I am running an electrolyzer which produces hydrogen gas and measured in milli liter. In order to find the efficiency, HHV must be known as J/ml. There are values in textbooks given in 39KWh/kg, 141Mj/kg and 12.7 Mj/m^3.
How to convert this to J/ml of hydrogen?
You will have to look at a value under normal conditions (I assume you also look at the gas under normal conditions) . If the value of 12,7 MJ/m^3 is under normal conditions, you divide it by 10^6 to get a value in MJ/ml and then multiply it with 10^6 to get a value in J/ml. In other words: a value of 12,7 MJ/m^3 equals a value of 12,7 J/ml (under equal conditions).
Hello, be careful about volume unit. For conversion of volume unit to mass unit you need to know also pressure at which the volume unit were obtained.
Thanks for this help Sheikh Adil Edrisi
and Robert Gerard van de Ketterij .I am running the electrolyzer under normal pressure but the temperature may slightly varry but that is not a big problem as the uncertainty will always exist.
If 1 ml of hydrogen yields only 12.7J then i get very low efficiency as follows:
Efficiency= out put energy / input energy= 35ml*12.7 / 31*0.200*20*60 s
Where 35 ml of hydrogen gas produced during 20 minutes (time) of experiment for which the voltage was 31V ( DC power source) and 0.200A is the average current flow into the electrolyzer through the electrolyte.
The efficiency i get is around 5%.
Dear Javad Hikmati
The following link may help you.
https://h2tools.org/hyarc/calculator-tools/lower-and-higher-heating-values-fuels
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