hydro or wind turbines.

Liquid nitrogen is distributed and stored in insulated containers. The insulation reduces heat

flow into the stored nitrogen; this is necessary because heat from the surrounding

environment boils the liquid, which then transitions to a gaseous state. Reducing inflowing

heat reduces the loss of liquid nitrogen in storage. The requirements of storage prevent the

use of pipelines as a means of transport. Since long-distance pipelines would be costly due

to the insulation requirements, it would be costly to use distant energy sources for production

of liquid nitrogen. Petroleum reserves are typically a vast distance from consumption but can

be transferred at ambient temperatures.

Liquid nitrogen consumption is in essence production in reverse. The Stirling engine or

cryogenic heat engine offers a way to power vehicles and a means to generate electricity.

Liquid nitrogen can also serve as a direct coolant for refrigerators, electrical

equipment and air conditioning units. The consumption of liquid nitrogen is in effect boiling

and returning the nitrogen to the atmosphere.

In the Dearman Engine the nitrogen is heated by combining it with the heat exchange fluid

inside the cylinder of the engine.

Criticisms[ Cost of production[

Liquid nitrogen production is an energy-intensive process. Currently practical refrigeration

plants producing a few tons/day of liquid nitrogen operate at about 50% of Carnot efficiency.

Currently surplus liquid nitrogen is produced as a byproduct in the production of liquid

oxygen.

Energy density of liquid nitrogen

Any process that relies on a phase-change of a substance will have much lower energy

densities than processes involving a chemical reaction in a substance, which in turn have

lower energy densities than nuclear reactions. Liquid nitrogen as an energy store has a low

energy density. Liquid hydrocarbon fuels by comparison have a high energy density. A high

energy density makes the logistics of transport and storage more convenient. Convenience

is an important factor in consumer acceptance. The convenient storage of petroleum fuels

combined with its low cost has led to an unrivaled success. In addition, a petroleum fuel is

a primary energy source, not just an energy storage and transport medium.

The energy density — derived from nitrogen's isobaric heat of vaporization and specific heat

in gaseous state — that can be realised from liquid nitrogen at atmospheric pressure and

zero degrees Celsius ambient temperature is about 97 watt-hours per kilogram (W-hr/kg).

This compares with 100-250 W-hr/kg for a lithium-ion battery and 3,000 W-hr/kg for a

gasoline combustion engine running at 28% thermal efficiency, 30 times the density of liquid

nitrogen used at the Carnot efficiency.

For an isothermal expansion engine to have a range comparable to an internal combustion

engine, a 350-litre (92 US gal) insulated onboard storage vessel is required.[7] A practical

volume, but a noticeable increase over the typical 50-litre (13 US gal) gasoline tank. The

addition of more complex power cycles would reduce this requirement and help enable frost

free operation. However, no commercially practical instances of liquid nitrogen use for

vehicle propulsion exist.

Frost formation

Unlike internal combustion engines, using a cryogenic working fluid requires heat exchangers to

warm and cool the working fluid. In a humid environment, frost formation will prevent heat flow

and thus represents an engineering challenge. To prevent frost build up, multiple working fluids

can be used. This adds topping cycles to ensure the heat exchanger does not fall below freezing.

Additional heat exchangers, weight, complexity, efficiency loss, and expense, would be required

to enable frost free operation.[

Safety

However efficient the insulation on the nitrogen fuel tank, there will inevitably be losses by

evaporation to the atmosphere. If a vehicle is stored in a poorly ventilated space, there is

some risk that leaking nitrogen could reduce the oxygen concentration in the air and

cause asphyxiation. Since nitrogen is a colorless and odourless gas that already makes up

78% of air, such a change would be difficult to detect.

Cryogenic liquids are hazardous if spilled. Liquid nitrogen can cause frostbite and can make

some materials extremely brittle.

As liquid N2 is colder than 90.2K, oxygen from the atmosphere can condense. Liquid oxygen

can spontaneously and violently react with organic chemicals, including petroleum products

like asphalt.

Since the liquid to gas expansion ratio of this substance is 1:694, a tremendous amount of

force can be generated if liquid nitrogen is rapidly vaporized. In an incident in 2006 at Texas

A&M University, the pressure-relief devices of a tank of liquid nitrogen were sealed with

brass plugs. As a result, the tank failed catastrophically, and exploded.

