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Concerning the building environment HVAC facilities, even if a great effort has been made in developing components and systems with high nominal efficiencies, less attention has been paid to the problem of system maintenance. The main objective of the thermoeconomic diagnosis is to detect possible anomalies and their location inside a component of the energy system. The second objective, and indeed the one to be achieved in this paper, is indicated as inverse problem. It is associated with the quantification of the effects of anomalies in terms of thermoeconomic quantities. Its rigorous application in building thermal installations has some difficulties relating to the strong interrelation between the different components and the fact that energy supply facilities are continuously changing with time. The way to deal with dynamic circumstances is thoroughly explored in this article. Likewise, this paper’s main goal is to demonstrate an application of two thermoeconomic diagnosis methodologies in the building sector, one based on the malfunction and dysfunction analysis and the other one based on the characteristic curves of the components. The results obtained allow us to point out the advantages and limitations of both methodologies as well as to combine them and then develop a more reliable diagnosis. [ABSTRACT FROM AUTHOR]

HVAC systems in buildings are composed of many subcomponents which consume energy in huge amounts. In recent years, energy consumption becomes very important aspect due to the lack of energy resources and environmental reasons. In terms of energy consumption, the components of HVAC systems account for large portion of total energy used in buildings. Therefore optimization of energy consumption in HVAC applications is an essential requirement in terms of thermodynamic and economic point of views. Besides, the efforts for decreasing energy consumption turn into economic recovery. It also provides benefits for human health and cleaner environment. In this paper, as originality, thermodynamic and economic analyses of an existing social and cultural building which has a heating and cooling area of 8852 m 2 are presented by comparing of a conventional HVAC and a VRF system. A novel contribution is given to the open literature by comparing two systems with actual data measured from the existing system. The other originality is to apply and test a VRF system to a complex-structured building. This study is a rare one which contains insulation, heating and cooling accounts of a building together. In this paper, VRF system is modelled to the existing building for the comparison of the conventional HVAC system. Both systems have been compared in terms of heating and cooling capacity, initial, operation and maintenance costs. It is found that the VRF system is more economic and efficient such that the VRF system is found to have 44% cost profit when compared with the conventional HVAC system. [ABSTRACT FROM AUTHOR]

To date, religious facilities have received little attention in the published literature regarding energy use and efficiency. With unique operating and building characteristics, these buildings have distinct opportunities for analysis in regards to building energy use and occupant comfort. With overall lower average energy intensity, religious facilities rarely receive energy assessments or are operated by experienced personnel. Therefore, identifying common issues is critical for training church owners in energy efficiency. This paper presents an in-depth analysis of heating, ventilation and air conditioning (HVAC) systems and occupant comfort in two religious facilities. The analysis reveals that the largest opportunities for reduction in energy use come from proper maintenance and operation of HVAC equipment and schedules. Temperature setbacks are shown to be an important operational setting to reduce energy usage. An accompanying analysis on thermal comfort reveals that temperature setbacks must be coupled with sufficient preconditioning of the space to ensure occupant comfort during intermittent building occupancy. An analysis of CO 2 levels in the building during occupancy reveals the need for sufficient outside air to meet ventilation standards. [ABSTRACT FROM AUTHOR]

Model predictive control (MPC) has been studied in the building science realm for about three decades. However, the following two aspects of the building control have not been studied thoroughly in MPC research. One is the impact of the mixed-mode cooling system on the active heating ventilation and air conditioning (HVAC) energy consumption, and the other is the differences of individual thermal comfort preference and its impact on energy. This paper proposes an occupant-oriented mixed-mode EnergyPlus predictive control system to optimize HVAC energy consumption while meeting the individual thermal comfort preference. A web-based dashboard is implemented in the test-bed building for three months to collect individual thermal comfort preference data. The data analysis results suggest that occupants have various tolerances and preferences about thermal comfort. The simulation results show that, during one week of a typical swing season, the mixed-mode system further reduces the active HVAC energy consumption, and the diversified occupant thermal comfort preference has significant impact on HVAC energy consumption. [ABSTRACT FROM AUTHOR]

Combined air heating and ventilation systems are often used in low energy buildings. However, operating these systems in the heating mode increases vertical air temperature gradient in rooms and can have negative effect on indoor air quality. The effectiveness of ventilation and personal exposure of the occupants to airborne pollutants generated at the floor level in rooms with the combined air heating and mixing ventilation was analyzed in this paper. The dispersion of pollutants was evaluated under three air distribution methods (in-ceiling four-way and one-way air supply, and high level wall grille air supply) and under three air change rates (1, 2, and 3 ach). Each of these cases were tested at the supply air temperature of +20 °C and +25 °C by performing CFD simulations and experiments in the full-scale test chamber. The results of the experiments showed higher inhaled concentration of the contaminants under the heating mode. The inhaled-to-ambient pollutant concentration ratio varied in the range of 1.05–1.41 under the ventilation mode and it rose up to 1.14–1.78 under combined air heating and ventilation mode. CFD predictions confirmed that pollutants generated at the floor level are entrained into convective boundary layer of the occupant in cases when vertical air temperature gradient was present. The personal exposure to pollutants released at the floor level can increase significantly when a HVAC system runs in the combined air heating and ventilation mode; this effect will not necessarily dissolve with the increase of the air change rate. [ABSTRACT FROM AUTHOR]

