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Abstract In this paper, a new method entitled "BBEE (Building Blocks Energy Estimation)" for estimating energy performance at the district level is proposed. It consists of two branches, namely the BBEE algorithm and an energy database of a typical zone. This method is used to keep architects and urban planners informed of the energy performance of their design by clustering zones and looking up corresponding energy intensities from the database. Because the related energy databases are preexisting, energy performance modeling and simulation are not required from the user. On the other hand, the database is set up and continuously replenished by parameterization simulations with a basic model of typical zones. This task was separated from the estimation process and operated by experts, which shortened the process and reduced modeling errors. As a case study, an urban district with eight buildings was estimated under three climate conditions separately following the proposed BBEE method. Results were compared with the full-model simulation using a simulation tool called DeST. The difference in annual heating demand between estimation and simulation was reported as less than 6% in all three cases. The potential applications and limitations of the proposed BBEE method are discussed at the end of this paper. Although further improvements are still required, the new estimation method could be helpful for energy performance estimation at the district level at the early stage of design. [ABSTRACT FROM AUTHOR]

Highlights • A new experimental procedure to test PCM-enhanced components is presented. • A modified Dynamic Heat Flow Meter Apparatus is used to perform the tests. • The thermal conductivity of PCMs is measured in different phases (solid-liquid). • Indications to solve the issues related to building PCM-specimens are provided. Abstract The implementation, in Building Performance Simulations (BPS) tools, of robust models capable of simulating the thermophysical behaviour of a Phase Change Material (PCM) represents a fundamental step for an appropriate thermal evaluation of buildings that adopt PCM-enhanced envelope components. Reliable and robust measuring procedures are essential, at a material and component level, to provide experimental data for the empirical validation of software tools. The traditional laboratory tests that are generally used for the validation of models present some limitations, because PCMs are usually subjected to conditions that may be very different from the real boundary conditions of the building components in which PCMs are applied. Furthermore, in many experimental full-scale mockups, the relatively small quantity of installed PCM and the combination of several thermal phenomena do not allow software tools to be tested in a reliable way. In this paper, an experimental procedure, based on a modified Heat Flow Meter Apparatus, has been developed to test the behaviour of PCM-enhanced components; the procedure, which is based on the measurement of the sinusoidal response, has been set up to provide data for the comparison and testing of numerical models and of BPS tools. Moreover, general indications and guidelines are provided to solve some issues related to building specimens that contain bulk PCM in order to obtain a more accurate measurement of their performance. The experimental results presented in this paper were obtained from two different bulk PCMs (organic and inorganic). It was found that it is important to evaluate different PCM typologies and different thermophysical boundary conditions, including partial and full phase transitions, to test simulation codes that implement PCM modelling functions. In fact, some phenomena, such as hysteresis and subcooling effects are more evident when partial phase transition takes place. The results related to the characterization of the thermal conductivity of a paraffin-based PCM have shown a significant increase (up to 42%) of the equivalent thermal conductivity from a solid to a liquid state, with an upward heat flux, thus highlighting that further investigations and improvements are needed to measure the equivalent thermal conductivity in the different PCM phases. [ABSTRACT FROM AUTHOR]

Solar-based radiant heating systems represent a sustainable, and relatively low-cost, technology to raise the temperature of the interior thermal mass of our buildings. Through the use of direct absorption solar thermal collectors, the same working fluid which absorbs the solar energy can be used to transfer the energy for storage in the thermal mass of the structure using a network of pipes embedded in concrete floors. This study investigates a promising working fluid which can be used in such systems – one which is based on multi-walled carbon-nanotubes suspended in normal base fluids. A major stumbling block affecting the wide spread use of carbon-nanotube nanofluids is their low dispersion stability at elevated temperatures, which significantly reduces the absorption capabilities of the nanofluids and could lead to clogging of the pumps used to circulate the fluids. In this paper, we report on a scalable UV-ozone (UVO) treatment technique to produce highly stable dispersions for the elevated temperatures experienced by working fluids in radiant heating systems. To probe suitability of UVO treated multi-walled carbon-nanotube (MWCNTs) for solar-assisted radiant heating systems, this paper investigates the effects of exposure time and temperature on stability, optical absorbance properties, the extent of functionalisation, and the photothermal conversion performance of UVO-treated MWCNT nanofluids. No agglomeration or degradation of the MWCNTs was observed at elevated temperatures (up to 150   °C), highlighting the stability of proposed nanofluids. [ABSTRACT FROM AUTHOR]

In this paper, the problem of dispatching the operation of a distribution feeder comprising a set of heterogeneous resources is investigated. The main objective is to track a power trajectory, called the dispatch plan , which is computed the day before the beginning of operation. In this paper, we propose a method to optimally compute the dispatch plan so as to optimize the operation of the feeder while making sure to allocate enough local reserves to absorb deviations of the realizations. Indeed, during real-time operation, due to the stochasticity of part of the resources in the feeder portfolio, tracking errors need to be absorbed in order to track the committed dispatch plan. This is achieved by modulating the power consumption of a utility-scale battery energy storage system and of the heating, ventilation and air conditioning system of a commercial controllable building. To this end, a hierarchical controller is designed to coordinate these two controllable entities while requiring a minimal communication infrastructure. Due to the inherent different response times of these systems, the power injection of the electrical battery is controlled at a sub-minute time-scale so as to absorb high-frequency tracking errors and, therefore, deliver the dispatch service. At a slower time-scale, the controllable building is controlled to maintain the state of charge for the electrical battery at a scheduled level by means of a model predictive controller. The model predictive controller is designed in order to account for both comfort and operational constraints of the controllable building, as well as power limits for the electrical storage. The effectiveness of the proposed control framework is demonstrated by means of both an extensive simulation analysis, as well as a set of 12 full day experimental results on the 20 kV distribution feeder in the campus of the Swiss institute of technology in Lausanne, that is comprised of: 1) A set of uncontrollable resources represented by five office buildings (350 kWp) and a roof-top photovoltaic installation (90 kWp), 2) a set of controllable resources, namely, a grid-connected electrical storage (720 kVA–500 kWh), and a fully-occupied multi-zone office building (45 kWp). [ABSTRACT FROM AUTHOR]

