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Huge amount of energy resources greenhouse gas (GHG) emissions is devoted to the built environment. Therefore, an accurate assessment method of these indicators is compulsory. To take advantage of the temporal variation in the primary energy use and associated GHG emissions of the energy supply, we propose two ways of integrating hourly life-cycle conversion factors in building energy systems. First, to appraise the energy system design, we developed a versatile modelling and performance assessment framework using a multi-criteria approach. The simulated performances of possible energy systems are compared, and help designers systematically choose appropriate energy production and storage systems. Second, for the operation of the building, we propose an energy management procedure (EMP) that always feeds in the energy source with the least global warming potential (GWP). These two developments are tested on a case study consisting in an architectural project that should respect the 2000 W society targets. The running conditions of several energy systems are simulated and compared. The most promising scenario is identified. Compared to traditional methods, the assessment framework has a promising future but the GWP-based energy management procedure offers, in the context of the case study, limited GHG emissions mitigation at very high primary energy cost.

It is a frequent practice nowadays to use mean annual conversion factors (CFs) when performing life-cycle assessment (LCA) of processes and products that use electricity supplied by the grid. In this paper, we conduct an hourly assessment of the greenhouse gas (GHG) emission factor, along with the conversion factors for the cumulative energy demand (CED) and its non-renewable part (CEDnr), of electricity supplied by the Swiss grid and its direct neighboring countries (France, Germany, and Austria; Italy being neglected). Based on an hourly inventory of energy flows during a one-year period (2015–2016), this attributional approach allows performance of various certification procedures of process or product manufacturing, and comparison of energy and carbon intensities of different national mixes. Hourly calculation allows evaluation of the order of magnitude of errors made when considering an annual mix. Visualization techniques are used to better understand the obtained data and to detect when strategies involving timing optimization of electricity use may be efficient. A case study is chosen to illustrate the relevance of hourly CFs when performing LCA associated to the exploitation of a given building. Moreover, mean annual CFs of interest are discriminated by electricity end-use sectors. This could be of great help for system designers willing to improve the assessment accuracy when hourly CFs are not readily available.

The data presented in this article are related to the research article entitled “Temporal variations in the primary energy use and greenhouse gas emissions of the electricity provided to the Swiss grid” Vuarnoz and Jusselme (2018). The provided data are the hourly CO2-eq emission factors, and the hourly conversion factors for the cumulative energy demand and its non-renewable part for the Swiss electricity mix over one year. These data have been assessed on the basis of an inventory of the technology used for electricity generation and an attributional life-cycle approach. The presented data are necessary for life-cycle assessment of all processes and products using electricity in Switzerland. They serve also as a sustainable benchmark when implementing renewable energy systems and energy storage.

This paper discusses the system performance of a magnetic heat pump with an active magnetic regenerator. The heat-transfer coefficient and pressure drop in the AMR are performed analytically. Measurements on the experimental magnetic heat pump test device are performed using distilled water as the working fluid. The coupling of a one-dimensional thermal model is presented. The thermal model takes into consideration the magneto-caloric effect as a source term and the energy conservation between a solid and a fluid. At cyclic steady states, the temperatures of the fluid on both sides of the regenerator are calculated numerically and compared with the measurement results. A reasonable agreement between simulations and experiments confirms the validity of the proposed model.

Today, cooling systems are widely used, notably with the unprecedented growth of data centres and building space cooling. These thermodynamic systems are powered mainly with electricity, and their peak loads are generally associated with very high carbon footprints. At the same time, congestion of the grid due to high load or renewable power injection is becoming an issue for all actors involved with electricity (producers, providers, consumers, and prosumers). Actually, both the price and associated carbon footprint of electricity usually fluctuates along with the charge of the network. This paper discusses the integration of power flexibility (PF) in new and existing cooling systems to avoid a possible cold crunch in the near future. After defining PF, several cooling systems archetypes are presented. Three possible ways to integrate PF are explained: flexibility by thermal inertia and energy storage (thermal and electrochemical). While PF principally targets the reduction of stress on the electric grid, other benefits can also be achieved, e.g. mitigation of direct carbon emissions and decrease of costs related to operating the refrigeration system. We explain how better management of energy transits and possible imbalance in electricity networks can be achieved by thermal inertia. The choice of integrating thermal storage or electric battery is discussed, and both solutions are considered in a specific case study. The study aims at better management of power loads on electricity network caused by the cooling system and could be useful for anyone involved with grid management and/or refrigeration systems.

