Energy and Buildings (2022). https://doi.org/10.1016/j.enbuild.2022.112135

The data collection process for thermal energy storage (TES) system is largely still and restricted to data collection only. This leaves a gap to study the transient state physical process of charge and discharge as it proceeds. In addition, these devices are restricted and cannot perform on spot model fitting, prediction and other data curation techniques. This paper demonstrates the application of intelligent data layer with neural networks for evaluating and predicting end to end performance of heat pump integrated stratified thermal energy storage (TES) system.

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Energy and Buildings (2022) https://doi.org/10.1016/j.enbuild.2021.111536

The article describes an experimental development of a new prototype of the horizontal plate shower exchanger for wastewater heat recovery. The prototype is designed so that while achieving the highest possible value of efficiency, it also respects the requirements of the spatial arrangement of the heat exchanger casing and, thus, allows an appropriate flow of wastewater on both sides of the heat transfer surface. At the same time, emphasis is placed on the smallest possible height of the heat exchanger casing with regard to the minimisation of the built-up space and the expected wastewater flow during the shower cycle. Experimental testing was performed according to the conditions meeting the certification criteria of the Passive House Institute, while for a given heat exchanger, the investigated flows and water temperatures, as well as the heat transfer efficiency of the new prototype was determined, reaching peak values ​​of up to 62%. An energy analysis and derivation of the equation was also performed, according to which it is possible to determine the achieved heat savings in the preparation of domestic hot water from the heat transfer efficiency of the exchanger, including all heat losses of the system. With new prototype, heat savings more than 21% are achieved.

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Build. Simul. (2021). https://doi.org/10.1007/s12273-020-0753-8

Due to the different approaches in determining the ventilation airflow rate per person for workspaces, where high-temperature air conditioning systems are used for air conditioning, problems with the condensation of water vapour on the cold surfaces of the system can occur. The article analyses the risk of condensation in various European cities using the available climatic data. Systems with cooling ceilings and cooling beams with a ventilation device operating in parallel are taken into account. Different ventilation airflow rates per person were analysed. On the example of a room equipped with high-temperature cooling, an energy simulation calculation is performed, which includes a ventilation and air-conditioning system with the possibility of capacity control. It is clear from the results that the condensation of water vapour can be prevented by technical measures at the cost of reducing the cooling capacity, which can affect the achievement of the thermal comfort of those present. In the end, suitable solutions are discussed, which should already be adopted at the time the device is designed so that the risk of condensation is not a major obstacle in the operation of these energy-efficient systems. An irreplaceable role in the operation of high-temperature cooling systems is played by a measurement and control system with a suitable algorithm to prevent condensation.

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Renewable Energy,Volume 154, Pages 1165-1179, ISSN 0960-1481

An efficient storage retains thermal stratification and improves the discharging performance. Turbulent mixing between hot and cold water is the prime source of stratification destruction. In this paper quantification of turbulent missing was achieved on the basis of temperature profile, MIX number, and Richardson number. The evaluated parameters include flow rate, ΔT, and diffuser design, henceforth a direct interdependence between each was thus established. Various CFD models were developed and experimentally validated on the test rig in order to find the optimal working conditions in discharge mode. The results proved numerically that the tank working conditions can be optimized by proper selection of inlet device. For instance, slotted type inlet device sustained maximum stratification even in as adverse a condition as of turbulent inflow & low ΔT. Perforated and simple inlet devices were capable of delivering best discharge efficiency only at low flow rate of 200 l/h and were showing insignificant dependency on ΔT. However, as flow rate is increased, ΔT dependency increased. Seeing the compounded benefits of slotted inlet devices and decreased ΔT, it was concluded that slotted inlet device delivered comparatively better thermal performance at both adverse conditions i.e. high flow & low ΔT and high flow & high ΔT, however, failed to outshine the rest of the inlet devices at low flow rate & low ΔT, and low flow rate & high ΔT. These research findings can serve as guidelines to optimize the storage tank design – more specifically, inlet device based design integrated with heating system, as thermal stratification and COP of heating system – heat pumps, for example, are inherently correlated. Heat pumps are high flow rate and low ΔT devices, while, solar systems are low flow rate and high ΔT devices, Thus, opting for accurate choice of inlet device for a particular operating condition is critical.

