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City design
Driverless electric cars and prefab homes
Dr. Jay Maron

Electric cars
City design
Prefab homes
Electric bikes
Electric flying cars


City travel time

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)  (km2)  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, bike
Electic 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:
*) Take the elevator from whatever floor you're on to the ground floor.
*) Walk to the subway
*) Wait for the subway
*) Ride the subway
*) Transfer subways
*) Wait for the subway
*) Ride the subway
*) Walk from the subway station to the destination skyscraper
*) Take the elevator from the ground floor to the destination floor

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/km2.


Travel time

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/km2  =  1 person every 10 meters2
City population         =  P = πDR2=280000 people
It helps to centralize. 4 points of focus of a city are the college, the pub district, the shopping district, and the K-12 school. These can be placed in the city center and the residences and businesses radiate out from the center.
Prefabricated homes

Prefabricated homes cost in the range from 20 to 100 $/foot2. A 400 foot2 minimalistic home costs on order 8000 $.


Shipping containers

Prefabricated homes can be made from shipping containers, which are abundant, cheap, and easily delivered.


                               $   Length  Width  Height  Mass
                                     ft     ft      ft     kg

10-foot shipping container   1000    10      8     8.5    1300
20-foot shipping container   1200    20      8     8.5    2200
40-foot shipping container   1500    40      8     8.5    3800
Typical mobile home                  90     18

Wilderness

Prefabricated houses can be helicoptered to wilderness locations and flying cars can be used to reach them.


Energy/Mass and Power/Mass

Tesla Roadster

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

Electric vehicles

Energy cost

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 drag
Buses 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      1
For 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.


Batteries

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.
Air drag and battery power

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/meter3
Drag parameter  =  K
Speed           =  V
Drag power      =  P  =  ½ K D V3
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      29000
For 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 and battery energy

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       41
City cars have plenty of range for city driving while freeway cars need to reharge often.
Flying electric cars

Design

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 single-propeller 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/second2
Rotor force         =  F = Mg/N =1960    Newtons
Rotor quality       =  q        =   1.02
Air density         =  D        =   1.22 kg/meter3
Rotor power         =  Pr=(qDR)-1F3/2= 46.2  kWatts
Hover power         =  Ph= N Pr =  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/Ph = 812    seconds  =  14 minutes
The 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/s
The 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.
Mass

For the large propellers,

Propeller radius          =  R  =  1.5 meters
Propeller mass parameter  =  C  =  5   kg/meter3
Propeller mass            =  M  =  C R3  =  17 kg
For the motors on the large propellers,
Motor power      = 60 kWatts
Motor power/mass =  8 kWatts/kg
Motor mass       =7.5 kg
The 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

Flight time

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       =  Mbat        =  .5 kg           (The battery is the most vital component)
Battery energy     =  E          =  .38 MJoules
Battery energy/mass=  ebat= E/Mbat=  .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 minutes
The flight time in terms of component parameters is
T  =  (ebat/p) * (Mbat/M)

Electric bikes

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      3.6
The 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.


Electric bike speed limits
             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

Batteries

Lithium batteries

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/cm3
Recharges       =1000
Shelf life      =   1.0  year
Voltage         =   3.7  Volt
Max temperature =  60    Celsius
Min temperature = -20    Celsius
Energy/Mass and Power/Mass are an engineering tradeoff. One can be increased at the expense of the other.
Battery sizes

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

Battery packs

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 high-power 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

Battery pack strategy

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

Acknowledgements

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.


Appendix

Electric car vs. electric aircraft

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=  eair= 1.0 Joules/m/kg
Electric aircraft flying time         =  T  =3600 seconds
Electric aircraft range               =  X  = 180 km
Gravity constant                      =  g  = 9.8 m/s2
Electric car mass                     =  M
Electric car rolling drag coefficient =  Cr = .0075
Electric car rolling drag             =  Fr =  Cr M g
Electric car total drag               =  F  =  2 Fr        (Assume rolling drag = air drag)
Electric car energy/distance/mass     =  ecar=  2 Cr g  =  .147 Joules/m/kg
Aircraft energy / Car energy          =  eair / ecar  =  6.8

Drag force

The drag force on an object moving through a fluid is

Velocity             =  V
Fluid density        =  D  =  1.22 kg/m2   (Air at sea level)
Cross-sectional area =  A
Drag coefficient     =  C
Drag force           =  F  =  ½ C A D V2
Drag power           =  P  =  ½ C A D V3  =  F V
Drag parameter       =  K  =  C A
"Terminal velocity" occurs when the drag force equals the gravitational force.
M g  =  ½ C D A V2
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 Vt = 6 m/s. If a skydiver has a mass of 100 kg then the area of the parachute required for this velocity is 46 meters2, which corresponds to a parachute radius of 3.8 meters.
Drag coefficient