Tanks

The tanks must be designed to safety standards appropriate for a pressure vessel, such as ISO

11439.

The storage tank may be made of:

steel

aluminium

carbon fiber

Kevlar

other materials, or combinations of the above.

The fiber materials are considerably lighter than metals but generally more expensive. Metal

tanks can withstand a large number of pressure cycles, but must be checked for corrosion

periodically. Liquid nitrogen, LN2, is commonly transported in insulated tanks, up to 50 litres,

at atmospheric pressure. These tanks, being non-pressure tanks they are not subject to

inspection. Very large tanks for LN2 are sometimes pressurized to less than 25 psi to aid in

transferring the liquid at point of use.

Emission output

Like other non-combustion energy storage technologies, a liquid nitrogen vehicle displaces

the emission source from the vehicle's tail pipe to the central electrical generating plant.

Where emissions-free sources are available, net production of pollutants can be reduced.

Emission control measures at a central generating plant may be more effective and less

costly than treating the emissions of widely dispersed vehicles.

Advantages

Liquid nitrogen vehicles are comparable in many ways to electric vehicles, but use liquid

nitrogen to store the energy instead of batteries. Their potential advantages over other

vehicles include:

Much like electrical vehicles, liquid nitrogen vehicles would ultimately be powered

through the electrical grid, which makes it easier to focus on reducing pollution from one

source, as opposed to the millions of vehicles on the road.

Transportation of the fuel would not be required due to drawing power off the

electrical grid. This presents significant cost benefits. Pollution created during fuel

transportation would be eliminated.

Lower maintenance costs

Liquid nitrogen tanks can be disposed of or recycled with less pollution than

batteries.

current battery systems. Liquid nitrogen vehicles are unconstrained by the

degradation problems associated with

The tank may be able to be refilled more often and in less time than batteries can be

recharged, with re-fueling rates comparable to liquid fuels.

It can work as part of a combined cycle powertrain in conjunction with a petrol or

diesel engine, using the waste heat from one to run the other in

a turbocompound system. It can even run as a hybrid system.

Disadvantages

The principal disadvantage is the inefficient use of primary energy. Energy is used to liquefy nitrogen, which in turn provides the energy to run the motor. Any conversion of energy has losses. For liquid nitrogen cars, electrical energy is lost during the liquefaction process of nitrogen.

Liquid nitrogen is not available in public refueling stations; however, there are distribution

systems in place at most welding gas suppliers and liquid nitrogen is an abundant by-

product of liquid oxygen production.

A New Car Engine

Despite shifting into higher gear within the consumer's green conscience, hybrid vehicles are

still tethered to the gas pump via a fuel-thirsty 100-year-old invention: the internal

combustion engine.

However, researchers at Michigan State University have built a prototype gasoline engine

that requires no transmission, crankshaft, pistons, valves, fuel compression, cooling systems

or fluids. Their so-called Wave Disk Generator could greatly improve the efficiency of gas-

electric hybrid automobiles and potentially decrease auto emissions up to 90 percent when

compared with conventional combustion engines.

The engine has a rotor that's equipped with wave-like channels that trap and mix oxygen

and fuel as the rotor spins. These central inlets are blocked off, building pressure within the

chamber, causing a shock wave that ignites the compressed air and fuel to transmit energy.

The Wave Disk Generator uses 60 percent of its fuel for propulsion; standard car engines

use just 15 percent. As a result, the generator is 3.5 times more fuel efficient than typical

combustion engines.

Researchers estimate the new model could shave almost 1,000 pounds off a car's weight

currently taken up by conventional engine systems.

DUMSG then considered alternate fuels Liquid Petroleum Gas (LPG)

Liquid Petroleum Gas (LPG) is a blend of propane and butane, produced either as a by-

product of oil-refining, or from natural gas (methane) fields. As an alternative fuel it is most

suited to use in cars and light vans, rather than heavy vehicles. More information on LPG

from the LP Gas Association.

Electric vehicles

EV vehicles are starting become a real alternative to the internal combustion engine. Zero

exhaust fumes, and silent! – this technology could transform our cities.

