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In times of great transition of the European construction sector to energy efficient and nearly zero energy buildings (nZEB), a market observation containing qualitative and quantitative indications should help to fill out some of the current gaps concerning the EU 2020 carbon targets. Next to the economic challenges, there are equally important factors that hinder renovating the existing residential building stock and adding newly constructed high performance buildings. Under these circumstances this paper summarises the findings of a cross-comparative study of the societal and technical barriers of nZEB implementation in 7 Southern European countries. The study analyses the present situation and provides an overview on future prospects for nZEB in Southern Europe. The result presents an overview of challenges and provides recommendations based on available empirical evidence to further lower those barriers in the European construction sector. The paper finds that the most Southern European countries are poorly prepared for nZEB implementation and especially to the challenge/opportunity of retrofitting existing buildings. Creating a common approach to further develop nZEB targets, concepts and definitions in synergy with the climatic, societal and technical state of progress in Southern Europe is essential. The paper provides recommendations for actions to shift the identified gaps into opportunities for future development of climate adaptive high performance buildings. [ABSTRACT FROM AUTHOR]

• Long term field evaluation of forecast control of heating. • Easy integration with existing installations in buildings. • Widely applicable measure for energy savings around 10%. • Payback time below one heating season. The priority for reaching carbon neutral buildings by 2050 is to first increase energy efficiency in existing buildings by use of easily and widely applicable measures that are verified based on long-term field research. One such solution is a forecast control of heating systems, which can be quickly and easily integrated to existing weather based controls. However, there are still no long-term field evaluation and detailed analyses of the main features of such a system, which would provide a clear picture about the system's energetical and economical features and thus increase their wide application in existing buildings. This paper provides the data from a long term field evaluation of an innovative forecast control of heating systems (forHEAT), which can be easily installed (in less than 2 h) and integrated with existing installations in millions of existing buildings in Europe and throughout the world. The energy consumption for heating was evaluated in seven residential buildings and three public office buildings before and after the installation and use of the forecast control. The resulting energy savings averaged 13.4% in the residential and 10.7% in the public buildings located in continental European climate, with very cold winters. The payback time averaged a 0.6 heating season and in most case studies does not exceed a single heating season. [ABSTRACT FROM AUTHOR]

This paper presents new metrics to measure the effect of thermal mass on the energy required to heat and cool buildings. Previous studies have been flawed as they have not considered the interaction between intermittent occupancy and thermal mass, which has a significant impact on overall energy use. However, existing parameters do not adequately capture these effects, so the new metrics developed in this paper are used to analyse the impact of thermal mass in hot climates with active cooling, and cold climates with active heating. The results agree with existing literature that high thermal mass structures are likely to be effective in hot climates; however, in cold climates the drawbacks of high thermal mass likely outweigh the advantages, and high thermal mass can cause an increase in energy use. This finding has implications for the design of buildings in cold climates, and contradicts the commonly-held assumption that high thermal mass is correlated with low energy use. The new metrics (transient energy ratio and effective U -value) provide a generalisable method to quantify these effects. They are further used here to analyse the dynamic performance of heavily insulated buildings and show that high thermal mass often leads to higher energy use in cold climates. [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 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]

Highlights • A component-based method of machine learning for performance prediction in engineering. • Components instead of one monolithic model extend reusability and generalization. • Flexible design support by machine learning for early design phases. • Internal parameters between components allow insights in the “black box” of machine learning. • Good prediction accuracies (error < 3.9%) for test cases different from the training model. Abstract Machine learning is increasingly being used to predict building performance. It replaces building performance simulation, and is used for data analytics. Major benefits include the simplification of prediction models and a dramatic reduction in computation times. However, the monolithic whole-building models suffer from a limited transfer of models and their data to other contexts. This imposes a vital limitation on the application of machine learning in building design. In this paper, we present a component-based approach that develops machine learning models not only for a parameterized whole building design, but for parameterized components of the design as well. Two decomposition levels, namely construction level components (wall, windows, floors, roof, etc.), and zone-level components, are examined. Results in test cases show that, depending on how far the cases deviate from the training case and its data, high prediction quality may be achieved with errors as low as 3.7% for cooling and 3.9% for heating. [ABSTRACT FROM AUTHOR]

Housing Stock Energy Models (HSEMs) play a determinant role in the study of strategies to decarbonise the UK housing stock. Over the past three decades, a range of national HSEMs have been developed and deployed to estimate the energy demand of the 27 million dwellings that comprise the UK housing stock. However, despite ongoing improvements in the fidelity of both modelling strategies and calibration data, their longevity, usability and reliability have been compromised by a lack of modularity and openness in the underlying algorithms and calibration data sets. To address these shortfalls, a new open and modular platform for the dynamic simulation of national (in the first instance, the UK) housing stocks has been developed—the Energy Hub (EnHub) . This paper describes EnHub’s architecture, its underlying rationale, the datasets it employs, its current scope, examples of its application, and plans for its further development. In this we pay particular attention to the systematic identification of housing archetypes and their corresponding attributes to represent the stock. The scenarios we analyse in our initial applications of EnHub, based on these archetypes, focus on improvements to housing fabric, the efficiency of lights and appliances and of the related behavioural practices of their users. In this we consider a perfect uptake scenario and a conditional (partial) uptake scenario. Results from the disaggregation of energy use throughout the stock for the baseline case and for our scenarios indicate that improvements to solid wall and loft thermal performance are particularly effective, as are reductions in infiltration. Improvements in lights and appliances and reductions in the intensity of their use are largely counteracted by increases in heating demand. Housing archetypes that offer the greatest potential savings are apartments and detached dwellings, owing to their relatively high surface area to volume ratio; in particular for pre-1919 and inter-war epochs. [ABSTRACT FROM AUTHOR]