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]

The construction industry in the European Union is turning increasingly in the direction of sustainable building. A particular important component of sustainable construction strategy is represented by the reduction of operational energy in buildings. One popular solution for the reduction of heat losses through the exterior envelope is the thermal insulation with polystyrene panels, frequently used in composite systems (ETICS – External Thermal Insulation Composite Systems). These solutions are efficient for operational energy savings, contributing in the same time to the reduction of environmental pollution and degradation due to the current energy production systems. Still, they present some reliability problems, being vulnerable to wind actions. The paper proposes an alternative solution for fixing the polystyrene panels by replacing the adhesive mortar with anchors and regular mortar to compensate the flatness. The paper presents experimental results for adhesive bonding strength of adhesive and regular mortar to various substrates. The results were embedded into numerical models for determining the response to wind actions both for the classical and proposed solution. The paper presents a comparative analysis of the mechanical and economic performance for the two fixing solutions. Finally are discussed the advantages and disadvantages of the mechanical fixing solution proposed and are identified the main areas of application. [ABSTRACT FROM AUTHOR]

The paper deals with location and exposure of the building in terms of building airtightness. Airtightness of the building envelope is one of the basic prerequisites of energy-efficient buildings. Energy efficient buildings situated in areas with lots of wind and in exposed locations could constitute up to 10% of total heat consumption. The exchange of air through the building envelope is conditional on pressure difference between interior and exterior. The pressure difference is usually caused by a combination of wind effect, stack effect, combustion and ventilation. The location and its parameters (exposure, altitude, wind, temperature and other) can be considered as passive determinative factors of air permeability of the building envelope. The surrounding environment of the building does not have a direct impact on the final airtightness of the building envelope. However, the exposure of the building, the altitude, the strength and wind speed have a significant impact on the pressure effects acting on the building. Pressure effects affect the amount of air flowing through leaks, cracks and gaps in the building envelope. The higher the pressure effects on the building is, the higher the air flow through the building envelope is. The aim of the paper is to verify, or reject, the potential impact of basic parameters of location on the final airtightness of the building envelope. The possible statistical dependence is tested by using test of independence. The calculated levels of significance (Sig.), also called as p-value, are compared with a reference level of significance α (5%). Fundamental data for testing consists of 150 energy passive houses built in the years 2004 -2014 in the Czech Republic. [ABSTRACT FROM AUTHOR]

In buildings, occupant behaviour is recognised as a major contributing factor to energy demand and in particular to heating consumption. To achieve thermal comfort within the heating season, people report to use heat in very different ways; for example behaviours include switching on the heating system, putting on warm clothes, drawing curtains, changing rooms, making a hot drink and using a hot water bottle. While research has focused on subjective accounts using interviews, diaries and questionnaires, little is known about the frequency and probability of these behaviours. Using a mixed-method approach, this paper reports on the results of a field study in dwellings using wearable and environmental sensors. The analysis investigates the probability of these behavioural responses as a function of seven independent variables; (1) external and (2) internal monitored temperature, (3) probability of heating being on or off, (4) time of the week, (5) time of the day, (6) the three categories of the predictive thermal comfort model, and (7) the three categories of the adaptive thermal comfort model. Results show that participants were more likely to increase their clothing and activity level as internal temperature decreased, although there was no significant change in activity level throughout the course of a day. Methodologically, this paper demonstrates the effectiveness of different statistical tools in analysing occupants’ behaviours. Substantively, this paper emphasises the need for future research to gather objective data on what people do. [ABSTRACT FROM AUTHOR]

The article deals with the problem of energy saving by optimizing heat loss and measures for energy recovery in the existing preschools. The paper presents a theoretical basis, simulation and computations - calculations of heating energy needs for established models, by using appropriate software packages. The program and development of models for improving energy qualities of the envelope, with the tendency of switching to renewable energy sources, are defined. The methods used in this paper include the method of modelling based on the digital simulation of the representative facility, as well as local visits and interviews with relevant researchers, policy makers and preschool educators. The survey is conducted through a case study on the territory of the City of Nis. [ABSTRACT FROM AUTHOR]

Green roofs have been proposed for energy saving purposes in many countries with different climatic conditions. However, their cooling and heating potential strongly depends on the climate and building characteristics. In particular, the increase of the thermal capacity of green roofs compared to traditional roofs, if not controlled with insulation, may lead to higher cooling and heating loads. This paper discusses the energy saving potential of green roofs adopting a variable insulation strategy. A system consisting of a plenum located between a green roof and the room underneath and a sensor-operated fan that couples (or decouples) the green roof mass with the indoor environment was developed. The fan is activated and stopped using temperature based rules; the plenum is ventilated only when the fan works, creating a variable insulation system. Four cells with an insulated traditional roof, a non-insulated green roof, an insulated green roof, and a green roof with the variable insulation system have been tested in a hot and dry climate with mild winters over several years. This paper compares and discusses different plenum control algorithms. Results are particularly promising because the variable insulating system proved to adjust the thermal capacity of the roof effectively. In summer, the non-insulated green roof and the green roof with variable insulation system achieved the lowest indoor temperature; in winter, the insulated traditional roof and the variable insulation green roof system achieved the highest indoor temperatures. Measurements are hence compared with simulations. Finally, the energy saving potential of the new green roof system is evaluated. [ABSTRACT FROM AUTHOR]

