Issue 1/2025

A study for specific planned district in Dolní Počernice in Prague shows a benefit of hydrogen system utilization with combined power and heat use to increase coverage of the energy demand of buildings while maximizing the use of their roofs area. Based on the optimiza tion analysis, the sizes of the electrolyzer, hydrogen storage and fuel cell were designed resulting in high coverage of the electricity use 86 % while high local utilization of the photovoltaic system production reached (96 %). Because of conventional standard of the buildings, the coverage of the heat demand by waste heat from electrolysis and fuel cell is at low level of 19 %. By shifting the buildings to the energy passive standard and increasing the photovoltaic system by covering the parking lots, it could be possible to increase the coverage of electricity use to 98 % and hea t to 42 %, in the case of seasonal hea t accumulation even up to 80 %.

The article focuses on the noise emission during air flow through blade grilles, which are used in the distribution elements of air handling systems. Based on a series of experiments and simulations of aerodynamic noise using computational fluid mechanics (CFD), an optimal blade shape was proposed. At the same time, optimum airflow velocities at air supply outlets were recommended to reduce aerodynamic noise emission.

The article outlines the problem of heating of mountain recreational buildings. They were divided according to their construction and use into three categories. For each of these categories, the heating methods used were described with emphasis on the hea t sources used.

The aim of this paper is a simple prediction of flow patterns during condensation of a fluid in a small-diameter vertical pipe with downward flow direction. The prediction is based on the calculation of the fraction of the gaseous phase of the condensing fluid (water) on the basis of experimentally measured data sets. Selected correlations of some authors are presented in the paper, which can be advantageously used to calculate the gas phase fraction independently of the experimentally measured data sets. The calculated values of the gas phase fraction are compared with tabulated values according to some authors, to which the corresponding fluid flow patterns during condensation in small-diameter tubes are assigned. It has been confirmed that the indication of the flow patterns according to the gas phase fraction is only informative, yet it is sufficient to get a general idea of the flow patterns in small-diameter pipes during condensation. For accurate identification, other parameters such as the quality of the gaseous component of the condensing fluid must be taken into account. The quick determination of the gas phase fraction and the resulting flow patterns can be advantageously used to construct simple flow pattern maps and use them to determine hea t transfer during phase changes.

The article deals with the principle, use and comparison of API providers for meteorological data acquisition. API finds a wide range of applications in intelligent building management systems, be it energy management, predictive maintenance, or advanced control of renewable energy, irrigation systems or lighting. The paper starts by describing the basic principles of the API and gives an overview of typical meteorological data that can be provided through the API. Its main part deals with a comparison of API providers according to different parameters such as usage costs, call limits and available meteorological variables for non-paid and paid tariff options. In the conclusion, providers of dedicated solar API for photovoltaic power plants are compared.

Fires in buildings are accompanied by associated phenomena, including smoke. If the smoke is not extracted outside the building, it accumulates under the ceiling structure and the space is gradually filled with smoke. Existing calculation techniques for assessing the smoke layer drop in the Czech Republic have no clear justification and, in many cases, lead to misleading results. For this reason, a new CSN calculation technique was developed and compared with NFPA, ISO and ASET calculation techniques and CFAST fire model. Comparisons were made for geometrically large objects and for objects of “normal geometric dimensions”. Statistical differences were evaluated using the RMSE method, with the ISO calculation technique as the reference equation. The largest differences were obtained when comparing the NFPA-ISO calculation techniques, when the maximum difference was 0.166. The differences were smaller for the other calculation techniques. The differences between the CSN-ISO calculation techniques were minimal, with a maximum of 0.007. The newly developed CSN calculation technique can be considered as promising for building design in the Czech Republic.