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Street fu
Dr. Jay Maron

g
Calories per dollar of food
Coats and thermal insulation
Battery heater
Hydroponics
Prefab homes
Electric vehicles
Electric bikes


Human nutrients

A vitamin pill covers all micronutrients. The macronutrients are:

         Requirement  Centrum
            g/day        g

Protein      50        0
Potassium     3.5      .08
Calcium       1.0      .2
Phosphorus    1.0      .02
Magnesium      .35     .05
Foods with high macronutrient density. Numbers in parts per thousand.
          Phosphorus  Potassium  Calcium  Magnesium  Protein

Sunflower seed  6.6      6.4       .8        3.3       179
Cheddar         5.1      1.0      7.2         .28      283
Peanut          3.8      7.1       .9        1.7       267
Beef            3.0      2.4       .12        .19      247
Turkey          2.1      3.0       .1         .21      293
Egg             1.9      1.3       .53        .12      120
Milk             .9      1.4      1.1         .10       33
Potato           .7      5.4       .15        .28       13
Rice             .7       .8       .11        .23       52
Avocado          .5      4.8       .1         .29       13
The ultimate macronutrient food is sunflower seeds. The cheapest source of macronutrients is cheese and peanuts.
Food cost

We calculate the price for food for 1 year. We assume 2600 calories/day.

              Energy  Price  Efficiency
              Cal/kg  $/kg     Cal/$

Rice (dry)     3330    2.86   1160
Peanut         6000    6.60    910
Sunflower seed 5710   10.00    571
Chicken        2762    5.00    550
Milk            422     .80    530
Mountain Dew    440    1.00    440
Turkey         2429    6.00    404
Cheddar        4040   10.00    404
Beef           3380    9.00    375
Watermellon     300     .83    361
Egg            1400    4.00    350
Potato          930    2.84    327
Mozarella      2780    8.80    315
Palm oil       7353   24.00    306
Corn            860    4.40    195
Apple           579    5.00    115
Cucumber        154    2.00     77
Tomato          249    4.41     56
Lettuce          95    5.57     17
Cherry tomato   176   11.76     14
Rice is the cheapest source of calories and peanuts are the cheapest source of macronutrients. You can feed a person for 2.5 $/day with rice, peanuts, and a vitamin pill.
Thermal insulation

The best insulator is air, which is why fluffy low-density materials like pillows and down coats are good insulators. The properties of a good coat are:

*) Thick. Insulation quality is proportional to thickness.
*) Low density Insulation quality is inversely proportional to density.
*) Airtight.
*) Full length.

The quality of thermal insulation is given by:

Material thickness            =  X
Material thermal conductivity =  C
Insulation quality            =  Q  =  X/C

A layer of fluffy liner is far more insulating than a leather layer. Fluffy liner has a thermal conductivity not much larger than air.

             Thickness    Thermal          Insulation      Mass/Area
                        conductivity        quality
                mm      Watts/K/meter  Kelvin/meter2/Watt  kg/meter2

Leather layer     1           .5             2              1
Fluffy liner      5           .025         200               .1

If you have a stout coat then most of your heat is lost through your legs. The next step is to use fluffy airtight snowpants.

Some common thermal conductivities are:

         Watts/Kelvin/meter

Steel         45
Granite        2.5
Glass           .8
Water           .6
Brick           .5
Plastic         .5
Plexiglass      .2
Wood            .1
Plastic foam    .03
Air             .025


Head power

The head generates heavy power and is easy to keep warm. One has to protect this heat with a hat. When resting,

            Power   Surface area   Heat flux
            Watts     meters2      Watts/meter2

Head          20         .13         160
Body         100        3             33

Thermal physics

Insulation thickness      = X               meters
Thermal conductivity      = C               Watts/Kelvin/meter
Insulation quality        = Q = X/C         Kelvin meter2/Watt
Temperature differential  = T               Kelvin
Heat flux                 = F = CT/X = T/Q  Watts/meter2

Battery-powered heater

Battery
Ceramic power resistor
USB cable
Solder
Battery and resistor circuit

A heater can be built with a battery and a resistor. Example values:

Voltage     =  V  =  I R           =  5   Volts           Phone charging battery
Resistance  =  R                   = 10   Ohms
Current     =  I                   =   .5 Amperes
Power       =  P  =  V I  =  V2/R  =  2.5 Watts

Large "power resistors" should be used. The larger the power, the larger the resistor has to be.

