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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.

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.

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.

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.