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Transport fuel in the future - Hydrogen fuel cells and electricity.
With oil reserves only sufficient for possibly 30 years practical alternatives must be developed and introduced.
If oil is to be eliminated as a primary fuel (in addition to gas and coal), the choice for future transport fuels will be obtained mainly via electricity and/or hydrogen (both secondary sources). Bio fuels will also play a part with the disadvantage that those obtained from crops also produce some CO2 (see green page) and use up land otherwise available for food and forest (the latter which is needed to take CO2 out of the atmosphere.)
Hydrogen can be burned in an internal combustion engine producing only water vapor and no other byproducts. The long term solutions to transport however is likely to be the development of a system for electric cars using rechargeable batteries followed by or supplemented by suitable fuel cells to generate electrical energy, using hydrogen as the fuel to supply the fuel cells (see hydrogen page). Hydrogen cars are available now, waiting for an infrastructure to enable long distance travel. The Chevrolet Equinox has a range of 150 miles in California, release date 2011 probably, powered by Hydrogen fuel cell/ electric motor.
Battery powered cars with battery change infrastructure in a few years.
A revolution to extend the use of battery cars is just around the corner and we should see these in two or so years powered by Lithium-ion batteries, giving a range of between 100km and 160 km (60 to 100m), rechargeable via the mains. Features will be:- A '5 minute' battery switch scheme set up around the country to extend range beyond100 miles; extensive recharging facilities, at restaurants, pubs, car parks, garages etc; and recharging preferably at night on a low rate.
Batteries may have to be replaced/traded in regularly, eg every two years and recharging time will be an important feature. Dyson suggests recharging also from on board solar photovoltaics
Battery cars will have to be relatively lightweight and optimum range will be an important feature, traded with cost and weight of battery.
' Project Better Place' plan such a scheme with the introduction of battery cars in 2011 into Israel (at equivalent capital cost due to tax incentive and much lower running costs.) Where mains electricity is obtained from solar (ie in Israel) wind or nuclear sources the solution would be 'carbon free.'
The UK and Denmark also plan such a scheme by 2011. Cost of fuel claimed to be £1 a mile, a third of petrol version.
Lithium Titanate oxide batteries are being developed that could extend the vehicle range to 200 miles, enable recharging in a few minutes with a projected life of up to 20 years.
Lithium carbonate is currently mined mostly in Brazil, Argentina and Bolivia.
Plug in rechargeable hybrid petrol-diesel/ battery cars
Battery cars with on board petrol or diesel engine top up charger (ie where the engine doesn't assist in the drive - unlike current hybrid cars - ref 174) will extend the range. Current hybrids will run up to 50 miles in battery mode, before the need for engine to cut in, which will enable cheap consumption for short journeys of 20-25 miles that most people make most of the time. Today's hybrid.
Compressed air drive for vehicles, fueled from electric driven compressors.
Alternatives to battery cars are cars driven by a compressed air piston engine, cylinders carried underneath the car. These are being developed in India. The 3 seater 'OneCAT' has a claimed range of 120 to 180 miles (200 to 300 km) weight 770 lbs (350 kg) low servicing and cost, speed up to 70 mph.
A compressed air car has probably 1/3 the efficiency of a battery car. With energy from a local wind or other green source however, where CO2 emission was not an overall worry, reliability and cost would be the main considerations. 300 L of air at 300 bar has the same energy ( 14 kw hr) as 5.4 litres (1.2 galls) petrol.
Efficiency of systems compared (Higher efficiency =less CO2 emitted)
Comparison Electric with Petrol (Gas)car from fossil fuel.
Fuel >> electricity 35% >>charger 90% >> battery 90% >> electric/motor 80% =23%
Fuel >> Petrol engine 16% Diesel engine 20% (normal driving - variable speed.)
Thus a Battery car involves slightly less CO2 emissions than a Petrol car; but if electrical generation is green, substantially less.
Efficiency using a fuel cell hydrogen car generated from fossil fuel source is 6 to 10%
See page on decreasing fuel consumption by economical driving 33%
Comparison of Hydrogen Fuel cell with Battery - Electric car using energy from heat or electric sources assuming non CO2 or green generation of energy.
Battery - Electric cars
Heat >> electricity 35% >>charger 90% >> battery 90% >> electric /motor 80% = 23%
Photo voltaic cell electricity >> charger 90% >> battery 90% >> motor 80% =65%
Hydrogen - Fuel Cell cars.