District heating system brings with it the problem of achieving a fair billing service for heating of apartment buildings in the case of uneven temperature in them. The problem is most pronounced when the individual apartments are completely excluded from the heating system of the building. The model of an existing building with 24 apartments was simulated in the software EnergyPlus, for different characteristics of the thermal envelope and different conditions of use, when the apartment with the lowest energy consumption is excluded from the heating system. It was simulated the exclusion of this apartment in which people are present and the lights and electrical appliances are turned on and in which there is no presence of people and electricity consumption (the apartment is empty). As a measure of energy flow between unheated and adjacent apartments, the parameter “stolen” energy is defined. The results of the conducted simulations show that the stolen energy is reduced by the exterior and interior insulation of the building. In this paper, data on energy flow when there is interior insulation in apartments, in particular according to the current regulations in Serbia, are especially analyzed. The results show that, depending on the case and scenario, the stolen energy ranges from 27.23 to 7.97 kWh/m 2 . The insulation of interior walls of the building can significantly mitigate the problem of energy flow due to temperature differences between apartments. [ABSTRACT FROM AUTHOR]

During the master planning of neighbourhoods, design decisions related to the urban layout and typology affect the building form and availability of solar radiation considerably. The influence of those decisions on the energy demand for heating is often neglected however because appropriate energy simulation tools are lacking. This paper proposes a simple and accurate design tool to assess the solar gains and heating energy demand in buildings during the master planning phase of neighbourhoods. Detailed information on building geometry, constituting building elements and solar obstructions, is extracted from a 3D neighbourhood model using a plugin implemented in the modelling software SketchUp. This information is used to assess the heating energy demand of the buildings in the neighbourhood based on the dynamic Equivalent Heating Degree Day (dEHDD) method. Furthermore, the associated financial and environmental impacts are calculated based on an integrated life cycle approach, combining Life Cycle Costing (LCC) and Environmental Life Cycle Assessment (E-LCA) respectively. The design tool proposed is implemented for the Belgian context and used to analyse a number of schematic residential neighbourhood models with diverse built densities. The analysis reveals substantial differences in heating energy demand, life cycle financial and environmental costs. Neighbourhoods with a high built density and compact building types have a lower heating energy demand with potential reductions of up to 40% compared to neighbourhoods with a low built density and detached building types. [ABSTRACT FROM AUTHOR]

Heat loss from rotary kilns accounts for certain amounts of the total energy consumption in chemical and metallurgical industries. To reduce the heat loss, a parallel and a series-parallel heat recovery systems with nine heat recovery exchangers are proposed to preheat the cold water in this paper. Experimental measurements are carried out to determine the heat transfer coefficient equations of each heat recovery exchanger. Then, the heat recovery systems are analyzed to deduce the mathematic relation between the design parameters and the system requirements, i.e. the temperatures and heat transfer rates of the nine heat recovery exchangers. The total heat transfer area, the total power consumption and the entropy generation due to heat transfer and fluid flow are set as the objective functions in four multi-objective optimization (MOO) cases. With the aid of the genetic algorithm in the Matlab 2015, the optimized operational and structural parameters are obtained. Finally, the MOO results are compared with that of the single objective optimization (SOO) method and the original values. The optimization results show that the MOO method are more suitable for the operational parameters design of the heat recovery systems compared with the SOO method. The required total heat transfer area and the total power consumption are decreased by at least 12.1% and 13.7%, respectively. Besides, as the entropy generation due to heat transfer and fluid flow decrease in the MOO cases, the corresponding heat transfer area and power consumption of the heat recovery system decrease, respectively. [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]

Although electric power networks and district heating networks are physically coupled, they are not operated in a coordinated manner. With increasing penetration of renewable energy sources, a coordinated market-based operation of the two networks can yield significant advantages, as reduced need for grid reinforcements, by optimizing the power flows in the coupled systems. Transactive control has been developed as a promising approach based on market and control mechanisms to coordinate supply and demand in energy systems, which when applied to power systems is being referred to as transactive energy. However, this approach has not been fully investigated in the context of market-based operation of coupled electric power and district heating networks. Therefore, this paper proposes a transactive control approach to coordinate flexible producers and consumers while taking into account the operational aspects of both networks, for the benefit of all participants and considering their privacy. A nonlinear model predictive control approach is applied in this work to maximize the social welfare of both networks, taking into account system operational limits, while reducing losses and considering system dynamics and forecasted power supply and demand of inflexible producers and consumers. A subtle approximation of the operational optimization problem is used to enable the practical application of the proposed approach in real time. The presented technique is implemented, tested, and demonstrated in a realistic test system, illustrating its benefits. • Transactive control design for coupled electric power and district heating networks. • Development and application of an accurate and computationally efficient system model. • Technical and economic optimal system operation considering participant privacy. [ABSTRACT FROM AUTHOR]

