# Converting kW/h to kWh for Optimizing Fuel Cell Ramp-Up

• Ornella
In summary, Ornella is trying to calculate the energy that is used during the ramp-up of her fuel cell, but she gets it wrong. She calculates it using the power that is drawn at the start of the ramp, but the power is actually constant. After finding out the correct time for the ramp-up, she applies the method that she was told.
Ornella
Hi everyone,

I am working on a mathematical optimization model for a fuel cell.
Currently I am facing a problem with the ramp-up of the cell.
I have a modulation ramp of 4% of the nominal power (58.3 kW) per minute.
My constraint in the model has to be in kWh (I have to precise that my model is a hourly simulation during one year).
Concerning the conversion of the power in other constraints (as for FC capacity constraint) I simply multiplied the power times one hour and I should get the energy in kWh.
But for the ramp-up constraint I am really struggling with the conversion.
Anyone that has an idea how to obtain it?

Thanks in advance for any help.
Ornella

Ornella said:
I simply multiplied the power times one hour and I should get the energy in kWh.
That works for constant power. For variable power you have take its integral over time.

A.T. said:
That works for constant power. For variable power you have take its integral over time.
The power is actually constant. I am trying to expand the simulation per every hour of the year. Is it still wrong?

Ornella said:
I have a modulation ramp of 4% of the nominal power (58.3 kW) per minute.
Maybe:
At the start you are drawing no current. Every minute you can increase your power draw by 4% of 58.3kW (= 2.332kW)
After 15min you are drawing the full rated power of 58.3kW.

If you are looking at energy, then, provided the ramp is a straight line (as it usually seems to be),
energy during ramp = average power x time = 1/2 full power * ramp time. = 0.5 x 58.3 x 0.25 kWh

Ornella
Ornella said:
The power is actually constant.
Than what are you measuring in kW/h?

A.T. said:
Than what are you measuring in kW/h?
the energy during the ramp up of my fuel cell

Last edited:
Merlin3189 said:
If you are looking at energy, then, provided the ramp is a straight line (as it usually seems to be),
energy during ramp = average power x time = 1/2 full power * ramp time. = 0.5 x 58.3 x 0.25 kWh
Thank you very much! That's what I was looking for!

Merlin3189 said:
Maybe:
At the start you are drawing no current. Every minute you can increase your power draw by 4% of 58.3kW (= 2.332kW)
After 15min you are drawing the full rated power of 58.3kW.
I actually found out the time for ramp up to be 25 min.

0.04/min * 60 min/h * 58 kW = 139.9 kW/h
58.3 kW / 139.92 = 0.42 h = 25 min
Then I applied the method as you said.
0.5 * 58.3 * 0.42 = 12.5 kWh
Thanks again!

Yes you're quite right. My brain must be withering! 25 minutes at 4% per minute is 100%

Ornella
A.T. said:
Then what are you measuring in kW/h?
Ornella said:
the energy during the ramp up of my fuel cell
Energy is measured in kWh, not in kW/h.

A.T. said:
Energy is measured in kWh, not in kW/h.

I was trying to obtain the energy during the actual time of ramp-up. But I solved my problem.
Thanks anyways.

## 1. What is the difference between kW/h and kWh?

The unit of measurement for power is kilowatts (kW), while the unit of measurement for energy is kilowatt-hours (kWh). kW/h is not a valid unit of measurement.

## 2. Why is it necessary to convert kW/h to kWh for optimizing fuel cell ramp-up?

Fuel cells produce electricity at a certain rate, which is measured in kilowatts. However, to determine the total energy output over a period of time, the measurement must be converted to kilowatt-hours. This is crucial for accurately monitoring and optimizing the ramp-up process of fuel cells.

## 3. How do you convert kW/h to kWh?

To convert kW/h to kWh, simply multiply the number of kilowatts by the number of hours the fuel cell has been operating. For example, if the fuel cell has been producing electricity at a rate of 5 kW for 3 hours, the conversion would be 5 x 3 = 15 kWh.

## 4. Can kW/h and kWh be used interchangeably?

No, kW/h and kWh cannot be used interchangeably. kW/h is not a valid unit of measurement, while kWh is the standard unit of measurement for energy. They represent different quantities and should not be confused.

## 5. How does converting kW/h to kWh help with optimizing fuel cell ramp-up?

Converting kW/h to kWh allows for accurate measurement of the total energy output of a fuel cell over a period of time. This data can then be used to analyze and optimize the ramp-up process, ensuring the fuel cell is operating efficiently and effectively.

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