Resistors have a maximum power rating. If you use this power, the resistor won't melt but it will melt your coat. To make it coat safe, use 1/8 of the maximum power. In the above example where the resistor dissipates 2.5 Watts, a resistor rated at 20 Watts maximum should be used.

A USB wire can connect the battery to the resistor. A USB cable has 4 wires:

Red       Positive voltage
Black     Zero voltage  (ground)
White     Positive data
Green     Negaive data

The red and black wires carry power and the white and green wires carry data. Strip the red and black wires and connect them to the resistor. The USB end connects to the battery.

If multiple resistors are used then they should be connected in parallel.

Typical costs are:

              $

Battery      10       5 Volts, 10 Amphours
Resistor      2       10 Ohms, 20 Watt maximum
USB wire      2
Solder        2       For connecting wires
Wires can be connected with solder. A lighter can melt solder and so you don't need a soldering iron.
Power resistors

The larger the power dissipated by the resistor, the larger the resistor has to be. Values for commercial power resistors:

Power  Length  Width  Depth  Mass  Power/Area
Watts    mm     mm     mm     g    Watts/cm2

  5      22     10     10      5      .46      Ceramic
 10      48     10     10     11      .47      Ceramic
 20      62     12     12     19      .61      Ceramic
 50      48     15     15     23     1.9       Aluminum
100      60     16     16            2.9       Aluminum

Batteries

Voltage     =  V                 Volts
Current     =  I                 Amperes
Time        =  T                 seconds
Charge      =  C  =  I T         Amp seconds
Power       =  P  =  V I         Watts
Energy      =  E  =  P T = C V   Joules

Commerical batteries from Amazon:

Brand       Price  Charge   Voltage   Energy   Current  Power  AC
              $    Amphour   Volts   Watthour   Amps    Watts

Expertpower  11      10        5        50       3       15    No
Expertpower  16      20        5        80       5       25    No
Qualcomm     28      10       12       120       1.5     18    No
Talent       50       8       12        96       6       72    No
Libower      60      15       24       360       2.5     60    No
100percent   30      11        5        55                     Yes

AC: 120 Volt AC

Numbers are usually expressed in hours rather than seconds. For example,

Energy  =  1 Watt hour  =  3600 Watt seconds  =  3600 Joules

Hydroponics

Hydroponics is the technique of growing plants in water rather than soil, where the water is fertilized with nutrients. Hydroponics can yield 100 times as much food as soil-based agriculture, and a person can be sustained with only 200 square meters of hydroponics.

Hydroponics is easy. One can buy a system that takes care of everything and one need only supply the system with water and fertilizer. One can further improve yield with greenhouses, lighting, and mirrors.


Hydroponic system

Grow kit
Nutrient solution
Mirror foil
LED light
Sturdy greenhouse
Unsturdy greenhouse

A "grow kit" takes care of supplying the plants with water. One need only supply the kit with water and fertilizer. Fertilizer comes in powder form and dissolves in the water. Kits cost $2 per plant site.

Putting a greenhouse around the kit amplifies the yield by allowing one to control temperature and humidity. A greenhouse also allows plants to be grown during the winter.

Mirrors can amplify the sunlight reaching the planet, and mirror film is cheap.

Lights can improve the growth rate and make it possible to grow plants 24 hours.

A hydroponics system can be ordered online from places such as Amazon and Wallmart, and examples of costs are:

                               $     Amazon link

Grow kit, 11 sites             25    *
Grow kit, 90 sites            160    *
Fertilizer, 10 kg              13    *
LED grow light, 1000 Watts    140    *
Mirror film, 400 square feet   24    *
Greenhouse                    120    *

Nutrient solution

1 kg of nutrient powder is mixed with ton of water. The composition of a typical nutrient solution is

        Parts per million

Potassium       160
Nitrogen        150
Calcium         100
Phosphorus       40
Sulfur           40
Magnesium        30
Iron              2
Manganese          .5
Zinc               .3
Boron              .2
Copper             .1
Molybdenum         .075
Source
Crop yield
             Yield      Yield     Energy
           kCal/m2/yr  kg/m2/yr   Cal/kg

Potato          48        52       923
Onion           20        50       400
Tomato cherry   17.2      98       176
Blueberry       13.8      24       573
Cucumber        12.6      82       154
Tomato          12.4      50       249
Lettuce          7.0      74        95

Hydroponic yield vs. field yield

Hydroponics offers gains over field agriculture in many categories. The following table shows the amplification for each category in terms of hydroponic yield over field yield. The total amplification is the product of the amplification from each category.

