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This paper presents the evaluation of the performance of a ground source heat pump system monitored plant providing heating/cooling to an office building located in the Universitat Politècnica de València in Spain. The system was designed using GLHEPRO software and it has been monitored since 2005. Once a ground source heat pump has been designed, it is important to analyze its performance along the years after its construction and check whether the design was appropriate and the simulation predictions were consistent with real experimental measurements. This paper first presents the impact of the GSHP system in the ground thermal response. The simulations obtained in GLHEPRO software will be analyzed and compared to experimental measurements. The second purpose of this work is to compare the performance simulation results of a complete ground source heat pump system model built in TRNSYS, with the experimental measurements which have been registered and collected for one cooling day. Numerical predictions and experimental results are compared and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Due to the unique properties of near-critical fluid, trans-critical/supercritical CO2 based natural circulation loop (NCL, or thermosyphon) has been proposed in many energy conversion systems, such as solar heater, waste heat recovery, next generation nuclear cooling, etc. This paper presents an experimental investigation of a near-critical CO2 thermosyphon. The closed thermosyphon is specially designed for high pressure experiments, where natural convection is achieved only by heating and cooling of fluid in the loop. The system is operated in wide range of pressures from around 6.0 to 15.0MPa in the near-critical region. It is found that the NCL flow will change from unstable sub-critical two-phase flow to stable liquid flow, and then become stable supercritical circulation with the increase of system initial pressure. The heat transfer behaviors are analyzed for stable flow conditions mainly for supercritical region. General variations of the fluid temperature, mass flow rate and loop pressure are presented in this paper. In the steady supercritical region, the heat transfer performance of the cooler show very small changes with bulk mean fluid temperature, and at the heater better heat transfer is found for conditions close to the pseudo-critical point. The heat transfer dependency on operation pressure and evolution mechanisms are also discussed in detail in this paper. [Copyright &y& Elsevier]

[Display omitted] This paper introduces a non-linear grey-box (GB) model based on stochastic differential equations that describes the heat dynamics of a school building in Denmark, equipped with a water-based heating system. The building is connected to a local district heating network through a heat exchanger. The heat is delivered to the rooms mainly through radiators and partially through a ventilation system. A monitoring system based on IoT sensors provides data on indoor climate in the rooms and on the heat load of the building. Using this data, we estimate unknown states and parameters of a model of the building's heating system using the maximum likelihood method. Important novelties of this paper include models of the water flow in the circuit and the state of the valves in the radiator thermostats. The non-linear model accurately predicts the indoor air temperature, return water temperature and heat load. The ideas behind the model lay a foundation for GB models of buildings that use different kinds of water-based heating systems such as air-to-water/water-to-water heat pumps. Such GB models enable model predictive control to control e.g. the indoor air climate or provide flexibility services. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dynamic evaluation of economic and energy benefits due to thermostatic valve installation. • Dynamic evaluation of economic and energy benefits due to heat metering installation. • The adoption of both thermostatic valves and heat metering least to a payback period lower than 2 years. • Analysis carried out considering several shapes of typical building. The aim of this paper is to propose a novel approach in order to accurately calculate the energy and economic savings due to the use of heat metering and thermostatic valves in residential buildings. The paper aims at proving that the present simplified approaches used in European Legislation may lead to significantly underestimate the profitability of this technology. The study is developed for four different typologies of buildings located in the city of Naples (South of Italy), including their geometrical and thermophysical properties. The buildings are first modelled in Google Sketchup and subsequently linked to the TRNSYS environment, which also includes a detailed model of the piping systems. The models allow one to evaluate, for every period of the year, energy demand, energy supplied by radiators, heat gains, transmission, etc. The developed models are used to calculate energy demands for three scenarios for each type of building: centralized heating systems not equipped with heat metering; thermostatic valves without heat metering; heat metering and thermostatic valves. The possible savings related to thermostatic valves and heat metering are estimated using the developed model. The results are compared with the ones provided by the Italian Standards. Results show that the thermostatic valves adoption leads to a significant reduction, up to 50%, of the thermal energy demand of the residential buildings and that all the proposed systems exhibit a remarkable economic profitability, with a payback period lower than 1.7 years. [ABSTRACT FROM AUTHOR]

Abstract: In this paper an inverse boundary design problem of combined natural convection–radiation is solved. The aim of this paper is to find the strength of heaters in a step-like enclosure to produce desired temperature and heat flux distribution on the design surface. The finite volume method for transition flow (which causes a faster convergence) is used as the direct solver of the energy and momentum equations. The SIMPLE algorithm is utilized to satisfy pressure–velocity coupling in order to solve the free convection heat transfer. Also, the backward Monte Carlo method is employed in order to be able to compute the distribution factors and carry out the radiant exchange calculations. Finally, the goal function which is defined on the basis of square root error is minimized by means of conjugate gradients method. The effects of variation of range of parameters such as the Rayleigh number, temperature ratio, radiation conduction parameter and the emissivity coefficient of insulated surfaces on the relative root mean square and heat flux are investigated and results are compared. The results demonstrate the efficiency and the accuracy of the proposed method. [Copyright &y& Elsevier]

Abstract: Experimental measurements in a spray cooling test rig were carried out for two different heater surface roughnesses and for two different types of nozzles with the dielectric refrigerant R134a. In this paper, results of the sprayed refrigerant film thickness measurements are presented. The influence of the volumetric flow rate, the surface roughness and the type of nozzle (through the spray parameters) on the total average film thickness is analyzed and discussed. In a companion paper, results of the heat transfer measurements are presented. It has been found that there is a relation between the variations of the average Nusselt number and of the film thickness along the spray cooling boiling curve. The heat transfer regimes along that curve are related not only to a variation in the average Nusselt number but also to changes in the film thickness. The qualitative analysis of those variations served to better understand the heat transfer mechanisms occurring during the spray cooling. [Copyright &y& Elsevier]

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: The contact condition between the welding tool and the workpiece in friction stir welding (FSW) is believed to be critically important to understand the heat generation and material flow behaviour. Both of these are difficult to study experimentally. In previous simulation studies, the contact conditions that occur during FSW are generally described as stick and/or slip, according to different methodologies but these descriptions have their limitations. In the study described in this paper, the thermal and mechanical outcomes from models with prescribed stick and slip conditions were compared to identify the results and drawbacks of assuming different contact conditions. This paper presents a new combination method for characterising the contact conditions that occur during FSW. This new method yields more reasonable heat generation estimates, as validated by the experimental thermal measurements. [Copyright &y& Elsevier]

