Bottom-up Lumped-parameters Thermodynamic Modelling of the Italian Residential Building Stock: Assessment of High-resolution Heat Demand Profiles F. Lombardi 1 , M.V. Rocco 1* , S. Locatelli 1 , C. Magni 1 , E. Colombo 1 , L. Belussi 2 , L. Danza 2 1 Department of Energy - Politecnico di Milano, Via Lambruschini 4, Milan 20156, Italy 2 Construction Technologies Institute - National Research Council of Italy (ITC-CNR), Via Lombardia 49, 20098, San Giuliano Milanese (MI), Italy Corresponding Author Email: matteovincenzo.rocco@polimi.it https://doi.org/10.18280/ti-ijes.632-434 ABSTRACT Received: 13 February 2019 Accepted: 26 April 2019 Final energy demand of residential sector accounts for about 25 % of the overall final consumption in the European region, mainly driven by space heating, space cooling, domestic hot water and cooking, which represent about 85 % of the total. Definition of effective policies towards decarbonisation of heat demand have been hindered so far by the lack of temporally- and spatially-detailed heat demand profiles, a key input for energy system optimisation models. This study tries to fill this gap by designing and validating a bottom-up thermodynamic lumped-parameters model for the Italian building stock. More specifically, the model grounds on a resistance-capacitance thermodynamic model, defined for: four building archetypes, five periods of construction and six building typologies corresponding to different climate zones. The model is applied to Italy and results classified based respectively on regional and hourly space and time resolutions. The model is validated based on temporally aggregated regional data. The model is used to assess the consequences of alternative building refurbishment/new construction scenarios towards Nearly Zero Energy Buildings (nZEBs), defined according to official Italian policy strategies: for each scenario, the change in heat demand and the change in share of appropriate domestic heating supply technologies are evaluated. Finally, sensitivity analysis is performed on the most critical parameters of the model. Keywords: residential building stock, heat demand, thermodynamic building model, energy modelling, nearly zero energy buildings 1. INTRODUCTION The integration of multiple energy sectors (power, heat, transport) into a multi-energy systems configuration is widely recognized as a pivotal prerequisite for fostering the penetration of renewable energy sources in the energy mix, in compliance with Paris Agreement decarbonization targets [1]. To this end, most profitable results and synergies can be experienced by acting on the residential heat demand [2]. The final energy demand of residential buildings accounts, in fact, for about 25 % of the overall final consumption in the European Union, primarily driven by heat loads: space heating, space cooling, domestic hot water and cooking represent up to 85 % of the total residential energy use in European Union (EU) [3]. Such energy uses present several opportunities for rapid and cost-effective sector-coupling and decarbonisation policies, such as the replacement of traditional heating technologies with highly-efficient heat pumps coupled with thermal storage [4] and the refurbishment of old buildings towards Nearly Zero Energy Buildings (nZEBs) [5]. Nonetheless, the residential heat sector presents several complexities and site-specific dynamics, which need to be carefully understood and assessed in order to design effective policies. The lack of clear, country-wide analyses demonstrating the synergies and benefits that may be ensured by heat-electricity integration and nZEBs diffusion at the Italian level has hindered so far the design of decarbonisation policies in this direction [6]. In fact, despite the increasing spatial and temporal resolution and the capability of integrating multiple energy sectors ensured by a new generation of open-source energy models (e.g. Calliope, Dispa-SET, oemof) [7], there is still a significant lack of corresponding detailed current and prospected residential heating and cooling demand profiles, required as a key input to such models. In most contexts, heating and cooling energy uses are not metered (preventing the use of experimental data), whilst models for their synthetic generation are hardly available at the required spatial scale and level of aggregation (i.e. regional or national) [8]. The most recent literature tries addressing this gap by designing country-wide bottom-up building stock models, allowing for a high degree of control and customisability (including simulation of future changes due to refurbishment), while also ensuring a good accuracy. For instance, Protopapadaki et al. [9] propose a Modelica- based implementation of a bottom-up model of the Belgian building stock, generating aggregate heating and cooling loads for different building archetypes with a high temporal resolution. Gendebien et al. [10] perform a similar analysis for the same context, but relying on lumped-parameters building archetypes for a more computationally-efficient aggregate simulation, accounting also for alternative refurbishment scenarios. Following a similar methodology, Patteeuw et al. [11] demonstrate how bottom-up models based on thermodynamic lumped-parameters building archetypes also entail the potential for a hard-linked integration with energy system models, enabling heating and cooling demand profiles TECNICA ITALIANA-Italian Journal of Engineering Science Vol. 63, No. 2-4, June, 2019, pp. 349-356 Journal homepage: http://iieta.org/Journals/TI-IJES 349