Balancing efficiency and renewables in the federal building strategy: Results from modelling potentials and restrictions in a national heat market with high spatial resolution

摘要

In the discussion of the nearly zero energy building stock, an important question is the right balance between energy efficiency (EE) measures and renewable energy sources (RES): Whereas the “efficiency first” principle requires lowering the building energy demand prior to implementing a RES supply, other stakeholders argue that RES are available cheaply and abundantly and could help avoid deep interventions in the building stock.Within the context of the German Federal Building Efficiency Strategy (ESG), a detailed modelling of the German building target (minus 80 % nonrenewable primary energy demand until 2050) has been carried out by the authors, identifying the restrictions and potentials of EE measures based on detailed statistical, GIS based and empirical information. Guiding questions were: What is the absolute minimum of U values of buildings from a technical, life-cycle and economic point of view? Which reduction of energy demand can be achieved? How long will the refurbishment of the whole building stock take at least? In addition to this EE perspective, the rather generic studies of RES potentials available in the literature were critically re-assessed, trying to improve the data quality of the potential contribution of RES to the target. This implies detailed, spatially resolved analyses of solar thermal energy, heat pumps, biomass, and district heating.Two building models were combined to answer the questions: first, the geodata based ‘German Heat Atlas’ WaD which allows locating energy demand on a single building level, including EE (e. g. historic or semi-renovated buildings) and RES restrictions (e.g. inadequate locations for geothermal heat pumps or heating networks), and second the building scenario model GEMOD which calculates the future development for different conditions. The combined models allowed detailed analyses of RES whose potentials depend on the density of heat demand or building density, such as district heating, deep drilling geothermal energy and brine/water heat pumps. The potentials of solar heat and biomass were quantified by regarding their specific restrictions.As a major result, one can state that there is only a narrow corridor left to reach the 80 % target within the technical boundaries. This requires about 50 % reduction of energy demand combined with 60 % renewable heat generation. Moreover according to the COP21 targets, it will be necessary to enhance the ambition of the building sector. The model results show that assuming the foreseeable technology evolution, such a decarbonisation target will hardly be achievable with EE and RES. To reach the target nonetheless, it is necessary to implement sufficiency as a third strategic dimension.