Abstract: The paper critically reviews and explores the impact of renewable energy heat policies to induce technological change in Ireland. It is in response to the challenge of better understanding the broad effects and attributes of renewable energy policy instruments in Ireland and beyond. Using the Irish residential sector as a case study, and analysing data of more than 31,600 technology installations under the Irish Government''s Greener Homes Scheme [GHS], the paper assesses the extent to which policy makers may be informed of the willingness of consumers to adopt these technologies in their homes. In doing so, it attempts to provide valuable guidance for policy evaluation in relation to renewable energy in the residential sector. It represents investment decisions and technological choice by the end user and reflects the growing concern among energy policy markets regarding the representation of user preferences. The overall intent is to investigate the implications of analysing different variables and their contribution to making more balanced renewable energy policies. It provides a critical analysis of the Greener Homes Scheme, the key instrument for implementing Ireland''s renewable heating policy from 2006 to 2010, established to induce technological change within the residential sector. In assessing the impact of the Scheme, attention focuses on decision frameworks for technological choice and the treatment of market and behavioural failures. It considers how consumers have responded to new technological policies aimed at deploying renewable heat technologies, and the specific policies aimed at advancing certain technologies over others. Through a case study investigation, the paper explores the relationship and dependencies that influence consumers'' decision-making regarding the choice of renewable energy heating technologies in the domestic sector in Ireland. Consumer preferences and their subsequent investment decisions, motives and technological choice are reflected. It concludes that while economic factors are important, a much broader variety of determinants is required when analysing the process of adoption of technology. [Copyright &y& Elsevier]

Abstract: With the development of urbanization in China, more and more high-rise residential buildings are constructed, mostly with 10–15 stories. Solar water heating system has been widely used in low-rise residential buildings in China, while its application in high-rise apartment is still in the initial stage. In this paper, the current application situation of solar water heating system in urban residential buildings of China is investigated. Additionally, demonstration projects of high-rise residential building are introduced, in which the application feasibility and limitation of solar water heating system are emphasized and some appropriate planning types of that are discussed. Finally, this paper analyzes the applicability of solar water heating systems integrated design in typical high-rise apartments from various aspects (such as architectural elevation, architectural plane and detailed construction) in the planning and designing phase. [Copyright &y& Elsevier]

Abstract: This paper presents a new calculation of neutral gas heating by precipitating auroral electrons. It is found that the heating rate of the neutral gas is significantly lower than previous determinations below 200km altitude. The neutral gas heating arises from the many exothermic chemical reactions that take place from the ions and excited species created by the energetic electrons. The calculations show that less than half the energy initially deposited ends up heating the neutral gases. The rest is radiated or lost in the dissociation of O2 because the O atoms do not recombine in the thermosphere. This paper also presents a new way of calculating the heating rate per ionization that can be used for efficient determination of the overall neutral gas heating for global thermosphere models. The heating rates are relatively insensitive to the neutral atmosphere when plotted against pressure rather than altitude coordinates. At high altitudes, the heating rates are sensitive to the thermal electron density and long-lived species. The calculations were performed with the Field Line Interhemispheric Plasma (FLIP) model using a 2-stream auroral electron precipitation model. The heating rate calculations in this paper differ from previous heating rate calculations in the treatment of backscattered electrons to produce better agreement with observed flux spectra. This paper shows that more realistic model auroral electron spectra can be obtained by reflecting the up going flux back to the ionosphere at the upper boundary of the model. In this case, the neutral gas heating rates are 20%–25% higher than when the backscattered flux escapes from the ionosphere. [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: Establishing adequate technical and physical boundary conditions for a sustained nuclear fusion reaction is a challenging task. Phased feedback control and monitoring for heating, fuelling and magnetic shaping is mandatory, especially for fusion devices aiming at high performance plasmas. Technical and physical interrelations require close collaboration of many components in sequential as well as in parallel processing flows. Moreover, handling of asynchronous, off-normal events has become a key element of modern plasma performance optimisation and machine protection recipes. The manifoldness of plasma states and events, the variety of plant system operation states and the diversity in diagnostic data sampling rates can hardly be mastered with a rigid control scheme. Rather, an adaptive system topology in combination with sophisticated synchronisation and process scheduling mechanisms is suited for such an environment. Moreover, the system is subject to real-time control constraints: response times must be deterministic and adequately short. Therefore, the experimental tokamak device ASDEX Upgrade employs a discharge control system DCS, whose core has been designed to meet these requirements. In the paper we will compare the scheduling schemes for the parallelised realisation of a control workflow and show the advantage of a data-driven workflow over a managed workflow. The data-driven workflow as used in DCS is based on signals connecting process outputs and inputs. These are implemented as real-time streams of data samples. Consequently, real-time signal management forms the foundation of DCS. The paper explains the principal features such as tagged samples, signal groups, algorithmic blocks and processes as well as scheduling schemes which allow DCS control applications to be defined as self-contained modular building blocks glued together by a software framework. By virtue of this sound foundation, DCS is a mature but still evolving system for reliable, distributed control of an entire tokamak device coordinating and monitoring 20 diagnostic systems, 14 magnetic power supplies, 5 heating systems with a total power of more than 25MW, 8 gas fuelling channels, a pellet injector and a killer gas gun. [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: The aim of this paper is to contribute to the knowledge about energy use in residential buildings. Field measurements were carried out in 57 electrically heated Swedish single-family houses, where the total energy use (i.e. electricity use for space heating, household electricity and electricity use for hot water production), indoor temperatures and water use were recorded during four winter days. Some of the findings were that differences for households’ total energy use of similar houses were large. The characteristics of load curves clearly differ between weekdays and weekend days. The water use differs greatly for the households. This paper is part of a larger project where time use diaries were used in order to further link the energy use to residents’ every day energy related behaviours. To get a better understanding of the energy use in our homes is a prerequisite to be able to both recognise the problems as well as the potentials of reaching energy goals of our society, leading to a decreased impact on the environment from the building sector. [Copyright &y& Elsevier]

