# Passive and Active Solar Systems in Eco-Architecture and Eco-Urban Planning
## 3 Research: Passive and Active Solar Systems in Eco-Architecture and Eco-Cities  
### Passive and Active Systems in Solar Architecture  
At Central European latitudes, the sun rises exactly in the east and sets exactly in the west only on March 21 and September 21; in summer, it lasts for as much as 16 h but in winter only 8 h [4]. In order to \"keep\" the sun inside the house for as long as possible, and at the same time store solar thermal radiation within rooms to give off heat after sunset, glazing of southern facades is needed using windows with high insulation and low heat transfer coefficients, along with accumulation walls made of appropriate materials that store heat such as stone, concrete or brick [5; 6; 7; 20]. One of the most important issues affecting the microclimate of the interior of a house is its orientation. This allows for the use of sunlight during the day, zoning rooms in terms of thermal requirements and creating buffer zones e.g., a garage and utility rooms to the north, or a \"winter garden\" to the south [9]. Indoor solar light can also be actively \"caught\" through light chimneys--tubularskyllights deflecting the sun's rays, solar lamps, and heliostats transmitting the reflected sunlight in any direction (Figure 1).  
Currently, intelligent glass that can regulate transparency and screens reflecting the sun's rays are also used. Intelligent windowpanes often consist of thermal and optical properties that can automatically change their parameters depending on environmental conditions such as temperature or lighting and that can be controlled. Additionally, tinted, heat-absorbing glass is used, as well as selective panes covered with multi-layer coatings applied to both outer and inner surfaces.  
The principles for passive solar architecture include (Figure 2):  
orientation;  
passive heating;  
creating buffer zones in buildings (a heat buffer using the greenhouse effect and a cold buffer using non-residential premises located on the north side) [9];  
use of an energy-saving form of building.  
The location of buildings using solar architecture should provide good insolation conditions (in this case, insolation means the average solar radiation per unit area) as well as the maximum number of sunshine hours per year. This situation is favorable for bioclimatic reasons, limits the use of artificial light and allows for the use of solar radiation energy in active and passive solar systems. The intensity of sunlight is significantly influenced by  
Figure 1: Principles for active solar architecture (authors, based on [PERSON] and [PERSON], 2000).  
Figure 2: Principles for passive solar architecture (authors, based on [PERSON] and [PERSON], 2000).  
the orientation of the windows: most light penetrates through the windows in the facade of the building facing south-west, and through roof windows with an orientation from south-east to south-west at a slope of 30-45\({}^{\circ}\), [10]. The inflow of solar radiation may be limited by shading from neighboring buildings or by trees; in this case, planting in the form of deciduous trees in summer protects against excessive sunlight but in winter enables maximum insolation.  
When discussing solar architecture, the role of shading in energy-efficient and sustainable buildings cannot be overlooked. This function is fulfilled by active systems: intelligent glass panes allowing for automatic regulation of the light supply, shutters, awnings, curtains and blinds mounted outside the windows, between glass panes or inside the building, and passive shading systems such as absorption panes, selective panes, elements of garden architecture or natural shading in the form of trees, shrubs or climbers.