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Build. Simul. (2020). https://doi.org/10.1007/s12273-020-0629-y

The global energy consumption of data centers (DCs) has experienced exponential growth over the last decade, that is expected to continue in the near future. Reasonable utilization of DC waste heat, which is dissipated during the computational process, can potentially be an effective solution to mitigate the environmental impact. However, the practical implementation of waste heat utilization in the DC environment is a very challenging task. The possible benefits of waste heat utilization are uncertain and difficult to quantify with the methods that are common in practice. This paper introduces a feasibility study in which dynamic simulation tools were used to predict the energy performance of a university campus resulting from the integration of a proposed DC system with an existing aquifer thermal energy storage (ATES). The presented study utilizes building energy simulation (BES) to evaluate uncertainty of the waste heat potential associated to various thermal management strategies of the proposed DC. Further in the feasibility study, the carbon footprint of the integrated approach is assessed for both the current and future situation based on measured data from the existing university campus and its district ATES system.

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Zelenský, P. ., Barták, M., Zmrhal, V. ., & Mázik, J. . (2022). Simulation-Aided Development of a Compact Local Ventilation Unit with the Use of CFD Analysis. CLIMA 2022 Conference. https://doi.org/10.34641/clima.2022.194

The current emphasis on the renovation of existing buildings to meet EU energy efficiency targets brings, in addition to energy savings and related CO2 reduction, also some negative issues. One of them can be the lack of fresh air supply caused by increased air tightness of the building envelope after its insulation and renovation or change of windows. The easy solutions are decentralized units for local ventilation, which can be installed during fast renovations in selected rooms without major building modifications. Controlled ventilation then ensures the delivery of a sufficient amount of fresh air to meet current standards and, at the same time, creates a healthy and comfortable environment for occupants. The paper demonstrates the practical use of CFD simulations for the development of a new type of compact small ventilation unit for local ventilation of rooms with heat and humidity recovery. An increase in the device efficiency and a reduction in acoustic power, while maintaining its very compact dimensions, were achieved with the help of the numerical study. The paper shows the possibility of using CFD analysis during the development of new HVAC appliances. It describes the preparation of the numerical model of the device, presents the simulation approach, including the calculation settings, and discusses device optimization based on variant numerical analyses in ANSYS Fluent. The initial prototype design of the unit was optimized following the findings from the numerical analysis, and it was verified by CFD study that the proposed adjustments were appropriate and that the expected results were achieved. In a separate CFD study, the use of different types of diffusers at the air outlet from the supply duct to the room was addressed. It was recommended to use adjustable nozzles, which allow one to direct the air flow into the room according to the user’s preference. Consequently, it was verified that the ventilation unit meets the hygienic noise limits, both for day operation and for night operation with reduced power.

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Zavřel, V. ., Zelenský, P. ., Macia, J. ., Mylonas, A. ., & Pascual, J. . (2022). Simulation aided development of a façade-integrated air handling unit with a thermoelectric heat exchanger. CLIMA 2022 Conference. https://doi.org/10.34641/clima.2022.20

The paper presents a simulation aided development of a new type of a façade-integrated air handling unit for local ventilation of rooms. The unit is developed as a part of the Plug-and-Use (PnU) concept within the H2020 project PLURAL. Unlike conventional local ventilation units designed solely for ventilation, the developed air handling unit has a two-stage heat recovery that combines a passive and an active heat exchanger. The active heat exchanger consists of an array of thermoelectric elements and provides the flexible and energy efficient capability of temperature control of supplied ventilation air. The paper demonstrates the practical use of building energy simulations for the development of the unit. A combined simulation approach was used, while the IDA ICE software addressed the indoor CO2 concentration and related ventilation volume flow rates used for the TRNSYS software, which predicted energy performance and indoor thermal conditions. In the TRNSYS, a numerical representing the initial prototype of the air handling unit was prepared. This sub-model was integrated into the TRNSYS building model of the real installation demo site, namely, the Terrassa building, Barcelona, Spain. A variant numerical analysis was performed with two different compositions of the building envelope (pre- and post-renovation) and several ventilation control strategies and air handling unit operation settings. The performed simulations were capable to predict the performance of the innovative device in the real-case arrangement, under various scenarios, on the scale of the entire building. The simulation analysis demonstrated that the façade integrated air handling unit can clearly improve the IAQ conditions and reduce the overheating in the case when no other cooling system is available. The simulations provided an important navigation for the design team to further develop the innovative device.