Biogas

Biogas is derived from rotting municipal waste, food waste or sewage (both human and

animal). This is turned into gas by means of “anaerobic conversion” in a digester. Organic

matter such as switchgrass can be grown specifically for biogas production. According to the

Energy Saving Trust Sweden has “the largest fleet of biogas-fuelled vehicles in the world,

with around 7,000 vehicles in the country and plans to increase this number to 80,000 by

2010.” In the UK, the number of refuelling stations linked to the HGV industry is increasing.

Biodiesel / vegetable oil

When Mr Diesel first designed his engine, petrochemical diesel wasn’t even available. So it’s

no surprise that modern diesel engines can run on alternative fuels.

One option is biodiesel, which is vegetable oil, processed to make it run in standard diesel

engines, which has many advanatages:

Vegetable oil is ‘carbon neutral’, because the carbon dioxide produced when the fuel

burns was absorbed when the plants were growing.

Engines using biodiesel are said to run smoother and last longer.

Most biodiesels can be used mixed with ordinary diesel – there’s no need for a

separate tank. Pure Biodiesel who supply 100% biodiesel in the Stround area provide

more information.

Biodiesel fuels are available now from fuel stations throughout the UK. All brands on

offer can be used in any diesel engine, and contain anything from 5% to 100% biodiesel.

Goldenfuels is a waste-oil biofuel company based in Oxford, who can supply more

information.

However, there are environmental costs in growing oilseed rape (possibly genetically

modified) or other plants for biofuels. These could outweigh some of the benefits. In

particular, the amount of land required to produce enough biodiesel to replace current fuel

use, assuming current levels of mileage, is enormous. It would not be feasible to use so

much land for biodiesel. It would also mean using land that is needed to grow food for

people or destroying wildlife habitats. Reusing old oil, e.g. from fish and chip shops, is a

possibility.

For the more adventurous: straight vegetable oil can be used as fuel instead, but in this

case the engine itself may need to be modified. It is possible to reuse old oil e.g. from fish

and chip shops.

Bioethanol

Bioethanol is derived from starches or sugar, for example corn or sugar cane, by

fermentation and distillation. A blend of 5% bioethanol with 95% petrol can be used in all

petrol engines and reduces carbon dioxide emissions by 3.5%. Petrol engines can be

modified to run on up to 85% bioethanol. Car manufacturers are beginning to produce

vehicles that can run on all blends up to 85% and the availability of bioethanol in the UK

looks set to increase. In Brazil 60% of new cars sold are 100% ethanol fuelled and it is the

world’s largest producer of bioethanol, with 45% of all fuel used in cars there being

bioethanol. An electric car is an automobile that is propelled by one electric motor or more,

using electrical energy stored in batteries or another energy storage device. Electric motors

give electric cars instant torque, creating strong and smooth acceleration.

The first electric cars appeared in the 1880s.[1] Electric cars were popular in the late 19th

century and early 20th century, until advances in internal combustion engine technology

and mass production of cheaper gasoline vehicles led to a decline in the use of electric drive

vehicles. The energy crises of the 1970s and 1980s brought a short-lived interest in electric

cars; although, those cars did not reach the mass marketing stage, as is the case in the 21st

century. Since 2008, a renaissance in electric vehicle manufacturing has occurred due to

advances in battery and power management technologies, concerns about increasing oil

prices, and the need to reduce greenhouse gas emissions.[2][3] Several national and local

governments have established tax credits, subsidies, and other incentives to promote the

introduction and adoption in the mass market of new electric vehicles depending on battery

size and their all-electric range.

Electric Cars

Benefits of electric cars over conventional internal combustion engine automobiles include a

significant reduction of local air pollution. A large reduction in total greenhouse gas and other

emissions (dependent on the fuel and technology used for electricity generation),

Terminology

Electric cars are a variety of electric vehicle (EV). The term "electric vehicle" refers to any

vehicle that uses electric motors for propulsion, while "electric car" generally refers to

highway-capable automobiles powered by electricity. Low-speed vehicles electric vehicles,

classified as neighborhood electric vehicles (NEVs) in the United States,[10] and as

electric motorised quadricycles in Europe,[11] are plug-in electric-powered microcars or city

cars with limitations in terms of weight, power and maximum speed that are allowed to travel

on public roads and city streets up to a certain posted speed limit, which varies by country.

