How scalable is this as a hydrogen storage option? How much depleted uranium is available for this purpose? How much hydrogen can be stored in this way?

  • The DU hydride compounds can chemically store hydrogen at twice the density of liquid hydrogen.  The volumetric density of hydrogen (H2) in uranium metal hydride (UH3) is NH (1022 atom.cm-3) compared to 4 NHfor liquid hydrogen stored at 20 Kelvin.

  • DU can also quickly give-up the stored hydrogen simply by heating it, which makes it suitable for a reversible hydrogen storage technology. 

  • As a hydrogen storage medium DU is very scalable. The commercial practicalities of the bed design will be explored during the Phase 2 Demonstration to optimise the design for manufacturing, transportation, operation and decommissioning.

  • As a commercial application, HyDUS will use stocks of depleted UF6 Tails which is produced as a by-product of the uranium enrichment services of URENCO in the UK. This would need to be converted to DU for the commercial deployment of HyDUS.

What is the round-trip efficiency of this storage option?

  • The objective of the BEIS funded demonstration project is to prove and calibrate the round-trip efficiency: taking electricity to generate hydrogen through a standard commercially available electrolyser; store the hydrogen in the HyDUS beds; and to then release the stored hydrogen to feed a commercial fuel-cell to generate electricity.
  • The demonstrator will also optimise the overall system design (pipes, instrumentation, pumps, heat integration), that will in turn contribute to improving round trip efficiency.
  • Estimates from the Phase 1 Feasibility Study of the HyDUS project indicate that the electricity-to-electricity round-trip efficiency of the solution is competitive with the efficiency of a gas engine peaking plant, and that with design optimisation from the Phase 2 Demonstration this could see a two-fold improvement. The way in which these characteristics create commercial value will be developed and assessed for the demonstrator design.
  • In addition, key opportunities that the HyDUS project intends to demonstrate include:

    – Stable storage with no volume degradation over time at ambient conditions;

    – Technology deployable at a range of suitable locations;

    – Compact storage due to large volumetric energy density of DU metal hydride; and

    – High purity hydrogen output at 99.999% H2 content.

How much heat is needed to extract the hydrogen from the hydride? What temperatures are required and can waste heat from nuclear facilities be used?

  • For the hydride to decompose and hydrogen to be given-off, the temperature in the bed is raised from ambient to 400 – 450°C.

  • When this temperature range is reached, the pressure of the system is expected to be in the range of 0.5 – 2 bar.

Are you able to provide a chemical formula of the process, eg UH3 + H2 UH5?

  • The introduction of hydrogen over a large surface area of U-metal is a reversable reaction of the form:

    – 2 U + 3 H2 ⇌ 2 UH3

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