Plant density               8          In terms of plants/meter2
Crops per year              4
Crop variety                2
Temperature contro l        2
LED lighting                2
Carbon dioxide enhancement  1.5

Hydroponic physics

Soil mass yield             =   1  grams/meter2/day      Data
Hydroponic mass yield       = 100  grams/meter2/day      Data
Typical food energy density =1000  Calorie/kg             (Potato = 930 Cal/kg)
Hydroponic calorie yield    = 100  Calorie/meter2/day
Calorie requirement per day =2600  Calorie/day
Hydroponic area/person      =  26  meters2     (Area required to sustain one person)

Hydroponic yield/growsite   =   4  kg
Electricity cost            =  30  MJoules/$
Minimum water flow rate     =  .5  Litre/minute
Optimal water flow rate     =   1  Litre/minute
Maximum water flow rate     =   2  Litre/minute
Maximum pipe length         =  10  meters                      (If longer, nitrogen becomes depleted)

Grow kit cost              =   2  $/growsite
Largest kit size           =  72  growsites
Nutrient solution cost     =  13  $/kg       (solid form)
Water requirement          = 500  kg of water per kg of solid nutrient fertilizer
LED lamp cost              =   7  Watts/$
Mirror film cost           = 1.5  meter2/$
Transparent acrylic sheets =  32  $/meter2
Greenhouse cost (sturdy)   =.016  meters3/$        (Plexiglass. Survives high wind)
Greenhouse cost (unsturdy) =.18   meters3/$        (Plastic. Cannot survive high wind)

O2 solubility in H2O, 10 C  =11.2  mg/Litre
O2 solubility in H2O, 20 C  = 9.1  mg/Litre
O2 solubility in H2O, 30 C  = 7.2  mg/Litre
O2 density in the atmosphere= 280  mg/Litre
The water pipes should exclude light to prevent algae growth.
Artificial light

The most efficient plant for converting sunlight to food energy is sugar cane, which has an efficiency of 7%. If LED lights are used to grow food for 1 person then the electrical power required is:

LED light efficiency       =  Ql          =  .2
Sugar cane efficinecy      =  Qc          =  .07
Plant efficiency           =  Qp          =  .5        Efficiency relative to sugar cane
Total efficiency           =  Q  = QlQcQp =  .007
Human power                =  P           =  120 Watts
LED power                  =  p  = P/Q    =17000 Watts
Electric energy/dollar     =  c           =   40 MJoules/$
Electricity cost for 1 year=  C           =12750 $

The sun

Arizona solar intensity, peak  =1000  Watts/meter2   (Noon in mid-summer)
Arizona solar intensity, ave.  = 250  Watts/meter2   (Averaged over day and night)
Manhattan solar intensity, ave.= 155  Watts/meter2
Electricity cost per Joule     =  36  MJoules/$
Energy in one day              =13.4  MJoules/day/meter2
Cost for one day               = .37  $/day/meter2

Cooling

A greenhouse can be cooled by evaporating water.

Melting energy of water at 0 Celsius        =     334  kJ/kg
Vaporization energy of water at 100 Celsius =    2257  kJ/kg
Energy to raise water from 0 to 30 Celsius  =     126  kJ/kg
Total energy for melting ice                =    2717  kJ/kg

Calories
1 Calorie                   =  4184 Joules
Daily requirement for men   =  2600 Calories
Daily requirement for women =  2000 Calories

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

Benches

Not all benches are created equal. Care must be taken in designing a bench that is comfortable.

The higher the back of the bench, the better. Best of all is if the bench can support the back of your head.
Benches with curvature are more comfortable than flat benches.
There should be space underneath the bench for your feet.
There should be a canopy for rain, with side walls to shield against wind.
There should be benches in the sun for cold weather and benches in the shade for hot weather.
Benches should have arm rests.