While an electric car's power source is not explicitly an on-board battery, electric cars with

motors powered by other energy sources are generally referred to by a different name: an

electric car powered by sunlight is a solar car, and an electric car powered by a gasoline

generator is a form of hybrid car. Thus, an electric car that derives its power from an on-

board battery pack is a form of battery electric vehicle (BEV). Most often, the term "electric

car" is used to refer to battery electric vehicles.

Comparison with internal combustion engine vehicles

An important goal for electric vehicles is overcoming the disparity between their costs of

development, production, and operation, with respect to those of equivalent internal combustion

engine vehicles (ICEVs). As of 2013, electric cars are significantly more expensive than

conventional internal combustion engine vehicles and hybrid electric vehicles due to the

additional cost of their lithium-ion battery pack. However, battery prices are coming down with

mass production and are expected to drop further. Electric cars have several benefits over

conventional internal combustion engine automobiles, including a significant reduction of local air

pollution, as they have no tailpipe, and therefore do not emit harmful tailpipe pollutants from the

onboard source of power at the point of operation reduced greenhouse gas emissions from the

onboard source of power, depending on the fuel and technology used for electricity generation to

charge the batteries. Electric vehicles generally, compared to gasoline vehicles show significant

reductions in overall well-wheel global carbon emissions due to the highly carbon intensive

production in mining, pumping, refining, transportation and the efficiencies obtained with gasoline

Price

The up-front purchase price of electric cars is significantly higher than conventional internal

combustion engine cars, even after considering government incentives for plug-in electric

vehicles available in several countries. The primary reason is the high cost of car batteries.

Maintenance

Electric cars have expensive batteries that must be replaced but otherwise incur very low

maintenance costs, particularly in the case of current lithium-based designs.

Running costs

The cost of charging the battery depends on the price paid per kWh of electricity - which varies

with location.

The EV1 energy use was about 11 kW·h/100 km (0.40 MJ/km; 0.18 kW·h/mi) The

2011/12 Nissan Leaf uses 21.25 kW·h/100 km (0.765 MJ/km; 0.3420 kW·h/mi) according to

the US Environmental Protection Agency These differences reflect the different design and

utility targets for the vehicles, and the varying testing standards. The energy use greatly

depends on the driving conditions and driving style. Nissan estimates that the Leaf's 5-year

operating cost will be US$1,800 versus US$6,000 for a gasoline car in the USA According to

Nissan, the operating cost of the Leaf in the UK is 1.75 pence per mile (1.09p per km) when

charging at an off-peak electricity rate, while a conventional petrol-powered car costs more

than 10 pence per mile (6.25p per km). These estimates are based on a national average of

British Petrol Economy 7 rates as of January 2012, and assumed 7 hours of charging

overnight at the night rate and one hour in the daytime charged at the Tier-2 daytime rate.

Range and recharging time

Most cars with internal combustion engines can be considered to have indefinite range, as

they can be refueled very quickly. Electric cars often have less maximum range on one

charge than cars powered by fossil fuels, and they can take considerable time to recharge.

However, they can be charged at home overnight, which fossil fueled cars cannot. The

average American drives less than 40 miles (64 km) per day; so the GM EV1 would have

been adequate for the daily driving needs of about 90% of U.S. consumers. Nevertheless,

people can be concerned that they would run out of energy from their battery before

reaching their destination, a worry known as range anxiety.

The Tesla Roadster can travel 245 miles (394 km) per charge;] more than double that of

prototypes and evaluation fleet cars currently on the roads The Roadster can be fully

recharged in about 3.5 hours from a 220-volt, 70-amp outlet which can be installed in a

hom But using a European standard 220-volt, 16-amp outlet a full charge will take more than

15 hours.

However, most vehicles also support much faster charging, where a suitable power supply is

available. Therefore for long distance travel, in the US and elsewhere, there has been the

installation of DC Fast Charging stations with high-speed charging capability from three-

phase industrial outlets so that consumers could recharge the 100-200+ mile battery of their

electric vehicle to 80 percent in about 30 minutes

Transmission

A gearless or single gear design in some EVs eliminates the need for gear shifting, giving

such vehicles both smoother acceleration and smoother braking. Because the torque of an

electric motor is a function of current, not rotational speed, electric vehicles have a high

torque over a larger range of speeds during acceleration, as compared to an internal

combustion engine. As there is no delay in developing torque in an EV, EV drivers report

generally high satisfaction with acceleration.

