
The quality of a city depends on things such as
*) The average travel time
*) The amount of residential and yard space per person
*) The amount of public park space
Most cities are poorly designed in this regard and hence new cities may emerge that are built from scratch. These cities will take advantage of possibilities offered by electric driverless cars, prefabricated housing, and factories where you can manufacture things for yourself.
Population Population Area Travel Travel density (millions) (km^{2}) time means (people/ha) (mins) Manila 430 1.65 38.6 30 Taxi Delhi 255 11.0 431 30 Bus Paris 215 2.27 105 30 Subway Seoul 130 10.4 605 30 Subway New York City 104 8.18 784 30 Subway San Francisco 67 .81 121 30 Subway Boston 51 .65 125 30 Subway Pasadena 24 .140 59.5 10 Car Beverly Hills 23 .347 14.8 10 Car Iowa City 10 .068 64.8 10 Walk, bike Isla Vista 48 .023 4.8 5 Walk, bikeElectic cars outperform public transportation for travel time and energy use. New York City is a catastrophic case that illustrates the weaknesses of public transportation. To get anywhere you have to:
This often takes more than 30 minutes, plus the subway routes are awkwardly designed.
Consider two contrasting city designs:
Design 1) Everyone has a yard adjacent to a park and no upstairs neighbors.
The house has a garage with a electric driverless car.
Design 2) Everyone lives in skycrapers
Lawns and parks are good for social interaction, especially for families with children. Skyscrapers are poor in this regard.
Being able to drive an electric car right up to your residence dramatically reduces travel time.
A high population density can be achieved even if everyone has a yard.
For example, suppose a citizen has on average:
*) A residence of 30 square meters.
*) A yard of 20 square meters.
*) The residence is adjacent to a park with 30 square meters per person.
*) Road space of 20 square meters per person.
These residences are larger than typical New York City apartments and they achieve a respectable population density of 10000 people/km^{2}.
A city with sensible traffic flow can achieve a large population and a small travel time. For example,
City radius = R = 3 km Average travel speed = V = 15 meters/second Average travel time = T = R/V = 3.3 minutes City population density = D = 10000 people/km^{2} = 1 person every 10 meters^{2} City population = P = πDR^{2}=280000 peopleIt helps to centralize. 4 points of focus of a city are the college, the pub district, the shopping district, and the K12 school. These can be placed in the city center and the residences and businesses radiate out from the center.
Prefabricated homes can be made from shipping containers, which are abundant, cheap, and easily delivered.
$ Length Width Height Mass ft ft ft kg 10foot shipping container 1000 10 8 8.5 1300 20foot shipping container 1200 20 8 8.5 2200 40foot shipping container 1500 40 8 8.5 3800 Typical mobile home 90 18
Prefabricated houses can be helicoptered to wilderness locations and flying cars can be used to reach them.
The energy sources that can be used by vehicles are:
Energy/Mass Power/mass Energy/$ Rechargeable Charge Maximum charging MJoule/kg Watt/kg MJoule/$ time cycles Gasoline 45 60 Battery, aluminum 4.6 130 No Battery, lithium .8 1600 .010 Yes 1 hour 1000 Supercapacitor .016 8000 .00005 Yes Instant Infinite Aluminum capacitor .010 10000 .0001 Yes Instant Infinite
The energy required to move a vehicle is proportional to the drag force.
Distance traveled = X (Meters) Drag force = F (Newtons) Energy expended = E = F X (Joules)Drag consists of air drag and rolling drag, with air drag usually being larger. For various vehicles moving at a city speed of 15 meters/second the drag force is:
Drag Drag/ People person Newtons Newtons Bike 87 87 1 Car (compact) 205 205 1 Car (large) 286 286 1 Bus 800 11 72 Subway car 720 6 120 Steel rails have low rolling dragBuses and trains outperform cars but only if they're full, and they're much slower and inflexible than cars.