Abstract: Microturbines offer new perspectives in small-scale heat and power production however their profitability depends strongly on the yearly amount of running hours. The non-continuous heat demand often leads to a reduction in running hours. This paper proposes an alternative by recuperating the lost thermal power through the injection of heated water in the micro Gas Turbine (mGT). Water injection is considered a successful way to increase power and efficiency in industrial gas turbines and similar effects are expected for microturbines. This paper reports on a series of simulations of water injection performed on a Turbec T100 mGT. The goal of this study was to investigate the potential of water injection in the mGT cycle using an adiabatic black box method in the Aspen® process simulation tool. Past experiments with steam injection on the T100 demonstrated the potential of introducing steam/water in the microturbine cycle. Calculations revealed that the key parameters for maximum heat recuperation are stack and pinch temperature. Simulations showed that most of the exhaust heat can be recovered through injection of heated water after the compressor, resulting in an 18% decrease in fuel consumption and an absolute increase in electrical efficiency of 7%. [Copyright &y& Elsevier]

[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]

In a central heating, ventilation, and air conditioning (HVAC) system, the set-points for several local control loops have a significant influence on the overall energy performance of the system. Real-time optimization (RtOpt) of those set-points has therefore been widely studied. However, due to the nonlinear dynamics of the HVAC system as well as the constraints associated with the system operation, real-time optimization always suffers from a heavy on-line computational load when those set-points are optimized simultaneously. To overcome this problem, multiplexed real-time optimization (MRtOpt) has been developed, which optimizes only one set-point at a time but with a faster optimization frequency. Because frequently resetting the set-points introduces artificial disturbances into the local control loops and may deteriorate the system stability, this paper presents a study to enhance the system stability of the multiplexed real-time optimization by integrating a degree of freedom (DOF) based set-point reset to renew the set-points instead of the conventional step-change set-point reset. The control performance of the integrated strategy was investigated using case studies. The results showed that around 10% of the energy saving was achieved by the proposed method compared with a method without real-time optimization. When compared with the conventional real-time optimization method, the proposed method resulted in around 70% computational load reduction, and over 26% reduction in the tracking errors of the local control loops. [ABSTRACT FROM AUTHOR]

Application of Thermoeconomics in the diagnosis of building energy supply systems allows the localization and quantification of an abnormal operation, which can cause significant increase in energy consumption to obtain the same product. To do that, a comparison between the real operation of the energy system and the reference operation must be done. In this paper a DHW and heating plant based on a condensing boiler has been analysed. Diagnosis is applied through a mono-failure case using a methodology based on the fuel impact formula and the malfunction and dysfunction analysis. An innovative methodology will be presented in order to filter the induced effects that take place in a dynamic situation due to the control system. Although the real aim of diagnosis is to solve the inverse problem, in this work we have faced a direct problem, in which a parameter of one component of the plant has been modified and its effect over the other components and the whole plant is evaluated. The major outcome is that by the application of this methodology the effects produced by the faulty component can easily be quantified, both in performance and economic terms. Those effects are due to the component malfunction as well as the induced malfunctions and dysfunctions generated in the other components of the facility. [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]

• A hydrogen-based MEMG in the electricity market is exploited. • A multiple time-scale energy management solution for MEMG is developed. • Electricity and hydrogen trading among subsystems are considered. • Daily operational cost of the hydrogen-based MEMG is minimized. With the technological advances in energy conversion and utilization of multiple forms of energy sources, hydrogen energy has attracted increasing attention. The hydrogen energy can be used to directly supply the hydrogen demand and generate both electricity and heat through fuel cell-based combined heat and power (FC-CHP) unit. This paper proposed a multiple time-scale energy management solution for a hydrogen-based multi-energy microgrid (MEMG) to supply electricity, hydrogen and heating loads aiming to minimize the MEMG operational cost with consideration of renewable energy generation and demand uncertainties. The proposed solution consists of day-ahead energy scheduling and model predictive control (MPC) based real-time energy dispatch in the presence of the electricity market. In the hydrogen-based MEMG, the electricity and hydrogen can be dispatched and utilized across multiple interconnected subsystems to improve the overall system energy utilization efficiency. The proposed solution is extensively assessed through simulation experiments compared with a benchmark solution. The numerical results confirm that the proposed solution outperforms the benchmark solution with the mean daily actual operational costs reduced by 37.08%. [ABSTRACT FROM AUTHOR]

In electric buses, the heating, ventilation and air conditioning (HVAC) system is responsible for up to 50% of the energy consumption, thereby significantly affecting the efficiency. It is therefore necessary to identify improved thermal settings for the bus cabin to minimize the energy consumption, while guaranteeing good thermal comfort. To achieve this goal, this paper presents the results of climatic measurements in an electric bus in Berlin, Germany. These measurements were performed for outer temperatures between 5.3 °C and 7.8 °C and four cabin temperature settings. During the measurements, several climatic parameters and the energy consumption were measured, whereas the thermal comfort (TC) was evaluated via 71 passengers' surveys. The results show that the climatic conditions in the bus vary greatly depending on the position (up to 3 K difference in mean air temperature) and height (up to 8 K/m temperature-to-height ratio). Additionally, the surveys show that the mean value of the thermal comfort parameter TC is minimized to a value of 0.15 (corresponding to "comfortable" thermal perception) for a set temperature of 21 °C, whereas the thermal conditions are perceived as acceptable even with heating off. [ABSTRACT FROM AUTHOR]

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: 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: 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: Building energy regulations, also referred to as building energy codes, emerged in the 1970s as an essential tool for improving energy efficiency and minimising energy consumption in buildings. Basically they aim at setting minimum energy efficiency requirements to achieve energy efficient design in new buildings. This paper analyses the development of building energy codes concerning Heating, Ventilation and Air-Conditioning (HVAC) energy efficiency, along with their scope and compliance paths. The paper focuses on the synthesis of energy efficiency requirements on HVAC systems of non-residential buildings in different regulations. Critical issues for the development of prescriptive and performance regulatory paths for this type of systems in non-residential buildings are discussed in order to improve the understanding of HVAC energy efficiency topics and to provide policy makers with a menu of options to strengthen the HVAC section of building energy codes. [ABSTRACT FROM AUTHOR]