This paper investigates factors associated with variation in daily total (electricity and gas) energy consumption in domestic buildings using linked pre-COVID-19 smart meter, weather, building thermal characteristics, and socio-technical survey data covering appliance ownership, demographics, behaviours, and attitudes for two nested sub-samples of 1418 and 682 British households selected from the Smart Energy Research Laboratory (SERL) Observatory panel. Linear mixed effects modelling resulted in adjusted R2 between 63% and 80% depending on sample size and combinations of contextual data used. Increased daily energy consumption was significantly associated (p -value < 0.05, VIF < 5) with: households living in buildings with more rooms and bedrooms, that are older, more detached, have air-conditioning, and experience colder (more heating degree days) or less sunny weather; households with more adult occupants, more children, older adult occupants, higher heating temperature setpoints, and that do not try to save energy. The results demonstrate the value of smart meter data linked with contextual data for improving understanding of energy demand in British housing. Accredited UK researchers are invited to apply to access the data, which has recently been updated to include over 13,000 households from across Great Britain. This paper provides guidance on appropriate methods to use when analysing the data. [ABSTRACT FROM AUTHOR]

Abstract: Directive 2010/31/EU adopted that by the end of 2020 all new buildings should be nearly Zero-Energy Buildings (nZEB) and Member States should achieve cost-optimal levels by ensuring minimum energy performance requirements for buildings. This paper discusses how low should be the energy required by a nZEB, in the context of housing energy consumption in a Mediterranean climate (Lisbon). For selected houses built after 1990, the calculated primary energy loads for regulated uses – heating, cooling and domestic hot water – are found to be below 90kWh/(m2 year). Applying the cost-optimal solutions of thermal insulation and glazing type and considering energy efficiency improved systems, this study concludes that housing energy loads are ‘low’ for the indicative range of 70kWh/(m2 year) for regulated uses or 100–110kWh/(m2 year) for total uses, taking primary energy indicators (PEI) from EN 15603. Assuming PEI from Passive House Planning Package or those to be assumed in Portugal for 2013, the threshold decreases to 60kWh/(m2 year) for regulated uses or 90–100kWh/(m2 year) for total uses. Only the first nZEB condition is explored by this paper. The second condition requires that the nZEB energy load is covered by a ‘significant’ part of renewable energy sources produced on-site or ‘nearby’. [Copyright &y& Elsevier]

Abstract: Nowadays, heating energy demand has become a significant estimator used during the design stage of any new building. In this paper we are proposing a model to predict the heating energy demand, based on the main factors that influence a building''s heat consumption. It was found out that these factors are: the building global heat loss coefficient (G), the south equivalent surface (SES) and the difference between the indoor set point temperature and the sol-air temperature. In the second part of this paper, multiple dynamic simulations were carried out in order to determine the values of the inputs and output data of the future prediction model. Using the obtained database, a multiple regression prediction model was further used to develop the prediction model. In the last part of this paper the model results was validated with the measured data from 17 blocks of flats. Moreover, in this article it is also shown the comparison with the results calculated using the building''s energy certification methodology. A detailed error analysis showed that the model presents a very good accuracy (correlation coefficient of 0.987). In conclusion, the proposed model presents the following characteristics: three inputs and one output, simplicity, large applicability, good match with the simulations and with the energy certification calculations, human behavior correction. [Copyright &y& Elsevier]

Abstract: The increase of peak and energy demand during the cooling season is becoming a crucial issue, as well as the intensification of the urban heat island effect. This trend is observed at several latitudes, including areas where overheating was unknown at building and urban levels. This phenomenon involves different issues: reduction of greenhouse gases, quality and comfort in outdoor and indoor environment, security of energy supply, public health. The building sector is directly involved in this change and adequate solutions can provide great benefit at energy and environmental levels. Roofs in particular are envelope components for which advanced solutions can provide significant energy savings in cooled buildings or improve indoor thermal conditions in not cooled buildings. Cool materials keep the roof cool under the sun by reflecting the incident solar radiation away from the building and radiating the heat away at night. Roofs covered with vegetation take benefits of the additional thermal insulation provided by the soil and of the evapo-transpiration to keep the roof cool under the sun. These two technologies are different in: structural requirements, initial and lifetime maintenance costs, impact on the overall energy performance of buildings. This paper presents a numerical comparative analysis between these solutions, taking into account the several parameters that affect the final energy performances. By means of dynamic simulations, the paper depicts how cool and green roofs can improve the energy performance of residential buildings in different localities at Mediterranean latitudes. [Copyright &y& Elsevier]

Abstract: The main goal of this paper is to evaluate the possibility of application or replacement of radiators with low-temperature radiant panels. This paper shows the comparison results of operations of 4 space heating systems: the low-temperature radiant panel system without any additional thermal insulation of external walls (PH-WOI), the low-temperature radiant panel system with additional thermal insulation of external walls (PH-WI), the radiator system without any additional thermal insulation of external walls (the classical heating system) (RH-WOI), and the radiator system with additional thermal insulation of external walls (RH-WI). The operation of each system is simulated by software EnergyPlus. The investigation shows that the PH-WI gives the best results. The RH-WOI has the largest energy consumption, and the largest pollutant emission. However, the PH-WI requires the highest investment. [Copyright &y& Elsevier]