Abstract: To decrease the regeneration temperature of silica gel (an excellent desiccant), the non-heating regeneration method with ultrasonic has been proposed and studied in our previous papers in which the effect of acoustic parameters as well as drying air temperature on the regeneration process was investigated experimentally by desiccant-weighing method. In this paper, the effect of drying air temperature and humidity on the ultrasonic-assisted regeneration and the following adsorption features of silica gel will be further studied by measuring the states of drying air. Different inlet air conditions, i.e., 40, 50, 60 and 70 °C in temperature combined with 0.01, 0.015 and 0.02 kg/(kg dry air) in humidity, are designed for the experimental study. The mass of dry silica gel sample used in this study is measured as 175 ± 0.1 g, and the acoustic frequency and power of ultrasound are 23 kHz and 60 W, respectively. The two indexes, AERR (Average Enhancement Ratio of Regeneration) and AERA (Average Enhancement Ratio of Adsorption), are used to estimate the effect of ultrasonic on the regeneration and the following adsorption of silica gel. The experimental results show that the effect of ultrasound on the regeneration will first rise and then decline when the drying air temperature rises from 40 °C to 70 °C, while it decreases with the drying air humidity increasing from 0.01 to 0.02 kg/(kg dry air). Similar regular patterns can be found for the effect of regeneration assisted by ultrasonic on the adsorption of silica gel. Meanwhile, a theoretical model is developed to predict the regeneration rate of silica gel assisted by ultrasound and validated by experiments. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a computational study on the energy consumption and related CO2 emissions for heating and cooling of an office building within the Urban Heat Island of London, currently and in the future. The study developed twenty weather files in an East-West axis through London; the weather files were constructed according to future climate change scenario for 2050 suitable for the UK which have been modified to represent specific locations within the London UHI based on measurements and predictions from a program developed for this purpose (LSSAT). The study simulated an office with typical construction, heat gains and operational patterns with an advanced thermal simulation program (IESVE). The predictions confirm that heating load decreases, cooling load and overheating hours increase as the office location moves from rural to urban sites and from present to future years. It is shown that internal heat gains are an important factor affecting energy performance and that night cooling using natural ventilation will have a beneficial effect at rural and city locations. As overheating will increase in the future, more buildings will use cooling; it is shown that this might lead to a five-fold increase of CO2 emission for city centre offices in London in 2050. The paper presents detailed results of the typical office placed on the East-West axis of the city, arguing the necessity to consider using weather files based on climate projections and urban heat island for the design of current buildings to safeguard their efficiency in the future. [Copyright &y& Elsevier]

Abstract: The article described the dilatancy technology of district heating system with high-temperature heat pump (HTHP). For the exploitation of low-temperature return network sources, a high-temperature heat pump with a heat exchanger was planned. As the core technology of the dilatancy district heating system, HTHP units and heat exchanging systems had been described detailedly through theoretical and experimental analysis. The model was proved to be in good agreement with the experiment data. It could be used for engineering design. In this paper the district heating system in Datong was taken as a case study. The main characteristics of the dilatancy district heating system had been presented in the form of diagrams. The principal advantage of dilatancy technology in the district heating system lies in increasing the temperature difference, reducing the diameters and the initial investment of primary side network. This paper shows clearly the analysis of the dilatancy technology for characterising and improving the performance of district heating systems. [Copyright &y& Elsevier]

Abstract: In certain building applications, the PV installation is extended to cover also south- or west-facing walls, taking care to circulate cooling air to the back of the panels. The cooling effect maintains a high conversion efficiency of the PV panels and the heated air may be exploited by the HVAC or service water heating system. Sizing and design of the double façade system is critical to its energetic performance. In this paper, the results from flow visualization and hot wire anemometry measurements performed on the basic structural module of a double-skin photovoltaic (PV/T) façade are discussed. The concept and its feasibility have been presented in a previous paper. The results of transient outdoor measurements with the testing device have been reported elsewhere. The air flow and turbulence field inside the cavity is analyzed in the present paper by means of indoor measurements with the testing device. The results are combined with CFD computations to calculate heat transfer coefficients and improve our understanding and modeling of the specific PV/T concept. [Copyright &y& Elsevier]

Abstract: In this paper, a series of fire tests on restrained composite slabs, carried out at the University of Manchester, is presented. A total of six composite slabs were tested under different fire scenarios, with different load ratios. The tests were particularly concerned with the variation of internal forces within the slabs during both heating and cooling phases. In addition to the testing programme, two separate nonlinear finite element models have been developed to simulate the thermal and mechanical behaviour of composite slabs during heating and cooling, which is introduced in detail in this paper. In the thermal analysis model, plane elements were adopted to obtain a detailed thermal behaviour. In the structural analysis model, the concrete, steel deck and mesh were simulated by solid elements, shell elements and truss elements respectively. The interaction between the concrete and steel sheet was simplified to spring elements. According to the experimental results and FE modelling, the behaviour of composite slabs was analysed in detail. At last, the parametric study was performed where the effect of concrete strength, steel deck thickness and mesh size was analysed. [Copyright &y& Elsevier]

Abstract In this paper, the full repowering of a steam Power Plant with a capacity of 320 MW in Iran was evaluated technically and economically. Implementation of this plan for the target power plant was selected because of its over 30 years of age. Due to the presence of steam flash feed water preheaters and the possibility of preheating feed water entirely or partially prior to entering heat recovery steam generator, the effect of using or not using these low and high pressure equipment was evaluated in different cases. To do this, five different cases were proposed and reviewed. Considering the available gas turbines in Iran, the gas turbines models Siemens V94.2 and V94.3A were selected. In each case, the optimum point is obtained in terms of the lowest cost of electricity generation. Finally, after reviewing the results of all cases, full repowering plan with parallel feed water heating was selected as the best alternative in terms of energy and exergy efficiencies and the price of generating electricity. If two heat recovery steam generators and two V94.3A gas turbines are used, the net exergy and energy efficiencies for the cycle can reach 54.49% and 52.98%, respectively. Moreover, the power capacity of a repowered unit is equal to 700.44 MW with electricity generation price of 0.05986 $/kWh. Graphical abstract Image 1057 Highlights • In the present study, a real power plant has been studied (A Case Study). • The five different arrangements of feed water heaters for proposed scenarios have been considered. • The merging of water-gas heat exchangers with existing preheaters has been investigated. • Optimum techno-economic case for repowering has been presented. [ABSTRACT FROM AUTHOR]

Abstract Flexoelectricity - the coupling between electric polarization and strain gradient - is an effect which promises intriguing applications at nano-scale. Strong strain gradients that appear in nano-sized and nano-structured systems lead to electric polarisation, as in analogy to piezoelectricity but without restrictions on the material symmetry. In contrast to piezoelectricity, the theoretical treatment of the flexoelectric effect is a challenging issue where a number of bulk, surface, static and dynamic contributions are encountered. Combined with other effects, this provides the possibility of additional, non-trivial couplings. In this paper, we address thermo-electric effects arising in an inhomogeneously heated sample. The theory is developed using variational principles and applied describing the polarization response in an inhomogeneously heated thin plate. We demonstrate that the effect can be used for the conversion of waste heat into electric power, up to tens of Watts per kilogram of the flexoelectric material. [ABSTRACT FROM AUTHOR]