Abstract: Optimization of combined cooling, heating, and power (CCHP) systems operation commonly focuses only on energy cost. Different algorithms have been developed to attain optimal utilization of CCHP units by minimizing the energy cost in CCHP systems operation. However, other outcomes resulting from CCHP operation such as primary energy consumption and emission of pollutants should also be considered during CCHP systems evaluation as one would expect these outcomes can be subject to regulation. This paper presents an optimization of the operation of CCHP systems for different climate conditions based on operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDE) using an optimal energy dispatch algorithm. The results for the selected cities demonstrate that in general there is not a common trend among the three optimization modes presented in this paper since optimizing one parameter may reduce or increase the other two parameters. The only cities that show reduction of PEC while also reducing the CDE are Columbus, MS; Minneapolis, MN; and Miami, FL. For these cities the operational cost always increases when compared to the reference case consisting of using a vapor/compression cycle for cooling and natural gas for heating. On the other hand, for San Francisco and Boston, CCHP systems increase the CDE. In general, if CCHP systems increase the cost of operation, as long as energy savings and reduction of emissions are guaranteed, the implementation of these systems should be considered. [Copyright &y& Elsevier]

Abstract: Thermally activated building systems (TABS) integrate the building structure as energy storage, and have proofed to be energy efficient and economic viable for the heating and cooling of buildings. Although TABS are increasingly used, in many cases control has remained an issue to be improved. In this paper, a method is outlined allowing for automated control of TABS in intermittent operation with pulse width modulation (PWM). This method represents one part of a TABS control solution with automatic switching between cooling and heating modes for variable comfort criteria which was published before. A first pulse width modulation control solution is derived based on a simple 1st order model of TABS. Then a second, even simpler solution is given that significantly reduces the tuning effort. Finally, the paper outlines a pulse width modulation control procedure and gives two application examples of the PWM control carried out in a laboratory test room. [Copyright &y& Elsevier]

This paper aims to develop an optimal real-life energy-efficient design for a production plant within the concept of the circular economy. The problem is to install a Heat Recovery System (HRS) that utilizes the hot oil used by the compressors to heat the water for the central heating system. To achieve the desired level of energy efficiency this design problem must be formulated from both the optimization and sustainability points of view. Additionally, this design problem must also consider the investment cost. In line with this purpose, this paper formulates this design problem as an optimization problem employing a mathematical programming approach as a single objective, and as a multi-objective optimization problem through a goal programming approach. Besides, this paper uses the return on investment as a key performance indicator, since it deals with a real-life design problem with an investment cost. The related design problem is solved with the single objective and multi-objective versions of the developed mathematical programming model via a commercial solver to identify different design alternatives and hence giving the decision-maker to make a selection option. Finally, the capability of the developed mathematical programming model is tested on a set of randomly generated problems. The obtained results indicate that the developed mathematical programming model is a successful decision support system since its single and multi-objective versions are capable of identifying energy-efficient production designs within the context of the real-life problem on hand and the circular economy. • A real-life energy-efficient design problem for a production plant is undertaken. • A heat recovery system is proposed within the concept of a circular economy. • The problem is modelled from both the optimization and sustainability aspects. • The problem is formulated as multi-objective models using goal programming. • The models are solved to minimize investment costs and maximize energy efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a practical method to optimize in-building section of centralized Heating, Ventilation and Air-conditioning (HVAC) systems which consist of indoor air loops and chilled water loops. First, through component characteristic analysis, mathematical models associated with cooling loads and energy consumption for heat exchangers and energy consuming devices are established. By considering variation of cooling load of each end user, adaptive neuro-fuzzy inference system (ANFIS) is employed to model duct and pipe networks and obtain optimal differential pressure (DP) set points based on limited sensor information. A mix-integer nonlinear constraint optimization of system energy is formulated and solved by a modified genetic algorithm. The main feature of our paper is a systematic approach in optimizing the overall system energy consumption rather than that of individual component. A simulation study for a typical centralized HVAC system is provided to compare the proposed optimization method with traditional ones. The results show that the proposed method indeed improves the system performance significantly. [Copyright &y& Elsevier]

The paper briefly describes energy-efficiency standards that have been issued for residential buildings in Northern and Central China as well as energy-efficiency inspection standards and specifications for renovation of existing residential heating systems in Northern China, and development of energy-efficiency standards for Southern China. The paper also describes barriers to improving the energy efficiency of residential buildings in China and strategies for overcoming these barriers, including reform of the method of payment for heating in Northern China. Finally, future prospects for further developing energy-efficiency standards for residential buildings in China are addressed. [Copyright &y& Elsevier]

• 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]

