Once the common areas are defined, the choice of which information to exchange can be made, and it is based on the purpose of the soft-linking. In this thesis the purpose is on the representation of a possible future uptake of hydrogen in shipping. The interest is in learning about the interactions between two represented systems: the energy system that embodies the supply of marine fuels and the hydrogen supply infrastructure, and the
shipping system that embodies the hydrogen technologies on board. Having examined the common area, it is possible to decide on the variables to exchange.
Among the most important variables, there are the quantities of marine fuels con- sumed and their relative shares by regions. The simulation in GloTraM of the projections of future consumption of marine fuels is taken as the true representation, and therefore the quantities and shares are among the variables that need to be exchanged from Glo- TraM to TIAM-UCL. This is linked into the energy model as shipping energy demand. Marine fuels availability and relative prices are other important variables that need to be exchanged. The simulation of fuels availability and price projections under different scenarios is better represented in TIAM-UCL, therefore they should be exchanged from TIAM-UCL to GloTraM. This implies that a decision needs to be made about which marine fuels to include among the options and how to match TIAM-UCL and GloTraM’s fuel options. This discussion is provided in section 4.7.
In TIAM-UCL, carbon price is a possible mitigation option that would vary based on the specified carbon target. This variable has an impact on the voyage cost represen- tation in GloTraM. Moreover the fuel choices made in the shipping industry may have implications on how this variable can vary. If the scope is learning about the interactions between the two represented systems, it is important to include this variable among the ones to be exchanged from TIAM-UCL to GloTraM.
Technology specifications of the shipping fleet could be transferred from GloTraM to TIAM-UCL, however this would result in an addition of complexity in the energy system that would not necessarily provide a more precise answer. The purpose indeed is not the integration of the two models and adding more details to either. Conversely, the purpose is on analysing the interactions between two different systems. This is why the specification of the shipping fleet is not transferred but rather it is simplified in TIAM-UCL. More details on how this is done are given in section4.11.
A more complicated common area between the two models is the trade by ships of energy commodities between different regions. In TIAM-UCL such trades are part of the distribution of energy commodities, which can be seen as a component of the infrastructure of the supply. This component would have its own energy and emission performance, and it would be developed differently based on the specified scenario. At the same time such trade is part of the transport demand in shipping, which is an input assumption in GloTraM. While TIAM-UCL could inform the shipping system about
Chapter 4. TIAM-GloTraM 68
such trade, GloTraM could inform the energy system about the specifications of the fleet that would provide such trade.
Under wider CO2 mitigation scenarios hydrogen can have the potential to reduce the
emissions of a number of energy technologies in the energy system. This could have an impact on the mix of energy resources used, and thus on the future international trade which corresponds to the future transport demand of the shipping system. Therefore this trade should be included among the exchanged variables from TIAM-UCL to GloTraM with the purpose of investigating the effect of this feedback and ensuring a greater level of consistency between the two models.
The specifications of the future shipping fleet can influence the shipping transport costs that consequently can influence the trades within the global energy system. In this thesis these specifications are not transferred from GloTraM to TIAM-UCL because it is assumed that changes in such specifications would have a negligible effect on the trades of energy commodities. On one hand it is recognised that this assumption is a limitation of this version of the model and further research should put more attention regarding it. On the other hand, the effects on the energy system caused by changes of transport costs are not in the scope of this thesis therefore additional developments are left to further research efforts.
TIAM-UCL does not provide carbon or GHG emissions per each pathway in the upstream, rather emissions are calculated by process. An attempt to allocate upstream emissions to a single fuel commodity (hydrogen for shipping) is provided in section6.3.3, however, such upstream emission are not exchanged between the models. Although it is recognised that they should be accounted to demonstrate the overall emissions impact of any potential future marine fuel, the upstream emissions are assumed to be excluded from the objective function of the shipping model. In other words, the shipowner profit maximisation approach assumes that the upstream emissions of any marine fuel are not included in the equation but only fuel price and operational emissions. As a consequence, upstream emission are not exchanged from TIAM-UCL to GloTraM.
Having defined the variables to be exchanged, a number of modifications need to be considered in both models before developing the soft-linking procedures. The variables chosen to be exchanged between TIAM-UCL and GloTraM are: marine fuels demand (quantities and shares), marine fuels options (availability and prices), carbon price, and trade of energy commodities. Modifications were required in both models, in order to
enable the links. Such modifications can be seen as developments applied to a number of assumptions and settings of the models. They regard:
1. the regions definition
2. the common portfolio of fuel options
3. the on board hydrogen technologies
4. the initial conditions on marine fuels demand
Each of these will be described in more detail in the next sections.