benefit E2
Category: publications

benefit E2

Kuhn, Christoph; Wurzbacher, Steffen; Drebes, Christoph

Wurzbacher, Steffen; Drebes, Christoph; Kuhn, Christoph - Parts 1, 2, 3, 4, 5, 7
Müller, Nikolas D.; Pfnür, Andreas - Parts 1, 6, 7

Research report


Link to the research report

The rapidly growing expansion of building-related solar energy use offers the opportunity to become a supporting pillar of a renewable energy supply. At the same time, different reservations regarding the use of applied and technical solar systems ave been expressed by various experts in the building sector. For a further successful expansion of building-related solar energy, adaptive and high-quality system solutions are needed that are economical for the actors involved.

The present research project built on the qualitative interview research of the previous project "benefit E" (AZ: SWD- and the obstacles to the integration of building-related solar systems identified there, and developed strategies and concepts for future solar-adaptive building envelopes. The term "solar-adaptive" refers to principles that enable passive and active solar energy use within an architectural design.

They have the ability to react to specific energy, constructional or design concerns through different configurations. An important aspect here is the consideration of thermodynamic effects of volatile solar yields. Phase shifting and load control are important basic properties of solar-adaptive behaviour. In particular, solar heat and waste heat from solar electricity production can be utilised energetically in different ways. At the same time, solar-adaptive building envelopes must also meet the same economic requirements that are placed on "standard systems" without solar functionality.

The aim of the benefit E2 project was to analyse specific areas of application for solar energy use in different buildings, to design a solar-adaptive principle taking into account the energy, constructional and economic framework conditions, and to present its design bandwidths. Methodically, the four scale levels - building, envelope with constructive component structure as well as construction process and operation - were processed.

For the analysis of application areas and fields of action of solar utilisation, extensive typological investigations were carried out in a first step. Using simulations, specific solar radiation profiles ("solar fingerprint") were generated for the common building types - point-shaped buildings, high-rise buildings, row buildings, courtyard-shaped buildings and halls. The determined energetic and structural parameters were entered into a separate typology catalogue. In parallel with the determination of the radiation potentials of typical buildings, these were quantified in terms of number and proportion of the total building stock. 

In a second step, a solar-adaptive façade principle was designed. This consists of a delicate, pre-hung "façade grid", which can be prefabricated to a large extent and allows maximum design freedom for the architect due to its small size. The "grate" is the supporting structure for an outer and inner layer, which each take on different constructive and design tasks. 

The outer layer serves as weather protection, solar energy generation (active and passive) and individual architectural expression, while the inner layer forms the room closure and consists of an insulation package, fixed glazing or window sashes. The space between the "grille" can encapsulate air or be air-permeable, depending on the energetic goal. A closed layer of air serves to store solar heat as well as waste heat from active solar electricity production. A flow-through, on the other hand, enables the removal of solar heat loads from the interstitial space. 

Depending on the configuration, very different thermodynamic behaviour was assumed in summer and winter. Therefore, dynamic simulations of different component configurations were carried out to determine sensible layer compositions. In addition to a series of varying solar-adaptive polyfunctional façade principles, common "standard" component structures were also simulated. The results of the component-related comparison of variants were also incorporated into the building energy model described below for further evaluation.

For the energetic, ecological and monetary evaluation of integration options for thermal and electrical solar energy, a building energy model was developed in a third step, with which all essential energy flows, including the building's systems engineering, can be mapped. The different configurations could thus also be evaluated in terms of final energy and the resulting CO2 emissions. 

Based on the results of the building energy model, the financial effects of the developed system were analysed using the example of an office building. For this analysis, an interface of essential characteristic data was developed, which made it possible to carry out extensive economic feasibility studies of solar-adaptive façades. A special feature is that the financial effects of solar-active façade elements are modelled on the basis of complete financial plans, thereby depicting the reciprocal effects for owners and tenants. 

The extensive analyses have identified large fields of application for solar-adaptive building envelopes in existing buildings. The new polyfunctional façade principle proves to be flexible in terms of energy and design. By buffering solar heat and waste heat from active systems, heating consumption can be reduced equivalent to insulation measures. The "susceptibility" of solar buffer zones with regard to summer overheating can be largely eliminated by controlled flow-throughs. The results of extensive analyses also show that solar-active façade elements can be economical for owners and tenants and thus contribute to the implementation of the heat transition (energy transition in the building sector). Overall, hybrid solar energy use is seen as having great potential for regenerative energy generation, especially in the façade sector.