At a freeway speed of 30 meters/second,
Drag Drag/ People person Newtons Newtons Freeway car 904 904 1 Bus 3200 44 72 Train car 2400 20 120 Semi truck 4200 4200 1For freeways, buses use 20 times less energy/person than cars.
An airbus A380 carries 600 people and has a drag force of 1300 Newtons/person. Buses use 30 times less energy/person than an Airbus.
The properties of electric vehicles are determined by the properties of lithium batteries, which are:
Battery energy/mass = e = .8 MJoules/kg Battery power/mass = p = 1600 Watts/kg Battery energy/dollar= s = .010 MJoules/$The value for energy/dollar is likely to see substantial improvement.
The speed of a vehicle is determined by engine power and air drag. We calculate the power required for electric bikes, cars, and helicopters. For electric cars we consider a compact "city car" powerful enough for city roads but not freeways, a "freeway car" that is powerful enough for freeways, and a "sports car" that maximizes the capabilities of electric motors.
The relationship between the engine power and top speed is determined by air drag.
Air density = D = 1.22 kg/meter^{3} Drag parameter = K Speed = V Drag power = P = ½ K D V^{3}The battery size has to be at least large enough to power the motor, and the motor power is determined by the maximum speed. For various vehicles,
Max Max Drag Drag Battery Battery speed speed parameter power mass cost mph m/s kWatt kg $ Bike 45 20 .6 2.9 1.8 180 City car 55 25 1.2 11.4 7.1 710 Freeway car 85 38 1.5 58 37 3700 Sports car 180 80 1.5 470 290 29000For city cars the battery is a small fraction of the vehicle cost and for freeway cars it's the dominant cost.
The battery energy determines the range.
The power is calculated using the max speed.
Battery mass is calculated from the power using a power/mass of 1600 Watts/kg.
Energy is calculated from the battery mass using an energy/mass of .8 MJoules/kg.
The drag parameter is obtained from an analysis of commercial vehicles. Data
Range is calculated using a cruising speed of 15 m/s for cities and 30 m/s for freeways. We use the battery energies calculated above.
Cruise Drag Battery Range speed force energy m/s Newtons MJoule km Bike 15 87 1.8 21 City car 15 205 7.1 35 Freeway car 30 904 37 41City cars have plenty of range for city driving while freeway cars need to reharge often.
The larger the propeller radius the better, because the force/power ratio is proportional to radius. Also, increasing the radius decreases the tip speed, which is helpful for nice because noise scales as the tip speed to the fifth power. The only limit to propeller radius is mass. If the radius is too large then the mass is too large.
The smaller the number of propeller, the larger the propeller radius. One propeller is optimal but singlepropeller aircraft are difficult to control, and there is no failsafe if the rotor fails.
We specify a design using 2 large propellers (for power) and 2 small propellers (for stability and failsafe). The large propellers have a radius of 1.5 meters and the small propellers have a radius of 1.0 meters.
The large propellers are mounted forward and aft and the foward propeller tilts forward for horizontal flight. The small propellers are to the right and left.
We assume the total vehicle mass is 400 kg and we use the properties of propellers to calculate the power required to hover. We use a peak power that is comfortably larger than the hover power. The minimum battery mass is 1/4 the total vehicle mass.
Total aircraft mass = M = 400 kg (Includes passenger) Number of rotors = N = 2 Rotor radius = R = 1.5 meters Gravity constant = g = 9.8 meters/second^{2} Rotor force = F = Mg/N =1960 Newtons Rotor quality = q = 1.02 Air density = D = 1.22 kg/meter^{3} Rotor power = P_{r}=(qDR)^{1}F^{3/2}= 46.2 kWatts Hover power = P_{h}= N P_{r} = 92.4 kWatts Peak power = P = 150 kWatts Battery power/mass = p =1600 Watts/kg Battery energy/mass = e = .8 MJoules/kg Battery mass = m = P/p = 94 kg Battery energy = E = e m = 75 MJoules Hover time = T = E/P_{h} = 812 seconds = 14 minutesThe properties of propellers are discussed in the propeller section. The rotor tip speed is
Rotor lift/drag = Q = 5.5 Rotor tip speed = V = P Q / F = 130 m/sThe maximum horizontal speed is around 1/3 of the rotor tip speed. If we assume a horizontal speed of 40 meters/second then the range is 32 km.
