Page 25 - Fuel Cell Student Edition

To model regenerative braking, create a new miners will have to wait the battery to recharge
column that will use a logical if statement to before proceeding, since time is of the essence, this
regenerate at a rate of 50% the interval mechanical will be considered a failed route. To see where the
energy while the rover is going downhill. This should failure occurs, create a new column called “failure?”.
be a positive number. The rover drive system works If the battery is completely discharged, there will be
by using a fuel cell to charge a high capacity battery. a 1 in this cell, otherwise, there will be a 0. Count the
The battery discharges directly to the drive motors, number of 1’s in this column using the SUM function
providing surge capacity beyond what the fuel cell to determine how many points of failure are along
could provide in short bursts. each route.

To model the battery, make 3 new columns. The The total travel time will be the sum of the interval
first column represents the energy input to the travel times.
battery. This is called “battery charging”. The battery
charging value is the sum of the fuel cell output and If the maximum slope is above the grade climbing
the electrical energy recovered from braking. ability of the rover, the mission will fail. Use the
max function to compare the slope in each interval
The next column models discharging and is called against the maximum slope that the rover can climb.
“battery discharging”. This value is the inverse of the
required energy (a negative result). With the Fuel Cell Power and Slope Test functions
written, it is now a matter of selecting additional
A final column called “total battery charge” is also paths to determine which is suitable for the rover.
needed. Use a logical if statement to limit the You will observe the test cells after each route
battery capacity to its maximum charge. Otherwise, change to determine whether that particular path
the battery charge will be the sum of the previous passes or fails. New routes can be copied and
charge, battery charging, and battery discharging. pasted directly from ImageJ without having to alter
any of the formulas in this spreadsheet, with the
If the battery is discharged below 0, the fuel cell exception of adding or reducing the number of rows
has failed to provide the required demand and the that hold the data.

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