Sašo Medved

An Experimental Study on a Microclimatic Layer of a Bionic Façade Inspired by Vertical Greenery

A microclimatic layer of the green façade is proven to have specific temperature and flow conditions on the building envelope. Lower temperatures and wind velocities, and higher relative humidity in the microclimatic layer are the characteristics of vertical greenery systems, which cause lower energy consumption for the cooling and heating of buildings. Despite innovative architectural solutions, there are some drawbacks to applying vertical greenery on building envelopes. In this study, a bionic façade that mimics the positive effects and eliminates the disadvantages of green façades is presented. The bionic façade consists of bionic leaves, which are made of photovoltaic cells and evaporative matrices. A real scale experiment was carried out in the summer to evaluate the potential of the cooling efficiency of the microclimatic layer and a new photovoltaic cooling technique. The results show a good agreement of the thermal performance between the bionic and the green façade and up to 20.8 K lower surface temperatures of photovoltaic cells, which increase the daily electricity yield by 6.6%.

Heat transfer through a double pane window with an insulation screen open at the top

The paper presents research of heat transfer through a double pane window with a screen and a siphon which form a semi-open cavity. Several operation modes of such devices as part of a transparent building envelope are shown, as well as the basis for mathematical and numerical CFD modeling with emphasis on conjugate heat transfer involving diffusion, convection and radiation. Gebharts method was used for radiation heat transfer. The PHOENICS code was used for CFD, with an additionally produced program code for the calculation of Gebhart factors and database formulation. Numerical results were validated with a series of experiments in which temperatures, heat fluxes and flow visualization were observed. The visualization technique was used for low fluid velocity measurements. After validation of the numerical code, a parametric study for such elements of the building envelope was evaluated with a range of boundary conditions based on the expected meteorological conditions. A modified form of dimensionless radiation number was used for empirical Nu number correlation.

Experimental research on physiological response of elderly with cardiovascular disease during heat wave period

The fact that the environment and human beings interact with each other has been known for centuries. In the present study, elderly’s heart rate (HR) and blood pressure response to indoor thermal comfort and indoor air quality (IAQ) were investigated. Indoor thermal comfort was characterized by Humidex, IAQ by CO2 concentrations. The results show that HR increase which is a prognostic factor for cardiovascular mortality is related to an increase of heat burden and low air quality. Meanwhile blood pressure would decrease as physiological response to these conditions. Our study demonstrates that common impact of heat burden and poor air quality on blood pressure and HR is greater than impact of exposure to each of them. Planners and decision makers that work in the field of designing indoor environment for elderly people or other risk groups should be aware of interactive influence of the thermal environment and the air quality on health and that unsuitability conditions could be ascertained by the occupants’ physiological response.

A simplified method for calculating heat losses to the ground according to the EN ISO 13370 standard

Heat losses from buildings through contact with the ground, especially in the case of large buildings, have a strong influence on energy demand. Various methods for calculating these heat losses are available, including one method that is defined by the EN ISO 13370 standard. Due to the complexity of this method, we have developed a method that is presented in this paper. Using our method we have calculated weight factors for buildings with and without basements with a variety of thermal transmittances for the contact between the building and the ground. Also, the number of influential parameters used in EN ISO 13370 is reduced. Our simplified method is particularly appropriate for use in the process of designing the thermal insulation for buildings and determining the specific heat losses from buildings.

Long-therm operation experiences with large-scale solar systems in Slovenia

In the early eighties more than 20 large-scale solar systems were installed in Slovenia. The majority of them are used for hot water and swimming pool heating. A lot of systems are in operation for more than 15 years. The overview of the large-scale solar systems in Slovenia is presented. For several systems the configuration, energy gains, difficulties in the operation and maintenance in years of operation are discussed.

The local ventilation system coupled with the indirect green façade: A Priliminary study

Green facades are becoming an important architectural element in an urban environment. Regarding the technology of the installation of green facades, one can distinguish between direct and indirect green facades, living walls and double skin facades with foliage. In addition to aesthetics of green facades, an impact on the outdoor and the indoor comfort has been proven. That is due to changed temperature and air fl ow conditions at the building envelope boundary. It has been proven that green facades impact lower surface temperatures of a building envelope and enhance thermal insulation properties of a building envelope, thus reducing the energy demand of a building. Based on the results from green facade thermal response research and growing interest in local ventilation systems, one can conclude that there is potential for a free cooling of a building. Therefore, this paper presents the design and the preliminary experimental research of a local ventilation system coupled with an indirect green facade. Based on the experimental work, it has been ascertained that the indirect green facade can impact a 5 K lower inlet air temperature for the local ventilation system compared with the one at the traditional facade.

Health impact assessment of liquid biofuel production.

Bioethanol and biodiesel as potential substitutes for fossil fuels in the transportation sector have been analyzed for environmental suitability. However, there could be impacts on human health during the production, therefore adverse health effects have to be analyzed. The aim of this study is to analyze to what health risk factors humans are exposed to in the production of biofuels and what the size of the health effects is. A health impact assessment expressed as disability adjusted life years (DALYs) was conducted in SimaPro 7.1 software. The results show a statistically significant lower carcinogenic impact of biofuels (p < 0.05) than fossil fuels. Meanwhile, the impact of organic respirable compounds is smaller for fossil fuels (p < 0.05) than for biofuels. Analysis of inorganic compounds like PM10, 2.5, SO2 or NOx shows some advantages of sugar beet bioethanol and soybean biodiesel production (p < 0.05), although production of sugarcane bioethanol shows larger impacts of respirable inorganic compounds than for fossil fuels (p < 0.001). Although liquid biofuels are made of renewable energy sources, this does not necessary mean that they do not represent any health hazards.

Optimizing the Form of School Buildings by Using the Requirements for Daylight Illumination

Daylight is an important factor in the functional and aesthetic aspects of school-building design. Because of the broad scope of the topic, in this study we have limited our investigation to the influence of the shape of the classroom on the daylight levels and the visual comfort, as these factors have an important influence on the design of school buildings. We have also looked at ways of obtaining appropriate daylighting levels in multi-storeyed, corridor-based school buildings, the form that is most often used around the world. We have investigated the natural illumination levels in classrooms using computer models of classrooms (CMCs), which serve as a basis for determining whether the classroom meets the basic requirements for visual comfort. The efficiency analysis of the CMCs has allowed us to propose an optimal form for an actual classroom and school building which may influence the design of multi-storeyed, corridor-based school buildings in the future.

EFFICIENCY OF WATER THERMAL STORAGE

ABSTRACT The quality of thermal storage is, regardless of its way of operation, defined by energetic and exergetic efficiency which take into account the losses of mixing and provide a measure for the quality of the construction. The test results of thermal storage systems for hot water preparation and their efficiencies are shown by diagrams. From the analysis it can be seen that the quality of the solar system defines also the quality of heat storage and not only the quality of the collector.