For the large propellers,
Propeller radius = R = 1.5 meters Propeller mass parameter = C = 5 kg/meter^{3} Propeller mass = M = C R^{3} = 17 kgFor the motors on the large propellers,
Motor power = 60 kWatts Motor power/mass = 8 kWatts/kg Motor mass =7.5 kgThe masses of the components in kg is
2 large 1.5 meter rotors 32 2 small 1.0 meter rotors 10 2 motors fo rthe large rotors 16 2 motors for the small rotors 10 Battery 100 Cabin 50 Fuselage 50 Pilot 80 Cargo 20 Total 380
The flight time of a drone is determined by:
*) The battery energy/mass.
*) The power/mass required to hover.
*) The ratio of the battery mass to the drone mass.
Typical parameters for a drone are:
Drone mass = M = 1.0 kg Battery mass = M_{bat} = .5 kg (The battery is the most vital component) Battery energy = E = .38 MJoules Battery energy/mass= e_{bat}= E/M_{bat}= .75 MJoules/kg (Upper range for lithium batteries) Drone energy/mass = e = E/M = .38 MJoules/kg Drone power/mass = p = P/M = 60 Watts/kg (Practical minimum to hover. Independent of mass) Drone power = P = p M = 60 Watts (Power required to hover) Flight time = T = E/P = 6250 seconds = 104 minutesThe flight time in terms of component parameters is
T = (e_{bat}/p) * (M_{bat}/M)
Electric bikes are easy to make. All you have to do is replace a conventional wheel with an electric wheel and attach a battery pack. Electric wheels come in kits and you can make the battery pack yourself. Example configurations for various motor powers:
Power Max Range Motor Battery Battery speed cost cost energy kWatt mph miles $ $ MJoule .75 30 10 160 40 .5 1.5 35 20 240 60 1.2 3 45 40 570 100 1.8 6 55 80 1150 200 3.6The bikes have one electric wheel and one conventional wheel except for 6 kWatt bike, which has 2 electric wheels with 3 kWatt each.
Electric wheel prices are from Amazon.com.
Speed Power License mph kWatt required? Connecticut 30 1.5 Yes California 28 .75 No Massachusetts 25 .75 Yes Oregon 20 1.0 No Washington 20 1.0 No Pennsylvania 20 .75 No Delaware 20 .75 No Maryland 20 .5 No DC 20 ? No
The properties of the best commercial lithium ion batteries are:
Energy/Mass = .8 Joule/kg Power/Mass = 1.6 kWatt/kg Energy/$ = .01 MJoule/kg Density = 3.5 gram/cm^{3} Recharges =1000 Shelf life = 1.0 year Voltage = 3.7 Volt Max temperature = 60 Celsius Min temperature = 20 CelsiusEnergy/Mass and Power/Mass are an engineering tradeoff. One can be increased at the expense of the other.
Energies and powers are for lithium batteries, which have a voltage of 3.7 Volts. The "ID #" is often used instead of cell size.
Cell Energy Power Current Mass Diameter Length Charge Price ID # size kJoule Watt Ampere gram mm mm AmpHour $ D 107 220 60 138 32 67 8.0 13 32650 C 67 220 60 92 26 50 5.0 8 26650, 25500 B 58 160 45 72 22 60 4.5 5 21700, 20700 A 47 110 30 49 18 50 3.5 3 18650 AA 9 22 6 15 14 53 .70 1 14500 AAA 4.7 11 3 7.6 10 44 .35 .5 10440 AAAA 2.3 6 1.5 3.8 8 42 .17 .25 75400
A single battery is a "cell" and a set of cells is a "pack". Packs are used to multiply the energy and power of cells.