Electric vehicles

Electric vehicles outperform gasoline vehicles in all regards except range, and if you splurge on the battery you can have the range (and ludicrous power). Electric vehicles are more powerful, quieter, simpler, more flexible, and cheaper than gasoline vehicles, and you can put an electric motor on anything, even a rollerblade. Electric power is ideal for compact and cheap city vehicles.


Power

To give a sense for the strength of human and electric power,

                          kiloWatts

Human unstrenuous cycling     .1
Human strenuous cycling       .3
Human sprint cycling         1
Typical electric bike        1
Monster electric bike        6
Typical car                100
Electric power opens the way for light cheap city vehicles. Electric power easily has the speed and range for city driving.
Speed

To give a sense for the relationship between power and top speed,

        Power   Speed   Speed
        kWatt    m/s     mph

Bike      .12     7      17     Human unstrenuous cycling
Bike      .25     9      21     Human strenuous cycling
Bike     1       15      33     Human sprint cycling
Bike     2       19      42
Bike     4       24      53

Trike    1       12      26
Trike    4       19      42
Trike   16       30      67

Car     16       26      58     Minimum power for cities
Car     32       33      73     Minimum power for highways
Car     64       41      92     Minimum power for freeways
Car    128       52     116     Typical car
Car    512       82     184     Sports car

Battery

Typical values for a 16 kWatt car battery are:

Energy/Mass   =  e  =  E/M  =   .8   MJoules/kg
Power/Mass    =  p  =  P/M  =  1.2   kWatts/kg
Energy/Cost   =  c  =  E/C  =   .01  MJoules/$
Power/Cost    =  d  =  P/C  =   .012 kWatts/$
Energy/Power  =  D  =  E/P  =   .67  MJoules/kWatt
Mass          =  M  =       = 13     kg
Energy        =  E  =       = 11     MJoules
Power         =  P  =       = 16     kWatts
Cost          =  C  =       = 1330   $

Range

Air drag determines a vehicle's top speed, energy use, and minimum battery power. A 16 kWatt car with a minimalist battery has a range of 30 km when driving at a speed of 20 meters/second.

Air density        =  D                        =  1.22 kg/meter3
Air drag coef.     =  K                        =   .75 meters2
Car speed          =  V                        = 20    meters/second
Air drag force     =  F  =  K D V2  =366    Newtons
Air drag power     =  P  =  K D V3  =  7.3  kWatts
Battery energy     =  E                        = 11    MJoules
Distance traveled  =  X  =  E/F                = 30    km

Energy efficiency

The goal is to minimize the energy cost per person. For an N-person vehicle,

People            =  N
Distance traveled =  X
Air drag force    =  F
Energy            =  E  =  F X
Energy efficiency =  Q  =  E/(NX)  =  F/N
The energy efficiency is equal to the air drag force divided by the number of passengers. Example values for various vehicles:
                        Speed    Power     Force   Force/prsn  People   Range  Drag area
                         m/s     kWatt     Newton    Newton              km     m2

Skate                      10       .18     18         18         1       5       .3
Kick scooter               10       .18     18         18         1       5       .3
Bike                       15       .82     55         55         1       8       .4
Car, small, city speed     20      4.9     244        244         1      10      1
Car, large, freeway speed  30     33      1100       1100         1      15      2
Bus, freeway speed         30     99      3290         46        72      15      6
Train car, freeway speed   30     99      3290         27       120      15      6
Airbus A380               251 251000   1000000       1840       544   10000    160

1 Horsepower  =  746 Watts
A full bus is 5 times more efficient than a compact car, but buses are rarely full and usually slow.

Buses and trains are substantially more efficient than planes and should be favored over short flights.

Trains are not substantially more efficient than buses and they are far less flexible.


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

Solar cells

A typical solar farm costs 5 $/Watt and produces 30 MWatts/km2, and America's electricity requirement can be satisfied by a farm that is 5% the size of Arizona. The largest farms are:

                                       GWatts  km2  MWatts/km2  B$  $/Watt

California   Solar Star                   .58   13    45
California   Topaz                        .55   25    22      2.5   4.5    Thin film CdTe
California   Desert Sunlight              .55   16    34                   Thin film CdTe
China        Longyangxia Dam              .32    9    36
California   Cal. Valley Solar Ranch      .29    8    36      1.6   5.5    Silicon crystal
Arizona      Agua Caliente Solar Project  .29   10    29      1.8   6.2    Thin film CdTe


       Solar power capacity (GWatts)

World         139
Germany        38.2
China          28.2
Japan          23.3
Italy          18.5
USA            18.3
France          5.7
Spain           5.4
UK              5.1
Australia       4.1

American solar farms tend to be in California or Arizona where sunlight is abundant. We calculate the payback time for a typical 1 meter2 solar cell in Arizona.

