*3.5. Photovoltaic Panels and Esthetical Issues in Buildings*

The growing popularity of solar photovoltaic systems has created new problems regarding esthetic values. The unstoppable trend toward the installation of solar systems on building envelopes, especially the first-generation PV panels, evoked ambiguous opinions from architects. The esthetic effects of PV assemblies mounted on buildings were criticized. Two decades ago, the issue of esthetics concerning the "solar design" was raised. Then, some steps should have been undertaken to modify the appearance of PV panels so that they would not only generate electrical energy but also have visual appeal and blend in with their surroundings [33] (p. 1). At that time, voices stated that the esthetic qualities of the buildings continued to be a largely unsolved problem.

Typological studies of building skins are still lacking, which would be an important basis and evaluation tool for the visual integration of solar technical systems. They should be visually integrated into the overall architectural concept [29] (p. 60). Innovative PV systems of the second and third generations are much less controversial than conventional PV panels, as they can be easily integrated with building components, being available as roof tiles, window glass, or facade finish panels replacing other typical materials. This assortment has changed the attitude of designers toward solar systems because they can be hidden or visually blended in with the background. The esthetics issues in the case of solar buildings require a wider perspective to be discussed. A new kind of esthetic for the built environment has been suggested that explicitly teaches people about the potentially symbiotic relationship between culture, nature, and design. This is a powerful approach since new ideas are learned most rapidly when they can be expressed visually and experienced directly. This esthetic is called visual ecology and is opposed to the method of designing that hides natural processes and related technology out of the public view [34] (pp. 188–189).

Well-articulated ethics have not been developed for sustainable designs, neither has the environmental movement in general, with its various ethics on biodiversity, animal rights, stewardship, intergenerational ethics, and holism [35] (p. 83). A sustainable design gives people a beautiful experience of nature through highlighting the elegance of its processes. It may also forward the interaction of these processes with the patterns of space in the design, revealing the beauty of their connections [35] (p. 115). Something can be considered beautiful if it reveals how it changes over time, especially toward a greater integration, order, and complexity [35] (p. 119).

Solar systems fall into this philosophy. Many examples exist of buildings with conspicuous disharmoniously contrasting surfaces of installed PV modules and the covering materials of pitched roofs or facades. The rectangular or even irregular compositions of PV modules are negatively assessed against the backdrop of roof materials in colors significantly different from the black or deep-blue tones of typical monocrystalline panel materials (Figure 13). Such disharmonized color compositions usually appear on existing houses covered with ceramic tiles. Novel photovoltaic panel systems, as innovative organic cells and nanocrystals, offer interesting color effects for the panels [36]. They are available in a much richer palette of colors and tones and can offer a remedy to this problem as an appropriate color choice can reduce unwanted contrasts, but unfortunately, they are of a much lower energy efficiency (Figure 14). Darker colors of panels absorb solar radiation better and therefore are better in this regard. Multicolored glass–glass (MCGG) and crystalline silicon cell (c-Si) PV laminates are an approach to overcome some of these issues and achieve aesthetically pleasing, yet technically and economically viable, building-integrated PV systems [37] (p. 2).

**Figure 13.** Disharmonious color composition on the building's roof covered with red ceramic tiles and monocrystalline PV panels (photo by W. Celadyn).

**Figure 14.** Harmonized color composition on the building's roof with the application of a new generation of color PV panels (computer simulation by P. Filipek).

Some new methods are available for computationally matching the color of PV panels with roof covering materials. This procedure can achieve a perfect match [33] (p. 9). It is not only the issue of disharmonious colors; controversies exist over the excessive differences in the texture of shiny PV panels and matte roofing materials, which can substantially modify the originally well-matched colors.

Products are, by their very materiality, transient; their usefulness is unavoidably a function of time. They become obsolete for a variety of reasons, all of which help fix a product in a specific timeframe [38] (p. 139). PV panels are automatically associated with recent times and their installation on old-looking roof coverings or facades also creates a disharmonious and anachronic image. Photovoltaic panels are conspicuous technological components on building facades and roofs. This initiates an interaction between architecture and technology, which produces much controversy over the issue. Certain viewpoints state that they continually redefine each other. Depending on the type of applied solar systems and the way they are installed, they can define a high-tech or eco-tech aspect of a building,

both considered opposite to each other [39] (p. 7). As the novel color PV modules offer many new unconventional esthetic opportunities, the possible integration of this technology and building envelope facilitates the approach of the built environment to the promoted eco-tech esthetics.
