Due to the large consumption of fossil energy, it leads to a series of social problems troubling human beings, such as energy crisis, environmental pollution, greenhouse effect and so on. It is urgent for people to find a kind of renewable energy which does not pollute the environment to provide the energy that people need, instead of the traditional fossil energy. Solar energy is favored by people because it is inexhaustible and does not pollute the environment during use. On a yearly basis, the solar energy radiated to the earth’s surface is equivalent to the energy released by burning 130 trillion tons of standard coal. Therefore, solar energy is the most attractive renewable energy nowadays. In the background, the photovoltaic building integrated (BuildingIntegratedPhotovoltaic, BIPV) arises at the historic moment. The concept of BIPV was first proposed by American scholars in the late 1970s. Due to the advantages of BIPV, such as environmental protection, no extra space, aesthetics and so on, scholars from various countries have carried out researches on BIPV technology. The original form of simply stacking photovoltaic arrays on buildings has been developed into the design of integrated photovoltaic system and buildings.
Basic concept of photovoltaic building integration
BIPV is a combination of existing buildings and solar power installations, which can generate photovoltaic power while assuming the functions of traditional buildings, providing part of the electricity for the load. In addition, for crowded big cities, combining photovoltaic power generation technology with housing construction can save more space and realize photovoltaic power generation at the same time. Therefore, photovoltaic building integration in urban use, has important value and significance.
Integrated classification of photovoltaic buildings
From the type of combination of photovoltaic power generation technology and buildings, photovoltaic building integration can be divided into two types: (1) photovoltaic power generation equipment is the type of additional system of buildings. This type is usually based on an existing building, adding photovoltaic power generation equipment to the surface of the building. In the early stage of photovoltaic building integration technology, this type is quite common. This type of photovoltaic building integration has the advantages of easy transformation, small investment, convenient construction; However, its disadvantages are also obvious, usually after the transformation of the building appearance and architectural design style is not coordinated, the vision is not beautiful, it is difficult to achieve the ideal effect. (2) The type of photovoltaic power generation equipment integrated with buildings. This type of photovoltaic module is usually a part of the building. In the whole design process of the project, the photovoltaic module and the building are considered at the same time, and the construction and installation are also carried out at the same time, so as to achieve the perfect combination of photovoltaic power generation equipment and the building. It has the function of power generation and construction equipment at the same time.
The application of photovoltaic building integration
BIPV systems can operate in different modes, either connected to the grid or independently used off the grid. In grid-connected use, when the generating capacity exceeds the local load, the excess electric energy can be sent to the grid; on the contrary, when the generating capacity is insufficient, the electric energy from the grid can be used. Independent BIPV is usually suitable for remote, sparsely populated grassland, desert and other areas where the power grid is difficult to access. At the same time, when the sun is in good condition, the surplus electricity produced by the BIPV system can be stored by special energy storage equipment for use when the light is poor, so as to achieve self-sufficiency.
Photovoltaic building integrated installation form
Photovoltaic modules can be assembled into the customer’s requested style, partial or whole replacement building components. The style of the system installation is determined by the performance of the photovoltaic modules selected, the architectural form designed by the architects, and the climatic conditions of the project location. The performance of photovoltaic modules plays a decisive role in the whole design process. At present, the installation forms of photovoltaic building integration are mainly as follows:
Awning type photovoltaic power generation system
FIG. 1 shows the sunshade type photovoltaic power generation system. The photovoltaic panels of this system are mainly installed in the form of sunshade facilities.
Tile photovoltaic power generation system
Figure 2 shows the tile photovoltaic power generation system. As can be seen from Figure 2, the design of the solar roof of the tile photovoltaic power generation system is different from that of the conventional distributed grid-connected roof. The tile photovoltaic power generation system perfectly combines the roof with the solar energy. The design and aesthetics of photovoltaic power generation are integrated into a sloping roof with solar tiles instead of conventional tiles. Its disadvantage is that the cost of solar watts is higher than the cost of ordinary solar panels, can not bring better economic benefits.
Interwindow photovoltaic system
The system not only provides electricity, but also automatically adjusts ventilation, humidity and temperature according to seasonal changes and external environment. Compared with the ordinary toughened glass roof, the interwindow photovoltaic system brings more convenient functions, which can make full use of the building space resources.
Wall-mounted photovoltaic power generation system
The wall-mounted PV system installs PV panels directly on the exterior walls of the building. Construction and maintenance are made easier by this unique external PV system. Since the solar energy system is installed on the exterior wall of the building, the solar cells absorb the radiant light from the outside of the building and generate electricity at the same time. This part of the radiant light was originally absorbed by the surface of the building, so the radiant energy absorbed by the building can be effectively reduced, especially in the summer can effectively reduce the temperature level of the building.
Louvered photovoltaic power generation system
The photovoltaic building heat of the system is through the thermal conductivity of the building envelope and the radiation of the Windows, which plays an important role in improving the indoor thermal comfort performance in summer. Unlike other wall photovoltaics, angled louvers allow the building to maximize the use of light energy and space.
Skylight photovoltaic system
Skylight skylight of this system is generally located in the lobby of buildings, usually the lobby skylight of domestic landmark buildings, such as museums, science and technology museums and other venues. If the translucent double glass photovoltaic panels are retrofitted or added, the skylight space can be used more effectively while taking care of the lighting needs, and the technology venues can present a modern atmosphere.
Future research and development priorities
Most of the energy consumed in the building is used to regulate the temperature. Currently, there are some examples of passive solar houses for heating, but these buildings are relatively expensive and difficult to promote. Active solar houses are more expensive and less valuable to promote. Therefore, the future research on solar house must be a way of combining renewable energy with conventional energy. In the implementation of the scheme, different schemes can be adopted according to the function of the building room, which can effectively reduce the initial investment of photovoltaic power station for building energy supply and improve the operability of the whole scheme. The control and adjustment technology of air temperature in buildings should be applied intelligently as far as possible to comply with nature to meet the needs of human health and comfortable life. The aim of air temperature control and regulation technology should be to minimize the so-called artificial environment. Under the premise of using active energy supply to ensure the comfort of living in the building, the active function technology and passive energy supply technology should be combined as far as possible, so as to achieve the optimal cost performance of solar energy buildings.
Conclusion
BIPV is a combination of the original building and the solar power generation device. On the basis of realizing the functions of traditional buildings, BiPV can perform the function of solar photovoltaic power generation and can be used to provide electric energy for indoor buildings. Photovoltaic building integration is not a simple stacking of photovoltaic power generation system and buildings, but an organic combination of the two, which can reach 1+1> The effect of 2.
