(62b) Large Scale Deployment of Low Carbon Hydrogen and CCS Value Chains for the Decarbonisation of Heat: Novel Methods and Insights

Authors: 
Sunny, N., Imperial College London
Mac Dowell, N., Imperial College London
Shah, N., Imperial College London
Growing environmental pressures have resulted in concerted research efforts into the deployment potential of hydrogen (H2) networks for many applications. It is generally construed that the optimal production pathway for a H2 network is dependent on the availability of carbon capture and storage (CCS) at scale [1], [2]. In particular, large scale methane reforming with CCS is the prevalent vision for H2 production in a carbon constrained environment [3]. However, there has been little progress in defining the necessary criteria for truly having “low carbon” H2 through such pathways. The Department for Business, Energy and Industrial Strategy (BEIS) in the United Kingdom (UK) highlights a key gap in current understanding through the following statement “The extent to which methane leakage could undermine greenhouse gas reduction is uncertain and requires further analysis”[4]. The purpose of this study is to evaluate the systemic potential of low carbon, H2 production and CCS technologies for the decarbonisation of domestic and industrial heat. This study addresses the aforementioned research gaps and further identifies and elucidates a set of generalisable engineering considerations that favour the eventual usage of a H2-CCS solution within a geographical context. The quantification of economic and environmental trade-offs in transition from natural gas-based infrastructure to H2 forms the core of this study. In particular, the interdependencies of a H2-based solution with the existing natural gas/ electricity grid infrastructure and negative emissions technologies (NETs) are studied to determine the infrastructural potential for alternate production pathways. The mathematical model used for these analyses comprises of a mixed integer linear program (MILP) based on the Resource Technology Network (RTN) framework introduced by Pantelides [5].

The models have been developed with a comprehensive description of all network components within both H2 and CO2 value chains. A discrete spatio-temporal description of the geographical region of Great Britain is used for illustrating the key factors in the design of nation-wide H2 infrastructure. Technological options such as biomass gasification with CCS, steam methane reforming and auto-thermal reforming with CCS and water electrolysis are compared in different configurations and scales to identify an optimal strategy for the supply of heat, given the distribution of incumbent infrastructure and available production technologies at scale. Further investigations explore the value of H2 storage in underground geological caverns, study trade-offs associated with long distance transmission of H2 against local distribution, etc. The effect of model uncertainties, such as a relatively coarse representation of time, on optimal infrastructure design are studied via a multi-stage optimisation formulation with increasingly finer representations of time. This provides clear indications of the operability limits in the designed networks and enables planning of additional capacity requirements. A novel model instance was developed to provide a phased development trajectory of conversion from natural gas to H2 through the introduction of a new set of binary decisions. Typically, multi-period time formulations are used in this context, however, severe computational limitations are present in cases when very high spatially resolved outputs must be defined. In contrast, the model variation in this study combines a snapshot model solution with an iterative strategy to incrementally define regions of conversion and associated infrastructure requirements at high computational speeds. Results indicate pathways with methane reforming and biomass gasification with CCS as the dominant technological choices, given sufficient CO2 storage availability. The total annualised costs increase significantly in the absence of cavern storage of H2, nevertheless, favourable alternate production technology configurations are highlighted for supplying peak demands in such areas.

[1] Dynamis Consortium, “Near-Zero Emissions from Electricity and Hydrogen Production with CO2 Capture and Storage (CCS) ,” vol. 2011, no. 05/29, p. 24, 2009.

[2] J. C. Meerman, E. S. Hamborg, T. van Keulen, A. Ramírez, W. C. Turkenburg, and A. P. C. Faaij, “Techno-economic assessment of CO2 capture at steam methane reforming facilities using commercially available technology,” Int. J. Greenh. Gas Control, vol. 9, pp. 160–171, Jul. 2012.

[3] Northern Gas Networks, Equinor, Cadent, “H21 North of England Report,” 2018.

[4] Department of Business Energy and Industrial Strategy (BEIS), “Clean Growth - Transforming Heating - Overview of Current Evidence,” 2018.

[5] C. C. Pantelides, “Unified Frameworks for Optimal Process Planning and Scheduling,” no. 1994.