Abstract This article introduces a parameter estimation and state prediction technique called constrained dual Extended Kalman Filter (EKF) that can be used in model prediction controls (MPC) and fault detection and diagnostics (FDD) in building systems. The proposed method is an improvement over the existing nonlinear filter-based methods such as the joint EKF or Unscented Kalman Filter, which is widely adopted in previous building controls research. Case studies using both simulation and real measurements are conducted to demonstrate the proposed algorithm when used for a building thermal zone. Data from parametric simulations are used to test the thermal model's ability to capture parameter variations. Measured data from five identical offices is collected to test the performance of parameter estimates and state predictions under real-life operation. Overall, the proposed algorithm is 25% faster than a conventional EKF with improved numerical stability. It can also help mitigate numerical instabilities seen in previous EKF research. The reduced thermal model used in this paper is also capable of detecting most of the parametric changes to the thermal zone and providing reliable temperature predictions. [ABSTRACT FROM AUTHOR]

Aiming to utilize the flexibility of smart buildings for flexible operation of active distribution network, a combined modeling and optimal scheduling method for the active distribution network with integrated smart buildings is proposed in this paper. Based on the heat storage characteristics of a building, the energy consumption prediction model of the building considering different heating zones with different orientations is developed using the Resistor-Capacitor thermal network model. Then, different optimal control methods of the heating, ventilation and air-conditioning system in the building are developed. The energy consumption management of the heating, ventilation and air-conditioning system is achieved by adjusting the room temperature within the suitable temperature comfort range. In order to further consider the impact of the integration of smart buildings on the economic and security operation of the active distribution network, the optimal scheduling method of the active distribution network with integrated smart buildings is developed considering the load factor of the aggregation of the smart buildings. Finally, the optimal scheduling results of the aggregation of the smart buildings under different heating, ventilation and air-conditioning control methods in the winter heating scenario are analyzed. In addition, based on the branch flow model, the optimal power flow model of active distribution network with on-load tap changer is constructed by piecewise linearization and second-order cone relaxation to achieve flexible and optimal operation of the active distribution network. Thus, the impacts of the optimal schedules of the aggregation of smart buildings on the economic and security operation of the active distribution network are further evaluated. Numerical studies demonstrate that the proposed optimal scheduling method can make full use of the demand response potential of the smart buildings and further contribute to the operating costs reduction of the smart buildings. Meanwhile, the optimization of the active distribution network with the load factor of the aggregation of buildings can reduce the power loss and increase the minimum voltage magnitude of the active distribution network utilizing the flexibility of the smart buildings. [ABSTRACT FROM AUTHOR]

Energy demand prediction of building heating is conducive to optimal control, fault detection and diagnosis and building intelligentization. In this study, energy demand prediction models are developed through machine learning methods, including extreme learning machine, multiple linear regression, support vector regression and backpropagation neural network. Seven different meteorological parameters, operating parameters, time and indoor temperature parameters are used as feature variables of the model. Correlation analysis method is utilized to optimize the feature sets. Moreover, this paper proposes a strategy for obtaining the thermal response time of building, which is used as the time ahead of prediction models. The prediction performances of extreme learning machine models with various hidden layer nodes are analyzed and contrasted. Actual data of building heating using a ground source heat pump system are collected and used to test the performances of the models. Results show that the thermal response time of the building is approximately 40 min. Four feature sets are obtained, and the performances of the models with feature set 4 are better. For different machine learning methods, the performances of extreme learning machine models are better than others. In addition, the optimal number of hidden layer nodes is 11 for the extreme learning machine model with feature set 4. [ABSTRACT FROM AUTHOR]

Polycarbonate panels could be considered as a suitable and cheap solution for walls, roofs, and sheds in non-residential buildings and, at the same time, granular silica aerogel is one of the most promising nano-materials for energy saving in buildings. In the paper, three types of advanced multiwall PC panels (thickness 16, 25, and 40 mm) with translucent granular aerogel were investigated by experimental (thermal and optical) and numerical characterization. By comparing thermal performance of air and aerogel-filled PC systems, it can be noticed that the impact of the aerogel is remarkable: the reduction in U-value is 46%-68%, depending on the aerogel layer thickness. U-value is 1.4 W/m 2 K for the 16 mm thickness sample and it is 0.6 W/m 2 K when the thickness increases up to 40 mm. The systems keep their performance in horizontal position, when they are used as roofs. Light transmittance is 0.61 and 0.42 for 16 mm and 40 mm respectively and the reduction with respect to air-filled panels is acceptable (15%) for 16 mm and significant (40%) for 40 mm thickness. The aerogel has also a remarkable impact on the reflectance spectrum , especially between 400 and 1400 nm. The solar factor is 0.58 for 25 mm thickness, quite similar to the low-e glazing one. Finally, energy simulations for a case study showed that aerogel-filled PC systems outperform conventional double glazing systems both for heating and cooling energy demands. However, when compared to low-e glazings, the benefits of the translucent material (also considering the highest thickness) in the interspace are lower for heating and negligible for cooling energy demands. The aerogel-filled polycarbonate systems could be a valid solution for non-residential buildings, enhancing the thermal performance and the light control of the building envelope, especially when they are used as roofs. [ABSTRACT FROM AUTHOR]

Actual national and international energy strategies generally encourage the use of renewable energy sources. Thermal energy storage (TES) offers various opportunities in the design of renewable energy systems. Thermochemical heat storage has gained popularity among researches because of higher energy density and lower heat loss compared to sensible and latent heat storage. On the other side solar energy has been recognized as one of the renewable energy sources with the most potential. This paper reviews thermochemical heat storage technologies and systems with emphasis on systems involving solar energy utilization in buildings. The studies are reviewed based on used storage materials, system configuration as well as models to predict and optimize system performance. [ABSTRACT FROM AUTHOR]