Solar cell efficiency         =  e             =  .20               Converting solar to electric energy
Arizona solar intensity, peak =  Ipeak          = 1000 Watts         Noon in mid-summer
Arizona solar intensity, ave. =  Iave           =  250 Watts         Averaged over day and night
Solar cell peak power         =  Ppeak =  e Ipeak=  200 Watts
Solar cell average power      =  Pave  =  e Iave =   50 Watts
Solar cell operation time     =  T              =  2.3 years         Payback time
Solar cell energy generated   =  E    =  Pave T = 3622 MJoules
Electricity cost per Joule    =  Qelec          =2.8⋅10-8 $/Joule  =  .10 $/kWh
Value of electricity generated=  Celec =  E Qelec=  100 $
Solar cell cost               =  Ccell           =  100 $
Solar cell cost per peak Watt =  Qcell =Ccell/Ppeak= .50 $/Watt
Setting the cost of the solar cell equal to the value of the energy generated,
Ccell  =  Celec  =  e Iave T Qelec

Payback time  =  T  =  Ccell / (e Iave Qelec)  =  2.3 years
A solar farm in Arizona large enough to supply all of America's electricity is a square 120 km on a side, which is 5% of the area of Arizona.
U.S. total power                =  3000 GWatts
U.S. electric power             =   500 GWatts
U.S. solar power                =    21 GWatts
U.S. power/person               =  9400 Watts
U.S. population                 =   320 million
Solar farm power per area       =    35 MWatts/km2     (Typical solar farm)
Solar farm area                 = 14300 km2
Arizona area                    =295234 km2
Solar farm side length          =   120 km             (Assume a square)

Silver is the most reflective metal

The types of solar cells are:

Technology         Efficiency  $/Watt  Market frac   Key element   Element cost ($/kWatt)

Thin film Ga As           .29                        Gallium
Crystalline Si (mono)     .25     .50     .36        Silver        48
Crystalline Si (poly)     .20     .50     .55        Silver       100
Thin film Cu In Ga Se     .20             .02        Indium
Thin film Cd Te           .16             .051       Tellurium      5
Thin film Amorphous Si    .11             .02        -
Multi junction            .41                        Gallium
World record              .44


Energy cost of silicon crystal= 39.6  MJ/kg
Electricity cost              =   36  MJ/$
Silicon crystal cost          =  1.1  $/kg
Monocrystal silicon           =  6.0  kg/kWatt
Monocrystal silicon cost      =  6.6  $/kWatt
Crystal silicon thickness     =  .18  mm
Thin film (CdTe) tellurium    = .093  kg/kWatt     =  4.6 $/kWatt
Silicon-monocrystal silver    =  .05  kg/kWatt     =   48 $/kWatt  =   100 $/kg  =  .0096kg/m2
Silicon-polycrystal silver    =  .10  kg/kWatt     =  100 $/kWatt  =  1000 $/kg  =  .020 kg/m2
Price of silver               =  264  $/kg

Inverter

A solar cell system requires an inverter to convert DC to AC power. For a 1 meter2 cell,

Solar cell efficiency               =  e
Peak power                          =  Ppeak =  e Ipeak    =  200 Watts
Cost of inverter per peak Watt      =  Qinv  =  .15 $/Watt
Cost of inverter                    =  Cinv  =  Qinv Ppeak  =  15 $
Cost of solar cell                  =  Ccell               = 100 $
Total system cost                   =  Ctotal              = 200 $
The the inverter costs less than the solar cell.
Acknowledgements

We give thanks to Broadway Presbyterian Church, Starbucks, and Morning 2 Midnight.


