|ETI modelling, using its Energy System Modelling Environment (ESME), shows that flexible power generation systems comprising hydrogen generation with CCS, intermediate hydrogen storage (particularly using salt caverns) and flexible turbines are attractive components in a future UK energy system. In such a system, hydrogen is supplied from coal and biomass fired gasifiers and steam methane reformers, with CO2 captured for storage - see Figure 1 below for hypothetical layouts. This permits the use at high load of capital intensive and relatively inflexible conversion and CCS equipment, filling hydrogen storage when power is not needed, and releasing hydrogen at short notice through turbines when power is at a premium. Superficially there are no barriers to using salt caverns as stores, as such stores are in use in the USA. However these are for high value added applications andnot for use in power where loss of efficiency is a more serious drawback. The ETI currently lacks sufficient data and knowledge to build a good representation of costs or efficiency (particularly relating to hydrogen storage) in ESME.
The purpose and focus of the proposed project is:
The first activity in the project (WP1 – see below for further details) is to characterise the requirements for storage for “power scale” use, in termsof offering tactical (diurnal) or strategic levels of storage (and what that means in terms of a delivery pattern of hydrogen) and to estimate what storage pressures are of interest.
- To improve the ETI’s understanding of the economics of flexible power generation systems comprising hydrogen production (with CCS), intermediate hydrogen storage (e.g. in salt caverns) and flexible turbines;
- To focus on the potential, economics and technical requirements for salt cavern storage and flexible turbines, to enable refinement of the ESME model in order to confirm or adjust ESME findings.
The second exercise (WP2) is to find out where in the UK suitable salt structures exist, and how much storage there might be. “Suitability” will not just depend on rock quality, but on depth (pressure) and location. This will enable calculation of scalable costs for UK design types. This data will be of general use, to potentially examine the economics of different configurations around a store. It will be necessary to check, for example, whether or not use of a cavern as a hydrogen store represents better value than, say, a natural gas store or a CO2 buffer store (which would also stabilise CCS flows).
The project will include a number of supporting studies (WP3) to provide context on the main thrust of the project: these will be brief and based on existing studies.
The outputs from WP1 - 3 will then be used to confirm the most favourable configuration (WP4) and/or identify any new ones. Provided these initial studies confirm the anticipated benefits of using hydrogen storage, the project will proceed via a Stage Gate following WP4 to model a representative system at high level and stress test the application in WP5.