A variety of novel, recyclable and reusable, construction materials has already been studied within literature during the past years, aiming at improving the overall energy efficiency ranking of the building envelope. However, several studies show that a delicate control of indoor climating elements can lead to a significant performance improvement by exploiting the building’s savings potential via smart adaptive HVAC regulation to exogenous uncertain disturbances (e.g. weather, occupancy). Building Optimization and Control (BOC) systems can be categorized into two different groups: centralized (requiring high data transmission rates at a central node from every corner of the overall system) and decentralized 1 The terms “decentralized”, “distributed” and “agent-based” are considered to have similar meanings herein. 1 (assuming an intercommunication among neighboring constituent systems). Moreover, both approaches can be further divided into two subcategories, respectively: model-assisted (usually introducing modeling oversimplifications) and model-free (typically presenting poor stability and very slow convergence rates). This paper presents the application of a novel, decentralized, agent-based , model-free BOC methodology (abbreviated as L4GPCAO) to a modern non-residential building (E.ON. Energy Research Center’s main building), equipped with controllable HVAC systems and renewable energy sources by utilizing the existing Building Management System (BES). The building testbed is located inside the RWTH Aachen University campus in Aachen, Germany. A combined rule criterion composed of the non-renewable energy consumption (NREC) and the thermal comfort index – aligned to international comfort standards – was adopted in all cases presented herein. Besides the limited availability of the specified building testbed, real-life experiments demonstrated operational effectiveness of the proposed approach in BOC applications with complex, emerging dynamics arising from the building’s occupancy and thermal characteristics. L4GPCAO outperformed the control strategy that was designed by the planers and system provider, in a conventional manner, requiring no more than five test days. [ABSTRACT FROM AUTHOR]

The application of ground source heat pumps (GSHP) for heating and cooling of buildings is currently increasing in popularity in the UK and globally. Traditional GSHP systems use the naturally available geothermal gradient of earth for heating and cooling purposes using open loop or closed loop systems. In this paper, the use of mine water from a flooded coal mine for heating of buildings is presented using a GSHP system with an open loop configuration. The novelty of this approach is that a single shaft is used to extract the warm water and inject the cooler water back into the same shaft, thereby minimising the area needed, initial capital costs in constructing a doublet system and also potentially overcome the time consuming process to address related environmental agencies regulation regarding the discharging of the mine water. The relatively stable temperature low enthalpy of mine water contained in the abandoned and flooded coal mines are ideal to be used for both heating and cooling of buildings when used in conjunction with heat pumps. The GSHP is considered to be an effective means of reducing the carbon emission as it gives more output in the form of thermal energy in comparison to the electrical energy it consumes as input. This research work reports on the performance of the system over the winter season and its long term potential in converting the mine water from an environmental liability to a sustainable energy resource and offers a means to regenerate the former coal mining areas. [ABSTRACT FROM AUTHOR]

With the gradual increase of building energy consumption in recent years, the application of phase change energy storage materials in buildings has become the focus of researches. Phase change material (PCM) embedded in the envelope can increase the building inertia to keep the temperature stable. It can also store energy and release energy when needed. In this paper, the system of PCM radiant floor combined with PCM wall attached with sunspace was established. The thermal characteristics and the energy consumption of the building are studied through analyzing the data from the experimental investigation including the temperature and the heat flux. Two different buildings were built between the PCM room and the conventional room with the same dimension and building. The main test conditions are divided into passive and active control stages by comparing the air temperatures, envelope temperatures, phase transition temperatures, heat fluxes and power consumptions between the two rooms. It is concluded that the average room temperature of the experimental room is 7.15 °C higher than that of the conventional room in the passive energy storage stage. While the average energy-saving rate of PCM room was 54.27% compared with the conventional room in the active control stage. [ABSTRACT FROM AUTHOR]

In this paper, three kinds of heating modes were presented for an apartment in Beijing and mathematical model of the apartment was developed to study the heating energy consumption and thermal environment. Results showed that temperature changed obviously in daytime when heating stopped if two intermitting heating modes used. The larger temperature decrease and the lowest indoor air temperature meant that two intermitting heating modes were suitable for the condition no people in the house daytime. Besides, the solar radiation, building’s thermal energy storage property and heating time affected the rooms’ temperature and apartment’s heating load obviously. Intermittent heating needed to increase the capacity of heating equipment to keep the indoor design temperature of each room. Compared with continuous heating mode, intermitting heating mode such as mode B and mode C could decrease the energy consumption effectively, and the decreased energy consumption percentages were 4.24% and 14.73% respectively. Heating mode determined by people’s behavior pattern was an important factor to the building’s energy consumption and indoor thermal environment. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES) systems with phase change materials (PCMs) as a known energy storage technology have a high potential for increasing the energy efficiency of buildings. In fact, the use of PCMs with various approaches, either active or passive, in the building helps to maintain the temperature in the thermal comfort range for occupants through decreasing the temperature swings, and lower energy consumption by the load reduction/shifting. Due to the significance of this issue, many research works have been carried out on the application of PCMs in buildings. In this study, the experimental works in the fields of PCMs in buildings are taken into account. The papers are classified based on heating, cooling, and air-conditioning. Besides these, the applications of nano-PCMs in buildings are reviewed. According to what has been carried out up to now, the gaps are identified and analyzed for preparing useful suggestions for future works. The recommendations and suggestions are presented at the end of the chapters as well as the conclusion, and the literature is summarized in some tables. [ABSTRACT FROM AUTHOR]

The temporal fluctuation of solar energy resources often require the utilization of thermal energy storage to increase the level of solar energy. Solar energy systems that are used to meet the heating demands of buildings can be implemented in a variety of system configurations, ranging from energy production and storage at the building-level, to centrally located production and storage components coupled with a district-heating network. In this paper, quasi-steady state simulation models are used to evaluate the impact that different design configurations of decentralized and centralized solar thermal systems (with short- and long-term storage) have on the overall economic cost of the energy provision and the degree of solar energy utilization. A suburban neighbourhood in Switzerland consisting of 11 buildings is selected as a case study. Simulation results suggest that building-level long-term storage configurations out perform all other system configurations in terms of solar fraction and system efficiencies for the given case study. Furthermore, the results demonstrate that the location of the thermal storage and the separation of short- and long-term storage are crucial issues that affect the performance of building-level renewable energy sources, and thus merit further investigation. [ABSTRACT FROM AUTHOR]

