Multi Energy Static Modelling Approaches: A Critical Overview

In Europe and elsewhere in the world, the current ambitious decarbonization targets push in the direction of a gradual decommissioning of all fossil-fuel-based dispatchable electrical generation and, at the same time, a gradual increase of the penetration of the Renewable Energy Sources (RES). Moreover, considerations tied to decarbonization as well as to security of supply, following the recent geo-political events, call for a gradual replacement of gas appliances with electricity-based ones. As RES generation is characterized by a variable generation pattern and as the electric carrier is characterized by scarce intrinsic flexibility (load and generation must coincide instant by instant and storage capabilities through electrochemical batteries as well as demand-side flexibility provision stay rather limited), it is quite natural to think of other energy carriers as possible service providers towards the electricity system. Gas networks are characterized by high compressibility (the so-called linepack phenomenon). Hydrogen stays very promising for providing not only daily but also seasonal storage. Heat networks are also intrinsically flexible because characterized by high thermal inertia and able to ensure comfort while varying water temperatures within a wide range of temperatures. All these carriers could, thus, provide storage services for the electricity system and this could allow, in turn, to increase the amount of RES penetration to be managed safely by the system, without incurring in risks of blackouts and without, on the other side, wasting RES generation peaks (or carrying out expensive reinforcements of electric transmission and distribution networks for hosting flows that would materialize only in a very limited number of hours in one year). All this calls for a new approach, both in electricity network dispatch simulations and in grid planning studies, which extends the simulation domain to other carriers (gas, heat, hydrogen…) so that a global optimal solution is sought for. This simulation approach, called multi-energy or multi-carrier, is gaining momentum in the last years and many approaches have been proposed, both in modelling the single carrier components and in joining them together for creating an overall model. The present paper aims at describing the most important of these approaches and comparing pros and cons of all of them. The style is that of a tutorial aimed at providing some guidance and a few bibliographic references to those who are interested to approach this issue in the next years.