a streetcar system that is predominantly solar powered is a technically
feasible. By combining old and new technology, the new Brooklyn
Streetcar can be entirely powered by pollution free, renewable, solar
receive power (typically 600v DC) through an overhead wire.
Rather than exclusively utilizing conventionally generated power (from
a power plant or line power), solar
panels can be used. Solar panels, ("photo-voltaic arrays"), that
converts sunlight directly into electricity, can be utilized to power a
24hr power can be derived from the solar power system by utilizing a
battery array. Such an array could be built at convenient remote
locations. The need for any "static power converters" changing "AC"
power to "DC" power for the streetcars, would be completely
eliminated. (see end section of this webpage for another power
The best place to start, is at the beginning...
About 100 years ago, the Brooklyn Rapid Transit Company devised a
move-able storage battery array, to supply extra streetcar power "on
demand" to certain key areas, at certain times when streetcar traffic
would peak. When streetcar power demand was low, the battery array
collected a "trickle charge" from the overhead trolley wire. When rail
car power demand was high, the battery array could supply 600 volt
power to the rail cars at the following rates: 1,000 amps for one hour,
500 amps for three hours, or 250 amps for seven hours.
(Source: Street Railway Journal, June 1, 1901, pp 665- 666)
Circa 1890's, the Atlantic Avenue RR streetcar company built a power
station for its new electric streetcars. This power station produced
4,400 kW (4.4 MW). This was enough electric power to simultaneously
operate 100 streetcars of 60 HP each. However, those streetcars were
probably only 2 axle vehicles. (Sources: The Power Stations and
Distribution System of the Brooklyn Rapid Transit Company, Street
Railway Journal, October 5, 1901, pp 471-480, and the The Brooklyn
Daily Eagle, November 11, 1892, pg 3.)
Let's now assume a 4- axle streetcar, with a 30 HP motor on each axle.
This gives us 120 HP, or by using the conversion factor of 1 HP= 0.76
kW, gives us 91.2kW for maximum motoring power. Let's now add an
additional 30 kW for Heating, Ventilation and Air Conditioning, as well
as interior lighting. This brings us to an estimated maximum power
demand of 141.2 kW per streetcar, or 235.3 amps at 600 volts DC, on
level track. Let's round this off to 150 kW per streetcar, or 250 amps
at 600 volts DC, maximum power demand. Since streetcars are largely
"free coasting" once set into motion, this peak power demand will only
occur when the streetcar is starting from a dead stop. Because the
proposed streetcar line is relatively short in length, we can probably
assume that only one streetcar at a time will be starting from a dead
stop, and thereby requiring the full 250 amps at 600 volts, or 150 kW.
Taking streetcar "coasting" into account, this 150 kW power demand,
represents the major portion of the Red Hook streetcar line's total
estimated power demand, which I put at 250 kW (416.6 amps at 600 volts
DC). Its assumed that at any given time, 2 of the 3 streetcars will be
drawing about 30 kW each while "coasting", the power being used by
HVAC, lighting, etc., while the 3rd streetcar will be simultaneously
using 150kW, for starting from a dead stop.
Since streetcars spend most of their time "free coasting" on their
rails, rather than wastefully, continuously, drawing motor power when
in motion, 250 kW should be enough to supply ALL of the power demand
for all 3 streetcars (but NOT light rail vehicles) simultaneously.
Now, lets consider where the 250 kW is coming from... This power source
is Solar, using photo voltaic cells to convert sunlight directly into
electricity. Since photo voltaic cells are not very efficient (about
15%), a fairly large surface area directly exposed to sunlight is
required, together with a storage battery array, to produce usable
quantities of electric power 24 hours a day, on demand. Typically, the
photo voltaic array is located on large surface area roof tops. Good
examples, are Brooklyn's Nassau Brewery on Bergen Street, and IKEA on
Beard Street. Photo voltaic arrays have also been successfully located
above parking fields.
As a working example, the expansive flat roof of Red Hook's Beard
Street Pier, could easily provide enough surface area for a photo
voltaic array producing 250kW- or rather much, much more...
If the rooftop of the Beard Street Pier were utilized, there is more
than enough surface area to make the streetcar line 100% Solar Powered.
Together with "regenerative brakes" used on each streetcar (converts
the streetcar's braking force to electric power, which is sent back
into the overhead power wire), ALL of the streetcar line's electrical
power demand could be met with "clean, renewable, solar energy".
The roof of the Beard Street Pier, is roughly 700 feet x 150 ft =
11,666.66 Square Yards. The quantity of "insolation" received at the
Earth's surface is typically 1 kW/ Square Meter. Since a Square Yard is
83.3% of a Square Meter, and photovoltaic cells are roughly 15%
efficient, we can use the conversion formula of 0.833 kW/SY x 0.15 =
0.12495 kW/ SY x 11,666.66 SY = 1,457.749 kW, or 1.457 MW. This is
enough electric power to simultaneously start over 6 streetcars from a
dead stop- this translates to a medium sized streetcar system.
Let's now look at the energy requirements for the Red Hook streetcar.
Assuming our "standard constant" power demand of 250 kW (3
streetcars: 1 car starting from a dead stop, and 2 cars coasting
simultaneously), then 250 kW/ 0.12495 kW/SY = 2,001 Square Yards, or
18,009 ft ², or roughly 120 ft x 150 ft of photovoltaic array,
converting sunlight directly into electricity.
The 250 kW Lithium- Ion Storage Battery Arrays could be easily located
at convenient places along the streetcar route.
| End notes
and other thoughts:
alternative to utilizing batteries (remote power storage) is to use the
power grid for power storage. You could feed the suplus generated
power (during times of most intense sun) into the municipal power
grid. Power could be converted to Ac and fed into the power
grid. Feeding power into the grid would spin the meter
backwards. During hours of darkness, power would be drawn from
the grid instead of added. As you use that power that was
previously fed into the grid, the supply meter spins forward
(eventually back to where it was before power was deposited into the
system). Essentially you could use the power grid as your
battery. Moreover, I believe that in NY, if you produce "clean" power
(from renewable energy), the power company is required to purchase it from