Battery packs are notorous for catching fire, but cell technology has reached the point where it's now possible to make safe battery packs, and the design is simple enough so that anyone can construct their own packs.
Cells can be combined in series and/or parallel. Connecting in series multiples voltage, and voltage is helpful for achieving high power in a motor.
Connecting in series is easier than in parallel. If it's possible to achieve the required power without parallelization then one should do so, and this is usually possible with modern cells.
Series packs have the advantage that the cells can easily be extracted and charged individually, and cells can be interchanged between packs. One can also construct a set of series packs and swap them in like gun clips.
High power electric bikes use a voltage of 72 Volts. If we use one series array of C cells then a pack provides 4440 Watts and 1.2 MJoules. Any electric device requiring less than this much power can be powered by a series pack.
The properties of a modern highpower cell are:
Type = "C" Voltage = 3.7 Volts Energy = 60 kJoules Power = 155 Watts Mass = 92 grams Energy/mass = 650 kJoules/kg Power/mass =1680 Watts/kg Current = 42 Amperes Manufacturer = "Basen"When the cells are connected in series the values for voltage and power are:
Cells Voltage Power Volts kWatts 1 3.7 .15 2 7.4 .30 3 11 .45 Electric kick scooter 4 15 .60 6 24 .90 Electric bike 10 36 1.5 20 72 3.0 Compact electric car 96 356 15.0 Large electric car
Electric bike motors use either 36, 48, or 72 Volts. The following table shows how to build a battery pack for each motor power.
Power Volts Cells Series Parallel Current Cell Cell Cell Cell Cell kWatt Amperes Amperes Amphours $ type ID# .5 36 10 .75 36 10 10 1 21 25 2.1 4 A LG HD4 1.5 48 13 13 1 31 30 2.0 4.5 A Sony VTC4 3 72 20 20 1 42 60 4.5 4.5 C Basen 6 72 40 20 2 83 120 4.5 4.5 C Basen 12 72 80 20 3 167 180 4.5 4.5 C Basen Cells Total number of cells, equal to the number of cells connected in series times the number of cells connected in parallel. Series Number of cells connected in series. For example, 20 batteries with 3.6 volts each connected in series produces a voltage of 72 Volts. Parallel Number of cells connected in parallel. Current Current required to provide given power Cell Maximum current of a cell
We give thanks to Starbucks, which makes cities better. Starbucks provided a comfortable environment for the writing of this paper. Special thanks to Ro and Denise of Starbucks of Broadway and 114th.
An electric aircraft uses 7 times more energy than an electric car in terms of energy/distance/mass. Electric aircraft have a cruising speed of order 50 m/s.
Typical values for electric cars and aircraft are:
Electric aircraft speed = 50 m/s Electric aircraft power/mass = 50 Watts/kg Electric aircraft energy/distance/mass= e_{air}= 1.0 Joules/m/kg Electric aircraft flying time = T =3600 seconds Electric aircraft range = X = 180 km Gravity constant = g = 9.8 m/s^{2} Electric car mass = M Electric car rolling drag coefficient = C_{r} = .0075 Electric car rolling drag = F_{r} = C_{r} M g Electric car total drag = F = 2 F_{r} (Assume rolling drag = air drag) Electric car energy/distance/mass = e_{car}= 2 C_{r} g = .147 Joules/m/kg Aircraft energy / Car energy = e_{air} / e_{car} = 6.8
The drag force on an object moving through a fluid is
Velocity = V Fluid density = D = 1.22 kg/m^{2} (Air at sea level) Crosssectional area = A Drag coefficient = C Drag force = F = ½ C A D V^{2} Drag power = P = ½ C A D V^{3} = F V Drag parameter = K = C A"Terminal velocity" occurs when the drag force equals the gravitational force.
