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  • 1.
    Lindberg, Ulla
    RISE Research Institutes of Sweden, Built Environment, Energy and Resources.
    Research for the retail grocery context: A systematic review on display cabinets2020In: Trends in Food Science & Technology, ISSN 0924-2244, E-ISSN 1879-3053, Vol. 100, p. 19-34Article in journal (Refereed)
    Abstract [en]

    Background: Cabinet and in-store layout design impose high demands on supermarket refrigeration systems, due to temperature requirements and interactions between the ambient environment and the display. It is clear that views diverge on how different barriers should be investigated, and there are reasons to believe that energy efficiency measurements, with regards to both energy efficiency in buildings and energy efficiency in the operations, have weak points. The energy efficiency situation is a paradox that needs to be elaborated on. Scope and approach: The paper presents a systematic literature review of research on open (no doors) or closed refrigerated cabinets (with doors) energy efficiency, chilled groceries and the consumer behavior, followed by an analysis of the contemporary research. The paper draws on findings and collects peer-reviewed articles from databases in order to examine how research has reported on this issue. As a result, 31 articles were framed, with different variables, to form a body of this article. Key findings and conclusions: Empirical research is needed that uses actual data, such as perceptions, behavioral research with lab experiments, and field measurements. Consumers shopping situation, for chilled groceries, is an extensive and complex topic, and a single study cannot provide a complete overview of all its related aspects. The results focus on two objectives. Firstly to present the review and secondly to analyze and identify knowledge gaps within the energy efficiency and store installations in the grocery context.

  • 2.
    Nickel, David Benjamin
    et al.
    Chalmers University of Technology, Sweden.
    Fornell, Rickard
    RISE Research Institutes of Sweden, Built Environment, Energy and Resources.
    Janssen, Matty
    Chalmers University of Technology, Sweden.
    Franzén, Carl Johan
    Chalmers University of Technology, Sweden.
    Multi-Scale Variability Analysis of Wheat Straw-Based Ethanol Biorefineries Identifies Bioprocess Designs Robust Against Process Input Variations2020In: Frontiers in Energy Research, E-ISSN 2296-598X, Vol. 8, article id 55Article in journal (Refereed)
    Abstract [en]

    Bioprocesses based on (ligno-)cellulosic biomass are highly prone to batch-to-batch variations. Varying raw material compositions and enzyme activities hamper the prediction of process yields, economic feasibility and environmental impacts. Commonly, these performance indicators are averaged over several experiments to select suitable process designs. The variabilities in performance indicators resulting from variable process inputs are often neglected, causing a risk for faulty performance predictions and poor process design choices during scale-up. In this paper, a multi-scale variability analysis framework is presented that quantifies the effects of process input variations on performance indicators. Using the framework, a kinetic model describing simultaneous saccharification and ethanol fermentation was integrated with a flowsheet process model, techno-economic analysis and life cycle assessment in order to evaluate a wheat straw-based ethanol biorefinery. Hydrolytic activities reported in the literature for the enzyme cocktail Cellic® CTec2, ranging from 62 to 266 FPU·mL−1, were used as inputs to the multi-scale model to compare the variability in performance indicators under batch and multi-feed operation for simultaneous saccharification and fermentation. Bioprocess simulations were stopped at ethanol productivities ≤0.1 g·L−1·h−1. The resulting spreads in process times, hydrolysis yields, and fermentation yields were incorporated into flowsheet, techno-economic and life cycle scales. At median enzymatic activities the payback time was 7%, equal to 0.6 years, shorter under multi-feed conditions. All other performance indicators showed insignificant differences. However, batch operation is simpler to control and well-established in industry. Thus, an analysis at median conditions might favor batch conditions despite the disadvantage in payback time. Contrary to median conditions, analyzing the input variability favored multi-feed operation due to a lower variability in all performance indicators. Variabilities in performance indicators were at least 50% lower under multi-feed operation. Counteracting the variability in enzymatic activities by adjusting the amount of added enzyme instead resulted in higher uncertainties in environmental impacts. The results show that the robustness of performance indicators against input variations must be considered during process development. Based on the multi-scale variability analysis process designs can be selected which deliver more precise performance indicators at multiple system levels. 