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Zavřel, V., Šimek, J., Bäumelt, T., Martínek, V., Mishukov, A., & Barták, M. (2022). Experiment-based testing routine to characterize building energy flexibility for potential aggregators. CLIMA 2022 Conference. https://doi.org/10.34641/clima.2022.356

The ultimate goal is to introduce a standardized routine to characterize flexibility of a given building for the purpose of potential flexibility aggregators. The routine should provide the characteristic demand response of the building under various smart-grid control signals (e.g. time-of-use (stage) pricing, real-time pricing etc.). The scope of this paper is limited to the experimental part, that demonstrates measured demand response provoked by testing sequences. The testing sequences were applied via cloud-based service to the building management system (BMS) of a mid-size office building in Prague. The evaluation is not limited only to power metering but also includes indoor environment quality (in terms of room air temperatures and CO2 concentrations), HVAC system and local meteorological data monitoring. The air handling unit (AHU) and cooling system response were investigated using ‘step’ and ‘modular’ testing sequences. The real-life experiments revealed authentic demand response allowing to characterize building flexibility in full details. The key findings are, that the operation of the HVAC system components can be blocked for relatively long period of time (2 to 5 hours in studied case) without any critical consequences to the indoor environment quality. Approximately 30 % of the total power load per the testing event can be considered as flexible. The quality of the power profile was found highly irregular. Due to the power profile fluctuation the ramping/modulation at the single building level was found ineffective. In contrary to the modular control, the multi-stage control led to more detectable power reduction. The stage type of control provoked more observable, reliable, and easier-to-predict demand response.

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In: Proceedings of Building Simulation 2019: 16th Conference of IBPSA. International Building Performance Simulation Association, 2020. p. 1824-1831. BS 2019. vol. 16. ISSN 2522-2708. ISBN 978-1-7750520-1-2.

This paper introduces an innovative concept of an autonomous curtain walling façade module. The façade module integrates functions of heating, cooling, ventilation, lighting, shading as well as renewable energy storage and generation to the façade structure. The main contribution of the presented research is the development and validation of a new numerical model representing the in-façade air-conditioner using thermoelectric cells. The model captures its hygro-thermal and electrical behaviour and provides a satisfactory agreement with measurements of an experimental setup.

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In: Central Europe towards Sustainable Building (CESB19). Bristol: IOP Publishing Ltd, 2019. IOP Conference Series:Earth and Environmental Science. vol. 290. ISSN 1755-1307.

The contribution of buildings towards energy consumption has dramatically increased over the past decade. According to the EC’s Joint Research Centre, HVAC systems in Europe were estimated to account for approximately 11% of electricity consumed in Europe [1] and with associated CO2 emissions highly contribute to global climate change. This paper deals with the electricity consumption of air-conditioning systems in buildings in the Czech Republic. The paper presents results of actual measurements in 15 mostly office buildings over a 5 year period. The extensive analysis of measured data is presented in graphs and tables. A considerable difference in the electricity consumptions for cooling between the various administrative buildings is identified. The advanced commissioning of air-conditioning systems and its general application in the Czech buildings is presented in the paper as well. Energy consumption measurements, proper operation and application of advanced commissioning are identified as important methods tool to reduce energy consumption of airconditioning systems in existing buildings.

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In: Central Europe towards Sustainable Building (CESB19). Bristol: IOP Publishing Ltd, 2019. IOP Conference Series:Earth and Environmental Science. vol. 290. ISSN 1755-1307.

Waste water heat recovery is currently one of the possible ways how to reduce energy performance of buildings. The mathematical model using specific heat pump parameters is presented in this article. The aim was to verify efficiency of the waste water recovery system with heat pump for domestic hot water heating in family houses. The model enabled to evaluate heat recovery effectiveness during a day cycle. The first set of simulations of a typical day cycle has shown that the heat pump with recuperation of waste water is not effective solution for family houses. However, it might be interesting for the objects with larger consumptions. Another simulations for these objects were performed and more promising results were reached.

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In: Central Europe towards Sustainable Building (CESB19). Bristol: IOP Publishing Ltd, 2019. IOP Conference Series:Earth and Environmental Science. vol. 290. ISSN 1755-1307.

Realistic energy balance of photovoltaic system has a direct impact on realistic economic evaluation of operation costs for given building. To estimate the realistic electricity power profile with a short-time step, a generator based on appliances power, occupancy and external daylight presence has been developed and used for simulations. Generator allows to create different power profiles for the whole year (all days identical, workdays-weekends, 365 different days) with given time-step resolution (from 1 minute to 1 day). Paper presents and analyses the results from parametric simulations of PV production and building electricity loads balance with different times-steps. Monthly calculation approach used as a standard methodology for building performance evaluation significantly overestimates the solar fraction of PV systems. Only calculations with time steps shorter than 1 hour lead to results close to reality. A methodology for monthly balance correction to realistic results based on yearly PV production to building consumption ratio will be presented.

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