Highlights • Optimal-sized building-integrated/attached PV systems on roof and facade break-even. • The cost saving potential of PV is highly dependent on the interest rates and the retail price development. • Gas heating remains the cheapest option compared to pellet heating, heat pump and district heat. • Energy cost reductions achieved by better building quality cannot compensate for the initial renovation costs (passive retrofitting). Abstract Multi-apartment buildings comprise almost half of the European housing stock and are for the most part old and energy inefficient, making active retrofitting an important topic. The objective of this paper is to determine the profitability and optimal size of different technology portfolios for renewable building energy. A mixed-integer linear programming optimisation model is developed in Matlab with the objective of maximising the Net Present Value over a time horizon of 20 years. To examine multiple use cases, a modular approach is used for realising different multi-apartment building set-ups. Building-attached and building-integrated photovoltaic systems on different parts of the building skin already achieve break-even. Heat pumps, pellet and district heating can hardly compete with gas heating yet. However, heat pumps have synergy effects with PV systems, thus reinforcing their implementation, as does a tenant portfolio with a good correlation with the sunshine hours. The profitability gap between investment costs for passive building renovation and resulting energy cost savings is significant. However, it is the smallest for buildings with quality standards. In conclusion, governmental subsidies and financial incentives such as the true cost pricing of CO 2 emissions are necessary to trigger investments in reasonable combinations of passive and active retrofitting measures. [ABSTRACT FROM AUTHOR]

Highlights • Detailed experimental research on viscosity of microencapsulated phase change material (mPCM) slurry during heating. • Experimental results for two constant shear rate and different: mPCM concentration; rate of temperature increase. • A visible influence of phase change process on dynamic viscosity of mPCM slurry. Abstract With the advancement of technological progress it is possible to close Phase Change Material "inside" capsules of the order of micro- and even nano-meters. Microcapsules added to a base liquid can be used as latent functionally thermal fluid (LFTF) in active heat exchange systems. Accurate recognition of the rheological properties of the resulting suspension, especially at the phase change temperature of the PCM, is essential for the planned practical application of the fluid. Knowledge of viscosity is one of the key parameters as this is reflected in both flow resistance and, for example, convective heat exchange. This paper presents the results of detailed tests on the viscosity change of the microencapsulated PCM slurry (Micronal® DS 5039 X – BASF product) at unsteady state conditions. The effect of the temperature increase rate (0.1–1.2 °C/min), mPCM concentration (80%, 90% of Micronal® DS 5039 X in water and pure Micronal® DS 5039 X) and the influence of spindle speed (50 RPM and 150 RPM) on mPCM slurry apparent viscosity was examined. Because the main peak melting temperature of the product is around 23 °C the temperature range of experiment was 15–30 °C. On the basis of the conducted tests, it was found that in general the temperature increase of the suspension causes a decrease of its viscosity, however a temporary increase in the viscosity of the slurry was observed when the PCM contained in the microcapsules undergoes a phase transition. [ABSTRACT FROM AUTHOR]

• The thermal energy flow model with time delay under CF-VT for DHN is proposed. • The model for DHN under different heating regulation modes is distinguished. • An optimal scheduling strategy of DIHPS under VF-CT and CF-VT is proposed. • The total thermal capacity of buildings is less under CF-VT than VF-CT. • Thermal inertia of DHN restrict flexibility of DIHPS with multiple energy stations. Utilizing multiple energy supply solutions and the thermal inertia of buildings are considered as an efficient method for improving energy conservation and the operational flexibility of Combined Heat and Power (CHP) for wind power integration in a district integrated heat and power system (DIHPS). However, to truly take advantage of these, many factors such as the energy price, the variable efficiency of devices, and especially the different heating regulation modes (the quantity regulation and the quality regulation mode) are imperative to be considered for variable situations of the practical project. Therefore, in this paper, an integrated hydraulic-thermal model of the district heating network (DHN) under the quantity regulation mode is introduced, and a novel thermal energy flow model with transmission time delay under the quality regulation mode is firstly proposed to simulate the dynamic thermal energy distribution of the DHN with multiple heat sources. Then, in terms of different heating regulation modes, the different thermal capacity of buildings to increase the flexibility of the DIHPS is studied. Moreover, an optimal scheduling method considering different energy stations and the thermal inertia of buildings under different heating regulation modes is proposed to guide the operation of the DIHPS in variable actual engineering applications for the sake of operational economics and wind power utilization. Finally, numerical cases have been compared based on a modified testing system. The results demonstrate that under the quantity regulation mode the coordination of energy stations effectively reduces the daily operation cost by 17.4%. The thermal inertia of buildings give a saving rate of 6.4% and he penalty cost of wind power is reduced by 36.3% further. Moreover, the total thermal capacity of buildings to reduce the operation cost and the wind power curtailment is less under the quality regulation mode. It results that the daily operation cost increases by 4.1%. In addition, towards the DIHPS with multiple energy stations in our case, the thermal inertia of pipes cloud not reduce the daily operation cost. [ABSTRACT FROM AUTHOR]

Highlights • A scalable and smart HVAC control approach. • An IoT architecture and prototype for implementing the control. • Deployment results in a test-bed. • Implementation aspects with IoT and legacy BMS. Abstract Scalability of control algorithms used for savings energy in commercial building Heating, Ventilation and Air-Conditioning (HVAC) system and their implementation on low cost resource constrained hardware is a challenging problem. This paper presents the Internet of Things (IoT) prototype which implements a smart and scalable control approach called the Smart-Token Based Scheduling Algorithm (Smart-TBSA) to minimize energy in commercial building HVAC systems. The IoT prototype is formalized with an architecture that encapsulates the different components (hardware, software, networking, and their integration) along with their interactions. A detailed description of the different components, hardware design, deployment issues, and their integration with legacy systems as well as cloud-connectivity is presented. In addition, simple modifications required for transforming the optimization models to an active control technique is also presented. While scalability is provided by the decentralized control, recursive zone thermal model identification, prediction occupant's thermal sensation, and embedding them within the optimization models enhances the smartness. Consequently, due to the implementation of Smart-TBSA using IoT devices, an otherwise centralized control architecture of the legacy building automation system is transformed to a more scalable and smart decentralized one. The proposed Smart-TBSA and IoT prototype are illustrated on a pilot building in Nanyang Technological University, Singapore having 85 zones. Our results shows that by combining IoT with decentralized control, energy savings up to 20% can be derived. Moreover, we show that legacy building automation system can be transformed into a more smart, adaptable, scalable, and decentralized control by deploying IoT devices without incurring significant costs. [ABSTRACT FROM AUTHOR]