Appendix

Lithium-ion batteries

The properties of the best commercial lithium ion batteries are:

Energy/Mass     =    .8  Joule/kg
Power/Mass      =  1200  Watt/kg
Energy/$        =    .01 MJoule/kg
Density         =   3.5  gram/cm3
Recharges       =1000
Shelf life      =   1.0  year
Voltage         =   3.7  Volt
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 max   Cell    Cell  Cell  Cell brand
kWatt                                  Amperes  Amperes  Amphours   $    type

   .75  36     10      10       1         21      30       2.0      5     A    Sony VTC4
  1.5   48     13      13       1         31      60       4.5      8     C    Basen
  3     72     20      20       1         42      60       4.5      8     C    Basen
  6     72     40      20       2         83     120       4.5      8     C    Basen
 12     72     80      20       3        167     180       4.5      8     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
Cellmax   Maximum current of a cell

Gigafactory

The Gigafactory in Nevada has a production target for 2020 of:

Battery production   =  200 TeraJoules/year
Energy of one car    =  310 MJoules           (Tesla Model S)
Cars supplied/year   =  .64 million
The Solar City Factory produces solar panels.
Panel production  =  1.0 GWatts/year
Panel duty factor =  .25        (Average solar intensity over peak solar intensity)
Effective power production  =  .25 GWatts/year

Electricity cost
Cost of electricity       =  30  MJoules/$
Crop time                 =   3  Mseconds  =  40 days
Lamp power                =1000  Watts
Lamp energy per crop      =   3  GJoules/crop
Lamp energy cost per crop = 100  $/crop

Fertilizer composition

The following table shows the elemental composition of a typical hydroponic nutrient solution in parts per million.

Nitrogen     600
Calcium      400
Sulfur       400
Potassium    250
Magnesium     80
Phosphorus    80
Iron           4
Boron          2
Nickel         1
Manganese       .8
Zinc            .5
Copper          .5
Molybdenum      .01
Hydroponic fertilizer can be purchased in solid form for $12/kg on Amazon.com. One kg of solid fertilizer supplies 500 kg of water.
Citrus growing regions


Soundproofing


Transmission through a wall

The left column is the change in decibel level provided by soundproofing.

Decibels

  25   Normal speech can be understood quite easily and distinctly through wall
  30   Loud speech can be understood fairly well, normal speech heard but not understood
  35   Loud speech audible but not intelligible
  45   Loud speech not audible
  50   Very loud sounds such as musical instruments or a stereo can be faintly heard;
  60   Most sounds inaudible
Table for the reduction in intensity of sound for various kinds of walls. Values in decibels.
33  Typical interior wall
46  6 inch hollow concrete masonry
50  10 inch hollow concrete masonry

Wall thickness

Sound transmission through the wall depends on the thickness of the wall.


L       =  Thickness of a wall
Dair    =  Density of air
Dwall   =  Density of wall material
P       =  Characteristic pressure fluctuation of a sound wave striking the wall
V       =  Characterstic velocity fluctuation of a sound wave striking the wall
T       =  Wave period
F       =  Wave frequency
        =  1/T
Vwall   =  Characteristic recoil velocity of a wall upon being struck by a sound wave

V^2  ~  P / Dair
The impulse per area delivered to the wall is
Impulse / Area  ~  P T
                ~  Dair T V^2
The impulse per area is equal to the momentum per area delivered to the wall
Dair T V^2  ~  Dwall L Vwall

Vwall  ~  (Dair/Dwall) V^2 / (LF)
The wall recoil generates a sound wave on the other side of the wall with a characteristic fluctuation magnitude of Vwall. The decibel level is proportional to the logarithm of the velocity.
log(Vwall)  =  Constant - log(L) - log(F)
The change in decibel level is proportional to the logarithm of the wall thickness. It's better to divide a wall into many layers rather than having one solid wall.

The change in decibel level is proportional to the logarithm of the frequency. Low-frequency waves are difficult to block.


Impact transmission


If a sound wave strikes a wall then only a small fraction of the energy is transmitted through the wall. If an object strikes the wall then a substantial amount of energy is transmitted through the wall. Carpets are a big help for soundproofing.


Noise

Noise is often characterized with a power spectrum because the properties of soundproofing depend on frequency. It is easier to stop high-frequency noise than low-frequency noise.


Anechoic chamber

f-16 in an anechoic test chamber

The walls of an anechoic chamber absorb all sound.

The absorbers are pointy to minimize the reflection of sound.

The information rate for sound is kilobytes/second and the rate for vision is megabytes/second.


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