M g = ½ C D A V^{2}Suppose we want to estimate the parachute size required for a soft landing. Let a "soft landing" be the speed reached if you jump from a height of 2 meters, which is V_{t} = 6 m/s. If a skydiver has a mass of 100 kg then the area of the parachute required for this velocity is 46 meters^{2}, which corresponds to a parachute radius of 3.8 meters.
Drag coefficient Bicycle car .076 Velomobile Tesla Model 3 .21 2017 Toyota Prius .24 2016 Bullet .30 Typical car .33 Cars range from 1/4 to 1/2 Sphere .47 Typical truck .6 Formula1 car .9 The drag coeffient is high to give it downforce Bicycle + rider 1.0 Skier 1.0 Wire 1.2
Force of the wheel normal to ground = F_{normal} Rolling friction coefficient = C_{roll} Rolling friction force = F_{roll} = C_{roll} F_{normal }Typical car tires have a rolling drag coefficient of .01 and specialized tires can achieve lower values.
C_{roll} Railroad .00035 Steel wheels on steel rails Steel ball bearings on steel .00125 Racing bicycle tires .0025 8 bars of pressure Typical bicycle tires .004 18wheeler truck tires .005 Best car tires .0075 Typical car tires .01 Car tires on sand .3
Wheel diameter = D Wheel sinkage depth = Z Rolling coefficient = C_{roll} ≈ (Z/D)^{½}
Energy = E Joules Time = T seconds Power = P = E/T Watts Mass = M kilograms Energy/Mass = e = E/M Joules/kilogram Power/Mass = p = P/M Watts/kilogram
Most fuels are combinations of carbon, hydrogen, and oxygen, and are collectively called "hydrocarbons".
Black: Carbon White: Hydrogen Red: Oxygen
The energy sources that can be used by vehicles are:
Energy/Mass Power/mass Energy/$ Rechargeable Charge Maximum charging MJoule/kg Watt/kg MJoule/$ time cycles Gasoline 45 60 Battery, aluminum 4.6 130 No Battery, lithium .8 1600 .010 Yes 1 hour 1000 Supercapacitor .016 8000 .00005 Yes Instant Infinite Aluminum capacitor .010 10000 .0001 Yes Instant Infinite
Speed Power Force Force Force Mass Drag Drag Area Drag Roll Year 100kph (total) (fluid) (roll) (data) (specs) coef coef time m/s kWatt kN kN kN ton m^{2} m^{2} m^{2} s eSkate 5.3 .11 .021 .013 .008 .08 .76 1.0 .01 eScooter Zoomair 7.2 .25 .035 .027 .008 .08 .85 1.0 .01 Bike 10 .30 .035 .030 .005 .10 .49 1.0 .005 Bike 18 1.78 .103 .098 .005 .10 .50 1.0 .005 eBike 250 Watt 8.9 .25 .028 .023 .005 .10 .48 1.0 .005 eBike 750 Watt 10.6 .75 .071 .066 .005 .10 .96 1.0 .005 eBike 1 kWatt 12.5 1.0 .080 .075 .005 .10 .79 1.0 .005 eBike 1.5 kWatt 15.3 1.5 .098 .093 .005 .10 .65 1.0 .005 eBike 3 kWatt 16.7 3.0 .180 .175 .005 .10 1.03 1.0 .005 eBike Stealth H 22.2 5.2 .234 .228 .006 .12 .76 1.0 .005 eBike Wolverine 29.2 7.0 .240 .234 .006 .12 .45 1.0 .005 Bike, record 22.9 3.66 .160 .155 .005 .10 .48 1.0 .005 Bike, steamline 38.7 3.66 .095 .090 .005 .10 .099 .11 .005 Loremo 27.8 45 1.62 1.58 .035 .47 3.39 .25 1.25 .20 .0075 2009 Mitsubishi MiEV 36.1 47 