Efficiency of a hydrogen fuel cell

In summary, the conversation discusses the calculation of efficiency for a small hydrogen fuel cell. The power in is measured by the voltage and amperage, while the power out is determined by the force and velocity. The efficiency is calculated by dividing the power out by the power in and multiplying by 100%. However, the accuracy of the calculation is questioned and may need to be adjusted for factors such as time and force measurement.
  • #1
redsox5
40
0
I'm trying to calulate the efficency of a small hydrogen fuell cell that I built. I have all of the measurements, but I'm not coming up with a resonable effiency.





The power to electrolyze the water is the P IN.
3.25 W =2.5 V x 1.3Amps (.21 mA)

We measured the electrical power out finding the voltage and amperage.
P OUT = V x I
2.01 x 10^-4 W=.96 V x .00021 AMPS (.21 mA)

I caulcate the force to be 1.421 N


Then I take the electrical P Out and use it as the P IN for the car

the P IN for the car is the electrical P Out

and the P Out for the car is F x V

To find the % efficiency:


The avg velocity is .0198 m/s

For the car: (there is something wrong here since I'm getting more power out)

P in = 2.01 x 10^-4 W
P Out = F x V
2.81 x 10^-2 J = 1.421 N x .0198 m/s

I'm coming up with an unreasonable calculation

Isn't watts joules per second. Should I be including the time it took to electrolyze the water. I'm just using the formula i was given, but the units don't work out

Also I'm not sure if I'm calculating the force in th right way. We used a spring scale and my measurement was .160 kg. I'm I just supposed to multiply that by 9.8 m/s^2. I know that this way gives me Newtons, but the car isn't being affected by gravity anyways. If someone could look this over I'd appreciate it.
 
Physics news on Phys.org
  • #2
The calculation you are using is not correct. The power in for the car is the same as the power out from the electrolysis, and the power out for the car is the force times the velocity. Efficiency is calculated by taking the power out divided by the power in and multiplying by 100%. In this case, the efficiency would be:Efficiency = (2.81 x 10^-2 J / 2.01 x 10^-4 W) * 100% = 140% This efficiency is not possible since it is greater than 100%. To get a more accurate measurement, make sure to factor in the time it took for the electrolysis to occur and also make sure that the force is calculated correctly.
 
  • #3


Dear researcher,

Thank you for sharing your progress in calculating the efficiency of your hydrogen fuel cell. It appears that you have encountered some difficulties in your calculations, and I would be happy to provide some guidance to help you achieve a more accurate result.

Firstly, it is important to ensure that all units are consistent in your calculations. As you correctly pointed out, watts are joules per second, so it may be helpful to convert all your values to joules before continuing with your calculations. Additionally, it may be helpful to include the time it took to electrolyze the water in your calculations, as this could affect the overall efficiency of the fuel cell.

In regards to calculating the force, it is correct to multiply the mass by the acceleration due to gravity (9.8 m/s^2) to obtain the force in Newtons. However, in this scenario, it may be more accurate to measure the force using a dynamometer rather than a spring scale. This will provide a more precise measurement of the force exerted by the fuel cell.

Finally, it may be helpful to review the overall efficiency formula for a fuel cell, which is the ratio of the output power to the input power. This can help you double check your calculations and ensure that your result is reasonable.

I hope this information helps you achieve a more accurate calculation of the efficiency of your hydrogen fuel cell. Keep up the good work in your research!
 

1. What is a hydrogen fuel cell?

A hydrogen fuel cell is an electrochemical device that converts the chemical energy of hydrogen and oxygen into electricity, with water as the only byproduct. It operates like a battery, but can be continuously recharged by supplying hydrogen and oxygen.

2. How efficient is a hydrogen fuel cell?

The efficiency of a hydrogen fuel cell varies depending on the type and size, but on average, it has an efficiency of 40-60%. This means that 40-60% of the energy produced by the fuel cell is converted into electricity, while the rest is lost as heat.

3. What factors affect the efficiency of a hydrogen fuel cell?

The efficiency of a hydrogen fuel cell can be affected by various factors such as the type of catalyst used, the temperature at which it operates, and the purity of the hydrogen and oxygen used. Additionally, the design and materials of the fuel cell can also impact its efficiency.

4. How does the efficiency of a hydrogen fuel cell compare to other energy sources?

Compared to traditional combustion engines, hydrogen fuel cells have a much higher efficiency, as combustion engines only convert about 20-30% of the energy from fuel into mechanical energy. However, the efficiency of a hydrogen fuel cell is still lower than that of lithium-ion batteries, which can have an efficiency of up to 90%.

5. Can the efficiency of a hydrogen fuel cell be improved?

Yes, there are ongoing research and development efforts to improve the efficiency of hydrogen fuel cells. This includes exploring new catalyst materials, optimizing the design and operation conditions, and increasing the purity of the reactants. As technology advances, we can expect to see even more efficient hydrogen fuel cells in the future.

Similar threads

Replies
4
Views
703
  • General Engineering
Replies
11
Views
2K
  • Mechanics
Replies
1
Views
963
  • Mechanical Engineering
Replies
10
Views
2K
Replies
7
Views
882
  • Materials and Chemical Engineering
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
664
Replies
7
Views
2K
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
8K
Back
Top