Issue 2/2019

The article deals with events and people who have influenced how the indoor environment has been perceived. The emphasis is on indoor air quality and thermal comfort. In the 19th century, people were concerned about spreading illnesses in poorly ventilated buildings. Therefore, the recommended amount of outdoor ventilation air was derived from requirements of physicians. Later, the requirements of engineers prevailed and in the 20th century the recommended amount of outdoor ventilation air was set with regard to ensuring the indoor environment quality. After the oil crisis (in the second half of the 20th century) a so-called sick building syndrome phenomenon emerged, while at the end of the 20th century, the issue of sustainability come into focus. By the beginning of the 21st century, the health of occupants and the often associated work productivity are once a gain in the forefront of the interest (and importance) in the i ndoor environment field.

The paper deals with the issue of turbo compressors. It focuses on the principle, modelling and prevention of so-called “surge”. The first part describes the principle of gas compression in turbo compressors and analyses the most important characteristics – of pressure, power and efficiency. Furthermore, the attention is paid to the “surge” – a negative phenomenon that occurs during the operation of turbo compressors. The last part presents the control methods of the “surge” suppression and the principle of standard control of the turbo compressor with “antisurge” regulation.

The paper analyses the possible year-round operation of a large-area solar systems using water as a heat transfer fluid. In order to avoid the ice formation, it is necessary to heat the water in the system during the periods with possible water freezing. The paper shows what energy demand can be expected and what factors can influence the demand.

In Slovakia has been realized about 170 geothermal drills with geothermal water (GHW) with borehole temperature from t0 = 15.7 °C to 126.0 °C. Most of these areas have temperature of the GHW suitable for heating and preparing hot water for flat areas, public facilities, agriculture and for industrial areas and for recreational purposes too. At this paper, we would like to show an exemplary solution for a problem of reconstructed heat source for a residential complex, which is heated with geothermal energy. The cooled GHW is subsequently used for heating of a polyclinic and at the end is cooled GHW used for the thermal pools. These pools are filled with diluted GHW – mixed GHW with cold water.

The article analyses the prospects for technically feasible ways of developing flexibility in conditions of common Czech households, both housing units and family houses. It focuses mainly on the importance of the accumulation of energy from renewable energy sources (RES) and the management of household consumption. It also mentions the psychological impact of remote control of energy consumption on the user. It addresses especially the technological, and not legislative, issues of the flexibility integration into the normal life of consumers.

The article compares, from the technical point of view, the controllers for water heating by photovoltaic systems, available on the Czech market. Regulators were borrowed from manufacturers for testing at the University Centre for Energy Efficient Buildings (UCEEB) CTU in Prague. They were powered by an electronic solar simulator with predefined profiles of the volt-ampere characteristics. The aim of the measurement was to determine the controller’s ability to monitor the maximum power point, measure the internal efficiency of the inverter, the overall capacity to transfer energy to the load, evaluate the output signal and the overall design of the controllers.

The article deals with one of the areas of building lighting technology – insolation. It describes the types of buildings for which the insolation is verified, the conditions to be taken into account in the calculations and the values of insolation requirements according to current legislation. The means of determining the position of the sun in the sky and the uncertainty of the calculations are described as well. Several model situations have been evaluated with a continuous and a limited length of the shading object. On the basis of the results, graphical tools are used to quickly verify the dependence of insolation times on the selected shading parameters.