Holcapek O.,Czech Technical University |
Holcapek O.,University Center for Energy Efficient Buildings
EAN 2015 - 53rd Conference on Experimental Stress Analysis | Year: 2015
This paper focuses on possible application of newly developed textile reinforced cement matrix for strengthening load-bearing structure elements from concrete. One year old concrete beams 100 × 100 × 400 mm made from ordinary concrete C 25/30 have been used for verification of possible application of this matrix and glass fabric for strengthening. Fine grain concrete with compressive strength over 100 MPa with maximum grain size 1.2 mm and water-binder ration 0.29 was used. The aim of performed experimental program is to evaluate the influence of various number of alkaliresistant (AR) glass fabrics (1, 3, and 5 layers) applied on bending side. The cohesion of concrete surface layer with the newly applied slim surface of textile reinforced concrete has been approved.
Richter J.,Czech Technical University |
Stanek K.,University Center for Energy Efficient Buildings
Energy Procedia | Year: 2015
This paper reviews common problems and approaches in the design of modern crawl spaces. It also presents a full-scale experimental set-up and a set of laboratory experiments designed to further investigate their hygrothermal and microbiological behaviour. This work is a part of a long-term research project to determine the basic rules for designing naturally ventilated crawl spaces in the Central European climate that would be moisture-safe, mould-free and with minimum maintenance requirements. © 2015 The Authors.
Pavlu T.,Czech Technical University |
Pavlu T.,University Center for Energy Efficient Buildings |
Sefflova M.,Czech Technical University |
Sefflova M.,University Center for Energy Efficient Buildings
EAN 2016 - 54th International Conference on Experimental Stress Analysis | Year: 2016
This paper deals with possibility of use the fine fraction of recycled concrete aggregate as partial replacement of sand in concrete mixture. The main topic of this article is the study of evaluation of the durability of the fine-aggregate concrete with partial replacement of sand by fine recycled concrete. The freeze-thaw resistance was tested. The weight loss was measured after 25, 50, 75 and 100 cycles of freeze-thaw. The dependence of weight loss after freeze-thaw cycles on water absorption capacity of fine aggregate concrete were expressed. The fine recycled concrete which was used as partial replacement of sand originated from highway demolition. The replacement rate was 10 %, 20 % and 30 %. Durability properties were investigates by using cubic and prismatic specimens.
Racova Z.,Czech Technical University |
Richter J.,Czech Technical University |
Stanek K.,University Center for Energy Efficient Buildings |
Ryparova P.,Czech Technical University
CESB 2016 - Central Europe Towards Sustainable Building 2016: Innovations for Sustainable Future | Year: 2016
A crawl space has several advantages in comparison with other types of foundations. However, in the specific conditions of Central Europe it can become very problematic in terms of moisture and mould growth. This paper presents results of preliminary laboratory experiments carried out to identify the best biocidal protection for wood and wood-based materials used as lower sheathing of the base floor in modern crawl spaces, with a special attention paid to chemical substances containing silver. The key outcomes are the sorption curves and susceptibility of untreated and treated materials to mould growth. It was shown that all the tested materials performed practically identical sorption behaviour. By contrast, the materials show very different susceptibility to mould growth in otherwise identical conditions.
Cachova M.,Czech Technical University |
Vejmelkova E.,Czech Technical University |
Vejmelkova E.,University Center for Energy Efficient Buildings |
Polozhiy K.,University Center for Energy Efficient Buildings
Materials Science Forum | Year: 2015
Exterior renders are protecting the load bearing parts of building constructions against the negative action of surrounding environment such is freezing-thawing action, crystallization of salts in pore system of material, biocorrosion etc. Thus sufficient mechanical properties, namely bending strength and adhesion to load bearing material’s surface, as well as durability properties are required. The paper deals with durability parameters of lime plasters modified by pozzolana and small amount of Portland cement. Such modification provided reduction of rate of liquid water transport what is promising with respect to freezing-thawing resistance of render. The water vapour diffusion coefficient was influenced just moderately. © (2015) Trans Tech Publications, Switzerland.
Vana Z.,Czech Technical University |
Privara S.,Czech Technical University |
Zacekova E.,University Center for Energy Efficient Buildings |
Cigler J.,Czech Technical University
2013 European Control Conference, ECC 2013 | Year: 2013
Buildings account for significant amount of final energy consumption and therefore there is an intensive research aimed at its optimization. Predictive control has become a very popular approach in many industries buildings included. The main bottleneck of this method is a need for a good model. There are many different identification frameworks, plenty of methods and approaches, some of them more or less suitable for the building modeling. A common situation is that there are number of models at hand (often of different complexities), and there is a need for selection of the 'best' model for predictive control. A logical choice is to start testing the statistical significance of an additional complexity (in a sense of the structure and number of disturbance inputs) of the model. This paper proposes a systematic way of building-up the model, starting from a simple structure. Then, more complex models are considered in an iterative manner. In each iteration, the statistical significance of the additional information due to the more complex model is checked. The procedure stops when selecting more complex models brings no quality improvements. In this paper, a semi-physical modeling using CTSM1 and model selection based on statistical tests are presented. Finally, the properties of the proposed algorithm are investigated. © 2013 EUCA.