[Display omitted] • A hierarchical approach for automatic layout of an underfloor heating system is proposed. • The routing problem is formulated as a shortest path problem in a proper routing graph. • An order relation is defined to separate the intersecting paths. • A depth-first layout algorithm based on recursion is developed to solve the coverage path planning problem. The layout of an underfloor heating system determines its heating performance. Conventionally, the design is completed by qualified experts using professional software, but this method is inefficient and heavily relies on the experts' previous experience. This paper proposes a hierarchical approach for the automatic design of underfloor heating systems aimed at residential buildings, and the underfloor heating layout problem is decomposed into a routing problem and coverage path planning problem. First, the routing problem is formulated as a shortest path problem in an appropriate routing graph and solved to provide the routing of pipes for further coverage. Subsequently, a depth-first layout algorithm is developed to recursively simplify the coverage path planning problem to obtain the basic rectangle layout, achieving uniform coverage of the given layout zone. Simulation results on two houses show that, unlike one popular commercial platform, the proposed approach generated feasible solutions in all 13 test instances. The new method improved the minimum temperature, average temperature, average percentage of nodes greater than 30 °C, and total energy efficiency by 3.18 °C, 0.79 °C, 3.23%, and 4.19%, respectively, with a lower variance on average. These improvements lead to a higher coverage rate, more even thermal distribution, and stronger robustness under flexible parameter selection. [ABSTRACT FROM AUTHOR]

Municipal heating by coal contributes considerably to the haze pollution in Chinese cities during cold period, e.g., Beijing 53%. It is widely considered that, as a supplement of natural gas, the use of coal-based synthetic natural gas (SNG) to replace coal for municipal heating is conductive to mitigate the haze pollution in metropolitan areas. Would it still be a good alternative if the whole life cycle of SNG were taken into consideration? In this study, SNG as an alternative for municipal heating is analyzed in comparison with coal. To target cleaner production, life cycle assessment methodology is used to analyze SNG contribution to haze pollutants and greenhouse gases (GHGs) emissions, as well as energy consumption. Compared to coal heating route, SNG heating route could reduce 44% of the haze pollutants emissions from life cycle perspective and up to 98% of the emissions in urban area. Thus, if municipal heating were entirely supplied by natural gas and SNG, there would be 52% less haze pollutants emissions in winter of Beijing. However, this “good” performance is at the cost of transferring haze pollutants emissions from urban areas to SNG-producing regions. It is also at the cost of consuming 90% more coal and emitting 65% more GHGs than the coal heating route from life cycle point of view. To tackle the problems of haze pollutants transfer and the increase of GHGs emissions, the paper suggests implementing ecological compensation and carbon tax policies in the coal-based SNG industry. [ABSTRACT FROM AUTHOR]

This paper presents a thermal analysis of a semi-active battery/supercapacitor (SC) hybrid energy storage system (HESS), which is used in electric vehicles (EVs), at subzero temperatures. In subzero temperature environments, EVs suffer a dramatic driving range loss due to the energy and power capability reduction of LiFePO 4 batteries, as well as severe battery degradation due to Li plating. This will increase the system operation cost because the battery pack needs to be changed frequently. Based on a novel degradation model of LiFePO 4 batteries, which is validated over a wide temperature range, a near-optimal energy management strategy of the HESS for on-line use is proposed using the dynamic programming (DP) approach, which minimizes the operation cost (the electricity and the battery fade costs) over a typical China Bus Drive Cycle (CBDC). The convective heating method is integrated into the DP process. Finally, the required heating of the HESS at subzero temperatures over multi-CBDC is analyzed by evaluating the system operation cost. Simulation results show that the heating process becomes increasingly necessary with increased driving range, battery price, and heating efficiency, as well as decreasing environment temperature. [ABSTRACT FROM AUTHOR]

This paper reports the results of three innovative laboratory tests implemented during winter 2013 in the framework of the Climate for Culture European Project (2009–2014). Thermal analysis was used to assess the heating efficiency of some heaters with different power consumption, geometric shape and dimensions. Experimental laboratory results were obtained under natural indoor environmental conditions and the outcomes were applied to a real case study of two churches on the Italian Alps during the Friendly Heating project. Results provide useful information to help final users and/or conservators to exploit at the best the heating efficiency of some heaters on the basis of the geometric characteristics of the elements and represent helpful advices for their installation, considering both the optimal position for the maximum comfort performance and the need for not exceeding specific risk thresholds for artwork preservation. [ABSTRACT FROM AUTHOR]

This paper discussed the influence of apartment location on household space heating energy demand per floor area in multi-apartment buildings. According to the actual data, apartment location has a significant impact on space heating consumption per floor area in multi-apartment buildings. Based on average data of each location, a corner unit on the top floor has a space heating consumption per floor area 26.1% higher than a center unit on the middle floor. For multi-apartment buildings, a correction should be made to reflect the effect of apartment location when billing is calculated from space heating consumption instead of floor area. Location correction factors (LCFs) of seven typical cities based on building type and building age were analyzed by calibrated simulation method. The study finds that LCFs for older buildings are smaller than those of younger buildings, varying from 0.8% to 15.3% for seven typical cities. As for different regions, the greater the heating degree day is, the larger the location correction factor (LCF) is, with the deviation among 5.7–14.4%. LCFs can provide a billing-tool to make a fair allocation of heating costs, which may promote the reform of heat metering and billing in China. [ABSTRACT FROM AUTHOR]

Although China's heat metering technology has developed rapidly in recent years, the improvement demonstrates an unbalance in different provinces. It is of great significance to outlook application and sustainability of heat metering technology in various regions technically. Taking the sustainability of heat metering technology as research object, the author establishes a sustainable evaluation model in this paper. Factors in the evaluation model are assigned through a main questionnaire and actual application of typical projects. A pecking-order contrast method is adopted to determine weights of factors in the evaluation model, correspondingly sustainable development of heat metering in various locations is assessed. Sustainability scores in three regions (Northeast, Northwest and North China) are obtained via evaluation model. The model owns high accuracy compared with results of heat metering work assessment by the Ministry of Housing and Urban-Rural Development (MOHURD). The heat metering in the three regions score 60, 62 and 75, respectively, implying that the sustainability in the northeast and northwest is unsatisfactory but in north is somehow better. It is suggested that envelope heat insulation should be increased in the northeast region, while policy support and heat metering technology ought to be enhanced in the northwest. [ABSTRACT FROM AUTHOR]