Abstract This paper numerically investigates the influence of masonry infill walls on collapse mechanisms of steel frames under fire scenarios. Three six-story by five-bay steel frames were designed in this study. One of these frames had no infill walls, another one had horizontal infill walls, and the last one had vertical infill walls. Load redistribution and fire resistance were investigated under edge bay fire scenario and central bay fire scenario. The numerical results indicated that masonry infill walls provide alternate load paths in fire conditions, causing significantly large variations of axial forces in surrounding columns. Furthermore, the lateral resistance of the infilled frames is provided by the integral loading resisting system under edge bay fire scenario. The infill walls decrease the buckling temperature and increase the collapse temperature of the heated columns. A series of parametric analyses were performed to investigate the factors influencing the fire resistance of the steel frames. Finally, a preliminary design method was proposed with an aim to prevent the collapse of steel frames with infill walls under fire scenarios. Highlights • Provide numerical investigation on fire-induced collapse mechanisms of steel frames with masonry infill walls. • Infill walls enhance integrity of the steel frames, resulting in an integral loading resisting system against edge bay fire. • Infill walls reduce the buckling temperature of the heated columns, whereas makes the frame resist collapse longer. • Propose a preliminary design method for using masonry infill walls to prevent fire-induced collapse of steel frames. [ABSTRACT FROM AUTHOR]

Abstract Ceramic Regenerative Storage Heater (RSH) is the preferable solution to provide clean hot air in Hypersonic Wind Tunnel (HWT) and Scramjet Test facilities to prevent the liquefaction of air during expansion in the high Mach number nozzles. Selection of the heater storage material for such operational requirements is a challenging task. As per the theoretical background; alumina, zirconia or mullite compositions have the capability to withstand at such high operating conditions. In the current study, a series of experiments were carried out to estimate the thermal characteristics of the material. This paper highlights the simplified approach by combining theoretical and experimental methods for economic (reduced time and cost) selection process of high temperature material. The desired material must possess good thermal shock resistance and low dust generation characteristics. Al 2 O 3 and SiO 2 based matrix composition fused in a transcrystalline phase exhibits significant improvement on the overall material integrity. Several Al 2 O 3 and SiO 2 matrix compositions were examined and the final matrix composite ratio of 90% of Al 2 O 3 and 10% of SiO 2 is considered as the desired candidate material. The ceramic matrix was sintered at a temperature of 2123 K, under the specific pressure of 1400 kg/cm2 for a period of 2 h, at a heating rate of 3.5 °C/min. The results of the thermal shock tests on various samples are presented. To improve the anti-dust characteristics, the final samples were coated with fine particles (5 µm) of Al 2 O 3 and SiO 2 matrix. Based on the experimental evaluation, Al 2 O 3 and SiO 2 fused matrix composition found to be meeting all the requirements of high temperature storage material. Highlights • Identification of suitable high temperature regenerative ceramic materials. • Realization of samples of different compositions and grain size combinations. • Impact of the brick geometry on thermal shock and overall size of the heater. • Establishment of methods to test and assess the usability of ceramics for RSH. • Thermal cyclic tests and measurement of the material response for RSH conditions. [ABSTRACT FROM AUTHOR]

Highlights • A two-phase flow visualisation and heat transfer experiment bench was established. • Flow patterns at various crank angles in an open cooling gallery were captured. • The effects of motor speed and heating on flow patterns were discussed. • The temperature distribution was obtained and the effect of speed was discussed. • Transition from laminar flow to turbulent flow has been identified. Abstract The demand of increasing power density of the Internal Combustion Engine promotes the technology development using internal cooling gallery of the piston. The oil flow and heat transfer performance of the piston internal cooling gallery have great influence on the cooling performance, which affects the thermal conditions of the piston and of the entire engine. The experimental study using visualising method is therefore critical and important to observe the flow patterns inside the piston gallery. In this paper, we presented the visualised study of two-phase flow patterns within an open cooling gallery by using a high-speed camera at various crank angles. The effects of motor speed both on the flow patterns and temperature distribution were investigated and the heat transfer mechanisms in gas-liquid two-phase flow during reciprocating motion were explored. Based on the study, the period-doubling phenomenon, which represented the transition from laminar flow to turbulent flow, was observed when the speed was around 400–500 rpm. Results indicated the increase of motor speed can effectively improve the cooling performance. Results also showed when the speed was higher than 600 rpm, the reduction of temperatures was quite close, which proven the existence of optimal or minimum requirement of motor speed to achieve good quality cooling performance. The results obtained in this study could be used as a critical reference for numerical studies and important experimental reference to further investigate the design and optimisation of engine cooling gallery for vehicle application. [ABSTRACT FROM AUTHOR]

Abstract Semiconducting single-walled carbon nanotube (s-SWNT) arrays attract much attention due to the ideal configuration for high performance electronics. A recent approach based on the nanoscale thermocapillary flow enabled the achievement of aligned arrays of highly purified s-SWNTs by removing the metallic SWNTs (m-SWNTs) in as-grown arrays by direct pulsed current injection. Thermal management of this process is critically important since the cumulative heating from the m-SWNT array yields a high temperature increase to cause the difficult control of thermocapillary flow. In this paper, an analytical heat transfer model combining a two-dimensional transient thermal model and a three-dimensional steady state thermal model is established for predicting the temperature increase of the SWNT array under a pulsed current injection with a period step function. The analytical predictions agree well with three-dimensional finite element analysis. Effects of parameters (such as duty cycle, period, spacing, etc.) on the temperature distributions and the maximum temperature increase are investigated systematically. These results can help guide the purification process to reduce the adverse thermal effects to obtain highly purified s-SWNTs. Highlights • An analytical thermal model is established for the aligned arrays of metallic single-walled carbon nanotubes by pulsed heating. • The analytical thermal model combines a two-dimensional transient analysis and a three-dimensional steady state analysis. • Effects of loading and geometric parameters on the temperature distributions and the maximum temperature increase are studied. • These results can help optimize the process to purify the horizontally aligned single-walled carbon nanotubes. [ABSTRACT FROM AUTHOR]

