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.