• Freely available online overview of district heating efficiency indicators. • Hourly district heating energy use data from approx. 43 000 buildings. • Building stock segmented into building typologies for analysis of: • -1) Heating energy use intensity, 2) load variation and 3) cooling efficiency This paper provides a state-of-the-art and freely available online overview of the district heating (DH) efficiency of Danish building typologies. The overview is based on DH consumption data from 42 969 buildings constructed up until 2017 that in combination with data from the Danish Building and Dwelling Register constitutes a dataset with a previously unseen level of detail, confidence, sample size, and research opportunities. The paper also presents an initial analysis of the dataset in terms of three heating efficiency indicators, namely 1) Annual heating energy use intensity, 2) Daily heat load variation, and 3) Cooling efficiency. The overall finding was that building typologies perform significantly different from one another concerning indicators 1 and 2, but not for indicator 3. It is therefore not possible to declare one building typology more efficient than the other as this depends on the building construction year and the considered efficiency indicator. The data indicate that further energy-efficiency improvements of the existing building stock are essential to the realization of 4th Generation District Heating technologies in Denmark and that these improvements most likely will lead to increased heat load variations that need to be addressed, for instance by enabling a larger degree of demand-side flexibility in the existing district heating systems. The large temporal variation of the buildings' cooling efficiency indicates that there is a potential for rethinking e.g. domestic hot water production in the summer or introduce differentiated billing based on the daily, weekly, or maybe seasonal cooling performance. The presented dataset can be subject to several future investigations which are also discussed in the paper. [ABSTRACT FROM AUTHOR]

The energy industry is undergoing a tremendous transformation from a centralized paradigm to a decentralized one with the employment of various distributed energy technologies and information technologies. Different from the traditional urban central heating system, the district heating system (DHS) with combined energy supply by multi-energy and multi-level energy stations is considered to be promising and can improve the efficiency and flexibility of the energy system. However, its complex system structure and multiple stakeholders bring new challenges to the operation optimization. Therefore, in the face of the DHS, two optimization models are applied in this study: 1) Independent Optimization Model (IOM): the operation strategies of each energy station are optimized independently, and each station then submits its own energy demand to the upper-level energy station; 2) Collaboration Optimization Model (COM): a model established for all energy stations for global optimization. A small number of existing papers on the operation optimization of such DHS have ignored the contradiction between social benefits and operators' profits, and do not study the gap between the two models. Therefore, this paper takes COM as the benchmark, quantitatively evaluating the potential of IOM for improving the overall energy efficiency under the interest game, and grasps the key reasons that restrict its energy saving potential, aiming to improve its comprehensive benefits. An actual DHS in China was used as a case study to explore the above problems. The results show that, although COM is more energy-saving, it loses 18.3% of the profits of energy integrators, and increases the profits of energy suppliers by 13.8%. Compared with COM, the primary energy consumption of IOM increases by 19.1%. For the results, this paper finally discusses whether it is possible to further improve the energy efficiency of IOM by adjusting the heat price without impairing the profits of the operators. The results indicate that the system's primary energy consumption reduces by 5.2% without impairing the profits of each operator. • The operation strategy of the multi-energy multi-level district heating system is optimized. • The contradiction between social benefits and operator profits is considered. • Independent optimization model and collaborative optimization model are established and quantitatively compared. • An actual case study is analyzed to explore why the energy saving potential of independent optimization is restricted. • The further improvement of independent optimization is discussed. [ABSTRACT FROM AUTHOR]

• A new enclosed melting system was built for deicing the bottom of a train. • A new method was used for simulating gravity shedding melting in complex models. • The effect of supply air properties on system performance was studied. In winter, a large amount of icing and snowing occurs in outdoor equipment and systems, which adversely affects their lifespan. The melting process is divided into two parts: convection melting and gravity shedding melting. This paper is based on an experiment with a real high-speed train unit, and it establishes a three-dimensional computational fluid dynamics model of the bogie area to validate the mathematical model of the winter ice melting experiment. A numerical simulation was used to calculate the airflow in the baffle-enclosed space and to predict the effects of interactions between air and the ice body on heat transfer and phase change. The influence of air velocity and temperature on the heat transfer was analyzed. The computational simulation effectively quantifies the amount of heat transfer and energy consumption under different conditions. This paper also presents a research method for the simulation of gravity shedding in complex models. These models provide information for the construction of similar ice melting models. This paper has suggested that for thin ice bodies, convection melting was the dominant strategy. For thick ice bodies, however, gravity shedding melting became dominant. The study also confirmed that enclosed hot-air ice-melting systems gave a better energy performance than unenclosed systems. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the methodology for the risk-based dimensioning of domestic hot water (DHW) and heating demands. It is demonstrated that they are stochastic variables. DHW demands are specified on the basis of hot water consumption statistics in Hungary. The standard values of heat demands for heating are based on the duration curve of external air temperatures. This study discusses daily mean temperature distribution in the heating season – between 15 October and 15 April in Hungary – and the description of its duration curve sorted by time. The authors verify the assumption that the duration curve can be described by normal distribution mathematically with high precision. Thereby they somewhat put an end to the process of mathematical experimentation on what function should be used to describe the frequency and duration curve of external daily mean temperatures in the heating season. [Copyright &y& Elsevier]