Abstract The goal of this paper is to evaluate the advantages achieved through the adoption of low impact energy saving strategies for an independent natural gas fired boiler heating system in a recently built residential building in Rome. For this purpose, an existing apartment was selected as a case study and dynamically simulated in TRNSYS with which the model was validated. Low impact retrofit solutions and heating system management were considered as possible solutions to achieve energy savings. The chosen retrofit solutions consist of envelope elements replacements and building automation controls improvement while heating system management depends on occupants' behavior. Overall, 36 scenarios were considered, starting from the combination of 3 comfort temperature set-points, 2 insulation levels for transparent components, 2 types of zone comfort set-point control with 3 dead-band temperatures. Each case is evaluated in terms of energy results and economic results. The simulation results provide energy savings up to 44% when windows are replaced lowering their transmittance nearby 32%. The choice of a proportional control for zone temperature set-point compared to a simple on-off control guarantee energy saving up to 39% when temperature set-point is low (19 °C) and controls dead-band is 0.5 °C. The effect of different temperature control dead-bands is higher when proportional controls are adopted (up to 40% passing from 2 to 0.5 °C dead-band for 19 °C set-point). Energy consumption reductions up to 63% are achieved if the indoor temperature set-point is lowered 2 °C, underlining the importance of occupants' behavior. At last, an analysis on socio-economic impacts was performed, based on the results of a previous study focused on the externality costs due to pollutants emissions. Highlights • Energy advantages achieved through the adoption of low impact energy saving strategies for an independent gas fired boiler were evaluated. • An existing apartment of a modern residential building in Rome was selected and dynamically simulated in TRNSYS. • 36 energy saving scenarios were considered. • Each case was evaluated in terms of energy and economic results. • An analysis on socio-economic impacts was performed, based on the externality costs due to pollutants emissions. [ABSTRACT FROM AUTHOR]

Abstract The paper presents the annual results of monitoring a hybrid heat source consisting of a condensing gas boiler, ground and air heat pump, and solar collectors. A boiler with a nominal heat output of 186 kW works with an 81.1 kW ground-source heat pump, a 27.4 kW air-to-water heat pump and six solar collectors. The hybrid heat source is located in the fire brigade building to provide heat for space heating and ventilation and to supply domestic hot water. The annual monitoring results of the hybrid heat source were analysed in detail. The entire heat plant was equipped with measuring instruments enabling determination of heat output of individual devices, average boiler efficiency in the heating and summer season, the heating seasonal performance factor for ground and air heat pump, gas consumption by the boiler and electricity consumption by individual devices. The heat energy produced by individual devices was determined for a given period. Selected results of the economic analysis are also discussed. The annual costs of purchasing gas and electricity consumed by heat pumps were compared. Boiler efficiency as a function of parameters characteristic for a hybrid heat source was presented. The use of ground and air-source heat pumps and solar collectors reduced the consumption of natural gas during the year by 21,621 m3. As a consequence of the reduced natural gas consumption, the carbon dioxide emissions decreased during the year by 13.32 Mg. Highlights • A system of a gas boiler, solar collectors, ground and air heat pumps was studied. • One year operation of a hybrid heat source system was experimentally assessed. • The efficiency of a boiler was 0.96 in the heating season and only 0.6 in summer. • The share of the ground heat pump in annual heat production was 43% and boiler 51%. • Significant reduction in the gas consumption and CO 2 emission was achieved. [ABSTRACT FROM AUTHOR]

Abstract This paper reviews multifunctional structural materials, particularly continuous fiber polymer-matrix composites. The non-structural functions include sensing, EMI shielding, heating, energy generation, energy storage, actuation and self-healing. For each function, the materials, composite design, functional performance and relevant technological needs are covered. Both unmodified and modified forms of the composite are addressed. Sensing, EMI shielding, heating and actuation are functions that do not require modification, though modifications can be performed. In contrast, energy generation, energy storage and self-healing require modification. For a continuous fiber polymer-matrix composite, the modification commonly involves the incorporation of constituents at the interlaminar interface. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a new approach for the stability analysis of a high-frequency series resonant inverter (HFSRI) in induction heating system. Here the mathematical analysis of HFSRI is described and the stability analysis is obtained by using MATLAB. The analytical method likely gradient method is also used to get stability of high frequency series resonant inverter. So the stability of high-frequency series resonant inverter is obtained and compared between MATLAB simulation output and gradient method output. From this simulation analysis and analytical analysis, the required specifications can be gratified so the appropriate influence of forward path gain and the feedback coefficient of the system are investigated. Hence, the system reliability of proposed topology is checked from the stability analysis of high frequency inverter circuit which is the heart of the induction heating system. More system stability indicates the higher reliability of the system. [ABSTRACT FROM AUTHOR]

Abstract Mine main fan switchover system (MMFSS) is crucial for the mine safe production. MMFSS consists of two main fans (one working and one on standby), and each main fan is equipped with a vertical air door and a horizontal air door. The main purpose of MMFSS is to ensure the stability of the underground airflow quantity and achieve the satisfactory ventilation during the switchover. Moreover, the safe and economic operation of mine production should be ensured. In this paper, the modeling and control problem of MMFSS is considered. First, based on the theory of fluid flow network, the minimal model of MMFSS is built by combining the branch fluid dynamics with the concept of graph theory. Then, a decentralized controller that fully considers the pressure head regulation of two main fans is developed by the Lyapunov stability theory. The controller can ensure that the four air doors can meet with the technological requirements. Finally, the proposed results are conformed using simulations on a semi-physical simulation platform for MMFSS. Highlights • A dynamic model of MMFSS is first developed. • An energy-saving control strategy that prevents the surge of two CMMFs is developed. • A decentralized controller considering the design of the pressure heads is given. [ABSTRACT FROM AUTHOR]

Abstract The majority of Canada's 300 remote communities must rely on petrol by-products for electricity and heating. However, alternative energy sources are gaining in interest. This paper presents a Multi-Criteria Decision Analysis of four alternative energy systems for heating, that is waste gasification and three types of combustion. A systemic approach is considered based on environmental, social and economic aspects. A single-family house in Kuujjuaq is selected for a case study. Results from the preference ranking organization method for enrichment and evaluation (PROMETHEE) show that wood pellets are the most suitable fuel for heating in all scenarios. It is followed by local waste gasification for the base-case and environmental scenarios and by fuel oil for the social and economic scenarios. [ABSTRACT FROM AUTHOR]