1.30 1.22 .081 1.08 1.53 .35 .0075 2011 Aptera 2 38.1 82 2.15 2.09 .062 .82 2.36 .19 1.27 .15 .0075 2011 Nissan Leaf SL 41.7 80 1.92 1.81 .114 1.52 1.71 .72 2.50 .29 .0075 2012 10.1 Volkswagen XL1 43.9* 55 1.25 1.19 .060 .80 1.01 .28 1.47 .19 .0075 2013 11.9 Chevrolet Volt 45.3 210 4.64 4.52 .121 1.61 3.61 .62 2.21 .28 .0075 2014 7.3 Saab 900 58.3 137 2.35 2.25 .100 1.34 1.09 .66 1.94 .34 .0075 1995 7.7 Tesla S P85 249+ 69.2* 568 8.21 8.06 .150 2.00 2.76 .58 2.40 .24 .0075 2012 3.0 BMW i8 69.4* 260 3.75 3.63 .116 1.54 1.24 .55 2.11 .26 .0075 2015 4.4 Nissan GTR 87.2 357 4.09 3.96 .130 1.74 .85 .56 2.09 .27 .0075 2008 3.4 Lamborghini Dia 90.3 362 4.01 3.89 .118 1.58 .78 .57 1.85 .31 .0075 1995 Porsche 918 94.4 661 7.00 6.88 .124 1.66 1.27 .29 .0075 LaFerrari 96.9 708 7.31 7.19 .119 1.58 1.26 .0075 Lamborghini SV 97.2 559 5.75 5.62 .130 1.73 .98 .0075 Bugatti Veyron 119.7 883 7.38 7.24 .142 1.89 .83 .74 .0075 2005 Hummer H2 242 .218 2.90 2.46 4.32 .57 .0075 2003 Formula 1 .053 .702 .9 .0075 2017 Bus (2 decks) 138 12.6 .005 2012 Subway (R160) 24.7 448 38.6 .0004 2006 Airbus A380 320 435200 1360 1360 21.8 F22 Raptor 740 231000 312 312 .93 Blackbird SR71 1100 332000 302 302 .41 Skydive, min 40 30 .75 .75 0 .075 .77 1.0 0 Skydive, max 124 101 .75 .75 0 .075 .080 1.0 0 Sub, human power 4.1 1.78 .434 .051 Blue Whale 13.9 3750 270 2.74 Sub, nuke 17.4 30000 1724 11.2 Virginia Class *: The top speed is electronically limited Drag (data) Drag parameter obtained from the power and top speed Data (specs) Drag parameter from Wikipedia Force (total) Total drag force = Fluid drag force + Roll drag force Force (fluid) Fluid drag force Force (roll) Roll drag force Area Cross section from Wikipedia Drag coef Drag coefficient from Wikipedia Roll coef Roll coefficient. Assume .0075 for cars and .005 for bikes. 100kph time Time to accelerate to 100 kphFor the skydiver, the minimum speed is for a maximum cross section (spread eagled) and the maximum speed is for a minimum cross section (dive).
Wiki: Energy efficiency in transportation
For a typical car,
Car mass = M = 1200 kg Gravity constant = g = 9.8 m/s^{2} Tire rolling drag coeff = C_{r} =.0075 Rolling drag force = F_{r} = C_{r} M g = 88 Newtons Air drag coefficient = C_{a} = .25 Air density = D = 1.22 kg/meter^{3} Air drag crosssection = A = 2.0 m^{2} Car velocity = V = 17 m/s (City speed. 38 mph) Air drag force = F_{a} = ½C_{a}ADV^{2} = 88 Newtons Total drag force = F = F_{r} + F_{a} = 176 Newtons Drag speed = V_{d} = 17 m/s Speed for which air drag equals rolling drag Car electrical efficiency = Q = .80 Battery energy = E = 60 MJoules Work done from drag = EQ = F X = C_{r} M g [1 + (V/V_{d})^{2}] X Range = X = EQ/(C_{r}Mg)/[1+(V/V_{d})^{2}] = 272 kmThe range is determined by equating the work from drag with the energy delivered by the battery. E Q = F X.
