**1. Introduction**

The need for energy is constantly increasing as human civilization develops. The modern energy system is moving toward replacing fossil fuels with renewable energy sources to ensure a sustainable energy supply [1, 2]. Solar energy is a renewable and environmentally friendly source of energy. Therefore, its application is widely used to achieve sustainable energy solutions. The contribution of solar energy to achieving sustainable development is determined by the affordability of meeting energy needs, creating jobs, and protecting the environment. At the same time, solar energy has not yet reached its maximum efficiency in its development. Therefore, research and innovation are important factors in improving the efficiency of renewable solar energy technologies.

Solar energy ranks first among the renewable energy sources introduced into the energy supply of modern buildings [3]. The studies [4, 5] analyze the issues of the effectiveness of the integration of solar systems in the structure. Many studies have been devoted to studying the features of predicting a solar renewable resource when using solar energy in the energy supply of buildings, among them [6–9].

The studies note the variability of solar energy in space, time, and the complexity of modeling, and various methods are proposed for analysis taking into account the parameters of time and latitude.

The authors of [10] raise the issue of the importance of identifying changes in the composition of solar irradiation for solving problems of integrating photovoltaic technologies.

The amount of energy produced by photovoltaic panels directly depends on the amount of sunlight they receive. Therefore, when modeling the real distribution of solar irradiation on surfaces, it is necessary to take into account the dynamics of changes in light conditions. At the same time, one of the important factors influencing the change in light conditions is the variable influence of direct sunlight, diffuse sunlight, and complex direct and diffuse light.

In the modern practice of real simulation of the irradiation of the surfaces of solar systems, the direction of light is mainly used, simulating the conditions of illumination by direct sunlight, which provides the most effective conditions for obtaining energy from the Sun. In this case, the irradiated part of the surface is considered to be where the rays of direct sunlight fall. The diffuse light of the sky, which also takes part in the irradiation of the surface, is not taken into account. Although there are cases where the diffuse light component is larger compared to direct sunlight. For example, in overwhelming cloudiness, when scattered light predominates, as well as in the zone of own or falling shadow on the surface, where direct sunlight does not fall. Thus, when solving problems of integration of heliosystems, three types of exposure to sunlight should be considered according to the state of the sky:


Each of these types of exposure has its own nature of change and modeling approaches. Direct sunlight is associated with modeling the movement of the Sun. The diffuse light of the sky is characterized by its quantitative indicators and uneven distribution of brightness. Complex light is determined by the total influence of two types of light (the Sun and the sky) in different proportional ratios.

Modeling of the irradiation process when integrating solar systems into a building can be carried out on a geometric basis, including modeling of variable parameters of the irradiation source (direct sunlight, scattered sky light, andcomplex sky light), geometric parameters of the surfaces of the building itself and elements of solar systems. The use of geometric modeling methods for the integration of solar systems on the surface of a building allows solving various problems that arise in the design process. Such tasks include optimal modeling in terms of irradiation of building surface shape parameters, irradiation duration, effective irradiation zones, shading zones, and reflection of light rays from the surface, taking into account the orientation

## *Geometric Modeling of Parameters of Variable Natural Light during the Integration… DOI: http://dx.doi.org/10.5772/intechopen.112134*

of the building surfaces relative to the cardinal points. The use of geometric modeling tools allows to imagine the process of interaction between the parameters of variable irradiation and the geometric parameters of the shape of the building surface. It is important to determine the means of geometric modeling of light distribution for each type of illumination: direct solar exposure, diffuse (diffuse) sky exposure, and complex direct sunlight and sky exposure.

In this section, the task is to explore and bring together the methods of geometric modeling of direct and diffuse sunlight variables by representing them in a ray form, that is,. light vectors. This will make it possible to geometrically model the complex combined action of direct and diffuse sunlight.