Risk of fire

Lithium-ion batteries may suffer thermal runaway and cell rupture if overheated or

overcharged, and in extreme cases this can lead to combustion.[] Several plug-in electric

vehicle fire incidents have taken place since the introduction of mass-production plug-in

electric vehicles in 2008. Most of them have been thermal runaway incidents related to their

lithium-ion battery packs.

Vehicle safety

Great effort is taken to keep the mass of an electric vehicle as low as possible to improve its

range and endurance. However, the weight and bulk of the batteries themselves usually makes

an EV heavier than a comparable gasoline vehicle, reducing range and leading to longer braking

distances.

At low speeds, electric cars produced less roadway noise as compared to vehicles propelled

by internal combustion engines. Blind people or the visually impaired consider the noise of

combustion engines a helpful aid while crossing streets, hence electric cars

and hybrids could pose an unexpected hazard.

Batteries

Prototypes of 75 watt-hour/kilogramlithium-ion polymer battery. Newer lithium-ion cells can

provide up to 130 W·h/kg and last through thousands of charging cycles.

Finding the economic balance of range against performance, energy density, and

accumulator type versus cost challenges every EV manufacturer.

While most current highway-speed electric vehicle designs focus on lithium-ion and other

lithium-based variants a variety of alternative batteries can also be used. Lithium based

batteries are often chosen for their high power and energy density but have a limited shelf-

life and cycle lifetime which can significantly increase the running costs of the vehicle.

Variants such as Lithium iron phosphate and Lithium-titanate attempt to solve the durability

issues with traditional lithium-ion batteries.

Other battery technologies include:

Lead acid batteries are still the most used form of power for most of the electric

vehicles used today. The initial construction costs are significantly lower than for other

battery types, and while power output to weight is poorer than other designs, range and

power can be easily added by increasing the number of batteries.[194]

NiCd - Largely superseded by NiMH

Nickel metal hydride (NiMH)

Nickel iron battery - Known for its comparatively long lifetime and low power density

Several battery technologies are also in development such as:

Zinc-air battery

Molten salt battery

Zinc-bromine flow batteries or Vanadium redox batteries can be refilled, instead of

recharged, saving time. The depleted electrolyte can be recharged at the point of

exchange, or taken away to a remote station.

Compressed air car

A compressed air car is a car that uses a motor powered by compressed air. The car can

be powered solely by air, or combined (as in a hybrid electric vehicle)

with gasoline,diesel, ethanol, or an electric plant with regenerative braking.

Technology[ Engines

Compressed air cars are powered by motors driven by compressed air, which is stored in

a tank at high pressure such as 30 MPa (4500 psi or 310 bar). Rather than driving engine pistons

with an ignited fuel-air mixture, compressed air cars use the expansion of compressed air, in a

similar manner to the expansion of steam in a steam engine.

Storage tanks

In contrast to hydrogen's issues of damage and danger involved in high-impact crashes, air,

on its own, is non-flammable. It was reported on Seven Network's Beyond Tomorrow that on

its own carbon-fiber is brittle and can split under sufficient stress, but creates

no shrapnel when it does so. Carbon-fiber tanks safely hold air at a pressure somewhere

around 4500 psi, making them comparable to steel tanks. The cars are designed to be filled

up at a high-pressure pump.

Energy density

Compressed air has relatively low energy density. Air at 30 MPa (4,500 psi) contains about

50 Wh of energy per liter (and normally weighs 372g per liter). For comparison, a lead–acid

battery contains 60-75 Wh/l. Alithium-ion battery contains about 250-620 Wh/l.

Gasoline contains about 9411 Wh per liter;[1] however, a typical gasoline engine with 18%

efficiency can only recover the equivalent of 1694 Wh/l. The energy density of a compressed

air system can be more than doubled if the air is heated prior to expansion.

In order to increase energy density, some systems may use gases that can be liquified or

solidified. "CO2 offers far greater compressibility than air when it transitions from gaseous to

supercritical form.

