Frequently asked questions
Hover over the questions below to reveal the answers
What does Pūhiko Nukutū mean?
Pūhiko Nukutū means Earth Battery. Pū is a bunch, indice or power, and hiko is the kupu (word) for electricity. Therefore, a pūhiko concentrates electricity within itself, like a battery. Nukutū is an alternative to Papatūānuku, meaning Earth Mother. The creation story describes the separation of Ranginui (Sky Father) and Papatūānuku (Earth Mother).
During periods where surplus energy is being produced, hydrogen can be injected into a Pūhiko Nukutū/Earth Battery and stored. When more energy is required (e.g., during a 'dry year' - when our hydropower lakes don't receive enough rainfall), hydrogen can be discharged and utilised to create electricity.
Is underground hydrogen storage safe, or will it explode?
While hydrogen is a highly flammable gas, an oxygen-rich environment is required for combustion to occur. Deep underground there is just not enough oxygen present within the tiny gaps in the rocks for hydrogen to combust. The major safety risk with underground hydrogen storage is production of hydrogen sulfide gas. Our team is looking into how microbes might cause this to occur and much could be generated.
Why store hydrogen underground?
Hydrogen is an extremely low density gas. One kilogram of hydrogen occupies 30 times the space of one kilogram of water, so the biggest challenge is finding enough space to hold it all. We'd need about five million tanks if we were to place our projected hydrogen capacity all on the surface. Underground gas fields solve the problem of storage; these huge geological formations can store many millions of cubic metres of hydrogen.