The main objective of this theoretical study was to investigate under which conditions a magnetic energy conversion device (MECD) - utilizing industrial waste heat - is economically feasible. Furthermore, it was evaluated if magnetic energy conversion (MCE) has the potential of being a serious concurrent to already existing conventional energy conversion technologies. Up-today the availability of magnetocaloric materials with a high Curie temperature and a high magnetocaloric effect is rather limited. Therefore, this study was mainly focused on applications with heat sources of low to medium temperature levels. Magnetic energy conversion machines, containing permanent magnets, are numerically investigated for operation conditions with different temperature levels, defined by industrial waste heat sources and environmental heat sinks, different magnetic field intensities and different frequencies of operation (number of thermodynamic cycles per unit of time). Theoretical modeling and numerical simulations were performed in order to determine thermodynamic efficiencies and the exergy efficiencies as function of different operation conditions. From extracted data of our numerical results, approximate values of the total mass and total volume of magnetic energy conversion machines could be determined. These important results are presented dependent on the produced electric power. An economic feasibility study supplements the scientific study. It shows an excellent potential of profitability for certain machines. The most important result of this article is that the magnetic energy conversion technology can be economically and technically competitive to or even beat conventional energy conversion technologies. This is true especially in those cases when large, low-exergy heat sources are at one's disposal. (C) 2012 Elsevier Ltd. All rights reserved.

A PCM dephaser and storage module based on a melting/freezing model was built and implemented into the Dymola-Modelica software. This software offers thermal libraries with standard components as tubes, pumps, heat exchangers, etc. Main simulation results of interest include the phase shift (delay time) caused by cylinders filled with a PCM and positioned in the storage/dephasing device. Furthermore, an entire Minergie™ house was modelled by a rather simple (economic in terms of CPU time), but still very effective thermal model. This house is connected to a suitable ventilation system chosen from a list of six different types. Therefore, also by graphical means on an interface, it is possible to create a Minergie™ house with an integrated thermal temperature lowering/phase shifting and heat recovery device. Temperature differences between a Minergie™ house connected to a storage device and a house without such a device are studied. Such systems are planned to be mainly used for hybrid cooling of Swiss Minergie™ houses in summer time. In a multi-functional application, they could also be applied in winter for a heating support. Numerous simulation results are discussed and optimal solutions are presented.

Standard algorithm of building’s energy strategy often use electricity and its tariff as the sole criterion of choice. This paper introduced an algorithmic regulation using global warming potential (GWP) of energy flux, to select which installation will satisfy the building energy demand (BED). In the frame of the Correlation Carbon project conducted by the Smart Living Lab (SLL), a research center dedicated to the building of the future, this paper presents the algorithm behind the design, the selection and the operation of appropriate energy installations for low-carbon buildings. The control strategy governing the building’s energy flow takes into account demand, supply and storage. The latter being mainly linked to economic or energy benefits, which standard algorithms often use as the only criterion of choice, thus increasing the environmental impact of the energy flowing through the building. In contrast to those, the algorithm introduced in this paper controls the energy fluxes of the electrical grid, photovoltaic (PV) panels, static and vehicle batteries according to their GWP. A simulation over one year at an hourly time step – enabling one to take into account small but significant variations of the GWP of the electricity from grid – is presented for different scenarios, in order to draw an annual balance for a given combination of energy systems. The algorithm chooses the “cleanest” instantaneous energy source combination to meet the BED. Simulations show that a building using this algorithm can satisfy its BED while reducing its GWP by as much as 40% compared to an energy supply using the grid only.