This paper presents a new methodology for the estimation of power capacity profiles for smart buildings. The capacity profile can be used within a demand-side management system in order to guide the building temperature operation. It provides a trade-off between the quality of service perceived by the end user and the requirements from the grid in a demand-response context. We use a data-fitting approach and a multiclass classifier to compute the required profile to run a set of electric heating and cooling units via an admission control module. Simulation results validate the performance of the proposed methodology under various conditions, and we compare our approach with neural networks in a real-world-based scenario. [ABSTRACT FROM AUTHOR]

Identifying and harnessing renewable clean energy sources in crowded and polluted urban areas for heat production, in existing heating systems, represent an opportunity insufficiently exploited at present. Creating the optimum frame, in order to increase the participation share of renewable energies, represents nowadays a constant preoccupation and an important object in the field of energy. In this regard, the purposes of this paper are: identifying, analyzing and validating the specific performance indicators applicable in the comparative thermal energy analysis of the urban heating systems which quantifies the impact of integrating renewable energy sources, particularly thermal-solar energy, in the classical heating systems and the hybrid systems’ efficiency thus obtained, highlighting the importance of harnessing clean energies in crowded urban areas. The following concepts were approached simultaneously and synergistic: the energy efficiency of the thermal consumers and the harnessing efficiency of the renewable energy sources identified in urban areas in the buildings connected to the district heating system. Thoroughly, the performance indicators defined for the district heating systems were centralized and analyzed, achieving a synthesis of the specific indicators meant to analyze the hybrid heating systems which integrate technologies that harness renewable energy sources and a comparison of different suggested systems. [ABSTRACT FROM AUTHOR]

Real-time optimization (RTO) has been developed to improve the cost and/or energy efficiency of complex heating, ventilation and air-conditioning (HVAC) systems. In current literature, almost all of the developed real-time optimization methods belong to the type of time-driven optimization, in which the action of optimization is triggered by “time”. As optimization should be done when the system operating conditions experience a change that is large enough to cause current operational setting not optimal any more, optimization strategies should recognize ‘significant’ changes and perform optimization when necessary. Since the time-driven optimization is a periodic mechanism in nature while those ‘significant’ changes may not be periodic, the time-driven optimization cannot capture ‘significant’ changes and do the optimization promptly. Therefore, this paper proposes an event-driven optimization (EDO) for complex HVAC systems, the key idea of which is to use “event” rather than “time” to trigger the action of optimization. A systematic event-driven optimization method is illustrated, where its main tasks, including event definition and event identification, will be discussed. The proposed method will be compared with a conventional time-driven method using case studies, through which the main advantages of the proposed method will be identified. [ABSTRACT FROM AUTHOR]

There is a growing trend for the use of thermo-active building systems (TABS) for the heating and cooling of buildings, because these systems are known to be very economical and efficient. However, their control is complicated due to the large thermal inertia, and their parameterization is time-consuming. With conventional TABS-control strategies, the required thermal comfort in buildings can often not be maintained, particularly if the internal heat sources are suddenly changed. This paper shows measurement results and evaluations of the operation of a novel adaptive and predictive calculation method, based on a multiple linear regression (AMLR) for the control of TABS. The measurement results are compared with the standard TABS strategy. The results show that the electrical pump energy could be reduced by more than 86%. Including the weather adjustment, it could be demonstrated that thermal energy savings of over 41% could be reached. In addition, the thermal comfort could be improved due to the possibility to specify mean room set-point temperatures. With the AMLR, comfort category I of the comfort norms ISO 7730 and DIN EN 15251 are observed in about 95% of occasions. With the standard TABS strategy, only about 24% are within category I. [ABSTRACT FROM AUTHOR]

Building energy simulators such as TRNSYS, EnergyPlus, and Esp-r offer an excellent opportunity for detailed design of house thermal model and its Heating, Ventilating, and Air Conditioning (HVAC) system and provide very accurate simulation results useful for performance analysis and optimization process. In contrast, these energy simulators do not include sub-models of advanced devices/strategies for control of HVAC system operation and suffer from poor control mechanism. In addition to lack of an advance controller, they inherently offer no mechanism for estimating the future state of their process models based on forecast weather dataset. Hence, no predictive controller can be designed and implemented within these simulators. This paper discusses the development of a Matlab-TRNSYS co-simulator in order to control/manage a TRNSYS program, which was previously developed and calibrated based on the characteristics of a real case study house, with an advanced predictive controller. This co-simulator investigates the effectiveness of different predictive strategy planning models, including Load Shifting (LSH), Smart Dual Fuel Switching System (SDFSS), and LSHSDFSS, as the integration of fuel switching and load shifting strategy planning models on 24 h ahead energy cost saving of the case study house HVAC system. Simulation results of different consecutive sample days indicate that SDFSS could bring significant energy cost saving. However, LSH and LSHSDFSS effectiveness is sensitive to the outdoor temperature. [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]

Current indoor thermal environment is usually automatically controlled based on a temperature set-point given by room occupants or building managers. However, investigation shows that many temperature set-points are far from the comfortable temperature range recommended by design handbooks. Such unreasonable temperature set-points will result in not only uncomfortable indoor thermal environment, but also waste of cooling or heating energy. The authors have proposed a methodology of satisfaction based control to take place of the traditional set-point based control. This paper describes the experimental comparison results between satisfaction based indoor thermal environment control and set-point based control. Two test-beds were set up and a series of experiments was conducted to compare control performances, user acceptances, user work performances and system energy consumptions of the set-point based and satisfaction based control. The comparison results show that the satisfaction based control can achieve more stable thermal environment. Both of the two control methods can get relatively high scores regarding user acceptance and work performance. There are no statistically significant differences for user acceptance and work performance between two control methods. However, satisfaction based control consumed 15.3% and 11.9% less energy at two test-beds respectively than set-point based control due to more reasonable temperature settings given by the satisfaction based control. [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]

