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The environmental profile of a dielectric-based 3D Building-Integrated Concentrating Photovoltaic(BICPV) device is investigated. Several scenarios and life-cycle impact assessment methods are adopted,including the newly-developed method ReCiPe. Multiple environmental indicators are evaluated fordifferent cities: Barcelona, Seville, Paris, Marseille, London and Aberdeen. The results from the mate-rial manufacturing phase demonstrate that the PV cells and the concentrator are the components withthe highest contribution to the total impact of the BICPV, based on ReCiPe, Eco-indicator 99, USEtox,CED (cumulative energy demand), GWP (global warming potential) according to different time hori-zons (20a, 100a, 500a) and Ecological footprint. Among the studied cities, Barcelona, Marseille andSeville present the lowest GWP and CED: less than 142 g CO2.eq/kWh and less than 2.9 MJprim/kWh,based on all the studied scenarios. Moreover, by considering 30-years lifespan, Barcelona, Marseille andSeville show 0.0107–0.0111 ReCiPe Pts/kWh while London, Paris and Aberdeen present 0.0161-0.0173ReCiPe Pts/kWh. Results about greenhouse-gas-, energy-, ReCiPe-payback times and energy-return-on-investment are also presented and critically discussed. In addition, comparisons with the literature andissues for the improvement of the environmental profile of the proposed system are included. The authors would like to thank “Ministerio de Economía y Competitividad” of Spain for the funding (grant reference ENE2013-48325-R).

Chemical looping syngas production is a two-step redox cycle with oxygen carriers (metal oxides) circulating between two interconnected reactors. In this paper, the performance of pure CeO2/Ce2O3 redox pair was investigated for low-temperature syngas production via methane reduction together with identification of optimal ideal operating conditions. Comprehensive thermodynamic analysis for methane reduction and water and CO2 splitting was performed through process simulation by Gibbs free energy minimization in ASPEN Plus®. The reduction reactor was studied by varying the CH4/CeO2 molar ratio between 0.4 and 4 along with the temperature from 500 to 1000 °C. In the oxidation reactor, steam and carbon dioxide mixture oxidized the reduced metal back to CeO2, while producing simultaneous streams of CO and H2 respectively. Within the oxidation reactor, the flow and composition of the mixture gas were varied, together with reactor temperature between 500 and 1000 °C. The results indicate that the maximum CH4 conversion in the reduction reactor is achieved between 900 and 950 °C with CH4/CeO2 ratio of 0.7–0.8, while, for the oxidation reactor, the optimal condition can vary between 600 and 900 °C based on the requirement of the final product output (H2/CO). The system efficiency was around 62% for isothermal operations at 900 °C and complete redox reaction of the metal oxide.

Many autonomous sensor nodes use small photovoltaic (PV) panels oriented towards the direction that provides the highest energy yield in the worst-case scenario. Since all those panels operate at similar irradiance and temperature conditions, they can be properly biased at the same bias point by using a single maximum power point tracker (MPPT). But in those applications involving several PV panels with dissimilar orientations, using an MPPT tailored to each panel would increase system cost. A better design option is to implement the MPPT with a single multiple-input converter (MIC) shared through time-division multiplexing (TDM) control. However, existing TDM controls are usually based on pulse width modulation (PWM) converters wherein the high switching frequency of transistors results in power losses that are excessive for low-power systems. Consequently, low-power MPPTs are usually based instead on pulse frequency modulation (PFM) converters. This paper proposes a novel TDM control method for MPPTs based on PFM converters. Peer Reviewed

Hybrid renewable energy systems (HRES) are a trendy alternative to enhance the renewable energy deployment worldwide. They effectively take advantage of scalability and flexibility of these energy sources, since combining two or more allows counteracting the weaknesses of a stochastic renewable energy source with the strengths of another or with the predictability of a non-renewable energy source. This work presents an optimization methodology for minimum life cycle cost of a HRES based on solar photovoltaic, wind and biomass power. Biomass power seeks to take advantage of locally available forest wood biomass in the form of wood chips to provide energy in periods when the PV and wind power generated are not enough to match the existing demand. The results show that a HRES combining the selected three sources of renewable energy could be installed in a rural township of about 1300 dwellings with an up-front investment of US $7.4 million, with a total life cycle cost of slightly more than US $30 million. Such a system would have benefits in terms of energy autonomy and environment quality improvement, as well as in term of job opportunity creation.

The main drawbacks faced by researchers to successfully implement organic-PCM as materials to improve the thermal performance of building systems are their low thermal conductivity, their high flammability, and their low thermal cycling stability. T In the present work, authors present a new enhanced PCM formulations aimed to solve the stated disadvantages in organic bulk-PCM. The new enhanced PCM were prepared by adding high thermal conductivity particles and two kinds of flame retardants into organic PCM (paraffin and fatty acid eutectic mixtures). In the first stage, the effective thermal conductivity of organic-PCM was increased by using two different methods: directly dispersion of powder graphite (PG) bulk-PCM and vacuum impregnation of PCM into expanded graphite (EG). In the second stage, the fire reaction behaviour of the thermal conductivity enhanced PCM formulations was improved by adding two kind of flame retardant: magnesium hydroxide and ammonium phosphate (APP).. Their fire reaction behaviour, thermal conductivity and thermophysical properties were measured by adapting the dripping test (UNE 23727-90), the hot-wire method and Differential Scanning Calorimetry (DSC), respectively. The enhanced PCM composites show a self-extinguished behaviour in terms of fire performance mechanism. The EG working with endothermic and phosphates flame retardants improve the fire performance of PCM by acting as a synergic system and the thermal conductivity is increased. However, their thermal storage capacity is significant decreased due to the large amount of flame retardant added (up to 40%). The thermal reliability was also tested, the enhanced PCM composites were stable up to 1000 thermal cycles.

Sorption heat storage has the potential to store large amounts of thermal energy from renewables and other distributed energy sources. This article provides an overview on the recent advancements on long-term sorption heat storage at material- and prototype- scales. The focus is on applications requiring heat within a temperature range of 30–150 °C such as space heating, domestic hot water production, and some industrial processes. At material level, emphasis is put on solid/gas reactions with water as sorbate. In particular, salt hydrates, adsorbents, and recent advancements on composite materials are reviewed. Most of the investigated salt hydrates comply with requirements such as safety and availability at low cost. However, hydrothermal stability issues such as deliquescence and decomposition at certain operating conditions make their utilization in a pure form challenging. Adsorbents are more hydrothermally stable but have lower energy densities and higher prices. Composite materials are investigated to reduce hydrothermal instabilities while achieving acceptable energy densities and material costs. At prototype-scale, the article provides an updated review on system prototypes based on the reviewed materials. Both open and closed system layouts are addressed, together with the main design issues such as heat and mass transfer in the reactors and materials corrosion resistance. Especially for open systems, the focus is on pure adsorbents rather than salt hydrates as active materials due to their better stability. However, high material costs and desorption temperatures, coupled with lower energy densities at typical system operating conditions, decrease their commercial attractiveness. Among the main conclusions, the implementation within the scientific community of common key performance indicators is suggested together with the inclusion of economic aspects already at material-scale investigations.