Abstract: Heating Ventilation and Air Conditioning (HVAC) system energy consumption on average accounts for 40% of an industrial sites total energy consumption. Studies have indicated that 20 – 30% energy savings are achievable by recommissioning Air Handling Units (AHUs) in HVAC systems to rectify faulty operation. Studies have also demonstrated that on-going commissioning of building systems for optimum efficiency can yield savings of an average of over 20% of total energy cost. Automated Fault Detection and Diagnosis (AFDD) is a process concerned with automating the detection of faults and their causes in physical systems. AFDD can be used to assist the commissioning process at multiple stages. This paper outlines the development of an AFDD tool for AHUs using expert rules. It outlines the results of the alpha testing phase of the tool on 18 AHUs across four commercial & industrial sites with over €104,000 annual energy savings detected by the AFDD tool. [Copyright &y& Elsevier]

Abstract: This paper studied the annual thermal performance of a photovoltaic wall (PV wall) mounted on a multi-layer façade. Based on some developed unsteady-state heat transfer models for a PV wall and a normal wall, the annual thermal performance of two types of walls was simulated. Compared with a normal wall, the south-facing PV wall could reduce heat gain through the envelope by 51% in summer under Hong Kong weather conditions. The impact of the PV wall on the envelope’s heat gain and heat loss in winter was investigated for the first time, and the results indicated that the PV wall could not only significantly reduce the heat gain through the envelope in daytime, but also reduce the heat loss at nighttime. The heat gain and heat loss through the PV wall in winter were reduced by 69% and 32% respectively compared with a normal wall. Totally, an annual thermal energy consumption reduction of 52.1kWh was achieved by replacing each square meter of a south-facing normal wall by a PV wall, which is equivalent to a saving of 18.6kWh of electric energy for the air conditioning system in a building. The impact of the thickness of an air duct on the thermal performance of the PV wall was also discussed. [Copyright &y& Elsevier]

Abstract: Full chain energy performance is applied to a hybrid combined cooling, heating and power (CCHP) system running with methanol and solar energy. Results show that the overall energy efficiencies of six different cases range from 40% to 50% in summer condition, and 38% to 47% in winter condition. Combined with the traditional methanol production process, the CCHP systems are not energy efficient compared to the traditional energy supply systems from a full chain viewpoint no matter whether the solar energy is utilized. While combined with a polygeneration (PG) or polygeneration with CO2 capture (PG+CC) process, the CCHP system could achieve obvious improvements in overall energy efficiency due to the benefits from cogeneration and solar energy utilization, and thus could yield a high fossil energy saving ratio in comparison with the traditional energy supply system. The findings presented in this paper indicate that the complementation utilization of solar energy and fossil fuels through thermochemistry reactions is energy efficient and could be one of the potential options to utilize solar energy. [Copyright &y& Elsevier]

District heating is expected to play an essential role in the cost-effective decarbonisation strategy of many countries. Resource-optimised management of district heating networks depends on a wide range of factors, including demand forecasting, operational flexibility, and increasingly volatile market conditions. However, traditional operations often still rely on static models and rather simple heuristics, while holistic optimisation requires dynamic cross-domain interoperability to allow the consideration of all these factors. This paper demonstrates a proof-of-concept for a knowledge graph based optimisation problem to minimise total heat generation cost for a district heating provider. The optimisation follows a hierarchical approach based on a merit-order principle and is embedded in a model predictive control framework to allow the system to incorporate most recent information and react to disturbances promptly. A detailed sensitivity study is conducted to identify key model parameters and assess the impact of anticipated changes in regulation and market conditions. Simulation-based optimisation is used to determine the short-term heat generation mix based on data-driven gas consumption models and day-ahead forecasts for the network's energy demand and grid temperatures. Seasonal autoregressive integrated moving average models with exogenous predictor variables are found to be sufficiently accurate and precise. The effectiveness of the approach is demonstrated for a case study of an existing heating network of a midsize town in Germany, where a reduction of approximately 20% and 40% compared to baseline operational data is obtained for operating cost and CO 2 emissions, respectively. [Display omitted] • Developed heat generation optimisation framework for district heating providers. • Identified key cost drivers and market dynamics using a detailed sensitivity analysis. • Developed high accuracy time series forecasting models for key input variables. • Assessed optimisation effectivity using a German municipal utility case study. • Improvement potential for operational cost and CO 2 emissions both exceed 20%. [ABSTRACT FROM AUTHOR]