Emissions

Compressed air cars are emission-free at the exhaust. Since a compressed air car's source

of energy is usually electricity, its total environmental impact depends on how clean the

source of this electricity is. Different regions can have very different sources of power,

ranging from high-emission power sources such as coal to zero-emission power sources

such as wind. A given region can also change its electrical power sources over time, thereby

improving or worsening total emissions.

However a study showed that even with very optimistic assumptions, air storage of energy is

less efficient than chemical (battery) storage.

Advantages

The principal advantages of an air powered

It uses no gasoline or other bio-carbon based fuel.

Refueling may be done at home,[4] but filling the tanks to full pressure would require

compressors for 250-300 bars, which are not normally available for home standard

utilization, considering the danger inherent at these pressure levels. As with gasoline,

service stations will eventually have the necessary air facilities. Those will use energy

produced at large centralized powerplants, potentially making it less costly and more

effective to manage emissions than from individual vehicles.

Compressed air engines reduce the cost of vehicle production, because there is no

need to build a cooling system, spark plugs, starter motor, or mufflers.[5]

The rate of self-discharge is very low opposed to batteries that deplete their charge

slowly over time. Therefore, the vehicle may be left unused for longer periods of time

than electric cars.

Expansion of the compressed air lowers its temperature; this may be exploited for

use as air conditioning.

Reduction or elimination of hazardous chemicals such as gasoline or battery

acids/metals

Some mechanical configurations may allow energy recovery during braking by

compressing and storing air.

Sweden’s Lund University reports that buses could see an improvement in fuel

efficiency of up to 60 percent using an air-hybrid system[6] But this only refers to hybrid

air concepts (due to recuperation of energy during braking), not compressed air-only

vehicles.

Disadvantages

The principal disadvantages are the additional steps of energy conversion and transmission,

because each inherently has loss. For combustion engine cars, the energy is lost when

chemical energy in fossil fuels are converted by the engine to mechanical energy. For

electric cars, a power plant's electricity (from whatever source) is transmitted to the car's

batteries, which then transmits the electricity to the car's motor, which converts it to

mechanical energy. For compressed-air cars, the power plant's electricity is transmitted to a

compressor, which mechanically compresses the air into the car's tank. The car's engine

then converts the compressed air to mechanical energy.

Additional concerns:

When air expands in the engine it cools dramatically and must be heated to ambient

temperature using a heat exchanger. The heating is necessary in order to obtain a

significant fraction of the theoretical energy output. The heat exchanger can be

problematic: while it performs a similar task to an intercooler for an internal combustion

engine, the temperature difference between the incoming air and the working gas is

smaller. In heating the stored air, the device gets very cold and may ice up in cool, moist

climates.

This also leads to the necessity of completely dehydrating the compressed air. If any

humidity subsists in the compressed air, the engine will stop due to inner icing.

Removing the humidity completely requires additional energy that cannot be reused and

is lost. (At 10g of water per m3 air -typical value in the summer- you have to take out 900

g of water in 90 m3; with a vaporization enthalpy of 2.26MJ/kg you will need theoretically

minimally 0.6 kWh; technically, with cold drying this figure must be multiplied by 3 - 4.

Moreover, dehydrating can only be done with professional compressors, so that a home

charging will completely be impossible, or at least not at any reasonable cost.)

Conversely, when air is compressed to fill the tank, its temperature increases up. If

the stored air is not cooled while the tank is being filled, then when the air cools off later,

its pressure decreases and the available energy decreases.

To mitigate this, the tank may be equipped with an internal heat-exchanger in order to

cool the air quickly and efficiently while charging.

Alternatively, a spring may be used to store work from the air as it is inserted in the tank,

thus maintaining a low pressure difference between the tank and recharger, which

results in a lower temperature raise for the transferred air.[citation needed]

Refueling the compressed air container using a home or low-end conventional air

compressor may take as long as 4 hours, though specialized equipment at service

stations may fill the tanks in only 3 minutesTo store 2.5 kWh @300 bar in 300 liter

reservoirs (90 m3 of air @ 1 bar), requires about 30 kWh of compressor energy (with a

single-stage adiabatic compressor), or approx. 21 kWh with an industrial standard

multistage unit. That means a compressor power of 360 kW is needed to fill the

reservoirs in 5 minutes from a single stage unit, or 250 kW for a multistage

one.[7] However, intercooling and isothermal compression is far more efficient and more

practical than adiabatic compression, if sufficiently large heat exchangers are fitted.