This paper investigates and compares the energetic and ergonomic performance of three different control logics (on–off, PID, fuzzy), used to regulate the emission of the heating system of an energy-efficient building. Tests were carried out on an experimental building, equipped with three electric radiators and a sensor network mapping internal, external and surface thermal conditions. The building–technical system ensemble was evaluated in real time for a monitoring period of five/six days of non-occupancy, winter/midseason weather and Mediterranean climate. All controllers were assessed with regard to thermal comfort and energy consumption in order to return an exhaustive scenario of possible strengths and weaknesses. The comparison showed that fuzzy logic, properly configured, outperformed both PID and on/off controllers reducing energy consumption of 30–70% and maintaining thermal dissatisfaction between comfort limits for all the monitoring period. [ABSTRACT FROM AUTHOR]

This paper quantifies green roofs energy savings which is a challenging topic, namely in Mediterranean climate with distinct heating and cooling seasons. The thermal behavior of a green roof case study in Lisbon, Portugal, was assessed through an experimental campaign during heating and cooling periods of the year of 2013. These experimental results were then used to calibrate a building energy simulation in EnergyPlus. After validation, the numerical model was used to compare the energy performance of intensive, semi-intensive and extensive green roofs. The three green roof types lead to similar heating energy needs but extensive green roof solution shows higher cooling energy needs than semi-intensive and intensive ones, of 2.8 and 5.9 times more, respectively. Furthermore, the performance of each type of green roof and different insulation properties was compared to traditional roof solutions. With no thermal insulation, extensive green roofs require 20% less energy use than black roofs and show a similar annual behavior than white roofs. Semi-intensive and intensive green roofs energy use is 60–70% and 45–60% lower than black and white roofs, respectively. Well insulated roofs do not take full advantage of evapotranspiration cooling effects, which is particularly noticeable when comparing with high reflective white roofs. [ABSTRACT FROM AUTHOR]

Although it is widely acknowledged that occupants play a critical role in building energy consumption, the characteristics of occupants are not well-represented in building simulation. Many statistic and data-mining technologies have been applied to develop a reliable occupant model. In contrast, rather than attempting to develop the occupant model, this study aims to investigate the correlation between the occupant behavior and energy consumption based on a series of experiments. First, this paper discusses the randomness of the occupants’ presence and behavior. The degree of randomness was verified using a Normalized Cumulative Periodogram (NCP) based on a random walk hypothesis. In addition, the correlation between occupant and energy consumption was investigated using the wavelet coherence. This study shows that, while the occupants’ presence has a randomness, it is not strongly correlated to the energy consumption. The occupants’ active action to control a heating/cooling system (turn on/off) is correlated to the energy consumption. In contrast to the occupant's presence, the occupants’ active action does not follow the random walk, and it has no particular frequency. This means that it is difficult to predict the control action of occupants with a specific time interval. [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]

The intensification of the Urban Heat Island effect (UHI) is a problem that involves several fields, and new adequate solutions are required to mitigate its amplitude. The construction sector is strictly related with this phenomenon; in particular, roofs are the envelope components subject to the highest solar irradiance, hence any mitigation strategy should start from them and involve their appropriate design process. For this purpose, cool materials, i.e. materials which are able to reflect a large amount of solar radiation and avoid overheating of building surfaces have been deeply analyzed in the last years both at building and urban scales, showing their benefits especially in hot climates. However, green roofs also represent a possible way to cope with UHI, even if their design is not straightforward and requires taking into account many variables, strictly related with the local climatic conditions. In this context, the present paper proposes a comparison between cool roofs and green roofs for several Italian cities that are representative of different climatic conditions. In search of the most effective solution, the answers may be different depending on the perspective that leads the comparison, i.e. the need to reduce the energy consumption in buildings or the desire to minimize the contribution of the UHI effect. [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]

This paper presents a cooperative fuzzy model predictive control (CFMPC) for heating and cooling of buildings. Because of different supply zones, the large time constants and the non-linear building dynamics with respect to the different seasons, a CFMPC concept is proposed. The overall non-linear building is split into different zones, which are consisting of input-coupled Takagi-Sugeno (TS)-fuzzy models. Each such TS-fuzzy model is constituted by a local linear model network (LLMN). The LLMN consists of local linear models (LLM), which are representing the different seasons: winter, transition season (fall and spring), and summer. The control of each LLM is realized by model predictive control (MPC). For each building zone the associated MPCs are output-blended by the fuzzy membership functions, which leads to fuzzy model predictive control (FMPC). In addition to the FMPCs a global MPC is controlling the thermally activated building systems, which affect all other zones. To coordinate the different controllers a cooperative iteration-loop is assumed, which leads to cooperative fuzzy model predictive control (CFMPC). The concept is developed for a specific demonstration building and can be easily adapted for other complex buildings. A simulation example demonstrates that the proposed CFMPC achieves a performance increase with less energy consumption, as compared to FMPC controllers and historical measured data of the demonstration building. [ABSTRACT FROM AUTHOR]

