At present, there are two main problems restricting the development of the integrated design of solar collectors and the appearance of high-rise residential buildings. On the one hand, the solar collectors on the market have poor compatibility with the appearance of buildings. Manufacturers of solar energy products generally only consider the quality and performance of the product itself, and seldom consider the adaptability of the product to the building structure and size of building components. There is little room for selection of collector style, surface texture and color; there is no specialized configuration for supporting components and installation methods required for installation. On the other hand, architects have not paid much attention to the design of solar water heating system, and the understanding of existing solar water heating system products is still very lacking. The installation position of the collector, the position of the pipeline, the embedded parts and the foundation settings are not reserved in the architectural design, and the subsequent installation will cause damage to the original building structure, waterproof and thermal insulation structure; the size and color of the collector are not considered, which affects the aesthetics of the building. Therefore, on the one hand, architects need to gradually increase the importance of solar water heating system subjectively, and take it as one of the contents of architectural design; on the other hand, the development of solar heat collection products should not only focus on the improvement of product performance, but also carry out modification and new product development according to building requirements.

There have been many successful examples of the combination of solar collectors and the appearance of residential buildings in China, but compared with other countries’ related technologies, we still have a big gap in product types, installation technology, and detailed processing. The integration of solar collectors and building appearance can be improved and developed in the following three aspects.

1. Component size matching

The specifications of China’s solar collectors are still produced according to industry standards, with few changes in specifications and poor compatibility with buildings; because the architect did not consider the installation position of the collector at the beginning of the design, the size of the building facade and the collector often did not match. Ideally, the size of the solar collector can be produced in consideration of the conventional size of each part of the building, which can be determined according to the modulus of the building roof or facade, and can be flexibly combined and changed according to actual needs. In the early stage of building design, architects need to understand the size and structure of related collector products, and try to match the size of building components with the size of collector products. At the same time, it is necessary to realize the modularization, standardization and interface standardization of connected devices.

The manufacturer customized a new 95mm U-shaped tube vacuum tube according to the structure size of the building balcony (with CPC reflectors installed on the back, 2.85m² per household), arranged vertically, the vacuum tube is combined with the original solid part like a balcony railing , see Figure 1(a).

Figure 1(b) is a low-rise residence with a combination of evacuated tube collectors and south-facing balcony railings. Each solar collector module consists of 9 evacuated tubes, 90cm high and 2.4m long. It just matches the size of the balcony railing, and is combined with the 90cm wide wooden railing on the side to form a unified and varied facade effect.

2. Diversification of collector products

The shape, color and surface texture of Chinese solar collector products are relatively simple, and architects have little choice for collector products, which restricts their organic integration with buildings. Other countries have made some innovations in this regard. They have carried out a lot of developmental research on the geometry, color and texture of the heat absorbing plate of the solar collector, and successfully developed many solar collectors with different colors and textures. As shown in Figure 2, in Figure 2(a), a selective filter coating is applied to the inner surface of the cover plate of the collector, which only reflects a small part of the solar visible spectrum, and the rest is absorbed by the heat absorbing plate, so that the collectors have different colors; in Figure 2(b), the collectors with different textures are treated with some surface textures on the cover plate, such as showing the arrangement of dots, and showing some characters like printed glass. Under the premise of ensuring the heat collection efficiency of the collector, solar collectors of different colors and textures can stimulate the interest of architects, and there is also a greater choice to use the collector as a means of architectural modeling.

3. Componentization of collectors

The componentization of solar collectors is an advanced stage of the combination of solar collectors and building appearance, which can realize the seamless combination of collectors and buildings. The collector is transformed into building components, such as walls, roof panels, sunshade components, etc., so that the collector has both heat collection and building functions (enclosure, heat preservation, heat insulation, waterproof, etc.), replacing traditional building components. The collector completes the finished product production of standard modules in the processing workshop, and is constructed and installed simultaneously with other building components at the construction site. Some componentized collectors have been briefly described above, such as balcony railings with heat collection function, sunshade louvers, etc., solar collectors and ordinary building components are combined into one, without any additions to the appearance of the building. There are also many manufacturers in China who have tried and developed products such as heat-collecting roof panels, window-type (vacuum tube) collectors, solar thermal tiles, and collector tiles.

In Figure 3, the collector is combined with a special bayonet structure and double glazing to become a unified building module, which is used as a sunshade component. In addition to the heat collection function, the collector can also play the role of shading and light guiding. The building components of the collector products can achieve a good integration effect, but there are also problems such as high price, complex technology, and contradiction between the collector elements and the life of the building, and further development and testing are needed.