Efficiencies of up to 65% might perhaps be achieved,] (whereas current efficiency for

large industrial compressors is max. 50% )however this is lower than the Coulomb's

efficiency with lead acid batteries.

The overall efficiency of a vehicle using compressed air energy storage, using the

above refueling figures, is around 5-7%. For comparison, well to wheel efficiency of a

conventional internal-combustion drivetrain is about 14%,

Early tests have demonstrated the limited storage capacity of the tanks; the only

published test of a vehicle running on compressed air alone was limited to a range of

7.22 km

A 2005 study demonstrated that cars running on lithium-ion batteries out-perform

both compressed air and fuel cell vehicles more than threefold at the same speeds

MDI claimed in 2007 that an air car will be able to travel 140 km in urban driving, and

have a range of 80 km with a top speed of 110 km/h (68 mph) on highways when

operating on compressed air alone, but in as late as mid-2011, MDI has still not

produced any working prototype.

A 2009 University of Berkeley Research Letter found that "Even under highly

optimistic assumptions the compressed-air car is significantly less efficient than a battery

electric vehicle and produces more greenhouse gas emissions than a conventional gas-

powered car with a coal intensive power mix." However, they also suggested, "a

pneumatic–combustion hybrid is technologically feasible, inexpensive and could

eventually compete with hybrid electric vehicles.]

After considering different Engines and Fuels, we considered alternatives to the car itself.

Electric bicycles were discussed.

Electric bicycle wheels are coming to the masses, and they are coming from multiple

sources. A few years ago we saw the Copenhagen Wheel, and now a similar product

is making its way to market – the FlyKly Smart Wheel.

The Smart Wheel is designed to work on almost any bicycle. The 250W electric

motor automatically kicks in when the user starts pedaling, and it stops when the

user does. As is the case with conventional electric bikes, this allows riders to pedal

with less effort.

The motor allows for a top speed of 20 mph (32 km/h) with a 30-mile (48-km) range.

The whole wheel weighs in at 9 lb (4 kg), and will be available in 20, 26, and 29-inch

sizes.

Aside from the actual motor, the wheel also comes with a mobile application that

offers features like the ability to lock the motor, track it in the event that it is stolen,

and set the top speed while riding.

How an electric bike works

Allows the rider to add power to their pedalling with a small electric motor

Most have lithium batteries with a range of 20 to 25 miles (32 to 40km)

Power-assisted speed limit of 15mph (25km/h) in the UK, but - as with standard bikes - can exceed that when under pedal power alone

Some models have power-assisted pedalling

Others have a throttle and/or a handlebar-mounted control panel and let the motor take most of the strain

Electric bikes come in many shapes and sizes, with prices starting at about £500 and rising to £2,000 or more.

You have to be pedalling for the motor to run and, by law, it cuts out at 15 mph (25km/h). Getting the heavier models to go much faster is not easy, but in a city that's a perfectly reasonable speed - although it can mean the more traditional cyclists left at the lights quickly catch up on the flat.

There's no licence to worry about, no insurance, and instead of trips to the petrol pump, the battery - which lasts for about 20 miles - is charged from a power socket.

So why do electric bikes remain something of a novelty?

Among those who will not be buying one in a hurry is Cycling Plus editor Rob Spedding, a self-confessed middle-aged man in lycra. For enthusiasts like him, the point is pedalling hard and getting fit.

Inventor Clive Sinclair devised the C5 from 1985, and a powered bike in 1994

But Spedding says that to judge electric bikes on these terms alone is wrong.

"It's a really good entry point into cycling," he says.

As electric bikes still have to be pedalled, an element of exercise is unavoidable - even if hills are less daunting, says Spedding. And encouraging more people onto bikes of whatever kind reduces pollution and congestion on the roads.

"Seniors with e-bikes have been dealing with falling a lot, misjudging the speed and so on."

Courses are now being offered to help older riders cycle safely, including speed awareness and how to deal with junctions.It is the kind of enthusiasm seen in the Netherlands that London Mayor Boris Johnson has been trying to tap into.