In buildings, HVAC systems consume a high amount of energy to provide thermal comfort for occupants. A methodology is presented in this paper to control thermostat operation of the buildings considering the effects of indoor and outdoor boundary conditions and phase change material (PCM) characteristics. EnergyPlus v8.1 building energy simulation software was used to analyze the energy performance of the PCM incorporated building models and to implement Fanger model to control HVAC thermostat operation according to BS EN 15251:2007 thermal comfort categories. Three types of building HVAC schedule, PCM with different melting points and layer thicknesses were studied for Madrid climate zone. Moreover, the impact of occupants clothing on the energy consumption was investigated. Furthermore, payback analysis was conducted to find out the economic benefits of PCM integration into the building envelopes. Application of PCM improved the cooling and heating energy performances except for the office model in winter (heating period). Additionally, higher energy savings and lower payback periods were observed when PCM with higher melting point was applied to the buildings. Eventually, energy savings in PCM incorporated models were found to improve further when occupants changed their clothing behavior in winter. [ABSTRACT FROM AUTHOR]

In order to reduce energy consumption in buildings, a solution using phase change materials (PCMs) as thermal energy storage (TES) is presented. During summer nights, cold is stored and delivered during the day to reduce cooling load, whereas in winter, heat from solar air collector is stored for heating during morning and evening hours. Proposed is a stand-alone unit suitable for offices, which consists of plates filled with paraffin RT22HC. The objective of the paper is to examine the functioning of the suggested TES system on an annual basis and to explore the feasibility of using it for both, cooling and heating. First numerical model is set up, which assumes 2D geometry and evaluates thermal response, calculations are carried out in Fluent. Then validation of simulations with experimental results is established. Finally the feasibility of storage unit on an annual basis is demonstrated. [ABSTRACT FROM AUTHOR]

Artificial intelligence techniques have been successfully applied to control dynamic systems looking for an optimal control. Among those techniques, reinforcement learning has been shown as particularly effective at reducing the dimensionality of some real problems and solving control problems by learning from experience. The use of thermal energy storage active systems in the building sector is identified as suitable option to reduce their energy demand for heating and cooling. However, these systems might be expensive and require appropriate control strategies in order to improve the performance of the building. In this paper a ventilated facade with PCM is controlled using a reinforcement learning algorithm. The ventilated facade uses mechanical ventilation during nighttime to solidify the PCM and releases this cold stored to the inner environment during the peak demand period. It is crucial to decide correctly the schedule of charge and discharge process of the PCM according to the weather and indoor conditions. An experimentally validated numerical model is used to test the performance of the control algorithm under different weather conditions. Important improvements on the energy savings due to the use of control strategies were found and supported by the data under the different tested climatic conditions. [ABSTRACT FROM AUTHOR]

The damper used for the control of airflow in heating, ventilation and air conditioning systems can constructively be adapted to measure the air velocity with its moment characteristic. It is a device that indirectly determines the air velocity by measuring the position of the blades and the air stream moment acting on it. The subject of this paper is energy consumption of the air torque position damper depending on its structure. The aim is to compare the energy consumption of four possible types of dampers with non-cascading blades: with one blade, with two cross-guided blades, with two parallels-guided blades and with two blades, one of which is a measuring blade and the other remains fixed in horizontal position. The case when there is a straight section of a duct both in front of and behind the damper was considered. Adequacy of the existing mathematical model and energy consumption for all four types of dampers was determined experimentally. It was found that the damper with two blades of which one is a measuring blade and other remains fixed in horizontal position had minimal energy consumption. [ABSTRACT FROM AUTHOR]

The paper presents the results of the analysis of the impact of various ventilation systems on the energy consumption performed for one Polish museum building that was built in 1929–1930. Simulations were carried out with the use of two computer codes: CONTAM and ESP-r. Multi-zone models including the exhibition rooms and the staircase were prepared. The simulations were made of synthetic weather data for one of the Polish towns for two months of the heating season. Twenty-four hour variability of internal heat gains was taken into account. The results show clearly that the natural ventilation system (which is currently used in the building) enables the air exchange with fresh air on the first floor only. The air infiltration on the upper levels is close to zero. Rebuilding the ventilation system generates changes in the energy demand of the building. It is presented how the heat demand increases with the increase of the ventilation air flow and what is the impact of the air infiltration on the heat demand for different variants of ventilation. [ABSTRACT FROM AUTHOR]

Abstract: Integrating passive systems such as cross and stack ventilation, a solar chimney, a wind tower or an earth-air tunnel into a building envelope has the potential to significantly reduce the ventilation and air-conditioning demand on buildings. However the application of combination of these features in low rise contemporary buildings is limited. Among the major reasons, is the lack of simple building modelling techniques preventing effective integrated passive systems. Existing coupled multi-zone airflow and thermal modelling software such as COMIS-TRNSYS, CONTAM-TRNSYS or TRNFLOW do not include the passive airflow components which require simultaneous prediction of temperature and airflow rate in the components such as solar chimneys and wind-induced earth-air tunnels. This paper develops an integrated model incorporating these passive airflow components into a coupled multi-zone ventilation and building thermal model. The model is validated against COMIS-TRNSYS software for a lightweight building with large openings. The prediction of each passive airflow component is validated with available published analytical and experimental findings. The solar chimney model is able to predict reverse flow and accurately predicts the air temperature in the chimney. The earth air tunnel (EAT) considers the transient heating up effect of the soil during operation and predicts the outlet air temperature. [Copyright &y& Elsevier]