At present magnetic refrigeration shows a realistic potential to penetrate into some niche markets in the field of cold and hot "production". It is well known that a refrigerator for cooling and a heat pump for heating are machines based on the same principle. A small review on magnetic heat pump studies is outlined and a simple engineering calculation scheme to determine the coefficient of performance for a magnetic heat pump with a rotary porous structure heat exchanger is presented. Magnetic heat flux line distributions are calculated by a 2-d finite element method numerical simulation program with the objective to obtain high field's mu H-0 with not too heavy permanent magnets assemblies. The porous structures are geometrically optimised to obtain maximal magnetic field inductions. It is shown that for a water/ethylene-glycol magnetic heat pump the coefficient of performance is higher than that of a conventional heat pump. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic refrigeration is a new environmentally benign technology and a promising alternative to conventional vapor-cycle refrigeration. The household refrigerator without a freezing compartment shows very good prospects for a successful application. This article starts with the general principle of magnetic refrigeration. An example of a magnet assembly is proposed and the corresponding magnetic flux lines are evaluated with a three-dimensional finite-element method (FEM). The maximum specific cooling capacity of magneto caloric materials is described. The specific cooling power of a magneto caloric material is found to be large even for medium magnetic field changes, especially if the frequency is not too small. For a domestic magnetic refrigerator, a comparison with a standard compressor refrigerator is presented. The modeling of a rotary magnetic refrigerator is described and its dynamic behavior is investigated. The physical model is based on a mapping of the magneto-thermodynamic problem from a cylinder onto two rectangles. In this model, in a basic centre cell, two coupled linear partial differential equations are solved, which have been programmed in the Modelica language. Steady-state solutions are envisaged to determine the coefficient of performance, COP, for these conditions. In future work the developed model shall be applied for an optimization of the magnetic refrigerator and to determine the related best parameters.

Recognized as a powerful methodology for the evaluation of environmental burdens, life cycle assessment (LCA) must be performed with close-to-reality inputs to be robust and accurate. However, the necessary real-world data is hardly available at the design stage, resulting in current LCA practice being mainly based on standards and norms as hypothesis of building contexts, therefore inducing uncertainties in results. The current paper presents a methodology to collect a subset of such input data in a function of the context more accurately than the standards. It then studies the impact of such uncertainties in the LCA results. Through an academic building case study that measured data concerning the building occupancy (A), i.e. the hourly occupancy rate and density, the hourly appliance consumption rate (B), and the hourly conversion factors of environmental impact of the electricity mix (C), the LCA results for the GHG emissions and primary energy consumption are compared between normative- and measurements-based input parameters. The measured occupancy rate (A) is shown to impact the LCA results the most, especially the embedded impacts, by implying a new occupancy density: the building population increase of +32% leads to a significant increase of the embedded impacts related to furniture. The variability in appliance usage (B) is marginal between measures and standards and therefore does not lead to a significant change in LCA results. The use of hourly conversion factors (C) indicates an underestimation of the GHG emissions and, at the same time, an overestimation of the primary energy when assessed with mean annual values. The combined effect of simultaneously using the three reality-based input parameters (A, B, C) mostly affects the non-renewable part of the cumulative energy demand indicator (-9% reduction of the operational part), followed by the cumulative energy demand (-7%) and GHG emissions indicators (-3%). The research findings affect not only LCA research but also practitioners such as architects or building contractors who need to respect ambitious environmental targets.

In this study, a flat-parallel-plate active magnetic regenerator made of gadolinium is investigated. The coupling of a one-dimensional thermal model with a two-dimensional magnetic model is presented. The thermal model takes into consideration the magnetocaloric effect as a source term and the energy conservation between a solid and a fluid. The magnetic model considers the space distribution of the internal magnetic field strength, and thus it includes the demagnetization effect. Measurements on an experimental magnetic refrigeration test device are performed using distilled water as the working fluid. At cyclic steady states, the temperatures of the fluid on both sides of the regenerator are calculated numerically and compared with the measurement results. The inability to provide a constant internal magnetic field during the heat transfer process with a permanent magnet is demonstrated. A reasonable agreement between simulations and experiments confirms the validity of the proposed model. (C) 2013 Elsevier Ltd. All rights reserved.

In conventional refrigeration the use of the T S diagram to determine thermodynamic cycle performance is a well accepted tool. This method is based on a single state description of the gaseous refrigerant during its cycling. Devices filled with a magnetocaloric refrigerant, due to slow diffusion and inhomogeneous temperature distributions, usually do not allow such a simple description. If the layered bed technique is applied, the situation is even more complex. The related problems are addressed and some new solutions are presented, e.g. a generalized T*-S* diagram containing weights w*. Furthermore, an analysis shows that an implementation of a layered bed of numerous weak magnetocaloric alloys does not substantially decrease the coefficient of performance, COP, compared to a single correspondingly better performing magnetocaloric material, but leads to an increase of the magnet size, the volume and the related price of a device. With devices operating with higher frequencies this can be counterbalanced and magnetic heating, refrigeration and energy conversion - with present available magnetocaloric materials - suddenly show a realistic chance for certain market penetrations. (c) 2012 Elsevier Ltd and IIR. All rights reserved.