Abstract Temporal mismatches between heat provided by a drain water heat recovery system, and heat consumption are, although often disregarded in literature, a crucial factor in assessing the feasibility of the former. Generally, the only available information for residences is the average monthly consumption. The probabilistic method described in this paper uses observations from 113 residences to predict daily and monthly consumption profiles, using monthly consumption as a starting point. These profiles were then used to study the operation of a drain water heat recovery system, but can also be used to assess the operation of other heating methods where the supply is not controlled, such as solar thermal. The operation of the drain water heat recovery systems was predicted based on a monitoring campaign at 3 residences, measuring wastewater temperature and flow at 5-minute intervals, for over a 1-year period. The performance of this system was assessed using the performance data of 26 commercially available heat pumps, with rated power below 7 kW. The method was applied to a theoretical average Irish residence, obtained through a Monte Carlo analysis on just under 700 000 Irish residences. The method highlighted the potential for a reduction in heating related greenhouse gas emissions by 7.6% to 22%. However, this increased heating costs by 120% to 130%. At current traditional heating prices, the DWHR system for a single residence is not financially competitive with traditional systems, due to its significant capital investment. Further research should examine combining waste water streams from different residences to provide a larger flow, and potentially a high recoverable energy volume, thus improving financial viability. Policy makers should also consider incentivizing DWHR to improve its financial competitiveness and help achieve the above GHG emissions savings. [ABSTRACT FROM AUTHOR]

Abstract Beyond the definition and measurement of energy poverty, which have mainly attracted research interest over the last decades, attention has recently begun to turn to a broader notion of energy vulnerability. So far, this has mostly been approached on a theoretical base, suggesting the incorporation of broader socio-economic aspects into the energy poverty framework. However, the quantitative measurement of energy vulnerability is still an unexplored field of research. In this paper, the "Vulnerability Index" is developed, which, based on stochastic analysis, quantifies the vulnerability of a population to the energy poverty ratio, compared to a reference population. Moreover, Sensitivity Analysis quantifies the particular contribution of various parameters to the problem, by determining their weighting factors. As case study, the vulnerability of Greek mountainous regions with respect to the country level was studied. The results showed that households living in mountainous regions are more vulnerable versus those of the whole country, at 89.7%. It was also found that energy policy should focus on raising incomes of mountainous population and, afterwards, on energy saving measures and reduction of heating cost in mountains. The methodology suggested can address social inequalities of vulnerable population groups, in terms of energy poverty. [ABSTRACT FROM AUTHOR]

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]

Highlights • A robust dynamic integral sliding mode control (DISMC) is designed for the approximated model to track the desired heating value. • The unknown states required for the model-based control are reconstructed using a gain-scheduled modified Utkin observer (GSMUO). • To guarantee the stability of the overall system, the boundedness of the internal dynamics is also proved. • To make a fair comparison the performance of the proposed controller is compared with an integral sliding mode and a classical PI controllers. Abstract In this paper, a model-based control and state reconstruction of an underground coal gasification (UCG) process is elaborated. In order to deploy model-based control strategies, a sophisticated model of the UCG process based on partial differential equations is approximated with a nonlinear control-oriented model that adequately preserves the fundamental dynamic characteristics of the process. A robust dynamic integral sliding mode control (DISMC) is designed based on the control-oriented model to track the desired heating value, which is one of the key indicators for evaluating the performance of an UCG process. Unknown states required for the model-based control are reconstructed using a gain-scheduled modified Utkin observer (GSMUO). In order to assess the robustness of the nonlinear control and estimation techniques, the water influx phenomenon is considered as an input disturbance. Moreover, the underlying UCG plant model is subjected to parametric variations as well as measurement noise. In order to guarantee the stability of the overall system, the boundedness of the internal dynamics is also proved. To make a fair comparison, the performance of the proposed controller is compared with an integral sliding mode control (ISMC) and a classical proportional-integral (PI) controller. Simulation results highlight the effectiveness of the proposed control scheme in terms of minimum control energy and improved tracking error. Moreover, the simulation study shows that the combination of DISMC and GSMUO exhibit robustness against an input disturbance, parametric uncertainties and measurement noise. [ABSTRACT FROM AUTHOR]

Highlights • TBR and nuclear heating have been studied for the last version of DCLL BB for DEMO. • Upgrades of this baseline are analyzed under neutronic point of view. • The impact on nuclear performances of different FW designs is addressed. • Two FCI designs with different strategies for their neutronic simulation also affect the TBR result. • The divertor compositions is also demonstrated to have impact on TBR. • NBI integration consequences on TBR and NH are evaluated. Abstract On the way towards a comprehensive design of DEMO, step by step all the systems and components must be introduced as their definition or refinement progresses, in order to demonstrate the viability of a design on larger scale, i.e. leaving fewer margins to undetermined questions. Among the EUROfusion Programme, new aspects have been recently fixed or further developed as the Divertor, the First Wall (FW) and the Flow Channel Inserts (FCI) designs. Furthermore, the integration of Heating and Current Drive (H&CD) systems, as the Neutral Beam Injector (NBI), has started. The introduction or modification of these systems and components could seriously jeopardize the nuclear behaviour of an initially validated Breeding Blanket (BB) DEMO concept, since many neutronics criteria - among others - could be no more fulfilled. Since the design of DEMO is a continuous upgrade under iterative process, as the advances push on, most of the studies have to be repeated to demonstrate that criteria are still respected in a fully integrated design. The consequences of these upgrades over the neutronic responses are addressed in this paper. Among others, the influence on Tritium Breeding Ratio (TBR) of a new design of detached FW protecting BB from high heat fluxes is investigated. The impact of different typologies of FCIs is assessed also according to the degree of detail in the neutronic description. The divertor composition also reveals to have strong impact on responses apparently not related with its design, as the tritium production in the BB. Besides, the integration of NBI minimizing its invasiveness in the BB is verified by neutronic analyses concerning the main BB functions: fuel breeding and heat generation. Accordingly, TBR and Nuclear Heating (NH) are assessed. The study is performed for a Dual Coolant Lead Lithium (DCLL) BB DEMO although can be extrapolated to other BB concepts. [ABSTRACT FROM AUTHOR]