Siroky J.,University of West Bohemia |
Cigler J.,University Center for Energy Efficient Buildings |
Ferkl L.,University Center for Energy Efficient Buildings
2013 European Control Conference, ECC 2013 | Year: 2013
This paper describes the application of Hybrid Model Predictive Control (HMPC) to a building heating system. The hybrid model contains continuous variables corresponding to physical quantities as well as discrete variables serving as indices of a Linear Time Invariant (LTI) model in action. Two LTI models are considered, each describing different configurations of the building heating system. The application of HMPC allows efficient handling of disturbances by reconfiguration of the heating system. The proposed HMPC strategy improves comfort and reduces energy demands. An exact solution of HMPC is computationally demanding; therefore, three suboptimal solutions are suggested. These take into account specifics of the building heating system and significantly reduce the computational complexity. All presented strategies are compared by means of a numerical simulations using real weather data and a model of a real building. © 2013 EUCA.
Sacha J.,Czech Technical University |
Sacha J.,University Center for Energy Efficient Buildings |
Jelinkova V.,University Center for Energy Efficient Buildings |
Snehota M.,Czech Technical University |
And 4 more authors.
Physics Procedia | Year: 2015
A ponded infiltration experiment was conducted under simultaneous imaging to investigate variations in quasi-saturated hydraulic conductivity a process frequently observed in infiltration experiments in soils with wide grain -size distribution. An artificially prepared heterogeneous sample composed of coarse quartz sand (representing pathways of preferential flow) and fine porous ceramic (representing soil matrix) was investigated. The sample was 34.5 mm high and 29.0 mm in diameter. Sequences of neutron radiography images (RI) of pixel size 0.045 × 0.045 mm were taken at one angle during particular transient phases of the flow process. During quasi-steady state flow stages of the experiment radiography images were acquired in range of angles 0-180° in 0.9° step and. 3D neutron tomograms (TI) were then developed. Using the data a quantitative evaluation of the spatial and temporal distribution of water content within the sample was conducted. For every RI and TI the amount of water in particular pixels and voxels, respectively, was calculated by subtracting the image of dry sample. The accuracy of the water content estimates derived from the images was checked by comparing them to the corresponding gravimetrically determined water content data. Heavy water with equilibrium air saturation was introduced into the sample during two recurrent infiltrations. Thirty five hours later, during second infiltration, the inflow was switched to degassed heavy water in order to remove residual air present in the sample. During the first twelve hours of first infiltration run flow rate through the sample decreased from 3.7 cm/hour to 1.0 cm/hour at the end of the "steady state flow" stage. The flow rate in second run decreased from 3.6 cm/hour to 1.6 cm/hour. Comparison of the tomogram of the sample at the beginning and one taken at the end of the steady state flow stage in each run shows an increase of water content in the porous ceramic, while the water content in the coarse sand decreased. On the contrary, during the subsequent infiltration with degassed water the flow rate increased to its maximum value of 10.5 cm/hour. The tomograms confirmed removal of the residual air during this stage. Increased water content in the coarse quartz sand was evident on a tomogram made at the end of the degassed water infiltration. The results show that the residual air saturation and its spatial distribution strongly affected the water flow in the quasi-saturated heterogeneous media representing natural soil. © 2015 The Authors.
Wolf P.,University Center for Energy Efficient Buildings
Czech Polar Reports | Year: 2015
It is well known that the utilization of renewable energy sources is inevitable for a sustainable future. Besides the fact that other energy sources such as coal, gas or nuclear power have limited reserves the proper use of increasingly higher shares of renewable energy sources may lower negative impacts of traditional energy sources on the ecosystems. This is especially important in naturally protected areas located in remote Earth locations. Such areas are still almost untouched by mankind, e.g. Antarctica. The research activities in the area of renewable energy sources have increased rapidly within the last few decades. It is of a global interest to carry out the research in an ecologically sensitive way, i.e. balance the outputs and the effects of infrastructure on environment. In this paper, a project of installation of a photovoltaic system on the Czech Antarctic Station (Johann Gregor Mendel) on the James Ross Island is described and the first experience from the system run is reported. The contribution of this system to the overall energy production on this station shortly after commissioning of the system is presented as well. In discussion, a possible future development of the system is suggested.
Vcelak J.,University Center for Energy Efficient Buildings |
Kral J.,Czech Technical University
Journal of Physics: Conference Series | Year: 2013
Undersurface localization systems are accuracy demanding application. Localization methods used for common position estimation in open space or in building cannot be used since they are usually based on RF signal transmission or satellite navigation. Magnetic localization methods are usually the only usable solution. Horizontal directional drilling is one of accuracy demanding application where the operator needs to know exact position of the underground unit with respect to a given point on the surface. Long range surface magnetic localization system will be presented in this paper. This paper will summarize achievable accuracy of magnetic localization and maximal range with respect to given localization error. First results measured with presented system will be presented as well as results from FEM modeling. The influence of target distance, magnetic sensors noise, orientation sensor accuracy and surrounding material will be evaluated and considered in this work. © 2013 Published under licence by IOP Publishing Ltd.