[Display omitted] The rapid development of urbanization has created high demand for central heating systems. This trend has led to an increase in energy consumption for central heating, which has made China's energy-saving transformation extremely difficult. However, the channel by which urbanization impacts and the future trends of energy consumption for central heating are still unclear. Therefore, this study employs the Logarithmic Mean Divisia Index (LMDI) method to decompose the effect of urbanization on changes in energy consumption for central heating during 2001–2019 in China. We investigate the contribution of urbanization from demographic, economic and spatial perspectives. Additionally, a scenario analysis is used to explore trends in energy consumption for central heating in different projected urbanization scenarios. The results show that urbanization has a positive impact on energy consumption for central heating, particularly in underdeveloped regions. Demographic urbanization has the strongest positive effect on energy consumption for central heating, followed by spatial urbanization and then economic urbanization. Compared with the expansion of area and economic development, population agglomeration will bring more energy consumption for central heating. The forecasting results indicate that energy consumption for central heating will reach 176–189 Mtce in 2030, which is approximately 1.4 times the current level. This work quantifies the energy consumption for central heating in the future under urbanization. The policy recommendations given at the end of the paper will provide a reference for the formulation of energy consumption for central heating. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a model to simulate the electricity demand of a single household consisting of multiple individuals. The total consumption is divided into four main categories, namely cold appliances, heating, ventilation, and air conditioning, lighting, and energy consumed by household members’ activities. The first three components are modeled using engineering physically-based models, while the activity patterns of individuals are modeled using a heterogeneous Markov chain. Using data collected by the U.S. Bureau of Labor Statistics, a case study for an average American household is developed. The data are used to conduct an in-sample validation of the modeled activities and a rigorous statistical validation of the predicted electricity demand against metered data is provided. The results show highly realistic patterns that capture annual and diurnal variations, load fluctuations, and diversity between household configuration, location, and size. [Copyright &y& Elsevier]

Abstract: This paper presents the heat transfer characteristics of CNT based nanofluids in a tubular heat exchanger of various lengths for cooling/heating applications. The nanofluid is prepared by dispersing multi-wall carbon nanotubes (MWCNT) in water–ethylene glycol mixture (70:30 by volume), and the value of the Prandtl number increases by 115.8% at 0°C, and 180.2% at 40°C for the nanofluids with 0.45vol.% MWCNT, compared to the base fluid. In contrast to the conventional heat transfer concept, the value of the Nusselt number for the nanofluids increases with decrease in the Reynolds number as the MWCNT concentration increases. The results showed the significant enhancement in the convective heat transfer coefficient in the entrance region. The possible reason for the abnormal enhancement in the heat transfer coefficient for the shorter length of the test section is due to the migration of the carbon nanotubes. This migration of carbon nanotubes does not allow the thermal boundary layer to develop at the faster rate. [Copyright &y& Elsevier]

Abstract: This paper presents a novel energy storage system which stores excessive energy in the form of compressed air and thermal heat. It is different from the conventional compressed air energy storage (CAES) technology in that the new system allows trigeneration of electrical, heating and cooling power in energy releasing process. Uniquely, the cooling power from this system is generated by direct expansion of compressed air instead of the use of absorption chilling technology. In addition, the system can meet the end users’ demands for electricity, and heating and cooling powers through controlling the inlet pressure and temperature of an air based expander. A new parameter, the comprehensive efficiency, is proposed to evaluate the performance of the trigeneration system. Energy requirements of a small office building located in Chicago is used for the evaluation. The results show that the comprehensive efficiency of the system is very high (∼50%) in winter months when no cooling is needed. In summer months, due to the high power consumption in air compression process and inefficient expansion of the compressed air (for cooling power production) the comprehensive efficiency decreases to about 30%. However such a value is still higher than the conventional trigeneration system based on absorption chilling technology. The system is therefore very promising for practical applications particularly for the use of renewable energy due to good flexibility and simple configuration. [Copyright &y& Elsevier]

Abstract: In 2007 the Class 1 project commenced. Originally, 442 dwellings were to be designed and constructed as “low-energy class 1” houses according to requirements set by the Municipality of Egedal/Denmark. This means that the energy consumption is 50% below the existing energy regulations. Sixty five dwellings and about 30 single family houses have been constructed. The Concerto community also includes a kindergarten (completed) and an elderly centre. Currently, because of the financial crisis, only about 200 new dwellings will be constructed. Therefore, a contingency plan (plan B) has been developed replacing some of the new dwellings with renovation projects for public buildings. Simultaneously the originally planned district heating network supplied from a relatively small bio-gasification plant has been substantially enlarged to cover a large part of the existing Stenloese town as well and a large wood-chip heating plant has been added. The project demonstrates the benefits of ultra-low-energy buildings integrated with biomass- and solar heating energy supply. The Class 1 project involves four other countries: Estonia, France, Italy and Romania. These countries develop training activities based on the results and experiences gained from the Danish housing projects. This paper describes the comparisons between measured and calculated energy consumption in a social housing settlement and in a detached single-family house. Results show relatively large discrepancies between measured and calculated results, and discussions on possible explanations are given. [Copyright &y& Elsevier]

Abstract: When an air source heat pump (ASHP) operates in heating mode, frost can be accumulated on the surface of its finned outdoor coil. Frosting deteriorates the operation and energy efficiency of the ASHP and periodic defrosting becomes necessary. Currently the most widely used standard defrosting method for ASHPs is reverse cycle defrost. On the other hand, electronic expansion valves (EEVs) are commonly used in heat pump/refrigeration systems, including ASHP units, as throttle regulators of refrigerant flow. This paper reports on an experimental investigation of the performance of a reverse cycle defrost operation for a 6.5kW experimental heating capacity residential ASHP whose outdoor coil had four-parallel refrigerant circuits, and with an EEV as the refrigerant flow throttle regulator. The detailed descriptions of the experimental ASHP unit and the experimental procedures of ASHP are firstly presented. This is followed by reporting the comparative experiments of two control strategies for the EEV to investigate their effects on defrosting performance: the EEV being fully open and the EEV being regulated by a degree of refrigerant superheat (DS) controller. Experimental results revealed that when the EEV was regulated by the DS controller during defrosting, a higher defrosting efficiency and less heat wastage would be resulted in. [Copyright &y& Elsevier]