The drag speed V_{d} is determined by setting F_{r} = F_{a}.
Drag speed = V_{d} = [C_{r} M g / (½ C_{a} D A)]^{½} = 4.01 [C_{r} M /(C_{a} A)]^{½} = 17.0 meters/second
Electric car engine .80 Gasoline engine .15 Diesel engine .20 Human muscles .22 Biomass plant .25 Natural gas plant .35 Solar cell .20 Crystalline type Solar cell .40 Multilayer type Turboprop, Mach .4 .80 Turboprops work up to Mach .5 Turbojet, Mach .4 .40 Turbofan, Mach .4 .68 Turbojet, Mach .9 .77 Turbofan, Mach .9 .90For an electric vehicle the overall efficiency is similar to that of a diesel engine.
Overall efficiency = Power plant efficiency * Vehicle efficiency = .35 * .80 = .28
Speed l/km l/km/ Passengers m/s person Walk 1.4 .0065 .0065 1 60 Watts Run .009 .009 1 Bike 4.4 .0032 .0032 1 Bike, aerodynamic 13.9 .0005 .0005 1 Car, solar power .067 .067 1 Car, electric, Tesla .015 .004 4 Car, electric, GEM NER 10.8 .012 .003 4 Car, electric, GE EV1 .026 .006 4 Car, electric, Volt .026 .006 4 Car, VW Bluemotion .038 .010 4 Car, Honda Insight .049 .012 4 Car, Toyota Prius .051 .013 4 Car, Cadillac Wagon .17 .028 6 6.2L engine Car, Bugatti Veyron .24 .12 2 Train, Switzerland .17 .0026 65 Train, Japan .65 .011 59 Plane, Dieselis 44.4 .019 .010 2 Plane, Pipistrel Sinus 62.5 .048 .024 2 Plane, Tecnam Sierra 65.8 .072 .036 2 Plane, DynAero MCR4S 61.1 .088 .022 4 100 hp Plane, Boeing 747400 3.1 660 Plane, Concorde 16.6 128 Plane, Airbus A380 3.0 835 Ship, Queen Elizabeth 300 .17 1777 Ship, Cargo 12.8 1070   Emma Maersk. 170000 tons Helicopter, Sikorsky 72.2 1.43 .12 12 Model S761 litre gasoline = 31.7 MJoules
MJ/km/ Passengers person per vehicle Train, Switzerland .085 65 Train, Japan .35 59 Car, electric 1.2 1.5 Train, city 1.60 30.9 Train, intercity 1.65 24.5 Motorcycle 1.61 1.16 Air 1.85 99.3 Car, gasoline 2.32 1.55 Bus 2.78 9.2 Taxi 10.3 1.55
MJ/km/ton Ship, U.S. local .16 Ship, ocean cargo .22 Emma Maersk. 170000 tons Train .21 Truck 2.43 Air 6.9
For a 1level prefabricated square bamboo house,
Side length = 8 meters Wall height = 3 meters Floor area = 64 meters^{2} Wall area = 24 meters^{2} Interior walls = 24 meters^{2} Total wall area = 248 meters^{2} Floor, ceiling, 4 walls, and interior walls Wall thickness = .05 meters Wall volume = 12.4 meters^{3} Bamboo density = 350 kg/meter^{2} Bamboo mass = 4.3 tons Carbon mass = 2.2 tons Bamboo carbon frac= .5 House mass = 7.0 tonsA helicopter can carry 12 tons. A prefabricated house can be placed anywhere in the wilderness and multiple modules can be assembled on site.