Hydrogen: 9-1

Please see the article attached hereto, especially the highlighted sections, and provide more information regarding the proposed hydrogen tube trailer/generation, and all related safety issues, including responses to the claims set forth in the attach

Hydrogen cooling of electric generators is a well-established technology that has been in use in the power industry for decades. The electric generators to be installed at the Clear River Energy Center (“CREC”) will utilize hydrogen gas for cooling the generator rotor and windings.  The hydrogen gas is circulated through an internal heat exchanger in the generator where the heat in the hydrogen is transferred to a cooling water system.  A small amount of hydrogen will leak through the shaft seals of the generator over time, requiring that additional hydrogen gas be fed to the generator.  The hydrogen gas will be supplied from a bank of compressed gas cylinders or, alternately, larger tube cylinders mounted on a truck trailer. 

It is important to note that the CREC is a new power generation facility and will be constructed in accordance with all current codes and National Fire Protection Agency (“NFPA”) recommendations regarding the storage and handling of hydrogen gases and the avoidance of hazardous conditions in the equipment, systems, and applicable areas of the plant.  The referenced article (published in 2008) accurately discusses the hazards associated with the use hydrogen for generator cooling and also describes appropriate safety measures and standards to address these hazards.  These safety measures and standards are incorporated into the design of new power generation facilities.

Of the alternates for supply of hydrogen (i.e. use of hydrogen generators or compressed storage of hydrogen gas delivered to the site), the CREC will not utilize hydrogen generators.  Given the volume of hydrogen to be used and the frequency of delivery, the use of compressed gas cylinders or tube trailers is more economical.  Hydrogen generators require additional operation and maintenance requirements and also increase the possibility of hazards by introducing another process step within the hydrogen system.

Fire and explosion hazards are controlled by appropriate design and operating procedures. These include prevention of the formation of combustible fuel-oxidant mixtures and removing potential sources of ignition (electric spark, static electricity, open flames, etc.) in areas where the hydrogen will be used. Designing enclosures and buildings  contain hydrogen with adequate ventilation will  reduce the possible formation of flammable mixtures in the event of a hydrogen leak.

To prevent the formation of flammable mixtures, the generator will be purged of hydrogen before opening the system to atmosphere, and purged of air, oxygen, or other oxidizers prior to admitting hydrogen into the system.  The hydrogen control system will automatically purge the generator using carbon dioxide gas (a non-oxidant inert gas) to remove the hydrogen.  When the generator is in operation, the hydrogen storage and supply system is designed to automatically maintain the correct hydrogen pressure and purity of hydrogen.  The hydrogen purity will be controlled to a level where an explosive mixture is not present, (i.e. 99.99 percent pure) which is greater than the explosive mixture range of hydrogen and oxygen, thus providing a measure of safety.

Pressure relief devices (“PRDs”) are employed in the compressed gas storage system to reduce the likelihood of cylinder and tube failures during the unlikely event of a fire.  These devices often include frangible disks, fusible metal plugs or pressure relief valves to relief the pressure in a controlled manner through a vent system to avoid a rupture of the container and release of the hydrogen.

As recommended by codes, the hydrogen cylinders will be located away from high traffic areas and normally occupied spaces.  A dedicated concrete pad will be constructed next to the cylinders for a tube trailer (hydrogen delivery truck) as a back-up source of hydrogen.  Protective bollards will be installed around the cylinders and the tube trailer pad for protection from vehicular traffic.  Hazard signage will be placed around the hydrogen storage containers to emphasize safe practices in these areas.