Heat >> H2(electrolysis)25% >> fuel cell 75% >> electricity/motor >>power 80% =15%
Heat >>H2(electrolysis/thermo chem)45% >> fuel cell 75% >> electric/motor 80% = 27%
Where the original fuel is non CO2 producing the determining factors between fuel cell and battery will be cost, infrastructure, convenience, recharging time and safety.
Report on efficiencies of air and battery cars.
Bio fuel an interim replacement but limited due to land pressure.
Bio fuel will have limited use long term where growing it requires land, which is therefore not available for crops, or forest, which would otherwise help reconvert CO2 back to Oxygen. Brazil has made extensive use of bio fuel as a green alternative to petrol/diesel. In the short term (next 50 years) Bio fuels will be useful while alternatives are introduced. See bio page.
Ineous chemicals claim that they can make 400 litres (90 gallons) ethanol from one tonne of dry waste, heating waste to produce gas, feeding the gas to bacteria which produce ethanol which can then be purified.
Trains - electric and diesel replaced coal in trains and in the future, Maglevs.
From the outset, coal was the fuel used for steam engines but train travel has for many years lent itself to electrification enabling power to be drawn from the more efficient electrical grid systems. Diesel electric first replaced steam on main lines and diesel locos in smaller applications.
In the future very fast intercity trains, say up to 300 mph or 500 km per hour, may take the form of the train suspended magnetically on a cushion of air and propelled by linear induction motors (electrical power), so eliminating friction, an example being the Maglev project. These could eliminate intercity flights, although the 'rail network' will be expensive. Japan plan to extend the maglev line and eventually offer a Tokyo - Osaka service.
An idea for a future intercity train is to run it in a tunnel which falls 1 to 3% per 10 km -a depth of up to 180 m and then rises using the kinetic energy. The train would be supported on PM magnetic levitation to reduce friction and would have battery assistance recharged by wind and no external power source. The tunnels would be 2 way with many interconnecting passages to enable low resistance air flow. (ref 172)
Comparison of CO2 emissions for travel 2007 (Ref 237)
Aircraft, high level emission problem as well as the CO2 problem.
Boeing have said that it is unlikely that fuel cells would ever provide primary power for large passenger aircraft, while demonstrating that it is possible for very light aircraft. Thus the future for all but small aircraft lies in reducing CO2 by economy and bio fuels.
At present fuel prices, air travel cost is low between major cities and countries while private jets are attractive for the very wealthy for time saving and convenience.
In addition to the contribution to CO2 emissions it has been suggested that the emissions of aircraft at high level cause a haze around the globe which, unlike emissions at low level (due to cars, heating, power stations etc) do not disperse, and therefore cause an additional and serious greenhouse effect (ref 153).
Bio fuels possible for air.
The problem is being tackled in several ways. First the development of bio fuels which must stand the low temperatures in aircraft. Secondly by improvements in efficiency.
Size or long haul?
The Airbus approach is to increase the size so that up to 800 passengers can be transported at one time, saving 20% fuel/CO2 per seat per mile. The approach of Boeing is more towards efficiency and range, to cut out the expensive (in cost and CO2) stops where passengers are on a long journey.
Reducing surface friction, weight and new engines to increase efficiency.
A future design idea to increase efficiency is a giant flying wing where the drag due to air friction is reduced on the wing surface by millions of tiny holes that suck in air; and the use of lighter materials such as Carbon Fibre instead of Aluminum based materials. These planes may come into service after 2025 and could reduce fuel use to 33%. Engine development may also improve efficiency by 30% and be quieter (ref 152.)
Rolls Royce suggest that overall efficiency could be improved by 50% of which 20-25% could be due to airframe improvements, 15 to 20% due to engine design and 5 to 10% due to operational refinements.
Fuel cell and Hydrogen storage for aircraft ?
An EU funded project is to develop intercity aircraft using fuel cell technology for the propulsion system and hydrogen storage (ref155.) Low noise levels are an added advantage to low emissions and could therefore allow take off and landing at night.
Ships
The shipping industry burns 4.5% of the fuel used in the world (1.2 bn tonnes CO2 per year - 0.33 bn tonnes carbon), twice that of air travel.
Coal / steam replaced sail in the 1800's and is now replaced by diesel or gas turbines. Only in very large vessels, submarines, some ice breakers and tankers are the relatively expensive nuclear reactors used which avoid or minimize CO2 emission.