               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
Formula-1 car       .9          The drag coeffient is high to give it downforce
Bicycle + rider    1.0
Skier              1.0
Wire               1.2

Rolling drag

Force of the wheel normal to ground  =  Fnormal
Rolling friction coefficient         =  Croll
Rolling friction force               =  Froll  =  Croll Fnormal

Typical car tires have a rolling drag coefficient of .01 and specialized tires can achieve lower values.
                             Croll

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
18-wheeler truck tires        .005
Best car tires                .0075
Typical car tires             .01
Car tires on sand             .3

Rolling friction coefficient
Wheel diameter          =  D
Wheel sinkage depth     =  Z
Rolling coefficient     =  Croll  ≈  (Z/D)½

Energy and power

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

Fuel

Most fuels are combinations of carbon, hydrogen, and oxygen, and are collectively called "hydrocarbons".

Black: Carbon        White: Hydrogen        Red: Oxygen

Methane (Natural gas)
Ethane
Propane
Butane (Lighter fluid)
Octane (gasoline)
Dodecane (Kerosene)

Hexadecane (Diesel)
Palmitic acid (fat)
Ethanol (alcohol)

Glucose (sugar)
Fructose (sugar)
Galactose (sugar)
Lactose = Glucose + Galactose
Starch (sugar chain)
Leucine (amino acid)

ATP (Adenosine triphosphate)
Phosphocreatine
Nitrocellulose (smokeless powder)
TNT
HMX (plastic explosive)

Lignin (wood)
Coal

Medival-style black powder
Modern smokeless powder
Capacitor
Lithium-ion battery
Nuclear battery (radioactive plutonium-238)
Nuclear fission
Nuclear fusion
Antimatter


Energy/Mass and Power/Mass

Tesla Roadster

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

Transport cost

Leitras velomobile
Loremo
Edison 2
BMW i8

The Saab 900, last of the boxy cars
Lamborghini Diablo
Ford Escape Hybrid
Hummer H2

              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     m2      m2     m2                        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
F-22 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 kph
For the skydiver, the minimum speed is for a maximum cross section (spread eagled) and the maximum speed is for a minimum cross section (dive).

Cycling power

Wiki: Energy efficiency in transportation


Drag speed

For a typical car,

Car mass                   =  M           = 1200 kg
Gravity constant           =  g           =  9.8 m/s2
Tire rolling drag coeff    =  Cr          =.0075
Rolling drag force         =  Fr = Cr M g =   88 Newtons

Air drag coefficient       =  Ca          =  .25
Air density                =  D           = 1.22 kg/meter3
Air drag cross-section     =  A           =  2.0 m2
Car velocity               =  V           =   17 m/s      (City speed. 38 mph)
Air drag force             =  Fa = ½CaADV2 =  88 Newtons

Total drag force           =  F  = Fr + Fa = 176 Newtons
Drag speed                 =  Vd           =  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     =  Cr M g [1 + (V/Vd)2] X
Range                      =  X  = EQ/(CrMg)/[1+(V/Vd)2] =  272 km
The range is determined by equating the work from drag with the energy delivered by the battery.   E Q = F X.

The drag speed Vd is determined by setting Fr = Fa.

Drag speed  =  Vd  =  [Cr M g / (½ Ca D A)]½  =  4.01 [Cr M /(Ca A)]½  =  17.0 meters/second

Engine efficiency

Photoelectric cell
Thermoelectric generator
Stirling engine
Stirling engine

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   .90
For an electric vehicle the overall efficiency is similar to that of a diesel engine.
Overall efficiency  =  Power plant efficiency  *  Vehicle efficiency  =  .35 * .80 =  .28

Fuel efficiency
                       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 MCR-4S  61.1     .088   .022    4         100 hp
Plane, Boeing 747-400                 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 S-76
1 litre gasoline = 31.7 MJoules
U.S. transportation averages
                  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

Freight
                  MJ/km/ton

Ship, U.S. local    .16
Ship, ocean cargo   .22     Emma Maersk. 170000 tons
Train               .21
Truck              2.43
Air                6.9

Prefabricated bamboo house

For a 1-level prefabricated square bamboo house,

Side length       =    8 meters
Wall height       =    3 meters
Floor area        =   64 meters2
Wall area         =   24 meters2
Interior walls    =   24 meters2
Total wall area   =  248 meters2       Floor, ceiling, 4 walls, and interior walls
Wall thickness    =  .05 meters
Wall volume       = 12.4 meters3
Bamboo density    =  350 kg/meter2
Bamboo mass       =  4.3 tons
Carbon mass       =  2.2 tons
Bamboo carbon frac=   .5
House mass        =  7.0 tons
A helicopter can carry 12 tons. A prefabricated house can be placed anywhere in the wilderness and multiple modules can be assembled on site.
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