  • 3.
    Ollas, Patrik
    RISE Research Institutes of Sweden, Built Environment, Energy and Resources. Chalmers University of Technology, Sweden.
    Energy Savings Using a Direct Current Distribution Network in a PV and Battery Equipped Residential Building2020Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Energy from solar photovoltaic (PV) are generated as direct current (DC) and almost all of today’s electrical loads in residential buildings, household appliances and HVAC system (Heating Ventilation and Air-conditioning) are operated on DC. For a conventional alternating current (AC) distribution system this requires the need for multiple conversion steps before the final user-stage. By switching the distribution system to DC, conversion steps between AC to DC can be avoided and, in that way, losses are reduced. Including a battery storage–the system’s losses can be reduced further and the generated PV energy is even better utilised.

    This thesis investigates and quantifies the energy savings when using a direct current distribution topology in a residential building together with distributed energy generation from solar photovoltaic and a battery storage. Measured load and PV generation data for a single-family house situated in Borås, Sweden is used as a case study for the analysis. Detailed and dynamic models–based on laboratory measurements of the power electronic converters and the battery–are also used to more accurately reflect the system’s dynamic performance.

    In this study a dynamic representation of the battery’s losses is presented which is based on laboratory measurements of the resistance and current dependency for a single lithium-ion cell based on Lithium iron phosphate (LFP). A comparative study is made with two others, commonly used, loss representations and evaluated with regards to the complete system’s performance, using the PV and load data from the single-family house. Results show that a detailed battery representation is important for a correct loss prediction when modelling the interaction between loads, PV and the battery.

    Four DC system topologies are also modelled and compared to an equivalent AC topology using the experimental findings from the power electronic converters and the battery measurements. Results from the quasi-dynamic modelling show that the annual energy savings potential from the suggested DC topologies ranges between 1.9–5.6%. The DC topologies also increase the PV utilisation by up to 10 percentage points, by reducing the associated losses from the inverter and the battery conversion. Results also show that the grid-tied converter is the main loss contributor and when a constant grid-tied efficiency is used, the energy savings are overestimated.

    Download full text (pdf)
    Licentiatavhandling__OLLAS
  • 4.
    Warneryd, Martin
    et al.
    RISE Research Institutes of Sweden, Built Environment, System setup and Service Innovation. Mälardalen University, Sweden; Dalarna University, Sweden.
    Håkansson, Maria
    RISE Research Institutes of Sweden, Built Environment, Energy and Resources.
    Karltorp, Kersti
    RISE Research Institutes of Sweden, Built Environment, System setup and Service Innovation. Jönköping International Business School, Sweden.
    Unpacking the complexity of community microgrids: A review of institutions’ roles for development of microgrids2020In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 121, article id 109690Article in journal (Refereed)
    Abstract [en]

    Community microgrids implemented in existing electricity grids can meet both development targets set out in the Paris agreement: 1. mitigate greenhouse gas emissions through increased implementation of renewable energy sources, and 2. to adapt to climate related disturbances and risk of catastrophes. Community microgrids are, however, complex to implement and institutional change is needed to reach their full potential. The purpose of this article is to review existing literature and analyze institutional developments influencing the growth of community microgrids. The literature describes a concentration of microgrid activities in specific regions: USA, EU, Asia and Australia. Varying reasons for implementing community microgrids were found in the different regions but similar institutional developments occurred, albeit with differing emphasis due to contextual specificities. Formal directions do however influence informal institutions even though their aims differ. Power utilities stand out as a critical actor and both formal and informal institutions put pressure on utilities to update their traditional business models. This article illustrates how informal and formal institutions play a significant role in the growth of community microgrids in existing electricity grids and provide interesting examples which can be utilized by policymakers. Microgrid development is still in a formative phase and further institutional change in the form of updated regulations is needed. © 2020 The Authors

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