Heating, ventilating, and air-conditioning (HVAC) systems consume almost half of the total energy consumption in buildings. In order to reduce the energy consumption of HVAC systems in buildings, different passive heating and cooling strategies and thermal energy storage systems have been adopted. Water wall is an excellent short-term thermal energy storage system which can be used to maintain thermal comfort in buildings while reducing the heating and/or cooling load of the buildings. A significant amount of research work on water wall has been carried out since the 1980s. This paper presents a comprehensive review of the previous studies of water wall systems, focussing mainly on the performance of various configurations of water wall systems and the different research approaches adopted in the literature. The advantages and disadvantages of the different research approaches have been highlighted. It is revealed that the existing water wall research has been based mainly on an energy balance model and experimental modelling, but CFD (computational fluid dynamics) modelling has attracted little attention. Moreover, this review has identified several gaps in the water wall research for further attention. [ABSTRACT FROM AUTHOR]

Energy signatures for air conditioning systems can have characteristics which are not seen with heating systems. This paper explains and illustrates some of the characteristics that are specific to air conditioning systems and describes how energy signatures that take account of them can be applied to produce benchmarks, control charts and diagnostic information. It focusses on the use of energy signatures derived from measured daily system energy consumption. Daily energy signatures can generate more robust energy consumption benchmarks and provide additional insight into unusual energy demand patterns compared to monthly or weekly signatures, albeit requiring slightly more data. In particular, they distinguish between weekday and weekend consumptions. They can be used to generate benchmarks based on standardised annual consumption or standardised annual load factor. In addition they can be used to generate control charts to identify days of unusual consumption for individual systems. More sets of daily energy consumption data are needed to evaluate their diagnostic power. [ABSTRACT FROM AUTHOR]

Ground source heat pump systems have been proved to be one of the most efficient systems for heating and cooling in buildings. However, an optimal energy performance depends on a good control of the auxiliaries, which stand for an important part of the total energy consumption. The authors previously developed an experimental in situ optimization methodology for the water circulation pumps frequency of ground source heat pump systems when single stage and multi-stage ON/OFF regulation is employed. However, the user comfort was not completely met under extreme weather conditions during summer. This paper presents the upgrading of this energy optimization strategy combining circulation pumps frequency variation and building supply temperature compensation in order to ensure the user comfort while keeping high energy savings. Experimental results show that the user comfort is met by means of this new methodology and the energy savings (33%) are even higher than those obtained with the previous methodology. [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]

Energy demand for heating and cooling of buildings can be minimized through usage of thermal energy storage (TES) systems in building materials. TES in microencapsulated phase change materials provides a new solution to thermally regulated energy efficient buildings. This study summarizes the investigations and analysis of microencapsulated PCMs for building applications. Microencapsulated phase change materials (MPCMs) can be incorporated with many materials that are commonly used in building construction. This paper provides overview of various encapsulation techniques, test methods for MPCMs as well as applications of MPCMs in buildings. There are several micro-encapsulation methods by which the microcapsules of a wide range of sizes between 0.05 μm and 5000 μm can be produced. The MPCM incorporated with concrete, mortar, plaster and other materials have a significant potential to increase the thermal capacity of the mixture. Several authors reported testing of building materials with MPCM. Though the increase of thermal capacity with addition of MPCM is significant the decrease of mechanical properties, such as compressive strength, is relatively small. [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]

Phase change materials can be integrated in building walls to reduce heating energy consumption. However, proper design of the composite material requires a lot of complex calculations. In this paper, we present a methodology based on metamodeling in order to properly design phase change material composite solutions. A low-energy house example is chosen to develop our methodology, simulations being carried with TRNSYS. Box–Behnken design of experiments is used for data sampling in order to be able to produce a polynomial metamodel. First, the metamodel allows to have a profound understanding of the parameters influence: melting temperature, thickness, latent heat, density and thermal conductivity. Second, it is possible to extract from the polynomial form the optimal material properties. Third, the metamodel can be used to design or test different material solutions. Based on this methodology, it is possible to build a simple tool that can be used by architects and engineers. [ABSTRACT FROM AUTHOR]

• A new methodology to investigate the impact of thermal mass is defined. • The use of unrepresentative boundary conditions could lead to inaccurate conclusions. • High thermal mass helps to decrease and regulate the internal temperature. • High thermal mass could increase energy use in the summer and winter seasons. • Isolating thermal mass through internal insulation results in better energy performance than external insulation. Contradictory conclusions have been reported on whether thermal mass reduces or increases energy demand in hot and cold climates. A novel approach to measuring the impact of thermal mass on the building's energy consumption is presented. The method aims to better represent reality and applies two different control conditions simultaneously in a numerical model: the first condition, which has been used in past studies, adjusts the internal boundary condition based on the time duration of heating/cooling activation (simulating an occupancy pattern) and the second, which has not been used in past studies, adjusts the internal boundary condition based on both the time duration and the internal temperature (simulating an occupancy pattern and the thermostatic control system). When investigating the impact of thermal mass on the internal temperature in a scenario where no heat is transferred into the building, the high thermal mass outperforms the low thermal mass, showing a time-shifting effect, long time lag, and small decrement factor. However, when modelled using the method presented in this paper, high thermal mass results in greater energy consumption during summer and winter periods in Saudi Arabia. During transition seasons where temperature swings occur on either side of the indoor set-point temperatures, thermal mass reduces thermal transmission. The impact of thermal mass is also investigated for several climatic conditions in Saudi Arabia. Simulation results show that an internally exposed thermal massive wall section results in greater energy consumption when compared to a similar building with isolated thermal mass (i.e. insulated internally). This is due to the fact that even though the internal temperature inside the building is being cooled/warmed up to the set-point, the thermal mass continues to transfer heat that is absorbed by the building's fabric from/to the interior, placing a greater demand on the cooling/heating system. Over the course of a year, however, the impact of thermal mass is negligible when compared to other factors, such as the insulative properties of the building's fabric. [ABSTRACT FROM AUTHOR]