Abstract: The employment of Heating, Ventilation and Air-conditioner (HVAC) technology is viable option for the dynamic thermal comfort in the transitional spaces where connect the interior and exterior space. In this paper, the optimization to thermal environment parameters in the hot summer and warm winter zone is benefit to human comfort, health and energy saving is discussed. According to the dynamic comfort equations and the advantage of artificial immune algorithm in solving combinatorial optimization to engineering problems, the artificial immune algorithm has been applied to the optimization of thermal parameters for the HVAC design within a transitional space. Furthermore, it is pointed out that the proposed method in this paper might be employed in the control of the HVAC conditioning system. [Copyright &y& Elsevier]

Abstract: Optimizing the configuration and operation of a CHP system for a whole year becomes a computationally demanding task when, for example, integer variables are used to model the status (on/off) of different pieces of equipment. The reason is that a discrete optimization problem is fundamentally an enumerative problem, featuring that the number of possible solutions grows exponentially with the number of integer variables. This computational difficulty is known as the curse of dimensionality, and severely limits the chances to use mixed integer programming methods to design CHP systems. To work out this problem, this paper presents a new and unambiguous method to reduce a full year of demand data to a few representative days that adequately preserve significant characteristics such as the peak demands, the demand duration curves, and the temporal inter-relationship between the different types of demands (power, heating, and cooling). Days are selected using a partitional clustering method known as the k-medoids method, and their ability to resemble the original data is tested by means of two quality indexes and a calendar visual inspection. Two case studies are discussed for the completeness of the paper, showing how the method and the quality indexes can be used in practice. [Copyright &y& Elsevier]

Abstract: Evaluating a building’s performance usually requires a high number of sensors especially if individual rooms are analyzed. This paper introduces a simple and scalable model-based virtual sensor that allows analysis of a buildings’ heat consumption down to room level using mainly simple temperature sensors. The approach is demonstrated with different sensor models for a case study of a building that contains a hybrid HVAC system and uses fossil and renewable energy-sources. The results show that, even with simple sensor models, reasonable estimations of rooms’ heat consumption are possible and that rooms with high heat consumption are identified. Further, the paper illustrates how virtual sensors for thermal comfort can support the decision making to identify the best ways to optimize building system efficiency while reducing the building monitoring cost. [Copyright &y& Elsevier]

Abstract: This paper presents a review of studies on natural convection heat transfer in the triangular enclosure namely, in attic-shaped space. Much research activity has been devoted to this topic over the last three decades with a view to providing thermal comfort to the occupants in attic-shaped buildings and to minimising the energy costs associated with heating and air-conditioning. Two basic thermal boundary conditions of attic are considered to represent hot and cold climates or day and night time. This paper also reports on a significant number of studies which have been performed recently on other topics related to the attic space, for example, attics subject to localized heating and attics filled with porous media. [Copyright &y& Elsevier]

Abstract: As a continuation of previous paper on modeling vertical density profile (VDP) formation for wood strand composites, this paper presents typical prediction results from the VDP model and describes the experimental investigations. By taking into account the non-uniform mat structure, the model can predict not only the overall panel VDP but also the localized VDP of a given area within the panel. Thus it links the horizontal density distribution to the vertical density distribution within the panel. The proposed model was validated by comparing its predictions with experimental data. Also the model can predict the effects of some key pressing parameters on VDP formation. Longer press closing times or preheating of the mat is found to make the VDP of the panel more uniform. This study is valuable for improving the fundamental understanding of the relationship between pressing variables and panel properties for process optimization. [Copyright &y& Elsevier]

Abstract: The paper deals with modelling of hygro-thermal performance and thermo-chemical degradation of concrete exposed to high temperature. Several possible simplifications in modelling of heat and mass transport phenomena in heated concrete are considered and their effect on the results of numerical simulations is analyzed. In part I of the companion paper, the physical phenomena, and heat and mass flux and sources in a concrete element were studied, both during slow and fast heating process, to examine the relative importance of different flux components. Then, the mathematical model of concrete at high temperature, developed by Authors in the last 10years, was briefly presented and for the first time all the constitutive relationships of the model are summarized and discussed in detail. Finally, the method of numerical solution of the model equations was thoroughly presented. In this part of the paper a brief literature review of the existing mathematical models of concrete at high temperature and a summary of their main features and physical assumptions is presented first. Then, extensive numerical study is performed with several simplified models, neglecting a chosen physical phenomenon or flux component, to evaluate a difference between the results obtained with the simplified models and with the reference model. The study concerns hygric, thermal and degradation performance of 1-D and 2-D axisymmetric concrete elements during fast and slow heating. The analysis will allow us to indicate which simplifications in modeling of concrete at high temperature are practically and physically possible, without generating excessive differences of the results with respect to the full reference model. [Copyright &y& Elsevier]

Abstract: The performance of different HVAC systems varies when coupled with different buildings. This paper examines the relationship between building heating and cooling load and subsequent energy consumption with different HVAC systems. Two common HVAC systems in use throughout the UK office building stock, variable air volume (VAV) system and fan coil (FC) with dedicated outside air system, have been coupled with a typical narrow plan office building with and without daylight control and for both cellular and open plan. The results presented in this paper clearly indicate that it is not possible to form a reliable judgment about building energy performance based only on building heating and cooling loads. For the two investigated systems, variable air volume system and fan coil with dedicated outside air system, the difference between system demand and building demand varied from over −40% to almost +30% for cooling and between −20% and +15% for heating. If a heat recovery unit is used, the difference in heating performance is even greater, rising to −70%. [Copyright &y& Elsevier]

Abstract: Combined heating and power (CHP) systems may be considered for installation if they produce savings over conventional systems with separate heating and power. For a CHP system with a natural gas engine as the prime mover, the difference between the price of natural gas and the price of purchased electricity, called spark spread, is an indicator as to whether a CHP system might be considered or not. The objective of this paper is to develop a detailed model, based on the spark spread, that compares the electrical energy and heat energy produced by a CHP system against the same amounts of energy produced by a traditional, or separate heating and power (SHP) system that purchases electricity from the grid. An expression for the spark spread based on the cost of the fuel and some of the CHP system efficiencies is presented in this paper as well as an expression for the payback period for a given capital cost and spark spread. The developed expressions allow determining the required spark spread for a CHP system to produce a net operational savings over the SHP in terms of the performance of system components. Results indicate that the spark spread which might indicate favorable payback varies based on the efficiencies of the CHP system components and the desired payback period. In addition, a new expression for calculating the payback period for a CHP system based on the CHP system capital cost per unit of power output and fuel cost is proposed. [Copyright &y& Elsevier]