A first part of the article contains a thermodynamic theory describing the temperature distribution in a Curie wheel. The occurring nonlinear ordinary differential equation has an analytical solution. If a Curie wheel is stabilized by levitation, it is named Palmy wheel. These wheels show a full structure, and because of this reason, their uptake of heat from a flame (Curie wheel) or by (solar) light absorption (Palmy wheel) only on the periphery of a cylinder is very limited. To improve the method, a modification of the principle by introducing a convective heat transport into a porous wheel is discussed. By this the power conversion rate from a heat flux to mechanical and electric power is very much increased. The second part of the article presents results of a theoretical/numerical study on the efficiencies of magnetic power conversion plants operating with porous wheels. Furthermore, these efficiencies which are promising-are compared with those of existing power conversion plants, as e.g. geothermal binary cycle power plants. (C) 2008 Published by Elsevier B.V.

In a rotary magnetic refrigerator a porous ring is turning in and out of a magnetic field region. The adiabatic demagnetization of the magnetocaloric material produces the "cold energy". This is described by a discontinuous temperature decrease, known as adiabatic temperature difference. For such a machine a physical model has been developed, based on a mapping of the magneto-thermodynamic problem. In this model, in a basic centre cell, two coupled linear partial differential equations are solved, which have been programmed in the Modelica language. The operation of a magnetic refrigerator is simulated with numerous parameters. Steady state solutions are obtained to verify the coefficient of performance under stable operation conditions. Optimal running conditions defined by maximum values of the coefficient of performance - are not presented in this article, but can now easily be obtained with the existing program. A simple regulation strategy is proposed and implemented into the program. (C) 2010 Elsevier Ltd and IIR. All rights reserved.

The storage of 'cold' with ice slurries-a special type of thermally multi-functional fluids or phase change slurries (PCS)-is discussed. At first an example of a calculation of a thermal energy storage tank in an ice slurry system with a peak load demand is presented. Then a new concept of ice slurry storage without mixing is introduced. It leads to ice particle stratification and front propagation in the storage vessel. The stratification of ice particles in ice slurry is theoretically described by multi-component multi-phase fluid dynamics. The resulting stratification process is calculated and front propagation times are compared with experimental results; they compare fairly well. Copyright (C) 2007 John Wiley & Sons, Ltd.

In high-performance buildings, energy storage is a key component in increasing self-consumption of onsite renewable energy, but is also responsible for extra embedded burdens. The main risk is not paying back these extra burdens through operational benefits during the use phase of the building. The aim of this study is to define, explore and propose a methodology for assessing the limits of the viability of energy storage systems when embedded in a building, utilising a set of indicators including greenhouse gas emissions, primary energy and costs. These values are therefore of importance when designing a building energy system integrating renewable energy source and energy storage. Beyond the results obtained for a case study in Switzerland, the study unveils different mechanisms according to the scheme of renewable energy exports. Results are greatly affected by the geographic context and demonstrate the necessity to implement harvesting systems providing low-impact renewable energy in buildings.

An investigation under which conditions industrial waste heat utilised with magnetic energy conversion machines can be a possible alternative to conventional energy conversion technologies is presented. The application of a numerical model leads to the thermodynamic efficiency, the exergy efficiency, and approximate values of the total mass and the total volume of a magnetic energy conversion machine. The exergy efficiency depends strongly on the magnetic field strength. A high frequency of operation reduces the mass and volume of a device. Magnetic energy conversion may beat conventional technologies, especially if large low-exergy heat sources are at ones disposal.

A magnetic hyperthermia cancer treatment strategy that does not operate by means of conventional heating mechanisms is presented. The proposed approach consists of injecting a gel with homogeneously distributed magnetic nanowires into a tumor. Upon the application of a low-frequency rotating or circularly polarized magnetic field, nanowires spin around their center of viscous drag due to torque generated by shape anisotropy. As a result of external rotational forcing and fluid friction in the nanoparticle's boundary layer, heating occurs. The nanowire dynamics is theoretically and experimentally investigated, and different feasibility proofs of the principle by physical modeling, which adhere to medical guidelines, are presented. The magnetic nanorotors exhibit rotations and oscillations with quite a steady center of gravity, which proves an immobile behavior and guarantees a time-independent homogeneity of the spatial particle distribution in the tumor. Furthermore, a fluid dynamic and thermodynamic heating model is briefly introduced. This model is a generalization of Penne's model that for this method reveals theoretic heating rates that are sufficiently high, and fits well into medical limits defined by present standards.