GIS methodology and case study regarding assessment of the solar potential at territorial level: PV or thermal?

This paper presents a GIS-based methodology for assessing solar photovoltaic (PV) and solar thermal potentials in urban environment. The consideration of spatial and temporal dimensions of energy resource and demand allows, for two different territories of the Geneva region, to determine the suitable building roof areas for solar installations, the solar irradiance on these areas and, finally, the electrical and/or thermal energy potentials related to the demand. Results show that the choice of combining PV and solar thermal for domestic hot water (DHW) is relevant in both territories. Actually, the installation of properly sized solar thermal collectors doesn’t decrease much the solar PV potential, while allowing significant thermal production. However, solar collectors for combined DHW and space heating (SH) require a much larger surface and, therefore, have a more important influence on the PV potential.

Hydrodynamic Interaction between an Accretion Flow and a Strong Wind around a Black Hole

In 2015, space heating and domestic hot water production accounted for around 40% of the Swiss final energy consumption. Reaching the goals of the 2050 energy strategy will require significantly reducing this share despite the growing building stock. Renewables are numerous but subject to spatial–temporal constraints. Territorial planning of energy distribution systems enabling the integration of renewables requires having a spatial–temporal characterization of the energy demand. This paper presents two bottom-up statistical extrapolation models for the estimation of the geo-dependent heat and electricity demand of the Swiss building stock. The heat demand is estimated by means of a statistical bottom-up model applied at the building level. At the municipality level, the electricity load curve is estimated by combining socio-economic indicators with average consumption per activity and/or electric device. This approach also allows to break down the estimated electricity demand according to activity type (e.g., households, various industry, and service activities) and appliance type (e.g., lighting, motor force, fridges). The total estimated aggregated demand is 94 TWh for heat and 58 TWh for electricity, which represent a deviation of 2.9 and 0.5%, respectively compared to the national energy consumption statistics. In addition, comparisons between estimated and measured electric load curves are done to validate the proposed approach. Finally, these models are used to build a geo-referred database of heat and electricity demand for the entire Swiss territory. As an application of the heat demand model, a realistic saving potential is estimated for the existing building stock; this potential could be achieved through by a deep retrofit program. One advantage of the statistical bottom-up model approach is that it allows to simulate a building stock that replicates the diversity of building demand. This point is important in order to correctly account for the mismatch between gross and net energy saving potential, often called performance gap. The impact of this performance gap is substantial since the estimated net saving potential is only half of the gross one

Utilisation des échangeurs air/sol pour le chauffage et le rafraîchissement des bâtiments : mesures in situ, modélisation analytique, simulation numérique et analyse systémique

Après définition des problèmes à aborder et description des projets pilotes qui sous-tendent le travail, la première partie pose les bases théoriques et opérationnelles: 1) Rappel des paramètres physiques. 2) Calcul analytique en situation géométrique simplifiée, permettant d'acquérir une bonne compréhension des phénomènes et de dégager les "règles du pouce" utiles à l'ingénieur. Cette approche révèle également un phénomène nouveau et prometteur, le déphasage à amortissement quasi-nul d'une oscillation thermique. 3) Modélisation numérique, permettant d'étendre la capacité de calcul à des géométries plus complexes. La deuxième partie comprenant l'analyse systémique de deux types d'utilisation des échangeurs air/sol: 1) Stockage diurne d'excès solaires en serres horticoles (boucle ouverte), étudié via une importante campagne de mesure. 2) Préchauffage/rafraîchissement par puits canadien (boucle fermée), mettant l'accent sur l'asymétrie fondamentale entre ces deux prestations et posant les bases d'une analyse énergétique complète du couplage d'échangeurs air/sol au bâtiment

Performance gap in building retrofit

The Swiss Energy Strategy 2050 strongly relies on massive reduction of the heat demand for the building sector (45% by 2035, and 64% by 2050). Given the slow transformation of the building stock, focus needs to be set on building retrofit. Understanding and reducing the performance gap between actual (real) and planned (design) energy performance is an essential step towards achieving the energy saving goals. The objectives of this study are: i) Analysis of the energy performance gap in building retrofit on the basis of a representative set of case studies, identification and characterization of the determinant factors and estimation of their impact on the energy performance via sensitivity analysis; ii) Estimation of the actual energy saving potential of the building stock, under current practice; iii) Provide guidance on countermeasures and policy recommendations to reduce the energy performance gap