the idea is to raise the power generation efficiency , which is now limited to 26 % in the boiler systems that burn hydrogen , to 42 % or more by 1 -rrb- recycling the 20 % or so of hydrogen that is discharged from the fuel cell as is , without being reacted , and 2 -rrb- by using the 170ë water vapor that is produced during the reaction process for energy within the plant .